Hello James!
07 May 97 21:06, James Vahn wrote to Sylvain Lauzon about assembly & linux:
 JV> But something is wrong here. This produces a clean executable when 
inked
 JV> with gcc (the compiler), but when linked with ld (the linker) directly
 JV> (ld -o int80 int80.o), the program segfaults and dumps core. Now if I
 JV> could just figure out the debugger....
you'll need to terminate the process in a clean way. This means use a signal 
or (preferred) the exit() systemcall. When you link with gcc, it'll add the 
startup code found in crt?.o which contains an exit call, but when using ld 
directly it just sees your object file. Remember, if you don't use _start or 
some other default, you'll have to pass an entry point to the linker, too. In 
the next messages are the disassembly listings to illustrate he differences. 
In the gcc version the label is changed to , of course.
I added a working version, but my nasm 0.90 is probably a bit different from 
yours, since i couldn't get it to assemble as-is. no guarantees though, i 
don't speak nasm.
 JV> ;nasm -f elf int80.asm -o int80.o
 JV> ;gcc int80.o -o int80
 JV> ;
 JV> section .text
 JV> global _start
 JV> _start:
 JV>         mov edx, 07h            ; write 0x07 characters
 JV>         mov ecx, msg            ; address of msg
 JV>         mov ebx, 0h             ; write to stdout
 JV>         mov eax, 4h             ; syscall write (see asm/unistd.h)
 JV>         int 80h                 ; trap
 JV>         ret
 JV> msg:
 JV>         db 'Hello!', 0Ah
------------------------------
[SECTION .text]
[BITS 32]
[GLOBAL _start]
_start:
        mov edx, 07h            ; write 0x07 characters
        mov ecx, msg            ; address of msg
        mov ebx, 0h             ; write to stdout
        mov eax, 4h             ; syscall write (see asm/unistd.h)
        int 80h                 ; trap
        mov ebx, 0h             ; zero exit value
        mov eax, 1h             ; syscall exit
        int 80h                 ; trap
        ret                     ;shouldn't get here
msg:
        db 'Hello!', 0Ah
----------------------
Bye , Pieter
--- GoldED 2.41+
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