ChangeDyn

; Copyright 1996 Acorn Computers Ltd
;
; Licensed under the Apache License, Version 2.0 (the "License");
; you may not use this file except in compliance with the License.
; You may obtain a copy of the License at
;
;     http://www.apache.org/licenses/LICENSE-2.0
;
; Unless required by applicable law or agreed to in writing, software
; distributed under the License is distributed on an "AS IS" BASIS,
; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
; See the License for the specific language governing permissions and
; limitations under the License.
;
        TTL   => ChangeDyn

        ; OS_ChangeDynamicArea optimisations:

        GBLL  FastCDA_UpFront ; Do all cache/TLB maintenance upfront instead of on a per-page basis
FastCDA_UpFront SETL {TRUE}

        GBLL  FastCDA_FIQs ; Don't thrash ClaimFIQ/ReleaseFIQ in DoTheGrowPagesSpecified
FastCDA_FIQs SETL {TRUE}

        GBLL  FastCDA_NoPhysical ; Don't use RISCOS_AccessPhysicalAddress/RISCOS_ReleasePhysicalAddress in DoTheGrowPagesSpecified. Instead, map pages straight to destination address.
FastCDA_NoPhysical SETL {TRUE}

        GBLL  FastCDA_CorruptFreePool ; Contents of free pool doesn't need preserving in DoTheGrowPagesSpecified
FastCDA_CorruptFreePool SETL {TRUE}

        GBLL  FastCDA_Unnecessary ; Avoid unnecessary MMU_ChangingEntry calls in DoTheGrowPagesSpecified
FastCDA_Unnecessary SETL {TRUE}

        ; DoTheGrowPagesSpecified profiling code
        ; Written to use Cortex-A8 cycle count performance counter - will need modifying for other CPUs!

        GBLL  FastCDA_Prof
FastCDA_Prof SETL {FALSE}

      [ FastCDA_Prof
        ; Squeeze profiling workspace into "free space after envstring"
                                 ^ ExtendedROMFooter+4
        ! 0, "FastCDA_Prof workspace at ":CC::STR:@
FastCDA_Prof_DoTheGrowInit           # 4
FastCDA_Prof_MarkRequired            # 4
FastCDA_Prof_PagesUnsafe             # 4
FastCDA_Prof_DoublyCheckCacheability # 4
FastCDA_Prof_DoublyMovePages         # 4
FastCDA_Prof_FindSpare               # 4
FastCDA_Prof_ClaimFIQ                # 4
FastCDA_Prof_AccessPhysical          # 4
FastCDA_Prof_CopyPage                # 4
FastCDA_Prof_ReleasePhysical         # 4
FastCDA_Prof_MoveReplacement         # 4
FastCDA_Prof_MoveNeeded              # 4
FastCDA_Prof_ReleaseFIQ              # 4
FastCDA_Prof_PagesSafe               # 4
FastCDA_Prof_CallPreGrow             # 4
FastCDA_Prof_CallPostGrow            # 4
FastCDA_Prof_MMUChanging             # 4
FastCDA_Prof_MMUChangingUncached     # 4
FastCDA_Prof_ChangingEntry           # 4
        ASSERT @ <= &500
      ]

        MACRO
        FastCDA_ProfInit $temp
      [ FastCDA_Prof
        MVN     $temp,#0
        MCR     p15,0,$temp,c9,c12,2
        MOV     $temp,#1<<31
        MCR     p15,0,$temp,c9,c12,1
        MOV     $temp,#7
        MCR     p15,0,$temp,c9,c12,0
      ]
        MEND

        MACRO
        FastCDA_ProfStart $var,$temp,$temp2,$temp3,$cc
      [ FastCDA_Prof
        LDR$cc  $temp,=ZeroPage+FastCDA_Prof_$var
        LDR$cc  $temp2,[$temp]
        MRC$cc  p15,0,$temp3,c9,c13,0
        SUB$cc  $temp2,$temp2,$temp3
        STR$cc  $temp2,[$temp]
      ]
        MEND

        MACRO
        FastCDA_ProfEnd $var,$temp,$temp2,$temp3,$cc
      [ FastCDA_Prof
        MRC$cc  p15,0,$temp3,c9,c13,0
        LDR$cc  $temp,=ZeroPage+FastCDA_Prof_$var
        LDR$cc  $temp2,[$temp]
        ADD$cc  $temp2,$temp2,$temp3
        STR$cc  $temp2,[$temp]
      ]
        MEND

;******************************************************************************
; ChangeDynamic SWI
; In  : R0 =  0 => System Heap,
;             1 => RMA
;             2 => Screen
;             3 => Sprite area
;             4 => Font cache
;             5 => RAM disc
;             6 => Free pool
;       R1 = no of bytes to change by
;
; Out : V set if CAO in AplWork or couldn't move all the bytes requested.
;       R1 set to bytes moved.
;******************************************************************************

AP_AppSpace     *       0                                       ; user r/w, CB
AP_SysHeap      *       0                                       ; user r/w, CB
AP_RMA          *       0                                       ; user r/w, CB
AP_Screen       *       0 :OR: DynAreaFlags_NotCacheable :OR: DynAreaFlags_DoublyMapped :OR: DynAreaFlags_NeedsSpecificPages
AP_Sprites      *       0                                       ; user r/w, CB
AP_FontArea     *       2                                       ; user none, CB
AP_RAMDisc      *       2 :OR: DynAreaFlags_NotCacheable        ; user none, ~CB (poor performance for current StrongARMs)
AP_RAMDisc_SA   *       2                                       ; user none,
AP_Duff         *       2 :OR: DynAreaFlags_NotCacheable :OR: DynAreaFlags_NotBufferable ; user none, ~C~B
AP_FreePool     *       2 :OR: DynAreaFlags_NotCacheable        ; user none, ~CB
AP_CursorChunk  *       1 :OR: DynAreaFlags_NotCacheable :OR: DynAreaFlags_NotBufferable :OR: PageFlags_Unavailable

AP_L2PT         *       2 :OR: DynAreaFlags_NotCacheable :OR: DynAreaFlags_NotBufferable ; user none, ~C~B
AP_L1PT         *       AP_L2PT :OR: PageFlags_Unavailable
AP_UndStackSoftCam *    PageFlags_Unavailable

  [ DA_Batman
ChangeDyn_Batcall    * -3               ; special DA number to select Batman usage of OS_ChangeDynamicArea
  ]
ChangeDyn_FreeAndApl * -2               ; special reason code for when we're sucking out of free pool and apl space
ChangeDyn_AplSpace   * -1
ChangeDyn_SysHeap    * 0
ChangeDyn_RMA        * 1
ChangeDyn_Screen     * 2
ChangeDyn_SpriteArea * 3
ChangeDyn_FontArea   * 4
ChangeDyn_RamFS      * 5
ChangeDyn_FreePool   * 6
ChangeDyn_MaxArea    * 6

; Area handler reason codes

DAHandler_PreGrow       *       0
DAHandler_PostGrow      *       1
DAHandler_PreShrink     *       2
DAHandler_PostShrink    *       3
 [ ShrinkableDAs
DAHandler_TestShrink    *       4       ; new reason added to find amount area could shrink by
 ]

; Number of entries in page block on stack

NumPageBlockEntries *   63
PageBlockSize   *       NumPageBlockEntries * 12
PageBlockChunk  *       NumPageBlockEntries * 4096

;
; mjs - performance enhancements (from Ursula, merged into HALised kernel June 2001)
; Workspace for acceleration of operations on a DA, by reducing need to traverse DA list.
;
; - accelerates allocating non-quick DA numbers to O(n) instead of laughable O(n*n), where n is no. of DAs
; - accelerates enumeration to O(n) instead of laughable O(n*n)
; - allocation of a quick handle (DA number) is O(1)
; - access of a DA node from a quick handle is O(1)
; - access of a DA node from a non-quick handle is O(1), if it repeats the most recent non-quick handle access (else O(n))
;
; - creation of a DA still has some O(n) work (requires search for address space), but is now rather quicker
; - removal of a DA is still O(n) (requires traversal of list in order to get previous node)
; - other uses of a DA with a quick handle (eg. get info, change size) avoid any O(n) work
;
; - all system handles will be quick.
; - non-system handles will be quick, except for very large numbers of DAs, or silly modules like the Wimp who insist on
;   their own silly DA number (the latter can still benefit from LastTreacleHandle - see below)
;
; Limitations:
; - does not allow anyone to choose their own DA number that clashes with the quick handle set - should not
;   be a problem since choosing own number reserved for Acorn use
; - does not allow anyone to renumber a DA with a quick handle - again, reserved for system use
; - DA names will be truncated to a maximum of 31 characters (or as defined below)
;
                                  GBLL DynArea_QuickHandles
DynArea_QuickHandles              SETL {TRUE}
;
      ;various bad things happen if DynArea_QuickHandles is FALSE (eg. some new API disappears)
      ;should remove FALSE build option to simplify source code next time kernel is updated (kept for reference/testing now)
      ASSERT DynArea_QuickHandles

                                  GBLL DynArea_NullNamePtrMeansHexString
DynArea_NullNamePtrMeansHexString SETL {TRUE} :LAND: DynArea_QuickHandles
;
  [ DynArea_QuickHandles
DynArea_MaxNameLength     * 31                      ;maximum length of DA name, excluding terminator (multiple of 4, -1)
DynArea_NumQHandles       * 256                     ;maximum no. of non-system quick handles available simultaneously
DynArea_AddrLookupBits    * 8                       ;LUT covers entire 4G logical space, so 4G>>8 = 16M granularity
DynArea_AddrLookupSize    * 1<<(32-DynArea_AddrLookupBits) ; Address space covered by each entry
DynArea_AddrLookupMask    * &FFFFFFFF-(DynArea_AddrLookupSize-1)
;
                          ^  0,R11
DynArea_TreacleGuess      # 4                       ;guess for next non-quick handle to allocate, if needed, is TreacleGuess+1
DynArea_CreatingHandle    # 4                       ;handle proposed but not yet committed, during DynArea_Create, or -1 if none
DynArea_CreatingPtr       # 4                       ;ptr to proposed DANode during DynArea_Create (invalid if CreatingHandle = -1)
DynArea_LastTreacleHandle # 4                       ;last non-quick handle accessed by a client (usually the Wimp), or -1 if none
DynArea_LastTreaclePtr    # 4                       ;ptr to DANode for last non-quick handle accessed (invalid if LastTreacleHandle = -1)
DynArea_LastEnumHandle    # 4                       ;last handle enumerated, or -1 if none
DynArea_LastEnumPtr       # 4                       ;ptr to DANode for last handle enumerated (invalid if LastEnumHandle = -1)
DynArea_ShrinkableSubList # 4                       ;sub list of dynamic areas that are Shrinkable (0 if none)
DynArea_OD6Signature      # 4                       ;signature of changes to non-system DAs since last call to OS_DynamicArea 6
                                                    ;bit  0 = 1 if any DAs have been created
                                                    ;bit  1 = 1 if any DAs have been removed
                                                    ;bit  2 = 1 if any DAs have been resized (excluding grow or shrink at creation or removal)
                                                    ;bit  3 = 1 if any DAs have been renumbered
                                                    ;bits 4-30   reserved (0)
                                                    ;bit 31 = 1 if next resize is not to update signature (used during create, remove)
DynArea_OD6PrevSignature  # 4                       ;previous signature, used to distinguish single from multiple changes
DynArea_OD6Handle         # 4                       ;handle of last DA that affected signature
DynArea_OD8Clamp1         # 4                       ;clamp value on area max size for OS_DynamicArea 0 with R5 = -1
                                                    ;(default -1, set by R1 of OS_DynamicArea 8)
DynArea_OD8Clamp2         # 4                       ;clamp value on area max size for OS_DynamicArea 0 with R5 > 0 (not Sparse)
                                                    ;(default -1, set by R2 of OS_DynamicArea 8)
DynArea_OD8Clamp3         # 4                       ;clamp value on area max size for OS_DynamicArea 0 for a Sparse area
                                                    ;(default 4G-4k, set by R3 of OS_DynamicArea 8)
DynArea_SortedList        # 4                       ;alphabetically sorted list of non-system areas, or 0 if none
DynArea_SysQHandleArray   # 4*(ChangeDyn_MaxArea+1) ;for system areas 0..MaxArea, word = ptr to DANode, or 0 if not created yet
DynArea_FreeQHandles      # 4                       ;index of first free quick handle, starting at 1 (or 0 for none)
DynArea_QHandleArray      # 4*DynArea_NumQHandles   ;1 word per quick handle
                                                    ; - if free, word = index of next free quick handle (or 0 if none)
                                                    ; - if used, word = ptr to DANode (must be > DynArea_NumQHandles)
DynArea_AddrLookup        # 4<<DynArea_AddrLookupBits ; Lookup table for fast logaddr -> dynarea lookup
;
DynArea_ws_size           *  :INDEX:@               ;must be multiple of 4
;
            ASSERT DynArea_QHandleArray = DynArea_FreeQHandles +4
  ]
;


;        InsertDebugRoutines

; Exit from ChangeDynamicArea with error Not all moved

failure_IRQgoingClearSemaphore
        LDR     r0, =ZeroPage
      [ ZeroPage = 0
        STR     r0, [r0, #CDASemaphore]
      |
        MOV     r10, #0
        STR     r10, [r0, #CDASemaphore]
      ]
failure_IRQgoing
        ADR     r0, ErrorBlock_ChDynamNotAllMoved
ChangeDynamic_Error
        MOV     r10, #0
        STR     r0, [stack]
        LDR     lr, [stack, #4*10]
        ORR     lr, lr, #V_bit
        STR     lr, [stack, #4*10]
CDS_PostServiceWithRestore
      [ International
        LDR     r0, [stack]
        BL      TranslateError
        STR     r0, [stack]
      ]

; and drop thru to ...

CDS_PostService
        MOV     r1, #Service_MemoryMoved
        MOV     r0, r10                 ; amount moved
        MOVS    r2, r11                 ; which way was transfer?
        BMI     %FT47                   ; [definitely a grow]
        CMP     r11, #ChangeDyn_FreePool
        BNE     %FT48                   ; [definitely a shrink]
        CMP     r12, #ChangeDyn_AplSpace
        BEQ     %FT48                   ; [a shrink]
47
        RSB     r0, r0, #0             ; APLwork or free was source
        MOV     r2, r12                ; r2 = area indicator
48
        BL      Issue_Service

        MOV     r1, r10                ; amount moved

        Pull    "r0, r2-r9, r10, lr"
        ExitSWIHandler

        MakeErrorBlock ChDynamNotAllMoved


; in:   r0 = logical address where page is now

GetPageFlagsForR0IntoR6 Entry "R0-R2, R4-R5, R7"
;
; code from MoveCAMatR0toR3
;
        LDR     r5, =L2PT
        ADD     r4, r5, r0, LSR #10             ; r4 -> L2PT for log addr r0
        MOV     r2, r4, LSR #12
        LDR     r2, [r5, r2, LSL #2]            ; r2 = L2PT entry for r4
        TST     r2, #3                          ; if no page there
        BEQ     %FT90                           ; then cam corrupt

        LDR     r4, [r4]                        ; r4 = L2PT entry for r0
        TST     r4, #3                          ; check entry is valid too
        BEQ     %FT91
        MOV     r4, r4, LSR #12                 ; r4 = phys addr >> 12

        LDR     r2, =ZeroPage
        LDR     r6, [r2, #MaxCamEntry]
        ADD     r5, r2, #PhysRamTable
      [ ZeroPage <> 0
        MOV     r2, #0
      ]
10
        CMP     r2, r6                          ; if page we've got to is > max
        BHI     %FT92                           ; then corrupt
        LDMIA   r5!, {r7, lr}                   ; get phys.addr, size
        SUB     r7, r4, r7, LSR #12             ; number of pages into this bank
        CMP     r7, lr, LSR #12                 ; if too many
        ADDCS   r2, r2, lr, LSR #12             ; then advance physical page no.
        BCS     %BT10                           ; and loop

        ADD     r2, r2, r7                      ; add on number of pages within bank
;
; code from BangCamUpdate
;
        LDR     r1, =ZeroPage
        LDR     r1, [r1, #CamEntriesPointer]
        ADD     r1, r1, r2, LSL #3              ; point at cam entry (logaddr, PPL)
        LDMIA   r1, {r0, r6}                    ; r0 = current logaddress, r6 = current PPL
        EXIT

90
        ADR     lr, NoL2ForPageBeingRemovedError ; NB don't corrupt r0 yet - we need that in block as evidence
95
        STR     lr, [sp]                        ; update returned r0
        BL      StoreDebugRegs
        PullEnv                                 ; seriously broken memory
        SETV
        MOV     pc, lr

91
        ADR     lr, PageBeingRemovedNotPresentError
        B       %BT95

92
        ADR     lr, PhysicalAddressNotFoundError
        B       %BT95


; MoveCAMatR0toR3
; in:   r0 = old logaddr
;       r3 = new logaddr
;       r9 = offset from 1st to 2nd copy of doubly mapped area (either source or dest, but not both)
;       r11 = page protection level
;
; out:  r2 = physical page number of page moved, unless there was a serious error
;       r0,r1,r3,r6-r12 preserved
;       r4,r5 corrupted

MoveCAMatR0toR3 Entry "r0,r1,r6,r7"
        LDR     r5, =L2PT
        ADD     r4, r5, r0, LSR #10             ; r4 -> L2PT for log addr r0
        MOV     r2, r4, LSR #12
        LDR     r2, [r5, r2, LSL #2]            ; r2 = L2PT entry for r4
        TST     r2, #3                          ; if no page there
        BEQ     %FT90                           ; then cam corrupt

        LDR     r4, [r4]                        ; r4 = L2PT entry for r0
        TST     r4, #3                          ; check entry is valid too
        BEQ     %FT91
        MOV     r4, r4, LSR #12                 ; r4 = phys addr >> 12

        LDR     r2, =ZeroPage
        LDR     r6, [r2, #MaxCamEntry]
        ADD     r5, r2, #PhysRamTable
      [ ZeroPage <> 0
        MOV     r2, #0
      ]
10
        CMP     r2, r6                          ; if page we've got to is > max
        BHI     %FT92                           ; then corrupt
        LDMIA   r5!, {r7, lr}                   ; get phys.addr, size
        SUB     r7, r4, r7, LSR #12             ; number of pages into this bank
        CMP     r7, lr, LSR #12                 ; if too many
        ADDCS   r2, r2, lr, LSR #12             ; then advance physical page no.
        BCS     %BT10                           ; and loop

        ADD     r2, r2, r7                      ; add on number of pages within bank
        BL      BangCamUpdate
        CLRV
        EXIT

90
        ADR     lr, NoL2ForPageBeingRemovedError ; NB don't corrupt r0 yet - we need that in block as evidence
95
        STR     lr, [sp]                        ; update returned r0
        BL      StoreDebugRegs
        PullEnv                                 ; seriously broken memory
        SETV
        MOV     pc, lr

91
        ADR     lr, PageBeingRemovedNotPresentError
        B       %BT95

92
        ADR     lr, PhysicalAddressNotFoundError
        B       %BT95

StoreDebugRegs ; Note: Corrupts R0,R1
        Push    "lr"
        LDR     lr, =ZeroPage+CamMapCorruptDebugBlock
        STMIA   lr, {r0-r12}
        STR     sp, [lr, #13*4]!
        LDMIA   sp, {r0,r1}                     ; reload stacked LR & return R0 (error pointer)
        STMIB   lr, {r0,r1}                     ; LR -> LR, error -> PC
        Pull    "pc"

NoL2ForPageBeingRemovedError
        &       0
        =       "Memory Corrupt: No L2PT for page being removed", 0
        ALIGN

PageBeingRemovedNotPresentError
        &       0
        =       "Memory Corrupt: Page being removed was not present", 0
        ALIGN

PhysicalAddressNotFoundError
        &       0
        =       "Memory Corrupt: Physical address not found", 0
        ALIGN

CamMapBroke
        &       0
        =       "!!!! CAM Map Corrupt !!!!", 0
        ALIGN
; Call_CAM_Mapping
; in:   r2 = physical page number
;       r3 = logical address (2nd copy of doubly mapped area)
;       r9 = offset from 1st to 2nd copy of doubly mapped area (either source or dest, but not both)
;       r11 = PPL + CB bits
Call_CAM_Mapping
        Push    "r0, r1, r4, r6, lr"
        BL      BangCamUpdate
        Pull    "r0, r1, r4, r6, pc"

  [ FastCDA_UpFront
; CheckCacheabilityR0ByMinusR2
; in:   r0 = end of area
;       r2 = size of area (must be nonzero)
; out:  r6 has DynAreaFlags_NotCacheable set if entire region noncacheable
;              Flag clear if at least one page is cacheable
;       r0 points to start of area
;
;       4K page size assumed!
CheckCacheabilityR0ByMinusR2 ROUT
        Entry   "r2"
10
        SUB     r0, r0, #4096
        BL      GetPageFlagsForR0IntoR6
        SUBS    r2, r2, #4096
        TSTNE   r6, #DynAreaFlags_NotCacheable
        BNE     %BT10
        SUB     r0, r0, r2
        EXIT
  ]

; +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; In    r0 bits 0..6 = area number
;       r0 bit 7 set => return max area size in r2 (implemented 13 Jun 1990)
;                       this will return an error if not implemented
; Out   r0 = address of area
;       r1 = current size of area
;       r2 = max size of area if r0 bit 7 set on entry (preserved otherwise)

; TMD 19-May-93: When this is updated to new CDA list, change meaning as follows:

; r0 in range 0..&7F    return address, size of area r0
;             &80..&FF  return address, size, maxsize of area (r0-&80)
;             &100..    return address, size, maxsize of area r0

; TMD 20-Aug-93: New bit added - if r0 = -1 on entry, then returns info on application space
; r0 = base address (&8000)
; r1 = current size (for current task)
; r2 = maximum size (eg 16M-&8000)

ReadDynamicArea ROUT

readdyn_returnR2bit     *       &80
        ASSERT  ChangeDyn_MaxArea < readdyn_returnR2bit

        CMP     r0, #-1                         ; if finding out about app space
      [ ZeroPage = 0
        LDREQ   r1, [r0, #AplWorkSize+1]        ; then r1 = current size
      |
        LDREQ   r1, =ZeroPage
        LDREQ   r1, [r1, #AplWorkSize]
      ]
; [ HAL32
;        LDREQ   r2, [r0, #RAMLIMIT+1]
; |
        LDREQ   r2, =AplWorkMaxSize             ; and r2 = max size
; ]
        MOVEQ   r0, #&8000                      ; r0 = base address
        SUBEQ   r1, r1, r0                      ; adjust size and maxsize
        SUBEQ   r2, r2, r0                      ; to remove bottom 32K
        ExitSWIHandler EQ

; first check if it's one of the new ones

        Push    "r1,lr"
        CMP     r0, #&100                       ; if area >= &100
        MOVCS   r1, r0                          ; then just use area
        BICCC   r1, r0, #readdyn_returnR2bit    ; else knock off bit 7
  [ DynArea_QuickHandles
        BL      QCheckAreaNumber                ; out: r10 -> node
  |
        BL      CheckAreaNumber                 ; out: r10 -> node
  ]
        Pull    "r1,lr"
        BCC     %FT05                           ; [not a new one, so use old code]

        CMP     r0, #&80                        ; CS => load maxsize into R2
                                                ; (do this either if bit 7 set, or area >=&100)
        LDRCS   r2, [r10, #DANode_MaxSize]
        LDR     r11, [r10, #DANode_Flags]       ; if doubly mapped
        LDR     r1, [r10, #DANode_Size]         ; r1 = current size
        LDR     r0, [r10, #DANode_Base]         ; r0 -> base
        TST     r11, #DynAreaFlags_DoublyMapped
        SUBNE   r0, r0, r1                      ; then return start of 1st copy for compatibility
        ExitSWIHandler
05
        ADRL    r0, ErrorBlock_BadDynamicArea
      [ International
        Push    "lr"
        BL      TranslateError
        Pull    "lr"
      ]
        B       SLVK_SetV

        MakeErrorBlock  BadDynamicArea

; *************************************************************************
; User access to CAM mapping
; ReadMemMapInfo:
; returns R0 = pagsize
;         R1 = number of pages in use  (= R2 returned from SetEnv/Pagesize)
; *************************************************************************

ReadMemMapInfo_Code
      LDR      R10, =ZeroPage
      LDR      R0, [R10, #Page_Size]
      LDR      R1, [R10, #RAMLIMIT]    ; = total memory size
      ADRL     R11, PageShifts-1
      LDRB     R11, [R11, R0, LSR #12]
      MOV      R1, R1, LSR R11
      ExitSWIHandler

; ************************************************************************
; SWI ReadMemMapEntries: R0 pointer to list.
;  Entries are three words long, the first of which is the CAM page number.
;  List terminated by -1.
; Returns pagenumber (unaltered)/address/PPL triads as below
; ************************************************************************

ReadMemMapEntries_Code  ROUT
        Push    "r0,r14"
        LDR     r14, =ZeroPage
        LDR     r10, [r14, #CamEntriesPointer]
        LDR     r14, [r14, #MaxCamEntry]
01
        LDR     r12, [r0], #4                   ; page number
        CMP     r12, r14
        Pull    "r0,r14", HI
        ExitSWIHandler HI

   [ ChocolateAMB
        ;may need AMB to make mapping honest (as if not lazy), if page is in currently mapped app
        Push    "r0, lr"
        MOV     r0, r12                         ; page number to make honest
        BL      AMB_MakeHonestPN
        Pull    "r0, lr"
   ]

        ADD     r11, r10, r12, LSL #3
        LDMIA   r11, {r11, r12}
        STMIA   r0!, {r11, r12}
        B       %BT01

