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comparison lib/Support/CrashRecoveryContext.cpp @ 0:95c75e76d11b

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children 54457678186b
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-1:000000000000 0:95c75e76d11b
1 //===--- CrashRecoveryContext.cpp - Crash Recovery ------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "llvm/Support/CrashRecoveryContext.h"
11 #include "llvm/ADT/SmallString.h"
12 #include "llvm/Config/config.h"
13 #include "llvm/Support/ErrorHandling.h"
14 #include "llvm/Support/ManagedStatic.h"
15 #include "llvm/Support/Mutex.h"
16 #include "llvm/Support/ThreadLocal.h"
17 #include <cstdio>
18 #include <setjmp.h>
19 using namespace llvm;
20
21 namespace {
22
23 struct CrashRecoveryContextImpl;
24
25 static ManagedStatic<sys::ThreadLocal<const CrashRecoveryContextImpl> > CurrentContext;
26
27 struct CrashRecoveryContextImpl {
28 CrashRecoveryContext *CRC;
29 std::string Backtrace;
30 ::jmp_buf JumpBuffer;
31 volatile unsigned Failed : 1;
32 unsigned SwitchedThread : 1;
33
34 public:
35 CrashRecoveryContextImpl(CrashRecoveryContext *CRC) : CRC(CRC),
36 Failed(false),
37 SwitchedThread(false) {
38 CurrentContext->set(this);
39 }
40 ~CrashRecoveryContextImpl() {
41 if (!SwitchedThread)
42 CurrentContext->erase();
43 }
44
45 /// \brief Called when the separate crash-recovery thread was finished, to
46 /// indicate that we don't need to clear the thread-local CurrentContext.
47 void setSwitchedThread() { SwitchedThread = true; }
48
49 void HandleCrash() {
50 // Eliminate the current context entry, to avoid re-entering in case the
51 // cleanup code crashes.
52 CurrentContext->erase();
53
54 assert(!Failed && "Crash recovery context already failed!");
55 Failed = true;
56
57 // FIXME: Stash the backtrace.
58
59 // Jump back to the RunSafely we were called under.
60 longjmp(JumpBuffer, 1);
61 }
62 };
63
64 }
65
66 static ManagedStatic<sys::Mutex> gCrashRecoveryContextMutex;
67 static bool gCrashRecoveryEnabled = false;
68
69 static ManagedStatic<sys::ThreadLocal<const CrashRecoveryContextCleanup> >
70 tlIsRecoveringFromCrash;
71
72 CrashRecoveryContextCleanup::~CrashRecoveryContextCleanup() {}
73
74 CrashRecoveryContext::~CrashRecoveryContext() {
75 // Reclaim registered resources.
76 CrashRecoveryContextCleanup *i = head;
77 tlIsRecoveringFromCrash->set(head);
78 while (i) {
79 CrashRecoveryContextCleanup *tmp = i;
80 i = tmp->next;
81 tmp->cleanupFired = true;
82 tmp->recoverResources();
83 delete tmp;
84 }
85 tlIsRecoveringFromCrash->erase();
86
87 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
88 delete CRCI;
89 }
90
91 bool CrashRecoveryContext::isRecoveringFromCrash() {
92 return tlIsRecoveringFromCrash->get() != 0;
93 }
94
95 CrashRecoveryContext *CrashRecoveryContext::GetCurrent() {
96 if (!gCrashRecoveryEnabled)
97 return 0;
98
99 const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
100 if (!CRCI)
101 return 0;
102
103 return CRCI->CRC;
104 }
105
106 void CrashRecoveryContext::registerCleanup(CrashRecoveryContextCleanup *cleanup)
107 {
108 if (!cleanup)
109 return;
110 if (head)
111 head->prev = cleanup;
112 cleanup->next = head;
113 head = cleanup;
114 }
115
116 void
117 CrashRecoveryContext::unregisterCleanup(CrashRecoveryContextCleanup *cleanup) {
118 if (!cleanup)
119 return;
120 if (cleanup == head) {
121 head = cleanup->next;
122 if (head)
123 head->prev = 0;
124 }
125 else {
126 cleanup->prev->next = cleanup->next;
127 if (cleanup->next)
128 cleanup->next->prev = cleanup->prev;
129 }
130 delete cleanup;
131 }
132
133 #ifdef LLVM_ON_WIN32
134
135 #include "Windows/Windows.h"
136
137 // On Windows, we can make use of vectored exception handling to
138 // catch most crashing situations. Note that this does mean
139 // we will be alerted of exceptions *before* structured exception
140 // handling has the opportunity to catch it. But that isn't likely
141 // to cause problems because nowhere in the project is SEH being
142 // used.
