forked from OSchip/llvm-project
140 lines
4.8 KiB
C++
140 lines
4.8 KiB
C++
//=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This checker evaluates clang builtin functions.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Basic/Builtins.h"
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class BuiltinFunctionChecker : public Checker<eval::Call> {
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public:
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bool evalCall(const CallEvent &Call, CheckerContext &C) const;
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};
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}
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bool BuiltinFunctionChecker::evalCall(const CallEvent &Call,
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CheckerContext &C) const {
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ProgramStateRef state = C.getState();
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const auto *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
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if (!FD)
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return false;
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const LocationContext *LCtx = C.getLocationContext();
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const Expr *CE = Call.getOriginExpr();
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switch (FD->getBuiltinID()) {
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default:
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return false;
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case Builtin::BI__builtin_assume: {
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assert (Call.getNumArgs() > 0);
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SVal Arg = Call.getArgSVal(0);
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if (Arg.isUndef())
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return true; // Return true to model purity.
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state = state->assume(Arg.castAs<DefinedOrUnknownSVal>(), true);
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// FIXME: do we want to warn here? Not right now. The most reports might
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// come from infeasible paths, thus being false positives.
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if (!state) {
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C.generateSink(C.getState(), C.getPredecessor());
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return true;
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}
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C.addTransition(state);
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return true;
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}
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case Builtin::BI__builtin_unpredictable:
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case Builtin::BI__builtin_expect:
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case Builtin::BI__builtin_expect_with_probability:
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case Builtin::BI__builtin_assume_aligned:
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case Builtin::BI__builtin_addressof:
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case Builtin::BI__builtin_function_start: {
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// For __builtin_unpredictable, __builtin_expect,
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// __builtin_expect_with_probability and __builtin_assume_aligned,
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// just return the value of the subexpression.
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// __builtin_addressof is going from a reference to a pointer, but those
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// are represented the same way in the analyzer.
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assert (Call.getNumArgs() > 0);
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SVal Arg = Call.getArgSVal(0);
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C.addTransition(state->BindExpr(CE, LCtx, Arg));
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return true;
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}
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case Builtin::BI__builtin_alloca_with_align:
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case Builtin::BI__builtin_alloca: {
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// FIXME: Refactor into StoreManager itself?
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MemRegionManager& RM = C.getStoreManager().getRegionManager();
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const AllocaRegion* R =
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RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
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// Set the extent of the region in bytes. This enables us to use the
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// SVal of the argument directly. If we save the extent in bits, we
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// cannot represent values like symbol*8.
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auto Size = Call.getArgSVal(0);
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if (Size.isUndef())
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return true; // Return true to model purity.
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state = setDynamicExtent(state, R, Size.castAs<DefinedOrUnknownSVal>(),
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C.getSValBuilder());
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C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
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return true;
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}
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case Builtin::BI__builtin_dynamic_object_size:
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case Builtin::BI__builtin_object_size:
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case Builtin::BI__builtin_constant_p: {
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// This must be resolvable at compile time, so we defer to the constant
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// evaluator for a value.
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SValBuilder &SVB = C.getSValBuilder();
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SVal V = UnknownVal();
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Expr::EvalResult EVResult;
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if (CE->EvaluateAsInt(EVResult, C.getASTContext(), Expr::SE_NoSideEffects)) {
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// Make sure the result has the correct type.
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llvm::APSInt Result = EVResult.Val.getInt();
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BasicValueFactory &BVF = SVB.getBasicValueFactory();
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BVF.getAPSIntType(CE->getType()).apply(Result);
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V = SVB.makeIntVal(Result);
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}
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if (FD->getBuiltinID() == Builtin::BI__builtin_constant_p) {
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// If we didn't manage to figure out if the value is constant or not,
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// it is safe to assume that it's not constant and unsafe to assume
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// that it's constant.
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if (V.isUnknown())
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V = SVB.makeIntVal(0, CE->getType());
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}
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C.addTransition(state->BindExpr(CE, LCtx, V));
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return true;
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}
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}
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}
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void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
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mgr.registerChecker<BuiltinFunctionChecker>();
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}
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bool ento::shouldRegisterBuiltinFunctionChecker(const CheckerManager &mgr) {
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return true;
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}
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