bool SymEval::expand(Result_t &res,
std::set<InstructionPtr> &failedInsns,
bool applyVisitors) {
// Symbolic evaluation works off an Instruction
// so we have something to hand to ROSE.
failedInsns.clear();
for (Result_t::iterator i = res.begin(); i != res.end(); ++i) {
if (i->second != AST::Ptr()) {
// Must've already filled it in from a previous instruction crack
continue;
}
Assignment::Ptr ptr = i->first;
bool success = expandInsn(ptr->insn(),
ptr->addr(),
res);
if (!success) failedInsns.insert(ptr->insn());
}
if (applyVisitors) {
// Must apply the visitor to each filled in element
for (Result_t::iterator i = res.begin(); i != res.end(); ++i) {
if (!i->second) continue;
AST::Ptr tmp = simplifyStack(i->second, i->first->addr(), i->first->func(), i->first->block());
BooleanVisitor b;
AST::Ptr tmp2 = tmp->accept(&b);
i->second = tmp2;
}
}
return (failedInsns.empty());
}
SymEvalPolicy::SymEvalPolicy(Result_t &r,
Address a,
Dyninst::Architecture ac,
Instruction::Ptr insn) :
res(r),
arch(ac),
addr(a),
ip_(Handle<32>(wrap(Absloc::makePC(arch)))),
failedTranslate_(false),
insn_(insn) {
// We also need to build aaMap FTW!!!
for (Result_t::iterator iter = r.begin();
iter != r.end(); ++iter) {
Assignment::Ptr a = iter->first;
// For a different instruction...
if (a->addr() != addr) continue;
AbsRegion &o = a->out();
if (o.containsOfType(Absloc::Register)) {
// We're assuming this is a single register...
//std::cerr << "Marking register " << a << std::endl;
aaMap[o.absloc()] = a;
}
else {
// Use sufficiently-unique (Heap,0) Absloc
// to represent a definition to a memory absloc
aaMap[Absloc(0)] = a;
}
}
}
void AssignmentConverter::handlePushEquivalent(const Instruction::Ptr I,
Address addr,
ParseAPI::Function *func,
ParseAPI::Block *block,
std::vector<AbsRegion> &operands,
std::vector<Assignment::Ptr> &assignments) {
// The handled-in operands are used to define *SP
// And then we update SP
AbsRegion stackTop = aConverter.stack(addr, func, block, true);
AbsRegion sp(Absloc::makeSP(func->isrc()->getArch()));
Assignment::Ptr spA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
stackTop));
spA->addInputs(operands);
spA->addInput(sp);
Assignment::Ptr spB = Assignment::Ptr(new Assignment(I, addr, func, block, sp));
spB->addInput(sp);
assignments.push_back(spA);
assignments.push_back(spB);
}
pair<AST::Ptr, bool> BoundFactsCalculator::ExpandAssignment(Assignment::Ptr assign) {
parsing_printf("Expand assignment : %s Instruction: %s\n", assign->format().c_str(), assign->insn()->format().c_str());
if (expandCache.find(assign) != expandCache.end()) {
AST::Ptr ast = expandCache[assign];
if (ast) return make_pair(ast, true); else return make_pair(ast, false);
} else {
pair<AST::Ptr, bool> expandRet = SymEval::expand(assign, false);
if (expandRet.second && expandRet.first) {
parsing_printf("Original expand: %s\n", expandRet.first->format().c_str());
AST::Ptr calculation = SimplifyAnAST(expandRet.first, assign->insn()->size());
expandCache[assign] = calculation;
} else {
expandCache[assign] = AST::Ptr();
}
return make_pair( expandCache[assign], expandRet.second );
}
}
bool IndirectControlFlowAnalyzer::IsZeroExtend(Assignment::Ptr memLoc) {
if (!memLoc) {
parsing_printf("\tmemLoc is null\n");
return false;
}
Instruction i = memLoc->insn();
parsing_printf("check zero extend %s\n", i.format().c_str());
if (i.format().find("movz") != string::npos) return true;
return false;
}
void AssignmentConverter::handlePopEquivalent(const Instruction::Ptr I,
Address addr,
ParseAPI::Function *func,
ParseAPI::Block *block,
std::vector<AbsRegion> &operands,
std::vector<Assignment::Ptr> &assignments) {
// We use the top of the stack and any operands beyond the first.
