1 //===- ThreadSafety.h -------------------------------------------*- 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 // 10 // A intra-procedural analysis for thread safety (e.g. deadlocks and race 11 // conditions), based off of an annotation system. 12 // 13 // See http://clang.llvm.org/docs/LanguageExtensions.html#thread-safety-annotation-checking 14 // for more information. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #ifndef LLVM_CLANG_ANALYSIS_ANALYSES_THREADSAFETY_H 19 #define LLVM_CLANG_ANALYSIS_ANALYSES_THREADSAFETY_H 20 21 #include "clang/Basic/SourceLocation.h" 22 #include "llvm/ADT/StringRef.h" 23 24 namespace clang { 25 26 class AnalysisDeclContext; 27 class FunctionDecl; 28 class NamedDecl; 29 30 namespace threadSafety { 31 32 class BeforeSet; 33 34 /// This enum distinguishes between different kinds of operations that may 35 /// need to be protected by locks. We use this enum in error handling. 36 enum ProtectedOperationKind { 37 /// Dereferencing a variable (e.g. p in *p = 5;) 38 POK_VarDereference, 39 40 /// Reading or writing a variable (e.g. x in x = 5;) 41 POK_VarAccess, 42 43 /// Making a function call (e.g. fool()) 44 POK_FunctionCall, 45 46 /// Passing a guarded variable by reference. 47 POK_PassByRef, 48 49 /// Passing a pt-guarded variable by reference. 50 POK_PtPassByRef 51 }; 52 53 /// This enum distinguishes between different kinds of lock actions. For 54 /// example, it is an error to write a variable protected by shared version of a 55 /// mutex. 56 enum LockKind { 57 /// Shared/reader lock of a mutex. 58 LK_Shared, 59 60 /// Exclusive/writer lock of a mutex. 61 LK_Exclusive, 62 63 /// Can be either Shared or Exclusive. 64 LK_Generic 65 }; 66 67 /// This enum distinguishes between different ways to access (read or write) a 68 /// variable. 69 enum AccessKind { 70 /// Reading a variable. 71 AK_Read, 72 73 /// Writing a variable. 74 AK_Written 75 }; 76 77 /// This enum distinguishes between different situations where we warn due to 78 /// inconsistent locking. 79 /// \enum SK_LockedSomeLoopIterations -- a mutex is locked for some but not all 80 /// loop iterations. 81 /// \enum SK_LockedSomePredecessors -- a mutex is locked in some but not all 82 /// predecessors of a CFGBlock. 83 /// \enum SK_LockedAtEndOfFunction -- a mutex is still locked at the end of a 84 /// function. 85 enum LockErrorKind { 86 LEK_LockedSomeLoopIterations, 87 LEK_LockedSomePredecessors, 88 LEK_LockedAtEndOfFunction, 89 LEK_NotLockedAtEndOfFunction 90 }; 91 92 /// Handler class for thread safety warnings. 93 class ThreadSafetyHandler { 94 public: 95 using Name = StringRef; 96 97 ThreadSafetyHandler() = default; 98 virtual ~ThreadSafetyHandler(); 99 100 /// Warn about lock expressions which fail to resolve to lockable objects. 101 /// \param Kind -- the capability's name parameter (role, mutex, etc). 102 /// \param Loc -- the SourceLocation of the unresolved expression. 103 virtual void handleInvalidLockExp(StringRef Kind, SourceLocation Loc) {} 104 105 /// Warn about unlock function calls that do not have a prior matching lock 106 /// expression. 107 /// \param Kind -- the capability's name parameter (role, mutex, etc). 108 /// \param LockName -- A StringRef name for the lock expression, to be printed 109 /// in the error message. 110 /// \param Loc -- The SourceLocation of the Unlock 111 virtual void handleUnmatchedUnlock(StringRef Kind, Name LockName, 112 SourceLocation Loc) {} 113 114 /// Warn about an unlock function call that attempts to unlock a lock with 115 /// the incorrect lock kind. For instance, a shared lock being unlocked 116 /// exclusively, or vice versa. 117 /// \param LockName -- A StringRef name for the lock expression, to be printed 118 /// in the error message. 119 /// \param Kind -- the capability's name parameter (role, mutex, etc). 120 /// \param Expected -- the kind of lock expected. 121 /// \param Received -- the kind of lock received. 122 /// \param LocLocked -- The SourceLocation of the Lock. 123 /// \param LocUnlock -- The SourceLocation of the Unlock. 124 virtual void handleIncorrectUnlockKind(StringRef Kind, Name LockName, 125 LockKind Expected, LockKind Received, 126 SourceLocation LocLocked, 127 SourceLocation LocUnlock) {} 128 129 /// Warn about lock function calls for locks which are already held. 130 /// \param Kind -- the capability's name parameter (role, mutex, etc). 131 /// \param LockName -- A StringRef name for the lock expression, to be printed 132 /// in the error message. 133 /// \param LocLocked -- The location of the first lock expression. 134 /// \param LocDoubleLock -- The location of the second lock expression. 135 virtual void handleDoubleLock(StringRef Kind, Name LockName, 136 SourceLocation LocLocked, 137 SourceLocation LocDoubleLock) {} 138 139 /// Warn about situations where a mutex is sometimes held and sometimes not. 140 /// The three situations are: 141 /// 1. a mutex is locked on an "if" branch but not the "else" branch, 142 /// 2, or a mutex is only held at the start of some loop iterations, 143 /// 3. or when a mutex is locked but not unlocked inside a function. 144 /// \param Kind -- the capability's name parameter (role, mutex, etc). 