143 //
144 // Vectored exception handling is built on top of SEH, and so it
145 // works on a per-thread basis.
146 //
147 // The vectored exception handler functionality was added in Windows
148 // XP, so if support for older versions of Windows is required,
149 // it will have to be added.
150 //
151 // If we want to support as far back as Win2k, we could use the
152 // SetUnhandledExceptionFilter API, but there's a risk of that
153 // being entirely overwritten (it's not a chain).
154
155 static LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ExceptionInfo)
156 {
157 // Lookup the current thread local recovery object.
158 const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
159
160 if (!CRCI) {
161 // Something has gone horribly wrong, so let's just tell everyone
162 // to keep searching
163 CrashRecoveryContext::Disable();
164 return EXCEPTION_CONTINUE_SEARCH;
165 }
166
167 // TODO: We can capture the stack backtrace here and store it on the
168 // implementation if we so choose.
169
170 // Handle the crash
171 const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
172
173 // Note that we don't actually get here because HandleCrash calls
174 // longjmp, which means the HandleCrash function never returns.
175 llvm_unreachable("Handled the crash, should have longjmp'ed out of here");
176 }
177
178 // Because the Enable and Disable calls are static, it means that
179 // there may not actually be an Impl available, or even a current
180 // CrashRecoveryContext at all. So we make use of a thread-local
181 // exception table. The handles contained in here will either be
182 // non-NULL, valid VEH handles, or NULL.
183 static sys::ThreadLocal<const void> sCurrentExceptionHandle;
184
185 void CrashRecoveryContext::Enable() {
186 sys::ScopedLock L(*gCrashRecoveryContextMutex);
187
188 if (gCrashRecoveryEnabled)
189 return;
190
191 gCrashRecoveryEnabled = true;
192
193 // We can set up vectored exception handling now. We will install our
194 // handler as the front of the list, though there's no assurances that
195 // it will remain at the front (another call could install itself before
196 // our handler). This 1) isn't likely, and 2) shouldn't cause problems.
197 PVOID handle = ::AddVectoredExceptionHandler(1, ExceptionHandler);
198 sCurrentExceptionHandle.set(handle);
199 }
200
201 void CrashRecoveryContext::Disable() {
202 sys::ScopedLock L(*gCrashRecoveryContextMutex);
203
204 if (!gCrashRecoveryEnabled)
205 return;
206
207 gCrashRecoveryEnabled = false;
208
209 PVOID currentHandle = const_cast<PVOID>(sCurrentExceptionHandle.get());
210 if (currentHandle) {
211 // Now we can remove the vectored exception handler from the chain
212 ::RemoveVectoredExceptionHandler(currentHandle);
213
214 // Reset the handle in our thread-local set.
215 sCurrentExceptionHandle.set(NULL);
216 }
217 }
218
219 #else
220
221 // Generic POSIX implementation.
222 //
223 // This implementation relies on synchronous signals being delivered to the
224 // current thread. We use a thread local object to keep track of the active
225 // crash recovery context, and install signal handlers to invoke HandleCrash on
226 // the active object.
227 //
228 // This implementation does not to attempt to chain signal handlers in any
229 // reliable fashion -- if we get a signal outside of a crash recovery context we
230 // simply disable crash recovery and raise the signal again.
231
232 #include <signal.h>
233
234 static const int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP };
235 static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]);
236 static struct sigaction PrevActions[NumSignals];
237
238 static void CrashRecoverySignalHandler(int Signal) {
239 // Lookup the current thread local recovery object.