// (Can you pop into memory?)
AbsRegion stackTop = aConverter.stack(addr, func, block, false);
AbsRegion sp(Absloc::makeSP(func->isrc()->getArch()));
Assignment::Ptr spA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
operands[0]));
spA->addInput(stackTop);
spA->addInput(sp);
for (unsigned i = 1; i < operands.size(); i++) {
spA->addInput(operands[i]);
}
// Now stack assignment
Assignment::Ptr spB = Assignment::Ptr(new Assignment(I, addr, func, block, sp));
spB->addInput(sp);
assignments.push_back(spA);
assignments.push_back(spB);
}
int IndirectControlFlowAnalyzer::GetMemoryReadSize(Assignment::Ptr memLoc) {
if (!memLoc) {
parsing_printf("\tmemLoc is null\n");
return 0;
}
Instruction i = memLoc->insn();
std::vector<Operand> ops;
i.getOperands(ops);
parsing_printf("\t there are %d operands\n", ops.size());
for (auto oit = ops.begin(); oit != ops.end(); ++oit) {
Operand o = *oit;
if (o.readsMemory()) {
Expression::Ptr exp = o.getValue();
return exp->size();
}
}
return 0;
}
void AssignmentConverter::convert(const Instruction::Ptr I,
const Address &addr,
ParseAPI::Function *func,
ParseAPI::Block *block,
std::vector<Assignment::Ptr> &assignments) {
assignments.clear();
if (cache(func, addr, assignments)) return;
// Decompose the instruction into a set of abstract assignments.
// We don't have the Definition class concept yet, so we'll do the
// hard work here.
// Two phases:
// 1) Special-cased for IA32 multiple definition instructions,
// based on the opcode of the instruction
// 2) Generic handling for things like flags and the PC.
// Non-PC handling section
switch(I->getOperation().getID()) {
case e_push: {
// SP = SP - 4
// *SP = <register>
std::vector<Operand> operands;
I->getOperands(operands);
// According to the InstructionAPI, the first operand will be the argument, the second will be ESP.
assert(operands.size() == 2);
// The argument can be any of the following:
// 1) a register (push eax);
// 2) an immediate value (push $deadbeef)
// 3) a memory location.
std::vector<AbsRegion> oper0;
aConverter.convertAll(operands[0].getValue(),
addr,
func,
block,
oper0);
handlePushEquivalent(I, addr, func, block, oper0, assignments);
break;
}
case e_call: {
// This can be seen as a push of the PC...
std::vector<AbsRegion> pcRegion;
pcRegion.push_back(Absloc::makePC(func->isrc()->getArch()));
Absloc sp = Absloc::makeSP(func->isrc()->getArch());
handlePushEquivalent(I, addr, func, block, pcRegion, assignments);
// Now for the PC definition
// Assume full intra-dependence of non-flag and non-pc registers.
std::vector<AbsRegion> used;
std::vector<AbsRegion> defined;
aConverter.convertAll(I,
addr,
func,
block,
used,
defined);
Assignment::Ptr a = Assignment::Ptr(new Assignment(I, addr, func, block, pcRegion[0]));
if (!used.empty()) {
for(std::vector<AbsRegion>::const_iterator u = used.begin();
u != used.end();
++u)
{
if(!(u->contains(pcRegion[0])) &&
!(u->contains(sp)))
{
a->addInput(*u);
}
}
}
else {
a->addInputs(pcRegion);
}
assignments.push_back(a);
break;
}
case e_pop: {
// <reg> = *SP
// SP = SP + 4/8
// Amusingly... this doesn't have an intra-instruction dependence. It should to enforce
// the order that <reg> = *SP happens before SP = SP - 4, but since the input to both
// uses of SP in this case are the, well, input values... no "sideways" edges.
// However, we still special-case it so that SP doesn't depend on the incoming stack value...
// Also, we use the same logic for return, defining it as
// PC = *SP
// SP = SP + 4/8
// As with push, eSP shows up as operand 1.
std::vector<Operand> operands;
I->getOperands(operands);
// According to the InstructionAPI, the first operand will be the explicit register, the second will be ESP.
assert(operands.size() == 2);
std::vector<AbsRegion> oper0;
aConverter.convertAll(operands[0].getValue(),
addr,
func,
block,
oper0);
handlePopEquivalent(I, addr, func, block, oper0, assignments);
break;
}
case e_leave: {
// a leave is equivalent to:
// mov ebp, esp
// pop ebp
// From a definition POV, we have the following:
// SP = BP
// BP = *SP
// BP STACK[newSP]
// | |
// v v
// SP -> BP
// This is going to give the stack analysis fits... for now, I think it just reverts the
// stack depth to 0.
