void BoundFactsCalculator::ThunkBound( BoundFact*& curFact, Node::Ptr src, Node::Ptr trg, bool &newCopy) {
// This function checks whether any found thunk is between
// the src node and the trg node. If there is any, then we have
// extra bound information to be added.
ParseAPI::Block *srcBlock;
Address srcAddr = 0;
if (src == Node::Ptr())
srcBlock = func->entry();
else {
SliceNode::Ptr srcNode = boost::static_pointer_cast<SliceNode>(src);
srcBlock = srcNode->block();
srcAddr = srcNode->addr();
}
SliceNode::Ptr trgNode = boost::static_pointer_cast<SliceNode>(trg);
ParseAPI::Block *trgBlock = trgNode->block();
Address trgAddr = trgNode->addr();
bool first = true;
for (auto tit = thunks.begin(); tit != thunks.end(); ++tit) {
ParseAPI::Block* thunkBlock = tit->second.block;
parsing_printf("\t\tCheck srcAddr at %lx, trgAddr at %lx, thunk at %lx\n", srcAddr, trgAddr, tit->first);
if (src != Node::Ptr()) {
if (srcBlock == thunkBlock) {
if (srcAddr > tit->first) continue;
} else {
if (rf.thunk_ins[thunkBlock].find(srcBlock) == rf.thunk_ins[thunkBlock].end()) continue;
}
}
if (trgBlock == thunkBlock) {
if (trgAddr < tit->first) continue;
} else {
if (rf.thunk_outs[thunkBlock].find(trgBlock) == rf.thunk_outs[thunkBlock].end()) continue;
}
parsing_printf("\t\t\tfind thunk at %lx between the source and the target. Add fact", tit->first);
BoundValue *bv = new BoundValue(tit->second.value);
bv->Print();
if (first && !newCopy) {
newCopy = true;
curFact = new BoundFact(*curFact);
}
curFact->GenFact(VariableAST::create(Variable(AbsRegion(Absloc(tit->second.reg)))), bv, false);
first = false;
}
}
void BoundFactsCalculator::DetermineAnalysisOrder() {
NodeIterator nbegin, nend;
slice->allNodes(nbegin, nend);
nodeColor.clear();
reverseOrder.clear();
analysisOrder.clear();
for (; nbegin != nend; ++nbegin)
if (nodeColor.find(*nbegin) == nodeColor.end()) {
NaturalDFS(*nbegin);
}
nodeColor.clear();
orderStamp = 0;
for (auto nit = reverseOrder.rbegin(); nit != reverseOrder.rend(); ++nit)
if (nodeColor.find(*nit) == nodeColor.end()) {
++orderStamp;
ReverseDFS(*nit);
}
// Create a virtual entry node that has
// edges into all entry SCCs
SliceNode::Ptr virtualEntry = SliceNode::create(Assignment::Ptr(), func->entry(), func);
analysisOrder[virtualEntry] = 0;
for (int curOrder = 1; curOrder <= orderStamp; ++curOrder) {
// First determine all nodes in this SCC
vector<Node::Ptr> curNodes;
NodeIterator nbegin, nend;
slice->allNodes(nbegin, nend);
for (; nbegin != nend; ++nbegin) {
if (analysisOrder[*nbegin] == curOrder) {
curNodes.push_back(*nbegin);
}
}
// If this SCC does not have any outside edge,
// it is an entry SCC and we need to connect
// the virtual entry to it
if (!HasIncomingEdgesFromLowerLevel(curOrder, curNodes)) {
if (curNodes.size() == 1) {
// If the SCC has only one node,
// we connect the virtual entry to this single node
SliceNode::Ptr node = boost::static_pointer_cast<SliceNode>(*(curNodes.begin()));
slice->insertPair(virtualEntry, node, TypedSliceEdge::create(virtualEntry, node, FALLTHROUGH));
} else {
// If there are more than one node in this SCC,
// we do a DFS to see which nodes in the SCC can be
// reached from the entry of the function without passing
// through other nodes in the SCC.
