; 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.
;
; > s.memmap
; low level memory mapping
;
; ----------------------------------------------------------------------------------
;
;convert page number in $pnum to L2PT entry (physical address+protection bits),
;using PhysBin table for speed
;
;entry: $ptable -> PhysBin table, $pbits = protection bits
;exit: $temp corrupted
;
MACRO
PageNumToL2PT $pnum,$ptable,$pbits,$temp
BIC $temp,$pnum,#(3:SHL:(AMBPhysBinShift-2)) ;word alignment for PhysBin lookup
LDR $temp,[$ptable,$temp,LSR #(AMBPhysBinShift-2)] ;start physical address of bin
AND $pnum,$pnum,#AMBPhysBinMask ;no. pages into bin
ADD $pnum,$temp,$pnum,LSL #Log2PageSize ;physical address of page
ORR $pnum,$pnum,$pbits ;munge in protection bits
MEND
[ AMB_LazyMapIn
; ----------------------------------------------------------------------------------
;
;AMB_LazyFixUp
;
; *Only* for ARMs where the abort handler can restart instructions
;
; Routine to be used in abort handlers (in abort32 mode), that checks to see if abort
; is expected, and fixes things up if so, ready to restart instruction.
;
; Fix up consists of mapping in affected page, and updating AMBMappedInRegister. This
; may seem like a lot of work, but remember that the L2PT and CAM updates for each page are
; needed anyway in non-lazy scheme, so there is really only a housekeeping overhead.
;
; There is no cache clean/flush consideration here, since the map is a map in from Nowhere.
; TLB flush consideration is left to main abort handler code - in fact there may not
; be a TLB flush consideration at all, if ARM TLB can be assumed not to cache an
; entry which is a translation fault, as seems rational.
;
; entry: r0 = aborting address (data address for data abort, instruction address
; for prefetch abort), r1-r7 trashable, no stack
; r2 = 1 for prefetch abort, 0 for data abort
; FSR valid for data aborts, unpredictable for prefetch aborts
; exit: r0 = non-zero (NE status) if abort was expected and fixed up, zero (EQ status) if not
; FAR,FSR,SPSR_abt,lr_abt preserved
;
AMB_LazyFixUp ROUT
MOV r7,r12
LDR r12,=ZeroPage+AMBControl_ws
LDR r12,[r12]
CMP r12,#0
BEQ %FT90 ;not initialised!
LDR r1,AMBFlags
TST r1,#AMBFlag_LazyMapIn_disable :OR: AMBFlag_LazyMapIn_suspend
BNE %FT90 ;not active
LDR r1,AMBMappedInNode
CMP r1,#0
BEQ %FT90 ;no current node
ARM_read_FSR r6 ;hang onto FSR in case we have to preserve it
TEQ r2,#1 ;if data abort
ANDNE r3,r6,#&F
TEQNE r3,#7 ; and not a page translation fault
BNE %FT20 ; then not a lazy abort (and FAR may be invalid anyway)
LDR r2,[r1,#AMBNode_Npages]
SUBS r0,r0,#ApplicationStart
BLO %FT20 ;abort not in current app space
MOV r0,r0,LSR #Log2PageSize ;address now in terms of pages from ApplicationStart
CMP r0,r2
BHS %FT20 ;abort not in current app space
;
; check/update the MappedIn bitmap
;
ADR r2,AMBMappedInRegister
MOV r5,#1
ADD r2,r2,r0,LSR #5-2
BIC r2,r2,#3 ;r2 -> bitmap word affected
AND r3,r0,#31
MOV r5,r5,LSL r3 ;mask for bit affected in bitmap word
LDR r3,[r2]
LDR r4,AMBMappedInNpages ;count it
TST r3,r5 ;if page already mapped in, not a lazy abort
BNE %FT20
ORR r3,r3,r5 ;ok, mark that we are going to map this page in
