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Streamlined the code, add zero page relocations
git-svn-id: svn://svn.cc65.org/cc65/trunk@1257 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cuz
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@ -38,6 +38,7 @@
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.import pushax, pusha0, push0, push1, decax1
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.import _malloc, _free, _memset
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.import __ZP_START__ ; Linker generated
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.importzp sp, ptr1, tmp1, regbank
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.macpack generic
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@ -59,18 +60,22 @@ TPtr = regbank+4 ; Pointer to module data for relocation
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Stack: .byte 0 ; Old stackpointer
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RegBankSave: .res 6 ; Save area for register bank
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; The header of the o65 file. Since we don't need the 8 bytes any longer,
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; once we've checked them, we will overlay them with other data to save a
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; few bytes.
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; The header of the o65 file. Since we don't need the first 8 bytes any
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; longer, once we've checked them, we will overlay them with other data to
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; save a few bytes.
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Header: .res O65_HDR_SIZE ; The o65 header
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; Input
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InputByte = Header ; Byte read from input
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; Stuff needed for relocation
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TextReloc = Header + 1 ; Relocation value for code seg
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DataReloc = Header + 3 ; Relocation value for data seg
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BssReloc = Header + 5 ; Relocation value for bss seg
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; Stuff needed for relocation. Since the ld65 linker uses a relocation base
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; address of zero for all segments, the relocation values needed are actually
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; the start addresses of the segments. Among other things this means that the
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; relocation value for the text segment is the same as the start address as
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; the whole module block.
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TextReloc = Module ; Relocation value for code seg
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DataReloc = Header + 1 ; Relocation value for data seg
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BssReloc = Header + 3 ; Relocation value for bss seg
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.data
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Read: jmp $FFFF ; Jump to read routine
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@ -106,15 +111,15 @@ LoadCtrl:
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;------------------------------------------------------------------------------
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; RestoreRegBank: Restore the register bank contents from the save area. Will
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; destroy A and X
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; destroy A and X (the latter will be zero on return).
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.code
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RestoreRegBank:
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ldx #6-1
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@L1: lda RegBankSave,x
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sta regbank,x
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ldx #6
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@L1: lda RegBankSave-1,x
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sta regbank-1,x
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dex
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bpl @L1
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bne @L1
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rts
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;------------------------------------------------------------------------------
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@ -140,7 +145,17 @@ GetReloc:
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ldx BssReloc+1
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rts
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@L3: lda #MLOAD_ERR_FMT
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@L3: cmp #O65_SEGID_ZP
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bne FormatError
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lda #<__ZP_START__
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ldx #>__ZP_START__
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rts
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;------------------------------------------------------------------------------
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; FormatError: Bail out with an o65 format error
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FormatError:
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lda #MLOAD_ERR_FMT
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; bne CleanupAndExit ; Branch always
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;------------------------------------------------------------------------------
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@ -181,6 +196,7 @@ CleanupAndExit:
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;------------------------------------------------------------------------------
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; ReadByte: Read one byte with error checking into InputByte and A.
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; ReadAndCheckError: Call read with the current C stack and check for errors.
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.code
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ReadByte:
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@ -192,6 +208,10 @@ ReadByte:
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ldx #>InputByte
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jsr pushax
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jsr push1
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; This is a second entry point used by the other calls to Read
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ReadAndCheckError:
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jsr Read
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; Check the return code and bail out in case of problems
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@ -203,7 +223,7 @@ ReadByte:
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; Done
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@L1: lda InputByte
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@L1: lda InputByte ; If called ReadByte, load the byte read
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Done: rts
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;------------------------------------------------------------------------------
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@ -254,43 +274,44 @@ Loop: jsr ReadByte ; Read byte from relocation table
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; Check for and handle the different relocation types.