; ************************************************************************
; SWI FindMemMapEntries:
; In:  R0 -> table of 12-byte page entries
;       +0      4       probable page number (0..npages-1) (use 0 if no idea)
;       +4      4       logical address to match with
;       +8      4       undefined
;       terminated by a single word containing -1
;
; Out: table of 12-byte entries updated:
;       +0      4       actual page number (-1 => not found)
;       +4      4       address (preserved)
;       +8      4       page protection level (3 if not found)
;       terminator preserved
;
; ************************************************************************

FindMemMapEntries_Code  ROUT

; Code for expanded CAM map version

        Push    "r0, r9, r14"
        LDR     r14, =ZeroPage
        LDR     r9, [r14, #MaxCamEntry]
        LDR     r14, [r14, #CamEntriesPointer]  ; r14 -> start of cam map
        ADD     r9, r14, r9, LSL #3             ; r9 -> first word of last entry in cam map
10
        LDR     r10, [r0, #0]                   ; r10 = guess page number (or -1)
        CMP     r10, #-1                        ; if -1 then end of list
        Pull    "r0, r9, r14", EQ               ; so restore registers
        ExitSWIHandler EQ                       ; and exit

        LDR     r11, [r0, #4]                   ; r11 = logical address

   [ ChocolateAMB
        ;may need AMB to make mapping honest (as if not lazy), if page is in currently mapped app
        Push    "r0, lr"
        MOV     r0, r11                         ; logical address to make honest
        BL      AMB_MakeHonestLA                ; note, quickly dismisses non app space addresses
        Pull    "r0, lr"
   ]

        ADD     r10, r14, r10, LSL #3           ; form address with 'guess' page
        CMP     r10, r9                         ; if off end of CAM
        BHI     %FT20                           ; then don't try to use the guess

        LDR     r12, [r10]                      ; load address from guessed page
        TEQ     r11, r12                        ; compare address
        BEQ     %FT60                           ; if equal, then guessed page was OK
20

; for now, cheat by looking in L2PT, to see if we can speed things up

        Push    "r5-r8"                         ; need some registers here!
        LDR     r10, =L2PT
        MOV     r8, r11, LSR #12                ; r8 = logical page number
        ADD     r8, r10, r8, LSL #2             ; r8 -> L2PT entry for log.addr
        MOV     r5, r8, LSR #12                 ; r5 = page offset to L2PT entry for log.addr
        LDR     r5, [r10, r5, LSL #2]           ; r5 = L2PT entry for L2PT entry for log.addr
        TST     r5, #3                          ; if page not there
        SUBEQ   r10, r9, #8                     ; then invalid page so go from last one
        BEQ     %FT45
        LDR     r8, [r8]                        ; r8 = L2PT entry for log.addr
        MOV     r8, r8, LSR #12                 ; r8 = physaddr / 4K

        LDR     r5, =ZeroPage+PhysRamTable
        SUB     r10, r14, #8
30
        CMP     r10, r9                         ; have we run out of RAM banks?
        BCS     %FT40                           ; then fail
        LDMIA   r5!, {r6,r7}                    ; load next address, size
        SUB     r6, r8, r6, LSR #12             ; number of pages into this bank
        CMP     r6, r7, LSR #12                 ; if more than there are
        BICCS   r7, r7, #&F00
        ADDCS   r10, r10, r7, LSR #12-3         ; then advance CAM entry position
        BCS     %BT30                           ; and loop to next bank

        ADD     r10, r10, r6, LSL #3            ; advance by 2 words for each page in this bank
40
        SUBCS   r10, r9, #8                     ; search from last one, to fail quickly (if CS)
45
        Pull    "r5-r8"
50
        CMP     r10, r9                         ; if not just done last one,
        LDRNE   r12, [r10, #8]!                 ; then get logical address
        TEQNE   r11, r12                        ; compare address
        BNE     %BT50                           ; loop if not same and not at end

; either found page or run out of pages

        TEQ     r11, r12                        ; see if last one matched
                                                ; (we always load at least one!)
60
        LDREQ   r12, [r10, #4]                  ; if match, then r12 = PPL
        SUBEQ   r10, r10, r14                   ; and page number=(r10-r14)>>3
        MOVEQ   r10, r10, LSR #3

        MOVNE   r10, #-1                        ; else unknown page number indicator
        MOVNE   r12, #3                         ; and PPL=3 (no user access)

        STMIA   r0!, {r10-r12}                  ; store all 3 words
        B       %BT10                           ; and go back for another one

;**************************************************************************
; SWI SetMemMapEntries: R0 pointer to list of CAM page/address/PPL triads,
;  terminated by -1.
; address of -1 means "put the page out of the way"
; +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

; note, if ChocolateAMB, no MakeHonest consideration here, this SWI just
; changes the mapping of pages regardless of their current mapping, and
; assumes the caller knows what he is doing (ho ho)
;

SetMemMapEntries_Code  ROUT
        Push    "r0-r6, r9, lr"
        MOV     r12, r0

; BangCamUpdate takes entry no in r2, logaddr to set to in r3
; r9 current MEMC, r11 = PPL
; corrupts r0,r1,r4,r6

        LDR     r9, =ZeroPage
        LDR     r5, [r9, #MaxCamEntry]
        LDR     r9, [r9, #MEMC_CR_SoftCopy]
01
        LDR     r2, [r12], #4
        CMP     r2, r5
        BHI     %FT02                   ; finished
        LDMIA   r12!, {r3, r11}
 [ {FALSE}
        AND     r11, r11, #3
 ]
        CMP     r3, #-1
        LDRHS   r3, =DuffEntry
        MOVHS   r11, #AP_Duff
        BL      BangCamUpdate
        B       %BT01
02
        Pull    "r0-r6, r9, lr"
        ExitSWIHandler

        LTORG



;**************************************************************************
;
;       DynamicAreaSWI - Code to handle SWI OS_DynamicArea
;
; in:   r0 = reason code
;       Other registers depend on reason code
;
; out:  Depends on reason code
;


DAReason_Create          *  0
DAReason_Remove          *  1
DAReason_GetInfo         *  2
DAReason_Enumerate       *  3
DAReason_Renumber        *  4
 [ ShrinkableDAs
DAReason_ReturnFree      *  5   ;if ShrinkableDAs, else reason code invalid
 ]
 [ DynArea_QuickHandles
DAReason_GetChangeInfo   *  6   ;if DynArea_Quickhandles, else reason code invalid
DAReason_EnumerateInfo   *  7   ;if DynArea_Quickhandles, else reason code invalid
DAReason_SetClamps       *  8   ;if DynArea_Quickhandles, else reason code invalid
 ]
 [ DA_Batman
DAReason_SparseClaim     *  9   ;if DA_Batman, else reason code invalid
DAReason_SparseRelease   * 10   ;if DA_Batman, else reason code invalid
 ]
DAReason_Limit           * 11   ;end of defined DA reasons


DynArea_NewAreas *      &100            ; Allocated area numbers start here
DynArea_NewAreasBase *  &04000000       ; Allocated area addresses start here


; Bits in dynamic area flags (and page flags)
;
; rearranged slightly for Ursula - allow room for some expansion of DA flags in future without moving page flags
; mjs June 2001 merged the Ursula arrangement into HALised kernel
;
DynAreaFlags_APBits             * 15 :SHL:  0   ; currently only uses 2 bits, but may extend to allow svc/usr read-only
DynAreaFlags_NotBufferable      *  1 :SHL:  4
DynAreaFlags_NotCacheable       *  1 :SHL:  5
DynAreaFlags_DoublyMapped       *  1 :SHL:  6
DynAreaFlags_NotUserDraggable   *  1 :SHL:  7
DynAreaFlags_NeedsSpecificPages *  1 :SHL:  8   ; whether area will ever require particular physical pages
DynAreaFlags_Shrinkable         *  1 :SHL:  9   ; whether area may be shrunk when need more space in free pool
DynAreaFlags_SparseMap          *  1 :SHL: 10   ; whether area may have non-contiguous mapping of pages (Holey dynamic areas Batman!)
DynAreaFlags_PiersBinding       *  1 :SHL: 11   ; whether area is bound to client application, and so may be swapped out with it (not implemented yet)
DynAreaFlags_CPBits             *  7 :SHL: 12   ; cache policy variant for NotBufferable and NotCacheable bits

; Cache policies
;
CP_NCNB_Default                 * 0             ; no policy variants

CP_NCB_Default                  * 0             ; OS decides buffer policy (currently always coalescing)
CP_NCB_NonMerging               * 1             ; Non-merging write buffer. If not available, unbuffered.
CP_NCB_Merging                  * 2             ; Merging write buffer. If not available, non-merging.

CP_CNB_Default                  * 0             ; OS decides cache policy (writethrough). NCNB if not available
CP_CNB_Writethrough             * 1             ; Writethrough cacheable, non-buffered. If not available, NCNB.
CP_CNB_Writeback                * 2             ; Writeback cacheable, non-buffered. If not available,CNB_Writethrough.

CP_CB_Default                   * 0             ; OS decides cache policy (WB if available, W alloc if HAL requests)
CP_CB_Writethrough              * 1             ; Writethrough cacheable, read allocate. If not available, NCB_Merging
CP_CB_WritebackReadAlloc        * 2             ; Writeback cacheable, read allocate. If not available, writethrough.
CP_CB_WritebackWriteAlloc       * 3             ; Writeback cacheable, write allocate. If not available, WB/R.
CP_CB_AlternativeDCache         * 4             ; Use XScale/SA11x0 mini-data cache. If not available, CB_Default.

DynAreaFlags_NeedsDMA           *  1 :SHL: 15   ; only allocate from DMAable memory
;
; No more bits left for easy flag expansion. Will have to start claiming bits
; from 16 to 31, or shuffle some of the following flags further up
; (which should be safe in theory, as they all should be kernel private)
;
DynAreaFlags_AccessMask * DynAreaFlags_APBits :OR: DynAreaFlags_NotBufferable :OR: DynAreaFlags_NotCacheable :OR: DynAreaFlags_DoublyMapped :OR: DynAreaFlags_CPBits
;
; The following bits are only present in page flags
;
TempUncacheableShift            * 16
PageFlags_TempUncacheableBits   * 15 :SHL: TempUncacheableShift    ; temporary count of uncacheability, used by DMA mgr (via OS_Memory 0)
PageFlags_Unavailable           *  1 :SHL: 20                      ; physical page may not be requested by a PreShrink handler
;
; Temporary flags only used by kernel
;
PageFlags_Required              *  1 :SHL: 21                      ; physical page asked for by handler
PageFlags_Unsafe                *  1 :SHL: 22                      ; skip cache/TLB maintenance in BangCamUpdate. flag not saved to CAM map.


DynamicAreaSWI Entry
        BL      DynAreaSub
        PullEnv
        ORRVS   lr, lr, #V_bit
        ExitSWIHandler

DynAreaSub
        CMP     r0, #DAReason_Limit
        ADDCC   pc, pc, r0, LSL #2
        B       DynArea_Unknown
        B       DynArea_Create
        B       DynArea_Remove
        B       DynArea_GetInfo
        B       DynArea_Enumerate
        B       DynArea_Renumber
 [ ShrinkableDAs
        B       DynArea_ReturnFree
 |
        B       DynArea_Unknown
 ]
 [ DynArea_QuickHandles
        B       DynArea_GetChangeInfo
        B       DynArea_EnumerateInfo
        B       DynArea_SetClamps
 |
        B       DynArea_Unknown
        B       DynArea_Unknown
        B       DynArea_Unknown
 ]
 [ DA_Batman
        B       DynArea_SparseClaim
        B       DynArea_SparseRelease
 |
        B       DynArea_Unknown
        B       DynArea_Unknown
 ]
;
; unknown OS_DynamicArea reason code
;
DynArea_Unknown
        ADRL    r0, ErrorBlock_HeapBadReason
DynArea_TranslateAndReturnError
      [ International
        Push    lr
        BL      TranslateError
        Pull    lr
      ]
DynArea_ReturnError
        SETV
        MOV     pc, lr

;**************************************************************************
;
;       DynArea_Create - Create a dynamic area
;
;       Internal routine called by DynamicAreaSWI and by reset code
;
; in:   r0 = reason code (0)
;       r1 = new area number, or -1 => RISC OS allocates number
;       r2 = initial size of area (in bytes)
;       r3 = base logical address of area, or -1 => RISC OS allocates address space
;       r4 = area flags
;               bits 0..3 = access privileges
;               bit  4 = 1 => not bufferable
;               bit  5 = 1 => not cacheable
;               bit  6 = 0 => area is singly mapped
;                      = 1 => area is doubly mapped
;               bit  7 = 1 => area is not user draggable in TaskManager window
;               bit  8 = 1 => area may require specific physical pages
;               bit  9 = 1 => area is shrinkable (only implemented if ShrinkableDAs)
;               bit 10 = 1 => area may be sparsely mapped (only implemented if DA_Batman)
;               bit 11 = 1 => area is bound to client application (allows areas to be overlayed in address space)
;                             not implemented yet, but declared in public API for Ursula
;               bits 12..14 => cache policy (if bits 4 or 5 set)
;               bit 15 = 1 => area requires DMA capable pages (is bit 12 in ROL's OS!)
;               bits 16..31 reserved for future expansion + internal page flags (should be 0)
;
;       r5 = maximum size of area, or -1 for total RAM size
;       r6 -> area handler routine
;       r7 = workspace pointer for area handler (-1 => use base address)
;       r8 -> area description string (null terminated) (gets copied)
;
; out:  r1 = given or allocated area number
;       r3 = given or allocated base address of area
;       r5 = given or allocated maximum size
;       r0, r2, r4, r6-r9 preserved
;       r10-r12 may be corrupted
;

DynArea_Create Entry "r2,r6-r8"
        CMP     r1, #-1         ; do we have to allocate a new area number
        BEQ     %FT10

  [ DynArea_QuickHandles
        CMP     r1, #DynArea_NewAreas
        BLO     %FT06
        CMP     r1, #DynArea_NewAreas+DynArea_NumQHandles
        BLO     %FT08           ; can't choose your own quick handle
  ]

06
  [ DynArea_QuickHandles
        BL      QCheckAreaNumber ; see if area number is unique
  |
        BL      CheckAreaNumber ; see if area number is unique
  ]
        BCC     %FT20           ; didn't find it, so OK

08
        ADR     r0, ErrorBlock_AreaAlreadyExists
DynArea_ErrorTranslateAndExit
        PullEnv
        B       DynArea_TranslateAndReturnError

        MakeErrorBlock  AreaAlreadyExists
        MakeErrorBlock  AreaNotOnPageBdy
        MakeErrorBlock  OverlappingAreas
        MakeErrorBlock  CantAllocateArea
        MakeErrorBlock  CantAllocateLevel2
        MakeErrorBlock  UnknownAreaHandler

; we have to allocate an area number for him

  [ DynArea_QuickHandles
10
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws ]
        LDR     r1, DynArea_FreeQHandles          ;get index of next available quick handle, if any free
        CMP     r1, #0
        ADDNE   r1, r1, #DynArea_NewAreas-1       ;compute quick handle from index
        BNE     %FT20
        LDR     r1, DynArea_TreacleGuess          ;last non-quick number allocated
12
        ADD     r1, r1, #1                        ; increment for next guess (collisions should be *very* rare)
        CMP     r1, #DynArea_NewAreas+DynArea_NumQHandles
        MOVLO   r1, #DynArea_NewAreas+DynArea_NumQHandles
        BL      QCheckAreaNumber
        BCS     %BT12                             ; and try again
  |
10
        MOV     r1, #DynArea_NewAreas
12
        BL      CheckAreaNumber
        ADDCS   r1, r1, #1      ; that area number already exists, so increment
        BCS     %BT12           ; and try again
  ]

20

; now validate maximum size of area

  [ DynArea_QuickHandles
    ;
    ; apply clamps on max size, as set by last call to OS_DynamicArea 8
    ;
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
    [ DA_Batman
        TST     r4, #DynAreaFlags_SparseMap
        BEQ     DAC_notsparse
        LDR     r10, DynArea_OD8Clamp3   ; clamp for sparse dynamic area
        CMP     r5, r10                  ; if requested max size is > relevant clamp
        MOVHI   r5, r10                  ; then clamp it!
        LDR     r10, [sp]                ; requested initial size, from stack
        CMP     r5, r10
        MOVLO   r5, r10                  ; we must try to honour initial size (allowed to break clamp)
        LDR     r10, =ZeroPage
        LDR     r11, [r10, #Page_Size]
        B       DAC_roundup
DAC_notsparse
    ]
        CMP     r5, #-1
        LDREQ   r10, DynArea_OD8Clamp1   ; clamp for max size requested of -1
        LDRNE   r10, DynArea_OD8Clamp2   ; clamp for max size requested of some specific value
        CMP     r5, r10                  ; if requested max size is > relevant clamp
        MOVHI   r5, r10                  ; then clamp it!
        LDR     r10, [sp]                ; requested initial size, from stack
        CMP     r5, r10
        MOVLO   r5, r10                  ; we must try to honour initial size (allowed to break clamp)
  ]

        LDR     r10, =ZeroPage
        LDR     r11, [r10, #Page_Size]
        LDR     r10, [r10, #RAMLIMIT]   ; get total RAM size
        CMP     r5, r10                 ; if requested maximum size is > total
        MOVHI   r5, r10                 ; then set max to total (NB. -1 passed in always yields HI)

DAC_roundup
        SUB     r10, r11, #1            ; also round up to a page multiple
        ADD     r5, r5, r10
        BIC     r5, r5, r10

; now see if we have to allocate a logical address space

        CMP     r3, #-1                 ; if we are to allocate the address space
        BEQ     %FT30                   ; then go do it

; otherwise we must check that the address does not clash with anything else

        TST     r3, r10                         ; does it start on a page boundary
        ADRNE   r0, ErrorBlock_AreaNotOnPageBdy ; if not then error
        BNE     DynArea_ErrorTranslateAndExit

        BL      CheckForOverlappingAreas        ; in: r3 = address, r4 = flags, r5 = size; out: if error, r0->error, V=1
        BVC     %FT40
25
        PullEnv
        B       DynArea_ReturnError

30
        BL      AllocateAreaAddress             ; in: r4 = flags, r5 = size of area needed; out: r3, or V=1, r0->error
        BVS     %BT25
40
        BL      AllocateBackingLevel2           ; in: r3 = address, r4 = flags, r5 = size; out: VS if error
        BVS     %BT25

        Push    "r0,r1,r3"
  [ DynArea_QuickHandles
    ;we save work and reduce stress on system heap by claiming only one block, consisting of node followed by
    ;string space (always maximum length, but typically not overly wasteful compared to 2nd block overhead)
    ;
        MOV     r3, #DANode_NodeSize + DynArea_MaxNameLength + 1
  |
        MOV     r3, #DANode_NodeSize
  ]
        BL      ClaimSysHeapNode                ; out: r2 -> node
        STRVS   r0, [sp]
        Pull    "r0,r1,r3"
        BVS     %BT25                           ; failed to claim node

; now store data in node (could probably use STM if we shuffled things around)

        CMP     r7, #-1                         ; if workspace ptr = -1
        MOVEQ   r7, r3                          ; then use base address

        STR     r1, [r2, #DANode_Number]
        STR     r3, [r2, #DANode_Base]
  [ DA_Batman
        ;disallow some awkward flag options if SparseMap set (no error), and temporarily create as not sparse
        ;also disallow a DA handler
        TST     r4, #DynAreaFlags_SparseMap
        STREQ   r4, [r2, #DANode_Flags]
        BICNE   r7, r4, #DynAreaFlags_DoublyMapped + DynAreaFlags_NeedsSpecificPages + DynAreaFlags_Shrinkable + DynAreaFlags_SparseMap
        ORRNE   r7, r7, #DynAreaFlags_NotUserDraggable
        STRNE   r7, [r2, #DANode_Flags]
        MOVNE   r6, #0
        MOVNE   r7, #0
  |
        STR     r4, [r2, #DANode_Flags]
  ]
        STR     r5, [r2, #DANode_MaxSize]
        STR     r6, [r2, #DANode_Handler]
        STR     r7, [r2, #DANode_Workspace]
        MOV     r7, #0                          ; initial size is zero
        STR     r7, [r2, #DANode_Size]          ; before we grow it

  [ HAL
        ; update lower limit on IO space growth, if this DA exceeds previous limit
      [ ZeroPage <> 0
        LDR     r7, =ZeroPage
      ]
        LDR     r6, [r7, #IOAllocLimit]
        ADD     lr, r3, r5
        CMP     lr, r6
        STRHI   lr, [r7, #IOAllocLimit]
  ]

; now make copy of string - first find out length of string

  [ DynArea_QuickHandles

        ADD     r7, r2, #DANode_NodeSize
        STR     r7, [r2, #DANode_Title]
        Push    "r0"
        MOV     r0, #DynArea_MaxNameLength
        TEQ     r8, #0
    [ DynArea_NullNamePtrMeansHexString
        ASSERT  DynArea_MaxNameLength > 8
        BNE     %FT45
        Push    "r1, r2"
        MOV     r0, r1                          ;string is 8-digit hex of DA number
        MOV     r1, r7
        MOV     r2, #DynArea_MaxNameLength+1
        SWI     XOS_ConvertHex8
        Pull    "r1, r2"
        B       %FT55
    |
        BEQ     %FT50                           ;assume NULL ptr to mean no DA name
    ]
45
        LDRB    r6, [r8], #1
        STRB    r6, [r7], #1
        SUB     r0, r0, #1
        TEQ     r6, #0
        TEQNE   r0, #0
        BNE     %BT45
50
        MOV     r0, #0
        STRB    r0, [r7], #1
55
        Pull    "r0"

  |

        MOV     r7, r8
45
        LDRB    r6, [r7], #1
        TEQ     r6, #0
        BNE     %BT45

        Push    "r0-r3"
        SUB     r3, r7, r8                      ; r3 = length inc. term.
        BL      ClaimSysHeapNode
        STRVS   r0, [sp]
        MOV     r7, r2
        Pull    "r0-r3"
        BVS     StringNodeClaimFailed

        STR     r7, [r2, #DANode_Title]
50
        LDRB    r6, [r8], #1                    ; copy string into claimed block
        STRB    r6, [r7], #1
        TEQ     r6, #0
        BNE     %BT50

 ] ;DynArea_QuickHandles

; now put node on list - list is sorted in ascending base address order

        LDR     r8, =ZeroPage+DAList
        LDR     r6, [r2, #DANode_Base]
60
        MOV     r7, r8
        ASSERT  DANode_Link = 0
        LDR     r8, [r7, #DANode_Link]          ; get next node
        TEQ     r8, #0                          ; if no more
        BEQ     %FT70                           ; then put it on here
        LDR     lr, [r8, #DANode_Base]
        CMP     lr, r6                          ; if this one is before ours
        BCC     %BT60                           ; then loop

70
        STR     r8, [r2, #DANode_Link]
        STR     r2, [r7, #DANode_Link]

  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        BL      AddDAToAddrLookupTable
        ;so XOS_ChangeDynamicArea can pick up the node we are still creating
        STR     r1, DynArea_CreatingHandle
        STR     r2, DynArea_CreatingPtr
        ;so initial grow won't leave resize signature
        LDR     lr, DynArea_OD6Signature
        ORR     lr, lr, #&80000000
        STR     lr, DynArea_OD6Signature
  ]

; now we need to grow the area to its requested size

        Push    "r0, r1, r2"
        LDR     r0, [r2, #DANode_Number]
        LDR     r1, [sp, #3*4]                  ; reload requested size off stack
        SWI     XOS_ChangeDynamicArea           ; deal with error - r0,r1,r2 still stacked
        BVS     %FT90
        Pull    "r0, r1, r2"

  [ DynArea_QuickHandles
;
; Now put node on alphabetically sorted list
;
        Push    "r3,r4,r5,r7,r8,r9"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        ADR     r8, DynArea_SortedList - DANode_SortLink ;so that [r8, #DANode_SortLink] addresses list header)
75
        MOV     r7, r8                       ; previous
        LDR     r8, [r7, #DANode_SortLink]
        TEQ     r8, #0
        BEQ     %FT78
        ;ho hum, UK case insensitive string compare
        LDR     r3, [r2, #DANode_Title]
        LDR     r9, [r8, #DANode_Title]
76
        LDRB    r4, [r3],#1
        uk_LowerCase r4,r11
        LDRB    r5, [r9],#1
        uk_LowerCase r5,r11
        CMP     r4, r5
        BNE     %FT77
        CMP     r4, #0
        BNE     %BT76
77
        BHI     %BT75
78
        STR     r2, [r7, #DANode_SortLink]
        STR     r8, [r2, #DANode_SortLink]
79
        Pull    "r3,r4,r5,r7,r8,r9"
  ] ;DynArea_QuickHandles

  [ DA_Batman
        TST     r4, #DynAreaFlags_SparseMap
        LDRNE   r11, [r2, #DANode_Flags]
        ORRNE   r11, r11, #DynAreaFlags_SparseMap ; set this in node now (after initial grow)
        STRNE   r11, [r2, #DANode_Flags]
        LDRNE   r11, [r2, #DANode_Size]
        LDRNE   lr,  [r2, #DANode_Base]
        ADDNE   r11, r11, lr
        STRNE   r11, [r2, #DANode_SparseHWM]      ; initial high water mark
  ]

  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]

        TST     r4, #DynAreaFlags_Shrinkable
        LDRNE   lr, DynArea_ShrinkableSubList
        STRNE   lr, [r2, #DANode_SubLink]
        STRNE   r2, DynArea_ShrinkableSubList   ;link onto front of Shrinkable sublist if Shrinkable

        MOV     lr, #-1
        STR     lr, DynArea_CreatingHandle      ;invalidate this now
        CMP     r1, #ChangeDyn_MaxArea
        BHI     %FT72
        ADR     lr, DynArea_SysQHandleArray
        STR     r2, [lr, r1, LSL #2]            ;system handle - store ptr to node for quick reference
        B       %FT80
72
        LDR     lr, DynArea_OD6Signature
        STR     lr, DynArea_OD6PrevSignature
        ORR     lr, lr, #1
        STR     lr, DynArea_OD6Signature
        STR     r1, DynArea_OD6Handle
        CMP     r1, #DynArea_NewAreas
        BLO     %FT80
        CMP     r1, #DynArea_NewAreas+DynArea_NumQHandles
        BHS     %FT74
        SUB     r10, r1, #DynArea_NewAreas
        ADR     lr, DynArea_QHandleArray
        LDR     r6, [lr, r10, LSL #2]           ;pick up index of next free quick handle
        STR     r6, DynArea_FreeQHandles        ;store as index of first free quick handle
        STR     r2, [lr, r10, LSL #2]           ;store ptr to node for quick reference
        B       %FT80
74
        LDR     r10, DynArea_TreacleGuess
        ADD     r10, r10, #1
        STR     r10, DynArea_TreacleGuess       ;non-quick handle allocated, increment for next allocate
80
  ] ;DynArea_QuickHandles


; Now issue service to tell TaskManager about it

        Push    "r0, r1, r2"
        MOV     r2, r1                          ; r2 = area number
        MOV     r1, #Service_DynamicAreaCreate
        BL      Issue_Service
        Pull    "r0, r1, r2"

        CLRV
        EXIT

90

; The dynamic area is not being created, because we failed to grow the area to the required size.
; The area itself will have no memory allocated to it (since if grow fails it doesn't move any).
; We must delink the node from our list, free the string node, and then the area node itself.