// TODO FIXME update stack analysis to make this really work.
AbsRegion sp(Absloc::makeSP(func->isrc()->getArch()));
AbsRegion fp(Absloc::makeFP(func->isrc()->getArch()));
// Should be "we assign SP using FP"
Assignment::Ptr spA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
sp));
spA->addInput(fp);
// And now we want "FP = (stack slot -2*wordsize)"
/*
AbsRegion stackTop(Absloc(0,
0,
func));
*/
// Actually, I think this is ebp = pop esp === ebp = pop ebp
Assignment::Ptr fpA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
fp));
//fpA->addInput(aConverter.stack(addr + I->size(), func, false));
fpA->addInput(aConverter.frame(addr, func, block, false));
assignments.push_back(spA);
assignments.push_back(fpA);
break;
}
case e_ret_near:
case e_ret_far: {
// PC = *SP
// SP = SP + 4/8
// Like pop, except it's all implicit.
AbsRegion pc = AbsRegion(Absloc::makePC(func->isrc()->getArch()));
Assignment::Ptr pcA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
pc));
pcA->addInput(aConverter.stack(addr, func, block, false));
AbsRegion sp = AbsRegion(Absloc::makeSP(func->isrc()->getArch()));
Assignment::Ptr spA = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
sp));
spA->addInput(sp);
assignments.push_back(pcA);
assignments.push_back(spA);
break;
}
case e_xchg: {
// xchg defines two abslocs, and uses them as appropriate...
std::vector<Operand> operands;
I->getOperands(operands);
// According to the InstructionAPI, the first operand will be the argument, the second will be ESP.
assert(operands.size() == 2);
// We use the first to define the second, and vice versa
std::vector<AbsRegion> oper0;
aConverter.convertAll(operands[0].getValue(),
addr,
func,
block,
oper0);
std::vector<AbsRegion> oper1;
aConverter.convertAll(operands[1].getValue(),
addr,
func,
block,
oper1);
// Okay. We may have a memory reference in here, which will
// cause either oper0 or oper1 to have multiple entries (the
// remainder will be registers). So. Use everything from oper1
// to define oper0[0], and vice versa.
Assignment::Ptr a = Assignment::Ptr(new Assignment(I, addr, func, block, oper0[0]));
a->addInputs(oper1);
Assignment::Ptr b = Assignment::Ptr(new Assignment(I, addr, func, block, oper1[0]));
b->addInputs(oper0);
assignments.push_back(a);
assignments.push_back(b);
break;
}
case power_op_stwu: {
std::vector<Operand> operands;
I->getOperands(operands);
// stwu <a>, <b>, <c>
// <a> = R1
// <b> = -16(R1)
// <c> = R1
// From this, R1 <= R1 - 16; -16(R1) <= R1
// So a <= b (without a deref)
// deref(b) <= c
std::set<Expression::Ptr> writes;
I->getMemoryWriteOperands(writes);
assert(writes.size() == 1);
Expression::Ptr tmp = *(writes.begin());
AbsRegion effAddr = aConverter.convert(tmp,
addr,
func,
block);
std::vector<AbsRegion> regions;
aConverter.convertAll(operands[0].getValue(), addr, func, block, regions);
AbsRegion RS = regions[0];
regions.clear();
aConverter.convertAll(operands[2].getValue(), addr, func, block, regions);
AbsRegion RA = regions[0];
Assignment::Ptr mem = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
effAddr));
mem->addInput(RS);
Assignment::Ptr ra = Assignment::Ptr(new Assignment(I,
addr,
func,
block,
RA));
ra->addInput(RS);
assignments.push_back(mem);
assignments.push_back(ra);
break;
}
default:
// Assume full intra-dependence of non-flag and non-pc registers.
std::vector<AbsRegion> used;
std::vector<AbsRegion> defined;
aConverter.convertAll(I,
addr,
func,
block,
used,
defined);
for (std::vector<AbsRegion>::const_iterator i = defined.begin();
i != defined.end(); ++i) {
Assignment::Ptr a = Assignment::Ptr(new Assignment(I, addr, func, block, *i));
a->addInputs(used);
assignments.push_back(a);
}
break;
}
// Now for flags...
