"""Data flow analysis based on miasm intermediate representation""" from collections import namedtuple from miasm2.core.graph import DiGraph from miasm2.ir.ir import AssignBlock, IRBlock from miasm2.expression.expression import ExprLoc, ExprMem, ExprId, ExprInt from miasm2.expression.simplifications import expr_simp from miasm2.core.interval import interval class ReachingDefinitions(dict): """ Computes for each assignblock the set of reaching definitions. Example: IR block: lbl0: 0 A = 1 B = 3 1 B = 2 2 A = A + B + 4 Reach definition of lbl0: (lbl0, 0) => {} (lbl0, 1) => {A: {(lbl0, 0)}, B: {(lbl0, 0)}} (lbl0, 2) => {A: {(lbl0, 0)}, B: {(lbl0, 1)}} (lbl0, 3) => {A: {(lbl0, 2)}, B: {(lbl0, 1)}} Source set 'REACHES' in: Kennedy, K. (1979). A survey of data flow analysis techniques. IBM Thomas J. Watson Research Division, Algorithm MK This class is usable as a dictionnary whose struture is { (block, index): { lvalue: set((block, index)) } } """ ircfg = None def __init__(self, ircfg): super(ReachingDefinitions, self).__init__() self.ircfg = ircfg self.compute() def get_definitions(self, block_lbl, assignblk_index): """Returns the dict { lvalue: set((def_block_lbl, def_index)) } associated with self.ircfg.@block.assignblks[@assignblk_index] or {} if it is not yet computed """ return self.get((block_lbl, assignblk_index), {}) def compute(self): """This is the main fixpoint""" modified = True while modified: modified = False for block in self.ircfg.blocks.itervalues(): modified |= self.process_block(block) def process_block(self, block): """ Fetch reach definitions from predecessors and propagate it to the assignblk in block @block. """ predecessor_state = {} for pred_lbl in self.ircfg.predecessors(block.loc_key): pred = self.ircfg.blocks[pred_lbl] for lval, definitions in self.get_definitions(pred_lbl, len(pred)).iteritems(): predecessor_state.setdefault(lval, set()).update(definitions) modified = self.get((block.loc_key, 0)) != predecessor_state if not modified: return False self[(block.loc_key, 0)] = predecessor_state for index in xrange(len(block)): modified |= self.process_assignblock(block, index) return modified def process_assignblock(self, block, assignblk_index): """ Updates the reach definitions with values defined at assignblock @assignblk_index in block @block. NB: the effect of assignblock @assignblk_index in stored at index (@block, @assignblk_index + 1). """ assignblk = block[assignblk_index] defs = self.get_definitions(block.loc_key, assignblk_index).copy() for lval in assignblk: defs.update({lval: set([(block.loc_key, assignblk_index)])}) modified = self.get((block.loc_key, assignblk_index + 1)) != defs if modified: self[(block.loc_key, assignblk_index + 1)] = defs return modified ATTR_DEP = {"color" : "black", "_type" : "data"} AssignblkNode = namedtuple('AssignblkNode', ['label', 'index', 'var']) class DiGraphDefUse(DiGraph): """Representation of a Use-Definition graph as defined by Kennedy, K. (1979). A survey of data flow analysis techniques. IBM Thomas J. Watson Research Division. Example: IR block: lbl0: 0 A = 1 B = 3 1 B = 2 2 A = A + B + 4 Def use analysis: (lbl0, 0, A) => {(lbl0, 2, A)} (lbl0, 0, B) => {} (lbl0, 1, B) => {(lbl0, 2, A)} (lbl0, 2, A) => {} """ def __init__(self, reaching_defs, deref_mem=False, *args, **kwargs): """Instanciate a DiGraph @blocks: IR blocks """ self._edge_attr = {} # For dot display self._filter_node = None self._dot_offset = None self._blocks = reaching_defs.ircfg.blocks super(DiGraphDefUse, self).