// Basically, we only connect edges from the virtual entry
// to the entries of the SCC
set<ParseAPI::Block*> visit;
map<ParseAPI::Block*, vector<SliceNode::Ptr> >targetMap;
for (auto nit = curNodes.begin(); nit != curNodes.end(); ++nit) {
SliceNode::Ptr node = boost::static_pointer_cast<SliceNode>(*nit);
ParseAPI::Block * b = node->block();
Address addr = node->addr();
if (targetMap.find(b) == targetMap.end()) {
targetMap[b].push_back(node);
} else if (targetMap[b][0]->addr() > addr) {
targetMap[b].clear();
targetMap[b].push_back(node);
} else if (targetMap[b][0]->addr() == addr) {
targetMap[b].push_back(node);
}
}
BuildEdgeFromVirtualEntry(virtualEntry, virtualEntry->block(), targetMap, visit, slice);
}
}
}
slice->clearEntryNodes();
slice->markAsEntryNode(virtualEntry);
}
void BoundFactsCalculator::CalcTransferFunction(Node::Ptr curNode, BoundFact *newFact){
SliceNode::Ptr node = boost::static_pointer_cast<SliceNode>(curNode);
if (!node->assign()) return;
if (node->assign() && node->assign()->out().absloc().type() == Absloc::Register &&
(node->assign()->out().absloc().reg() == x86::zf || node->assign()->out().absloc().reg() == x86_64::zf)) {
// zf should be only predecessor of this node
parsing_printf("\t\tThe predecessor node is zf assignment!\n");
newFact->SetPredicate(node->assign(), ExpandAssignment(node->assign()) );
return;
}
entryID id = node->assign()->insn()->getOperation().getID();
// The predecessor is not a conditional jump,
// then we can determine buond fact based on the src assignment
parsing_printf("\t\tThe predecessor node is normal node\n");
parsing_printf("\t\t\tentry id %d\n", id);
AbsRegion &ar = node->assign()->out();
Instruction::Ptr insn = node->assign()->insn();
pair<AST::Ptr, bool> expandRet = ExpandAssignment(node->assign());
if (expandRet.first == NULL) {
parsing_printf("\t\t\t No semantic support for this instruction. Assume it does not affect jump target calculation. Ignore it (Treat as identity function) except for ptest. ptest should kill the current predicate\n");
if (id == e_ptest) {
parsing_printf("\t\t\t\tptest instruction, kill predciate.\n");
newFact->pred.valid = false;
}
return;
} else {
parsing_printf("\tAST: %s\n", expandRet.first->format().c_str());
}
AST::Ptr calculation = expandRet.first;
BoundCalcVisitor bcv(*newFact, node->block(), handleOneByteRead);
calculation->accept(&bcv);
AST::Ptr outAST;
// If the instruction writes memory,
// we need the AST that represents the memory access and the address.
// When the AbsRegion represents memory,
// the generator of the AbsRegion is set to be the AST that represents
// the memory address during symbolic expansion.
// In other cases, if the AbsRegion represents a register,
// the generator is not set.
if (ar.generator() != NULL)
outAST = SimplifyAnAST(RoseAST::create(ROSEOperation(ROSEOperation::derefOp, ar.size()), ar.generator()), node->assign()->insn()->size());
else
outAST = VariableAST::create(Variable(ar));
/*
* Naively, bsf and bsr produces a bound from 0 to the number of bits of the source operands.
* In pratice, especially in libc, the real bound is usually smaller than the size of the source operand.
* Ex 1: shl %cl,%edx
* bsf %rdx,%rcx
* Here rcx is in range [0,31] rather than [0,63] even though rdx has 64 bits.
*
* Ex 2: pmovmskb %xmm0,%edx
* bsf %rdx, %rdx
* Here rdx is in range[0,15] because pmovmskb only sets the least significat 16 bits
* In addition, overapproximation of the bound can lead to bogus control flow
* that causes overlapping blocks or function.
* It is important to further anaylze the operand in bsf rather than directly conclude the bound
if (id == e_bsf || id == e_bsr) {
int size = node->assign()->insn()->getOperand(0).getValue()->size();
newFact->GenFact(outAST, new BoundValue(StridedInterval(1,0, size * 8 - 1)), false);
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
return;
}
*/
if (id == e_xchg) {
newFact->SwapFact(calculation, outAST);
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
return;
}
if (id == e_push) {
if (calculation->getID() == AST::V_ConstantAST) {
ConstantAST::Ptr c = boost::static_pointer_cast<ConstantAST>(calculation);
newFact->PushAConst(c->val().val);
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
return;
}
}
if (id == e_pop) {
if (newFact->PopAConst(outAST)) {
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
return;
}
}
// Assume all SETxx entry ids are contiguous
if (id >= e_setb && id <= e_setz) {
newFact->GenFact(outAST, new BoundValue(StridedInterval(1,0,1)), false);
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
return;
}
if (bcv.IsResultBounded(calculation)) {
parsing_printf("\t\t\tGenerate bound fact for %s\n", outAST->format().c_str());
newFact->GenFact(outAST, new BoundValue(*bcv.GetResultBound(calculation)), false);
}
else {
parsing_printf("\t\t\tKill bound fact for %s\n", outAST->format().c_str());
newFact->KillFact(outAST, false);
}
if (calculation->getID() == AST::V_VariableAST) {
// We only track alising between registers
parsing_printf("\t\t\t%s and %s are equal\n", calculation->format().c_str(), outAST->format().c_str());
newFact->InsertRelation(calculation, outAST, BoundFact::Equal);
}
newFact->AdjustPredicate(outAST, calculation);
// Now try to track all aliasing.