        STR     r0, [sp, #0*4]                  ; remember error pointer in stacked r0
        STR     r8, [r7, #DANode_Link]          ; delink area
  [ :LNOT: DynArea_QuickHandles
        LDR     r2, [r2, #DANode_Title]
        BL      FreeSysHeapNode                 ; free title string node
  ]
        Pull    "r0, r1, r2"                    ; pull stacked registers, and drop thru to...

  [ :LNOT: DynArea_QuickHandles
; The dynamic area is not being created, because there is no room to allocate space for the title string
; We must free the DANode we have allocated
; It would be nice to also free the backing L2, but we'll leave that for now.

; in: r2 -> DANode

StringNodeClaimFailed
  ]

        Push    "r0, r1"
        BL      FreeSysHeapNode
        Pull    "r0, r1"
  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        MOV     lr, #-1
        STR     lr, DynArea_CreatingHandle
  ]
        PullEnv
        B       DynArea_ReturnError

        LTORG

; Add a dynamic area to the quick address lookup table
; In:
;  R2 = DANode ptr
;  R11 = DynArea_ws
AddDAToAddrLookupTable
        Entry   "r0-r1,r3,r6"
        ADRL    r0, DynArea_AddrLookup
        LDR     r1, [r2, #DANode_Flags]
        LDR     r3, [r2, #DANode_MaxSize]
        LDR     r6, [r2, #DANode_Base]
        TST     r1, #DynAreaFlags_DoublyMapped
        SUBNE   r6, r6, r3                      ; Get true start address
        MOVNE   r3, r3, LSL #1
        AND     r1, r6, #DynArea_AddrLookupMask ; Round down start address
        ADD     lr, r6, r3
        AND     r3, lr, #DynArea_AddrLookupMask
        TEQ     lr, r3
        ADDNE   r3, r3, #DynArea_AddrLookupSize ; Round up end address
        SUB     r3, r3, r1
        ADD     r0, r0, r1, LSR #30-DynArea_AddrLookupBits
71
        LDR     lr, [r0], #4
        TEQ     lr, #0
        STREQ   r2, [r0, #-4]
        BEQ     %FT72
        LDR     lr, [lr, #DANode_Base]
        CMP     lr, r6
        STRHI   r2, [r0, #-4]                   ; Update LUT if current entry starts after us
72
        SUBS    r3, r3, #DynArea_AddrLookupSize
        BNE     %BT71
        EXIT

;**************************************************************************
;
;       DynArea_Remove - Remove a dynamic area
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (1)
;       r1 = area number
;
; out:  r10-r12 may be corrupted
;       All other registers preserved
;

DynArea_Remove Entry

        ;*MUST NOT USE QCheckAreaNumber* (need r11 = previous)
        BL      CheckAreaNumber         ; check that area is there
        BCC     UnknownDyn              ; [not found]

  [ DA_Batman
        Push    "r11"
        LDR     r11,[r10,#DANode_Flags]
        TST     r11,#DynAreaFlags_SparseMap
        Pull    "r11"
        BEQ     DAR_notsparse
        Push    "r0,r2-r3"
        MOV     r0,#DAReason_SparseRelease
        LDR     r2,[r10,#DANode_Base]
        LDR     r3,[r10,#DANode_MaxSize]
        SWI     XOS_DynamicArea            ;release all pages in sparse area
        STRVS   r0,[SP]
        Pull    "r0,r2-r3"
        EXIT    VS
        B       DAR_delink
DAR_notsparse
  ]

  [ DynArea_QuickHandles
        Push    "r11"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        ;so final shrink won't leave resize signature
        LDR     lr, DynArea_OD6Signature
        ORR     lr, lr, #&80000000
        STR     lr, DynArea_OD6Signature
        Pull    "r11"
  ]

; First try to shrink area to zero size

        Push    "r0-r2"
        MOV     r0, r1                  ; area number
        LDR     r2, [r10, #DANode_Size] ; get current size
        RSB     r1, r2, #0              ; negate it
        SWI     XOS_ChangeDynamicArea
        BVS     %FT80
        Pull    "r0-r2"

DAR_delink

  [ DynArea_QuickHandles
;
; delink from sorted list
;
        Push    "r0-r4,r7,r8,r11"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        ADR     r8, DynArea_SortedList - DANode_SortLink ;so that [r8, #DANode_SortLink] addresses list header)
DAR_sdloop
        MOV     r7, r8                      ;previous
        LDR     r8, [r7, #DANode_SortLink]
        TEQ     r8, #0                      ;just in case not on list, shouldn't happen
        BEQ     DAR_sddone
        TEQ     r8, r10
        BNE     DAR_sdloop
        LDR     r8, [r8, #DANode_SortLink]
        STR     r8, [r7, #DANode_SortLink]
DAR_sddone
; Delink from address lookup table
        ADRL    r0, DynArea_AddrLookup
        LDR     r1, [r10, #DANode_Flags]
        LDR     r3, [r10, #DANode_MaxSize]
        LDR     r2, [r10, #DANode_Base]
        TST     r1, #DynAreaFlags_DoublyMapped
        SUBNE   r2, r2, r3                      ; Get true start address
        MOVNE   r3, r3, LSL #1
        AND     r1, r2, #DynArea_AddrLookupMask ; Round down start address
        ADD     lr, r2, r3
        AND     r3, lr, #DynArea_AddrLookupMask
        TEQ     lr, r3
        ADDNE   r3, r3, #DynArea_AddrLookupSize ; Round up end address
        SUB     r3, r3, r1
        ADD     r0, r0, r1, LSR #30-DynArea_AddrLookupBits
DAR_adloop
        LDR     lr, [r0], #4
        TEQ     lr, r10
        BNE     DAR_adnext
        ; Update to point to next DA, or null if next is outside this chunk
        LDR     lr, [lr, #DANode_Link]
        TEQ     lr, #0
        STREQ   lr, [r0, #-4]
        BEQ     DAR_adnext
        LDR     r4, [lr, #DANode_Flags]
        LDR     r2, [lr, #DANode_Base]
        TST     r4, #DynAreaFlags_DoublyMapped
        LDRNE   r4, [lr, #DANode_MaxSize]
        SUBNE   r2, r2, r4
        AND     r2, r2, #DynArea_AddrLookupMask
        TEQ     r2, r1
        MOVNE   lr, #0
        STR     lr, [r0, #-4]
DAR_adnext
        SUBS    r3, r3, #DynArea_AddrLookupSize
        ADD     r1, r1, #DynArea_AddrLookupSize
        BNE     DAR_adloop
        Pull    "r0-r4,r7,r8,r11"

  ] ;DynArea_QuickHandles

; Now just de-link from list (r10 -> node, r11 -> prev)

        LDR     lr, [r10, #DANode_Link] ; store our link
        STR     lr, [r11, #DANode_Link] ; in prev link

  [ DynArea_QuickHandles
        ;if it is a Shrinkable area, find on Shrinkable sublist and remove it
        Push    "r0-r2, r11"
        LDR     r0, [r10, #DANode_Flags]
        TST     r0, #DynAreaFlags_Shrinkable
        BEQ     %FT06
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        ADR     r1, DynArea_ShrinkableSubList
        LDR     r2, [r1]
04
        CMP     r2, r10
        LDREQ   r2, [r2, #DANode_SubLink]
        STREQ   r2, [r1]
        BEQ     %FT06
        ADD     r1, r2, #DANode_SubLink
        LDR     r2, [r2, #DANode_SubLink]
        B       %BT04
06
        Pull    "r0-r2, r11"
  ]

        Push    "r0-r2"
  [ :LNOT: DynArea_QuickHandles
        LDR     r2, [r10, #DANode_Title]        ; free title string block
        BL      FreeSysHeapNode
  ]
        MOV     r2, r10                         ; and free node block
        BL      FreeSysHeapNode
        Pull    "r0-r2"

  [ DynArea_QuickHandles
        Push    "r2, r3"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        MOV     r2,#-1
        STR     r2, DynArea_CreatingHandle                ; invalidate these, just in case
        STR     r2, DynArea_LastTreacleHandle
        STR     r2, DynArea_LastEnumHandle
        CMP     r1, #ChangeDyn_MaxArea
        BLS     %FT08                                     ; system area being removed
        LDR     r2, DynArea_OD6Signature
        STR     r2, DynArea_OD6PrevSignature
        ORR     r2, r2, #2
        STR     r2, DynArea_OD6Signature
        STR     r1, DynArea_OD6Handle
        CMP     r1, #DynArea_NewAreas
        BLO     %FT10
        CMP     r1, #DynArea_NewAreas+DynArea_NumQHandles
        BHS     %FT10
        SUB     r2, r1, #DynArea_NewAreas-1               ; index of quick handle
        ADR     r10, DynArea_FreeQHandles                 ; so we can index array from 1
        LDR     r3, DynArea_FreeQHandles
        STR     r3, [r10, r2, LSL #2]
        STR     r2, DynArea_FreeQHandles                  ; put on front of free list
        B       %FT10
08
        ADR     r10, DynArea_SysQHandleArray
        MOV     r2,  #0
        STR     r2,  [r10, r1, LSL #2]                    ; reset system Qhandle
10
        Pull    "r2, r3"

  ]

; Issue service to tell TaskManager

        Push    "r0, r1, r2"
        MOV     r2, r1
        MOV     r1, #Service_DynamicAreaRemove
        BL      Issue_Service
        Pull    "r0, r1, r2"

        CLRV
        EXIT

; come here if shrink failed - r0-r2 stacked

80
        STR     r0, [sp]                ; overwrite stacked r0 with error pointer
        LDR     r0, [sp, #1*4]          ; reload area number
        LDR     r1, [r10, #DANode_Size] ; get size after failed shrink
        SUB     r1, r2, r1              ; change needed to restore original size
        SWI     XOS_ChangeDynamicArea   ; ignore any error from this
        Pull    "r0-r2"
        SETV
        EXIT

UnknownDyn
        ADRL    r0, ErrorBlock_BadDynamicArea
 [ International
        BL      TranslateError
 |
        SETV
 ]
        EXIT

;**************************************************************************
;
;       DynArea_GetInfo - Get info on a dynamic area
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (2)
;       r1 = area number
;
; out:  r2 = current size of area
;       r3 = base logical address
;       r4 = area flags
;       r5 = maximum size of area
;       r6 -> area handler routine
;       r7 = workspace pointer
;       r8 -> title string
;       r10-r12 may be corrupted
;       All other registers preserved
;

DynArea_GetInfo ALTENTRY
  [ DynArea_QuickHandles
        BL      QCheckAreaNumber        ; check area exists
  |
        BL      CheckAreaNumber         ; check area exists
  ]
        BCC     UnknownDyn              ; [it doesn't]

; r10 -> node, so get info

        LDR     r2, [r10, #DANode_Size]
        LDR     r3, [r10, #DANode_Base]
        LDR     r4, [r10, #DANode_Flags]
        LDR     r5, [r10, #DANode_MaxSize]
        LDR     r6, [r10, #DANode_Handler]
        LDR     r7, [r10, #DANode_Workspace]
        LDR     r8, [r10, #DANode_Title]
        CLRV
        EXIT

;**************************************************************************
;
;       DynArea_GetChangeInfo
;
;       Get info on changes to *non-system* dynamic areas
;       Reserved for Acorn use (intended for TaskManager, can only serve one client)
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (6)
;
; out:  r1 = Number of affected area, if a single change has occurred since last call,
;          = -1, if no changes or more than one change have occurred
;       r2 = signature of changes to non-system dynamic areas since last call to
;            OS_DynamicArea 6
;            bit 0 = 1 if any non-system areas have been created
;            bit 1 = 1 if any non-system areas have been removed
;            bit 2 = 1 if any non-system areas have been resized
;            bit 3 = 1 if any non-system areas have been renumbered
;            bits 4-31 reserved (undefined)
;
;Notes:
; (1) bit 2 of r2 excludes the initial grow of a created area, and the final
;     shrink of a removed area
; (2) if a single renumber has occurred, r1 is the old number

  [ DynArea_QuickHandles

DynArea_GetChangeInfo ROUT
        Push    "lr"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        LDR     r1, DynArea_OD6Handle
        LDR     r2, DynArea_OD6Signature
        LDR     lr, DynArea_OD6PrevSignature
        CMP     lr, #0
        MOVNE   r1, #-1
        CMP     r2, #0
        MOVEQ   r1, #-1
        MOV     lr, #0
        STR     lr, DynArea_OD6Signature
        STR     lr, DynArea_OD6PrevSignature
        CLRV
        Pull    "PC"

  ] ;DynArea_QuickHandles

;**************************************************************************
;
;       DynArea_EnumerateInfo
;
;       Enumerate *non-system* dynamic areas, returning selected info
;       Reserved for Acorn use (intended for TaskManager)
;
; in:   r0 = reason code (7)
;       r1 = -1 to start enumeration, or area number to continue from
;
; out:  r1 = number of next area found, or -1 if no more areas
;       r2 = current size of area, if area found
;       r3 = base logical address, if area found
;       r4 = area flags, if area found
;       r5 = maximum size of area, if area found
;       r6 -> title string, if area found
;
;Notes:
; (1) r2-r6 on exit are undefined if r1 = -1
;

  [ DynArea_QuickHandles

DynArea_EnumerateInfo ROUT
        Push    "lr"

        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]

        CMP     r1, #-1                         ; if starting from beginning
        LDREQ   r10, DynArea_SortedList         ; then load pointer to 1st node on sorted list
        BEQ     %FT10                           ; and skip

        LDR     r10, DynArea_LastEnumHandle
        CMP     r10, r1
        LDREQ   r10, DynArea_LastEnumPtr        ; pick up where we left off
        BEQ     %FT08
        BL      QCheckAreaNumber                ; else check valid area number
        BCC     %FT14

08
        LDR     r10, [r10, #DANode_SortLink]    ; find next one
10
        TEQ     r10, #0                         ; if at end
        MOVEQ   r1, #-1                         ; then return -1
        BEQ     %FT12
        LDR     r1, [r10, #DANode_Number]       ; else return number
        CMP     r1, #ChangeDyn_MaxArea
        BLS     %BT08                           ; skip if system area

        LDR     r2, [r10, #DANode_Size]         ; return rest of info
        LDR     r3, [r10, #DANode_Base]
        LDR     r4, [r10, #DANode_Flags]
        LDR     r5, [r10, #DANode_MaxSize]
        LDR     r6, [r10, #DANode_Title]

        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        STR     r1, DynArea_LastEnumHandle
        STR     r10, DynArea_LastEnumPtr        ; save a lot of messing about on next call
12
        CLRV
        Pull    "PC"

;it's a reserved call, so naff off internationalisation
14
        ADR     r0,DynArea_badei
        SETV
        Pull    "PC"
DynArea_badei
        DCD     0
        DCB     "bad DA number",0
        ALIGN

  ] ;DynArea_QuickHandles

;**************************************************************************
;
;       DynArea_SetClamps
;
;       Set clamps on max size of dynamic areas created by subsequent
;       calls to OS_DynamicArea 0
;
;   On entry
;       R0 = 8 (reason code)
;       R1 = limit on maximum size of (non-Sparse) areas created by
;            OS_DynamicArea 0 with R5 = -1, or 0 to read only
;       R2 = limit on maximum size of (non-Sparse) areas created by
;            OS_DynamicArea 0 with R5 > 0, or 0 to read only
;       R3 = limit on maximum size of Sparse areas created by
;            OS_DynamicArea 0 with R4 bit 10 set, or 0 to read only
;
;   On exit
;       R1 = previous limit for OS_DynamicArea 0 with R5 = -1
;       R2 = previous limit for OS_DynamicArea 0 with R5 > 0
;       R3 = previous limit for OS_DynamicArea 0 with R4 bit 10 set
;
;       Specifying -1 in R1 or R2 means the respective limit
;       is the RAM limit of the machine (this is the default).
;       Specifiying larger than the RAM limit in R1 or R2 is
;       equivalent to specifiying -1.
;
  [ DynArea_QuickHandles

DynArea_SetClamps ROUT
        Push    "r9,lr"

        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]

        LDR     r10, DynArea_OD8Clamp1
        LDR     lr,  DynArea_OD8Clamp2
        LDR     r9,  DynArea_OD8Clamp3

;insist on at least 1M for a clamp value (ignore anything lower)
;
        CMP     r1, #&100000
        STRHS   r1, DynArea_OD8Clamp1
        CMP     r2, #&100000
        STRHS   r2, DynArea_OD8Clamp2
        CMP     r3, #&100000
        STRHS   r3, DynArea_OD8Clamp3

        MOV     r1, r10
        MOV     r2, lr
        MOV     r3, r9

        CLRV
        Pull    "r9,PC"

  ] ;DynArea_QuickHandles

;**************************************************************************

;       DynArea_SparseClaim
;
;  Ensure region of sparse dynamic area is mapped to valid memory
;
; in:   r0 = reason code (9)
;       r1 = area number
;       r2 = base of region to claim
;       r3 = size of region to claim
;
; out:  r0-r3 preserved (error if not all of region successfully mapped)
;       r10-r12 may be corrupted
;
; action: - round base and size to page granularity
;         - scan the L2PT for each page covered
;         - find contiguous fragments of 1 or more pages that are not yet mapped-in
;         - pass each of these fragments as a psuedo DANode to OS_ChangeDynamicArea
;           via special Batcall), to 'grow' pages into each fragment
;
  [ DA_Batman

DynArea_SparseClaim ROUT
        Push    "r0-r9,lr"
        MOV     r4,#1                   ; flags operation as a claim

DynArea_SparseChange                    ; common entry point for claim and release

  [ DynArea_QuickHandles
        BL      QCheckAreaNumber        ; check area exists
  |
        BL      CheckAreaNumber         ; check area exists
  ]
        BCC     DA_naffsparse           ; area not there

        LDR     r9,[r10,#DANode_Flags]
        TST     r9,#DynAreaFlags_SparseMap
        BEQ     DA_naffsparse           ; area not sparse

        MOV     r9,#&1000               ;page size
        SUB     r9,r9,#1
        ADD     r3,r3,r2                ;base+size
        CMP     r4,#1
        BICEQ   r2,r2,r9                ;round base down to page granularity for claim
        ADDEQ   r3,r3,r9
        BICEQ   r3,r3,r9                ;round base+size up to page granularity for claim
        ADDNE   r2,r2,r9
        BICNE   r2,r2,r9                ;round base up to page granularity for release
        BICNE   r3,r3,r9                ;round base+size down to page granularity for release
        SUB     r3,r3,r2                ;rounded size

        ADD     r9,r3,r2
        LDR     r5,[r10,#DANode_Base]
        LDR     r6,[r10,#DANode_MaxSize]
        ADD     r6,r6,r5
        CMP     r2,r5
        CMPHS   r9,r5
        BLO     DA_naffsparse
        CMP     r2,r6
        CMPLS   r9,r6
        BHI     DA_naffsparse

        ADD     r5,r2,r3                   ;base+size of mapping
        LDR     r6,[r10,#DANode_SparseHWM] ;high water mark = highest claim base+size seen
        CMP     r4,#1
        BEQ     %FT08
        CMP     r5,r6
        SUBHI   r3,r6,r2                   ;for release we can save work by trimming to high water mark
        B       %FT09                      ;r3 is now trimmed size (may be <=0 for trim to nothing)
08
        CMP     r5,r6
        STRHI   r5,[r10,#DANode_SparseHWM] ;for claim remember highest base+size as high water mark
09
        SUB     SP,SP,#DANode_NodeSize  ;room for temporary DANode on stack
        MOV     r9,r10                  ;actual sparse area DANode
        MOV     r5,SP
        MOV     r6,#DANode_NodeSize
10
        LDR     r7,[r9],#4           ;copy sparse area node to temp node
        STR     r7,[r5],#4
        SUBS    r6,r6,#4
        BNE     %BT10
        ADD     r3,r2,r3             ;stop address
;
        MOV     r5,#L2PT
        ADD     r5,r5,r2,LSR #10     ;r5 -> L2PT for base (assumes 4k page)
        MOV     r8,r2                ;start address
;
;look for next fragment of region that needs to have mapping change
20
        CMP     r8,r3
        BHS     %FT50                ;done
        LDR     r6,[r5],#4           ;pick-up next L2PT entry
        CMP     r4,#0                ;if operation is a release...
        CMPEQ   r6,#0                ;...and L2PT entry is 0 (not mapped)...
        ADDEQ   r8,r8,#&1000         ;...then skip page (is ok)
        BEQ     %BT20
        CMP     r4,#0                ;if operation is a claim (not 0)...
        CMPNE   r6,#0                ;...and L2PT entry is non-0 (mapped)...
        ADDNE   r8,r8,#&1000         ;...then skip page (is ok)
        BNE     %BT20
        MOV     r1,#&1000            ;else we need to do a change (1 page so far)
30
        ADD     r9,r8,r1
        CMP     r9,r3
        BHS     %FT40
        LDR     r6,[r5],#4           ;pick-up next L2PT entry
        CMP     r4,#1                ;if operation is a release (not 1)...
        CMPNE   r6,#0                ;...and L2PT entry is non-0 (mapped)...
        ADDNE   r1,r1,#&1000         ;...then count page as needing change
        BNE     %BT30
        CMP     r4,#1                ;if operation is a claim...
        CMPEQ   r6,#0                ;...and L2PT entry is 0 (not mapped)...
        ADDEQ   r1,r1,#&1000         ;...then count page as needing change
        BEQ     %BT30
;set up pseudo DA and do Batcall to change mapping of fragment we have found
40
        MOV     r2,SP                  ;temp DANode
        STR     r8,[r2,#DANode_Base]
        ADD     r8,r8,r1
        ADD     r8,r8,#&1000           ;next address to check after fragment
        CMP     r4,#1
        MOVEQ   r9,#0                  ;start size of 0 for claim
        MOVNE   r9,r1                  ;start size of fragment size for release
        STR     r9,[r2,#DANode_Size]
        STR     r1,[r2,#DANode_MaxSize]
        MOV     r0,#ChangeDyn_Batcall
        CMP     r4,#0
        RSBEQ   r1,r1,#0               ;batshrink for release, batgrow for claim
        SWI     XOS_ChangeDynamicArea
        TEQ     r4,#0
        RSBEQ   r1,r1,#0
        LDR     r9,[r10,#DANode_Size]
        ADD     r9,r9,r1
        STR     r9,[r10,#DANode_Size]
        BVC     %BT20
;
50
        ADD     SP,SP,#DANode_NodeSize   ;drop temp DANode
        BVS     %FT52
        BL      DA_sparse_serviceandsig
        Pull    "r0-r9,PC"
;
52
        BL      DA_sparse_serviceandsig
        SETV
        STR     r0,[SP]
        Pull    "r0-r9,PC"

DA_naffsparse
        ADR     r0,DA_naffsparseinnit
        SETV
        STR     r0,[SP]
        Pull    "r0-r9,PC"
DA_naffsparseinnit
        DCD     0
        DCB     "invalid OS_DynamicArea sparse claim/release",0
        ALIGN

DA_sparse_serviceandsig ROUT
        Push    "r0,LR"
        LDR     r1,[r10,#DANode_Number]
   [ DynArea_QuickHandles
        LDR     r11,=ZeroPage
        LDR     r11,[r11, #DynArea_ws]
        LDR     r5,DynArea_OD6Signature
        STR     r5,DynArea_OD6PrevSignature
        ORR     r5,r5,#4                     ;signal a resize
        STR     r5,DynArea_OD6Signature
        STR     r1,DynArea_OD6Handle
   ]
        MOV     r2,r1                    ;area number
        MOV     r0,#0                    ;nominal 'grow/shrink' of 0 for service call
        MOV     r1,#Service_MemoryMoved
        BL      Issue_Service
        Pull    "r0,PC"

  ] ;DA_Batman

;**************************************************************************
;
;       DynArea_SparseRelease
;
;  Allow region of sparse dynamic area to release memory to free pool
;
; in:   r0 = reason code (10)
;       r1 = area number
;       r2 = base of region to release
;       r3 = size of region to release
;
; out:  r0-r3 preserved (error if not all of region successfully released)
;       r10-r12 may be corrupted
;
;
; action: - similar to DynArea_SparseClaim, but does 'shrinks' on fragments
;           that are mapped in

  [ DA_Batman

DynArea_SparseRelease ROUT
        Push    "r0-r9,lr"
        MOV     r4,#0                   ; flags operation as a release
        B       DynArea_SparseChange    ; jump to common code

