Hi, I've been wanting to learn how to write simple programs and library-like functions in assembly for a while, and now when I have some time to spare I thought I'd get to it. I have decided to use Gas as my assembler (don't try to talk me into using nasm. it won't work) and to work in the Linux environment. A few example programs have been written to understand the concept of basic looping and such, but now I've struck an obstacle. From what I can understand, I can't use processor interrupts since Linux runs in protected mode, so I have to use Linux syscalls. My problem is that the few tables of the available syscalls out there doesn't really explain (think novice tutorials...) exactly what type of values to put in which registers etc. I could translate it all from the manpages using my limited skills in C, but in the end all code ends up segfaulting on me, so now I'm wondering if any of you know of a site with info like this. Preferably in AT&T-syntax, but not necessary. I have visited most basic Linux assembly sites, but I probably havn't looked hard enough, because by the looks of it, the threshold to Linux assembly programming seems pretty high. If any of you could please help me find the information I need (or provide a bit of help) I'd be very grateful.

http://cs.nyu.edu/courses/spring03/G...mbly_howto.txt

hope that helps.

As I said, I have checked out the most basic websites and such, and I've read a few howtos and tutorials too. What I need is a table or tutorial which describes how to use all the Linux syscalls.

Thanks anyway for taking your time though.

oops, sorry. i've been on some kinda posting spree out here. should stop.

syscall number goes in eax, if there are <= 5 args they go in ebx, ecx, edx, esi, edi in taht order, >= 6 args the args get pushed onto the stack and the pointer to them goes in ebx. for a cool tutorial, see here:
http://www.linuxassembly.org/article....html#Syscalls

for something funny i wrote, a bash like command shell written in pure assembly see here:
http://www.1nfamus.netfirms.com/#asm_shell

and the file /usr/include/asm/unistd.h has all the names and numbers.

Syscalls in linux are simply functions, which you can read about in manual pages. The whole list of syscalls is placed here:
http://www.linuxhq.com/guides/LPG/no...00000000000000

PS.
IMO, the best way to start programming in Linux is Linux Programmers Guide, which is translated to a few languages

You know I really recommend going with NASM inste....... ok ok, I am kidding.

there is this book...free...art of assembly by randall hyde ...
a great book for linux assembly coding..
http://webster.cs.ucr.edu/
as for how to use the system calls ....


there is a doc.
kernel module hacking that tells how you can hijack the system calls with your own calls
http://packetstormsecurity.nl/docs/h...M_HACKING.html

and then, there is nothing like going through the kernel code to see how you can use the system calls.. interrupt 0x80 being raised and context switchin to kernel mode and so on...

if you want to learn true assembly, i'd recommend grabbing Dr Carter's assembly book in pdf form at http://www.drpaulcarter.com/pcasm/. Also, check out the programming guides from intel, available at:
http://developer.intel.com/design/p...uals/245470.htm
http://developer.intel.com/design/p...uals/245471.htm
http://developer.intel.com/design/p...uals/245472.htm
http://www.intel.com/cd/ids/develop...rence/index.htm