145 /// \param LockName -- A StringRef name for the lock expression, to be printed 146 /// in the error message. 147 /// \param LocLocked -- The location of the lock expression where the mutex is 148 /// locked 149 /// \param LocEndOfScope -- The location of the end of the scope where the 150 /// mutex is no longer held 151 /// \param LEK -- which of the three above cases we should warn for 152 virtual void handleMutexHeldEndOfScope(StringRef Kind, Name LockName, 153 SourceLocation LocLocked, 154 SourceLocation LocEndOfScope, 155 LockErrorKind LEK) {} 156 157 /// Warn when a mutex is held exclusively and shared at the same point. For 158 /// example, if a mutex is locked exclusively during an if branch and shared 159 /// during the else branch. 160 /// \param Kind -- the capability's name parameter (role, mutex, etc). 161 /// \param LockName -- A StringRef name for the lock expression, to be printed 162 /// in the error message. 163 /// \param Loc1 -- The location of the first lock expression. 164 /// \param Loc2 -- The location of the second lock expression. 165 virtual void handleExclusiveAndShared(StringRef Kind, Name LockName, 166 SourceLocation Loc1, 167 SourceLocation Loc2) {} 168 169 /// Warn when a protected operation occurs while no locks are held. 170 /// \param Kind -- the capability's name parameter (role, mutex, etc). 171 /// \param D -- The decl for the protected variable or function 172 /// \param POK -- The kind of protected operation (e.g. variable access) 173 /// \param AK -- The kind of access (i.e. read or write) that occurred 174 /// \param Loc -- The location of the protected operation. 175 virtual void handleNoMutexHeld(StringRef Kind, const NamedDecl *D, 176 ProtectedOperationKind POK, AccessKind AK, 177 SourceLocation Loc) {} 178 179 /// Warn when a protected operation occurs while the specific mutex protecting 180 /// the operation is not locked. 181 /// \param Kind -- the capability's name parameter (role, mutex, etc). 182 /// \param D -- The decl for the protected variable or function 183 /// \param POK -- The kind of protected operation (e.g. variable access) 184 /// \param LockName -- A StringRef name for the lock expression, to be printed 185 /// in the error message. 186 /// \param LK -- The kind of access (i.e. read or write) that occurred 187 /// \param Loc -- The location of the protected operation. 188 virtual void handleMutexNotHeld(StringRef Kind, const NamedDecl *D, 189 ProtectedOperationKind POK, Name LockName, 190 LockKind LK, SourceLocation Loc, 191 Name *PossibleMatch = nullptr) {} 192 193 /// Warn when acquiring a lock that the negative capability is not held. 194 /// \param Kind -- the capability's name parameter (role, mutex, etc). 195 /// \param LockName -- The name for the lock expression, to be printed in the 196 /// diagnostic. 197 /// \param Neg -- The name of the negative capability to be printed in the 198 /// diagnostic. 199 /// \param Loc -- The location of the protected operation. 200 virtual void handleNegativeNotHeld(StringRef Kind, Name LockName, Name Neg, 201 SourceLocation Loc) {} 202 203 /// Warn when a function is called while an excluded mutex is locked. For 204 /// example, the mutex may be locked inside the function. 205 /// \param Kind -- the capability's name parameter (role, mutex, etc). 206 /// \param FunName -- The name of the function 207 /// \param LockName -- A StringRef name for the lock expression, to be printed 208 /// in the error message. 209 /// \param Loc -- The location of the function call. 210 virtual void handleFunExcludesLock(StringRef Kind, Name FunName, 211 Name LockName, SourceLocation Loc) {} 212 213 /// Warn that L1 cannot be acquired before L2. 214 virtual void handleLockAcquiredBefore(StringRef Kind, Name L1Name, 215 Name L2Name, SourceLocation Loc) {} 216 217 /// Warn that there is a cycle in acquired_before/after dependencies. 218 virtual void handleBeforeAfterCycle(Name L1Name, SourceLocation Loc) {} 219 220 /// Called by the analysis when starting analysis of a function. 221 /// Used to issue suggestions for changes to annotations. 222 virtual void enterFunction(const FunctionDecl *FD) {} 223 224 /// Called by the analysis when finishing analysis of a function. 225 virtual void leaveFunction(const FunctionDecl *FD) {} 226 227 bool issueBetaWarnings() { return IssueBetaWarnings; } 228 void setIssueBetaWarnings(bool b) { IssueBetaWarnings = b; } 229 230 private: 231 bool IssueBetaWarnings = false; 232 }; 233 234 /// Check a function's CFG for thread-safety violations. 235 /// 236 /// We traverse the blocks in the CFG, compute the set of mutexes that are held 237 /// at the end of each block, and issue warnings for thread safety violations. 238 /// Each block in the CFG is traversed exactly once. 239 void runThreadSafetyAnalysis(AnalysisDeclContext &AC, 240 ThreadSafetyHandler &Handler, 241 BeforeSet **Bset); 242 243 void threadSafetyCleanup(BeforeSet *Cache); 244 245 /// Helper function that returns a LockKind required for the given level 246 /// of access. 247 LockKind getLockKindFromAccessKind(AccessKind AK); 248 249 } // namespace threadSafety 250 } // namespace clang 251 252 #endif // LLVM_CLANG_ANALYSIS_ANALYSES_THREADSAFETY_H 253