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 /// \param LocPreviousUnlock -- If valid, the location of a previous Unlock. 112 virtual void handleUnmatchedUnlock(StringRef Kind, Name LockName, 113 SourceLocation Loc, 114 SourceLocation LocPreviousUnlock) {} 115 116 /// Warn about an unlock function call that attempts to unlock a lock with 117 /// the incorrect lock kind. For instance, a shared lock being unlocked 118 /// exclusively, or vice versa. 119 /// \param LockName -- A StringRef name for the lock expression, to be printed 120 /// in the error message. 121 /// \param Kind -- the capability's name parameter (role, mutex, etc). 122 /// \param Expected -- the kind of lock expected. 123 /// \param Received -- the kind of lock received. 124 /// \param LocLocked -- The SourceLocation of the Lock. 125 /// \param LocUnlock -- The SourceLocation of the Unlock. 126 virtual void handleIncorrectUnlockKind(StringRef Kind, Name LockName, 127 LockKind Expected, LockKind Received, 128 SourceLocation LocLocked, 129 SourceLocation LocUnlock) {} 130 131 /// Warn about lock function calls for locks which are already held. 132 /// \param Kind -- the capability's name parameter (role, mutex, etc). 133 /// \param LockName -- A StringRef name for the lock expression, to be printed 134 /// in the error message. 135 /// \param LocLocked -- The location of the first lock expression. 136 /// \param LocDoubleLock -- The location of the second lock expression. 137 virtual void handleDoubleLock(StringRef Kind, Name LockName, 138 SourceLocation LocLocked, 139 SourceLocation LocDoubleLock) {} 140 141 /// Warn about situations where a mutex is sometimes held and sometimes not. 142 /// The three situations are: 143 /// 1. a mutex is locked on an "if" branch but not the "else" branch, 144 /// 2, or a mutex is only held at the start of some loop iterations, 145 /// 3. or when a mutex is locked but not unlocked inside a function. 146 /// \param Kind -- the capability's name parameter (role, mutex, etc). 147 /// \param LockName -- A StringRef name for the lock expression, to be printed 148 /// in the error message. 149 /// \param LocLocked -- The location of the lock expression where the mutex is 150 /// locked 151 /// \param LocEndOfScope -- The location of the end of the scope where the 152 /// mutex is no longer held 153 /// \param LEK -- which of the three above cases we should warn for 154 virtual void handleMutexHeldEndOfScope(StringRef Kind, Name LockName, 155 SourceLocation LocLocked, 156 SourceLocation LocEndOfScope, 157 LockErrorKind LEK) {} 158 159 /// Warn when a mutex is held exclusively and shared at the same point. For 160 /// example, if a mutex is locked exclusively during an if branch and shared 161 /// during the else branch. 162 /// \param Kind -- the capability's name parameter (role, mutex, etc). 163 /// \param LockName -- A StringRef name for the lock expression, to be printed 164 /// in the error message. 165 /// \param Loc1 -- The location of the first lock expression. 166 /// \param Loc2 -- The location of the second lock expression. 167 virtual void handleExclusiveAndShared(StringRef Kind, Name LockName, 168 SourceLocation Loc1, 169 SourceLocation Loc2) {} 170 171 /// Warn when a protected operation occurs while no locks are held. 172 /// \param Kind -- the capability's name parameter (role, mutex, etc). 173 /// \param D -- The decl for the protected variable or function 174 /// \param POK -- The kind of protected operation (e.g. variable access) 175 /// \param AK -- The kind of access (i.e. read or write) that occurred 176 /// \param Loc -- The location of the protected operation. 177 virtual void handleNoMutexHeld(StringRef Kind, const NamedDecl *D, 178 ProtectedOperationKind POK, AccessKind AK, 179 SourceLocation Loc) {} 180 181 /// Warn when a protected operation occurs while the specific mutex protecting 182 /// the operation is not locked. 183 /// \param Kind -- the capability's name parameter (role, mutex, etc). 184 /// \param D -- The decl for the protected variable or function 185 /// \param POK -- The kind of protected operation (e.g. variable access) 186 /// \param LockName -- A StringRef name for the lock expression, to be printed 187 /// in the error message. 188 /// \param LK -- The kind of access (i.e. read or write) that occurred 189 /// \param Loc -- The location of the protected operation. 190 virtual void handleMutexNotHeld(StringRef Kind, const NamedDecl *D, 191 ProtectedOperationKind POK, Name LockName, 192 LockKind LK, SourceLocation Loc, 193 Name *PossibleMatch = nullptr) {} 194 195 /// Warn when acquiring a lock that the negative capability is not held. 196 /// \param Kind -- the capability's name parameter (role, mutex, etc). 197 /// \param LockName -- The name for the lock expression, to be printed in the 198 /// diagnostic. 199 /// \param Neg -- The name of the negative capability to be printed in the 200 /// diagnostic. 201 /// \param Loc -- The location of the protected operation. 202 virtual void handleNegativeNotHeld(StringRef Kind, Name LockName, Name Neg, 203 SourceLocation Loc) {} 204 205 /// Warn when a function is called while an excluded mutex is locked. For 206 /// example, the mutex may be locked inside the function. 207 /// \param Kind -- the capability's name parameter (role, mutex, etc). 208 /// \param FunName -- The name of the function 209 /// \param LockName -- A StringRef name for the lock expression, to be printed 210 /// in the error message. 211 /// \param Loc -- The location of the function call. 212 virtual void handleFunExcludesLock(StringRef Kind, Name FunName, 213 Name LockName, SourceLocation Loc) {} 214 215 /// Warn that L1 cannot be acquired before L2. 216 virtual void handleLockAcquiredBefore(StringRef Kind, Name L1Name, 217 Name L2Name, SourceLocation Loc) {} 218 219 /// Warn that there is a cycle in acquired_before/after dependencies. 220 virtual void handleBeforeAfterCycle(Name L1Name, SourceLocation Loc) {} 221 222 /// Called by the analysis when starting analysis of a function. 223 /// Used to issue suggestions for changes to annotations. 224 virtual void enterFunction(const FunctionDecl *FD) {} 225 226 /// Called by the analysis when finishing analysis of a function. 227 virtual void leaveFunction(const FunctionDecl *FD) {} 228 229 bool issueBetaWarnings() { return IssueBetaWarnings; } 230 void setIssueBetaWarnings(bool b) { IssueBetaWarnings = b; } 231 232 private: 233 bool IssueBetaWarnings = false; 234 }; 235 236 /// Check a function's CFG for thread-safety violations. 237 /// 238 /// We traverse the blocks in the CFG, compute the set of mutexes that are held 239 /// at the end of each block, and issue warnings for thread safety violations. 240 /// Each block in the CFG is traversed exactly once. 241 void runThreadSafetyAnalysis(AnalysisDeclContext &AC, 242 ThreadSafetyHandler &Handler, 243 BeforeSet **Bset); 244 245 void threadSafetyCleanup(BeforeSet *Cache); 246 247 /// Helper function that returns a LockKind required for the given level 248 /// of access. 249 LockKind getLockKindFromAccessKind(AccessKind AK); 250 251 } // namespace threadSafety 252 } // namespace clang 253 254 #endif // LLVM_CLANG_ANALYSIS_ANALYSES_THREADSAFETY_H 255