clang 18.0.0git
BlockInCriticalSectionChecker.cpp
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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
23
24using namespace clang;
25using namespace ento;
26
27namespace {
28
29class 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
49public:
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
64REGISTER_TRAIT_WITH_PROGRAMSTATE(MutexCounter, unsigned)
65
66BlockInCriticalSectionChecker::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
82void 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
95bool BlockInCriticalSectionChecker::isBlockingFunction(const CallEvent &Call) const {
96 return matchesAny(Call, SleepFn, GetcFn, FgetsFn, ReadFn, RecvFn);
97}
98
99bool 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
110bool 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
121void 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
144void 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
161void ento::registerBlockInCriticalSectionChecker(CheckerManager &mgr) {
162 mgr.registerChecker<BlockInCriticalSectionChecker>();
163}
164
165bool ento::shouldRegisterBlockInCriticalSectionChecker(const CheckerManager &mgr) {
166 return true;
167}
#define REGISTER_TRAIT_WITH_PROGRAMSTATE(Name, Type)
Declares a program state trait for type Type called Name, and introduce a type named NameTy.
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:182
IdentifierTable & Idents
Definition: ASTContext.h:636
One of these records is kept for each identifier that is lexed.
IdentifierInfo & get(StringRef Name)
Return the identifier token info for the specified named identifier.
This class represents a description of a function call using the number of arguments and the name of ...
Represents an abstract call to a function or method along a particular path.
Definition: CallEvent.h:152
CHECKER * registerChecker(AT &&... Args)
Used to register checkers.
Symbolic value.
Definition: SymExpr.h:30