STR r3,[r2]
ADD r4,r4,#1
STR r4,AMBMappedInNpages
;
; now map in the the page that went pop
;
ADD r1,r1,#AMBNode_pages
ADD r1,r1,r0,LSL #2 ;r1 -> page involved, in node page list
LDR r2,AMBPhysBin
; Calculate the L2PT protection bits in a nice way that won't produce broken code if we change MMU model
; This should match the AP_Full entry from the PPLTrans table that gets used by BangCam (plus C+B bits)
[ MEMM_Type = "VMSAv6"
MOV r3,#(AP_Full*L2X_APMult)+L2_ExtPage+L2_C+L2_B
|
ASSERT (AP_Full*L2_APMult)+L2_SmallPage+L2_C+L2_B = &FFE
MOV r3,#&FF0
ORR r3,r3,#&E
]
LDR r4,[r1]
MOV r6,r4
PageNumToL2PT r4,r2,r3,r5
;
;here, r6 = page number of page involved, r4 = new L2PT entry value to map in page
;
ADD r0,r0,#ApplicationStart:SHR:Log2PageSize ;address now in terms of pages from 0
MOV r5,#L2PT
STR r4,[r5,r0,LSL #2] ;update L2PT
;
LDR r5,=ZeroPage
LDR r5,[r5,#CamEntriesPointer]
ADD r5,r5,r6,LSL #3 ;r5 -> CAM entry affected
MOVS r0,r0,LSL #Log2PageSize ;address is now ordinary again, and must be non-zero
MOV r1,#0 ;0 = AP for ordinary page
STMIA r5,{r0,r1} ;update CAM entry
MOV r12,r7
MOV pc,lr ;r0 is non-zero, NE status
;
; not our abort, but is possible that client abort handler is in app space, so force all
; app space pages in now (so that client abort handler does not cause lazy abort, scribbling over original abort details)
;
ASSERT No26bitCode ;assumes we have an abort stack! (recursive lazy fixup aborts may occur)
20
MOV r1,#ApplicationStart ;good old page walk to provoke lazy fixups
LDR r2,AMBMappedInNode
LDR r2,[r2,#AMBNode_Npages]
CMP r2,#0
BEQ %FT90
MRS r0,SPSR ;preserve SPSR_abort for original abort details
MOV r4,lr ;preserve lr_abort so we can return properly (!)
ARM_read_FAR r5 ;preserve FAR in case client abort handler wants to read it
;preserve FSR (already in r6) similarly
30
LDR r3,[r1] ;bring that page in by the magic of aborts
SUBS r2,r2,#1
ADD r1,r1,#PageSize
BNE %BT30
MSR SPSR_cxsf,r0 ;SPSR for original abort
MOV lr,r4 ;restore return address
ARM_write_FAR r5 ;restore FAR
ARM_write_FSR r6 ;restore FSR
[ MEMM_Type = "VMSAv6"
myISB ,r0 ; Not sure if this is necessary or not; do it just in case
]
;
90
MOVS r0,#0
MOV r12,r7
MOV pc,lr ;r0 is zero, EQ status
] ;AMB_LazyMapIn
; ----------------------------------------------------------------------------------
[ AMB_LazyMapIn
;
; If page of given logical address (r0) is in current app space, make sure page is
; 'honest' ie. properly mapped in. This is for things like FindMemMapEntries
; that must return sensible info (and presumably their client needs a consistent
; view of app space mapping, so that laziness is transparent)
;
AMB_MakeHonestLA ROUT
CMP r0,#AbsMaxAppSize ;quick dismiss if definitely not app address
MOVHS pc,lr
Push "r1,r12,lr"
LDR r12,=ZeroPage+AMBControl_ws
LDR r12,[r12]
CMP r12,#0
BEQ %FT90 ;we're dormant!
SUBS r14,r0,#ApplicationStart
BMI %FT90 ;below app space
MOV r14,r14,LSR #Log2PageSize ;pages from ApplicationStart
LDR r1,AMBMappedInNode
CMP r1,#0
BEQ %FT90 ;no node mapped in
LDR r1,[r1,#AMBNode_Npages]
CMP r1,r14 ;HI if log addr is in current app space
LDRHI r1, [r0,#0] ;make honest if necessary (magic of abort fixups!)