  ] ;DA_Batman

;**************************************************************************
;
;       DynArea_Enumerate - Enumerate dynamic areas
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (3)
;       r1 = -1 to start enumeration, or area number to continue from
;
; out:  r1 = next area number or -1 if no next
;       r10-r12 may be corrupted
;       All other registers preserved

DynArea_Enumerate ALTENTRY
  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
  ]
        CMP     r1, #-1                         ; if starting from beginning
  [ DynArea_QuickHandles
        LDREQ   r10, DynArea_SortedList         ; then load pointer to 1st node on sorted list
  |
    [ ZeroPage = 0
        LDREQ   r10, [r1, #DAList+1]            ; then load pointer to 1st node
    |
        LDREQ   r10, =ZeroPage
        LDREQ   r10, [r10, #DAList]
    ]
  ]
        BEQ     %FT10                           ; and skip

  [ DynArea_QuickHandles
        LDR     r10, DynArea_LastEnumHandle
        CMP     r10, r1
        LDREQ   r10, DynArea_LastEnumPtr        ; pick up where we left off
        BEQ     %FT08
        BL      QCheckAreaNumber                ; else check valid area number
  |
        BL      CheckAreaNumber                 ; else check valid area number
  ]
        BCC     UnknownDyn                      ; complain if passed in duff area number

08
  [ DynArea_QuickHandles
        LDR     r10, [r10, #DANode_SortLink]    ; find next one
  |
        LDR     r10, [r10, #DANode_Link]        ; find next one
  ]
10
        TEQ     r10, #0                         ; if at end
        MOVEQ   r1, #-1                         ; then return -1
        BEQ     %FT12
        LDR     r1, [r10, #DANode_Number]       ; else return number

  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        STR     r1, DynArea_LastEnumHandle
        STR     r10, DynArea_LastEnumPtr        ; save a lot of messing about on next call
  ]
12
        CLRV
        EXIT

;**************************************************************************
;
;       DynArea_Renumber - Renumber dynamic area
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (4)
;       r1 = old area number
;       r2 = new area number
;

DynArea_Renumber ALTENTRY
        CMP     r1, #ChangeDyn_MaxArea
        BLS     %FT92                           ; can't renumber a system area
        CMP     r1, #ChangeDyn_MaxArea
        BLS     %FT92
  [ DynArea_QuickHandles
        CMP     r1, #DynArea_NewAreas
        BLO     %FT10
        CMP     r1, #DynArea_NewAreas+DynArea_NumQHandles
        BLO     %FT92                           ; can't renumber a quick handle
10
        CMP     r2, #DynArea_NewAreas
        BLO     %FT12
        CMP     r2, #DynArea_NewAreas+DynArea_NumQHandles
        BLO     %FT92                           ; can't choose your own quick handle
12
        BL      QCheckAreaNumber
  |
        BL      CheckAreaNumber                 ; check valid area number
  ]
        BCC     UnknownDyn                      ; [it's not]

        Push    "r1"
        MOV     r12, r10                        ; save pointer to node
        MOV     r1, r2
  [ DynArea_QuickHandles
        BL      QCheckAreaNumber                ; check area r2 doesn't already exist
  |
        BL      CheckAreaNumber                 ; check area r2 doesn't already exist
  ]
        Pull    "r1"
        BCS     %FT90                           ; [area r2 already exists]

        STR     r2, [r12, #DANode_Number]

; Now issue service to tell TaskManager

        Push    "r1-r3"
        MOV     r3, r2                          ; new number
        MOV     r2, r1                          ; old number
        MOV     r1, #Service_DynamicAreaRenumber
        BL      Issue_Service
        Pull    "r1-r3"

  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage                         ; we know system areas cannot be renumbered
        LDR     r11, [r11, #DynArea_ws]
        MOV     r10, #-1
        STR     r10, DynArea_CreatingHandle     ; invalidate these, just in case
        STR     r10, DynArea_LastTreacleHandle
        STR     r10, DynArea_LastEnumHandle
        LDR     lr, DynArea_OD6Signature
        STR     lr, DynArea_OD6PrevSignature
        ORR     lr, lr, #8
        STR     lr, DynArea_OD6Signature
        STR     r1, DynArea_OD6Handle
  ]

        CLRV
        EXIT

90
        ADRL    r0, ErrorBlock_AreaAlreadyExists
 [ International
        BL      TranslateError
 |
        SETV
 ]
        EXIT

;if you think this is worth internationalising, I pity you
92
        ADR     r0, DynArea_NaughtyRenum
        SETV
        EXIT
DynArea_NaughtyRenum
        DCD     0
        DCB     "illegal DA renumber",0
        ALIGN

 [ ShrinkableDAs
;**************************************************************************
;
;       DynArea_ReturnFree - Return total free space, including shrinkables
;
;       Internal routine called by DynamicAreaSWI
;
; in:   r0 = reason code (5)
;       r1 = area number to exclude, or -1 to include all shrinkable areas
;
; out:  r2 = total amount of free memory
;

DynArea_ReturnFree ALTENTRY
        CMP     r1, #-1                         ; if no excluded area,
        MOVEQ   r10, r1                         ; then point r10 nowhere
        BEQ     %FT10

  [ DynArea_QuickHandles
        BL      QCheckAreaNumber                ; else check area number is valid
  |
        BL      CheckAreaNumber                 ; else check area number is valid
  ]
        BCC     UnknownDyn                      ; [unknown area]
10
        LDR     r2, =ZeroPage
        LDR     r2, [r2, #FreePoolDANode + DANode_Size] ; start with current size of free pool
  [ DynArea_QuickHandles
        ;traverse the Shrinkable sublist
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        LDR     r11, DynArea_ShrinkableSubList
        B       %FT21
  |
        LDR     r11, =ZeroPage+DAList
  ]
20
  [ DynArea_QuickHandles
        LDR     r11, [r11, #DANode_SubLink]     ; load next area on sublist
  |
        LDR     r11, [r11, #DANode_Link]        ; load next area
  ]
21
        TEQ     r11, #0                         ; if end of list
        EXIT    EQ                              ; then exit, with r2 = correct value

  [ DynArea_QuickHandles
        TEQ     r11, r10                        ; must not be the excluded area
  |
        LDR     lr, [r11, #DANode_Flags]        ; load area flags
        TST     lr, #DynAreaFlags_Shrinkable    ; must be shrinkable
        TEQNE   r11, r10                        ; and not excluded area
  ]
        BEQ     %BT20                           ; [don't try this one]

        Push    r3
        BL      CallTestShrink
        ADD     r2, r2, r3                      ; add on amount if any
        Pull    r3
        B       %BT20                           ; then go back for more
 ]

;**************************************************************************
;
;       CheckAreaNumber - Try to find area with number r1
;
;       Internal routine called by DynArea_Create
;
; in:   r1 = area number to match
; out:  If match, then
;         C=1, r10 -> node, r11 -> previous node
;       else
;         C=0, r10,r11 corrupted
;       endif

CheckAreaNumber Entry
  [ DynArea_QuickHandles
QCheckAreaNumber_nonQ
  ]
        LDR     r10, =ZeroPage+DAList
        ASSERT  DANode_Link = 0                 ; because DAList has only link
10
        MOV     r11, r10                        ; save prev
        LDR     r10, [r10, #DANode_Link]        ; and load next
        CMP     r10, #1                         ; any more nodes?
        EXIT    CC                              ; no, then no match
        LDR     lr, [r10, #DANode_Number]       ; get number
        CMP     lr, r1                          ; does number match
        BNE     %BT10                           ; no, try next
  [ DynArea_QuickHandles
        Push    "r11"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        STR     r1,  DynArea_LastTreacleHandle
        STR     r10, DynArea_LastTreaclePtr
        Pull    "r11"
  ]
        EXIT                                    ; (C=1 from CMP lr,r1)

  [ DynArea_QuickHandles

; QCheckAreaNumber - similar to CheckAreaNumber, but blisteringly quick for system or for quick
;                    numbers. However, DOES NOT return previous node in r11.
;
QCheckAreaNumber ROUT
        Push    "lr"
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        CMP     r1, #-1
        BEQ     QCheckAreaNumber_nonQ           ;just to protect against -1 as a proposed number
        LDR     lr, DynArea_LastTreacleHandle
        CMP     lr, r1
        LDREQ   r10, DynArea_LastTreaclePtr
        EXIT    EQ                              ;found node is slow one we handled last time (carry set)
        LDR     lr, DynArea_CreatingHandle
        CMP     lr, r1
        LDREQ   r10, DynArea_CreatingPtr
        EXIT    EQ                              ;found node is one we're creating (carry set)
        CMP     r1, #ChangeDyn_MaxArea
        BLS     %FT10
        CMP     r1,#DynArea_NewAreas
        BLO     QCheckAreaNumber_nonQ
        SUB     lr, r1, #DynArea_NewAreas
        CMP     lr, #DynArea_NumQHandles
        BHS     QCheckAreaNumber_nonQ
;quick handle
        ADR     r10, DynArea_QHandleArray
        LDR     r10, [r10, lr, LSL #2]
        CMP     r10, #DynArea_NumQHandles
        MOVLS   r10, #0                         ;not a valid pointer
        CMP     r10, #1
        Pull    "pc"                            ;handle free, carry clear
                                                ;or word is ptr to node, carry set
;system handle
10
        ADR     r10, DynArea_SysQHandleArray
        LDR     r10, [r10, r1, LSL #2]
        CMP     r10, #1
        Pull    "pc"                            ;DA does not exist, carry clear
                                                ;or word is ptr to node, carry set
  ] ;DynArea_QuickHandles

;**************************************************************************
;
;       CheckForOverlappingAreas - Check that given area does not overlap any existing ones
;
;       Internal routine called by DynArea_Create
;
; in:   r3 = base address
;       r4 = area flags (NB if doubly mapped, then have to check both halves for overlap)
;       r5 = size (of each half in doubly mapped areas)
;
; out:  If this area overlaps with an existing one, then
;         r0 -> error
;         V=1
;       else
;         r0 preserved
;         V=0
;       endif
;

CheckForOverlappingAreas Entry "r0-r5"
        TST     r4, #DynAreaFlags_DoublyMapped          ; check if doubly mapped
        BEQ     %FT05                                   ; [not, so don't mangle]

        SUBS    r3, r3, r5                              ; move start address back
        BCC     %FT20                                   ; oh dear! - it went back to below 0
        MOVS    r5, r5, LSL #1                          ; and double size
        BCS     %FT20                                   ; if that wrapped then that's bad, too
05
        ADDS    r5, r5, r3                              ; r5 -> end +1
        BHI     %FT20                                   ; if CS, indicating wrap, and not EQ (ie just ending at 0), then bad

  [ HAL
        LDR     lr, =ZeroPage
        LDR     r0, [lr, #IOAllocPtr]
        CMP     r5, r0                                  ; end must be below I/O space (allocated down from high memory)
        BHI     %FT20
  ]

; check against list of fixed areas

        ADR     lr, FixedAreasTable
10
        LDMIA   lr!, {r0, r1}                           ; r0 = start addr, r1 = size
        CMP     r0, #-1                                 ; if at end of list
        BEQ     %FT30                                   ; then OK wrt fixed areas
        ADD     r1, r1, r0                              ; r1 = end addr+1
        CMP     r5, r0                                  ; if end of our area is <= start of fixed, then OK wrt fixed areas
        BLS     %FT30
        CMP     r3, r1                                  ; if start of our area is >= end of fixed, then go onto next area
        BCS     %BT10

20
        ADRL    r0, ErrorBlock_OverlappingAreas
 [ International
        BL      TranslateError
 |
        SETV
 ]
        STR     r0, [sp]
        EXIT

; Now, check against DAList

30
        LDR     lr, =ZeroPage+DAList
        ASSERT  DANode_Link = 0
40
        LDR     lr, [lr, #DANode_Link]
        CMP     lr, #0                                  ; if got to end of list (V=0)
        BEQ     %FT50                                   ; then exit saying OK
        LDR     r0, [lr, #DANode_Base]
        LDR     r1, [lr, #DANode_Flags]
        TST     r1, #DynAreaFlags_DoublyMapped
        LDR     r1, [lr, #DANode_MaxSize]
        SUBNE   r0, r0, r1                              ; if doubly mapped then move back
        MOVNE   r1, r1, LSL #1                          ; and double size
        ADD     r1, r1, r0                              ; r1 -> end
        CMP     r5, r0                                  ; if end of our area is <= start of dyn, then OK wrt dyn areas)
        BLS     %FT50
        CMP     r3, r1                                  ; if start of our area is >= end of dyn, then go onto next area
        BCS     %BT40
        B       %BT20                                   ; else it overlaps

50
        CLRV                                            ; OK exit
        EXIT


FixedAreasTable                                         ; table of fixed areas (address, size)
 [ HAL
        &       0,                      AplWorkMaxSize  ; application space
 [ CursorChunkAddress < IO
        &       CursorChunkAddress,     64*1024                 ; 32K for cursor, 32K for "nowhere"
 ]
 [ ROM < IO
 [ OSROM_ImageSize > 8192
        &       &03800000,              OSROM_ImageSize*1024   ; ROM
 |
        &       &03800000,              8*1024*1024            ; ROM
 ]
 ]
        &       IO,                     &FFFFFFFF-IO    ; Kernel workspace (code will also check dynamic value IOAllocPtr)
 |
        &       0,                      AplWorkMaxSize  ; application space
        &       UndStackSoftCamChunk,   1024*1024               ; undefined stack / soft cam map
        &       CursorChunkAddress,     1504*1024               ; cursor, Nowhere, cache cleaners, reserved (up to kernel buffers)
        &       L2PT,                   4*1024*1024             ; L2PT (and L1PT)
 [ OSROM_ImageSize > 8192
        &       &03000000,              8*1024*1024+OSROM_ImageSize*1024    ; I/O + ROM
 |
        &       &03000000,              16*1024*1024            ; I/O + ROM
 ]
        &       PhysSpace,              512*1024*1024   ; PhysSpace
 [ No26bitCode
        &       AbtStack,               AbtStackSize
 ]
 ] ; HAL
        &       -1,                     0               ; termination

;**************************************************************************
;
;       AllocateAreaAddress - Find an area of logical space to use for this area
;
;       Internal routine called by DynArea_Create
;
; in:   r4 = area flags (NB if doubly mapped, we have to find space for both halves)
;       r5 = size (of each half in doubly mapped areas)
;
; out:  If successfully found an address, then
;         r0 preserved
;         r3 = logical address
;         V=0
;       else
;         r0 -> error
;         r3 preserved
;         V=1
;       endif

AllocateAreaAddress Entry "r0-r2,r4-r7"
        TST     r4, #DynAreaFlags_DoublyMapped          ; check if doubly mapped
        BEQ     %FT05                                   ; [not, so don't mangle]
        MOVS    r5, r5, LSL #1                          ; double size
        BCS     %FT90                                   ; if that wrapped then that's bad
05
        LDR     r3, =DynArea_NewAreasBase               ; r3 is our current attempt
        ADR     r0, FixedAreasTable                     ; r0 is ptr into fixed areas table
        LDR     r1, =ZeroPage+DAList                             ; r1 is ptr into dyn areas list
10
        ADDS    r7, r3, r5                              ; r7 is our end+1
        BHI     %FT90                                   ; if we wrapped (but not end+1=0) then we failed
  [ HAL
        LDR     lr, =ZeroPage
        LDR     r2, [lr, #IOAllocPtr]
        CMP     r7, r2
        BHI     %FT90                                   ; if we walked into IOspace (assumed higher than any DA space) then we failed
  ]
15
        BL      GetNextRange                            ; get next range from either list (r2=start, r6=end+1)
        CMP     r7, r2                                  ; if end(ours) <= start(next) then this is OK
        BLS     %FT80                                   ; (note this also works when r2=-1)
        CMP     r3, r6                                  ; else if start(ours) >= end(next)
        BCS     %BT15                                   ; then get another
        MOV     r3, r6                                  ; else make start(ours) := end(next)
        B       %BT10                                   ; and go back for another try

; we've succeeded - just apply unbodge for doubly-mapped areas

80
        TST     r4, #DynAreaFlags_DoublyMapped          ; if doubly mapped
        MOVNE   r5, r5, LSR #1                          ; halve size again
        ADDNE   r3, r3, r5                              ; and advance base address to middle
        CLRV
        EXIT

90
        ADRL    r0, ErrorBlock_CantAllocateArea
  [ International
        BL      TranslateError
  |
        SETV
  ]
        STR     r0, [sp]
        EXIT                                    ; say we can't do it

        LTORG

;**************************************************************************
;
;       GetNextRange - Get next lowest range from either fixed or dynamic list
;
;       Internal routine called by AllocateAreaAddress
;
; in:   r0 -> next entry in fixed list
;       r1!0 -> next entry in dyn list
;
; out:  r2 = next lowest area base (-1 if none)
;       r6 = end of that range (undefined if none)
;       Either r0 or r1 updated to next one (except when r2=-1 on exit)
;

GetNextRange Entry "r7,r8"
        LDMIA   r0, {r2, r6}                            ; load start, size from fixed list
        ADD     r6, r6, r2                              ; r6 = end+1

        ASSERT  DANode_Link = 0
        LDR     r7, [r1, #DANode_Link]                  ; get next from dyn
        TEQ     r7, #0                                  ; if none
        MOVEQ   r8, #-1                                 ; then use addr -1
        BEQ     %FT10

        LDR     r8, [r7, #DANode_Flags]                 ; more double trouble
        TST     r8, #DynAreaFlags_DoublyMapped
        LDR     r8, [r7, #DANode_Base]
        LDR     lr, [r7, #DANode_MaxSize]
        SUBNE   r8, r8, lr
        MOVNE   lr, lr, LSL #1
        ADD     lr, lr, r8                              ; now r8 = start addr, lr = end+1
10
        CMP     r8, r2                                  ; if dyn one is earlier
        MOVCC   r2, r8                                  ; then use dyn start
        MOVCC   r6, lr                                  ; and end
        MOVCC   r1, r7                                  ; and advance dyn ptr
        EXIT    CC                                      ; then exit
        CMP     r2, #-1                                 ; else if not at end of fixed
        ADDNE   r0, r0, #8                              ; then advance fixed ptr
        EXIT

;**************************************************************************
;
;       AllocateBackingLevel2 - Allocate L2 pages for an area
;
;       Internal routine called by DynArea_Create
;
; in:   r3 = base address (will be page aligned)
;       r4 = area flags (NB if doubly mapped, then have to allocate for both halves)
;       r5 = size (of each half in doubly mapped areas)
;
; out:  If successfully allocated pages, then
;         All registers preserved
;         V=0
;       else
;         r0 -> error
;         V=1
;       endif

AllocateBackingLevel2 Entry "r0-r8,r11"
        TST     r4, #DynAreaFlags_DoublyMapped          ; if doubly mapped
        SUBNE   r3, r3, r5                              ; then area starts further back
        MOVNE   r5, r5, LSL #1                          ; and is twice the size

; NB no need to do sanity checks on addresses here, they've already been checked

; now round address range to 4M boundaries

        ADD     r5, r5, r3                              ; r5 -> end
        MOV     r0, #1 :SHL: 22
        SUB     r0, r0, #1
        BIC     r8, r3, r0                              ; round start address down (+ save for later)
        ADD     r5, r5, r0
        BIC     r5, r5, r0                              ; but round end address up

; first go through existing L2PT working out how much we need

        LDR     r7, =L2PT
        ADD     r3, r7, r8, LSR #10                     ; r3 -> start of L2PT for area
        ADD     r5, r7, r5, LSR #10                     ; r5 -> end of L2PT for area +1

        ADD     r1, r7, r3, LSR #10                     ; r1 -> L2PT for r3
        ADD     r2, r7, r5, LSR #10                     ; r2 -> L2PT for r5

        TEQ     r1, r2                                  ; if no pages needed
        BEQ     %FT30

        MOV     r4, #0                                  ; number of backing pages needed
10
        LDR     r6, [r1], #4                            ; get L2PT entry for L2PT
        TST     r6, #3                                  ; EQ if translation fault
        ADDEQ   r4, r4, #1                              ; if not there then 1 more page needed
        TEQ     r1, r2
        BNE     %BT10

; if no pages needed, then exit

        TEQ     r4, #0
        BEQ     %FT30

; now we need to claim r4 pages from the free pool, if possible; return error if not

        LDR     r1, =ZeroPage
        LDR     r6, [r1, #FreePoolDANode + DANode_Size]
        SUBS    r6, r6, r4, LSL #12                     ; reduce free pool size by that many pages
        BCS     %FT14                                   ; if enough, skip next bit

; not enough pages in free pool currently, so try to grow it by the required amount

        Push    "r0, r1"
        MOV     r0, #ChangeDyn_FreePool
        RSB     r1, r6, #0                              ; size change we want (+ve)
        SWI     XOS_ChangeDynamicArea
        Pull    "r0, r1"
        BVS     %FT90                                   ; didn't manage change, so report error

        MOV     r6, #0                                  ; will be no pages left in free pool after this
14
        STR     r6, [r1, #FreePoolDANode + DANode_Size] ; if possible then update size

; after that we need to zero all these pages out (=> cause translation fault for area initially)

        LDR     r0, [r1, #FreePoolDANode + DANode_Base] ; r0 -> base of free pool
        ADD     r0, r0, r6                              ; r0 -> first byte we're taking out of free pool
        ADD     r6, r0, r4, LSL #12                     ; r6 -> byte after last in free pool
        Push    r8                                      ; save original logical address
      [ ZeroPage <> 0
        MOV     r1, #0
      ]
        MOV     r8, #0                                  ; 0 => translation fault
        MOV     r11, #0
        MOV     lr, #0
15
        STMIA   r0!, {r1,r8,r11,lr}                     ; store data
        TEQ     r0, r6
        BNE     %BT15
        Pull    r8

; now r0 -> after end of free pool (log addr)

        LDR     lr, =L1PT
        ADD     r8, lr, r8, LSR #18                     ; point r8 at start of L1 we may be updating
        ADD     r1, r7, r3, LSR #10                     ; point r1 at L2PT for r3 again
        MOV     r11, #AP_L2PT                           ; access privs (+CB bits)
20
        LDR     r6, [r1], #4                            ; get L2PT entry again
        TST     r6, #3                                  ; if no fault
        BNE     %FT25                                   ; then skip

        SUB     r0, r0, #4096                           ; move free pointer back
        Push    "r2,r4,r5"
        BL      MoveCAMatR0toR3                         ; else move page from end of free pool to r3
        Pull    "r2,r4,r5"

        LDR     lr, =ZeroPage
        LDR     r6, [lr, #L2PTUsed]
        ADD     r6, r6, #4096
        STR     r6, [lr, #L2PTUsed]

; now update 4 words in L1PT (corresponding to 4M of address space which is covered by the 4K of L2)
; and point them at the physical page we've just allocated (r1!-4 will already hold physical address+bits now!)

