Build kernel using relocatable AOF

* Add KernelBaseA absolute symbol.
* Use KernelBase - KernelBaseA to convert some expressions
  to/from AREA relative form.
* Link to correct address.
* Remove ORG directive
* Move EndOfKernel to separate AREA

Makefile

@@ -89,8 +89,9 @@ install: ${EXPORTS} inst_dirs
 
 ${KERNEL_MODULE}: ${ROM_OBJECT} ${DIRS}
 	${MKDIR} bin
-	${LD} -bin -o $@ ${ROM_OBJECT}
-	${LD} -aif -bin -d -o ${KERNEL_MODULE}_aif ${ROM_OBJECT}
+	SetEval KernelBase "4" + STR ( 227858432 + ( HALSize LEFT ( LEN HALSize - 1 ) ) * 1024 )
+	Do ${LD} -bin -base <KernelBase> -o $@ ${ROM_OBJECT}
+	Do ${LD} -aif -base <KernelBase> -bin -d -o ${KERNEL_MODULE}_aif ${ROM_OBJECT}
 	${TOGPA} -s ${KERNEL_MODULE}_aif ${KERNEL_MODULE}_gpa
 
 #

s/GetAll

@@ -175,6 +175,7 @@ EndOfAMB
 
         ! 0, "AMB section size = &" :CC: :STR: (EndOfAMB - StartOfAMB)
 
+        AREA    zzzzzz, DATA, READONLY
 EndOfKernel
         DCD     0
 

s/Kernel

@@ -298,12 +298,12 @@ CBack_VectorReq * 4
         SUBT    Arthur Code
         OPT     4
 
-        ORG     ROM + OSROM_HALSize
-
         AREA    |!!!!OSBase|,CODE,READONLY
 
         ENTRY                   ; Not really, but we need it to link
 KernelBase
+KernelBaseA     *       ROM + OSROM_HALSize
+ToRelative      *       KernelBase - KernelBaseA
 
 ; *****************************************************************************
 ;
@@ -320,7 +320,7 @@ RISCOS_Header
         DCD     (RISCOS_Entries_End - RISCOS_Entries) / 4
         DCD     OSROM_ImageSize*1024 - OSROM_HALSize
         DCD     0
-        DCD     EndOfKernel - RISCOS_Header
+        DCD     EndOfKernel - KernelBaseA
         ASSERT  (. - RISCOS_Header) = OSHdr_size
 
 RISCOS_Entries
@@ -428,19 +428,19 @@ EndData
 
 SVCDespatcher ROUT
 
-SWIRelocation * SVCDespatcher-SWIDespatch
+SWIRelocation * SVCDespatcher - ToRelative - SWIDespatch
 
 SLVK_SetV * {PC}-SWIRelocation
 
         ORR     lr, lr, #V_bit
 
 SLVK_TestV * {PC}-SWIRelocation
- ! 0,"SLVK_TestV at ":CC:(:STR:SLVK_TestV)
+ ! 0,"SLVK_TestV at ":CC:(:STR:(SLVK_TestV - ToRelative))
 
         ORRVS   lr, lr, #V_bit
 
 SLVK * {PC}-SWIRelocation
- ! 0,"SLVK       at ":CC:(:STR:SLVK)
+ ! 0,"SLVK       at ":CC:(:STR:(SLVK - ToRelative))
 Local_SLVK
 
         LDR     r12, [sp], #4
@@ -456,7 +456,7 @@ Local_SLVK
         BNE     %FT50
 
 SWIReturnWithCallBackFlag * {PC}-SWIRelocation
- ! 0,"SWIReturnWithCallBackFlag at ":CC:(:STR:SWIReturnWithCallBackFlag)
+ ! 0,"SWIReturnWithCallBackFlag at ":CC:(:STR:(SWIReturnWithCallBackFlag - ToRelative))
 
 40      TEQ     r11, #0
 
@@ -467,7 +467,7 @@ SWIReturnWithCallBackFlag * {PC}-SWIRelocation
 
         B       callback_checking + SWIRelocation
 
- ! 0,"VSetReturn at ":CC:(:STR:({PC}-SWIRelocation))
+ ! 0,"VSetReturn at ":CC:(:STR:({PC} - SWIRelocation - ToRelative))
 50
         ; Some programs abuse XOS_GenerateError by using it purely as a method
         ; to trigger callbacks, or to convert null terminated strings to BASIC
@@ -687,7 +687,7 @@ JTABLE  & SWIWriteC
 ; The fudge branch to exit a dirty SWI handler
 
 DirtyBranch
-        B       SLVK +DirtyBranch-BranchToSWIExit
+        B       SLVK + DirtyBranch - ToRelative - BranchToSWIExit
 
 ; +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 

s/vdu/vdu5

@@ -168,7 +168,7 @@ Vdu5NextLine
         TST     ecfptr, #63                     ;  ecf pointer, wrapping if
         SUBEQ   ecfptr, ecfptr, #64             ;  necessary
 
-        ASSERT  HardFont < &40000000 :LOR: HardFont >= &C0000000
+        ASSERT  HardFont - ToRelative < &40000000 :LOR: HardFont - ToRelative >= &C0000000
         ASSERT  WsPtr < &40000000 :LOR: WsPtr >= &C0000000
         TEQ     charmsk, #0                     ; Double height? (MI=yes)
         LDRMIB  charbyte, [charptr, -charptr, ASR #1] ; Use ASR, as font will be at