clang/lib/StaticAnalyzer/Checkers/BlockInCriticalSectionChecker.cpp

   1 //===-- BlockInCriticalSectionChecker.cpp -----------------------*- C++ -*-===//
   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 // Defines a checker for blocks in critical sections. This checker should find
  10 // the calls to blocking functions (for example: sleep, getc, fgets, read,
  11 // recv etc.) inside a critical section. When sleep(x) is called while a mutex
  12 // is held, other threades cannot lock the same mutex. This might take some
  13 // time, leading to bad performance or even deadlock.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  19 #include "clang/StaticAnalyzer/Core/Checker.h"
  20 #include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
  21 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
  22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  23
  24 using namespace clang;
  25 using namespace ento;
  26
  27 namespace {
  28
  29 class BlockInCriticalSectionChecker : public Checker<check::PostCall> {
  30
  31   mutable IdentifierInfo *IILockGuard, *IIUniqueLock;
  32
  33   CallDescription LockFn, UnlockFn, SleepFn, GetcFn, FgetsFn, ReadFn, RecvFn,
  34                   PthreadLockFn, PthreadTryLockFn, PthreadUnlockFn,
  35                   MtxLock, MtxTimedLock, MtxTryLock, MtxUnlock;
  36
  37   StringRef ClassLockGuard, ClassUniqueLock;
  38
  39   mutable bool IdentifierInfoInitialized;
  40
  41   std::unique_ptr<BugType> BlockInCritSectionBugType;
  42
  43   void initIdentifierInfo(ASTContext &Ctx) const;
  44
  45   void reportBlockInCritSection(SymbolRef FileDescSym,
  46                                 const CallEvent &call,
  47                                 CheckerContext &C) const;
  48
  49 public:
  50   BlockInCriticalSectionChecker();
  51
  52   bool isBlockingFunction(const CallEvent &Call) const;
  53   bool isLockFunction(const CallEvent &Call) const;
  54   bool isUnlockFunction(const CallEvent &Call) const;
  55
  56   /// Process unlock.
  57   /// Process lock.
  58   /// Process blocking functions (sleep, getc, fgets, read, recv)
  59   void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
  60 };
  61
  62 } // end anonymous namespace
  63
  64 REGISTER_TRAIT_WITH_PROGRAMSTATE(MutexCounter, unsigned)
  65
  66 BlockInCriticalSectionChecker::BlockInCriticalSectionChecker()
  67     : IILockGuard(nullptr), IIUniqueLock(nullptr), LockFn({"lock"}),
  68       UnlockFn({"unlock"}), SleepFn({"sleep"}), GetcFn({"getc"}),
  69       FgetsFn({"fgets"}), ReadFn({"read"}), RecvFn({"recv"}),
  70       PthreadLockFn({"pthread_mutex_lock"}),
  71       PthreadTryLockFn({"pthread_mutex_trylock"}),
  72       PthreadUnlockFn({"pthread_mutex_unlock"}), MtxLock({"mtx_lock"}),
  73       MtxTimedLock({"mtx_timedlock"}), MtxTryLock({"mtx_trylock"}),
  74       MtxUnlock({"mtx_unlock"}), ClassLockGuard("lock_guard"),
  75       ClassUniqueLock("unique_lock"), IdentifierInfoInitialized(false) {
  76   // Initialize the bug type.