// Currently, all variables in the slice are presented as an AST
// consists of input variables to the slice (the variables that
// we do not the sources of their values).
newFact->TrackAlias(DeepCopyAnAST(calculation), outAST);
// Apply tracking relations to the calculation to generate a
// potentially stricter bound
BoundValue *strictValue = newFact->ApplyRelations(outAST);
if (strictValue != NULL) {
parsing_printf("\t\t\tGenerate stricter bound fact for %s\n", outAST->format().c_str());
newFact->GenFact(outAST, strictValue, false);
}
parsing_printf("\t\t\tCalculating transfer function: Output facts\n");
newFact->Print();
}
bool BoundFactsCalculator::CalculateBoundedFacts() {
/* We use a dataflow analysis to calculate the value bound
* of each register and potentially some memory locations.
* The key steps of the dataflow analysis are
* 1. Determine the analysis order:
* First calculate all strongly connected components (SCC)
* of the graph. The flow analysis inside a SCC is
* iterative. The flow analysis between several SCCs
* is done topologically.
* 2. For each node, need to calculate the meet and
* calculate the transfer function.
* 1. The meet should be simply an intersection of all the bounded facts
* along all paths.
* 2. To calculate the transfer function, we first get the symbolic expression
* of the instrution for the node. Then depending on the instruction operation
* and the meet result, we know what are still bounded. For example, loading
* memory is always unbounded; doing and operation on a register with a constant
* makes the register bounded.
*/
DetermineAnalysisOrder();
queue<Node::Ptr> workingList;
unordered_set<Node::Ptr, Node::NodePtrHasher> inQueue;
unordered_map<Node::Ptr, int, Node::NodePtrHasher> inQueueLimit;
for (int curOrder = 0; curOrder <= orderStamp; ++curOrder) {
// We first determine which nodes are
// in this SCC
vector<Node::Ptr> curNodes;
NodeIterator nbegin, nend;
slice->allNodes(nbegin, nend);
for (; nbegin != nend; ++nbegin) {
if (analysisOrder[*nbegin] == curOrder) {
curNodes.push_back(*nbegin);
workingList.push(*nbegin);
inQueue.insert(*nbegin);
}
}
if (!HasIncomingEdgesFromLowerLevel(curOrder, curNodes)) {
// If this SCC is an entry SCC,
// we choose a node inside the SCC
// and let it be top.
// This should only contain the virtual entry node
parsing_printf("This SCC does not incoming edges from outside\n");
boundFactsIn[curNodes[0]] = new BoundFact();
boundFactsOut[curNodes[0]] = new BoundFact();
}
parsing_printf("Starting analysis inside SCC %d\n", curOrder);
// We now start iterative analysis inside the SCC
while (!workingList.empty()) {
// We get the current node
Node::Ptr curNode = workingList.front();
workingList.pop();
inQueue.erase(curNode);
SliceNode::Ptr node = boost::static_pointer_cast<SliceNode>(curNode);
++inQueueLimit[curNode];
if (inQueueLimit[curNode] > IN_QUEUE_LIMIT) continue;
BoundFact* oldFactIn = GetBoundFactIn(curNode);
parsing_printf("Calculate Meet for %lx", node->addr());
if (node->assign()) {
parsing_printf(", insn: %s\n", node->assign()->insn()->format().c_str());
}
else {
if (node->block() == NULL)
parsing_printf(", the VirtualExit node\n");
else
parsing_printf(", the VirtualEntry node\n");
}
parsing_printf("\tOld fact for %lx:\n", node->addr());
if (oldFactIn == NULL) parsing_printf("\t\t do not exist\n"); else oldFactIn->Print();
// We find all predecessors of the current node
// and calculates the union of the analysis results
// from the predecessors
BoundFact* newFactIn = Meet(curNode);
parsing_printf("\tNew fact at %lx\n", node->addr());
if (newFactIn != NULL) newFactIn->Print(); else parsing_printf("\t\tNot calculated\n");
// If the current node has not been calcualted yet,
// or the new meet results are different from the
// old ones, we keep the new results
if (newFactIn != NULL && (oldFactIn == NULL || *oldFactIn != *newFactIn)) {
parsing_printf("\tFacts change!\n");
if (oldFactIn != NULL) delete oldFactIn;
boundFactsIn[curNode] = newFactIn;
BoundFact* newFactOut = new BoundFact(*newFactIn);
// The current node has a transfer function
// that changes the analysis results
CalcTransferFunction(curNode, newFactOut);
if (boundFactsOut.find(curNode) != boundFactsOut.end() && boundFactsOut[curNode] != NULL)
delete boundFactsOut[curNode];
boundFactsOut[curNode] = newFactOut;
curNode->outs(nbegin, nend);
for (; nbegin != nend; ++nbegin)
// We only add node inside current SCC into the working list
if (inQueue.find(*nbegin) == inQueue.end() && analysisOrder[*nbegin] == curOrder) {
workingList.push(*nbegin);
inQueue.insert(*nbegin);
}
} else {
if (newFactIn != NULL) delete newFactIn;
parsing_printf("\tFacts do not change!\n");
}
}
}
return true;
}
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;
}
