jit.py

# modifies following code to work on macos
# https://eli.thegreenplace.net/2017/adventures-in-jit-compilation-part-4-in-python/
# interesting: https://developer.apple.com/documentation/apple-silicon/porting-just-in-time-compilers-to-apple-silicon?language=objc

import ctypes, mmap as mmap_flags

libc = ctypes.cdll.LoadLibrary(None)

mmap = libc.mmap
mmap.restype = ctypes.c_void_p
mmap.argtypes = (ctypes.c_void_p, ctypes.c_size_t, ctypes.c_int, ctypes.c_int, ctypes.c_int, ctypes.c_size_t)

mprotect = libc.mprotect
mprotect.restype = ctypes.c_int
mprotect.argtypes = (ctypes.c_void_p, ctypes.c_size_t, ctypes.c_int, ctypes.c_int)

CODE_SIZE = 1024

code_address = mmap(None, CODE_SIZE, mmap_flags.PROT_READ | mmap_flags.PROT_WRITE, mmap_flags.MAP_ANON | mmap_flags.MAP_PRIVATE, -1, 0)

if code_address == -1:
  raise OSError('mmap failed to allocate memory')

code = b'\x00\x7c\x00\x9b\xc0\x03\x5f\xd6'
assert len(code) <= CODE_SIZE
ctypes.memmove(code_address, code, len(code))

if mprotect(code_address, CODE_SIZE, mmap_flags.PROT_READ | mmap_flags.PROT_EXEC, 0) < 0:
  raise OSError('mprotect failed to make memory executable')

JittedFuncType = ctypes.CFUNCTYPE(ctypes.c_long, ctypes.c_long)
func = JittedFuncType(code_address)

print(func(100)) # 10000

z-cjit.py

import ctypes, mmap as mmap_flags, subprocess

libc = ctypes.cdll.LoadLibrary(None)

mmap = libc.mmap
mmap.restype = ctypes.c_void_p
mmap.argtypes = (ctypes.c_void_p, ctypes.c_size_t, ctypes.c_int, ctypes.c_int, ctypes.c_int, ctypes.c_size_t)

mprotect = libc.mprotect
mprotect.restype = ctypes.c_int
mprotect.argtypes = (ctypes.c_void_p, ctypes.c_size_t, ctypes.c_int, ctypes.c_int)

c_code = '''
int square(int x) {
  return x * x;
}
'''
command = ['clang', '-x', 'c', '-O2', '-fPIC', '-c', '-', '-o', '-']
process = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
machine_code, _ = process.communicate(input=c_code.encode())
code_size = len(machine_code)

code_address = mmap(None, code_size, mmap_flags.PROT_READ | mmap_flags.PROT_WRITE, mmap_flags.MAP_ANON | mmap_flags.MAP_PRIVATE, -1, 0)

if code_address == -1:
  raise OSError('mmap failed to allocate memory')
ctypes.memmove(code_address, machine_code, code_size)

if mprotect(code_address, code_size, mmap_flags.PROT_READ | mmap_flags.PROT_EXEC, 0) < 0:
  raise OSError('mprotect failed to make memory executable')

JittedFuncType = ctypes.CFUNCTYPE(ctypes.c_long, ctypes.c_long)
func = JittedFuncType(code_address)

print(func(100)) # XXX: ILLEGAL HARDWARE INSTRUCTION (not jumping to method inside machine code)