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|
;*****************************************************************************/
;* */
;* modload.s */
;* */
;* o65 module loader for the cc65 library */
;* */
;* */
;* */
;* (C) 2002 Ullrich von Bassewitz */
;* Wacholderweg 14 */
;* D-70597 Stuttgart */
;* EMail: uz@musoftware.de */
;* */
;* */
;* This software is provided 'as-is', without any expressed or implied */
;* warranty. In no event will the authors be held liable for any damages */
;* arising from the use of this software. */
;* */
;* Permission is granted to anyone to use this software for any purpose, */
;* including commercial applications, and to alter it and redistribute it */
;* freely, subject to the following restrictions: */
;* */
;* 1. The origin of this software must not be misrepresented; you must not */
;* claim that you wrote the original software. If you use this software */
;* in a product, an acknowledgment in the product documentation would be */
;* appreciated but is not required. */
;* 2. Altered source versions must be plainly marked as such, and must not */
;* be misrepresented as being the original software. */
;* 3. This notice may not be removed or altered from any source */
;* distribution. */
;* */
;*****************************************************************************/
.include "o65.inc"
.include "modload.inc"
.include "zeropage.inc"
.import pushax, pusha0, push0, push1, decax1
.import _malloc, _free, _bzero
.import __ZP_START__ ; Linker generated
.macpack generic
;------------------------------------------------------------------------------
; Variables stored in the register bank in the zero page. Placing the variables
; here will protect them when calling other C functions.
Module = regbank+0 ; Pointer to module memory
Ctrl = regbank+2 ; Pointer to mod_ctrl structure
TPtr = regbank+4 ; Pointer to module data for relocation
;------------------------------------------------------------------------------
; Static module data
.bss
; Save areas and error recovery data
Stack: .byte 0 ; Old stackpointer
RegBankSave: .res regbanksize ; Save area for register bank
; The header of the o65 file. Since we don't need the first 8 bytes any
; longer, once we've checked them, we will overlay them with other data to
; save a few bytes.
Header: .tag O65_HDR ; The o65 header
; Input
InputByte = Header ; Byte read from input
; Relocation
RelocVal = Header + 1 ; Relocation value
.data
Read: jmp $FFFF ; Jump to read routine
.rodata
ExpectedHdr:
.byte O65_MARKER_0, O65_MARKER_1 ; non C64 marker
.byte O65_MAGIC_0, O65_MAGIC_1, O65_MAGIC_2 ; Magic ("o65")
.byte O65_VERSION ; Version
.word O65_MODE_CC65 ; Mode word
ExpectedHdrSize = * - ExpectedHdr
;------------------------------------------------------------------------------
; PushCallerData: Push the callerdata member from control structure onto the
; C stack.
.code
PushCallerData:
ldy #MOD_CTRL::CALLERDATA+1
lda (Ctrl),y
tax
dey
lda (Ctrl),y
jmp pushax
;------------------------------------------------------------------------------
; RestoreRegBank: Restore the register bank contents from the save area. Will
; destroy A and X (the latter will be zero on return).
.code
RestoreRegBank:
ldx #6
@L1: lda RegBankSave-1,x
sta regbank-1,x
dex
bne @L1
rts
;------------------------------------------------------------------------------
; GetReloc: Return a relocation value based on the segment in A.
; The routine uses some knowledge about the values to make the code shorter.
.code
GetReloc:
cmp #O65_SEGID_TEXT
bcc FormatError
cmp #O65_SEGID_ZP
beq @L1
bcs FormatError
; Text, data and bss segment
lda Module
ldx Module+1 ; Return start address of buffer
rts
; Zero page relocation
@L1: lda #<__ZP_START__
ldx #>__ZP_START__
rts
;------------------------------------------------------------------------------
; ReadByte: Read one byte with error checking into InputByte and A.
; ReadAndCheckError: Call read with the current C stack and check for errors.
