I read a book,it said:
In Linux Shell,the address for ESP every program
is equal,and it supportes the codes:
and then I add this codes in my two programs,andCode:unsigned long get_sp() { __asm__("movl %esp,%eax"); }
I insert it on the start about the function main() ,
but I find they get different value,how to explain?
(I first run in Shell:echo "0" >/proc/sys/kernel/randomize_va_space)
Your book is old.
Address space randomisation is new-ish - primarily designed to stop stupid script kiddies from trying buffer overflow / code injection.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
But seriously, you need to find another direction for your curiosity.
You're not learning C or C++, you're just out to grab hacking information - nothing more.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Hmm, that works for me, but you need root permissions to do it. Did you check to see that it was set?Originally Posted by leetow2003
root~/C
»cat /proc/sys/kernel/randomize_va_space
0
root~/C
»./a.out
4294958384
root~/C
»./a.out
4294958384
root~/C
»./a.out
4294958384
root~/C
»echo 2 > /proc/sys/kernel/randomize_va_space
root~/C
»cat /proc/sys/kernel/randomize_va_space
2
root~/C
»./a.out
4120804800
root~/C
»./a.out
705018288
root~/C
»./a.out
3830575680
W/ custom x64 kernel, v.3.0.6
I could see it being worth knowing once in a blue moon.
Last edited by MK27; 04-08-2012 at 06:38 AM.
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
