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/System/Mutex.h"
14 #include "llvm/System/ThreadLocal.h"
15 #include <setjmp.h>
16 #include <cstdio>
17 using namespace llvm;
18
19 namespace {
20
21 struct CrashRecoveryContextImpl;
22
23 static sys::ThreadLocal<const CrashRecoveryContextImpl> CurrentContext;
24
25 struct CrashRecoveryContextImpl {
26 CrashRecoveryContext *CRC;
27 std::string Backtrace;
28 ::jmp_buf JumpBuffer;
29 volatile unsigned Failed : 1;
30
31 public:
CrashRecoveryContextImpl__anon59d521ad0111::CrashRecoveryContextImpl32 CrashRecoveryContextImpl(CrashRecoveryContext *CRC) : CRC(CRC),
33 Failed(false) {
34 CurrentContext.set(this);
35 }
~CrashRecoveryContextImpl__anon59d521ad0111::CrashRecoveryContextImpl36 ~CrashRecoveryContextImpl() {
37 CurrentContext.erase();
38 }
39
HandleCrash__anon59d521ad0111::CrashRecoveryContextImpl40 void HandleCrash() {
41 // Eliminate the current context entry, to avoid re-entering in case the
42 // cleanup code crashes.
43 CurrentContext.erase();
44
45 assert(!Failed && "Crash recovery context already failed!");
46 Failed = true;
47
48 // FIXME: Stash the backtrace.
49
50 // Jump back to the RunSafely we were called under.
51 longjmp(JumpBuffer, 1);
52 }
53 };
54
55 }
56
57 static sys::Mutex gCrashRecoveryContexMutex;
58 static bool gCrashRecoveryEnabled = false;
59
~CrashRecoveryContext()60 CrashRecoveryContext::~CrashRecoveryContext() {
61 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
62 delete CRCI;
63 }
64
GetCurrent()65 CrashRecoveryContext *CrashRecoveryContext::GetCurrent() {
66 const CrashRecoveryContextImpl *CRCI = CurrentContext.get();
67 if (!CRCI)
68 return 0;
69
70 return CRCI->CRC;
71 }
72
73 #ifdef LLVM_ON_WIN32
74
75 // FIXME: No real Win32 implementation currently.
76
Enable()77 void CrashRecoveryContext::Enable() {
78 sys::ScopedLock L(gCrashRecoveryContexMutex);
79
80 if (gCrashRecoveryEnabled)
81 return;
82
83 gCrashRecoveryEnabled = true;
84 }
85
Disable()86 void CrashRecoveryContext::Disable() {
87 sys::ScopedLock L(gCrashRecoveryContexMutex);
88
89 if (!gCrashRecoveryEnabled)
90 return;
91
92 gCrashRecoveryEnabled = false;
93 }
94
95 #else
96
97 // Generic POSIX implementation.
98 //
99 // This implementation relies on synchronous signals being delivered to the
100 // current thread. We use a thread local object to keep track of the active
101 // crash recovery context, and install signal handlers to invoke HandleCrash on
102 // the active object.
103 //
104 // This implementation does not to attempt to chain signal handlers in any
105 // reliable fashion -- if we get a signal outside of a crash recovery context we
106 // simply disable crash recovery and raise the signal again.
107
108 #include <signal.h>
109
110 static int Signals[] = { SIGABRT, SIGBUS, SIGFPE, SIGILL, SIGSEGV, SIGTRAP };
111 static const unsigned NumSignals = sizeof(Signals) / sizeof(Signals[0]);
112 static struct sigaction PrevActions[NumSignals];
113
CrashRecoverySignalHandler(int Signal)114 static void CrashRecoverySignalHandler(int Signal) {
115 // Lookup the current thread local recovery object.
116 const CrashRecoveryContextImpl *CRCI = CurrentContext.get();
117
118 if (!CRCI) {
119 // We didn't find a crash recovery context -- this means either we got a
120 // signal on a thread we didn't expect it on, the application got a signal
121 // outside of a crash recovery context, or something else went horribly
122 // wrong.
123 //
124 // Disable crash recovery and raise the signal again. The assumption here is
125 // that the enclosing application will terminate soon, and we won't want to
126 // attempt crash recovery again.
127 //
128 // This call of Disable isn't thread safe, but it doesn't actually matter.
129 CrashRecoveryContext::Disable();
130 raise(Signal);
131 }
132
133 // Unblock the signal we received.
134 sigset_t SigMask;
135 sigemptyset(&SigMask);
136 sigaddset(&SigMask, Signal);
137 sigprocmask(SIG_UNBLOCK, &SigMask, 0);
138
139 if (CRCI)
140 const_cast<CrashRecoveryContextImpl*>(CRCI)->HandleCrash();
141 }
142
Enable()143 void CrashRecoveryContext::Enable() {
144 sys::ScopedLock L(gCrashRecoveryContexMutex);
145
146 if (gCrashRecoveryEnabled)
147 return;
148
149 gCrashRecoveryEnabled = true;
150
151 // Setup the signal handler.
152 struct sigaction Handler;
153 Handler.sa_handler = CrashRecoverySignalHandler;
154 Handler.sa_flags = 0;
155 sigemptyset(&Handler.sa_mask);
156
157 for (unsigned i = 0; i != NumSignals; ++i) {
158 sigaction(Signals[i], &Handler, &PrevActions[i]);
159 }
160 }
161
Disable()162 void CrashRecoveryContext::Disable() {
163 sys::ScopedLock L(gCrashRecoveryContexMutex);
164
165 if (!gCrashRecoveryEnabled)
166 return;
167
168 gCrashRecoveryEnabled = false;
169
170 // Restore the previous signal handlers.
171 for (unsigned i = 0; i != NumSignals; ++i)
172 sigaction(Signals[i], &PrevActions[i], 0);
173 }
174
175 #endif
176
RunSafely(void (* Fn)(void *),void * UserData)177 bool CrashRecoveryContext::RunSafely(void (*Fn)(void*), void *UserData) {
178 // If crash recovery is disabled, do nothing.
179 if (gCrashRecoveryEnabled) {
180 assert(!Impl && "Crash recovery context already initialized!");
181 CrashRecoveryContextImpl *CRCI = new CrashRecoveryContextImpl(this);
182 Impl = CRCI;
183
184 if (setjmp(CRCI->JumpBuffer) != 0) {
185 return false;
186 }
187 }
188
189 Fn(UserData);
190 return true;
191 }
192
HandleCrash()193 void CrashRecoveryContext::HandleCrash() {
194 CrashRecoveryContextImpl *CRCI = (CrashRecoveryContextImpl *) Impl;
195 assert(CRCI && "Crash recovery context never initialized!");
196 CRCI->HandleCrash();
197 }
198
getBacktrace() const199 const std::string &CrashRecoveryContext::getBacktrace() const {
200 CrashRecoveryContextImpl *CRC = (CrashRecoveryContextImpl *) Impl;
201 assert(CRC && "Crash recovery context never initialized!");
202 assert(CRC->Failed && "No crash was detected!");
203 return CRC->Backtrace;
204 }
205