__init__(*args, **kwargs) self._compute_def_use(reaching_defs, deref_mem=deref_mem) def edge_attr(self, src, dst): """ Return a dictionary of attributes for the edge between @src and @dst @src: the source node of the edge @dst: the destination node of the edge """ return self._edge_attr[(src, dst)] def _compute_def_use(self, reaching_defs, deref_mem=False): for block in self._blocks.itervalues(): self._compute_def_use_block(block, reaching_defs, deref_mem=deref_mem) def _compute_def_use_block(self, block, reaching_defs, deref_mem=False): for index, assignblk in enumerate(block): assignblk_reaching_defs = reaching_defs.get_definitions(block.loc_key, index) for lval, expr in assignblk.iteritems(): self.add_node(AssignblkNode(block.loc_key, index, lval)) read_vars = expr.get_r(mem_read=deref_mem) if deref_mem and lval.is_mem(): read_vars.update(lval.arg.get_r(mem_read=deref_mem)) for read_var in read_vars: for reach in assignblk_reaching_defs.get(read_var, set()): self.add_data_edge(AssignblkNode(reach[0], reach[1], read_var), AssignblkNode(block.loc_key, index, lval)) def del_edge(self, src, dst): super(DiGraphDefUse, self).del_edge(src, dst) del self._edge_attr[(src, dst)] def add_uniq_labeled_edge(self, src, dst, edge_label): """Adds the edge (@src, @dst) with label @edge_label. if edge (@src, @dst) already exists, the previous label is overriden """ self.add_uniq_edge(src, dst) self._edge_attr[(src, dst)] = edge_label def add_data_edge(self, src, dst): """Adds an edge representing a data dependencie and sets the label accordingly""" self.add_uniq_labeled_edge(src, dst, ATTR_DEP) def node2lines(self, node): lbl, index, reg = node yield self.DotCellDescription(text="%s (%s)" % (lbl, index), attr={'align': 'center', 'colspan': 2, 'bgcolor': 'grey'}) src = self._blocks[lbl][index][reg] line = "%s = %s" % (reg, src) yield self.DotCellDescription(text=line, attr={}) yield self.DotCellDescription(text="", attr={}) def dead_simp_useful_assignblks(irarch, defuse, reaching_defs): """Mark useful statements using previous reach analysis and defuse Source : Kennedy, K. (1979). A survey of data flow analysis techniques. IBM Thomas J. Watson Research Division, Algorithm MK Return a set of triplets (block, assignblk number, lvalue) of useful definitions PRE: compute_reach(self) """ ircfg = reaching_defs.ircfg useful = set() for block_lbl, block in ircfg.blocks.iteritems(): successors = ircfg.successors(block_lbl) for successor in successors: if successor not in ircfg.blocks: keep_all_definitions = True break else: keep_all_definitions = False # Block has a nonexistant successor or is a leaf if keep_all_definitions or (len(successors) == 0): valid_definitions = reaching_defs.get_definitions(block_lbl, len(block)) for lval, definitions in valid_definitions.iteritems(): if lval in irarch.get_out_regs(block) or keep_all_definitions: for definition in definitions: useful.add(AssignblkNode(definition[0], definition[1], lval)) # Force keeping of specific cases for index, assignblk in enumerate(block): for lval, rval in assignblk.iteritems(): if (lval.is_mem() or irarch.IRDst == lval or lval.is_id("exception_flags") or rval.is_function_call()): useful.add(AssignblkNode(block_lbl, index, lval)) # Useful nodes dependencies for node in useful: for parent in defuse.reachable_parents(node): yield parent def dead_simp(irarch, ircfg): """ Remove useless affectations. This function is used to analyse relation of a * complete function * This means the blocks under study represent a solid full function graph. Source : Kennedy, K. (1979). A survey of data flow analysis techniques. IBM Thomas J. Watson Research Division, page 43 @ircfg: