LLVM 19.0.0git
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 = 1;
68static LLVM_THREAD_LOCAL unsigned ThreadLocalSigInfoGenerationCounter = 0;
69
70namespace llvm {
71PrettyStackTraceEntry *ReverseStackTrace(PrettyStackTraceEntry *Head) {
72 PrettyStackTraceEntry *Prev = nullptr;
73 while (Head)
74 std::tie(Prev, Head, Head->NextEntry) =
75 std::make_tuple(Head, Head->NextEntry, Prev);
76 return Prev;
77}
78} // namespace llvm
79
80static void PrintStack(raw_ostream &OS) {
81 // Print out the stack in reverse order. To avoid recursion (which is likely
82 // to fail if we crashed due to stack overflow), we do an up-front pass to
83 // reverse the stack, then print it, then reverse it again.
84 unsigned ID = 0;
85 SaveAndRestore<PrettyStackTraceEntry *> SavedStack{PrettyStackTraceHead,
86 nullptr};
87 PrettyStackTraceEntry *ReversedStack = ReverseStackTrace(SavedStack.get());
88 for (const PrettyStackTraceEntry *Entry = ReversedStack; Entry;
89 Entry = Entry->getNextEntry()) {
90 OS << ID++ << ".\t";
92 Entry->print(OS);
93 }
94 llvm::ReverseStackTrace(ReversedStack);
95}
96
97/// Print the current stack trace to the specified stream.
98///
99/// Marked NOINLINE so it can be called from debuggers.
101static void PrintCurStackTrace(raw_ostream &OS) {
102 // Don't print an empty trace.
103 if (!PrettyStackTraceHead) return;
104
105 // If there are pretty stack frames registered, walk and emit them.
106 OS << "Stack dump:\n";
107
108 PrintStack(OS);
109 OS.flush();
110}
111
112// Integrate with crash reporter libraries.
113#if defined (__APPLE__) && defined(HAVE_CRASHREPORTERCLIENT_H)
114// If any clients of llvm try to link to libCrashReporterClient.a themselves,
115// only one crash info struct will be used.
116extern "C" {
117CRASH_REPORTER_CLIENT_HIDDEN
118struct crashreporter_annotations_t gCRAnnotations
119 __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION)))
120#if CRASHREPORTER_ANNOTATIONS_VERSION < 5
121 = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
122#else
123 = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0, 0 };
124#endif
125}
126#elif defined(__APPLE__) && HAVE_CRASHREPORTER_INFO
127extern "C" const char *__crashreporter_info__
128 __attribute__((visibility("hidden"))) = 0;
129asm(".desc ___crashreporter_info__, 0x10");
130#endif
131
132static void setCrashLogMessage(const char *msg) LLVM_ATTRIBUTE_UNUSED;
133static void setCrashLogMessage(const char *msg) {
134#ifdef HAVE_CRASHREPORTERCLIENT_H
135 (void)CRSetCrashLogMessage(msg);
136#elif HAVE_CRASHREPORTER_INFO
137 __crashreporter_info__ = msg;
138#endif
139 // Don't reorder subsequent operations: whatever comes after might crash and
140 // we want the system crash handling to see the message we just set.
141 std::atomic_signal_fence(std::memory_order_seq_cst);
142}
143
144#ifdef __APPLE__
145using CrashHandlerString = SmallString<2048>;
146using CrashHandlerStringStorage = std::byte[sizeof(CrashHandlerString)];
147alignas(CrashHandlerString) static CrashHandlerStringStorage
148 crashHandlerStringStorage;
149#endif
150
151/// This callback is run if a fatal signal is delivered to the process, it
152/// prints the pretty stack trace.
153static void CrashHandler(void *) {
154 errs() << BugReportMsg ;
155
156#ifndef __APPLE__
157 // On non-apple systems, just emit the crash stack trace to stderr.
158 PrintCurStackTrace(errs());
159#else
160 // Emit the crash stack trace to a SmallString, put it where the system crash
161 // handling will find it, and also send it to stderr.
162 //
163 // The SmallString is fairly large in the hope that we don't allocate (we're
164 // handling a fatal signal, something is already pretty wrong, allocation
165 // might not work). Further, we don't use a magic static in case that's also
166 // borked. We leak any allocation that does occur because the program is about
167 // to die anyways. This is technically racy if we were handling two fatal
168 // signals, however if we're in that situation a race is the least of our
169 // worries.
170 auto &crashHandlerString =
171 *new (&crashHandlerStringStorage) CrashHandlerString;
172
173 // If we crash while trying to print the stack trace, we still want the system
174 // crash handling to have some partial information. That'll work out as long
175 // as the SmallString doesn't allocate. If it does allocate then the system
176 // crash handling will see some garbage because the inline buffer now contains
177 // a pointer.