.bss
ReadSize: .res 2
.code
ReadByte:
; C->read (C->callerdata, &B, 1)
jsr PushCallerData
lda #<InputByte
ldx #>InputByte
jsr pushax
ldx #0
lda #1
; This is a second entry point used by the other calls to Read
ReadAndCheckError:
sta ReadSize
stx ReadSize+1
jsr Read
; Check the return code and bail out in case of problems
cmp ReadSize
bne @L1
cpx ReadSize+1
beq @L2 ; Jump if ok
@L1: lda #MLOAD_ERR_READ
bne CleanupAndExit
; Done
@L2: lda InputByte ; If called ReadByte, load the byte read
Done: rts
;------------------------------------------------------------------------------
; FormatError: Bail out with an o65 format error
.code
FormatError:
lda #MLOAD_ERR_FMT
; bne CleanupAndExit ; Branch always
;------------------------------------------------------------------------------
; CleanupAndExit: Free any allocated resources, restore the stack and return
; to the caller.
.code
CleanupAndExit:
; Restore the stack so we may return to the caller from here
ldx Stack
txs
; Save the error return code
pha
; Check if we have to free the allocated block
lda Module
ldx Module+1
bne @L1
tay ; Test high byte
beq @L2
@L1: jsr _free ; Free the allocated block
; Restore the register bank
@L2: jsr RestoreRegBank
; Restore the error code and return to the caller
ldx #$00 ; Load the high byte
pla
rts
;------------------------------------------------------------------------------
; RelocSeg: Relocate the segment pointed to by a/x
.code
RelocSeg:
jsr decax1 ; Start value is segment-1
sta TPtr
stx TPtr+1
Loop: jsr ReadByte ; Read byte from relocation table
beq Done ; Bail out if end of table reached
cmp #255 ; Special offset?
bne @L1
; Increment offset by 254 and continue
lda TPtr
add #254
sta TPtr
bcc Loop
inc TPtr+1
jmp Loop
; Increment offset by A
@L1: add TPtr
sta TPtr
bcc @L2
inc TPtr+1
; Read the relocation byte, extract the segment id, fetch the corresponding
; relocation value and place it into ptr1
@L2: jsr ReadByte
and #O65_SEGID_MASK
jsr GetReloc
sta RelocVal
stx RelocVal+1
; Get the relocation byte again, this time extract the relocation type.
lda InputByte
and #O65_RTYPE_MASK
; Check for and handle the different relocation types.
cmp #O65_RTYPE_WORD
beq RelocWord
cmp #O65_RTYPE_HIGH
beq RelocHigh
cmp #O65_RTYPE_LOW
bne FormatError
; Relocate the low byte
RelocLow:
ldy #0
clc
lda RelocVal
bcc AddCommon
; Relocate a high byte
RelocHigh:
jsr ReadByte ; Read low byte from relocation table
ldy #0
clc
adc RelocVal ; We just need the carry
AddHigh:
lda RelocVal+1
AddCommon:
adc (TPtr),y
sta (TPtr),y
jmp Loop ; Done, next entry
; Relocate a word
RelocWord:
ldy #0
clc
lda RelocVal
adc (TPtr),y
sta (TPtr),y
iny
bne AddHigh ; Branch always (add high byte)
;------------------------------------------------------------------------------
; mod_load: Load and relocate an o65 module
.code
_mod_load:
; Save the register bank and clear the Module pointer
pha
ldy #6
@L1: lda regbank-1,y
sta RegBankSave-1,y
dey
bne @L1
sty Module
sty Module+1
pla
; Save the passed parameter
sta Ctrl
stx Ctrl+1
; Save the stack pointer so we can bail out even from subroutines
tsx
stx Stack
; Get the read function pointer from the control structure and place it into
; our call vector
ldy #MOD_CTRL::READ
lda (Ctrl),y
sta Read+1
iny
lda (Ctrl),y
sta Read+2
; Read the o65 header: C->read (C->callerdata, &H, sizeof (H))
jsr PushCallerData
lda #<Header
ldx #>Header
jsr pushax
lda #.sizeof(O65_HDR)
ldx #0 ; Always less than 256
jsr ReadAndCheckError ; Bails out in case of errors
; We read the o65 header successfully. Validate it.
ldy #ExpectedHdrSize-1
ValidateHeader:
lda Header,y
cmp ExpectedHdr,y
bne HeaderError
dey
bpl ValidateHeader
; Header is ok as far as we can say now. Read all options, check for the
; OS option and ignore all others. The OS option contains a version number
; and the module id as additional data.