IntermediateRepresentation instance """ modified = False reaching_defs = ReachingDefinitions(ircfg) defuse = DiGraphDefUse(reaching_defs, deref_mem=True) useful = set(dead_simp_useful_assignblks(irarch, defuse, reaching_defs)) for block in ircfg.blocks.itervalues(): irs = [] for idx, assignblk in enumerate(block): new_assignblk = dict(assignblk) for lval in assignblk: if AssignblkNode(block.loc_key, idx, lval) not in useful: del new_assignblk[lval] modified = True irs.append(AssignBlock(new_assignblk, assignblk.instr)) ircfg.blocks[block.loc_key] = IRBlock(block.loc_key, irs) return modified def _test_merge_next_block(ircfg, loc_key): """ Test if the irblock at @loc_key can be merge with its son @ircfg: IRCFG instance @loc_key: LocKey instance of the candidate parent irblock """ if loc_key not in ircfg.blocks: return None sons = ircfg.successors(loc_key) if len(sons) != 1: return None son = list(sons)[0] if ircfg.predecessors(son) != [loc_key]: return None if son not in ircfg.blocks: return None return son def _do_merge_blocks(ircfg, loc_key, son_loc_key): """ Merge two irblocks at @loc_key and @son_loc_key @ircfg: DiGrpahIR @loc_key: LocKey instance of the parent IRBlock @loc_key: LocKey instance of the son IRBlock """ assignblks = [] for assignblk in ircfg.blocks[loc_key]: if ircfg.IRDst not in assignblk: assignblks.append(assignblk) continue affs = {} for dst, src in assignblk.iteritems(): if dst != ircfg.IRDst: affs[dst] = src if affs: assignblks.append(AssignBlock(affs, assignblk.instr)) assignblks += ircfg.blocks[son_loc_key].assignblks new_block = IRBlock(loc_key, assignblks) ircfg.discard_edge(loc_key, son_loc_key) for son_successor in ircfg.successors(son_loc_key): ircfg.add_uniq_edge(loc_key, son_successor) ircfg.discard_edge(son_loc_key, son_successor) del ircfg.blocks[son_loc_key] ircfg.del_node(son_loc_key) ircfg.blocks[loc_key] = new_block def _test_jmp_only(ircfg, loc_key): """ If irblock at @loc_key sets only IRDst to an ExprLoc, return the corresponding loc_key target. None in other cases. @ircfg: IRCFG instance @loc_key: LocKey instance of the candidate irblock """ if loc_key not in ircfg.blocks: return None irblock = ircfg.blocks[loc_key] if len(irblock.assignblks) != 1: return None items = dict(irblock.assignblks[0]).items() if len(items) != 1: return None dst, src = items[0] assert dst.is_id("IRDst") if not src.is_loc(): return None return src.loc_key def _relink_block_node(ircfg, loc_key, son_loc_key, replace_dct): """ Link loc_key's parents to parents directly to son_loc_key """ for parent in set(ircfg.predecessors(loc_key)): parent_block = ircfg.blocks.get(parent, None) if parent_block is None: continue new_block = parent_block.modify_exprs( lambda expr:expr.replace_expr(replace_dct), lambda expr:expr.replace_expr(replace_dct) ) # Link parent to new dst ircfg.add_uniq_edge(parent, son_loc_key) # Unlink block ircfg.blocks[new_block.loc_key] = new_block ircfg.del_node(loc_key) def _remove_to_son(ircfg, loc_key, son_loc_key): """ Merge irblocks; The final block has the @son_loc_key loc_key Update references Condition: - irblock at @loc_key is a pure jump block - @loc_key is not an entry point (can be removed) @irblock: IRCFG instance @loc_key: LocKey instance of the parent irblock @son_loc_key: LocKey instance of the son irblock """ # Ircfg loop => don't mess if loc_key == son_loc_key: return False # Unlink block destinations ircfg.del_edge(loc_key, son_loc_key) del ircfg.blocks[loc_key] replace_dct = { ExprLoc(loc_key, ircfg.IRDst.size):ExprLoc(son_loc_key, ircfg.IRDst.size) } _relink_block_node(ircfg, loc_key, son_loc_key, replace_dct) return