Machine code: Difference between revisions

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=={{header|Python}}==

The ctypes module is meant for calling existing native code from Python, but you can get it to execute your own bytes with some tricks. The bulk of the code is spent establishing an executable memory area - once that's done, the actual execution takes just a few lines.

<lang Python>import ctypes

import os

from ctypes import c_ubyte, c_int

code = bytes([0x8b, 0x44, 0x24, 0x04, 0x03, 0x44, 0x24, 0x08, 0xc3])

code_size = len(code)

# copy code into an executable buffer

if (os.name == 'posix'):

import mmap

executable_map = mmap.mmap(-1, code_size, mmap.MAP_PRIVATE | mmap.MAP_ANON, mmap.PROT_READ | mmap.PROT_WRITE | mmap.PROT_EXEC)

# we must keep a reference to executable_map until the call, to avoid freeing the mapped memory

executable_map.write(code)

# the mmap object won't tell us the actual address of the mapping, but we can fish it out by allocating

# some ctypes object over its buffer, then asking the address of that

func_address = ctypes.addressof(c_ubyte.from_buffer(executable_map))

elif (os.name == 'nt'):

# the mmap module doesn't support protection flags on Windows, so execute VirtualAlloc instead

code_buffer = ctypes.create_string_buffer(code)

PAGE_EXECUTE_READWRITE = 0x40 ~~# Windows constants that would usually come from header files~~

PAGE_EXECUTE_READWRITE = 0x40

MEM_COMMIT = 0x1000

executable_buffer_address = ctypes.windll.kernel32.VirtualAlloc(0, code_size, MEM_COMMIT, PAGE_EXECUTE_READWRITE)

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func_address = executable_buffer_address

else:

# for other platforms, we just hope DEP isn't enabled

code_buffer = ctypes.create_string_buffer(code)

func_address = ctypes.addressof(code_buffer)

⚫

prototype = ctypes.CFUNCTYPE(c_int, c_ubyte, c_ubyte)

func = prototype(func_address)

⚫

prototype = ctypes.CFUNCTYPE(c_int, c_ubyte, c_ubyte) ~~# build a function prototype from return type and argument types~~

⚫

res = func(7, 12)

func = prototype(func_address) # build an actual function from the prototype by specifying the address

⚫

print(res)</lang>

⚫

res = func(7,12)

⚫

print(res)

</lang>

=={{header|Racket}}==