Example #1
0
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;
    }


}
Example #2
0
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);
}
Example #3
0
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();

}
Example #4
0
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;
}
Example #5
0
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 &reg = *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;
}