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from miasm2.core.bin_stream import bin_stream_str
from miasm2.core.asmblock import AsmConstraint
from miasm2.arch.x86.disasm import dis_x86_32, cb_x86_funcs
def cb_x86_callpop(cur_bloc, symbol_pool, *args, **kwargs):
"""
1000: call 1005
1005: pop
Will give:
1000: push 1005
1005: pop
"""
# Pattern matching
if len(cur_bloc.lines) < 1:
return
## We want to match a CALL, always the last line of a basic block
last_instr = cur_bloc.lines[-1]
if last_instr.name != 'CALL':
return
## The destination must be a location
dst = last_instr.args[0]
if not dst.is_loc():
return
loc_key = dst.loc_key
offset = symbol_pool.loc_key_to_offset(loc_key)
## The destination must be the next instruction
if offset != last_instr.offset + last_instr.l:
return
# Update instruction instance
last_instr.name = 'PUSH'
# Update next blocks to process in the disassembly engine
cur_bloc.bto.clear()
cur_bloc.add_cst(loc_key, AsmConstraint.c_next, symbol_pool)
# Prepare a tiny shellcode
shellcode = ''.join(["\xe8\x00\x00\x00\x00", # CALL $
"X", # POP EAX
"\xc3", # RET
])
bin_stream = bin_stream_str(shellcode)
mdis = dis_x86_32(bin_stream)
print "Without callback:\n"
asmcfg = mdis.dis_multiblock(0)
print "\n".join(str(block) for block in asmcfg.blocks)
# Enable callback
cb_x86_funcs.append(cb_x86_callpop)
## Other method:
## mdis.dis_block_callback = cb_x86_callpop
print "=" * 40
print "With callback:\n"
asmcfg_after = mdis.dis_multiblock(0)
print "\n".join(str(block) for block in asmcfg_after.blocks)
# Ensure the callback has been called
assert asmcfg.loc_key_to_block(asmcfg.heads()[0]).lines[0].name == "CALL"
assert asmcfg_after.loc_key_to_block(asmcfg_after.heads()[0]).lines[0].name == "PUSH"
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