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msp430: do not read destination operand for MOV #68

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May 22, 2024
Merged

msp430: do not read destination operand for MOV #68

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35 changes: 22 additions & 13 deletions angr_platforms/msp430/instrs_msp430.py
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Original file line number Diff line number Diff line change
Expand Up @@ -292,14 +292,16 @@ def decorate_dst(self, dst_bits, mode_bits, imm_bits):
# val = val.cast_to(ty)
return dst_str

def fetch_dst(self, dst_bits, mode_bits, imm_bits, ty):
def fetch_dst(self, dst_bits, mode_bits, imm_bits, ty, do_fetch=True):
"""
Fetch the destination argument.
:param dst_bits:
:param mode_bits:
:param imm_bits:
:param ty:
:return: The VexValue representing the destination, and the writeout function for it
:param do_fetch:
:return: The VexValue representing the destination (if do_fetch is set;
else None), and the writeout function for it
"""
dst_num = int(dst_bits, 2)
dst_name = ArchMSP430.register_index[dst_num]
Expand All @@ -312,7 +314,7 @@ def fetch_dst(self, dst_bits, mode_bits, imm_bits, ty):
dst_imm = int(imm_bits, 2)

# two-op instructions always have a dst and a writeout
val, writeout = self.fetch_reg(dst_num, dst_mode, dst_imm, ty)
val, writeout = self.fetch_reg(dst_num, dst_mode, dst_imm, ty, do_fetch)
# val = val.cast_to(ty)
return val, writeout

Expand Down Expand Up @@ -340,7 +342,7 @@ def decorate_reg(self, reg_name, reg_mode, imm):
raise Exception('Unknown mode found')
return reg_str

def fetch_reg(self, reg_num, reg_mode, imm, ty):
def fetch_reg(self, reg_num, reg_mode, imm, ty, do_fetch=True):
"""
Resolve the operand for register-based modes.
:param reg_num: The Register Number
Expand All @@ -349,25 +351,28 @@ def fetch_reg(self, reg_num, reg_mode, imm, ty):
:param ty: The Type (byte or word)
:return: The VexValue of the operand, and the writeout function, if any.
"""
val = None
# Boring register mode. A write is just a Put.
if reg_mode == ArchMSP430.Mode.REGISTER_MODE:
# Fetch the register
reg_vv = self.get(reg_num, ty)
val = reg_vv
if do_fetch:
val = self.get(reg_num, ty)
writeout = lambda v: self.put(v.cast_to(REGISTER_TYPE), reg_num)
# Indexed mode, add the immediate to the register
# A write here is a store to reg + imm
elif reg_mode == ArchMSP430.Mode.INDEXED_MODE:
# Fetch the register
reg_vv = self.get(reg_num, REGISTER_TYPE)
addr_val = reg_vv + imm
val = self.load(addr_val, ty)
if do_fetch:
val = self.load(addr_val, ty)
writeout = lambda v: self.store(v, addr_val)
# Indirect mode; fetch address in register; store is a write there.
elif reg_mode == ArchMSP430.Mode.INDIRECT_REGISTER_MODE:
# Fetch the register
reg_vv = self.get(reg_num, REGISTER_TYPE)
val = self.load(reg_vv, ty)
if do_fetch:
val = self.load(reg_vv, ty)
writeout = lambda v: self.store(v, reg_vv)
# Indirect Autoincrement mode. Increment the register by the type size, then access it
elif reg_mode == ArchMSP430.Mode.INDIRECT_AUTOINCREMENT_MODE:
Expand All @@ -380,11 +385,13 @@ def fetch_reg(self, reg_num, reg_mode, imm, ty):
# Do the increment, now
self.put(reg_vv + incconst, reg_num)
# Now load it.
val = self.load(reg_vv, ty)
if do_fetch:
val = self.load(reg_vv, ty)
writeout = lambda v: self.store(v, reg_num)
elif reg_mode == ArchMSP430.Mode.ABSOLUTE_MODE:
imm_vv = self.constant(imm, REGISTER_TYPE)
val = self.load(imm_vv, ty)
if do_fetch:
val = self.load(imm_vv, ty)
writeout = lambda v: self.store(v, imm_vv)
else:
raise Exception('Unknown mode found')
Expand Down Expand Up @@ -457,10 +464,10 @@ def compute_result(self, src, dst):
# pylint: disable=arguments-differ
pass

def fetch_operands(self):
def fetch_operands(self, do_fetch=True):
ty = Type.int_16 if self.data['b'] == '0' else Type.int_8
src, _ = self.fetch_src(self.data['s'], self.data['A'], self.data['S'], ty)
dst, self.commit_func = self.fetch_dst(self.data['d'], self.data['a'], self.data['D'], ty)
dst, self.commit_func = self.fetch_dst(self.data['d'], self.data['a'], self.data['D'], ty, do_fetch)
return src, dst

##
Expand Down Expand Up @@ -618,11 +625,13 @@ class Instruction_MOV(Type3Instruction):
opcode = '0100'
name = 'mov'

# NOTE: MOV is the only Type3Instruction that does *not* read its
# destination operand (i.e., do_fetch=False), as it will be overwritten
def fetch_operands(self):
if self.data['s'] == '0001' and self.data['d'] == '0000':
return None, None
else:
return Type3Instruction.fetch_operands(self)
return Type3Instruction.fetch_operands(self, do_fetch=False)

def disassemble(self):
# support useful pseudo-ops for disassembly
Expand Down