        LDR     r6, [r1, #-4]                           ; r6 = physical address for L2 page + other L2 bits
        MOV     r6, r6, LSR #12                         ; r6 = phys.addr >> 12
 [ MEMM_Type = "VMSAv6"
        LDR     lr, =L1_Page
 |
  [ ECC
        LDR     lr, =L1_Page + L1_U + L1_P              ; form other bits to put in L1
  |
        LDR     lr, =L1_Page + L1_U                     ; form other bits to put in L1
  ]
 ]
        ORR     lr, lr, r6, LSL #12                     ; complete L1 entry
        STR     lr, [r8, #0]                            ; store entry for 1st MB
        ADD     lr, lr, #1024                           ; advance L2 pointer
        STR     lr, [r8, #4]                            ; store entry for 2nd MB
        ADD     lr, lr, #1024                           ; advance L2 pointer
        STR     lr, [r8, #8]                            ; store entry for 3rd MB
        ADD     lr, lr, #1024                           ; advance L2 pointer
        STR     lr, [r8, #12]                           ; store entry for 4th MB
        ;;;ARM_flush_TLB r6                junk TLB(s) shouldn't be needed, would have to be ARMop now
25
        ADD     r3, r3, #4096                           ; advance L2PT logical address
        ADD     r8, r8, #16                             ; move onto L1 for next 4M

        TEQ     r1, r2
        BNE     %BT20
30
        CLRV
        EXIT

; Come here if not enough space in free pool to allocate level2

90
        ADRL    r0, ErrorBlock_CantAllocateLevel2
  [ International
        BL      TranslateError
  |
        SETV
  ]
        STR     r0, [sp]
        EXIT

;**************************************************************************

  [ ChocolateSysHeap
;
; CreateChocolateBlockArray
;
; entry: r2 = No. of blocks to be created in array (N)
;        r3 = size of each block in bytes (S, must be multiple of 4)
;
; exit:
;        r2 = address of chocolate block array (parent SysHeap block address)
;        array is initialised to all blocks free
;   OR   V set, r0=error pointer, if error (from OS_Heap)
;
; - A Chocolate block array is only suitable for blocks of single fixed size.
;   These blocks may be allocated and freed in any order, but never resized.
; - Allocating and freeing blocks from a Chocolate block array is much faster
;   than OS_Heap, and the cost of operations is independent of N.
; - A Chocolate block array is a single block in the SysHeap, and looks like this
;   (excluding the internal structure of OS_Heap blocks):
;
;  - array header (3 words):
;    - word 0  =  total no. of blocks in array (N)
;    - word 1  =  size of each block container (S+4)
;    - word 2  -> first free block container in array, or 0 if none free
;  - followed immediately by N block containers, each of form:
;    - container header (1 word):
;      - word 0 :  bits  0..30 = container id (C)
;                                C = (S+4)*I, where I is array index, 0..N-1
;                  bit  31     = 1 if block is free, 0 if block is in use
;    - followed immediately by the S/4 words of the block itself
;      - if the block is in use, these words are as defined by the client
;      - if the block is free, the first word is a pointer to the next free
;        block container (or 0 if end of free list), and the other words
;        are undefined
;
; - A Chocolate block array requires a SysHeap block of 3*4 + N*(S + 4) bytes
;
CreateChocolateBlockArray ROUT
        Push    "r0,r1,r3,r4,r5,lr"
        MOV     r5,r2                ;N
        ADD     r4,r3,#4             ;S+4
        MUL     r3,r5,r4
        ADD     r3,r3,#3*4
        BL      ClaimSysHeapNode
        STRVS   r0,[SP]
        BVS     %FT50
        STR     r5,[r2]
        STR     r4,[r2,#4]
        ADD     r1,r2,#3*4
        STR     r1,[r2,#8]
        MOV     lr,r5
        ADD     r0,r2,#3*4
        MOV     r1,#&80000000        ;free flag
10
        STR     r1,[r0]
        ADD     r3,r0,r4
        STR     r3,[r0,#4]
        ADD     r1,r1,r4
        SUBS    lr,lr,#1
        MOVNE   r0,r3
        BNE     %BT10
        MOV     r1,#0
        STR     r1,[r0,#4]           ;end of free list
50
        Pull    "r0,r1,r3,r4,r5,pc"

;
; ClaimChocolateBlock
;
; entry: r3 = address of parent ChocolateBlockArray (must be valid)
; exit:  r2 = address of allocated block
;        r3 = size of block
;  OR    V set, R0=error (no free blocks)
;
ClaimChocolateBlock ROUT
        Push    "r1,r4,lr"
        MRS     r4,CPSR
        ORR     r1,r4,#I32_bit
        MSR     CPSR_c,r1         ;protect critical manipulation from interrupt re-entry
        LDR     r2,[r3,#8]        ;pick up block container at front of free list
        CMP     r2,#0
        BEQ     ClaimChocolateBlock_NoneFree
        LDR     r1,[r2]
        BIC     r1,r1,#&80000000  ;clear the free flag
        STR     r1,[r2]
        LDR     r1,[r2,#4]        ;next free block container
        STR     r1,[r3,#8]        ;put it at front
        ADD     r2,r2,#4          ;address of block
        LDR     r3,[r3,#4]
        SUB     r3,r3,#4          ;size of block
        BIC     r4,r4,#V_bit      ;return with V clear
        MSR     CPSR_cf,r4        ;restore IRQ state
        Pull    "r1,r4,pc"
;
;DON'T even think about internationalisation - this exit route must be fast
ClaimChocolateBlock_NoneFree
        ADR     R0,ChocolateBlock_NFError
        ORR     r4,r4,#V_bit      ;return with V set
        MSR     CPSR_cf,r4        ;restore IRQ state
        Pull    "r1,r4,pc"

;
; FreeChocolateBlock
;
; entry: r1 = address of parent ChocolateBlockArray (must be valid)
;        r2 = address of block to free (may be invalid)
; exit:  -
;   OR   V set, R0=error (not a ChocolateBlock), r1,r2 still preserved
;
FreeChocolateBlock ROUT
        Push    "r2,r3,r4,lr"
        MRS     r4,CPSR
        ORR     r3,r4,#I32_bit
        MSR     CPSR_c,r3         ;protect critical manipulation from interrupt re-entry
        ADD     r3,r1,#12         ;r3 -> first block container
        SUB     r2,r2,#4          ;r2 -> container for block (if valid)
        CMP     r2,r3
        BLO     FreeChocolateBlock_NaffOff
        LDR     lr,[r1,#-4]       ;OS_Heap's size word (naughty!)
        ADD     lr,lr,r1
        CMP     r2,lr
        BHS     FreeChocolateBlock_NaffOff
        LDR     lr,[r2]           ;block container id
        TST     lr,#&80000000     ;free flag
        BNE     FreeChocolateBlock_NaffOff
        ADD     lr,lr,r3          ;lr := address of block container, from container id
        CMP     lr,r2
        BNE     FreeChocolateBlock_NaffOff
;
;we now believe caller is freeing a valid block, currently in use
;
        LDR     lr,[r2]
        ORR     lr,lr,#&80000000
        STR     lr,[r2]           ;set free flag in container id
        LDR     lr,[r1,#8]        ;current front of free list
        STR     lr,[r2,#4]        ;chain free list to block container we are freeing
        STR     r2,[r1,#8]        ;put freed block container at front
        BIC     r4,r4,#V_bit      ;return with V clear
        MSR     CPSR_cf,r4        ;restore IRQ state
        Pull    "r2,r3,r4,pc"
;
;DON'T even think about internationalisation - this exit route must be fast
FreeChocolateBlock_NaffOff
        ADR     R0,ChocolateBlock_NOError
        ORR     r4,r4,#V_bit      ;return with V set
        MSR     CPSR_cf,r4        ;restore IRQ state
        Pull    "r2,r3,r4,pc"

;
;forget internationalisation - if these errors aren't dealt with silently,
;                              the kernel's stuffed anyway
ChocolateBlock_NFError
        DCD     0
        DCB     "Chocolate SysHeap claim failed",0
        ALIGN
ChocolateBlock_NOError
        DCD     0
        DCB     "not a Chocolate SysHeap block",0
        ALIGN

  ] ;ChocolateSysHeap

;**************************************************************************
;
;       InitDynamicAreas - Initialise nodes for dynamic areas
;
;       It only initialises free pool, appspace and sysheap nodes
;       The other areas are created properly, after the screen area has been created (improperly)
;
; in:   -
; out:  -
;

InitDynamicAreas Entry "r0-r12"
        LDR     lr, =ZeroPage+AppSpaceDANode
        ADR     r0, InitAppSpaceTable
        LDMIA   r0, {r0-r8}
        STMIA   lr, {r0-r8}

        LDR     lr, =ZeroPage+FreePoolDANode
        ADR     r0, InitFreePoolTable
        LDMIA   r0, {r0-r8}                     ; copy initial data into node
        LDR     r5, [lr, #RAMLIMIT-FreePoolDANode] ; max size is RAMLIMIT
        STMIA   lr, {r0-r8}


; We have to move all free pages (ie ones not occupied by the static pages)
; into the free pool.
; By default, pages will get taken from the end of the free pool when other
; dynamic areas are initialised or grown. So make sure that the slowest RAM
; is at the start of the free pool and the fastest is at the end; this is the
; reverse of the order in PhysRamTable.

; The blocks of pages within the free pool are kept with consecutive physical
; page numbers; I'm not sure how important this is, but the old code did it.
; However instead of merely keeping the entire free pool in consecutive order,
; we need to process each PhysRamTable entry in turn, to allow us to place the
; fastest block at the end of the pool. Furthermore VRAM block is kept at the
; start of the pool - again to match old behaviour, although moving it elsewhere
; may not have any significant impact on the system

        MOV     r11, r3                         ; r11 = PPL (inc CB) for free pool
        MOV     r6, r2                          ; r6 = base address of free pool, ie where to put stuff
        LDR     r5, =ZeroPage
        LDR     r0, [r5, #InitUsedStart]
        ADD     r0, r0, #DRAMOffset_FirstFixed - DRAMOffset_L1PT
        BL      PhysAddrToPageNo
        MOV     r7, r0                          ; r7 = page number of start of static chunk
        LDR     r0, [r5, #InitUsedEnd]
        BL      PhysAddrToPageNo
        SUB     r8, r0, #1                      ; r8 = page number of last page in statics

        ADD     r9, r5, #PhysRamTable
        LDMIA   r9, {r0, r10}                   ; get VRAM info
        ADD     r9, r9, #PhysRamTableEnd-PhysRamTable ; skip to end
        MOV     r10, r10, LSR #12
        LDR     r5, [r5, #CamEntriesPointer]
        ADD     r5, r5, #4                      ; r5 = base of PPLs
10
        BL      PhysAddrToPageNo
        ; Move r10 pages to r6 starting from r0
        MOV     r2, r0                          ; get ready for BangCamUpdate
        MOV     r3, r6
15
        CMP     r2, r7
        CMPHS   r8, r2
        BHS     %FT20                           ; page is in statics
        ; Check the CAM map to see if the page is already taken - this will detect the DMA regions, which aren't included in InitUsedStart/InitUsedEnd
        LDR     lr, [r5, r2, LSL #3]
        TST     lr, #PageFlags_Unavailable
        BNE     %FT20
        BL      BangCamUpdate
        ADD     r3, r3, #4096
20
        ADD     r2, r2, #1
        SUBS    r10, r10, #1
        BNE     %BT15
        ; Advance to next PhysRamTable entry, working backwards
30
        LDMDB   r9!, {r0, r10}
        MOVS    r10, r10, LSR #12
        BEQ     %BT30
        LDR     lr, =ZeroPage+PhysRamTable
        CMP     lr, r9                          ; stop once we hit first entry, it's already been processed
        MOV     r6, r3
        BNE     %BT10
        ; Left with r6 = end of free pool
        LDR     lr, =ZeroPage+FreePoolDANode
        LDR     r5, [lr, #DANode_Base]
        SUB     r5, r6, r5
        STR     r5, [lr, #DANode_Size]

; Now initialise the system heap by hand, so we can start creating dynamic areas

        LDR     r0, =SysHeapStart
        LDR     r1, =magic_heap_descriptor
        MOV     r2, #Nil
        MOV     r3, #hpdsize
        MOV     r4, #32*1024 - (SysHeapStart-SysHeapChunkAddress)
        STMIA   r0, {r1-r4}

        LDR     r0, =ZeroPage                   ; initialise module list to empty
      [ ZeroPage = 0
        STR     r0, [r0, #Module_List]
      |
        MOV     lr, #0
        STR     lr, [r0, #Module_List]
      ]

        LDR     lr, =ZeroPage+SysHeapDANode     ; initialise system heap node
        ADR     r0, InitSysHeapTable
        LDMIA   r0, {r0-r8}
        STMIA   lr, {r0-r8}
        LDR     r0, =ZeroPage
 [ FreePoolAddress < SysHeapStart
        ADD     lr, r0, #FreePoolDANode             ; cf comments above/below - what was old code? KJB
 ]
        STR     lr, [r0, #DAList]               ; store pointer to 1st node on list (either free pool or sys heap)

  [ ChocolateSysHeap
        ASSERT  ChocolateCBBlocks = ChocolateBlockArrays +  0
        ASSERT  ChocolateSVBlocks = ChocolateBlockArrays +  4
        ASSERT  ChocolateTKBlocks = ChocolateBlockArrays +  8
        ASSERT  ChocolateMRBlocks = ChocolateBlockArrays + 12
        ASSERT  ChocolateMABlocks = ChocolateBlockArrays + 16
        ASSERT  ChocolateMSBlocks = ChocolateBlockArrays + 20
        LDR     r1,=ZeroPage+ChocolateBlockArrays
        MOV     r2,#MaxChocolateCBBlocks
        MOV     r3,#3*4
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#0]
        MOV     r2,#MaxChocolateSVBlocks
        MOV     r3,#VecNodeSize
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#4]
        MOV     r2,#MaxChocolateTKBlocks
        MOV     r3,#TickNodeSize
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#8]
        MOV     r2,#MaxChocolateMRBlocks
        MOV     r3,#ROMModule_NodeSize
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#12]
        MOV     r2,#MaxChocolateMABlocks
        MOV     r3,#ModInfo + Incarnation_Postfix + 8
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#16]
        MOV     r2,#MaxChocolateMSBlocks
        MOV     r3,#ModSWINode_Size
        BL      CreateChocolateBlockArray       ; better not fail
        STR     r2,[r1,#20]

  ]

  [ Oscli_HashedCommands
        MOV     r3,#4*(Oscli_MHashValMask+1)
        BL      ClaimSysHeapNode                ; better not fail
        LDR     r0,=ZeroPage
      [ ZeroPage = 0
        STR     r0,[r0,#Oscli_CmdHashSum]
      |
        MOV     r3,#0
        STR     r3,[r0,#Oscli_CmdHashSum]
      ]
        STR     r2,[r0,#Oscli_CmdHashLists]
        MOV     r3,#Oscli_MHashValMask+1
      [ ZeroPage <> 0
        MOV     r0, #0
      ]
DynArea_OHinit_loop
        STR     r0,[r2],#4
        SUBS    r3,r3,#1
        BNE     DynArea_OHinit_loop
  ]

  [ DynArea_QuickHandles

        LDR     r3, =DynArea_ws_size
        BL      ClaimSysHeapNode                    ; should not give error - kernel boot
        LDR     r0, =ZeroPage
        STR     r2, [r0, #DynArea_ws]
        MOV     r11, r2
        LDR     r3, =DynArea_ws_size
        ADD     r3, r3, r2
      [ ZeroPage <> 0
        MOV     r0, #0
      ]
DynArea_QHinit_loop1
        STR     r0, [r2], #4
        CMP     r2, r3
        BLO     DynArea_QHinit_loop1

        MOV     r1, #-1
        STR     r1, DynArea_CreatingHandle
        STR     r1, DynArea_LastTreacleHandle
        STR     r1, DynArea_LastEnumHandle
        STR     r1, DynArea_OD8Clamp1
        STR     r1, DynArea_OD8Clamp2
        MOV     r1, #&1000
        RSB     r1, r1, #0
        STR     r1, DynArea_OD8Clamp3               ; 4G - 4k

        ADR     r1, DynArea_QHandleArray            ; init all Qhandles as free, free list = 1..DynArea_NumQHandles
        MOV     r2, #1
        STR     r2, DynArea_FreeQHandles
DynArea_QHinit_loop2
        ADD     r2, r2, #1
        STR     r2, [r1], #4
        CMP     r2, #DynArea_NumQHandles
        BLO     DynArea_QHinit_loop2
        MOV     r2, #0
        STR     r2, [r1]                            ; 0 = end of free list

        MOV     r1, #DynArea_NewAreas-1
        ADD     r1, r1, #DynArea_NumQHandles        ; first non-quick DA number -1
        STR     r1, DynArea_TreacleGuess

        LDR     r1, =ZeroPage+FreePoolDANode
        STR     r1, DynArea_SortedList              ; initially, FreePool at front of sorted list,
        LDR     r2, =ZeroPage+SysHeapDANode
        STR     r2, [r1, #DANode_SortLink]          ; and SysHeap second...
        MOV     r1, #0
        STR     R1, [r2, #DANode_SortLink]          ; ...and last

        ADR     r1, DynArea_SysQHandleArray
        LDR     r2, =ZeroPage+SysHeapDANode
        STR     r2, [r1, #ChangeDyn_SysHeap:SHL:2]
        LDR     r2, =ZeroPage+FreePoolDANode
        STR     r2, [r1, #ChangeDyn_FreePool:SHL:2]

; Initialise the address lookup table for the current DA's
; Assumes we have at least one DA to start with!
        LDR     r2, =ZeroPage+DAList
        LDR     r2, [r2]
DynArea_AddrLookup_loop
        BL      AddDAToAddrLookupTable
        LDR     r2, [r2, #DANode_Link]
        TEQ     r2, #0
        BNE     DynArea_AddrLookup_loop

  |
        ASSERT  ZeroPage = 0
        MOV     r0, #0
        STR     r0, [r0, #DynArea_ws]

  ] ;DynArea_QuickHandles

        LDR     r0, =ZeroPage
      [ ZeroPage = 0
        STR     r0, [r0, #CDASemaphore]         ; clear CDASemaphore
      |
        MOV     r2, #0
        STR     r2, [r0, #CDASemaphore]         ; clear CDASemaphore
      ]

        EXIT

        LTORG

InitFreePoolTable
 [ FreePoolAddress > SysHeapStart
        &       0                               ; link: no more nodes on list
 |
        &       ZeroPage+SysHeapDANode
 ]
        &       ChangeDyn_FreePool
; [ HAL32
;        ! 0, "Sort out FreePoolInitTable"
;        &       -1
; |
        &       FreePoolAddress
; ]
        &       AP_FreePool
        &       0                               ; size will be updated later
        &       0                               ; max size is computed
        &       0                               ; no workspace needed
        &       0                               ; no handler needed
        &       FreePoolString                  ; title

InitSysHeapTable
 [ FreePoolAddress > SysHeapStart
        &       ZeroPage+FreePoolDANode         ; link -> free pool node, since FreePoolAddress > SysHeapStart
 |
        &       0
 ]
        &       ChangeDyn_SysHeap
        &       SysHeapStart
        &       AP_SysHeap
        &       32*1024-(SysHeapStart-SysHeapChunkAddress) ; size
        &       SysHeapMaxSize
        &       SysHeapStart                    ; workspace pointer -> base of heap
        &       DynAreaHandler_SysHeap          ; area handler
        &       SysHeapString                   ; title

InitAppSpaceTable
        &       0                               ; link: not on list
        &       ChangeDyn_AplSpace
        &       0                               ; base address
        &       AP_AppSpace
        &       0                               ; size will be set up later
        &       AplWorkMaxSize
        &       0                               ; no workspace needed
        &       0                               ; no handler needed
        &       AppSpaceString                  ; title

FreePoolString
        =       "Free pool", 0
AppSpaceString
        =       "Application space", 0
SysHeapString
        =       "System heap", 0
        ALIGN

;**************************************************************************
;
;       ChangeDynamicSWI - implement OS_ChangeDynamicArea (change the
;                          size of a dynamic area)
;
; in:   r0 = area number
;       r1 = size of change (in bytes, signed integer)
;
; out:  r0   preserved
;       r1 = actual amount moved (in bytes, unsigned integer)
;

  [ DA_Batman
;OR, a special call is allowed for internal use:
;
; in:   r0 = ChangeDyn_Batman (-3)
;       r1 = size of change (in bytes, signed integer)
;       r2 -> pseudo DANode for this call - base of DA will be base of fragment to map/unmap,
;             magnitude of r1 will give size of fragment, sign of r1 is +ve for map -ve for unmap
  ]

ChangeDynamicSWI ROUT
        Push    "r0, r2-r9, r10, lr"

        FastCDA_ProfInit r3

        LDR     r10, =ZeroPage                  ; check we're not in an IRQ
        LDR     lr, [r10, #IRQsema]
        TEQ     lr, #0
        LDREQ   lr, [r10, #CDASemaphore]       ; now also check whether ChangeDynamicArea is already threaded
        TEQEQ   lr, #0
        LDREQB  lr, [r10, #VRAMRescue_control] ; also check that wimp has not locked Free Pool
        TSTEQ   lr, #VRRc_wimp_lock
        BNE     failure_IRQgoing
        STR     pc, [r10, #CDASemaphore]     ; store non-zero value in CDASemaphore, to indicate we're threaded

 [ DebugCDA2
        DLINE   "Entering OS_ChangeDynamicArea (new code)"
 ]

  [ DA_Batman
    ;check for special Batman call (which uses OS_ChangeDynamicArea to map or unmap a fragment of a sparse DA)
        CMP     r0, #ChangeDyn_Batcall
        MOVEQ   r10, r2                         ; Batman call passes a pseudo DANode in r2
        BEQ     CDA_handlechecked
  ]

        Push    "r1"
        MOV     r1, r0
 [ DebugCDA2
        DREG    r1, "Checking list for area number "
 ]

  [ DynArea_QuickHandles
        BL      QCheckAreaNumber                ; check area number is on list
  |
        BL      CheckAreaNumber                 ; check area number is on list
  ]

        Pull    "r1"
        BCC     failure_IRQgoingClearSemaphore

 [ DebugCDA2
        DLINE   "Found entry on list"
 ]

  [ DA_Batman
        ;a sparse area is not allowed to do an ordinary grow or shrink
        ;
        LDR     r11, [r10, #DANode_Flags]
        TST     r11, #DynAreaFlags_SparseMap
        BNE     failure_IRQgoingClearSemaphore
  ]

CDA_handlechecked

  [ DynArea_QuickHandles
        LDR     r11, =ZeroPage
        LDR     r11, [r11, #DynArea_ws]
        LDR     r5, DynArea_OD6Signature
        CMP     r0, #ChangeDyn_MaxArea
        BLS     daq_cda_od6done
        CMP     r0, #&FFFFFFF0                  ;don't count special DA numbers, such as ChangeDyn_AplSpace
        BHI     daq_cda_od6done
        TST     r5, #&80000000                  ;if set, disables resize signature for this call
        STREQ   r5, DynArea_OD6PrevSignature
        STREQ   r0, DynArea_OD6Handle
        ORREQ   r5, r5, #4
daq_cda_od6done
        BIC     r5, r5, #&80000000              ;clear any disable
        STR     r5, DynArea_OD6Signature
  ]

        LDR     r5, =ZeroPage
        LDR     r5, [r5, #Page_Size]            ; r5 = page size throughout
        SUB     r12, r5, #1                     ; r12 = page mask
        ADD     r1, r1, r12
        BICS    r1, r1, r12
        BEQ     IssueServiceMemoryMoved         ; zero pages! (r0 = area number, r1 = size change (0))
        BPL     AreaGrow

AreaShrink ROUT
        RSB     r1, r1, #0                      ; make size change positive
 [ DebugCDA2
        DREG    r0, "Shrinking area ", cc
        DREG    r1, " by "
 ]
        MOV     r11, r10                        ; source is area
        CMP     r0, #ChangeDyn_FreePool         ; if source is free pool
        ADREQ   r12, AppSpaceDANode             ; then dest is appspace
        ADRNE   r12, FreePoolDANode             ; else dest is free pool
      [ ZeroPage <> 0
        LDR     r2, =ZeroPage
        ADD     r12, r12, r2
      ]

        ASSERT  DANode_MaxSize = DANode_Size +4
        ADD     r2, r12, #DANode_Size
        LDMIA   r2, {r2, r3}
        SUB     lr, r3, r2                      ; lr = amount dest could grow

 [ ShrinkableDAs
        CMP     r1, lr
        MOVHI   r1, lr                          ; r1 = the most we want to move if we could
        BLHI    GenNotAllMovedError             ; but if not all we still want error
        SUB     lr, r5, #1                      ; lr = pagesize mask
        BICS    r1, r1, lr                      ; a pagesize multiple
        BEQ     IssueServiceMemoryMoved
 ]

 [ ShrinkableDAs
        LDR     r2, [r11, #DANode_Size]         ; amount src could shrink
        CMP     r2, r1
        BLCC    TryToShrinkShrinkables
        BCS     %FT15                           ; [we can now do it all]

; we can't move all that is required, so move smaller amount

        MOV     r1, r2                          ; move smaller amount
 |
        LDR     r2, [r11, #DANode_Size]         ; amount src could shrink
        CMP     r2, lr
        MOVCC   lr, r2                          ; lr = min(amount dest could grow, amount src could shrink)

        CMP     r1, lr
        BLS     %FT15

; we can't move all that is required, so move smaller amount

        MOV     r1, lr                          ; move smaller amount
 ]
        BL      GenNotAllMovedError
        SUB     lr, r5, #1                      ; lr = pagesize mask
        BICS    r1, r1, lr                      ; a pagesize multiple
        BEQ     IssueServiceMemoryMoved
15
      [ ZeroPage = 0
        CMP     r11, #AppSpaceDANode            ; if src <> appspace
        CMPNE   r12, #AppSpaceDANode            ; and dst <> appspace
      |
        LDR     lr, =ZeroPage+AppSpaceDANode
        CMP     r11, lr                         ; if src <> appspace
        CMPNE   r12, lr                         ; and dst <> appspace
      ]
        BNE     %FT17                           ; then don't call app
        Push    "r10"                           ; save -> to area we tried to shrink
        MOV     r10, r1
        BL      CheckAppSpace
        Pull    "r10"
        BVS     ChangeDynError
17
        BL      CallPreShrink
        BVS     ChangeDynError                  ; (r10 still points to area we tried to shrink)
        CMP     r2, r1                          ; can we move as much as we wanted?
        MOVCS   r2, r1                          ; if not, then move lesser amount (r2 = amount we're moving)
        BLCC    GenNotAllMovedError             ; store error, but continue

        TEQ     r2, #0                          ; if can't move any pages
        BEQ     NoMemoryMoved                   ; then exit, issuing Service_MemoryMoved

; Now move pages starting from end of area

        LDR     r0, [r11, #DANode_Base]
        LDR     r3, [r11, #DANode_Size]
        LDR     r6, [r11, #DANode_Flags]        ; r6 = src flags
        Push    "r3, r6"                        ; save src old size, src flags for later
        TST     r6, #DynAreaFlags_DoublyMapped  ; if src is doubly mapped
        MOVNE   r9, r3                          ; then set up offset from 1st copy to 2nd copy = old src size
        ADD     r0, r0, r3                      ; move r0 to point to after end of area (2nd copy)
        SUB     r3, r3, r2
        STR     r3, [r11, #DANode_Size]         ; store reduced source size

        LDR     r1, [r12, #DANode_Base]         ; this is free pool or app space, so it can't be doubly mapped!
        LDR     r3, [r12, #DANode_Size]
        ADD     r1, r1, r3                      ; r1 -> address of 1st extra page

      [ FastCDA_UpFront
        Push    "r0-r1"
        BL      CheckCacheabilityR0ByMinusR2
        LDR     r4, [r11, #DANode_Flags]
        ADR     lr, %FT19
        TST     r4, #DynAreaFlags_DoublyMapped
        LDR     r4, =ZeroPage
        BNE     %FT18
        ; Interacting with singly-mapped region - use regular logic
        TST     r6, #DynAreaFlags_NotCacheable
        MOV     r1, r2, LSR #12
        ARMop   MMU_ChangingEntries, EQ, tailcall, r4
        ARMop   MMU_ChangingUncachedEntries, NE, tailcall, r4
18
        ; Interacting with doubly-mapped region - use sledgehammer logic
        TST     r6, #DynAreaFlags_NotCacheable
        ARMop   MMU_Changing, EQ, tailcall, r4
        ARMop   MMU_ChangingUncached, NE, tailcall, r4
19
        Pull    "r0-r1"
      ]