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cmp #O65_RTYPE_WORD
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bne @L3
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beq RelocWord
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cmp #O65_RTYPE_HIGH
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beq RelocHigh
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cmp #O65_RTYPE_LOW
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bne FormatError
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; Relocate the low byte
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RelocLow:
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ldy #0
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clc
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lda (TPtr),y
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adc ptr1
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sta (TPtr),y
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jmp Loop
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; Relocate a high byte
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RelocHigh:
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jsr ReadByte ; Read low byte from relocation table
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ldy #0
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clc
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adc ptr1 ; We just need the carry
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AddHigh:lda (TPtr),y
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adc ptr1+1
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sta (TPtr),y
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jmp Loop ; Done, next entry
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; Relocate a word
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RelocWord:
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ldy #0
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clc
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lda (TPtr),y
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adc ptr1
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sta (TPtr),y
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iny
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bne @L4 ; Branch always (add high byte)
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@L3: cmp #O65_RTYPE_HIGH
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bne @L5
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jsr ReadByte ; Read low byte from relocation table
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ldy #0
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clc
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adc ptr1 ; We just need the carry
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@L4: lda (TPtr),y
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adc ptr1+1
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sta (TPtr),y
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jmp Loop ; Done, next entry
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@L5: cmp #O65_RTYPE_LOW
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beq @L6
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; Problem: Invalid relocation code
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lda #MLOAD_ERR_FMT
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jmp CleanupAndExit
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@L6: ldy #0
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clc
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lda (TPtr),y
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adc ptr1
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sta (TPtr),y
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; Finished with this relocation
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jmp Loop
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bne AddHigh ; Branch always (add high byte)
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;------------------------------------------------------------------------------
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; mod_load: Load and relocate an o65 module
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@ -336,18 +357,11 @@ _mod_load:
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jsr pushax
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lda #O65_HDR_SIZE
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jsr pusha0 ; Always less than 256
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jsr Read
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; Check the return code
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tax
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beq @L2
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lda #MLOAD_ERR_READ
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jmp CleanupAndExit
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jsr ReadAndCheckError ; Bails out in case of errors
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; We read the o65 header successfully. Validate it.
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@L2: ldy #ExpectedHdrSize-1
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ldy #ExpectedHdrSize-1
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@L3: lda Header,y
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cmp ExpectedHdr,y
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beq @L4
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@ -368,7 +382,10 @@ OneOpt: dec TPtr
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jmp OneOpt
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OptDone:
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; Skipped all options. Calculate the sizes of several areas needed later
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; Skipped all options. Calculate the size of text+data and of text+data+bss
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; (the latter is the size of the memory block we need). We will store the
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; total module size also into the control structure for evaluation by the
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; caller
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lda Header + O65_HDR_TLEN
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add Header + O65_HDR_DLEN
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@ -378,20 +395,17 @@ OptDone:
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sta TPtr+1
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lda TPtr
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add Header + O65_HDR_BLEN
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sta tmp1
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pha ; Save low byte of total size
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ldy #MODCTRL_MODULE_SIZE
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sta (Ctrl),y
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lda TPtr+1
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adc Header + O65_HDR_BLEN + 1
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; Load the total module size into a/x and store it into the control structure
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ldy #MODCTRL_MODULE_SIZE + 1
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iny
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sta (Ctrl),y
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tax
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dey
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lda tmp1
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sta (Ctrl),y
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pla ; Restore low byte of total size
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; Allocate memory, check if we got it
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; Total memory size is now in a/x. Allocate memory, check if we got it.
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jsr _malloc
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sta Module
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@ -408,10 +422,10 @@ OptDone:
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; structure. We will use internal knowlege about the layout of the structure
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; here to save some code.
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GotMem: lda Module
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GotMem: lda Module ; Ctrl->module = Module;
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ldy #MODCTRL_MODULE
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sta (Ctrl),y
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ldy #MODCTRL_CODE
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ldy #MODCTRL_CODE ; Ctrl->code = Module;
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sta (Ctrl),y
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txa
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iny
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@ -431,28 +445,34 @@ CLoop: lda Header,x
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cpy #MODCTRL_SIZE
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bne CLoop
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; Missing in the control structure now: start of the data and bss segments
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; Missing in the control structure now: start of the data and bss segments.
