1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
//===--- PthreadLockChecker.cpp - Check for locking problems ---*- C++ -*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines PthreadLockChecker, a simple lock -> unlock checker.
// Also handles XNU locks, which behave similarly enough to share code.
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "llvm/ADT/ImmutableList.h"
using namespace clang;
using namespace ento;
namespace {
class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
mutable OwningPtr<BugType> BT_doublelock;
mutable OwningPtr<BugType> BT_lor;
enum LockingSemantics {
NotApplicable = 0,
PthreadSemantics,
XNUSemantics
};
public:
void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
void AcquireLock(CheckerContext &C, const CallExpr *CE, SVal lock,
bool isTryLock, enum LockingSemantics semantics) const;
void ReleaseLock(CheckerContext &C, const CallExpr *CE, SVal lock) const;
};
} // end anonymous namespace
// GDM Entry for tracking lock state.
namespace { class LockSet {}; }
namespace clang {
namespace ento {
template <> struct ProgramStateTrait<LockSet> :
public ProgramStatePartialTrait<llvm::ImmutableList<const MemRegion*> > {
static void *GDMIndex() { static int x = 0; return &x; }
};
} // end of ento (ProgramState) namespace
} // end clang namespace
void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();
StringRef FName = C.getCalleeName(CE);
if (FName.empty())
return;
if (CE->getNumArgs() != 1)
return;
if (FName == "pthread_mutex_lock" ||
FName == "pthread_rwlock_rdlock" ||
FName == "pthread_rwlock_wrlock")
AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
false, PthreadSemantics);
else if (FName == "lck_mtx_lock" ||
FName == "lck_rw_lock_exclusive" ||
FName == "lck_rw_lock_shared")
AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
false, XNUSemantics);
else if (FName == "pthread_mutex_trylock" ||
FName == "pthread_rwlock_tryrdlock" ||
FName == "pthread_rwlock_tryrwlock")
AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
true, PthreadSemantics);
else if (FName == "lck_mtx_try_lock" ||
FName == "lck_rw_try_lock_exclusive" ||
FName == "lck_rw_try_lock_shared")
AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
true, XNUSemantics);
else if (FName == "pthread_mutex_unlock" ||
FName == "pthread_rwlock_unlock" ||
FName == "lck_mtx_unlock" ||
FName == "lck_rw_done")
ReleaseLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
}
void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
SVal lock, bool isTryLock,
enum LockingSemantics semantics) const {
const MemRegion *lockR = lock.getAsRegion();
if (!lockR)
return;
ProgramStateRef state = C.getState();
SVal X = state->getSVal(CE, C.getLocationContext());
if (X.isUnknownOrUndef())
return;
DefinedSVal retVal = cast<DefinedSVal>(X);
if (state->contains<LockSet>(lockR)) {
if (!BT_doublelock)
BT_doublelock.reset(new BugType("Double locking", "Lock checker"));
ExplodedNode *N = C.generateSink();
if (!N)
return;
BugReport *report = new BugReport(*BT_doublelock,
"This lock has already "
"been acquired", N);
report->addRange(CE->getArg(0)->getSourceRange());
C.EmitReport(report);
return;
}
ProgramStateRef lockSucc = state;
if (isTryLock) {
// Bifurcate the state, and allow a mode where the lock acquisition fails.
ProgramStateRef lockFail;
switch (semantics) {
case PthreadSemantics:
llvm::tie(lockFail, lockSucc) = state->assume(retVal);
break;
case XNUSemantics:
llvm::tie(lockSucc, lockFail) = state->assume(retVal);
break;
default:
llvm_unreachable("Unknown tryLock locking semantics");
}
assert(lockFail && lockSucc);
C.addTransition(lockFail);
} else if (semantics == PthreadSemantics) {
// Assume that the return value was 0.
lockSucc = state->assume(retVal, false);
assert(lockSucc);
} else {
// XNU locking semantics return void on non-try locks
assert((semantics == XNUSemantics) && "Unknown locking semantics");
lockSucc = state;
}
// Record that the lock was acquired.
lockSucc = lockSucc->add<LockSet>(lockR);
C.addTransition(lockSucc);
}
void PthreadLockChecker::ReleaseLock(CheckerContext &C, const CallExpr *CE,
SVal lock) const {
const MemRegion *lockR = lock.getAsRegion();
if (!lockR)
return;
ProgramStateRef state = C.getState();
llvm::ImmutableList<const MemRegion*> LS = state->get<LockSet>();
// FIXME: Better analysis requires IPA for wrappers.
// FIXME: check for double unlocks
if (LS.isEmpty())
return;
const MemRegion *firstLockR = LS.getHead();
if (firstLockR != lockR) {
if (!BT_lor)
BT_lor.reset(new BugType("Lock order reversal", "Lock checker"));
ExplodedNode *N = C.generateSink();
if (!N)
return;
BugReport *report = new BugReport(*BT_lor,
"This was not the most "
"recently acquired lock. "
"Possible lock order "
"reversal", N);
report->addRange(CE->getArg(0)->getSourceRange());
C.EmitReport(report);
return;
}
// Record that the lock was released.
state = state->set<LockSet>(LS.getTail());
C.addTransition(state);
}
void ento::registerPthreadLockChecker(CheckerManager &mgr) {
mgr.registerChecker<PthreadLockChecker>();
}
|
