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simple_x64 does not add extra unwanted REX for some 'Slash [MEM]' instruction

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This commit is contained in:
Clement Rouault
2017-05-24 17:33:40 +02:00
parent e5e9ff7a47
commit 5b17cc988f
1 changed files with 21 additions and 3 deletions
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windows/native_exec/simple_x64.py
+21 -3
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@@ -1,6 +1,6 @@
import collections
import struct
from windows.dbgprint import dbgprint
DEBUG = False
@@ -573,7 +573,6 @@ class ModRM_REG__REG(SubModRM):
self.mod = BitArray(2, "11")
self.is_rex_needed = True
#self.rex[4] = 1 # Setup by setup_reg_as_register or setup_rm_as_register
self.setup_reg_as_register(arg2)
self.setup_rm_as_register(arg1)
self.direction = 0
@@ -673,6 +672,23 @@ class ModRM_REG64__MEM(SubModRM):
return BitArray.from_int(2, scale[mem_access.scale]) + self.setup_sib_index_rex(mem_access.index) + self.setup_sib_base_rex(mem_access.base)
class REG64__MEM_Slash(ModRM_REG64__MEM):
# A ModRM_REG64__MEM where the setup_reg_as_register() does
# not set the REX (as the register is hardcoded in the Slash
def setup_reg_as_register(self, name):
if name in registers_32_bits:
name = registers_32_bits[name]
self.setup_as_32bit_operation()
else:
# self.is_rex_needed = True
# self.rex[4] = 1
self.setup_as_64bit_operation()
self.reg = X64RegisterSelector.get_reg_bits(name)
if X64.is_new_reg(name):
self.is_rex_needed = True
self.rex[5] = 1
class Slash(object):
"No idea for the name: represent the modRM for single args + encoding in reg (/7 in cmp in man intel)"
@@ -690,7 +706,7 @@ class Slash(object):
if X64.is_32b_reg(args[0]):
injected_reg = registers_64_to_32_bits[injected_reg]
try:
arg_consum, value, rex = ModRM([ModRM_REG__REG, ModRM_REG64__MEM], has_direction_bit=False).accept_arg(args[:1] + [injected_reg] + args[1:], instr_state)
arg_consum, value, rex = ModRM([ModRM_REG__REG, REG64__MEM_Slash], has_direction_bit=False).accept_arg(args[:1] + [injected_reg] + args[1:], instr_state)
except ValueError as e:
# Size mismatch
return None, None, None
@@ -706,6 +722,7 @@ class Instruction(object):
default_rex = BitArray.from_int(8, 0x40)
def __init__(self, *initial_args):
dbgprint("Assembling {0}{1}".format(type(self).__name__, initial_args), "X64")
for type_encoding in self.encoding:
args = list(initial_args)
res = []
@@ -724,6 +741,7 @@ class Instruction(object):
else: # if no break
if args: # if still args: fail
continue
dbgprint("Valid encoding found: REX={0:#x}".format(ord(full_rex.dump())), "X64")
self.prefix = prefix
self.value = sum(res, BitArray(0, ""))
if str(full_rex.dump()) != "\x40":