90
Pull "r1,r12,pc"
; similar to AMB_MakeHonestLA, but for page of given page number (r0)
;
AMB_MakeHonestPN ROUT
Push "r1-r3,r12,lr"
LDR r12,=ZeroPage+AMBControl_ws
LDR r12,[r12]
CMP r12,#0
BEQ %FT90 ;we're dormant!
LDR r14,=ZeroPage
LDR r1,[r14,#MaxCamEntry]
CMP r0,r1
BHI %FT90 ;invalid page number
LDR r1,[r14,#CamEntriesPointer]
LDR r1,[r1,r0,LSL #3] ;logical address from CAM
LDR r14,=Nowhere
TEQ r1,r14
BNE %FT90 ;only a page at Nowhere might be dishonest
LDR r1,AMBMappedInNode ;let's check the current node
CMP r1,#0
BEQ %FT90 ;no node mapped in
LDR r14,[r1,#AMBNode_Npages]
MOV r14,r14,LSL #Log2PageSize
ADD r14,r14,#ApplicationStart ;top of current app space
ADD r1,r1,#AMBNode_pages ;[r1] is page number
MOV r2,#ApplicationStart ;r2 is logical address for page
10
CMP r2,r14
BHS %FT90
LDR r3,[r1],#4 ;next page number in node
TEQ r3,r0 ;see if its the one that wants to be honest
ADDNE r2,r2,#PageSize ;next logical address
BNE %BT10
LDR r1,[r2,#0] ;make honest if necessary (magic of abort fixups!)
90
Pull "r1-r3,r12,pc"
] ;AMB_LazyMapIn
; ----------------------------------------------------------------------------------
;
;AMB_movepagesin_L2PT
;
;updates L2PT for new logical page positions, does not update CAM
;
; entry:
; r3 = new logical address of 1st page
; r8 = number of pages
; r10 -> page list
; r11 = protection/control bits for L2PT
;
AMB_movepagesin_L2PT ROUT
Push "r0-r10,r12,lr"
LDR lr,AMBPhysBin ;lr -> PhysBin
LDR r9,=L2PT
ADD r9,r9,r3,LSR #(Log2PageSize-2) ;r9 -> L2PT for 1st new logical page
CMP r8,#8
BLT %FT20
10
LDMIA r10!,{r0-r7} ;next 8 page numbers
PageNumToL2PT r0,lr,r11,r12
PageNumToL2PT r1,lr,r11,r12
PageNumToL2PT r2,lr,r11,r12
PageNumToL2PT r3,lr,r11,r12
PageNumToL2PT r4,lr,r11,r12
PageNumToL2PT r5,lr,r11,r12
PageNumToL2PT r6,lr,r11,r12
PageNumToL2PT r7,lr,r11,r12
STMIA r9!,{r0-r7} ;write 8 L2PT entries
SUB r8,r8,#8
CMP r8,#8
BGE %BT10
20
CMP r8,#0
BEQ %FT35
30
LDR r0,[r10],#4
PageNumToL2PT r0,lr,r11,r12
STR r0,[r9],#4
SUBS r8,r8,#1
BNE %BT30
35
Pull "r0-r10,r12,pc"
; ----------------------------------------------------------------------------------
;
;update CAM entry for page number in $reg
;
;entry: r11 -> CAM, r9 = logical addr of page, lr = PPL of page
;exit: $reg = addr of CAM entry
;
MACRO
UpdateCAM $reg
ADD $reg,r11,$reg,LSL #3 ;r0 -> CAM entry for 1st page
STMIA $reg,{r9,lr} ;store logical addr,PPL
MEND
