unicorn-singlestep.py

#!/usr/bin/env python
# Sample code for MIPS of Unicorn. Nguyen Anh Quynh <aquynh@gmail.com>
# Python sample ported by Loi Anh Tuan <loianhtuan@gmail.com>

from traceback import format_exc

from unicorn import *
from unicorn.mips_const import *

#400790  24020123  addiu $v0, $zero, 0x123
#400794  03e00008  jr    $ra
#400798  00000000  nop
#40079c  0c1001e4  jal   0x400790   <--- start
#4007a0  00000000  nop
#4007a4  00000000  nop              <--- stop

MIPS_CODE_EB = "".join([
    "\x24\x02\x01\x23", # li $v0, 0x123
    "\x03\xe0\x00\x08", # jr $ra
    "\x00\x00\x00\x00", # nop
    "\x0c\x10\x01\xe4", # jal 0x400790
    "\x00\x00\x00\x00", # nop
    "\x00\x00\x00\x00", # nop
    ])

# memory address where emulation starts
ADDRESS = 0x0400790

current_start = 0x40079c
end_address = 0x4007a4

# callback for tracing instructions
def hook_code(uc, address, size, user_data):
    #print ""
    print "_" * 80
    print "    Tracing instruction at 0x%x, instruction size = 0x%x\n" %(address, size)

    zr = uc.reg_read(UC_MIPS_REG_ZERO)
    at = uc.reg_read(UC_MIPS_REG_AT) 
    v0 = uc.reg_read(UC_MIPS_REG_V0) 
    v1 = uc.reg_read(UC_MIPS_REG_V1) 
    a0 = uc.reg_read(UC_MIPS_REG_A0) 
    a1 = uc.reg_read(UC_MIPS_REG_A1) 
    a2 = uc.reg_read(UC_MIPS_REG_A2) 
    a3 = uc.reg_read(UC_MIPS_REG_A3) 
    t0 = uc.reg_read(UC_MIPS_REG_T0) 
    t1 = uc.reg_read(UC_MIPS_REG_T1) 
    t2 = uc.reg_read(UC_MIPS_REG_T2) 
    t3 = uc.reg_read(UC_MIPS_REG_T3) 
    t4 = uc.reg_read(UC_MIPS_REG_T4) 
    t5 = uc.reg_read(UC_MIPS_REG_T5) 
    t6 = uc.reg_read(UC_MIPS_REG_T6) 
    t7 = uc.reg_read(UC_MIPS_REG_T7) 
    s0 = uc.reg_read(UC_MIPS_REG_S0) 
    s1 = uc.reg_read(UC_MIPS_REG_S1) 
    s2 = uc.reg_read(UC_MIPS_REG_S2) 
    s3 = uc.reg_read(UC_MIPS_REG_S3) 
    s4 = uc.reg_read(UC_MIPS_REG_S4) 
    s5 = uc.reg_read(UC_MIPS_REG_S5) 
    s6 = uc.reg_read(UC_MIPS_REG_S6) 
    s7 = uc.reg_read(UC_MIPS_REG_S7) 
    gp = uc.reg_read(UC_MIPS_REG_GP) 
    sp = uc.reg_read(UC_MIPS_REG_SP) 
    pc = uc.reg_read(UC_MIPS_REG_PC) 
    ra = uc.reg_read(UC_MIPS_REG_RA) 
    fp = uc.reg_read(UC_MIPS_REG_FP) 

    print "    $0 = 0x%08x at = 0x%08x v0 = 0x%08x v1 = 0x%08x" % (zr, at, v0, v1)
    print "    a0 = 0x%08x a1 = 0x%08x a2 = 0x%08x a3 = 0x%08x" % (a0, a1, a2, a3)
    print "    t0 = 0x%08x t1 = 0x%08x t2 = 0x%08x t3 = 0x%08x" % (t0, t1, t2, t3)
    print "    t4 = 0x%08x t5 = 0x%08x t6 = 0x%08x t7 = 0x%08x" % (t4, t5, t6, t7)
    print "    s0 = 0x%08x s1 = 0x%08x s2 = 0x%08x s3 = 0x%08x" % (s0, s1, s2, s3)
    print "    s4 = 0x%08x s5 = 0x%08x s6 = 0x%08x s7 = 0x%08x" % (s4, s5, s6, s7)
    print "    gp = 0x%08x sp = 0x%08x pc = 0x%08x ra = 0x%08x" % (gp, sp, pc, ra) 
    print "    fp = 0x%08x" % (fp)

    global current_start

    current_start = uc.reg_read(UC_MIPS_REG_PC)

    if current_start == end_address:
        current_start = None
        uc.emu_stop()

PAGE_SIZE = 0x1000

def _align_address(address):
    return address & 0xFFFFF000 #// PAGE_SIZE * PAGE_SIZE 

# Test MIPS EB
def test_mips_eb():
    try:
        global current_start
        global uc

        #print "Emulate MIPS code (big-endian)"
        # Initialize emulator in MIPS32 + EB mode
        uc = Uc(UC_ARCH_MIPS, UC_MODE_MIPS32 + UC_MODE_BIG_ENDIAN)

        address_aligned = _align_address(ADDRESS)

        # map 2MB memory for this euclation
        uc.mem_map(address_aligned, 2 * 1024 * 1024)

        # write machine code to be euclated to memory
        uc.mem_write(ADDRESS, MIPS_CODE_EB)

        # tracing all instructions with customized callback
        uc.hook_add(UC_HOOK_CODE, hook_code)

        while current_start != None:
            uc.emu_start(current_start, end_address+4, timeout=0, count=1)

            # update current_start because single-step does not update
            # the PC
            if current_start is not None:
                if current_start == 0x40079c:
                    current_start = 0x400790
                elif current_start == 0x400794:
                    current_start = 0x4007a4
                else:
                    current_start += 4

        # now print out some registers
        print ">>> Emulation done. Below is the CPU context"

        v0 = uc.reg_read(UC_MIPS_REG_V0)
        print ">>> v0 = 0x%x" % v0

    except UcError as e:
        print format_exc()
        print "ERROR: %s" % e

if __name__ == '__main__':
    test_mips_eb()
    print "=" * 27