LLVM 17.0.0git
PrettyStackTrace.cpp
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1//===- PrettyStackTrace.cpp - Pretty Crash Handling -----------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines some helpful functions for dealing with the possibility of
10// Unix signals occurring while your program is running.
11//
12//===----------------------------------------------------------------------===//
13
16#include "llvm/Config/config.h"
22
23#ifdef __APPLE__
25#endif
26
27#include <atomic>
28#include <cassert>
29#include <cstdarg>
30#include <cstdio>
31#include <cstring>
32#include <tuple>
33
34#ifdef HAVE_CRASHREPORTERCLIENT_H
35#include <CrashReporterClient.h>
36#endif
37
38using namespace llvm;
39
40static const char *BugReportMsg =
41 "PLEASE submit a bug report to " BUG_REPORT_URL
42 " and include the crash backtrace.\n";
43
44// If backtrace support is not enabled, compile out support for pretty stack
45// traces. This has the secondary effect of not requiring thread local storage
46// when backtrace support is disabled.
47#if ENABLE_BACKTRACES
48
49// We need a thread local pointer to manage the stack of our stack trace
50// objects, but we *really* cannot tolerate destructors running and do not want
51// to pay any overhead of synchronizing. As a consequence, we use a raw
52// thread-local variable.
53static LLVM_THREAD_LOCAL PrettyStackTraceEntry *PrettyStackTraceHead = nullptr;
54
55// The use of 'volatile' here is to ensure that any particular thread always
56// reloads the value of the counter. The 'std::atomic' allows us to specify that
57// this variable is accessed in an unsychronized way (it's not actually
58// synchronizing). This does technically mean that the value may not appear to
59// be the same across threads running simultaneously on different CPUs, but in
60// practice the worst that will happen is that we won't print a stack trace when
61// we could have.
62//
63// This is initialized to 1 because 0 is used as a sentinel for "not enabled on
64// the current thread". If the user happens to overflow an 'unsigned' with
65// SIGINFO requests, it's possible that some threads will stop responding to it,
66// but the program won't crash.
67static volatile std::atomic<unsigned> GlobalSigInfoGenerationCounter =
68 ATOMIC_VAR_INIT(1);
69static LLVM_THREAD_LOCAL unsigned ThreadLocalSigInfoGenerationCounter = 0;
70
71namespace llvm {
72PrettyStackTraceEntry *ReverseStackTrace(PrettyStackTraceEntry *Head) {
73 PrettyStackTraceEntry *Prev = nullptr;
74 while (Head)
75 std::tie(Prev, Head, Head->NextEntry) =
76 std::make_tuple(Head, Head->NextEntry, Prev);
77 return Prev;
78}
79} // namespace llvm
80
81static void PrintStack(raw_ostream &OS) {
82 // Print out the stack in reverse order. To avoid recursion (which is likely
83 // to fail if we crashed due to stack overflow), we do an up-front pass to
84 // reverse the stack, then print it, then reverse it again.
85 unsigned ID = 0;
86 SaveAndRestore<PrettyStackTraceEntry *> SavedStack{PrettyStackTraceHead,
87 nullptr};
88 PrettyStackTraceEntry *ReversedStack = ReverseStackTrace(SavedStack.get());
89 for (const PrettyStackTraceEntry *Entry = ReversedStack; Entry;
90 Entry = Entry->getNextEntry()) {
91 OS << ID++ << ".\t";
93 Entry->print(OS);
94 }
95 llvm::ReverseStackTrace(ReversedStack);
96}
97
98/// Print the current stack trace to the specified stream.
99///
100/// Marked NOINLINE so it can be called from debuggers.
102static void PrintCurStackTrace(raw_ostream &OS) {
103 // Don't print an empty trace.
104 if (!PrettyStackTraceHead) return;
105
106 // If there are pretty stack frames registered, walk and emit them.
107 OS << "Stack dump:\n";
108
109 PrintStack(OS);
110 OS.flush();
111}
112
113// Integrate with crash reporter libraries.
114#if defined (__APPLE__) && defined(HAVE_CRASHREPORTERCLIENT_H)
115// If any clients of llvm try to link to libCrashReporterClient.a themselves,
116// only one crash info struct will be used.
