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|
|*************************************************************************
|* *
|* DSTART.S Startup module for Pascal programs using dLibs *
|* *
|*************************************************************************
|*
|* entry points
|*
.globl __base | basepage pointer
.globl __start | startup entry point
.globl _etext | end of text segment
.globl _edata | end of data segment
.globl _end | end of BSS segment (end of program)
.globl __BREAK | location of stack/heap break
.globl __ARGC | number of arguments
.globl __ARGS | argument list pointer
.globl __envp | environment string pointer
.globl _errno | system error number
|
| external references
|
|.globl __stklen | Stack size value from C (unsigned long)
|
| useful constants
|
MINSTK = 16384 | Minimum 16K stack size
MARGIN = 512 | Minimum memory to return to OS
|
| GEMDOS functions
|
Cconws = 0x09 | Console write string
Pterm = 0x4C | Process terminate (with exit code)
Mshrink = 0x4A | Shrink program space
|
| basepage offsets
|
p_hitpa = 0x04 | top of TPA
p_tbase = 0x08 | base of text
p_tlen = 0x0C | length of text
p_dbase = 0x10 | base of data
p_dlen = 0x14 | length of data
p_bbase = 0x18 | base of BSS
p_blen = 0x1C | length of BSS
p_env = 0x2C | environment string
p_cmdlin = 0x80 | command line image
|
| STARTUP ROUTINE (must be first object in link)
|
.text
.globl start
.globl _start
__start:
start:
_start:
|
| save initial stack and basepage pointers
|
movel sp,a5 | a5 = initial stack pointer
movel sp@(4),a4 | a4 = basepage address
movel a4,__base
movel a4@(p_tbase),d3
addl a4@(p_tlen),d3
movel d3,_etext | end of text segment
movel a4@(p_dbase),d3
addl a4@(p_dlen),d3
movel d3,_edata | end of data segment
movel a4@(p_bbase),d3
addl a4@(p_blen),d3
movel d3,_end | end of BSS (end of program)
movel d3,__BREAK; | set initial _break value
movel a4@(p_env),__envp | save environment pointer
|
| call C function to get command line arguments
|
lea a4@(p_cmdlin),a0 | get pointer to command line image
moveb a0@+,d0
extw d0 | extract length
| movew d0,sp@- | cmdlen
| movel a0,sp@- | cmdline
| jsr __initar | call _initargs(cmdline, cmdlen)
| addql #6,sp
movew d0,__ARGC | save length
movel a0,__ARGS | save pointer to string
|
| calculate free space available to program
|
movel __BREAK,d3
movel d3,a3 | a3 = base of free space
negl d3
addl a4@(p_hitpa),d3
subl #MARGIN,d3 | d3 = free space
|
| calculate new stack size (store in d2)
|
| ASSUME 8K STACK FOR THE MOMENT.
movel __stklen,d2 | d2 = _STKSIZ
tstl d2 | if __STKSIZ is zero
beq minimum | use MINSTK
bra setstk | use __STKSIZ
minimum:
movel #MINSTK,d2 | use MINSTK
|
| check to see if there is enough room for requested stack
|
setstk:
cmpl d3,d2
blt shrink | if (available < requested)
movel #stkerr,sp@-
movew #Cconws,sp@-
trap #1 | report a stack error
addql #6,sp
movew #-39,sp@-
movew #Pterm,sp@-
trap #1 | and return error -39 (ENSMEM)
|
| set up new stack pointer and Mshrink
|
shrink:
addl a3,d2 | new stack = free base + stack size
movel d2,sp
subl a4,d2 | keep space = new stack - __base
movel d2,sp@-
movel a4,sp@-
clrw sp@-
movew #Mshrink,sp@-
trap #1 | Mshrink(0, _base, keep);
addl #12,sp
|
| call C entry point function _main()
|
jsr PASCALMAIN | if _main returns
movew #0,sp@- | Terminate program normally
trap #1
| movew d0,sp@(4) | insert return value and fall thru
|
| check for stack overflow (done after all OS traps)
|
chkstk:
cmpl __BREAK,sp
bgt nosweat | if (_break > sp)
movel #stkovf,sp@-
movew #Cconws,sp@-
trap #1 | report a stack overflow
addql #6,sp
movew #-1,sp@-
movew #Pterm,sp@-
trap #1 | and return error -1 (ERROR)
nosweat:
movel traprtn,sp@- | else, restore return address
rts | and do a normal return.
|
| this call to _main ensures that it the user's main() function will be
| linked, even if it is in a library.
|
jsr PASCALMAIN | NO PATH TO THIS STATEMENT
movew d0,sp@-
movew #0x4c,sp@-
trap #1
|
| initialized data space
|
.data
.even
stkerr: | not enough memory for stack
.ascii "Not enough memory"
.byte 0x0d,0x0a,0x00
stkovf: | impending stack overflow
.ascii "Stack overflow"
.byte 0x0d,0x0a,0x00
.even
_errno: | system error number
.word 0
__ARGC: | number of command line args
.word 0
__ARGS: | pointer to command line arg list
.long 0
|
| uninitialized data space
|
.even
__base: | pointer to basepage
.long 0
_etext: | pointer to end of text segment
.long 0
_edata: | pointer to end of data segment
.long 0
_end: | pointer to end of BSS (end of program)
.long 0
__BREAK: | pointer to stack/heap break
.long 0
__envp: | pointer to environment string
.long 0
traprtn: | storage for return PC in trap hooks
.long 0
|