        LDR     lr, =DynAreaFlags_AccessMask
        MOV     r4, r2
        LDR     r6, [r12, #DANode_Flags]        ; r6 = dst flags
        AND     r6, r6, lr
      [ FastCDA_UpFront
        ORR     r6, r6, #PageFlags_Unsafe
      ]
20
        SUB     r0, r0, r5                      ; pre-decrement source pointer
 [ DebugCDA2
        DREG    r0, "Moving page at ", cc
        DREG    r1, " to ", cc
        DREG    r6, " with PPL "
 ]
        BL      MovePageAtR0ToR1WithAccessR6
        ADD     r1, r1, r5
        SUBS    r4, r4, r5
        BNE     %BT20

        ADD     r3, r3, r2
        STR     r3, [r12, #DANode_Size]         ; store increased destination size
      [ ZeroPage = 0
        EORS    lr, r12, #AppSpaceDANode        ; check if dest = appspace (if so lr:=0)
        STREQ   r3, [lr, #MemLimit]             ; update memlimit if so
      |
        LDR     lr, =ZeroPage+AppSpaceDANode
        TEQ     r12, lr                         ; check if dest = appspace
        STREQ   r3, [lr, #MemLimit-AppSpaceDANode] ; update memlimit if so
      ]

        Pull    "r3, r6"                        ; restore src old size, src flags
        TST     r6, #DynAreaFlags_DoublyMapped  ; if src doubly mapped
        SUBNES  r4, r3, r2                      ; then set r4 = number of pages to shuffle up
        BEQ     %FT30                           ; [not doubly mapped, or no pages left, so skip]

        SUB     r0, r0, r3                      ; move r0 back to end of 1st copy of pages remaining
        ADD     r1, r0, r2                      ; r1 is end of where they're moving to (should be src base address!)
 [ 1 = 1
 |
        AND     r6, r6, #DynAreaFlags_AccessMask
 ]
        MOV     r9, #0                          ; no funny stuff while moving these pages
25
        SUB     r0, r0, r5
        SUB     r1, r1, r5
 [ 1 = 1
        BL      GetPageFlagsForR0IntoR6
 ]
 [ FastCDA_UpFront
        ORR     r6, r6, #PageFlags_Unsafe
 ]
        BL      MovePageAtR0ToR1WithAccessR6
        SUBS    r4, r4, r5
        BNE     %BT25

30
  [ EarlierReentrancyInDAShrink
        LDR     r4, =ZeroPage                   ; indicate no page block (and ptr to semaphore)
      [ ZeroPage = 0
        STR     r4, [r4, #CDASemaphore]         ; OK to reenter now (we've done the damage)
      |
        MOV     lr, #0
        STR     lr, [r4, #CDASemaphore]
      ]
  ]
        BL      CallPostShrink
        RSB     r1, r2, #0
        LDR     r0, [r11, #DANode_Number]       ; reload dynamic area number
        B       IssueServiceMemoryMoved

AreaGrow ROUT
 [ DebugCDA2
        DREG    r0, "Growing area ", cc
        DREG    r1, " by "
 ]
        MOV     r12, r10                        ; dest is area specified
        CMP     r0, #ChangeDyn_FreePool         ; if dest is free pool
        ADREQ   r11, AppSpaceDANode             ; then src is appspace
        ADRNE   r11, FreePoolDANode             ; else src is free pool (may later be free+apl)
      [ ZeroPage <> 0
        LDR     r2, =ZeroPage
        ADD     r11, r11, r2
      ]

        ASSERT  DANode_MaxSize = DANode_Size +4
        ADD     r2, r12, #DANode_Size
        LDMIA   r2, {r2, r3}
        SUB     lr, r3, r2                      ; lr = amount dest could grow

 [ DebugCDA2
        DREG    lr, "Dest could grow by "
 ]
      [ ZeroPage = 0
        LDR     r2, [r11, #DANode_Size]         ; amount src could shrink
        CMP     r11, #AppSpaceDANode            ; if appspace
      |
        LDR     r2, =ZeroPage+AppSpaceDANode
        CMP     r11, r2                         ; if appspace
        LDR     r2, [r11, #DANode_Size]         ; amount src could shrink
      ]
        SUBEQ   r2, r2, #&8000                  ; then can't take away last 32K (0..&7FFF)

 [ DebugCDA2
        DREG    r2, "Src could shrink by "
 ]

        CMP     r1, lr                          ; if enough room in dest
        CMPLS   r1, r2                          ; and enough space in src
        MOVLS   r3, r1                          ; then can do full amount
        BLS     %FT65                           ; so skip this bit

; we can't move all that is required
;
; if src = AplSpace then
;       (dest must be free pool)
;       move reduced amount
; else
;       (src must be free pool)
;       (dest <> AplSpace, cos that's a shrink!)
;       so check if adding aplspace would allow us to succeed
;       if it does then adjust registers, else give error
; endif
;

 [ DebugCDA2
        DLINE   "Can't move all required using just free pool"
 ]
      [ ZeroPage = 0
        CMP     r11, #AppSpaceDANode
      |
        Push    "lr"
        LDR     lr, =ZeroPage+AppSpaceDANode
        CMP     r11, lr
        Pull    "lr"
      ]
        BNE     %FT62
        MOV     r1, lr
        CMP     r1, r2
        MOVHI   r1, r2                          ; move min(max addable to dest, max removable from src)

 [ DebugCDA2
        DREG    r1, "Dest is free pool, moving reduced amount of "
 ]

61
        BL      GenNotAllMovedError
        SUB     lr, r5, #1                      ; lr = pagesize mask
        BICS    r1, r1, lr                      ; a pagesize multiple
        BEQ     IssueServiceMemoryMoved
        MOV     r3, r1
        B       %FT65

62

 [ ShrinkableDAs
; growing another area from free pool
; insert code here to check for shrinking shrinkable areas

        CMP     r1, lr                          ; if dest can't grow by this amount,
        BHI     %FT64                           ; we're definitely not doing anything

        CMP     r2, r1                          ; this should definitely set C=0 as required by TryToShrinkShrinkables
        Push    "lr"
        BLCC    TryToShrinkShrinkables
        Pull    "lr"
        MOVCS   r3, r1                          ; if succeeded set r3 to number of bytes to do
        BCS     %FT65                           ; and do it
64

; end of inserted code
 ]

        LDR     r4, =ZeroPage+AppSpaceDANode
        LDR     r6, [r4, #DANode_Size]          ; get current size of apl space
        SUB     r6, r6, #&8000                  ; can't take away 0-&7FFF
        ADD     r3, r2, r6                      ; add on to amount we could remove from free pool

 [ DebugCDA2
        DREG    r6, "Can get from app space an additional ", cc
        DREG    r3, " making a total of "
 ]

        CMP     r1, lr                          ; if not enough room in dest
        CMPLS   r1, r3                          ; or src still doesn't have enough
        MOVHI   r1, #0                          ; then don't move any
        BHI     %BT61                           ; and return error

        MOV     r3, r1                          ; amount actually doing

        TEQ     r2, #0                          ; else check to see if there was any at all in free pool
        LDREQ   r11, =ZeroPage+AppSpaceDANode   ; if not, then just take from aplspace
        MOVEQ   r7, r3                          ; and do all

        MOVNE   r11, #0                         ; else make src indicator reflect that we need both
        MOVNE   r7, r2                          ; but save amount we are taking from freepool

65

        Push    "r10"
      [ ZeroPage = 0
        CMP     r11, #AppSpaceDANode            ; if source = aplspace
      |
        LDR     r10, =ZeroPage+AppSpaceDANode
        CMP     r11, r10                        ; if source = aplspace
      ]
        MOV     r10, #0                         ; default value if apl space not involved
        RSBEQ   r10, r3, #0                     ; then make amount -ve
        CMP     r11, #0                         ; if source = free and apl
        SUBEQ   r10, r7, r3                     ; then make it -(amount removing from apl space)
        MOVNE   r7, r3                          ; else set up r7 to be total amount (wasn't set up above)

 [ DebugCDA2
        DREG    r3, "Amount actually moving into area = "
        DREG    r7, "Amount coming from 1st src area = "
 ]

        CMP     r10, #0                         ; if neither of the above then don't talk to app (CMP clears V)
        BLNE    CheckAppSpace                   ; else check app agrees
        Pull    "r10"
        BVS     ChangeDynError

; now split up grow into bite-size chunks, and call DoTheGrow to do each one

        Push    "r3"                            ; save original total amount
        TEQ     r11, #0                         ; if taking from both free + apl
        LDREQ   r11, =ZeroPage+FreePoolDANode   ; then start with free

        LDR     lr, [r12, #DANode_Flags]        ; could this area require particular physical pages at all?
        TST     lr, #DynAreaFlags_NeedsSpecificPages+DynAreaFlags_NeedsDMA
        BNE     %FT70                           ; [yes it could, so do it in lumps]

        MOV     r1, #0                          ; no page block
        MOV     r2, r3, LSR #12                 ; number of pages to do
        BL      CallPreGrow
        LDRVS   r3, [sp]                        ; if error, haven't done any, so restore total as how much to do
        BVS     %FT95

        Push    "r3, r7"
        MOV     r2, r7, LSR #12
        BL      DoTheGrowNotSpecified
        Pull    "r3, r7"
        SUBS    r3, r3, r7                      ; subtract off what we just did

        MOVHI   r7, r3                          ; if not finished, then start 2nd half
        LDRHI   r11, =ZeroPage+AppSpaceDANode   ; which is app space
        MOVHI   r2, r7, LSR #12
        BLHI    DoTheGrowNotSpecified

        LDR     r3, [sp]                        ; restore total amount
        MOV     r1, #0                          ; indicate no page block (and ptr to semaphore)
      [ ZeroPage = 0
        STR     r1, [r1, #CDASemaphore]         ; OK to reenter now (we've done the damage)
      |
        LDR     r2, =ZeroPage
        STR     r1, [r2, #CDASemaphore]         ; OK to reenter now (we've done the damage)
      ]
        MOV     r2, r3, LSR #12
        BL      CallPostGrow
        BVS     %FT95
        B       %FT80

70
        Push    "r3, r7"
        CMP     r7, #PageBlockChunk             ; only do 1 area, so do min(r7,page)
        MOVHI   r7, #PageBlockChunk
        MOV     r2, r7, LSR #12                 ; number of entries to fill in in page block
        BL      DoTheGrow
        Pull    "r3, r7"
        BVS     %FT95
        CMP     r7, #PageBlockChunk             ; if 1st area is more than 1 page
        SUBHI   r3, r3, #PageBlockChunk         ; then reduce total
        SUBHI   r7, r7, #PageBlockChunk         ; and partial amounts by 1 page and do it again
        BHI     %BT70

        SUBS    r3, r3, r7                      ; subtract off what we just did
        MOVHI   r7, r3                          ; if not finished, then start 2nd half
        LDRHI   r11, =ZeroPage+AppSpaceDANode   ; which is app space
        BHI     %BT70                           ; and loop
80
        Pull    "r3"                            ; restore total amount

        MOV     r1, r3
        LDR     r0, [r12, #DANode_Number]       ; reload dynamic area number
        B       IssueServiceMemoryMoved

95
        Pull    "r1"                            ; restore total amount
        SUB     r1, r1, r3                      ; subtract off amount left, to leave done amount
        B       ChangeDynErrorSomeMoved

GenNotAllMovedError Entry "r0"
        ADRL    r0, ErrorBlock_ChDynamNotAllMoved
 [ International
        BL      TranslateError
 ]
        STR     r0, [sp, #2*4]          ; sp -> r0,lr, then stacked r0,r2-r9,r10,lr
        LDR     lr, [sp, #12*4]
        ORR     lr, lr, #V_bit
        STR     lr, [sp, #12*4]
        EXIT

        LTORG

ChangeDynError

; in:   r0 -> error
;       r10 -> area that we tried to shrink/grow

        MOV     r1, #0
ChangeDynErrorSomeMoved
        STR     r0, [sp]
        LDR     lr, [sp, #10*4]
        ORR     lr, lr, #V_bit
        STR     lr, [sp, #10*4]
        B       SomeMemoryMoved

NoMemoryMoved
        MOV     r1, #0                          ; nothing moved
SomeMemoryMoved
        LDR     r0, [r10, #DANode_Number]       ; reload area number

; and drop thru to...

IssueServiceMemoryMoved

; in:   r0 = area number that was shrunk/grown
;       r1 = amount moved (signed)
;
  [ DA_Batman
        CMP     r0, #ChangeDyn_Batcall
        BEQ     ISMM_BatCloak           ; cloaking device (no service issue)
  ]
        Push    "r1"
        MOV     r2, r0                  ; r2 = area number
        MOV     r0, r1                  ; amount moved (signed)
        MOV     r1, #Service_MemoryMoved
        BL      Issue_Service
        Pull    "r1"                    ; restore amount moved
  [ DA_Batman
ISMM_BatCloak
  ]
        TEQ     r1, #0
        RSBMI   r1, r1, #0              ; r1 on exit = unsigned amount

        LDR     r0, =ZeroPage
      [ ZeroPage = 0
        STR     r0, [r0, #CDASemaphore] ; clear CDASemaphore
      |
        MOV     lr, #0
        STR     lr, [r0, #CDASemaphore] ; clear CDASemaphore
      ]
        Pull    "r0, r2-r9, r10, lr"
        ExitSWIHandler

 [ ShrinkableDAs
; ***********************************************************************************
;
;       TryToShrinkShrinkables - Attempt to make more space by shrinking shrinkable areas if appropriate
;
; in:   r1 = total amount we wish to have in src area (already limited by max_size of destination area)
;       r2 = current size of src area
;       r11 -> src area node (we don't do anything unless this is the free pool)
;       r12 -> dst area node
;       C = 0
;
; out:  r2 = new size of src area
;       C=0 => failed to move as much as we wanted
;       C=1 => succeeded in moving as much as we wanted

TryToShrinkShrinkables ROUT
        Entry "r0,r1,r10"
        LDR     lr, [r11, #DANode_Number]
        TEQ     lr, #ChangeDyn_FreePool
        EXIT    NE                              ; if src <> free pool, exit with C, V flags intact

        LDR     r10, =ZeroPage+DAList
        ASSERT  DANode_Link = 0                 ; because DAList has only link
10
        LDR     r10, [r10, #DANode_Link]        ; and load next
        CMP     r10, #1                         ; any more nodes?
        EXIT    CC                              ; no, then no match
        TEQ     r10, r12                        ; check area <> dest
        LDRNE   lr, [r10, #DANode_Flags]        ; and area is shrinkable
        TSTNE   lr, #DynAreaFlags_Shrinkable
        BEQ     %BT10                           ; if not, try next area

        SUBS    r1, r1, r2                      ; r1 = amount we still need
        LDR     lr, [r10, #DANode_Size]         ; available size of this area
        CMP     lr, r1
        MOVCC   r1, lr                          ; min(amount we need, size of this area)
        RSB     r1, r1, #0                      ; make negative - it's a shrink
        LDR     r0, =ZeroPage
      [ ZeroPage = 0
        STR     r0, [r0, #CDASemaphore]         ; momentarily pretend we're not threaded
      |
        MOV     lr, #0
        STR     lr, [r0, #CDASemaphore]         ; momentarily pretend we're not threaded
      ]
        LDR     r0, [r10, #DANode_Number]
        SWI     XOS_ChangeDynamicArea
      [ ZeroPage = 0
        MOV     r0, #1
        STR     r0, [r0, #CDASemaphore-1]       ; we're threaded again
      |
        LDR     r0, =ZeroPage
        STR     r0, [r0, #CDASemaphore]         ; we're threaded again
      ]
        LDR     r1, [sp, #4]                    ; reload original r1
        LDR     r2, [r11, #DANode_Size]         ; get new size of src area
        CMP     r2, r1
        BCC     %BT10                           ; if still too small, loop
        EXIT                                    ; exit CS indicating success
 ]

; ***********************************************************************************
;
;       DoTheGrow - Do one chunk of growing, small enough to fit into the page block on the stack
;
; in:   r2 = number of entries to put in page block (for this chunk)
;       r5 = page size
;       r7 = amount taking from src area (in this chunk)
;       (r10 -> dest area)
;       r11 -> src area
;       r12 -> dest area
;
; out:  r0-r2,r4,r6-r9 may be corrupted
;       r3,r5,r10-r12 preserved
;
; Note: Removal is from one area only, the calling routine breaks the chunks up at free/app boundary.

; Temporary (stack frame) workspace used by this routine

                ^       0, sp
NumEntries      #       4                       ; Number of entries to do for this chunk
TotalAmount     #       4                       ; Total size of grow for this chunk (ie entry value of r3)

DoTheGrowNotSpecifiedStackSize * :INDEX: @      ; amount of stack needed for 'not specified' version

DestAddr        #       4                       ; Log addr of 1st page being added to dest
DestFlags       #       4                       ; Page flags for destination area
SavedPSR        #       4                       ; PSR before IRQs disabled
Offset1To2      #       4                       ; Offset from 1st to 2nd bank
PageBlock1      #       PageBlockSize           ; 1st page block, for original page numbers and phys. addrs
PageBlock2      #       PageBlockSize           ; 2nd page block, for new page numbers and phys. addrs

DoTheGrowStackSize *    :INDEX: @

; Offset1To2 is only used by the first half of the routine. Reuse the space as flags for the second half:
                    ^   :INDEX: Offset1To2, sp
NeedToMoveFlag      #   1                       ; Whether we still need to move the current page
                    #   3                       ; (spare)

DoTheGrow ROUT
        Entry "r3,r5,r10-r12", DoTheGrowStackSize

; First fill in the page block with -1 in the physical page number words

        STR     r2, NumEntries                  ; save number of entries for use later
        STR     r7, TotalAmount                 ; save amount growing by

        FastCDA_ProfStart DoTheGrowInit, r0, r1, lr
        ADR     r1, PageBlock1                  ; point at 1st page block on stack
        ADD     lr, r2, r2, LSL #1              ; lr = number of words in page block
        ADD     lr, r1, lr, LSL #2              ; lr -> off end of page block
        MOV     r0, #-1
10
        STR     r0, [lr, #-12]!                 ; store -1, going backwards
        STR     r0, [lr, #PageBlockSize]        ; and put -1 in 2nd page block as well
        TEQ     lr, r1                          ; until the end
        BNE     %BT10
        FastCDA_ProfEnd DoTheGrowInit, r0, r3, lr

; Now call the pre-grow handler

        MOV     r3, r7
        BL      CallPreGrow
        EXIT    VS

; now check to see if particular pages are required

        LDR     lr, [r1]                        ; load page number in 1st entry
        CMP     lr, #-1                         ; is it -1?
        BNE     DoTheGrowPagesSpecified         ; if not, then jump to special code

; now move pages starting from end of area

        MOV     r2, r3                          ; amount moving
        LDR     r0, [r11, #DANode_Base]
        LDR     r3, [r11, #DANode_Size]
        ADD     r0, r0, r3                      ; move r0 to point to after end of area
        SUB     r3, r3, r2                      ; reduce by amount moving from area
        STR     r3, [r11, #DANode_Size]         ; store reduced source size
      [ ZeroPage = 0
        TEQ     r11, #AppSpaceDANode                    ; if just appspace
      |
        LDR     r1, =ZeroPage+AppSpaceDANode
        TEQ     r11, r1                                 ; if just appspace
      ]
        STREQ   r3, [r11, #MemLimit-AppSpaceDANode]     ; then store in memlimit

        LDR     r1, [r12, #DANode_Base]
        LDR     r3, [r12, #DANode_Size]

        LDR     r6, [r12, #DANode_Flags]        ; r6 = dst flags
        LDR     lr, =DynAreaFlags_AccessMask
        TST     r6, #DynAreaFlags_DoublyMapped  ; check if dst is doubly mapped
        AND     r6, r6, lr
        BEQ     %FT25                           ; [it's not, so skip all this]

; we must shunt all existing pages in dest area down

        MOVS    r4, r3                          ; amount to do
        BEQ     %FT20                           ; [none, so skip all this]

      [ FastCDA_UpFront
        ; Perform sledgehammer logic upfront
        Push    "r0,r2,r6"
        MOV     r0, r1
        MOV     r2, r3
        BL      CheckCacheabilityR0ByMinusR2
        TST     r6, #DynAreaFlags_NotCacheable
        LDR     r0, =ZeroPage
        ADR     lr, %FT14
        ARMop   MMU_Changing, EQ, tailcall, r0
        ARMop   MMU_ChangingUncached, NE, tailcall, r0
14
        Pull    "r0,r2,r6"
        ORR     r6, r6, #PageFlags_Unsafe
      ]

        Push    "r0, r1"
        SUB     r0, r1, r3                      ; src starts at start of 1st copy = start of 2nd - old size
        SUB     r1, r0, r2                      ; dst start = src start - amount of room needed
        MOV     r9, #0                          ; no funny business while moving these pages
15
        BL      MovePageAtR0ToR1WithAccessR6    ; move page
        ADD     r0, r0, r5                      ; advance src ptr
        ADD     r1, r1, r5                      ; advance dst ptr
        SUBS    r4, r4, r5                      ; one less page to move
        BNE     %BT15                           ; loop if more
        Pull    "r0, r1"                        ; restore original regs
20
        ADD     r9, r3, r2                      ; set up offset from 1st copy to 2nd copy (= new size)
25
        ADD     r1, r1, r3                      ; r1 -> address of 1st extra page
   [ FastCDA_UpFront
        ; Flush src region from cache
        Push    "r0-r1,r6"
        BL      CheckCacheabilityR0ByMinusR2
        TST     r6, #DynAreaFlags_NotCacheable
        LDR     r4, =ZeroPage
        MOV     r1, r2, LSR #12
        ADR     lr, %FT29
        ARMop   MMU_ChangingEntries, EQ, tailcall, r4
        ARMop   MMU_ChangingUncachedEntries, NE, tailcall, r4
29
        Pull    "r0-r1,r6"
        ; Now BangCam for all the pages
        ORR     r6, r6, #PageFlags_Unsafe
   ]
        MOV     r4, #0                          ; amount done so far
        MOV     r10, r2                         ; move amount to do into r10, as routine returns page number in r2
        ADR     r3, PageBlock1                  ; point at 1st entry we have to update
30
        SUB     r0, r0, r5                      ; pre-decrement source pointer
 [ DebugCDA2
        DREG    r0, "Moving page at ", cc
        DREG    r1, " to ", cc
        DREG    r6, " with PPL "
 ]
        BL      MovePageAtR0ToR1WithAccessR6ReturnPageNumber
        STR     r2, [r3], #12                   ; store page number and move on
        ADD     r1, r1, r5
        ADD     r4, r4, r5
        CMP     r4, r10                         ; have we done all of it?
        BNE     %BT30                           ; [no, so loop]
35
        LDR     r3, [r12, #DANode_Size]
        ADD     r3, r3, r10
        STR     r3, [r12, #DANode_Size]         ; store increased destination size

        MOV     r3, r10                         ; r3 = size of change
        LDR     r2, NumEntries                  ; restore number of entries in page block
        ADR     r1, PageBlock1                  ; point at page block 1 with page numbers filled in
        BL      CallPostGrow
        CLRV
        EXIT

DoTheGrowPageUnavailable ROUT

; Come here if a required page is not available
; First we need to go back thru all the part of the page block we've already done,
; marking the pages as not being used after all

        ADR     r2, PageBlock1
38
        LDR     r4, [r1, #-12]!                 ; r4 = physical page number
        ADD     r4, r0, r4, LSL #3              ; point at cam entry
        LDMIA   r4, {r8, lr}
        BIC     lr, lr, #PageFlags_Required
        STMIA   r4, {r8, lr}
        TEQ     r1, r2
        BNE     %BT38

; since pre-grow handler exited without an error, we have to keep our promise
; to call the post-grow handler

        MOV     r3, #0                          ; no pages moved
        MOV     r2, #0                          ; no pages moved
        ADR     r1, PageBlock1                  ; not really relevant
        BL      CallPostGrow

        ADR     r0, ErrorBlock_CantGetPhysMem
 [ International
        BL      TranslateError
 |
        SETV
 ]
        EXIT

        MakeErrorBlock  CantGetPhysMem

DoTheGrowPagesSpecified ROUT

; First check if any of the pages requested are unavailable
; At the same time as we're doing this, we fill in the log. and phys. addresses in the block

        FastCDA_ProfStart MarkRequired, r0, r6, lr
        LDR     r0, =ZeroPage
        LDR     r0, [r0, #CamEntriesPointer]
        LDR     r6, =L2PT
40
        LDR     r3, [r1], #12                   ; r4 = physical page number
        ADD     r4, r0, r3, LSL #3              ; point at cam entry
        LDMIA   r4, {r8, lr}                    ; r8 = log. addr, lr = PPL
        STR     r8, [r1, #4-12]                 ; store log. addr in page block
        STR     r8, [r1, #PageBlockSize+4-12]   ; and in 2nd page block

        TST     lr, #PageFlags_Unavailable :OR: PageFlags_Required ; if page in use by someone else, or by us, then return error
        BNE     DoTheGrowPageUnavailable
        ORR     lr, lr, #PageFlags_Required     ; set bit in flags to say page will be needed
        STR     lr, [r4, #4]                    ; and store back

; work out physical address direct from physical page number, NOT from logical address, since log addr may be Nowhere (multiply mapped)

        LDR     r4, =ZeroPage+PhysRamTable
42
        LDMIA   r4!, {r8, lr}                   ; load phys addr, size
        SUBS    r3, r3, lr, LSR #12             ; subtract off number of pages in this chunk
        BCS     %BT42

        ADD     r3, r3, lr, LSR #12             ; put back what could not be subtracted
        ADD     r8, r8, r3, LSL #12             ; and add onto base address
        STR     r8, [r1, #8-12]                 ; store physical address in page block

        SUBS    r2, r2, #1
        BNE     %BT40
        FastCDA_ProfEnd MarkRequired, r0, r6, lr

