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"Helper to quickly build instruction's semantic side effects"
import inspect
import ast
import re
import miasm2.expression.expression as m2_expr
from miasm2.ir.ir import irbloc
class MiasmTransformer(ast.NodeTransformer):
"""AST visitor translating DSL to Miasm expression
memX[Y] -> ExprMem(Y, X)
iX(Y) -> ExprIntX(Y)
X if Y else Z -> ExprCond(Y, X, Z)
'X'(Y) -> ExprOp('X', Y)
('X' % Y)(Z) -> ExprOp('X' % Y, Z)
"""
# Parsers
parse_integer = re.compile("^i([0-9]+)$")
parse_mem = re.compile("^mem([0-9]+)$")
# Visitors
def visit_Call(self, node):
"""iX(Y) -> ExprIntX(Y),
'X'(Y) -> ExprOp('X', Y), ('X' % Y)(Z) -> ExprOp('X' % Y, Z)"""
if isinstance(node.func, ast.Name):
# iX(Y) -> ExprIntX(Y)
fc_name = node.func.id
# Match the function name
new_name = fc_name
integer = self.parse_integer.search(fc_name)
# Do replacement
if integer is not None:
new_name = "ExprInt%s" % integer.groups()[0]
# Replace in the node
node.func.id = new_name
elif (isinstance(node.func, ast.Str) or
(isinstance(node.func, ast.BinOp) and
isinstance(node.func.op, ast.Mod) and
isinstance(node.func.left, ast.Str))):
# 'op'(args...) -> ExprOp('op', args...)
# ('op' % (fmt))(args...) -> ExprOp('op' % (fmt), args...)
op_name = node.func
# Do replacement
node.func = ast.Name(id="ExprOp", ctx=ast.Load())
node.args[0:0] = [op_name]
node.args = map(self.visit, node.args)
else:
# TODO: launch visitor on node
pass
return node
def visit_Subscript(self, node):
"""memX[Y] -> ExprMem(Y, X)"""
# Detect the syntax
if not isinstance(node.value, ast.Name):
return node
name = node.value.id
mem = self.parse_mem.search(name)
if mem is None:
# TODO: launch visitor on node
return node
# Do replacement
addr = self.visit(node.slice.value)
call = ast.Call(func=ast.Name(id='ExprMem', ctx=ast.Load()),
args=[addr, ast.Num(n=int(mem.groups()[0]))],
keywords=[], starargs=None, kwargs=None)
return call
def visit_IfExp(self, node):
"""X if Y else Z -> ExprCond(Y, X, Z)"""
call = ast.Call(func=ast.Name(id='ExprCond', ctx=ast.Load()),
args=[self.visit(node.test),
self.visit(node.body),
self.visit(node.orelse)],
keywords=[], starargs=None, kwargs=None)
return call
class SemBuilder(object):
"""Helper for building instruction's semantic side effects method
This class provides a decorator @parse to use on them.
The context in which the function will be parsed must be supplied on
instanciation
"""
def __init__(self, ctx):
"""Create a SemBuilder
@ctx: context dictionnary used during parsing
"""
# Init
self.transformer = MiasmTransformer()
self._ctx = dict(m2_expr.__dict__)
self._ctx["irbloc"] = irbloc
self._functions = {}
# Update context
self._ctx.update(ctx)
@property
def functions(self):
"""Return a dictionnary name -> func of parsed functions"""
return self._functions.copy()
def parse(self, func):
"""Function decorator, returning a correct method from a pseudo-Python
one"""
# Get the function AST
parsed = ast.parse(inspect.getsource(func))
fc_ast = parsed.body[0]
argument_names = [name.id for name in fc_ast.args.args]
body = []
# AffBlock of the current instruction
new_ast = []
for statement in fc_ast.body:
if isinstance(statement, ast.Assign):
src = self.transformer.visit(statement.value)
dst = self.transformer.visit(statement.targets[0])
if (isinstance(dst, ast.Name) and
dst.id not in argument_names and
dst.id not in self._ctx):
# Real variable declaration
statement.value = src
body.append(statement)
continue
dst.ctx = ast.Load()
res = ast.Call(func=ast.Name(id='ExprAff',
ctx=ast.Load()),
args=[dst, src],
keywords=[],
starargs=None,
kwargs=None)
new_ast.append(res)
elif (isinstance(statement, ast.Expr) and
isinstance(statement.value, ast.Str)):
# String (docstring, comment, ...) -> keep it
body.append(statement)
else:
# TODO: real var, +=, /=, -=, <<=, >>=, if/else, ...
raise RuntimeError("Unimplemented %s" % statement)
# Build the new function
fc_ast.args.args[0:0] = [ast.Name(id='ir', ctx=ast.Param()),
ast.Name(id='instr', ctx=ast.Param())]
body.append(ast.Return(value=ast.Tuple(elts=[ast.List(elts=new_ast,
ctx=ast.Load()),
ast.List(elts=[],
ctx=ast.Load())],
ctx=ast.Load())))
ret = ast.Module([ast.FunctionDef(name=fc_ast.name,
args=fc_ast.args,
body=body,
decorator_list=[])])
# To display the generated function, use codegen.to_source
# codegen: https://github.com/andreif/codegen
# Compile according to the context
fixed = ast.fix_missing_locations(ret)
codeobj = compile(fixed, '<string>', 'exec')
ctx = self._ctx.copy()
eval(codeobj, ctx)
# Get the function back
self._functions[fc_ast.name] = ctx[fc_ast.name]
return ctx[fc_ast.name]
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