Hi!
I wrote a library for packing files in my own format(tpack) for windows, so i'm translating it to linux-asm.
I started it with the basic writing functions.
This is my TPacker.inc:
; TPacker v2.0 library for GNU/Linux OS
proc tpackw.new stdcall file
stdcall sys_creat, [file], 00644o ; Attemp to create packet
test eax,eax ; Test for error
js .error ; Jump on error
clc ; Clear carry flag
stdcall sys_write, eax, __tpack_head, __tpack_head_size
test eax,eax ; Test for error
js .error ; Jump on error
jmp .ret ; Return
.error:
stc ; Set Carry Flag
jmp .ret ; Return
.ret:
ret
endp
proc tpackw.end stdcall fd
stdcall sys_write, [fd], __tpack_end_head, __tpack_end_head_size
test eax,eax ; Test for error
js .error ; Jump on error
clc
jmp .ret ; Return
.error:
stc ; Set Carry Flag
jmp .ret ; Return
.ret:
ret
endp
__tpack_head db "tpack2.0",0
__tpack_head_size = $-__tpack_head
__tpack_end_head db "epack",0
__tpack_end_head_size = $-__tpack_end_head
And the TPacker.asm for testing:
format ELF executable
entry main
include 'api.inc'
include 'TPacker.inc'
segment readable executable
main:
stdcall tpackw.new, _path
;jc .error
stdcall tpackw.end, eax
jc .error
jmp .ret
.error:
stdcall sys_write, 1 , _error, _error_size
jmp .ret
.ret:
stdcall sys_exit,1
segment readable writable
_path db "/home/thaorius/asm/pack.tpack",0
_error db "Error!",10,0
_error_size = $-_error
It build's fine, but on runtime, the function tpackw.end returns with error and the 'epack' head is not writed. But, if you look at tpack.new there is a call to sys_write with the fd that sys_creat returns.
The problem is that the head 'tpack2.0' is writed without problems but the 'epack' isn't.
Any ideas?
P/D: api.inc
; GNU/Linux API Wrapper
include 'macros.inc'
O_RDONLY equ 00
O_RWONLY equ 01
O_RDRW equ 02
proc sys_exit stdcall uses eax ebx,ecode
mov eax, 1 ; Select sys_exit function
mov ebx, [ecode] ; Exit code
int 80h ; Call the kernel
ret ; Return
endp
proc sys_fork stdcall
mov eax, 2 ; Select sys_fork function
int 80h ; Call the kernel
test eax, eax ; Check for error
js .error ; Jump on error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
; TEST THIS FUNCTION, IT READS BUT RETURNS ERROR ANYWAY
proc sys_read stdcall uses eax ebx ecx edx, fd, buffer, nbytes
mov eax, 3 ; Select sys_read function
mov ebx, [fd] ; File Descriptor
mov ecx, [buffer] ; Buffer address
mov edx, [nbytes] ; Bytes to read
int 80h ; Call the kernel
test eax,eax ; Check for error
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
proc sys_write stdcall uses ebx ecx edx, fd, buffer, buffer_len
mov eax, 4 ; Select sys_write function
mov ebx, [fd] ; File Descriptor
mov ecx, [buffer] ; Buffer
mov edx, [buffer_len] ; Buffer Len
int 80h ; Call the kernel
test eax,eax ; Check for error
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
proc sys_open stdcall uses ebx ecx, road, flags
mov eax, 5 ; Select sys_open function
mov ebx, [road] ; File location
mov ecx, [flags] ; Flags
int 80h ; Call the kernel
test eax,eax ; Check the file descriptor
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
proc sys_close stdcall uses ebx, fd
mov eax, 6 ; Select sys_close function
mov ebx, [fd] ; File descriptor
int 80h ; Call the kernel
test eax,eax ; Check for error
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
proc sys_creat stdcall uses ebx ecx, what, mode
mov eax, 8 ; Select sys_creat function
mov ebx, [what] ; File to create
mov ecx, [mode] ; Mode
int 80h ; Call the kernel
test eax,eax ; Check the file descriptor
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
proc sys_brk stdcall uses ebx, edsegment
mov eax, 45 ; Select sys_brk function
lea ebx, [edsegment] ; End data segment
int 80h ; Call the kernel
test eax,eax ; Check for error
js .error ; If the sign flag is set go to error
clc ; Clear carry flag
jmp .ret ; Jump to return instruction
.error:
stc ; Set carry flag
jmp .ret ; Jump to return instruction
.ret:
ret ; Return
endp
Thanks for helping me.
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> Linux > Error calling sys_write, help please
29 Aug 2006, 14:11