; now issue Service_PagesUnsafe

        FastCDA_ProfStart PagesUnsafe, r0, r6, lr
        ADR     r2, PageBlock1                  ; r2 -> 1st page block
        LDR     r3, NumEntries                  ; r3 = number of entries in page block
        MOV     r1, #Service_PagesUnsafe
        BL      Issue_Service
        FastCDA_ProfEnd PagesUnsafe, r0, r6, lr

; now move the pages

        LDR     r2, TotalAmount                 ; amount moving
        LDR     r0, [r11, #DANode_Base]
        LDR     r3, [r11, #DANode_Size]
        ADD     r0, r0, r3                      ; move r0 to point to after end of area
        SUB     r3, r3, r2                      ; reduce by amount moving from area
        STR     r3, [r11, #DANode_Size]         ; store reduced source size
      [ ZeroPage = 0
        TEQ     r11, #AppSpaceDANode                    ; if appspace
      |
        LDR     r1, =ZeroPage+AppSpaceDANode
        TEQ     r11, r1                                 ; if appspace
      ]
        STREQ   r3, [r11, #MemLimit-AppSpaceDANode]     ; then update memlimit

        LDR     r1, [r12, #DANode_Base]
        LDR     r3, [r12, #DANode_Size]

        LDR     r6, [r12, #DANode_Flags]        ; r6 = dst flags
        LDR     lr, =DynAreaFlags_AccessMask
        AND     r6, r6, lr
        ORR     r6, r6, #PageFlags_Unavailable  ; set unavailable bit
        STR     r6, DestFlags                   ; save for later
        TST     r6, #DynAreaFlags_DoublyMapped  ; check if dst is doubly mapped
        BEQ     %FT55                           ; [it's not, so skip all this, and r9 will be irrelevant]

; we must shunt all existing pages in dest area down

        MOVS    r4, r3                          ; amount to do
        BEQ     %FT50                           ; [none, so skip all this]

    [ FastCDA_UpFront
        ; Perform sledgehammer logic upfront
        Push    "r0,r2,r6"
        FastCDA_ProfStart DoublyCheckCacheability, r0, r6, lr
        MOV     r0, r1
        MOV     r2, r3
        BL      CheckCacheabilityR0ByMinusR2
        FastCDA_ProfEnd DoublyCheckCacheability, r0, r2, lr
        TST     r6, #DynAreaFlags_NotCacheable
        LDR     r2, =ZeroPage
      [ FastCDA_Prof
        LDREQ   lr,[r2,#FastCDA_Prof_MMUChanging]
        LDRNE   lr,[r2,#FastCDA_Prof_MMUChangingUncached]
        MRC     p15,0,r0,c9,c13,0
        SUB     lr,lr,r0
        STREQ   lr,[r2,#FastCDA_Prof_MMUChanging]
        STRNE   lr,[r2,#FastCDA_Prof_MMUChangingUncached]
      ]
        ADR     lr, %FT44
        ARMop   MMU_Changing, EQ, tailcall, r2
        ARMop   MMU_ChangingUncached, NE, tailcall, r2
44
      [ FastCDA_Prof
        MRC     p15,0,r0,c9,c13,0
        TST     r6, #DynAreaFlags_NotCacheable
        LDREQ   lr,[r2,#FastCDA_Prof_MMUChanging]
        LDRNE   lr,[r2,#FastCDA_Prof_MMUChangingUncached]
        ADD     lr,lr,r0
        STREQ   lr,[r2,#FastCDA_Prof_MMUChanging]
        STRNE   lr,[r2,#FastCDA_Prof_MMUChangingUncached]
      ]
        Pull    "r0,r2,r6"
        ORR     r6, r6, #PageFlags_Unsafe
    ]

        Push    "r0, r1"
        FastCDA_ProfStart DoublyMovePages, r0, r9, lr
        SUB     r0, r1, r3                      ; src starts at start of 1st copy = start of 2nd - old size
        SUB     r1, r0, r2                      ; dst start = src start - amount of room needed
        MOV     r9, #0                          ; no funny business while moving these pages
45
        BL      MovePageAtR0ToR1WithAccessR6    ; move page
        ADD     r0, r0, r5                      ; advance src ptr
        ADD     r1, r1, r5                      ; advance dst ptr
        SUBS    r4, r4, r5                      ; one less page to move
        BNE     %BT45                           ; loop if more
        FastCDA_ProfEnd DoublyMovePages, r0, r9, lr
        Pull    "r0, r1"                        ; restore original regs
50
        ADD     r9, r3, r2                      ; set up offset from 1st copy to 2nd copy (= new size)
55
        STR     r9, Offset1To2                  ; store offset 1st to 2nd copy
        ADD     r1, r1, r3                      ; r1 -> address of 1st extra page
        STR     r1, DestAddr
        ADR     r8, PageBlock1                  ; r8 -> position in 1st page block
        SUB     r2, r0, r2                      ; r2 = lowest address being removed from src
        LDR     r3, =ZeroPage
        LDR     r3, [r3, #CamEntriesPointer]
        MOV     r4, r0                          ; r4 is where we're at in allocating spare logical addresses
        LDR     r9, NumEntries                  ; number of entries still to do in 1st loop

; Now before we start, we must construct the second page block, with replacement page numbers

;        DLINE   "Start of 1st loop"
        FastCDA_ProfStart FindSpare, r6, r1, lr

60
        LDR     r6, [r8], #12                   ; r6 = page number required
        LDR     r10, [r8, #8-12]                ; r10 = phys addr
        LDR     lr, [r3, r6, LSL #3]            ; lr = logical address for this page

;        DREG    r6, "Checking page ", cc
;        DREG    lr, "at address "

        CMP     lr, r2                          ; check if address is one being taken from src anyway
        BCC     %FT63
        CMP     lr, r0
        BCS     %FT63

;        DLINE   "Page is being taken away anyway"
        B       %FT68                           ; [page is being taken anyway, so use same page number + phys addr in 2nd block]

; page is not one being taken away, so put in 1st replacement page that isn't required by area

63
;        DLINE   "Page is not being taken, looking for replacement"

64
        SUB     r4, r4, r5                      ; go onto next page being taken from src
;        DREG    r4, "Considering address "

        LDR     lr, =L2PT
        LDR     lr, [lr, r4, LSR #10]           ; get L2PT entry (to get phys addr) for next free page
        MOV     r10, lr, LSR #12                ; r10 = phys addr >>> 12

; now convert phys addr to page number

        MOV     r6, #0
        LDR     r1, =ZeroPage+PhysRamTable
66
        LDMIA   r1!, {r7, lr}                   ; load phys addr, size
        SUB     r7, r10, r7, LSR #12            ; number of pages into this bank
        CMP     r7, lr, LSR #12                 ; if more than there are here,
        ADDCS   r6, r6, lr, LSR #12             ; then advance page number by number of pages in this bank
        BCS     %BT66                           ; and go onto next bank

        ADD     r6, r6, r7                      ; advance page number by no. of pages into this bank

        ADD     r1, r3, r6, LSL #3              ; r1 -> cam entry for this page
        LDR     r1, [r1, #4]                    ; get PPL for this page
        TST     r1, #PageFlags_Required         ; if this page is required for the operation
        BNE     %BT64                           ; then try next page

        MOV     r10, r10, LSL #12               ; make r10 proper phys addr
;        DREG    r6, "Using page number "
68
        STR     r6, [r8, #PageBlockSize-12]     ; store page number in 2nd block
        STR     r10, [r8, #PageBlockSize+8-12]  ; and store phys addr

        SUBS    r9, r9, #1                      ; one less entry to do
        BNE     %BT60
        FastCDA_ProfEnd FindSpare, r7, r1, lr

        MOV     r7, r3                          ; r7 -> camentries

; Now we can go onto the 2nd loop which actually moves the pages

     [ FastCDA_FIQs
        ; Claim FIQs for this entire loop
        ; (With the old behaviour, for large grows, total time in ReleaseFIQ could be several centiseconds, since the kernel reinstalls the default handler each time)
        FastCDA_ProfStart ClaimFIQ, r6, r1, lr
        MOV     r1, #Service_ClaimFIQ
        BL      Issue_Service
        FastCDA_ProfEnd ClaimFIQ, r6, r1, lr
     ]

        LDR     r1, DestAddr
        MOV     r4, #0                          ; amount done
        MOV     r0, r7                          ; point r0 at camentries
        LDR     r7, TotalAmount                 ; amount to do
        ADR     r8, PageBlock1
        LDR     r9, Offset1To2
70
        MRS     r14, CPSR
        STR     r14, SavedPSR                   ; save old PSR (note: stack must be flat when we do this!)

    [ FastCDA_NoPhysical
        ; Grab the flags for the page we're replacing; NoPhysical optimisation means the page may get mapped to its target pos earlier than before, causing the flags in the CAM map to be "wrong" when we read them back out later on
        LDR     r11, [r8, #0]                   ; need to get PPL for page being replaced
        ADD     lr, r0, #4                      ; point at PPLs, not addresses
        LDR     r11, [lr, r11, LSL #3]
        MOV     lr, #1
        STRB    lr, NeedToMoveFlag
    ]

        Push    "r0-r4,r7-r12"                  ; save regs used during copy
    [ :LNOT: FastCDA_FIQs
        FastCDA_ProfStart ClaimFIQ, r6, r1, lr
        MOV     r1, #Service_ClaimFIQ
        BL      Issue_Service
        FastCDA_ProfEnd ClaimFIQ, r6, r1, lr
    ]

        WritePSRc I_bit+SVC_mode, r6            ; disable IRQs round here (we don't want interrupt code to update
                                                ; the old mapping behind us while we're trying to copy it)

        LDR     r6, [r8, #0]                    ; r6 = page number required
        LDR     lr, [r8, #PageBlockSize+0]      ; lr = page number of replacement page
        TEQ     r6, lr                          ; if the same
        Pull    "r0-r4,r7-r12", EQ              ; then restore registers
        BEQ     %FT76                           ; and skip copy and first page move

        ;mjs
        ; - if the old page is currently mapped in, copy normally
        ; - if the old page is not mapped in, copy via temporary mapping
        ; The old scheme, always copying from other mapping, had interrupt cache coherency hole, at least for
        ; ARM with writeback cache (bug in 3.7, fixed in Ursula, then lost)

        LDR     r6, [r8, #4]                    ;logical address of src page

      [ FastCDA_CorruptFreePool
        ; If the source is in the free pool, we don't need to preserve its contents
        LDR     r3, =ZeroPage+FreePoolDANode
        SUB     r2, r6, #FreePoolAddress
        LDR     r3, [r3, #DANode_MaxSize]
        CMP     r2, r3
        BLO     %FT74
      ]

        LDR     r0, [r0, lr, LSL #3]            ; r0 = log. address for replacement page (NB use logical address to write to, for cache consistency)

        LDR     r3, =Nowhere
        TEQ     r6, r3                          ;will be 'Nowhere' if not mapped in
        BNE     %FT71

      [ FastCDA_NoPhysical
        ; No need to use AccessPhysicalAddress here - if the required page isn't mapped in, all we need to do is map it in at the target address and use that mapping to copy the data out
        LDR     r2, [r8, #0]
        LDR     r3, [sp, #4] ; Get stacked r1
        LDR     r11, [sp, #11*4+:INDEX:DestFlags]
        FastCDA_ProfStart MoveNeeded, lr, r4, r7
        BL      Call_CAM_Mapping                ; move needed page to destination
        FastCDA_ProfEnd MoveNeeded, lr, r4, r7
        MOV     r6, r3                          ; r6 = logical address of src for copy
        MOV     lr, #0
        STRB    lr, [sp, #11*4+:INDEX:NeedToMoveFlag]
      |
        ASSERT  HAL
        SUB     sp, sp, #4                      ; for oldp
        Push    "r0,r1"
        FastCDA_ProfStart AccessPhysical, r0, r1, lr
        MOV     r0, #0
        LDR     r1, [r8, #8]                    ; r1 = physical address of src for copy
        ADD     r2, sp, #8                      ; must use physical address, as page may be mapped to nowhere along with others
        BL      RISCOS_AccessPhysicalAddress
        MOV     r6, r0                          ; r6 = logical address of src for copy
        FastCDA_ProfEnd AccessPhysical, r0, r1, lr
        Pull    "r0,r1"
      ]

71
        FastCDA_ProfStart CopyPage, r2, r3, r4
        ADD     lr, r6, r5                      ; lr = end src address
72
        LDMIA   r6!, {r2, r3, r4, r7, r9, r10, r11, r12}
        STMIA   r0!, {r2, r3, r4, r7, r9, r10, r11, r12}
        TEQ     r6, lr
        BNE     %BT72

        FastCDA_ProfEnd CopyPage, r2, r3, r4

     [ :LNOT: FastCDA_NoPhysical
        LDR     r0, [r8, #4]                    ;logical address of src page
        LDR     r3, =Nowhere
        TEQ     r0, r3

        Pull    "r0", EQ                        ; oldp
      [ FastCDA_Prof
        BNE     %FT73
        FastCDA_ProfStart ReleasePhysical, r2, r3, r4
      ]
        BLEQ    RISCOS_ReleasePhysicalAddress
      [ FastCDA_Prof
        FastCDA_ProfEnd ReleasePhysical, r2, r3, r4
73
      ]
     ]

; now check if page we're replacing is in L2PT, and if so then adjust L1PT entries (4 of these)

        LDR     r6, [r8, #4]                    ; look at logical address of page being replaced
        SUBS    r6, r6, #L2PT
        BCC     %FT74                           ; address is below L2PT
        CMP     r6, #4*1024*1024
        BCS     %FT74                           ; address is above L2PT

        LDR     r2, =L1PT
        ADD     r2, r2, r6, LSR #(12-4)         ; address in L1 of 4 consecutive words to update
        LDR     r3, [r2]                        ; load 1st word, to get AP etc bits
        MOV     r3, r3, LSL #(31-9)             ; junk other bits
        LDR     r4, [r8, #PageBlockSize+8]      ; load new physical address for page
        ORR     r3, r4, r3, LSR #(31-9)         ; and merge with AP etc bits
        STR     r3, [r2], #4
        ADD     r3, r3, #&400
        STR     r3, [r2], #4
        ADD     r3, r3, #&400
        STR     r3, [r2], #4
        ADD     r3, r3, #&400
        STR     r3, [r2], #4
74
        Pull    "r0-r4,r7-r12"                  ; restore registers

        ; mjs
        ; OK, what we are about to do is:
        ;   1) move replacement page in (to replace needed page)
        ;   2) move needed page to required destination
        ; This order means that we don't leave a temporary hole at the logical address we're substituting,
        ; which is vital at least in the horrendous case where the logical page is itself used for L2PT.
        ; However, this means there is a potential temporary degeneracy in the caches, two physical pages
        ; having been seen at the same logical address (undefined behaviour).
        ; So, to be safe, we do a MMUChangingEntry first, for the logical page, which will clean/invalidate
        ; caches and invalidate TLBs, to avoid degeneracy. This is slight overkill in some cases, but vital
        ; to avoid serious grief in the awkward cases. Fortunately, these page substitutions are relatively
        ; rare, so performance is not critical.

 [ :LNOT: FastCDA_NoPhysical
        LDR     lr, =ZeroPage
        LDR     lr, [lr, #CamEntriesPointer]    ; lr -> soft cam map
        ADD     lr, lr, #4                      ; point at PPLs, not addresses
        LDR     r2, [r8, #0]                    ; need to get PPL for page being replaced
        LDR     r11, [lr, r2, LSL #3]
 ]
        BIC     r11, r11, #PageFlags_Required   ; knock off bits that indicate that it was a required page

        ADD     lr, r8, #PageBlockSize
        LDMIA   lr, {r2, r3}                    ; get page number, logical address

        LDR     lr, =Nowhere                    ; There's no point in cleaning the nowhere page, and on some architectures it'll even trigger an abort handler due to the lack of mapping
        TEQ     r3, lr
        BEQ     %FT75
      [ FastCDA_Unnecessary
        ; We only need to clean the cache/TLB if the page is cacheable
        ; For uncacheable pages, BangL2PT will flush the TLB for us just before the mapping is updated
        TST     r11, #DynAreaFlags_NotCacheable
        BNE     %FT75
      ]
        Push    "r0, r4"
        MOV     r0, r3
      [ FastCDA_Prof
        FastCDA_ProfStart ChangingEntry, r6, lr, r4
      ]
        LDR     r4, =ZeroPage
        ARMop   MMU_ChangingEntry,,,r4
      [ FastCDA_Prof
        FastCDA_ProfEnd ChangingEntry, r6, lr, r4
      ]
        Pull    "r0, r4"
75

        FastCDA_ProfStart MoveReplacement, r6, lr, r5
        BL      Call_CAM_Mapping                ; move replacement page in
        FastCDA_ProfEnd MoveReplacement, r6, lr, r5
76
        LDR     r2, [r8, #0]
        MOV     r3, r1
        LDR     r11, DestFlags
      [ FastCDA_NoPhysical
        LDRB    lr, NeedToMoveFlag
        TEQ     lr, #0
        BEQ     %FT77                           ; don't bother if page already been moved to dest
      ]
        FastCDA_ProfStart MoveNeeded, r6, lr, r5
        BL      Call_CAM_Mapping                ; move needed page to destination
        FastCDA_ProfEnd MoveNeeded, r6, lr, r5

77
        LDR     lr, SavedPSR
        MSR     CPSR_cf, lr

      [ :LNOT: FastCDA_FIQs
        Push    "r1"
        FastCDA_ProfStart ReleaseFIQ, r1, lr, r5
        MOV     r1, #Service_ReleaseFIQ
        BL      Issue_Service
        FastCDA_ProfEnd ReleaseFIQ, r1, lr, r5
        Pull    "r1"
      ]
      [ FastCDA_Prof
        MOV     r5, #4096
      ]

        ADD     r1, r1, r5                      ; advance dest ptr
        ADD     r4, r4, r5                      ; increment amount done
        ADD     r8, r8, #12                     ; advance page block ptr
        CMP     r4, r7                          ; have we done all?
        BNE     %BT70                           ; [no, so loop]

     [ FastCDA_FIQs
        FastCDA_ProfStart ReleaseFIQ, r1, lr, r2
        MOV     r1, #Service_ReleaseFIQ
        BL      Issue_Service
        FastCDA_ProfEnd ReleaseFIQ, r1, lr, r2
     ]

        LDR     r3, [r12, #DANode_Size]
        ADD     r3, r3, r7
        STR     r3, [r12, #DANode_Size]         ; store increased destination size

; now issue Service_PagesSafe

        FastCDA_ProfStart PagesSafe, r1, r2, r3
        LDR     r2, NumEntries
        ADR     r3, PageBlock1
        ADR     r4, PageBlock2
        MOV     r1, #Service_PagesSafe
        BL      Issue_Service
        FastCDA_ProfEnd PagesSafe, r1, r2, r3

; now call Post_Grow handler

        LDR     r3, TotalAmount                 ; size of grow
        LDR     r2, NumEntries                  ; restore number of entries in page block
        ADR     r1, PageBlock1                  ; point at page block 1 with page numbers filled in
        BL      CallPostGrow
        CLRV
        EXIT

        LTORG

; ***********************************************************************************
;
;       DoTheGrowNotSpecified - Do one chunk of growing, with no page block
;                               But don't call pre-grow or post-grow either
;
; in:   r2 = number of pages to do (in this chunk)
;       r5 = page size
;       r7 = amount taking from src area (in this chunk)
;       (r10 -> dest area)
;       r11 -> src area
;       r12 -> dest area
;
; out:  r0-r2,r4,r6-r9 may be corrupted
;       r3,r5,r10-r12 preserved
;
; Note: Removal is from one area only, the calling routine breaks the chunk at free/app boundary.


DoTheGrowNotSpecified ROUT
        Entry "r3,r5,r10-r12", DoTheGrowNotSpecifiedStackSize

        STR     r2, NumEntries                  ; save number of entries for use later
        STR     r7, TotalAmount                 ; save amount growing by

; now move pages starting from end of area

        MOV     r2, r7                          ; amount moving
        LDR     r0, [r11, #DANode_Base]
        LDR     r3, [r11, #DANode_Size]
        ADD     r0, r0, r3                      ; move r0 to point to after end of area
        SUB     r3, r3, r2                      ; reduce by amount moving from area
        STR     r3, [r11, #DANode_Size]         ; store reduced source size
      [ ZeroPage = 0
        TEQ     r11, #AppSpaceDANode                    ; if just appspace
      |
        LDR     r1, =ZeroPage+AppSpaceDANode
        TEQ     r1, r11                                 ; if just appspace
      ]
        STREQ   r3, [r11, #MemLimit-AppSpaceDANode]     ; then store in memlimit

        LDR     r1, [r12, #DANode_Base]
        LDR     r3, [r12, #DANode_Size]

        LDR     r6, [r12, #DANode_Flags]        ; r6 = dst flags
        LDR     lr, =DynAreaFlags_AccessMask
        AND     r6, r6, lr
        TST     r6, #DynAreaFlags_DoublyMapped  ; check if dst is doubly mapped
        BEQ     %FT25                           ; [it's not, so skip all this]

; we must shunt all existing pages in dest area down

        MOVS    r4, r3                          ; amount to do
        BEQ     %FT20                           ; [none, so skip all this]

      [ FastCDA_UpFront
        ; Perform sledgehammer logic upfront
        Push    "r0,r2,r6"
        MOV     r0, r1
        MOV     r2, r3
        BL      CheckCacheabilityR0ByMinusR2
        TST     r6, #DynAreaFlags_NotCacheable
        LDR     r0, =ZeroPage
        ADR     lr, %FT14
        ARMop   MMU_Changing, EQ, tailcall, r0
        ARMop   MMU_ChangingUncached, NE, tailcall, r0
14
        Pull    "r0,r2,r6"
        ORR     r6, r6, #PageFlags_Unsafe
      ]

        Push    "r0, r1"
        SUB     r0, r1, r3                      ; src starts at start of 1st copy = start of 2nd - old size
        SUB     r1, r0, r2                      ; dst start = src start - amount of room needed
        MOV     r9, #0                          ; no funny business while moving these pages
15
        BL      MovePageAtR0ToR1WithAccessR6    ; move page
        ADD     r0, r0, r5                      ; advance src ptr
        ADD     r1, r1, r5                      ; advance dst ptr
        SUBS    r4, r4, r5                      ; one less page to move
        BNE     %BT15                           ; loop if more
        Pull    "r0, r1"                        ; restore original regs
20
        ADD     r9, r3, r2                      ; set up offset from 1st copy to 2nd copy (= new size)
25
        ADD     r1, r1, r3                      ; r1 -> address of 1st extra page
   [ FastCDA_UpFront
        ; Flush src region from cache
        Push    "r0-r1,r6"
        BL      CheckCacheabilityR0ByMinusR2
        TST     r6, #DynAreaFlags_NotCacheable
        LDR     r4, =ZeroPage
        MOV     r1, r2, LSR #12
        ADR     lr, %FT29
        ARMop   MMU_ChangingEntries, EQ, tailcall, r4
        ARMop   MMU_ChangingUncachedEntries, NE, tailcall, r4
29
        Pull    "r0-r1,r6"
        ; Now BangCam for all the pages
        ORR     r6, r6, #PageFlags_Unsafe
   ]
        MOV     r4, #0                          ; amount done so far
        MOV     r10, r2                         ; move amount to do into r10
30
        SUB     r0, r0, r5                      ; pre-decrement source pointer
 [ DebugCDA2
        DREG    r0, "Moving page at ", cc
        DREG    r1, " to ", cc
        DREG    r6, " with PPL "
 ]
        BL      MovePageAtR0ToR1WithAccessR6
        ADD     r1, r1, r5
        ADD     r4, r4, r5
        CMP     r4, r10                         ; have we done all of it?
        BNE     %BT30                           ; [no, so loop]
35
        LDR     r3, [r12, #DANode_Size]
        ADD     r3, r3, r10
        STR     r3, [r12, #DANode_Size]         ; store increased destination size

        CLRV
        EXIT

; ***********************************************************************************
;
;       CheckAppSpace - If appspace involved in transfer, issue Service or UpCall
;
;       Internal routine, called by OS_ChangeDynamicArea
;
; in:   r0 = area number passed in to ChangeDyn
;       r10 = size of change (signed)
;       r11 -> node for src
;       r12 -> node for dest
;
; out:  If appspace not involved, or application said it was OK, then
;         V=0
;         All registers preserved
;       else
;         V=1
;         r0 -> error
;         All other registers preserved
;       endif
;

CheckAppSpace ROUT
        Entry "r0-r3"
        LDR     r2, =ZeroPage
        LDR     r3, [r2, #AplWorkSize]
        LDR     r2, [r2, #Curr_Active_Object]
        CMP     r2, r3                          ; check if CAO outside application space
        BHI     %FT20                           ; [it is so issue Service not UpCall]

; CAO in application space, so issue UpCall to check it's OK

        MOV     r0, #UpCall_MovingMemory :AND: &FF
        ORR     r0, r0, #UpCall_MovingMemory :AND: &FFFFFF00
        MOVS    r1, r10
        RSBMI   r1, r1, #0                      ; r1 passed in is always +ve (probably a bug, but should be compat.)

