Programming Forums > Application Development > Assembly

zyd · Oct 31st, 2005, 9:04 PM

Hello everyone. new guy in the neighbourhood.
i am starting to program in asm exclusively in linux, but i haven't found good information about the int 80h, just some vague notes.
Could anybody tell me of a paper or a site where i can find good information about this interruption.
Thanks in advance

DaWei · Oct 31st, 2005, 9:56 PM

Depends entirely upon the implementation and the last code that set it up.

zyd · Oct 31st, 2005, 10:06 PM

yes, i read that. But i heard that there are more than less estandarized formats. For example on linux x86, there ought to be a minimum standar, because if there were not, a program wouldn't be portable from one machine to another.
In /usr/include/asm/unistd.h there are the numbres of every single system call. I just need to know the parameters and the locations of them for every system call.

splyxx · Nov 1st, 2005, 7:29 AM

Hi,

http://www.lxhp.in-berlin.de/lhpsysc0.html

There's a lot of stuff at www.linuxassembly.org too. On a side note, I would not perform system calls directly if there's a chance to use libc. Doing so only requires linking with the library itself and the C runtime support module and specifying a runtime linker to use:

(Toggle Plain Text)

/home/splyxx [0]> cat test.asm
extern puts
global main

section .text

msg db 'hello world', 0

main:
        push dword msg
        call puts
        add esp, 4
        mov eax, 0
        ret

/home/splyxx [0]> nasm -f elf test.asm -o test.o
/home/splyxx [0]> ld test.o -o test /usr/lib/crti.o /usr/lib/crtn.o /usr/lib/crt1.o -lc --dynamic-linker /lib/ld-linux.so.2
/home/splyxx [0]> ./test
hello world
/home/splyxx [0]>

(The details may differ if you're using a new Linux system - this one is almost three years old - but you should be able to reverse-engineer what gcc does to link applications. If you link with libc, your assembly code will be portable to FreeBSD, NetBSD, OpenBSD (If you prepend libc functions with a ``_'' character even to a.out-based OpenBSD) and perhaps other x86 systems your assembler runs on.)

In fact you should invoke gcc instead of ld to link your application, unless you're writing your own compiler

zyd · Nov 1st, 2005, 11:17 AM

ok, that trick of linking the program against glibc, works just fine. But i am doing some research, and every single program in asm for linux x86 that i find uses the int 80h, and they are not so self-explanatory, so it would be nice to have some docs about it.

Oct 31st, 2005, 9:04 PM	#1
zyd Newbie Join Date: Oct 2005 Posts: 11 Rep Power: 0	int 80h Hello everyone. new guy in the neighbourhood. i am starting to program in asm exclusively in linux, but i haven't found good information about the int 80h, just some vague notes. Could anybody tell me of a paper or a site where i can find good information about this interruption. Thanks in advance

Oct 31st, 2005, 9:56 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Depends entirely upon the implementation and the last code that set it up. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 1st, 2005, 7:29 AM	#4
splyxx Newbie Join Date: Nov 2005 Posts: 4 Rep Power: 0	Hi, http://www.lxhp.in-berlin.de/lhpsysc0.html There's a lot of stuff at www.linuxassembly.org too. On a side note, I would not perform system calls directly if there's a chance to use libc. Doing so only requires linking with the library itself and the C runtime support module and specifying a runtime linker to use: (Toggle Plain Text) /home/splyxx [0]> cat test.asm extern puts global main section .text msg db 'hello world', 0 main: push dword msg call puts add esp, 4 mov eax, 0 ret /home/splyxx [0]> nasm -f elf test.asm -o test.o /home/splyxx [0]> ld test.o -o test /usr/lib/crti.o /usr/lib/crtn.o /usr/lib/crt1.o -lc --dynamic-linker /lib/ld-linux.so.2 /home/splyxx [0]> ./test hello world /home/splyxx [0]> /home/splyxx [0]> cat test.asm extern puts global main section .text msg db 'hello world', 0 main: push dword msg call puts add esp, 4 mov eax, 0 ret /home/splyxx [0]> nasm -f elf test.asm -o test.o /home/splyxx [0]> ld test.o -o test /usr/lib/crti.o /usr/lib/crtn.o /usr/lib/crt1.o -lc --dynamic-linker /lib/ld-linux.so.2 /home/splyxx [0]> ./test hello world /home/splyxx [0]> (The details may differ if you're using a new Linux system - this one is almost three years old - but you should be able to reverse-engineer what gcc does to link applications. If you link with libc, your assembly code will be portable to FreeBSD, NetBSD, OpenBSD (If you prepend libc functions with a ``_'' character even to a.out-based OpenBSD) and perhaps other x86 systems your assembler runs on.) In fact you should invoke gcc instead of ld to link your application, unless you're writing your own compiler

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Oct 31st, 2005, 10:06 PM	#3
zyd Newbie Join Date: Oct 2005 Posts: 11 Rep Power: 0	yes, i read that. But i heard that there are more than less estandarized formats. For example on linux x86, there ought to be a minimum standar, because if there were not, a program wouldn't be portable from one machine to another. In /usr/include/asm/unistd.h there are the numbres of every single system call. I just need to know the parameters and the locations of them for every system call.

Nov 1st, 2005, 11:17 AM	#5
zyd Newbie Join Date: Oct 2005 Posts: 11 Rep Power: 0	ok, that trick of linking the program against glibc, works just fine. But i am doing some research, and every single program in asm for linux x86 that i find uses the int 80h, and they are not so self-explanatory, so it would be nice to have some docs about it.

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