  77   BlockInCritSectionBugType.reset(
  78       new BugType(this, "Call to blocking function in critical section",
  79                         "Blocking Error"));
  80 }
  81
  82 void BlockInCriticalSectionChecker::initIdentifierInfo(ASTContext &Ctx) const {
  83   if (!IdentifierInfoInitialized) {
  84     /* In case of checking C code, or when the corresponding headers are not
  85      * included, we might end up query the identifier table every time when this
  86      * function is called instead of early returning it. To avoid this, a bool
  87      * variable (IdentifierInfoInitialized) is used and the function will be run
  88      * only once. */
  89     IILockGuard  = &Ctx.Idents.get(ClassLockGuard);
  90     IIUniqueLock = &Ctx.Idents.get(ClassUniqueLock);
  91     IdentifierInfoInitialized = true;
  92   }
  93 }
  94
  95 bool BlockInCriticalSectionChecker::isBlockingFunction(const CallEvent &Call) const {
  96   return matchesAny(Call, SleepFn, GetcFn, FgetsFn, ReadFn, RecvFn);
  97 }
  98
  99 bool BlockInCriticalSectionChecker::isLockFunction(const CallEvent &Call) const {
 100   if (const auto *Ctor = dyn_cast<CXXConstructorCall>(&Call)) {
 101     auto IdentifierInfo = Ctor->getDecl()->getParent()->getIdentifier();
 102     if (IdentifierInfo == IILockGuard || IdentifierInfo == IIUniqueLock)
 103       return true;
 104   }
 105
 106   return matchesAny(Call, LockFn, PthreadLockFn, PthreadTryLockFn, MtxLock,
 107                     MtxTimedLock, MtxTryLock);
 108 }
 109
 110 bool BlockInCriticalSectionChecker::isUnlockFunction(const CallEvent &Call) const {
 111   if (const auto *Dtor = dyn_cast<CXXDestructorCall>(&Call)) {
 112     const auto *DRecordDecl = cast<CXXRecordDecl>(Dtor->getDecl()->getParent());
 113     auto IdentifierInfo = DRecordDecl->getIdentifier();
 114     if (IdentifierInfo == IILockGuard || IdentifierInfo == IIUniqueLock)
 115       return true;
 116   }
 117
 118   return matchesAny(Call, UnlockFn, PthreadUnlockFn, MtxUnlock);
 119 }
 120
 121 void BlockInCriticalSectionChecker::checkPostCall(const CallEvent &Call,
 122                                                   CheckerContext &C) const {
 123   initIdentifierInfo(C.getASTContext());
 124
 125   if (!isBlockingFunction(Call)
 126       && !isLockFunction(Call)
 127       && !isUnlockFunction(Call))
 128     return;
 129
 130   ProgramStateRef State = C.getState();
 131   unsigned mutexCount = State->get<MutexCounter>();
 132   if (isUnlockFunction(Call) && mutexCount > 0) {
 133     State = State->set<MutexCounter>(--mutexCount);
 134     C.addTransition(State);
 135   } else if (isLockFunction(Call)) {
 136     State = State->set<MutexCounter>(++mutexCount);
 137     C.addTransition(State);
 138   } else if (mutexCount > 0) {
 139     SymbolRef BlockDesc = Call.getReturnValue().getAsSymbol();
 140     reportBlockInCritSection(BlockDesc, Call, C);
 141   }
 142 }
 143
 144 void BlockInCriticalSectionChecker::reportBlockInCritSection(
 145     SymbolRef BlockDescSym, const CallEvent &Call, CheckerContext &C) const {
 146   ExplodedNode *ErrNode = C.generateNonFatalErrorNode();
 147   if (!ErrNode)
 148     return;
 149
 150   std::string msg;
 151   llvm::raw_string_ostream os(msg);
 152   os << "Call to blocking function '" << Call.getCalleeIdentifier()->getName()
 153      << "' inside of critical section";
 154   auto R = std::make_unique<PathSensitiveBugReport>(*BlockInCritSectionBugType,
 155                                                     os.str(), ErrNode);
 156   R->addRange(Call.getSourceRange());
 157   R->markInteresting(BlockDescSym);
 158   C.emitReport(std::move(R));
 159 }
 160
 161 void ento::registerBlockInCriticalSectionChecker(CheckerManager &mgr) {
 162   mgr.registerChecker<BlockInCriticalSectionChecker>();
 163 }
 164
 165 bool ento::shouldRegisterBlockInCriticalSectionChecker(const CheckerManager &mgr) {
 166   return true;
 167 }