// According to Matt, the easiest way to represent dependencies for flags on
// IA-32/AMD-64 is to have them depend on the inputs to the instruction and
// not the outputs of the instruction; therefore, there's no intra-instruction
// dependence.
// PC-handling section
// Most instructions use the PC to set the PC. This includes calls, relative branches,
// and the like. So we're basically looking for indirect branches or absolute branches.
// (are there absolutes on IA-32?).
// Also, conditional branches and the flag registers they use.
if (cacheEnabled_) {
cache_[func][addr] = assignments;
}
}
SymEval::Retval_t SymEval::process(SliceNode::Ptr ptr,
Result_t &dbase,
std::set<Edge::Ptr> &skipEdges) {
bool failedTranslation;
bool skippedEdge = false;
bool skippedInput = false;
bool success = false;
std::map<const AbsRegion*, std::set<Assignment::Ptr> > inputMap;
expand_cerr << "Calling process on " << ptr->format() << endl;
// Don't try an expansion of a widen node...
if (!ptr->assign()) return WIDEN_NODE;
EdgeIterator begin, end;
ptr->ins(begin, end);
for (; begin != end; ++begin) {
SliceEdge::Ptr edge = boost::static_pointer_cast<SliceEdge>(*begin);
SliceNode::Ptr source = boost::static_pointer_cast<SliceNode>(edge->source());
// Skip this one to break a cycle.
if (skipEdges.find(edge) != skipEdges.end()) {
expand_cerr << "In process, skipping edge from "
<< source->format() << endl;
skippedEdge = true;
continue;
}
Assignment::Ptr assign = source->assign();
if (!assign) continue; // widen node
expand_cerr << "Assigning input " << edge->data().format()
<< " from assignment " << assign->format() << endl;
inputMap[&edge->data()].insert(assign);
}
expand_cerr << "\t Input map has size " << inputMap.size() << endl;
// All of the expanded inputs are in the parameter dbase
// If not (like this one), add it
AST::Ptr ast;
boost::tie(ast, failedTranslation) = SymEval::expand(ptr->assign());
// expand_cerr << "\t ... resulting in " << dbase.format() << endl;
// We have an AST. Now substitute in all of its predecessors.
for (std::map<const AbsRegion*, std::set<Assignment::Ptr> >::iterator iter = inputMap.begin();
iter != inputMap.end(); ++iter) {
// If we have multiple secondary definitions, we:
// if all definitions are equal, use the first
// otherwise, use nothing
AST::Ptr definition;
for (std::set<Assignment::Ptr>::iterator iter2 = iter->second.begin();
iter2 != iter->second.end(); ++iter2) {
AST::Ptr newDef = dbase[*iter2];
if (!definition) {
definition = newDef;
continue;
} else if (definition->equals(newDef)) {
continue;
} else {
// Not equal
definition = AST::Ptr();
skippedInput = true;
break;
}
}
// The region used by the current assignment...
const AbsRegion ® = *iter->first;
// Create an AST around this one
VariableAST::Ptr use = VariableAST::create(Variable(reg, ptr->addr()));
if (!definition) {
// Can happen if we're expanding out of order, and is generally harmless.
continue;
}
expand_cerr << "Before substitution: " << (ast ? ast->format() : "<NULL AST>") << endl;
if (!ast) {
expand_cerr << "Skipping substitution because of null AST" << endl;
} else {
ast = AST::substitute(ast, use, definition);
success = true;
}
expand_cerr << "\t result is " << (ast ? ast->format() : "<NULL AST>") << endl;
}
expand_cerr << "Result of substitution: " << ptr->assign()->format() << " == "
<< (ast ? ast->format() : "<NULL AST>") << endl;
// And attempt simplification again
ast = simplifyStack(ast, ptr->addr(), ptr->func(), ptr->block());
expand_cerr << "Result of post-substitution simplification: " << ptr->assign()->format() << " == "
<< (ast ? ast->format() : "<NULL AST>") << endl;
dbase[ptr->assign()] = ast;
if (failedTranslation) return FAILED_TRANSLATION;
else if (skippedEdge || skippedInput) return SKIPPED_INPUT;
else if (success) return SUCCESS;
else return FAILED;
}