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; Since the linker relocates all segments to zero, these addresses are also
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; the relocation values for the segments.
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ldy #MODCTRL_DATA
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lda Module
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add Header + O65_HDR_TLEN
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sta (Ctrl),y
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sta DataReloc
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iny
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lda Module + 1
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adc Header + O65_HDR_TLEN + 1
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sta (Ctrl),y
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sta DataReloc + 1
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ldy #MODCTRL_BSS
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lda Module
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add TPtr
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sta (Ctrl),y
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sta BssReloc
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iny
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lda Module+1
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add TPtr+1
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sta (Ctrl),y
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sta BssReloc + 1
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; Control structure is complete now. Load code and data segment into memory.
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; The sum of the sizes of code and data segment is still in TPtr.
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; The sum of the sizes of code+data segment is still in TPtr.
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; C->read (C, C->module, H.tlen + H.dlen)
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jsr PushCtrl
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@ -462,80 +482,44 @@ CLoop: lda Header,x
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lda TPtr
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ldx TPtr+1
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jsr pushax
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jsr Read
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; Check for errors
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tax
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beq LoadOk
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lda #MLOAD_ERR_READ
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jmp CleanupAndExit
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jsr ReadAndCheckError ; Bails out in case of errors
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; We've got the code and data segments in memory. Next section contains
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; undefined references which we don't support. So check if the count of
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; undefined references is actually zero.
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LoadOk: jsr ReadByte
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jsr ReadByte
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bne Undef
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jsr ReadByte
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beq Reloc
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Undef: lda #MLOAD_ERR_FMT
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jmp CleanupAndExit
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Undef: jmp FormatError
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; Number of undefined references was zero. Next sections are the relocation
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; tables for code and data segment. Before doing the actual relocation, we
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; have to setup the relocation values for the three segments.
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; tables for code and data segment. Relocate the code segment
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Reloc: lda Module
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sub Header + O65_HDR_TBASE
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sta TextReloc
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lda Module + 1
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sbc Header + O65_HDR_TBASE + 1
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sta TextReloc + 1
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ldy #MODCTRL_DATA
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lda (Ctrl),y
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sub Header + O65_HDR_DBASE
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sta DataReloc
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iny
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lda (Ctrl),y
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sbc Header + O65_HDR_DBASE + 1
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sta DataReloc + 1
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ldy #MODCTRL_BSS
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lda (Ctrl),y
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sub Header + O65_HDR_BBASE
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sta BssReloc
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iny
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lda (Ctrl),y
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sbc Header + O65_HDR_BBASE + 1
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sta BssReloc + 1
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; Relocate the code segment
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lda Module
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ldx Module + 1 ; Code segment address
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ldx Module + 1 ; Code segment address
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jsr RelocSeg
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; Relocate the data segment
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ldy #MODCTRL_DATA + 1
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jsr LoadCtrl ; Get data segment address
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jsr LoadCtrl ; Get data segment address
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jsr RelocSeg
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; Clear the bss segment
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ldy #MODCTRL_BSS + 1
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jsr LoadCtrl ; Load bss segment address
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jsr LoadCtrl ; Load bss segment address
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jsr pushax
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jsr push0
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ldy #MODCTRL_BSS_SIZE + 1
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jsr LoadCtrl ; Load bss segment size
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jsr _memset ; memset (bss, 0, bss_size);
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lda Header + O65_HDR_BLEN
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ldx Header + O65_HDR_BLEN+1
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jsr _memset ; memset (bss, 0, bss_size);
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; We're done. Restore the register bank and return a success code
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jsr RestoreRegBank
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jsr RestoreRegBank ; X will be zero on return
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lda #MLOAD_OK
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rts
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