minix/lib/i86/rts/ncrtso.s

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ArmAsm
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2005-04-21 16:53:53 +02:00
! This is the C run-time start-off routine. It's job is to take the
! arguments as put on the stack by EXEC, and to parse them and set them up the
! way _main expects them.
! It also initializes _environ when this variable isn't defined by the
! programmer. The detection of whether _environ belong to us is rather
! simplistic. We simply check for some magic value, but there is no other
! way.
.extern _main, _exit, crtso, __penviron, __penvp
.extern begtext, begdata, begbss, endtext, enddata, endbss
.text
begtext:
crtso:
xor bp, bp ! clear for backtrace of core files
mov bx, sp
mov ax, (bx) ! argc
lea dx, 2(bx) ! argv
lea cx, 4(bx)
add cx, ax
add cx, ax ! envp
! Test if environ is in the initialized data area and is set to our
! magic number. If so then it is not redefined by the user.
mov bx, #_environ
cmp bx, #__edata ! within initialized data?
jae 0f
testb bl, #1 ! aligned?
jnz 0f
cmp (bx), #0x5353 ! is it our environ?
jne 0f
mov __penviron, bx ! _penviron = &environ;
0: mov bx, __penviron
mov (bx), cx ! *_penviron = envp;
push cx ! push envp
push dx ! push argv
push ax ! push argc
call _main ! main(argc, argv, envp)
push ax ! push exit status
call _exit
hlt ! force a trap if exit fails
.data
begdata:
.data2 0 ! for sep I&D: *NULL == 0
__penviron:
.data2 __penvp ! Pointer to environ, or hidden pointer
.bss
begbss:
.comm __penvp, 2 ! Hidden environment vector