240 const CrashRecoveryContextImpl *CRCI = CurrentContext->get();
241
242 if (!CRCI) {
243 // We didn't find a crash recovery context -- this means either we got a
244 // signal on a thread we didn't expect it on, the application got a signal
245 // outside of a crash recovery context, or something else went horribly
246 // wrong.
247 //
248 // Disable crash recovery and raise the signal again. The assumption here is
249 // that the enclosing application will terminate soon, and we won't want to
250 // attempt crash recovery again.
251 //
252 // This call of Disable isn't thread safe, but it doesn't actually matter.
253 CrashRecoveryContext::Disable();
254 raise(Signal);
255
256 // The signal will be thrown once the signal mask is restored.
257 return;
258 }
259
260 // Unblock the signal we received.
261 sigset_t SigMask;
262 sigemptyset(&SigMask);
263 sigaddset(&SigMask, Signal);
264 sigprocmask(SIG_UNBLOCK, &SigMask, 0);
265
266 if (CRCI)
267 const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
268 }
269
270 void CrashRecoveryContext::Enable() {
271 sys::ScopedLock L(*gCrashRecoveryContextMutex);
272
273 if (gCrashRecoveryEnabled)
274 return;
275
276 gCrashRecoveryEnabled = true;
277
278 // Setup the signal handler.
279 struct sigaction Handler;
280 Handler.sa_handler = CrashRecoverySignalHandler;
281 Handler.sa_flags = 0;
282 sigemptyset(&Handler.sa_mask);
283
284 for (unsigned i = 0; i != NumSignals; ++i) {
285 sigaction(Signals[i], &Handler, &PrevActions[i]);
286 }
287 }
288
289 void CrashRecoveryContext::Disable() {
290 sys::ScopedLock L(*gCrashRecoveryContextMutex);
291
292 if (!gCrashRecoveryEnabled)
293 return;
294
295 gCrashRecoveryEnabled = false;
296
297 // Restore the previous signal handlers.
298 for (unsigned i = 0; i != NumSignals; ++i)
299 sigaction(Signals[i], &PrevActions[i], 0);
300 }
301
302 #endif
303
304 bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) {
305 // If crash recovery is disabled, do nothing.
306 if (gCrashRecoveryEnabled) {
307 assert(!Impl && "Crash recovery context already initialized!");
308 CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl(this);
309 Impl = CRCI;
310
311 if (setjmp(CRCI->JumpBuffer) != 0) {
312 return false;
313 }
314 }
315
316 Fn(UserData);
317 return true;
318 }
319
320 void CrashRecoveryContext::HandleCrash() {
321 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
322 assert(CRCI && "Crash recovery context never initialized!");
323 CRCI->HandleCrash();
324 }
325
326 const std::string &CrashRecoveryContext::getBacktrace() const {
327 CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl;
328 assert(CRC && "Crash recovery context never initialized!");
329 assert(CRC->Failed && "No crash was detected!");
330 return CRC->Backtrace;
331 }
332
333 //
334
335 namespace {
336 struct RunSafelyOnThreadInfo {
337 void (*UserFn)(void*);
338 void *UserData;
339 CrashRecoveryContext *CRC;
340 bool Result;
341 };
342 }
343
344 static void RunSafelyOnThread_Dispatch(void *UserData) {
345 RunSafelyOnThreadInfo *Info =
346 reinterpret_cast<RunSafelyOnThreadInfo*>(UserData);
347 Info->Result = Info->CRC->RunSafely(Info->UserFn, Info->UserData);
348 }
349 bool CrashRecoveryContext::RunSafelyOnThread(void (*Fn)(void*), void *UserData,
350 unsigned RequestedStackSize) {
351 RunSafelyOnThreadInfo Info = { Fn, UserData, this, false };
352 llvm_execute_on_thread(RunSafelyOnThread_Dispatch, &Info, RequestedStackSize);
353 if (CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *)Impl)
354 CRC->setSwitchedThread();
355 return Info.Result;
356 }