Example of execve

Example of execve

[Slack Traq]

Hello.
Can anyone give me an example of how can i implement
the execve syscall under asm, because I don't know how
to pass arrays as parameters.
Thank you in advance,

                                       Slack Ware


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Re: Example of execve

[Brian Raiter]

> Can anyone give me an example of how can i implement
> the execve syscall under asm, because I don't know how
> to pass arrays as parameters.

You don't pass arrays per se to execve(). execve() takes pointers to
arrays. Just construct the array somewhere in your data
segment. Simple example:

section .data

str1:	db	"foo", 0
str2:	db	"bar", 0
str3:	db	"baz", 0
array:	dd	str1, str2, str3, 0

section .text

	push	str1		; filename
	push	array		; argv
	push	dword 0		; envp
	call	execve

b

Re: Example of execve

[Gigi Sullivan]

Aiee :)

   Hello!

On Tue, Apr 29, 2003 at 12:31:12PM -0700, Slack Traq wrote:
> Can anyone give me an example of how can i implement
> the execve syscall under asm, because I don't know how
> to pass arrays as parameters.
> Thank you in advance,
> 
>                                        Slack Ware

   Here below you can find a simple example (nasm syntax)
   about executing an execve syscall. For the sake of simplicity
   there are no sanity checks, however.

      ; execve(2) syscall asm example
      ; nasm syntax 

      SECTION .text

      _start:

         mov ebx, array
         lea ecx, [array+8]
         lea edx, [array+12]
         mov eax, 0xb
         int 0x80

      SECTION .data

      array db '/bin/sh', 0
            dd array
            dd 0

   This way we're not calling any glibc function but we're issuing 
   the 0x80 interrupt software. The ELF obtained it's fully relocatable
   since we're running a syscall ...

   Hope this helps a bit and that is what you're looking for.

bye,
GG sullivan

-- 
Lorenzo Cavallaro `Gigi Sullivan' <sullivan@sikurezza.org>

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