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