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Date: Tue, 4 Apr 2006 12:05:10 +0200
From: "Nicolas Cormier" <n.cormier@gmail.com>
To: freebsd-hackers@freebsd.org
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Subject: Function calling
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X-List-Received-Date: Tue, 04 Apr 2006 10:05:13 -0000

Hello.

I'm writing a function tracer on freebsd to know which function the
process passes inside.

ex:
----

nico > cat toto.c
int foo4()
{
}
int foo3()
{
}
int foo2()
{
  foo3();
}
int foo1()
{
  foo2();
}
int main()
{
  foo1();
  foo4();
}
nico >

will print:

         0x80484a8 (foo1)
                 0x804849c (foo2)
                         0x8048494 (foo3)
                         ret @ 0x8048498
                 ret @ 0x80484a5
         ret @ 0x80484b1
         0x804848c (foo4)
         ret @ 0x8048490
----

I use PTRACE to run the process in single-stepping mode.
For each step I look on the next instruction (read at %eip) and I seek
the following sequence:


call
[backup eip in addr and wait a step]
pushl=09%ebp
movl=09%esp, %ebp
[print addr and the sym associed]

OR

(plt call)
call
jmp =09*
pushl=09$
jmp =09.
[print eip and the sym associed]

OR

leave
ret
[print ret @ eip]


But when the program uses the libc I have more RET than call ...
What's the good way to find function calls and return ?

Thanks in advance for your help and sorry for my poor english.
--
Nico