117extern "C" {
118CRASH_REPORTER_CLIENT_HIDDEN
119struct crashreporter_annotations_t gCRAnnotations
120 __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION)))
121#if CRASHREPORTER_ANNOTATIONS_VERSION < 5
122 = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
123#else
124 = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0, 0 };
125#endif
126}
127#elif defined(__APPLE__) && HAVE_CRASHREPORTER_INFO
128extern "C" const char *__crashreporter_info__
129 __attribute__((visibility("hidden"))) = 0;
130asm(".desc ___crashreporter_info__, 0x10");
131#endif
132
133static void setCrashLogMessage(const char *msg) LLVM_ATTRIBUTE_UNUSED;
134static void setCrashLogMessage(const char *msg) {
135#ifdef HAVE_CRASHREPORTERCLIENT_H
136 (void)CRSetCrashLogMessage(msg);
137#elif HAVE_CRASHREPORTER_INFO
138 __crashreporter_info__ = msg;
139#endif
140 // Don't reorder subsequent operations: whatever comes after might crash and
141 // we want the system crash handling to see the message we just set.
142 std::atomic_signal_fence(std::memory_order_seq_cst);
143}
144
145#ifdef __APPLE__
146using CrashHandlerString = SmallString<2048>;
147using CrashHandlerStringStorage =
148 std::aligned_storage<sizeof(CrashHandlerString),
149 alignof(CrashHandlerString)>::type;
150static CrashHandlerStringStorage crashHandlerStringStorage;
151#endif
152
153/// This callback is run if a fatal signal is delivered to the process, it
154/// prints the pretty stack trace.
155static void CrashHandler(void *) {
156 errs() << BugReportMsg ;
157
158#ifndef __APPLE__
159 // On non-apple systems, just emit the crash stack trace to stderr.
160 PrintCurStackTrace(errs());
161#else
162 // Emit the crash stack trace to a SmallString, put it where the system crash
163 // handling will find it, and also send it to stderr.
164 //
165 // The SmallString is fairly large in the hope that we don't allocate (we're
166 // handling a fatal signal, something is already pretty wrong, allocation
167 // might not work). Further, we don't use a magic static in case that's also
168 // borked. We leak any allocation that does occur because the program is about
169 // to die anyways. This is technically racy if we were handling two fatal
170 // signals, however if we're in that situation a race is the least of our
171 // worries.
172 auto &crashHandlerString =
173 *new (&crashHandlerStringStorage) CrashHandlerString;
174
175 // If we crash while trying to print the stack trace, we still want the system
176 // crash handling to have some partial information. That'll work out as long
177 // as the SmallString doesn't allocate. If it does allocate then the system
178 // crash handling will see some garbage because the inline buffer now contains
179 // a pointer.
180 setCrashLogMessage(crashHandlerString.c_str());
181
182 {
183 raw_svector_ostream Stream(crashHandlerString);
184 PrintCurStackTrace(Stream);
185 }
186
187 if (!crashHandlerString.empty()) {
188 setCrashLogMessage(crashHandlerString.c_str());
189 errs() << crashHandlerString.str();
190 } else
191 setCrashLogMessage("No crash information.");
192#endif
193}
194
195static void printForSigInfoIfNeeded() {
196 unsigned CurrentSigInfoGeneration =
197 GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed);
198 if (ThreadLocalSigInfoGenerationCounter == 0 ||
199 ThreadLocalSigInfoGenerationCounter == CurrentSigInfoGeneration) {
200 return;
201 }
202
203 PrintCurStackTrace(errs());
204 ThreadLocalSigInfoGenerationCounter = CurrentSigInfoGeneration;
205}
206
207#endif // ENABLE_BACKTRACES
208
209void llvm::setBugReportMsg(const char *Msg) {
210 BugReportMsg = Msg;
211}
212
214 return BugReportMsg;
215}
216
218#if ENABLE_BACKTRACES
219 // Handle SIGINFO first, because we haven't finished constructing yet.
220 printForSigInfoIfNeeded();
221 // Link ourselves.
222 NextEntry = PrettyStackTraceHead;
223 PrettyStackTraceHead = this;
224#endif
225}
226
228#if ENABLE_BACKTRACES
229 assert(PrettyStackTraceHead == this &&
230 "Pretty stack trace entry destruction is out of order");
231 PrettyStackTraceHead = NextEntry;
232 // Handle SIGINFO first, because we already started destructing.
233 printForSigInfoIfNeeded();
234#endif
235}
236
237void PrettyStackTraceString::print(raw_ostream &OS) const { OS << Str << "\n"; }
238
240 va_list AP;
241 va_start(AP, Format);
242 const int SizeOrError = vsnprintf(nullptr, 0, Format, AP);
243 va_end(AP);
244 if (SizeOrError < 0) {
245 return;
246 }
247
248 const int Size = SizeOrError + 1; // '\0'
249 Str.resize(Size);
250 va_start(AP, Format);
251 vsnprintf(Str.data(), Size, Format, AP);
252 va_end(AP);
253}
254
255void PrettyStackTraceFormat::print(raw_ostream &OS) const { OS << Str << "\n"; }
256
258 OS << "Program arguments: ";
259 // Print the argument list.
