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| 1 | +//=== AssumeModeling.cpp --------------------------------------------------===// |
| 2 | +// |
| 3 | +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | +// See https://llvm.org/LICENSE.txt for license information. |
| 5 | +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | +// |
| 7 | +//===----------------------------------------------------------------------===// |
| 8 | +// |
| 9 | +// This checker evaluates the builting assume functions. |
| 10 | +// This checker also sinks execution paths leaving [[assume]] attributes with |
| 11 | +// false assumptions. |
| 12 | +// |
| 13 | +//===----------------------------------------------------------------------===// |
| 14 | + |
| 15 | +#include "clang/AST/AttrIterator.h" |
| 16 | +#include "clang/Basic/Builtins.h" |
| 17 | +#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| 18 | +#include "clang/StaticAnalyzer/Core/Checker.h" |
| 19 | +#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" |
| 20 | +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| 21 | +#include "llvm/ADT/STLExtras.h" |
| 22 | + |
| 23 | +using namespace clang; |
| 24 | +using namespace ento; |
| 25 | + |
| 26 | +namespace { |
| 27 | +class AssumeModelingChecker |
| 28 | + : public Checker<eval::Call, check::PostStmt<AttributedStmt>> { |
| 29 | +public: |
| 30 | + void checkPostStmt(const AttributedStmt *A, CheckerContext &C) const; |
| 31 | + bool evalCall(const CallEvent &Call, CheckerContext &C) const; |
| 32 | +}; |
| 33 | +} // namespace |
| 34 | + |
| 35 | +void AssumeModelingChecker::checkPostStmt(const AttributedStmt *A, |
| 36 | + CheckerContext &C) const { |
| 37 | + if (!hasSpecificAttr<CXXAssumeAttr>(A->getAttrs())) |
| 38 | + return; |
| 39 | + |
| 40 | + for (const auto *Attr : getSpecificAttrs<CXXAssumeAttr>(A->getAttrs())) { |
| 41 | + SVal AssumptionVal = C.getSVal(Attr->getAssumption()); |
| 42 | + |
| 43 | + // The assumption is not evaluated at all if it had sideffects; skip them. |
| 44 | + if (AssumptionVal.isUnknown()) |
| 45 | + continue; |
| 46 | + |
| 47 | + const auto *Assumption = AssumptionVal.getAsInteger(); |
| 48 | + assert(Assumption && "We should know the exact outcome of an assume expr"); |
| 49 | + if (Assumption && Assumption->isZero()) { |
| 50 | + C.addSink(); |
| 51 | + } |
| 52 | + } |
| 53 | +} |
| 54 | + |
| 55 | +bool AssumeModelingChecker::evalCall(const CallEvent &Call, |
| 56 | + CheckerContext &C) const { |
| 57 | + ProgramStateRef State = C.getState(); |
| 58 | + const auto *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl()); |
| 59 | + if (!FD) |
| 60 | + return false; |
| 61 | + |
| 62 | + if (!llvm::is_contained({Builtin::BI__builtin_assume, Builtin::BI__assume}, |
| 63 | + FD->getBuiltinID())) { |
| 64 | + return false; |
| 65 | + } |
| 66 | + |
| 67 | + assert(Call.getNumArgs() > 0); |
| 68 | + SVal Arg = Call.getArgSVal(0); |
| 69 | + if (Arg.isUndef()) |
| 70 | + return true; // Return true to model purity. |
| 71 | + |
| 72 | + State = State->assume(Arg.castAs<DefinedOrUnknownSVal>(), true); |
| 73 | + if (!State) { |
| 74 | + C.addSink(); |
| 75 | + return true; |
| 76 | + } |
| 77 | + |
| 78 | + C.addTransition(State); |
| 79 | + return true; |
| 80 | +} |
| 81 | + |
| 82 | +void ento::registerAssumeModeling(CheckerManager &Mgr) { |
| 83 | + Mgr. registerChecker<AssumeModelingChecker>(); |
| 84 | +} |
| 85 | + |
| 86 | +bool ento::shouldRegisterAssumeModeling(const CheckerManager &) { return true; } |
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