iny ; Y = $00
sty TPtr+1 ; Flag for OS option read
Opt: jsr ReadByte ; Read the length byte
beq OptDone ; Jump if done
sta TPtr ; Use TPtr as a counter
; An option has a length of at least 2 bytes
cmp #2
bcc HeaderError ; Must be 2 bytes total at least
; Check for the OS option
dec TPtr
jsr ReadByte ; Get the option type
cmp #O65_OPT_OS ; OS option?
bne SkipOpt ; No: Skip
lda TPtr ; Get remaining length+1
cmp #5 ; CC65 has 6 bytes total
bne OSError
jsr ReadByte ; Get the operating system
cmp #O65_OS_CC65
bne OSError ; Wrong operating system
jsr ReadByte ; Get the version number, expect zero
bne OSError ; Wrong version
jsr ReadByte ; Get low byte of id
ldy #MOD_CTRL::MODULE_ID
sta (Ctrl),y
jsr ReadByte
ldy #MOD_CTRL::MODULE_ID+1
sta (Ctrl),y
inc TPtr+1 ; Remember that we got the OS
jmp Opt
; Skip one option
SkipOpt:
dec TPtr
beq Opt ; Next option
jsr ReadByte ; Skip one byte
jmp SkipOpt
; Operating system error
OSError:
lda #MLOAD_ERR_OS
jmp CleanupAndExit
; Options done, check that we got the OS option
OptDone:
lda TPtr+1
bne CalcSizes
; Entry point for header errors
HeaderError:
lda #MLOAD_ERR_HDR
jmp CleanupAndExit
; Skipped all options. Calculate the size of text+data and of text+data+bss
; (the latter is the size of the memory block we need). We will store the
; total module size also into the control structure for evaluation by the
; caller
CalcSizes:
lda Header + O65_HDR::TLEN
add Header + O65_HDR::DLEN
sta TPtr
lda Header + O65_HDR::TLEN + 1
adc Header + O65_HDR::DLEN + 1
sta TPtr+1
lda TPtr
add Header + O65_HDR::BLEN
pha ; Save low byte of total size
ldy #MOD_CTRL::MODULE_SIZE
sta (Ctrl),y
lda TPtr+1
adc Header + O65_HDR::BLEN + 1
iny
sta (Ctrl),y
tax
pla ; Restore low byte of total size
; Total memory size is now in a/x. Allocate memory and remember the result,
; both, locally and in the control structure so it the caller can access
; the memory block. After that, check if we got the requested memory.
jsr _malloc
sta Module
stx Module+1
ldy #MOD_CTRL::MODULE
sta (Ctrl),y
txa
iny
sta (Ctrl),y
ora Module
bne GotMem
; Could not allocate memory
lda #MLOAD_ERR_MEM
jmp CleanupAndExit
; Control structure is complete now. Clear the bss segment.
; bzero (bss_addr, bss_size)
GotMem: lda Module
add TPtr
pha
lda Module+1
adc TPtr+1 ; Module + tlen + dlen
tax
pla
jsr pushax
lda Header + O65_HDR::BLEN
ldx Header + O65_HDR::BLEN+1
jsr _bzero ; bzero (bss, bss_size);
; Load code and data segment into memory. The sum of the sizes of
; code+data segment is still in TPtr.
; C->read (C->callerdata, C->module, H.tlen + H.dlen)
jsr PushCallerData
lda Module
ldx Module+1
jsr pushax
lda TPtr
ldx TPtr+1
jsr ReadAndCheckError ; Bails out in case of errors
; We've got the code and data segments in memory. Next section contains
; undefined references which we don't support. So check if the count of
; undefined references is actually zero.
jsr ReadByte
bne Undef
jsr ReadByte
beq Reloc
Undef: jmp FormatError
; Number of undefined references was zero. Next come the relocation tables
; for code and data segment. Relocate the code segment
Reloc: lda Module
ldx Module + 1 ; Code segment address
jsr RelocSeg
; Relocate the data segment
lda Module
add Header + O65_HDR::TLEN
pha
lda Module + 1
adc Header + O65_HDR::TLEN + 1
tax
pla ; Data segment address in a/x
jsr RelocSeg
; We're done. Restore the register bank and return a success code
jsr RestoreRegBank ; X will be zero on return
lda #MLOAD_OK
rts
|