True def _remove_to_parent(ircfg, loc_key, son_loc_key): """ Merge irblocks; The final block has the @loc_key loc_key Update references Condition: - irblock at @loc_key is a pure jump block - @son_loc_key is not an entry point (can be removed) @irblock: IRCFG instance @loc_key: LocKey instance of the parent irblock @son_loc_key: LocKey instance of the son irblock """ # Ircfg loop => don't mess if loc_key == son_loc_key: return False # Unlink block destinations ircfg.del_edge(loc_key, son_loc_key) old_irblock = ircfg.blocks[son_loc_key] new_irblock = IRBlock(loc_key, old_irblock.assignblks) ircfg.blocks[son_loc_key] = new_irblock del ircfg.blocks[son_loc_key] ircfg.add_irblock(new_irblock) replace_dct = { ExprLoc(son_loc_key, ircfg.IRDst.size):ExprLoc(loc_key, ircfg.IRDst.size) } _relink_block_node(ircfg, son_loc_key, loc_key, replace_dct) return True def merge_blocks(ircfg, loc_key_entries): """ This function modifies @ircfg to apply the following transformations: - group an irblock with its son if the irblock has one and only one son and this son has one and only one parent (spaghetti code). - if an irblock is only made of an assignment to IRDst with a given label, this irblock is dropped and its parent destination targets are updated. The irblock must have a parent (avoid deleting the function head) - if an irblock is a head of the graph and is only made of an assignment to IRDst with a given label, this irblock is dropped and its son becomes the head. References are fixed Return True if at least an irblock has been modified @ircfg: IRCFG instance @loc_key_entries: loc_key to keep """ modified = False todo = set(ircfg.nodes()) while todo: loc_key = todo.pop() # Test merge block son = _test_merge_next_block(ircfg, loc_key) if son is not None and son not in loc_key_entries: _do_merge_blocks(ircfg, loc_key, son) todo.add(loc_key) modified = True continue # Test jmp only block son = _test_jmp_only(ircfg, loc_key) if son is not None and loc_key not in loc_key_entries: ret = _remove_to_son(ircfg, loc_key, son) modified |= ret if ret: todo.add(loc_key) continue # Test head jmp only block if (son is not None and son not in loc_key_entries and son in ircfg.blocks): # jmp only test done previously ret = _remove_to_parent(ircfg, loc_key, son) modified |= ret if ret: todo.add(loc_key) continue return modified def remove_empty_assignblks(ircfg): """ Remove empty assignblks in irblocks of @ircfg Return True if at least an irblock has been modified @ircfg: IRCFG instance """ modified = False for loc_key, block in ircfg.blocks.iteritems(): irs = [] for assignblk in block: if len(assignblk): irs.append(assignblk) else: modified = True ircfg.blocks[loc_key] = IRBlock(loc_key, irs) return modified class SSADefUse(DiGraph): """ Generate DefUse information from SSA transformation Links are not valid for ExprMem. """ def add_var_def(self, node, src): lbl, index, dst = node index2dst = self._links.setdefault(lbl, {}) dst2src = index2dst.setdefault(index, {}) dst2src[dst] = src def add_def_node(self, def_nodes, node, src): lbl, index, dst = node if dst.is_id(): def_nodes[dst] = node def add_use_node(self, use_nodes, node, src): lbl, index, dst = node sources = set() if dst.is_mem(): sources.update(dst.arg.get_r(mem_read=True)) sources.update(src.get_r(mem_read=True)) for source in sources: if not source.is_mem(): use_nodes.setdefault(source, set()).add(node) def get_node_target(self, node): lbl, index, reg = node return self._links[lbl][index][reg] def set_node_target(self, node, src): lbl, index, reg = node self._links[lbl][index][reg] = src @classmethod def from_ssa(cls, ssa): """ Return a DefUse DiGraph from a SSA graph @ssa: SSADiGraph instance """ graph = cls() # First pass # Link line to its use and def def_nodes = {} use_nodes = {} graph._links = {} for lbl in ssa.graph.nodes(): block = ssa.graph.blocks.get(lbl, None) if block is None: continue for index, assignblk in enumerate(block): for dst, src in assignblk.iteritems(): node = lbl, index, dst graph.add_var_def(node, src) graph.add_def_node(def_nodes, node, src) graph.add_use_node(use_nodes, node, src) for dst, node in def_nodes.iteritems(): graph.add_node(node) if dst not in use_nodes: continue for use in use_nodes[dst]: graph.add_uniq_edge(node, use) return graph def expr_test_visit(expr, test): result = set() expr.visit( lambda expr: expr, lambda expr: test(expr, result) ) if result: return True else: return False def expr_has_mem_test(expr, result): if result: # Don't analyse if we already found a candidate return False if expr.is_mem(): result.add(expr) return False return True def expr_has_mem(expr): """ Return True if expr contains at least one memory access @expr: Expr instance """ return expr_test_visit(expr, expr_has_mem_test) def expr_has_call_test(expr, result): if result: # Don't analyse if we already found a candidate return False if expr.is_op() and expr.op.startswith("call"): result.add(expr) return False return True def expr_has_call(expr): """ Return True if expr contains at least one "call" operator @expr: Expr instance """ return expr_test_visit(expr, expr_has_call_test) class PropagateExpr(object): def assignblk_is_propagation_barrier(self, assignblk): for dst, src in assignblk.iteritems(): if expr_has_call(src): return True if dst.is_mem(): return True return False def has_propagation_barrier(self, assignblks): for assignblk in assignblks: for dst, src in assignblk.iteritems(): if expr_has_call(src): return True if dst.is_mem(): return True return False def is_mem_written(self, ssa, node, successor): loc_a, index_a, reg_a = node loc_b, index_b, reg_b = successor block_b = ssa.graph.blocks[loc_b] nodes_to_do = self.compute_reachable_nodes_from_a_to_b(ssa.graph, loc_a, loc_b) if loc_a == loc_b: # src is dst assert nodes_to_do == set([loc_a]) if self.has_propagation_barrier(block_b.assignblks[index_a:index_b]): return True else: # Check everyone but loc_a and loc_b for loc in nodes_to_do - set([loc_a, loc_b]): block = ssa.graph.blocks[loc] if self.has_propagation_barrier(block.assignblks): return True # Check loc_a partially block_a = ssa.graph.blocks[loc_a] if self.has_propagation_barrier(block_a.assignblks[index_a:]): return True if nodes_to_do.intersection(ssa.graph.successors(loc_b)): # There is a path from loc_b to loc_b => Check loc_b fully if self.has_propagation_barrier(block_b.assignblks): return True else: # Check loc_b partially if self.has_propagation_barrier(block_b.assignblks[:index_b]): return True return False def compute_reachable_nodes_from_a_to_b(self, ssa, loc_a, loc_b): reachables_a = set(ssa.reachable_sons(loc_a)) reachables_b = set(ssa.reachable_parents_stop_node(loc_b, loc_a)) return reachables_a.intersection(reachables_b) def propagation_allowed(self, ssa, to_replace, node_a, node_b): """ Return True if we can replace @node source into @node_b """ loc_a, index_a, reg_a = node_a if not expr_has_mem(to_replace[reg_a]): return True if self.is_mem_written(ssa, node_a, node_b): return False return True def propagate(self, ssa, head): defuse = SSADefUse.from_ssa(ssa) to_replace = {} node_to_reg = {} for node in