Trace assembly instructions via gdb

traceit.py

import subprocess as sp
import select
import sys
import time

executable = "a.out"
function = "call_the_wrapper_fn"
arguments = ""

gdb = sp.Popen(["gdb", executable], stdin=sp.PIPE, stdout=sp.PIPE, stderr=sp.STDOUT)
gdb_poll = select.poll()
gdb_poll.register(gdb.stdout, select.POLLIN)

def gdb_read():
    timeout = 0
    out = ''
    while True:
        res = gdb_poll.poll(0)
        if res:
            out += gdb.stdout.read(1)
            timeout = 0
        elif timeout == 0:
            time.sleep(0.01)
            timeout = 1
        else:
            break
    return out

time.sleep(1)
gdb_read()
gdb.stdin.write('set disassembly-flavor intel\n')
gdb.stdin.write('break %s\n' % function)
gdb.stdin.write('run %s\n' % arguments)
time.sleep(1)
gdb_read()
gdb.stdin.write('display/i $pc\n')
out = gdb_read()
for line in out.split('\n'):
    if line.startswith('=>'):
        print line
depth = 0
while depth >= 0:
    gdb.stdin.write('stepi\n')
    out = gdb_read()
    for line in out.split('\n'):
        if '=>' in line:
            s = line.split()
            instr = s[3]
            if 'call' in instr:
                depth += 1
            if 'ret' in instr:
                depth -= 1
            print line
gdb.stdin.write('continue\n')
gdb_read()