; ----------------------------------------------------------------------------------
;
;AMB_movepagesin_CAM
;
;updates CAM, does not update L2PT
;
; entry:
; r3 = new logical address of 1st page
; r8 = number of pages
; r9 = PPL for CAM
; r10 -> page list
;
AMB_movepagesin_CAM ROUT
Push "r0-r11,lr"
MOV lr,r9
MOV r9,r3
LDR r11,=ZeroPage
LDR r11,[r11,#CamEntriesPointer] ;r11 -> CAM
CMP r8,#8
BLT %FT20
10
LDMIA r10!,{r0-r7} ;next 8 page numbers
UpdateCAM r0
ADD r9,r9,#PageSize ;next logical addr
UpdateCAM r1
ADD r9,r9,#PageSize
UpdateCAM r2
ADD r9,r9,#PageSize
UpdateCAM r3
ADD r9,r9,#PageSize
UpdateCAM r4
ADD r9,r9,#PageSize
UpdateCAM r5
ADD r9,r9,#PageSize
UpdateCAM r6
ADD r9,r9,#PageSize
UpdateCAM r7
ADD r9,r9,#PageSize
SUB r8,r8,#8
CMP r8,#8
BGE %BT10
20
CMP r8,#0
Pull "r0-r11,pc",EQ
30
LDR r0,[r10],#4
UpdateCAM r0
ADD r9,r9,#PageSize
SUBS r8,r8,#1
BNE %BT30
Pull "r0-r11,pc"
; ----------------------------------------------------------------------------------
;
;AMB_movepagesout_CAM
;
;updates CAM, does not update L2PT
;
; entry:
; r8 = number of pages
; r9 = PPL for CAM
; r10 -> page list
;
AMB_movepagesout_CAM ROUT
Push "r0-r11,lr"
MOV lr,r9
LDR r9,=DuffEntry
LDR r11,=ZeroPage
LDR r11,[r11,#CamEntriesPointer] ;r11 -> CAM
CMP r8,#8
BLT %FT20
10
LDMIA r10!,{r0-r7} ;next 8 page numbers
UpdateCAM r0
UpdateCAM r1
UpdateCAM r2
UpdateCAM r3
UpdateCAM r4
UpdateCAM r5
UpdateCAM r6
UpdateCAM r7
SUB r8,r8,#8
CMP r8,#8
BGE %BT10
20
CMP r8,#0
Pull "r0-r11,pc",EQ
30
LDR r0,[r10],#4
UpdateCAM r0
SUBS r8,r8,#1
BNE %BT30
Pull "r0-r11,pc"
; ----------------------------------------------------------------------------------
;
;AMB_movepagesout_L2PT
;
;updates L2PT for old logical page positions, does not update CAM
;
; entry:
; r4 = old logical address of 1st page
; r8 = number of pages
;
AMB_movepagesout_L2PT ROUT
Push "r0-r8,lr"
LDR lr,=L2PT
ADD lr,lr,r4,LSR #(Log2PageSize-2) ;lr -> L2PT 1st entry
MOV r0,#0 ;0 means translation fault
MOV r1,#0
MOV r2,#0
MOV r3,#0
MOV r4,#0
MOV r5,#0
MOV r6,#0
MOV r7,#0
CMP r8,#8
BLT %FT20
10
STMIA lr!,{r0-r7} ;blam! (8 entries)
SUB r8,r8,#8
CMP r8,#8
BGE %BT10
20
CMP r8,#0
BEQ %FT35
30
STR r0,[lr],#4
SUBS r8,r8,#1
BNE %BT30
35
Pull "r0-r8,pc"
; ----------------------------------------------------------------------------------
;
; AMB_SetMemMapEntries:
;
; entry:
; R3 = no. of pages
; R4 -> list of page entries (1 word per entry, giving page no.)
