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bextr_cmt.py
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bextr_cmt.py
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from ida_bytes import *
from idaapi import *
from idc import *
import idaapi
import ida_bytes
import idc
import binascii
def is_amd64_idb():
if ida_idp.ph.id != ida_idp.PLFM_386:
return False
return ida_ida.cvar.inf.is_64bit()
def get_mask(val):
result = 0
while val != 0:
result |= 1 << val
val -= 1
result >>= 1
return result
def resolve(ea):
mask = get_operand_value(ea, 2) # grab mask reg number
old_ea = ea
insn_counter = 0
while insn_counter < 30: # unsafe value, lower can't catch all... :/
insn_counter += 1
ea = prev_head(ea, 0)
if print_insn_mnem(ea) == "mov" and get_operand_type(ea, 1) == 5 and get_operand_value(ea, 0) == mask: # mov x,imm
if insn_counter > 15:
print("WARNING! Mov instruction is more than 15 opcodes before bextr!")
print("Result can be inaccurate.")
value = get_operand_value(ea, 1)
bits = ((value >> 8) & 0xFF)
if bits == 0:
print("EE RR RR OO RR")
return
start = value & 0xFF
bitmask = get_mask(bits)
is_s = ""
mask_mode = 1
if mask_mode == 0:
if bits > 1:
is_s = "s"
string = "extract {:d} bit" + is_s + ", starting from bit {:d}"
set_cmt(old_ea, string.format(bits, start), 0)
else:
source = print_operand(old_ea, 1)
dest = print_operand(old_ea, 0)
#string = dest + " = " + source + " >> {:d} & 0x{:X}"
string = source + " >> {:d} & 0x{:X}"
set_cmt(old_ea, string.format(start, bitmask), 0)
break
ea = old_ea + 5
return ea
def single_bextr():
ea = get_screen_ea()
opcode = print_insn_mnem(ea)
if opcode != "bextr":
print("Selected opcode is not bextr!")
return
resolve(ea)
def multi_bextr():
ea = get_first_seg()
end = get_segm_end(ea) - 0x10
while ea < BADADDR:
print(hex(ea))
if ea >= end:
if get_next_seg(ea) != get_segm_end(ea): # if next seg is not right after that one
ea = get_next_seg(ea)
end = get_segm_end(ea) - 0x10
if idaapi.getseg(ea).perm & idaapi.SEGPERM_EXEC == 0:
ea = get_next_seg(ea)
end = get_segm_end(ea) - 0x10
if print_insn_mnem(ea) != "bextr":
ea += 1
continue
ea = resolve(ea)
def start_plg():
#multi_bextr()
single_bextr()
class bextr_helper_t(idaapi.plugin_t):
flags = idaapi.PLUGIN_UNL
comment = "Simplify bextr instruction."
help = ""
wanted_name = "Comment bextr"
wanted_hotkey = "F10"
def init(self):
if not is_amd64_idb():
return ida_idaapi.PLUGIN_SKIP
return idaapi.PLUGIN_KEEP
def run(self, arg):
start_plg()
def term(self):
pass
def PLUGIN_ENTRY():
return bextr_helper_t()