python-JIT

base_asm.s

.intel_syntax noprefix
.globl main

main:
    push    r12
    push    r13
    push    rbx

    mov     r13, 0x123456789abcdef0
    mov     r12, 26
    mov     rbx, 0x41

loop:
    cmp     r12, 0
    jz      end

    mov     rdi, rbx
    call    r13

    inc     rbx
    dec     r12
    jmp     loop

end:
    mov     rdi, 0xa
    call    r13

    pop     rbx
    pop     r13
    pop     r12
    ret

objdump_result

a.out:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <main>:
   0:   41 54                   push   r12
   2:   41 55                   push   r13
   4:   53                      push   rbx
   5:   49 bd f0 de bc 9a 78    movabs r13,0x123456789abcdef0
   c:   56 34 12 
   f:   49 c7 c4 1a 00 00 00    mov    r12,0x1a
  16:   48 c7 c3 41 00 00 00    mov    rbx,0x41

000000000000001d <loop>:
  1d:   49 83 fc 00             cmp    r12,0x0
  21:   74 0e                   je     31 <end>
  23:   48 89 df                mov    rdi,rbx
  26:   41 ff d5                call   r13
  29:   48 ff c3                inc    rbx
  2c:   49 ff cc                dec    r12
  2f:   eb ec                   jmp    1d <loop>

0000000000000031 <end>:
  31:   48 c7 c7 0a 00 00 00    mov    rdi,0xa
  38:   41 ff d5                call   r13
  3b:   5b                      pop    rbx
  3c:   41 5d                   pop    r13
  3e:   41 5c                   pop    r12
  40:   c3                      ret 

python_jit_2.py

import sys, struct
from ctypes import *

libc = cdll.LoadLibrary("libc.so.6")
free = libc.free
printf = libc.printf
putchar = libc.putchar

mmap = libc.mmap
mmap.restype = c_void_p
munmap = libc.munmap
munmap.argtype = [c_void_p, c_size_t]

PROT_READ       = 1
PROT_WRITE      = 2
PROT_EXEC       = 4
MAP_PRIVATE     = 2
MAP_ANONYMOUS   = 0x20

def conv64(dw):
    return map(ord, struct.pack("<q" if dw < 0 else "<Q", dw))

codes = (c_ubyte * 128) (
    0x41, 0x54,                                 # push  r12
    0x41, 0x55,                                 # push  r13
    0x53,                                       # push  rbx
    0x49, 0xbd, 0x00, 0x00, 0x00, 0x00, 0x00,   # mov   r13, (long)
    0x00, 0x00, 0x00,
    0x49, 0xc7, 0xc4, 0x1a, 0x00, 0x00, 0x00,   # mov   r12, 0x1a
    0x48, 0xc7, 0xc3, 0x41, 0x00, 0x00, 0x00,   # mov   rbx, 0x41
    0x49, 0x83, 0xfc, 0x00,                     # cmp   r12, 0
    0x74, 0x0e,                                 # je    <end>
    0x48, 0x89, 0xdf,                           # mov   rdi, rbx
    0x41, 0xff, 0xd5,                           # call  r13
    0x48, 0xff, 0xc3,                           # inc   rbx
    0x49, 0xff, 0xcc,                           # dec   r12
    0xeb, 0xec,                                 # jmp   <loop>
    0x48, 0xc7, 0xc7, 0x0a, 0x00, 0x00, 0x00,   # mov   rdi, 0xa
    0x41, 0xff, 0xd5,                           # call  r13
    0x5b,                                       # pop   rbx
    0x41, 0x5d,                                 # pop   r13
    0x41, 0x5c,                                 # pop   r12
    0xc3,                                       # ret
)

buflen = len(codes)
p = mmap(
    0, buflen,
    PROT_READ | PROT_WRITE | PROT_EXEC,
    MAP_PRIVATE | MAP_ANONYMOUS,
    -1, 0
)

getaddr = CFUNCTYPE(c_void_p, c_void_p)(lambda p: p)
f       = CFUNCTYPE(c_void_p)(p)

codes[7:15] = conv64(getaddr(putchar))
memmove(p, addressof(codes), buflen)

f() 

munmap(p, buflen)

sample.s

.intel_syntax noprefix
.globl main

main:
    mov     r12, 26
    mov     rbx, 0x41

loop:
    cmp     r12, 0
    jz      end

    mov     rdi, rbx
    call    putchar

    inc     rbx
    dec     r12
    jmp     loop

end:
    mov     rdi, 0xa
    call    putchar