#!/usr/bin/env python
import subprocess, os, tempfile
from ctypes import *
PAGE_SIZE = 4096
class AssemblerFunction(object):
def __init__(self, code, ret_type, *arg_types):
# Run Nasm
fd, source = tempfile.mkstemp(".S", "assembly", os.getcwd())
os.write(fd, code)
os.close(fd)
target = os.path.splitext(source)[0]
subprocess.check_call(["nasm",source])
os.unlink(source)
binary = file(target,"rb").read()
os.unlink(target)
bin_len = len(binary)
# align our code on page boundary.
self.code_buffer = create_string_buffer(PAGE_SIZE*2+bin_len)
addr = (addressof(self.code_buffer) + PAGE_SIZE) & (~(PAGE_SIZE-1))
memmove(addr, binary, bin_len)
# Change memory protection
self.mprotect = cdll.LoadLibrary("libc.so.6").mprotect
mp_ret = self.mprotect(addr, bin_len, 4) # execute only.
if mp_ret: raise OSError("Unable to change memory protection")
self.func = CFUNCTYPE(ret_type, *arg_types)(addr)
self.addr = addr
self.bin_len = bin_len
def __call__(self, *args):
return self.func(*args)
def __del__(self):
# Revert memory protection
if hasattr(self,"mprotect"):
self.mprotect(self.addr, self.bin_len, 3)
if __name__ == "__main__":
add_func = """ BITS 64
mov rax, rdi ; Move the first parameter
add rax, rsi ; add the second parameter
ret ; rax will be returned
"""
Add = AssemblerFunction(add_func, c_int, c_int, c_int)
print Add(1, 2)
Diff to Previous Revision
--- revision 3 2015-03-24 18:22:37
+++ revision 4 2015-03-24 18:23:19
@@ -8,7 +8,6 @@
class AssemblerFunction(object):
def __init__(self, code, ret_type, *arg_types):
-
# Run Nasm
fd, source = tempfile.mkstemp(".S", "assembly", os.getcwd())
os.write(fd, code)
