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SubjectRe: Strange Linking Problem
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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