Dear friend,
First of all, thank you for reading my letter.
I am a student.When I do researches about the buffer overflow, I meet a question and want to get your help.Please permit me to illustrate it with the following example:
First, provided we have such a simple program named as test001.c.
-------------------------------
int main()
{
char buf[10];
int i;
i=0;
return 1;
}
-------------------------------
If we compile the program with the command: gcc -S test001.s test001.c, show the content of the test001.s, we can get the following:
-------------------------------
.file 'test001.c'
.text
.globl main
.type main,@function
main:
pushl %ebp
movl %esp,%ebp
subl $40,%esp
andl $-16,%esp
movl $0,%eax
subl %eax,%esp
movl $0,-28(%ebp)
movl $1,%eax
leave
ret
.Lfel:
.size main,.Lfel-main
.ident 'GCC(GNU)3.2.2 20030222(Red Hat Linux(3.2.2-5)'
--------------------------------
From the above, we can know that the instruction 'subl $40,%esp' is used to allocate the space for the buf[] and i. My trouble is that I don't know in which function the 'subl $40,%esp' is introduced. Now I want to add some instructions before
the 'subl $40,%esp' to set some flags to indicate the end of the string. I hope you can tell me which sourcecode file I should look through among so many sourcecode files with the gcc tool.
Thanks again.
Look forward to your answer.
Sincerely,
Yejun Wang
wyj-me
wyj3390@xxxxxxxxxxxxxxxxx
2005-04-15