260 for (int I = 0; I < ArgC; ++I) {
261 const bool HaveSpace = ::strchr(ArgV[I], ' ');
262 if (I)
263 OS << ' ';
264 if (HaveSpace)
265 OS << '"';
266 OS.write_escaped(ArgV[I]);
267 if (HaveSpace)
268 OS << '"';
269 }
270 OS << '\n';
271}
272
273#if ENABLE_BACKTRACES
274static bool RegisterCrashPrinter() {
275 sys::AddSignalHandler(CrashHandler, nullptr);
276 return false;
277}
278#endif
279
281#if ENABLE_BACKTRACES
282 // The first time this is called, we register the crash printer.
283 static bool HandlerRegistered = RegisterCrashPrinter();
284 (void)HandlerRegistered;
285#endif
286}
287
289#if ENABLE_BACKTRACES
290 if (!ShouldEnable) {
291 ThreadLocalSigInfoGenerationCounter = 0;
292 return;
293 }
294
295 // The first time this is called, we register the SIGINFO handler.
296 static bool HandlerRegistered = []{
298 GlobalSigInfoGenerationCounter.fetch_add(1, std::memory_order_relaxed);
299 });
300 return false;
301 }();
302 (void)HandlerRegistered;
303
304 // Next, enable it for the current thread.
305 ThreadLocalSigInfoGenerationCounter =
306 GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed);
307#endif
308}
309
311#if ENABLE_BACKTRACES
312 return PrettyStackTraceHead;
313#else
314 return nullptr;
315#endif
316}
317
318void llvm::RestorePrettyStackState(const void *Top) {
319#if ENABLE_BACKTRACES
320 PrettyStackTraceHead =
321 static_cast<PrettyStackTraceEntry *>(const_cast<void *>(Top));
322#endif
323}
324
327}
#define LLVM_THREAD_LOCAL
\macro LLVM_THREAD_LOCAL A thread-local storage specifier which can be used with globals,...
Definition: Compiler.h:532
#define LLVM_ATTRIBUTE_NOINLINE
LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so, mark a method "not for inl...
Definition: Compiler.h:220
#define LLVM_ATTRIBUTE_UNUSED
Definition: Compiler.h:172
uint64_t Size
#define I(x, y, z)
Definition: MD5.cpp:58
if(VerifyEach)
static const char * BugReportMsg
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file provides utility classes that use RAII to save and restore values.
This file defines the SmallString class.
PrettyStackTraceEntry - This class is used to represent a frame of the "pretty" stack trace that is d...
void print(raw_ostream &OS) const override
print - Emit information about this stack frame to OS.
PrettyStackTraceFormat(const char *Format,...)
void print(raw_ostream &OS) const override
print - Emit information about this stack frame to OS.
void print(raw_ostream &OS) const override
print - Emit information about this stack frame to OS.
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition: SmallString.h:26
void resize(size_type N)
Definition: SmallVector.h:642
pointer data()
Return a pointer to the vector's buffer, even if empty().
Definition: SmallVector.h:289
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
raw_ostream & write_escaped(StringRef Str, bool UseHexEscapes=false)
Output Str, turning '\', '\t', ' ', '"', and anything that doesn't satisfy llvm::isPrint into an esca...
A raw_ostream that writes to an SmallVector or SmallString.
Definition: raw_ostream.h:672
This class provides an abstraction for a timeout around an operation that must complete in a given am...
Definition: Watchdog.h:25
void LLVMEnablePrettyStackTrace(void)
Enable LLVM's built-in stack trace code.
void AddSignalHandler(SignalHandlerCallback FnPtr, void *Cookie)
Add a function to be called when an abort/kill signal is delivered to the process.
void SetInfoSignalFunction(void(*Handler)())
Registers a function to be called when an "info" signal is delivered to the process.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void setBugReportMsg(const char *Msg)
Replaces the generic bug report message that is output upon a crash.
const void * SavePrettyStackState()
Returns the topmost element of the "pretty" stack state.
raw_fd_ostream & errs()
This returns a reference to a raw_ostream for standard error.
void RestorePrettyStackState(const void *State)
Restores the topmost element of the "pretty" stack state to State, which should come from a previous ...
void EnablePrettyStackTraceOnSigInfoForThisThread(bool ShouldEnable=true)
Enables (or disables) dumping a "pretty" stack trace when the user sends SIGINFO or SIGUSR1 to the cu...
void EnablePrettyStackTrace()
Enables dumping a "pretty" stack trace when the program crashes.
const char * getBugReportMsg()
Get the bug report message that will be output upon a crash.
A utility class that uses RAII to save and restore the value of a variable.