1 //===- PrettyStackTrace.cpp - Pretty Crash Handling -----------------------===//
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 // This file defines some helpful functions for dealing with the possibility of
11 // Unix signals occurring while your program is running.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Support/PrettyStackTrace.h"
16 #include "llvm-c/ErrorHandling.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/Config/config.h" // Get autoconf configuration settings
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/Signals.h"
21 #include "llvm/Support/Watchdog.h"
22 #include "llvm/Support/raw_ostream.h"
23 
24 #include <cstdarg>
25 #include <cstdio>
26 #include <tuple>
27 
28 #ifdef HAVE_CRASHREPORTERCLIENT_H
29 #include <CrashReporterClient.h>
30 #endif
31 
32 using namespace llvm;
33 
34 // If backtrace support is not enabled, compile out support for pretty stack
35 // traces.  This has the secondary effect of not requiring thread local storage
36 // when backtrace support is disabled.
37 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
38 
39 // We need a thread local pointer to manage the stack of our stack trace
40 // objects, but we *really* cannot tolerate destructors running and do not want
41 // to pay any overhead of synchronizing. As a consequence, we use a raw
42 // thread-local variable.
43 static LLVM_THREAD_LOCAL PrettyStackTraceEntry *PrettyStackTraceHead = nullptr;
44 
45 namespace llvm {
46 PrettyStackTraceEntry *ReverseStackTrace(PrettyStackTraceEntry *Head) {
47   PrettyStackTraceEntry *Prev = nullptr;
48   while (Head)
49     std::tie(Prev, Head, Head->NextEntry) =
50         std::make_tuple(Head, Head->NextEntry, Prev);
51   return Prev;
52 }
53 }
54 
55 static void PrintStack(raw_ostream &OS) {
56   // Print out the stack in reverse order. To avoid recursion (which is likely
57   // to fail if we crashed due to stack overflow), we do an up-front pass to
58   // reverse the stack, then print it, then reverse it again.
59   unsigned ID = 0;
60   PrettyStackTraceEntry *ReversedStack =
61       llvm::ReverseStackTrace(PrettyStackTraceHead);
62   for (const PrettyStackTraceEntry *Entry = ReversedStack; Entry;
63        Entry = Entry->getNextEntry()) {
64     OS << ID++ << ".\t";
65     sys::Watchdog W(5);
66     Entry->print(OS);
67   }
68   llvm::ReverseStackTrace(ReversedStack);
69 }
70 
71 /// PrintCurStackTrace - Print the current stack trace to the specified stream.
72 static void PrintCurStackTrace(raw_ostream &OS) {
73   // Don't print an empty trace.
74   if (!PrettyStackTraceHead) return;
75 
76   // If there are pretty stack frames registered, walk and emit them.
77   OS << "Stack dump:\n";
78 
79   PrintStack(OS);
80   OS.flush();
81 }
82 
83 // Integrate with crash reporter libraries.
84 #if defined (__APPLE__) && defined(HAVE_CRASHREPORTERCLIENT_H)
85 //  If any clients of llvm try to link to libCrashReporterClient.a themselves,
86 //  only one crash info struct will be used.
87 extern "C" {
88 CRASH_REPORTER_CLIENT_HIDDEN
89 struct crashreporter_annotations_t gCRAnnotations
90         __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION)))
91         = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
92 }
93 #elif defined(__APPLE__) && HAVE_CRASHREPORTER_INFO
94 extern "C" const char *__crashreporter_info__
95     __attribute__((visibility("hidden"))) = 0;
96 asm(".desc ___crashreporter_info__, 0x10");
97 #endif
98 
99 /// CrashHandler - This callback is run if a fatal signal is delivered to the
100 /// process, it prints the pretty stack trace.
101 static void CrashHandler(void *) {
102 #ifndef __APPLE__
103   // On non-apple systems, just emit the crash stack trace to stderr.
104   PrintCurStackTrace(errs());
105 #else
106   // Otherwise, emit to a smallvector of chars, send *that* to stderr, but also
107   // put it into __crashreporter_info__.
108   SmallString<2048> TmpStr;
109   {
110     raw_svector_ostream Stream(TmpStr);
111     PrintCurStackTrace(Stream);
112   }
113 
114   if (!TmpStr.empty()) {
115 #ifdef HAVE_CRASHREPORTERCLIENT_H
116     // Cast to void to avoid warning.
117     (void)CRSetCrashLogMessage(std::string(TmpStr.str()).c_str());
118 #elif HAVE_CRASHREPORTER_INFO
119     __crashreporter_info__ = strdup(std::string(TmpStr.str()).c_str());
120 #endif
121     errs() << TmpStr.str();
122   }
123 
124 #endif
125 }
126 
127 // defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
128 #endif
129 
130 PrettyStackTraceEntry::PrettyStackTraceEntry() {
131 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
132   // Link ourselves.
133   NextEntry = PrettyStackTraceHead;
134   PrettyStackTraceHead = this;
135 #endif
136 }
137 
138 PrettyStackTraceEntry::~PrettyStackTraceEntry() {
139 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
140   assert(PrettyStackTraceHead == this &&
141          "Pretty stack trace entry destruction is out of order");
142   PrettyStackTraceHead = NextEntry;
143 #endif
144 }
145 
146 void PrettyStackTraceString::print(raw_ostream &OS) const { OS << Str << "\n"; }
147 
148 PrettyStackTraceFormat::PrettyStackTraceFormat(const char *Format, ...) {
149   va_list AP;
150   va_start(AP, Format);
151   const int SizeOrError = vsnprintf(nullptr, 0, Format, AP);
152   va_end(AP);
153   if (SizeOrError < 0) {
154     return;
155   }
156 
157   const int Size = SizeOrError + 1; // '\0'
158   Str.resize(Size);
159   va_start(AP, Format);
160   vsnprintf(Str.data(), Size, Format, AP);
161   va_end(AP);
162 }
163 
164 void PrettyStackTraceFormat::print(raw_ostream &OS) const { OS << Str << "\n"; }
165 
166 void PrettyStackTraceProgram::print(raw_ostream &OS) const {
167   OS << "Program arguments: ";
168   // Print the argument list.
169   for (unsigned i = 0, e = ArgC; i != e; ++i)
170     OS << ArgV[i] << ' ';
171   OS << '\n';
172 }
173 
174 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
175 static bool RegisterCrashPrinter() {
176   sys::AddSignalHandler(CrashHandler, nullptr);
177   return false;
178 }
179 #endif
180 
181 void llvm::EnablePrettyStackTrace() {
182 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
183   // The first time this is called, we register the crash printer.
184   static bool HandlerRegistered = RegisterCrashPrinter();
185   (void)HandlerRegistered;
186 #endif
187 }
188 
189 const void *llvm::SavePrettyStackState() {
190 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
191   return PrettyStackTraceHead;
192 #else
193   return nullptr;
194 #endif
195 }
196 
197 void llvm::RestorePrettyStackState(const void *Top) {
198 #if defined(HAVE_BACKTRACE) && ENABLE_BACKTRACES
199   PrettyStackTraceHead =
200       static_cast<PrettyStackTraceEntry *>(const_cast<void *>(Top));
201 #endif
202 }
203 
204 void LLVMEnablePrettyStackTrace() {
205   EnablePrettyStackTrace();
206 }
207