Hello everyone Thanks for fellows' previous helps. I actually have a further question. I read an article that it says if I compile the following program
#include <stdio.h> int main(){ char *name[2]; name[0] = "/bin/sh"; name[1] = NULL; execve(name[0],name,NULL); return 0; } by gcc -o shellcode -ggdb -static shellcode.c when i "disassemble execve" inside gdb, I should be able to see the assembly code for execve, but I can't see those codes for execve(). Does anyone know how I can get the assembly code and see how the execve() works?? btw, I am using gcc3.2.2 any help is really appreciated best regards Chungwei On Sat, 6 Mar 2004 10:02:09 +1030 Greg 'groggy' Lehey <[EMAIL PROTECTED]> wrote: > On Friday, 5 March 2004 at 13:43:04 -0500, Chungwei Hsiung wrote: > > Hello.. > > I am super new to this list, and I have a simple question that I don't > > know why it does that. I have a simple test program. I compile it, and > > gdb to disassemble main. I got the following.. > > > > 0x80481f8 <main>: push %ebp > > 0x80481f9 <main+1>: mov %esp,%ebp > > 0x80481fb <main+3>: sub $0x8,%esp > > 0x80481fe <main+6>: and $0xfffffff0,%esp > > 0x8048201 <main+9>: mov $0x0,%eax > > 0x8048206 <main+14>: sub %eax,%esp > > 0x8048208 <main+16>: movl $0x804a6ce,0xfffffff8(%ebp) > > 0x804820f <main+23>: movl $0x0,0xfffffffc(%ebp) > > 0x8048216 <main+30>: sub $0x4,%esp > > 0x8048219 <main+33>: push $0x0 > > 0x804821b <main+35>: lea 0xfffffff8(%ebp),%eax > > 0x804821e <main+38>: push %eax > > 0x804821f <main+39>: pushl 0xfffffff8(%ebp) > > 0x8048222 <main+42>: call 0x804823c <execve> > > 0x8048227 <main+47>: add $0x10,%esp > > 0x804822a <main+50>: mov $0x0,%eax > > 0x804822f <main+55>: leave > > 0x8048230 <main+56>: ret > > > > I don't know if at line 5, we move zero to %eax. why do we need to sub > > %eax, %esp? why do we need to substract 0 from the stack pointer?? > > Any help is really appreciated. > > This is probably because you didn't optimize the output. You'd be > surprised how many redundant instructions the compiler puts in under > these circumstances. Try optimizing and see what the code looks like. > > If this *was* done with optimization, let's see the source code. > > Greg > -- > Note: I discard all HTML mail unseen. > Finger [EMAIL PROTECTED] for PGP public key. > See complete headers for address and phone numbers. > _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"