defuse.nodes(): lbl, index, reg = node src = defuse.get_node_target(node) if expr_has_call(src): continue if src.is_op('Phi'): continue if reg.is_mem(): continue to_replace[reg] = src node_to_reg[node] = reg modified = False for node, reg in node_to_reg.iteritems(): src = to_replace[reg] for successor in defuse.successors(node): if not self.propagation_allowed(ssa, to_replace, node, successor): continue loc_a, index_a, reg_a = node loc_b, index_b, reg_b = successor block = ssa.graph.blocks[loc_b] replace = {reg_a: to_replace[reg_a]} # Replace assignblks = list(block) assignblk = block[index_b] out = {} for dst, src in assignblk.iteritems(): if src.is_op('Phi'): out[dst] = src continue if src.is_mem(): ptr = src.arg ptr = ptr.replace_expr(replace) new_src = ExprMem(ptr, src.size) else: new_src = src.replace_expr(replace) if dst.is_id(): new_dst = dst elif dst.is_mem(): ptr = dst.arg ptr = ptr.replace_expr(replace) new_dst = ExprMem(ptr, dst.size) else: new_dst = dst.replace_expr(replace) if not (new_dst.is_id() or new_dst.is_mem()): new_dst = dst if src != new_src or dst != new_dst: modified = True out[new_dst] = new_src out = AssignBlock(out, assignblk.instr) assignblks[index_b] = out new_block = IRBlock(block.loc_key, assignblks) ssa.graph.blocks[block.loc_key] = new_block return modified def stack_to_reg(expr): if expr.is_mem(): ptr = expr.arg SP = ir_arch_a.sp if ptr == SP: return ExprId("STACK.0", expr.size) elif (ptr.is_op('+') and len(ptr.args) == 2 and ptr.args[0] == SP and ptr.args[1].is_int()): diff = int(ptr.args[1]) assert diff % 4 == 0 diff = (0 - diff) & 0xFFFFFFFF return ExprId("STACK.%d" % (diff / 4), expr.size) return False def is_stack_access(ir_arch_a, expr): if not expr.is_mem(): return False ptr = expr.arg diff = expr_simp(ptr - ir_arch_a.sp) if not diff.is_int(): return False return expr def visitor_get_stack_accesses(ir_arch_a, expr, stack_vars): if is_stack_access(ir_arch_a, expr): stack_vars.add(expr) return expr def get_stack_accesses(ir_arch_a, expr): result = set() expr.visit(lambda expr:visitor_get_stack_accesses(ir_arch_a, expr, result)) return result def get_interval_length(interval_in): length = 0 for start, stop in interval_in.intervals: length += stop + 1 - start return length def check_expr_below_stack(ir_arch_a, expr): """ Return False if expr pointer is below original stack pointer @ir_arch_a: ira instance @expr: Expression instance """ ptr = expr.arg diff = expr_simp(ptr - ir_arch_a.sp) if not diff.is_int(): return True if int(diff) == 0 or int(expr_simp(diff.msb())) == 0: return False return True def retrieve_stack_accesses(ir_arch_a, ssa): """ Walk the ssa graph and find stack based variables. Return a dictionnary linking stack base address to its size/name @ir_arch_a: ira instance @ssa: SSADiGraph instance """ stack_vars = set() for block in ssa.graph.blocks.itervalues(): for assignblk in block: for dst, src in assignblk.iteritems(): stack_vars.update(get_stack_accesses(ir_arch_a, dst)) stack_vars.update(get_stack_accesses(ir_arch_a, src)) stack_vars = filter(lambda expr: check_expr_below_stack(ir_arch_a, expr), stack_vars) base_to_var = {} for var in stack_vars: base_to_var.setdefault(var.arg, set()).add(var) base_to_interval = {} for addr, vars in base_to_var.iteritems(): var_interval = interval() for var in vars: offset = expr_simp(addr - ir_arch_a.sp) if not offset.is_int(): # skip non linear stack offset continue start = int(offset) stop = int(expr_simp(offset + ExprInt(var.size / 8, offset.size))) mem = interval([(start, stop-1)]) var_interval += mem base_to_interval[addr] = var_interval if not