; R5 = start logical address of mapping (-1 means 'out of the way')
; R6 = PPL ('page protection level') for mapping
;
AMB_SetMemMapEntries ROUT
Push "r0-r4,r7-r11,lr"
MOVS r8,r3
BEQ AMB_smme_exit
CMP r5,#-1
MOVEQ r9,#AP_Duff ;PPL for mapped out pages
MOVNE r9,r6 ;PPL for mapped in pages
;get L2PT protection etc. bits, appropriate to PPL in R9, into R11
ADRL r1,PPLTrans
AND lr,r9,#3
LDR r11,[r1,lr,LSL #2]
TST r9,#DynAreaFlags_NotCacheable
TSTEQ r9,#PageFlags_TempUncacheableBits
ORREQ r11,r11,#L2_C ;if cacheable (area bit CLEAR + temp count zero), then OR in C bit
TST r9,#DynAreaFlags_NotBufferable
ORREQ r11,r11,#L2_B ;if bufferable (area bit CLEAR), then OR in B bit
MOV r10,r4 ;ptr to next page number
LDR r2,[r10] ;page number of 1st page
LDR r7,=ZeroPage
LDR r7,[r7,#CamEntriesPointer] ;r7 -> CAM
ADD r1,r7,r2,LSL #3 ;r1 -> CAM entry for 1st page
[ AMB_LimpidFreePool
LDR r4,[r1] ;fetch old logical addr. of 1st page from CAM
LDR r3,[r1,#4] ;fetch old PPL of 1st page from CAM
|
LDR r4,[r1] ;fetch old logical addr. of 1st page from CAM
]
CMP r5,#-1
BEQ AMB_smme_mapout
;map or mapin
LDR r1,=DuffEntry
CMP r4,r1
BEQ AMB_smme_mapin
;map from somewhere to somewhere (should be App Space <-> Free Pool)
;
[ AMB_LimpidFreePool
;can avoid cache clean/flush for moving pages out from FreePool, since FreePool pages are uncacheable
;
TST r3, #DynAreaFlags_NotCacheable ;test PPL of 1st page for not cacheable bit set
BEQ AMB_smme_mapnotlimpid ;if clear, must do full map somewhere with cache clean/flush
;
;this should be map FreePool -> App Space then
;
MOV r0,r4 ;address of 1st page
MOV r1,r8 ;number of pages
LDR r3,=ZeroPage
ARMop MMU_ChangingUncachedEntries,,,r3 ;no cache worries, hoorah
MOV r3,r5
BL AMB_movepagesout_L2PT ;unmap 'em from where they are
BL AMB_movepagesin_L2PT ;map 'em to where they now be
BL AMB_movepagesin_CAM ;keep the bloomin' soft CAM up to date
Pull "r0-r4,r7-r11, pc"
AMB_smme_mapnotlimpid
]
;
MOV r0,r4 ;address of 1st page
MOV r1,r8 ;number of pages
LDR r3,=ZeroPage
ARMop MMU_ChangingEntries,,,r3 ;
MOV r3,r5
BL AMB_movepagesout_L2PT
BL AMB_movepagesin_L2PT
BL AMB_movepagesin_CAM
Pull "r0-r4,r7-r11, pc"
;all pages sourced from same old logical page Nowhere, ie. pages currently mapped out, no cache worries
;
AMB_smme_mapin
MOV r0,r4 ;address of 1st page
MOV r1,r8 ;number of pages
LDR r3,=ZeroPage
ARMop MMU_ChangingUncachedEntries,,,r3 ;TLB coherency, possibly not needed (TLBs shouldn't cache 0 entries)
MOV r3,r5
BL AMB_movepagesin_L2PT
BL AMB_movepagesin_CAM
Pull "r0-r4,r7-r11, pc"
;all pages destined for same new logical page Nowhere, ie. mapping them out
;
AMB_smme_mapout
MOV r0,r4 ;address of 1st page
MOV r1,r8 ;number of pages
LDR r3,=ZeroPage
ARMop MMU_ChangingEntries,,,r3 ;
LDR r3,=DuffEntry
BL AMB_movepagesout_L2PT
BL AMB_movepagesout_CAM
AMB_smme_exit
Pull "r0-r4,r7-r11, pc"
[ AMB_LazyMapIn
; ----------------------------------------------------------------------------------
;
; AMB_SetMemMapEntries_SparseMapOut:
;
;
; entry:
; R3 = no. of pages currently mapped in (0=none)
; R4 -> list of page entries (1 word per entry, giving page no.)
