linux syscall uname for x86

Question

I only study assembler (nasm) and have more question. For example i want make asm code that get info about operating system. I use linux 86 bit. In a code i use syscall uname. In a browser have more information about this syscall and code. I found this link:

https://github.com/hc0d3r/asm/blob/master/uname.asm

Uname syscall in buffer overflow

But i use 86 bit system. So, i tried rewrite code for my system. I understand, that in register eax i should move value of syscall (0x7a or 122) and in register ebx addres of array.

I used first link as example, but get error. So, can you help me decide this problem?

This is my main code:

extern printf

SYS_WRITE equ 4
SYS_UNAME equ 122
SYS_EXIT equ 60
STDOUT equ 1

section .data
str: db '%s',10,0
UTSNAME_SIZE equ 65
space db ' '
break_line db 0xa

section .bss
uname_res resb UTSNAME_SIZE*5

section .text
global main
main:
    mov eax, 0x7A
    mov ebx, uname_res
    int 80h


push dword [uname_res]
    push dword str
    call printf

mov eax, 1
int 80h

and I got this error:

segmentation error (memory dump made)

This mistake on printf. Sorry for my crooked english

I'm not used to pushing arguments to the stack, but have you tried push str instead of push dword [str]? Also, by 86 bit do you mean x86? — mediocrevegetable1
@mediocrevegetable1 I change push. Now "push dword str". In the internet used "push dword str". I use linux x86 — OKIS
@mediocrevegetable1 The error remains. Does not display information — OKIS
x86 doesn't mean 86-bit. There are only 16, 32 and 64-bit x86 — phuclv
Didn't recall what syscall 0x7a does, but push dword [uname_res] is probably wrong, you probably want push uname_res. Also, familiarize yourself with gdb, radare2, or any debugger, they will help you shed some light on the crashes. — Margaret Bloom

OKIS OKIS · Accepted Answer · 2021-02-24T05:16:14

I wrote code for linux x86. Look it here (maybe will be useful)

https://github.com/OlegInfoSecurity/uname_x86

This error occurred when i output (print) info. I changed code for output info and program is work.

linux syscall uname for x86

1 Answers