Seg fault for memory read about pylibemu

[buffer]

Could you please provide a test code which reproduces the issue?

Thanks,
Angelo

[cperdana]

emu = pylibemu.Emulator()

emu.prepare('\x90\x90\xc3\x90\x90\x90', 0)
emu.test(2)
eip = emu.cpu_eip_get()
print "eip:", eip, hex(eip)
print emu.memory_read_byte(eip)
----------output-----------
eip: 4288514 0x417002L
Segmentation fault (core dumped)

platform:
ubuntu 12.04 64bit
Python 2.7.3 (default, Apr 20 2012, 22:39:59)
[GCC 4.6.3] on linux2
Cython version 0.15.1

[buffer]

I'm not able to reproduce it here...

buffer@alnitak ~ $ python
Python 2.7.3 (default, May 15 2012, 11:39:38)
[GCC 4.5.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.

import pylibemu
emu = pylibemu.Emulator()
emu.prepare('\x90\x90\xc3\x90\x90\x90', 0)
emu.test(2)
0
eip = emu.cpu_eip_get()
print "eip:", eip, hex(eip)
eip: 4288514 0x417002L
print emu.memory_read_byte(eip)
195

Cython is really not needed by your side because setup.py compiles the generated C file so the only difference between our environments is gcc (here 4.5.3).

Could you please try creating a .py file and run it in gdb? You should just do something like

$ gdb python

run test.py

After the segfault please something like backtrace' andinfo frame N' would be really useful to understand what's going on by your side.

[cperdana]

(gdb) run rkaji.py
Starting program: /usr/bin/python rkaji.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
eip: 4288513 0x417001L

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff55662e5 in emu_memory_read_byte (m=0xc2c780, addr=4288513, byte=0x0) at emu_memory.c:272
272 *byte = *((uint8_t *)address);

[cperdana]

I think the problem is uninitialize pointer in memory_read_byte in pylibemu.pyc.
You declare byte:
cdef uint8_t *byte # line 993
then without initialize it, you send it as parameter in
if emu_memory_read_byte(_mem, addr, byte) # line 999

I change the function as below and it works.
#--------------code-begin---------------------------
def memory_read_byte(self, uint32_t addr):
cdef c_emu_memory *_mem
cdef uint8_t byte # I change this line

    if self._emu is NULL:
        raise RuntimeError('Emulator not initialized')

    _mem = emu_memory_get(self._emu)
    if emu_memory_read_byte(_mem, addr, &byte):   #  I change this line
        raise RuntimeError("Error while reading a byte at address 0x%x" % (addr, ))

    return byte#  I change this line

#-------------code-end---------------------------

[buffer]

Committed a patch for your issue. I still had not the possibility to test memory_read_string method but the other memory_read methods should work for you too now. Please run tests/cpu_mem_test.py and tell if everything is ok.

[buffer]

Added a test for memory_read_string method too.

[cperdana]

Great, its working now. Thank you.