; R5 -> bitmap of pages mapped in (1 bit per page in whole page list)
; R6 = total no. of pages in slot
;
AMB_SetMemMapEntries_SparseMapOut ROUT
CMP r3,#0
MOVEQ pc,lr
Push "r0-r11,lr"
MOV r10,r4 ;ptr to page list
LDR r2,=ZeroPage
MOV r9,#AP_Duff ;permissions for DuffEntry
LDR r7,[r2,#CamEntriesPointer] ;r7 -> CAM
MOV r4,#ApplicationStart ;log. address of first page
LDR r1,=DuffEntry ;means Nowhere, in CAM
;if the number of pages mapped in is small enough, we'll do cache/TLB coherency on
;just those pages, else global (performance decision, threshold probably not critical)
ARMop Cache_RangeThreshold,,,r2 ;returns threshold (bytes) in r0
CMP r3,r0,LSR #Log2PageSize
MOVLO r6,#0 ;r6 := 0 if we are to do coherency as we go
BLO %FT10 ;let's do it
ARMop MMU_Changing,,,r2 ;global coherency
B %FT10
;skip next 32 pages then continue
06
ADD r10,r10,#32*4
ADD r4,r4,#32*PageSize
;find the sparsely mapped pages, map them out, doing coherency as we go if enabled
10
MOV r8,#1 ;initial bitmap mask for new bitmap word
LDR r11,[r5],#4 ;next word of bitmap
CMP r11,#0 ;if next 32 bits of bitmap clear, skip
BEQ %BT06 ;skip loop must terminate if r3 > 0
12
TST r11,r8 ;page is currently mapped in if bit set
BEQ %FT16
TEQ r6, #0
BNE %FT14 ;check for coherency as we go
LDR r2,=ZeroPage
MOV r0,r4 ;address of page
ARMop MMU_ChangingEntry,,,r2
14
LDR r0,[r10] ;page no.
ADD r0,r7,r0,LSL #3 ;r0 -> CAM entry for page
STMIA r0,{r1,r9} ;CAM entry for page set to DuffEntry,AP_Duff
LDR lr,=L2PT ;lr -> L2PT
MOV r2, #0
STR r2,[lr,r4,LSR #(Log2PageSize-2)] ;L2PT entry for page set to 0 (means translation fault)
SUBS r3,r3,#1
STREQ r2,[r5,#-4] ;make sure we clear last word of bitmap, and...
BEQ %FT20 ;done
16
ADD r10,r10,#4 ;next page no.
ADD r4,r4,#PageSize ;next logical address
MOVS r8,r8,LSL #1 ;if 32 bits processed...
BNE %BT12
MOV r2, #0
STR r2,[r5,#-4] ;zero word of bitmap we've just traversed
LDR r2,=ZeroPage
B %BT10
20
Pull "r0-r11,pc"
; ----------------------------------------------------------------------------------
;
; AMB_MakeUnsparse
;
; entry: r0 = size of area (at top of current slot) to ensure is not sparsely mapped
;
; action: walk over space involved, to force abort handler fix up to map in any
; pages not already there
;
AMB_MakeUnsparse ROUT
Push "r0-r2,r12,lr"
; Debug AMB,"AMB_MakeUnsparse r0",r0
ADD r0,r0,#PageSize
SUB r0,r0,#1
MOVS r0,r0,LSR #Log2PageSize
BEQ %FT20
LDR r12,=ZeroPage+AMBControl_ws
LDR r12,[r12]
CMP r12,#0
BEQ %FT20
LDR r1,AMBMappedInNode
CMP r1,#0
BEQ %FT20
LDR r2,AMBFlags
TST r2,#AMBFlag_LazyMapIn_disable :OR: AMBFlag_LazyMapIn_suspend
BNE %FT20
[ AMB_ChocTrace
LDR r2,AMBNmakeunsparse
ADD r2,r2,#1
STR r2,AMBNmakeunsparse
]