        SWI     XOS_UpCall
        CMP     r0, #UpCall_Claimed             ; if upcall claimed
    [  ChocolateAMB
        BNE     %FT05
        BL      Do_AMB_MakeUnsparse             ; then ok to move memory, so undo laziness and exit
        CLRV
        EXIT
    |
        EXIT    EQ                              ; then OK to move memory, so exit (V=0 from CMP)
    ]

05
        ADR     r0, ErrorBlock_ChDynamCAO
10
 [ International
        BL      TranslateError
 |
        SETV
 ]
        STR     r0, [sp]
        EXIT

; IF service call claimed Then Error AplWSpaceInUse

20
        MOV     r0, r10                         ; amount removing from aplspace
        MOV     r1, #Service_Memory
        BL      Issue_Service
        CMP     r1, #Service_Serviced
        ADREQ   r0, ErrorBlock_AplWSpaceInUse   ; if service claimed, then return error
        BEQ     %BT10
  [ ChocolateAMB
        BL      Do_AMB_MakeUnsparse             ; undo laziness
  ]
        CLRV                                    ; else OK
        EXIT

    [ ChocolateAMB
Do_AMB_MakeUnsparse ROUT
        Push    "r0, lr"
        MOVS    r0, r10
        RSBMI   r0, r0, #0
        BL      AMB_MakeUnsparse  ;shrinking AppSpace, so make sure unsparse over area of shrink
        Pull    "r0, pc"
    ] ;ChocolateAMB

        MakeErrorBlock AplWSpaceInUse
        MakeErrorBlock ChDynamCAO

; ***********************************************************************************
;
;       CallPreShrink - Call pre-shrink routine
;
; in:   r1 = amount shrinking by (+ve)
;       r5 = page size
;       r11 -> node for area being shrunk
;
; out:  If handler exits VC, then r2 = no. of bytes area can shrink by
;       else r0 -> error block or 0 for generic error, and r2=0
;

CallPreShrink Entry "r0,r3,r4, r12"
        LDR     r0, [r11, #DANode_Handler]              ; check if no handler
        CMP     r0, #0                                  ; if none (V=0)
        EXIT    EQ                                      ; then exit

        MOV     r0, #DAHandler_PreShrink                ; r0 = reason code
        MOV     r3, r1                                  ; r3 = amount shrinking by
        LDR     r4, [r11, #DANode_Size]                 ; r4 = current size
        ASSERT  DANode_Handler = DANode_Workspace +4
        ADD     r12, r11, #DANode_Workspace
        MOV     lr, pc
        LDMIA   r12, {r12, pc}                          ; load workspace pointer and jump to handler

; shrink amount returned by handler may not be page multiple (according to spec),
; so we'd better make it so.

        SUB     lr, r5, #1
        BIC     r2, r3, lr                              ; make page multiple and move into r2
        EXIT    VC
        TEQ     r0, #0                                  ; if generic error returned
        ADREQL  r0, ErrorBlock_ChDynamNotAllMoved       ; then substitute real error message
 [ International
        BLEQ    TranslateError
 ]
        STR     r0, [sp]
        EXIT

; ***********************************************************************************
;
;       CallPostShrink - Call post-shrink routine
;
; in:   r2 = amount shrinking by (+ve)
;       r5 = page size
;       r11 -> node for area being shrunk
;
; out:  All registers preserved
;

CallPostShrink Entry "r0,r3,r4, r12"
        LDR     r0, [r11, #DANode_Handler]              ; check if no handler
        CMP     r0, #0                                  ; if none (V=0)
        EXIT    EQ                                      ; then exit

        MOV     r0, #DAHandler_PostShrink               ; r0 = reason code
        MOV     r3, r2                                  ; r3 = amount shrunk by
        LDR     r4, [r11, #DANode_Size]                 ; r4 = new size
        ASSERT  DANode_Handler = DANode_Workspace +4
        ADD     r12, r11, #DANode_Workspace
        MOV     lr, pc
        LDMIA   r12, {r12, pc}                          ; load workspace pointer and jump to handler

        EXIT

; ***********************************************************************************
;
;       CallPreGrow - Call pre-grow routine
;
; in:   Eventually r1 -> page block (on stack)
;                  r2 = number of entries in block
;       but for now these are both undefined
;       r3 = amount area is growing by
;       r5 = page size
;       r12 -> node for area being grown
;
; out:  If can't grow, then
;         r0 -> error
;         V=1
;       else
;         page block may be updated with page numbers (but not yet!)
;         All registers preserved
;         V=0
;       endif
;

CallPreGrow ROUT
        Entry   "r0,r4, r12"
        LDR     r0, [r12, #DANode_Flags]
        TST     r0, #DynAreaFlags_NeedsDMA              ; if DMA needed
        BNE     %FT10                                   ; use special PreGrow

        LDR     r0, [r12, #DANode_Handler]              ; check if no handler
        CMP     r0, #0                                  ; if none (V=0)
        EXIT    EQ                                      ; then exit

        FastCDA_ProfStart CallPreGrow, r0, r4, lr
        MOV     r0, #DAHandler_PreGrow                  ; r0 = reason code
        LDR     r4, [r12, #DANode_Size]                 ; r4 = current size
        ASSERT  DANode_Handler = DANode_Workspace +4
        ADD     r12, r12, #DANode_Workspace
        MOV     lr, pc
        LDMIA   r12, {r12, pc}                          ; load workspace pointer and jump to handler
        FastCDA_ProfEnd CallPreGrow, r12, r4, lr
        EXIT    VC                                      ; if no error then exit

05
        TEQ     r0, #0                                  ; if generic error returned (V still set)
        ADREQL  r0, ErrorBlock_ChDynamNotAllMoved       ; then substitute real error message
 [ International
        BLEQ    TranslateError
 ]
        STR     r0, [sp]
        EXIT

10
        ; Instead of calling the users PreGrow handler, walk PhysRamTable and
        ; the CAM map to look for some free DMAable pages
        ; Note that we don't guarantee physical contiguity - if you want that,
        ; just use OS_Memory 12 or PCI_RAMAlloc instead
        Push    "r1-r3"
        LDR     r0,=ZeroPage+PhysRamTable+4
        MOV     r2,#0                    ; current page number
        LDR     r4,=ZeroPage+CamEntriesPointer
        LDR     r4,[r4]
        ADD     r4,r4,#4                 ; -> base of PPLs
        LDR     r12,[r0],#8              ; get video chunk flags
20
        ADD     r2,r2,r12,LSR #12        ; advance page number
21
        LDR     r12,[r0],#8              ; get next chunk details
        CMP     r12,#0
        BEQ     %FT90
        TST     r12,#OSAddRAM_NoDMA
        BNE     %BT20
        ; Check the CAM map to see if any pages here are free
        MOV     r12,r12,LSR #12
30
        LDR     lr,[r4,r2,LSL #3]
        TST     lr,#PageFlags_Unavailable :OR: PageFlags_Required
        STREQ   r2,[r1],#12
        SUBEQS  r3,r3,#4096
        BEQ     %FT80
        SUBS    r12,r12,#1
        ADD     r2,r2,#1
        BNE     %BT30
        B       %BT21
80
        ; Success
        CLRV
        Pull    "r1-r3"
        EXIT
90
        ; Failure
        SETV
        Pull    "r1-r3"
        MOV     r0,#0
        B       %BT05


; ***********************************************************************************
;
;       CallPostGrow - Call post-grow routine
;
; in:   Eventually, r1 -> page block with actual pages put in
;                   r2 = number of entries in block
;       r3 = size of change
;       r5 = page size
;       r12 -> node for area being grown
;
; out:  All registers preserved
;

CallPostGrow Entry "r0,r3,r4, r12"
        LDR     r0, [r12, #DANode_Handler]              ; check if no handler
        CMP     r0, #0                                  ; if none (V=0)
        EXIT    EQ                                      ; then exit

        FastCDA_ProfStart CallPostGrow, r0, r4, lr
        MOV     r0, #DAHandler_PostGrow                 ; r0 = reason code
        LDR     r4, [r12, #DANode_Size]                 ; r4 = new size
        ASSERT  DANode_Handler = DANode_Workspace +4
        ADD     r12, r12, #DANode_Workspace
        MOV     lr, pc
        LDMIA   r12, {r12, pc}                          ; load workspace pointer and jump to handler
        FastCDA_ProfEnd CallPostGrow, r12, r4, lr
        EXIT

 [ ShrinkableDAs
; ***********************************************************************************
;
;       CallTestShrink - Call test-shrink routine
;
; in:   r11 -> area node
;
; out:  If handler exits VC, then r3 = no. of bytes area can shrink by
;       else r0 -> error block or 0 for generic error, and r3=0
;

CallTestShrink Entry "r0,r4,r5, r12"
        LDR     r0, [r11, #DANode_Handler]              ; check if no handler
        CMP     r0, #0                                  ; if none (V=0)
        EXIT    EQ                                      ; then exit

        MOV     r0, #DAHandler_TestShrink               ; r0 = reason code
        LDR     r4, [r11, #DANode_Size]                 ; r4 = current size
        LDR     r5, =ZeroPage
        LDR     r5, [r5, #Page_Size]                    ; set r5 = page size
        ASSERT  DANode_Handler = DANode_Workspace +4
        ADD     r12, r11, #DANode_Workspace
        MOV     lr, pc
        LDMIA   r12, {r12, pc}                          ; load workspace pointer and jump to handler

; shrink amount returned by handler may not be page multiple (according to spec),
; so we'd better make it so.

        SUBVC   lr, r5, #1
        BICVC   r3, r3, lr                              ; make page multiple
        EXIT    VC
        TEQ     r0, #0                                  ; if generic error returned (V still set)
        ADREQL  r0, ErrorBlock_ChDynamNotAllMoved       ; then substitute real error message
 [ International
        BLEQ    TranslateError
 ]
        STR     r0, [sp]
        MOV     r3, #0                                  ; indicate no shrink possible
        SETV
        EXIT
 ]

; ***********************************************************************************
;
;       MovePageAtR0ToR1WithAccessR6
;
;       Internal routine, called by OS_ChangeDynamicArea
;
; in:   r0 = logical address where page is now
;       r1 = logical address it should be moved to
;       r6 = area flags (which contain access privileges, and cacheable/bufferable bits)
;
; out:  All registers preserved
;

MovePageAtR0ToR1WithAccessR6 Entry "r2-r5,r11"
        MOV     r3, r1
        MOV     r11, r6
        BL      MoveCAMatR0toR3         ; use old internal routine for now
        EXIT

; Same as above, but returns with r2 = page number of page that moved

MovePageAtR0ToR1WithAccessR6ReturnPageNumber Entry "r3-r5,r11"
        MOV     r3, r1
        MOV     r11, r6
        BL      MoveCAMatR0toR3         ; use old internal routine for now
        EXIT

; ***********************************************************************************
;
;       DynAreaHandler_SysHeap - Dynamic area handler for system heap
;       DynAreaHandler_RMA     - Dynamic area handler for RMA
;
; in:   r0 = reason code (0=>pre-grow, 1=>post-grow, 2=>pre-shrink, 3=>post-shrink)
;       r12 -> base of area
;

DynAreaHandler_SysHeap
DynAreaHandler_RMA ROUT
        CMP     r0, #4
        ADDCC   pc, pc, r0, LSL #2
        B       UnknownHandlerError
        B       PreGrow_Heap
        B       PostGrow_Heap
        B       PreShrink_Heap
        B       PostShrink_Heap

PostGrow_Heap
PostShrink_Heap
        STR     r4, [r12, #:INDEX:hpdend] ; store new size

; and drop thru to...

PreGrow_Heap
        CLRV                            ; don't need to do anything here
        MOV     pc, lr                  ; so just exit

PreShrink_Heap
        Push    "r0, lr"
        PHPSEI                          ; disable IRQs round this bit
        LDR     r0, [r12, #:INDEX:hpdbase]      ; get minimum size
        SUB     r0, r4, r0              ; r0 = current-minimum = max shrink
        CMP     r3, r0                  ; if requested shrink > max
        MOVHI   r3, r0                  ; then limit it
        SUB     r0, r5, #1              ; r0 = page mask
        BIC     r3, r3, r0              ; round size change down to page multiple
        SUB     r0, r4, r3              ; area size after shrink
        STR     r0, [r12, #:INDEX:hpdend] ; update size

        PLP                             ; restore IRQ status
        CLRV
        Pull    "r0, pc"

AreaName_RMA
        =       "Module area", 0
  [ LongCommandLines :LAND: (:LNOT: HAL)
AreaName_Kbuffs
        =       "Kernel buffers", 0
  ]
        ALIGN


UnknownHandlerError
        Push    "lr"
        ADRL    r0, ErrorBlock_UnknownAreaHandler
  [ International
        BL      TranslateError
  |
        SETV
  ]
        Pull    "pc"

DynAreaHandler_Sprites
        CMP     r0, #4
        ADDCC   pc, pc, r0, LSL #2
        B       UnknownHandlerError
        B       PreGrow_Sprite
        B       PostGrow_Sprite
        B       PreShrink_Sprite
        B       PostShrink_Sprite

PostGrow_Sprite
PostShrink_Sprite Entry "r0"

; in - r3 = size change (+ve), r4 = new size, r5 = page size

        LDR     lr, =ZeroPage+VduDriverWorkSpace
        TEQ     r4, #0                  ; if new size = 0
        STREQ   r4, [lr, #SpAreaStart]  ; then set area ptr to zero
        STRNE   r12, [lr, #SpAreaStart] ; else store base address

        LDR     r0, =ZeroPage
        LDR     lr, [r0, #SpriteSize]   ; load old size
        STR     r4, [r0, #SpriteSize]   ; and store new size
        BEQ     %FT10                   ; if new size is zero, don't try to update header

        STR     r4, [r12, #saEnd]       ; store new size in header
        TEQ     lr, #0                  ; if old size was zero
        STREQ   lr, [r12, #saNumber]    ; then initialise header (no. of sprites = 0)
        MOVEQ   lr, #saExten
        STREQ   lr, [r12, #saFirst]     ; ptr to first sprite -> after header
        STREQ   lr, [r12, #saFree]      ; ptr to first free byte -> after header

10
        CLRV                            ; don't need to do anything here
        EXIT                            ; so just exit

PreGrow_Sprite
        CLRV                            ; don't need to do anything here
        MOV     pc, lr                  ; so just exit

PreShrink_Sprite Entry "r0"
        TEQ     r4, #0                  ; if current size is zero
        BEQ     %FT10                   ; then any shrink is OK (shouldn't happen)

        LDR     r0, [r12, #saFree]      ; get used amount
        TEQ     r0, #saExten            ; if only header used,
        MOVEQ   r0, #0                  ; then none really in use

        SUB     r0, r4, r0              ; r0 = current-minimum = max shrink
        CMP     r3, r0                  ; if requested shrink > max
        MOVHI   r3, r0                  ; then limit it
        SUB     r0, r5, #1              ; r0 = page mask
        BIC     r3, r3, r0              ; round size change down to page multiple
10
        CLRV
        EXIT

AreaName_SpriteArea
        =       "System sprites", 0
        ALIGN


DynAreaHandler_RAMDisc
        CMP     r0, #4
        ADDCC   pc, pc, r0, LSL #2
        B       UnknownHandlerError
        B       PreGrow_RAMDisc
        B       PostGrow_RAMDisc
        B       PreShrink_RAMDisc
        B       PostShrink_RAMDisc

PostGrow_RAMDisc
PostShrink_RAMDisc Entry "r0-r6"

; in - r3 = size change (+ve), r4 = new size, r5 = page size
; but we don't really care about any of these

; The only thing we have to do here is ReInit RAMFS, but NOT if
; a) no modules are initialised yet (eg when we're created), or
; b) RAMFS has been unplugged

        LDR     r0, =ZeroPage
        LDR     r0, [r0, #Module_List]
        TEQ     r0, #0                  ; any modules yet?
        BEQ     %FT90                   ; no, then don't do anything

        MOV     r0, #ModHandReason_EnumerateROM_Modules
        MOV     r1, #0
        MOV     r2, #-1                 ; enumerate ROM modules looking for RAMFS
10
        SWI     XOS_Module
        BVS     %FT50                   ; no more modules, so it can't be unplugged
        ADR     r5, ramfsname
20
        LDRB    r6, [r3], #1            ; get char from returned module name
        CMP     r6, #" "                ; if a terminator then we have a match
        BLS     %FT30                   ; so check for unplugged
        LowerCase r6, lr                ; else force char to lower case
        LDRB    lr, [r5], #1            ; get char from "ramfs" string
        CMP     lr, r6                  ; and if matches
        BEQ     %BT20                   ; then try next char
        B       %BT10                   ; else try next module

30
        CMP     r4, #-1                 ; is module unplugged?
        BEQ     %FT90                   ; if so, then mustn't reinit it
50
        MOV     r0, #ModHandReason_ReInit ; reinit module
        ADR     r1, ramfsname
        SWI     XOS_Module              ; ignore any errors from this
90
        CLRV
        EXIT

PreGrow_RAMDisc
PreShrink_RAMDisc Entry "r0-r5"
        LDR     r0, =ZeroPage
        LDR     r0, [r0, #Module_List]  ; first check if any modules going
        TEQ     r0, #0
        BEQ     %FT90                   ; if not, don't look at filing system

        MOV     r0, #5
        ADR     r1, ramcolondollardotstar
        SWI     XOS_File
        CMPVC   r0, #0
        BVS     %FT90                   ; if no RAMFS then change OK
        BEQ     %FT90                   ; or if no files, then change OK
        ADR     r0, ErrorBlock_RAMFsUnchangeable
 [ International
        BL      TranslateError
 |
        SETV
 ]
        STR     r0, [sp]
        EXIT

90
        CLRV
        EXIT

        MakeErrorBlock  RAMFsUnchangeable

AreaName_RAMDisc
        =       "RAM disc", 0
ramcolondollardotstar
        =       "ram:$.*", 0
ramfsname
        =       "ramfs", 0
        ALIGN


DynAreaHandler_FontArea
        CMP     r0, #4
        ADDCC   pc, pc, r0, LSL #2
        B       UnknownHandlerError
        B       PreGrow_FontArea
        B       PostGrow_FontArea
        B       PreShrink_FontArea
        B       PostShrink_FontArea

PostGrow_FontArea Entry "r0-r2"

; in - r3 = size change (+ve), r4 = new size, r5 = page size

        LDR     r1, =ZeroPage
        LDR     r1, [r1, #Module_List]  ; any modules active?
        TEQ     r1, #0
        MOVNE   r1, r4                  ; there are, so inform font manager of size change
        SWINE   XFont_ChangeArea
        CLRV
        EXIT

PostShrink_FontArea
PreGrow_FontArea
        CLRV                            ; don't need to do anything here
        MOV     pc, lr                  ; so just exit

PreShrink_FontArea Entry "r0-r2"
        MOV     r1, #-1                 ; ask font manager for minimum size of font area
        MOV     r2, #0                  ; default value if no font manager
        SWI     XFont_ChangeArea        ; out: r2 = minimum size

        SUB     r0, r4, r2              ; r0 = current-minimum = max shrink
        CMP     r3, r0                  ; if requested shrink > max
        MOVHI   r3, r0                  ; then limit it
        SUB     r0, r5, #1              ; r0 = page mask
        BIC     r3, r3, r0              ; round size change down to page multiple

        SUB     r1, r4, r3              ; r1 = new size
        SWI     XFont_ChangeArea        ; tell font manager to reduce usage

        CLRV
        EXIT

AreaName_FontArea
        =       "Font cache", 0
        ALIGN


; **** New screen stuff ****
;
;
; This source collects together all the new routines needed to make
; the screen into a new dynamic area.
;
; It has the following dependencies elsewhere in the kernel before
; it can be expected to work:
;
; * Definition of AP_Screen in ChangeDyn needs doubly_mapped and
;   name_is_token bits set
; * name_is_token handling needs adding (or scrap the bit designation)
; * Call to CreateNewScreenArea from NewReset to create area
; * Tim says doubly-mapped areas are broken - this must be fixed first
; * Old CDA routine may be retired, since screen is its last client
; * Has Tim completed the rest of this work?
;
; Once these routines work, they should be grafted into appropriate
; places in the kernel sources
;
; This source is not intended for stand-alone assembly: it should be
; plumbed into the kernel source build
;
; Version history - remove this once integrated with kernel sources
;
; Vsn  Date      Who  What
; ---  --------  ---  ----------------------------------------------
; 000  23/08/93  amg  Written
; 001  24/08/93  amg  Fixes and changes following review by TMD
; 002  03/09/93  tmd  Updated to work!

; *********************************************************************
; Create a new style dynamic area for the screen
; *********************************************************************

; Entry requirements
; none

AreaName_Screen
        =       "Screen memory",0               ;needs replacing with message token
        ALIGN

; *********************************************************************
; Handler despatch routine for screen dynamic area
; *********************************************************************

DynAreaHandler_Screen                           ;despatch routine for pre/post grow/shrink handlers
        CMP     r0, #4
        ADDCC   pc, pc, R0, LSL #2
        B       UnknownHandlerError             ;already defined in ChangeDyn
        B       PreGrow_Screen                  ;the rest are defined here
        B       PostGrow_Screen
        B       PreShrink_Screen
        B       PostShrink_Screen

;The sequence of events which these handlers must do is:
;
;Grow Screen
;
;Pre : Remove cursors
;      Work out which physical page numbers are needed and return a list
;CDA : Move existing pages lower in memory within first copy (ie change logical address
;        associated with physical pages)
;      Locate and free the next physical pages in line (if used a page swap must occur)
;      Assign the new pages logical addresses in the gap between the end of the present
;        logical range and the start of the second physical range
;Post: Adjust screen memory contents & screen start addresses to retain screen display
;
;Shrink Screen
;
;Pre : Remove cursors
;      Adjust screen memory contents & screen start addresses to retain screen display
;CDA : Move pages from screen to free pool (creates a gap in first logical range)
;      Close up the gap in logical addressing
;Post: Restore cursors
;

; ***********************************************************************************
; Handlers for the screen dynamic area
; ***********************************************************************************

;Pregrow entry parameters
; R0 = 0 (reason code)
; R1 -> page block (entries set to -1)
; R2 = number of entries in page block == number of pages area is growing by
; R3 = number of bytes area is growing by (r2 * pagesize)
; R4 = current size (bytes)
; R5 = page size
;
; exit with V clear, all preserved

PreGrow_Screen  Entry   "r0-r2,r4"
        LDR     r0, [WsPtr, #CursorFlags]       ; test if VDU inited yet
        LDRB    lr, [WsPtr, #ExternalFramestore]
        TEQ     r0, #0                          ; if not, CursorFlags will be zero
        BEQ     %FT05
        TEQ     lr, #0
        SWIEQ   XOS_RemoveCursors               ; if VDU inited, then remove cursors

05      ADRL    r0, PageShifts-1
        LDRB    r0, [r0, r5, LSR #12]           ; grab log2Pagesize for shifting
        MOV     r4, r4, LSR r0                  ; change present size into number of pages
                                                ; since page numbers are 0 to n-1 thus n
                                                ; is the first page number we want to insist on
10
        STR     r4, [r1], #12                   ; store physical page number and increment to next
        SUBS    r2, r2, #1                      ; one less to do
        ADDNE   r4, r4, #1                      ; next physical page number
        BNE     %BT10                           ; continue until all pages done
        CLRV                                    ; ok, so I'm paranoid...
        EXIT

; **********************************************************************

;PostGrow entry parameters
;R0 = 1 (reason code)
;R1 -> page block (only physical page numbers are meaningful)
;R2 = number of entries in page block (= number of pages area grew by)
;R3 = number of bytes area grew by
;R4 = new size of area (bytes)
;R5 = page size

PostGrow_Screen Entry   "r0,r5"
        LDR     r0, [WsPtr, #CursorFlags]       ; test if VDU inited (CursorFlags=0 => not)
        TEQ     r0, #0
        BEQ     %FT90                           ; if not inited, do nothing

        PHPSEI  r5                              ; disable IRQs

        MOV     r0, r3                          ; move number of bytes area grew by into r0
        BL      InsertPages                     ; only call InsertPages if VDU inited

        PLP     r5                              ; restore IRQ state
        SWI     XOS_RestoreCursors              ; and restore cursors
90
        CLRV
        EXIT

; ***********************************************************************

;PreShrink Entry parameters
;R0 = 2 (reason code)
;R3 = number of bytes area is shrinking by
;R4 = current size of area (bytes)
;R5 = page size
;R12 = vdu workspace

PreShrink_Screen Entry   "R0-R2,R4-R5"

        ;need to check whether the proposed shrink still leaves enough for
        ;the current amount needed by the vdu drivers, if it doesn't we
        ;reduce R3 to be the most we can spare (in whole pages)

 [ HAL
        LDR     LR, =ZeroPage
        LDR     LR, [LR, #VideoSizeFlags]          ;is VRAM suitable for general use?
        TST     LR, #OSAddRAM_VRAMNotForGeneralUse ;if not - don't shrink screen memory
        MOVNE   R3, #0
 ]
        SUB     R2, R5, #1                      ;make a page mask

        LDRB    R14, [R12, #ExternalFramestore]
        TEQ     R14, #0                         ;okay to shrink if using external framestore
        BEQ     %FT12
        RSB     R0, R3, #0                      ;R0= -(number of bytes) for RemovePages
        BL      RemovePages
        CLRV
        EXIT

12      LDR     R5, [R12, #ScreenSize]          ;get current minimum size

        SUB     R1, R4, R5                      ;R1 = maximum shrink (current - screensize)
        CMP     R3, R1                          ;if requested shrink > max...
        MOVHI   R3, R1                          ;...then limit it, and...
        BICS    R3, R3, R2                      ;...round down to multiple of page size
        BEQ     %FT10                           ;don't shuffle screen data if resultant
                                                ;shrink is 0 bytes/0 pages
        SWI     XOS_RemoveCursors
        PHPSEI  R5                              ;disable interrupts
        RSB     R0, R3, #0                      ;R0= -(number of bytes) for RemovePages
        BL      RemovePages                     ;entry: R0 = -(number of bytes)
        PLP     R5                              ;restore interrupts
10
        CLRV
        EXIT

; ************************************************************************

;PostShrink Entry parameters
;R0 = 3 (reason code)
;R3 = number of bytes area shrank by
;R4 = new size of area (bytes)
;R5 = page size

PostShrink_Screen Entry
        SWI     XOS_RestoreCursors
        CLRV                                    ;ok, so I'm paranoid...
        EXIT

; ************************************************************************

        LTORG

        END