178 setCrashLogMessage(crashHandlerString.c_str());
179
180 {
181 raw_svector_ostream Stream(crashHandlerString);
182 PrintCurStackTrace(Stream);
183 }
184
185 if (!crashHandlerString.empty()) {
186 setCrashLogMessage(crashHandlerString.c_str());
187 errs() << crashHandlerString.str();
188 } else
189 setCrashLogMessage("No crash information.");
190#endif
191}
192
193static void printForSigInfoIfNeeded() {
194 unsigned CurrentSigInfoGeneration =
195 GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed);
196 if (ThreadLocalSigInfoGenerationCounter == 0 ||
197 ThreadLocalSigInfoGenerationCounter == CurrentSigInfoGeneration) {
198 return;
199 }
200
201 PrintCurStackTrace(errs());
202 ThreadLocalSigInfoGenerationCounter = CurrentSigInfoGeneration;
203}
204
205#endif // ENABLE_BACKTRACES
206
207void llvm::setBugReportMsg(const char *Msg) {
208 BugReportMsg = Msg;
209}
210
212 return BugReportMsg;
213}
214
216#if ENABLE_BACKTRACES
217 // Handle SIGINFO first, because we haven't finished constructing yet.
218 printForSigInfoIfNeeded();
219 // Link ourselves.
220 NextEntry = PrettyStackTraceHead;
221 PrettyStackTraceHead = this;
222#endif
223}
224
226#if ENABLE_BACKTRACES
227 assert(PrettyStackTraceHead == this &&
228 "Pretty stack trace entry destruction is out of order");
229 PrettyStackTraceHead = NextEntry;
230 // Handle SIGINFO first, because we already started destructing.
231 printForSigInfoIfNeeded();
232#endif
233}
234
235void PrettyStackTraceString::print(raw_ostream &OS) const { OS << Str << "\n"; }
236
238 va_list AP;
239 va_start(AP, Format);
240 const int SizeOrError = vsnprintf(nullptr, 0, Format, AP);
241 va_end(AP);
242 if (SizeOrError < 0) {
243 return;
244 }
245
246 const int Size = SizeOrError + 1; // '\0'
247 Str.resize(Size);
248 va_start(AP, Format);
249 vsnprintf(Str.data(), Size, Format, AP);
250 va_end(AP);
251}
252
253void PrettyStackTraceFormat::print(raw_ostream &OS) const { OS << Str << "\n"; }
254
256 OS << "Program arguments: ";
257 // Print the argument list.
258 for (int I = 0; I < ArgC; ++I) {
259 const bool HaveSpace = ::strchr(ArgV[I], ' ');
260 if (I)
261 OS << ' ';
262 if (HaveSpace)
263 OS << '"';
264 OS.write_escaped(ArgV[I]);
265 if (HaveSpace)
266 OS << '"';
267 }
268 OS << '\n';
269}
270
271#if ENABLE_BACKTRACES
272static bool RegisterCrashPrinter() {
273 sys::AddSignalHandler(CrashHandler, nullptr);
274 return false;
275}
276#endif
277
279#if ENABLE_BACKTRACES
280 // The first time this is called, we register the crash printer.
281 static bool HandlerRegistered = RegisterCrashPrinter();
282 (void)HandlerRegistered;
283#endif
284}
285
287#if ENABLE_BACKTRACES
288 if (!ShouldEnable) {
289 ThreadLocalSigInfoGenerationCounter = 0;
290 return;
291 }
292
293 // The first time this is called, we register the SIGINFO handler.
294 static bool HandlerRegistered = []{
296 GlobalSigInfoGenerationCounter.fetch_add(1, std::memory_order_relaxed);
297 });
298 return false;
299 }();
300 (void)HandlerRegistered;
301
302 // Next, enable it for the current thread.
303 ThreadLocalSigInfoGenerationCounter =
304 GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed);
305#endif
306}
307
309#if ENABLE_BACKTRACES
310 return PrettyStackTraceHead;
311#else
312 return nullptr;
313#endif
314}
315
316void llvm::RestorePrettyStackState(const void *Top) {
317#if ENABLE_BACKTRACES
318 PrettyStackTraceHead =
319 static_cast<PrettyStackTraceEntry *>(const_cast<void *>(Top));
320#endif
321}
322
325}
#define LLVM_THREAD_LOCAL
\macro LLVM_THREAD_LOCAL A thread-local storage specifier which can be used with globals,...
Definition: Compiler.h:577
#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:251
#define LLVM_ATTRIBUTE_UNUSED
Definition: Compiler.h:203
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())
raw_pwrite_stream & OS
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:651
pointer data()
Return a pointer to the vector's buffer, even if empty().
Definition: SmallVector.h:299
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:691
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.