NASM - The Netwide Assembler
NASM Forum => Using NASM => Topic started by: indieexe on April 23, 2013, 08:57:01 PM
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I'm on Ubuntu, followed a NASM tutorial online.
I told nasm to create an object file of the following code using the command: nasm -f elf64 01.asm.
I then linked the c libraries and told gcc to create an executable with the following command: gcc 01.o -o prog.
This apparently in order to use the printf subroutine in C.
The linking was successful however when i ran this program with ./prog i got a segmentation fault.
What is wrong about the code, why do i get a segmentation fault?
(The following code is identical to what the tuturial author wrote).
[section .data]
hello: db 'Hello, Wordl!',10,0
[section .text]
global main
extern printf
main:
push hello
call printf
add esp,4
mov eax,0
ret
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Your code is fine... but it's for 32bit. Easy way to fix it is to assemble it with "-f elf32" instead of "-f elf64", and tell gcc "-m32" so it will produce 32-bit code. This should run fine on your 64-bit system. If you want 64-bit code, the first parameter to "printf" goes in rsi (or is it rdi?), not on the stack. I think you need to zero rax to say that you haven't got any floating-point parameters. There may be some stack manipulation required, as well. I'm still running 32-bit hardware, and 64-bit code seems "weird" to me. I suppose I'll get used to it once I start using it. (obviously, I'm not in too much of a rush). You may find some 64-bit examples in the "Examples" section that will help... 32-bit examples (like what you've got) are easier to find, and telling gcc "-m32" doesn't seem too hard...
Best,
Frank
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Hi indieexe,
I think your program won't work under Linux 64 bit. The ABI (Application Binary Interface) has changed. Please check out the following link. (http://www.intel-assembler.it/portale/5/system-v-application-binary-interface/amd-64bit-programming.asp) Your tutorial is for 32 bit.
Gerhard