base_to_interval: return {} # Check if not intervals overlap _, tmp = base_to_interval.popitem() while base_to_interval: addr, mem = base_to_interval.popitem() assert (tmp & mem).empty tmp += mem base_to_info = {} base_to_name = {} for addr, vars in base_to_var.iteritems(): name = "var_%d" % (len(base_to_info)) size = max([var.size for var in vars]) base_to_info[addr] = size, name return base_to_info def fix_stack_vars(expr, base_to_info): """ Replace local stack accesses in expr using informations in @base_to_info @expr: Expression instance @base_to_info: dictionnary linking stack base address to its size/name """ if not expr.is_mem(): return expr ptr = expr.arg if ptr not in base_to_info: return expr size, name = base_to_info[ptr] var = ExprId(name, size) if size == expr.size: return var assert expr.size < size return var[:expr.size] def replace_mem_stack_vars(expr, base_to_info): return expr.visit(lambda expr:fix_stack_vars(expr, base_to_info)) def replace_stack_vars(ir_arch_a, ssa): """ Try to replace stack based memory accesses by variables. WARNING: may fail @ir_arch_a: ira instance @ssa: SSADiGraph instance """ defuse = SSADefUse.from_ssa(ssa) base_to_info = retrieve_stack_accesses(ir_arch_a, ssa) stack_vars = {} modified = False for block in ssa.graph.blocks.itervalues(): assignblks = [] for assignblk in block: out = {} for dst, src in assignblk.iteritems(): new_dst = dst.visit(lambda expr:replace_mem_stack_vars(expr, base_to_info)) new_src = src.visit(lambda expr:replace_mem_stack_vars(expr, base_to_info)) if new_dst != dst or new_src != src: modified |= True out[new_dst] = new_src out = AssignBlock(out, assignblk.instr) assignblks.append(out) new_block = IRBlock(block.loc_key, assignblks) ssa.graph.blocks[block.loc_key] = new_block return modified def memlookup_test(expr, bs, is_addr_ro_variable, result): if expr.is_mem() and expr.arg.is_int(): ptr = int(expr.arg) if is_addr_ro_variable(bs, ptr, expr.size): result.add(expr) return False return True def memlookup_visit(expr, bs, is_addr_ro_variable): result = set() expr.visit(lambda expr: expr, lambda expr: memlookup_test(expr, bs, is_addr_ro_variable, result)) return result def get_memlookup(expr, bs, is_addr_ro_variable): return memlookup_visit(expr, bs, is_addr_ro_variable) def read_mem(bs, expr): ptr = int(expr.arg) var_bytes = bs.getbytes(ptr, expr.size / 8)[::-1] try: value = int(var_bytes.encode('hex'), 16) except: return expr return ExprInt(value, expr.size) def load_from_int(ir_arch, bs, is_addr_ro_variable): """ Replace memory read based on constant with static value @ir_arch: ira instance @bs: binstream instance @is_addr_ro_variable: callback(addr, size) to test memory candidate """ modified = False for label, block in ir_arch.blocks.iteritems(): assignblks = list() for assignblk in block: out = {} for dst, src in assignblk.iteritems(): # Test src mems = get_memlookup(src, bs, is_addr_ro_variable) src_new = src if mems: replace = {} for mem in mems: value = read_mem(bs, mem) replace[mem] = value src_new = src.replace_expr(replace) if src_new != src: modified = True # Test dst pointer if dst is mem if dst.is_mem(): ptr = dst.arg mems = get_memlookup(ptr, bs, is_addr_ro_variable) ptr_new = ptr if mems: replace = {} for mem in mems: value = read_mem(bs, mem) replace[mem] = value ptr_new = ptr.replace_expr(replace) if ptr_new != ptr: modified = True dst = ExprMem(ptr_new, dst.size) out[dst] = src_new out = AssignBlock(out, assignblk.instr) assignblks.append(out) block = IRBlock(block.loc_key, assignblks) ir_arch.blocks[block.loc_key] = block return modified