Re: Strange Linking Problem

[linux-os]

On Sat, 12 Mar 2005, Matthias-Christian Ott wrote:

> Hi!
> I hope I'm right here. I've the following assembler code:
>
> SECTION .DATA
>       hello:     db 'Hello world!',10
>       helloLen:  equ $-hello
>
> SECTION .TEXT
>       GLOBAL main
>
> main:
>
>
>
>       ; Write 'Hello world!' to the screen
>       mov eax,4            ; 'write' system call
>       mov ebx,1            ; file descriptor 1 = screen
>       mov ecx,hello        ; string to write
>       mov edx,helloLen     ; length of string to write
>       int 80h              ; call the kernel
>
>       ; Terminate program
>       mov eax,1            ; 'exit' system call
>       mov ebx,0            ; exit with error code 0
>       int 80h              ; call the kernel
>
>
> Then I run:
>
> nasm -f elf hello.asm
>
>
> I link it with ld and run it:
>
> ld -s -o hello hello.o
> ./hello
> segmentation fault
>
>
> I link it with the gcc and run it:
>
> gcc hello.o -o hello
> ./hello
> Hello world!
>
>
> What's wrong with the ld?

Nothing at all. Where is _start: ?

Remove the 'main' label and substitute _start:

It is 'C' convention that programs start with main(). They
really don't. With the Linux API, they start at _start: and
do some housekeeping before calling main. That's what the
crt.o file that the 'C' tool-chain uses, does.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
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