| 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>(Val: 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(Index: 0); |
| 69 | if (Arg.isUndef()) |
| 70 | return true; // Return true to model purity. |
| 71 | |
| 72 | State = State->assume(Cond: Arg.castAs<DefinedOrUnknownSVal>(), Assumption: 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; } |
| 87 |