LDR r2,[r1,#AMBNode_Npages]
; Debug AMB,"AMB_MakeUnsparse pages Npages ",r0,r2
CMP r0,r2
MOVHI r0,r2
SUB lr,r2,r0
MOV lr,lr,LSL #Log2PageSize
ADD lr,lr,#ApplicationStart
; Debug AMB,"AMB_MakeUnsparse MappedInNode addr pages ",r1,lr,r0
10
LDR r2,[lr] ;tends to wash data cache a bit, but this should be called rarely
ADD lr,lr,#PageSize
SUBS r0,r0,#1
BNE %BT10
20
Pull "r0-r2,r12,pc"
] ;AMB_LazyMapIn
; ----------------------------------------------------------------------------------
;
; AMB_FindMemMapEntries
;
; finds page numbers for pages currently at given logical start address,
; and fills in buffer; pages must exist
;
; (does not have any page number guesses)
;
; entry:
; R3 = no. of pages
; R4 -> buffer for page entries
; R5 = logical address of 1st page
; exit:
; buffer at R4 filled in with page numbers
;
AMB_FindMemMapEntries ROUT
Push "r0-r11,lr"
;initialise r0,r1,r2 as physical RAM chunk cache for AMB_r11topagenum routine
LDR r9,=ZeroPage+PhysRamTable
LDMIA r9,{r0,r1} ;r0,r1 := phys addr,size of chunk
ADD r1,r1,r0 ;r0,r1 := lowest addr,highest addr + 1 of chunk
MOV r2,#0 ;r2 := first page number of chunk
LDR r10,=L2PT
ADD r10,r10,r5,LSR #(Log2PageSize-2) ;r10 -> L2 entry for 1st page
CMP r3,#4 ;handle pages in chunks of 4
BLT %FT20
10
LDMIA r10!,{r5-r8} ;next 4 L2PT entries
MOV r11,r5,LSR #Log2PageSize ;r11 := phys_addr/page_size
BL AMB_r11topagenum
MOV r5,r11
MOV r11,r6,LSR #Log2PageSize
BL AMB_r11topagenum
MOV r6,r11
MOV r11,r7,LSR #Log2PageSize
BL AMB_r11topagenum
MOV r7,r11
MOV r11,r8,LSR #Log2PageSize
BL AMB_r11topagenum
STMIA r4!,{r5-r7,r11} ;fill in next 4 page numbers
SUB r3,r3,#4
CMP r3,#4
BGE %BT10
20
CMP r3,#0
Pull "r0-r11,pc",EQ
30
LDR r11,[r10],#4
MOV r11,r11,LSR #Log2PageSize
BL AMB_r11topagenum
STR r11,[r4],#4
SUBS r3,r3,#1
BNE %BT30
Pull "r0-r11,pc"
; ----------------------------------------------------------------------------------
;
;AMB_r11topagenum
;entry:
; r0,r1,r2 = lowest addr,highest addr +1,first page no.
; (cached physical RAM chunk)
; r11 = physical_addr/page_size for page
;
;exit:
; r11 = page number of page
; r0,r1,r2 cache updated if necessary
; r9 corrupted
;
AMB_r11topagenum ROUT
CMP r11,r0,LSR #Log2PageSize
BLO %FT10
CMP r11,r1,LSR #Log2PageSize
BHS %FT10
;cache hit (phys address in range of cached chunk)
SUB r11,r11,r0,LSR #Log2PageSize ;pages into chunk
ADD r11,r11,r2 ;page number
MOV pc,lr
10
LDR r9,=ZeroPage+PhysRamTable
MOV r2,#0 ;start at page number 0
20
LDMIA r9!,{r0,r1} ;r0,r1 := phys addr,size of chunk
SUB r11,r11,r0,LSR #Log2PageSize
CMP r11,r1,LSR #Log2PageSize
ADDHS r11,r11,r0,LSR #Log2PageSize
ADDHS r2,r2,r1,LSR #Log2PageSize
BHS %BT20
ADD r1,r1,r0
ADD r11,r11,r2
MOV pc,lr
LTORG
END