| //===- PrettyStackTrace.cpp - Pretty Crash Handling -----------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines some helpful functions for dealing with the possibility of |
| // Unix signals occurring while your program is running. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Support/PrettyStackTrace.h" |
| #include "llvm-c/ErrorHandling.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/Config/config.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/SaveAndRestore.h" |
| #include "llvm/Support/Signals.h" |
| #include "llvm/Support/Watchdog.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| #include <atomic> |
| #include <cassert> |
| #include <cstdarg> |
| #include <cstdio> |
| #include <cstring> |
| #include <tuple> |
| |
| #ifdef HAVE_CRASHREPORTERCLIENT_H |
| #include <CrashReporterClient.h> |
| #endif |
| |
| using namespace llvm; |
| |
| static const char *BugReportMsg = |
| "PLEASE submit a bug report to " BUG_REPORT_URL |
| " and include the crash backtrace.\n"; |
| |
| // If backtrace support is not enabled, compile out support for pretty stack |
| // traces. This has the secondary effect of not requiring thread local storage |
| // when backtrace support is disabled. |
| #if ENABLE_BACKTRACES |
| |
| // We need a thread local pointer to manage the stack of our stack trace |
| // objects, but we *really* cannot tolerate destructors running and do not want |
| // to pay any overhead of synchronizing. As a consequence, we use a raw |
| // thread-local variable. |
| static LLVM_THREAD_LOCAL PrettyStackTraceEntry *PrettyStackTraceHead = nullptr; |
| |
| // The use of 'volatile' here is to ensure that any particular thread always |
| // reloads the value of the counter. The 'std::atomic' allows us to specify that |
| // this variable is accessed in an unsychronized way (it's not actually |
| // synchronizing). This does technically mean that the value may not appear to |
| // be the same across threads running simultaneously on different CPUs, but in |
| // practice the worst that will happen is that we won't print a stack trace when |
| // we could have. |
| // |
| // This is initialized to 1 because 0 is used as a sentinel for "not enabled on |
| // the current thread". If the user happens to overflow an 'unsigned' with |
| // SIGINFO requests, it's possible that some threads will stop responding to it, |
| // but the program won't crash. |
| static volatile std::atomic<unsigned> GlobalSigInfoGenerationCounter = |
| ATOMIC_VAR_INIT(1); |
| static LLVM_THREAD_LOCAL unsigned ThreadLocalSigInfoGenerationCounter = 0; |
| |
| namespace llvm { |
| PrettyStackTraceEntry *ReverseStackTrace(PrettyStackTraceEntry *Head) { |
| PrettyStackTraceEntry *Prev = nullptr; |
| while (Head) |
| std::tie(Prev, Head, Head->NextEntry) = |
| std::make_tuple(Head, Head->NextEntry, Prev); |
| return Prev; |
| } |
| } // namespace llvm |
| |
| static void PrintStack(raw_ostream &OS) { |
| // Print out the stack in reverse order. To avoid recursion (which is likely |
| // to fail if we crashed due to stack overflow), we do an up-front pass to |
| // reverse the stack, then print it, then reverse it again. |
| unsigned ID = 0; |
| SaveAndRestore<PrettyStackTraceEntry *> SavedStack{PrettyStackTraceHead, |
| nullptr}; |
| PrettyStackTraceEntry *ReversedStack = ReverseStackTrace(SavedStack.get()); |
| for (const PrettyStackTraceEntry *Entry = ReversedStack; Entry; |
| Entry = Entry->getNextEntry()) { |
| OS << ID++ << ".\t"; |
| sys::Watchdog W(5); |
| Entry->print(OS); |
| } |
| llvm::ReverseStackTrace(ReversedStack); |
| } |
| |
| /// Print the current stack trace to the specified stream. |
| /// |
| /// Marked NOINLINE so it can be called from debuggers. |
| LLVM_ATTRIBUTE_NOINLINE |
| static void PrintCurStackTrace(raw_ostream &OS) { |
| // Don't print an empty trace. |
| if (!PrettyStackTraceHead) return; |
| |
| // If there are pretty stack frames registered, walk and emit them. |
| OS << "Stack dump:\n"; |
| |
| PrintStack(OS); |
| OS.flush(); |
| } |
| |
| // Integrate with crash reporter libraries. |
| #if defined (__APPLE__) && defined(HAVE_CRASHREPORTERCLIENT_H) |
| // If any clients of llvm try to link to libCrashReporterClient.a themselves, |
| // only one crash info struct will be used. |
| extern "C" { |
| CRASH_REPORTER_CLIENT_HIDDEN |
| struct crashreporter_annotations_t gCRAnnotations |
| __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION))) |
| #if CRASHREPORTER_ANNOTATIONS_VERSION < 5 |
| = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 }; |
| #else |
| = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0, 0 }; |
| #endif |
| } |
| #elif defined(__APPLE__) && HAVE_CRASHREPORTER_INFO |
| extern "C" const char *__crashreporter_info__ |
| __attribute__((visibility("hidden"))) = 0; |
| asm(".desc ___crashreporter_info__, 0x10"); |
| #endif |
| |
| static void setCrashLogMessage(const char *msg) LLVM_ATTRIBUTE_UNUSED; |
| static void setCrashLogMessage(const char *msg) { |
| #ifdef HAVE_CRASHREPORTERCLIENT_H |
| (void)CRSetCrashLogMessage(msg); |
| #elif HAVE_CRASHREPORTER_INFO |
| __crashreporter_info__ = msg; |
| #endif |
| // Don't reorder subsequent operations: whatever comes after might crash and |
| // we want the system crash handling to see the message we just set. |
| std::atomic_signal_fence(std::memory_order_seq_cst); |
| } |
| |
| #ifdef __APPLE__ |
| using CrashHandlerString = SmallString<2048>; |
| using CrashHandlerStringStorage = |
| std::aligned_storage<sizeof(CrashHandlerString), |
| alignof(CrashHandlerString)>::type; |
| static CrashHandlerStringStorage crashHandlerStringStorage; |
| #endif |
| |
| /// This callback is run if a fatal signal is delivered to the process, it |
| /// prints the pretty stack trace. |
| static void CrashHandler(void *) { |
| errs() << BugReportMsg ; |
| |
| #ifndef __APPLE__ |
| // On non-apple systems, just emit the crash stack trace to stderr. |
| PrintCurStackTrace(errs()); |
| #else |
| // Emit the crash stack trace to a SmallString, put it where the system crash |
| // handling will find it, and also send it to stderr. |
| // |
| // The SmallString is fairly large in the hope that we don't allocate (we're |
| // handling a fatal signal, something is already pretty wrong, allocation |
| // might not work). Further, we don't use a magic static in case that's also |
| // borked. We leak any allocation that does occur because the program is about |
| // to die anyways. This is technically racy if we were handling two fatal |
| // signals, however if we're in that situation a race is the least of our |
| // worries. |
| auto &crashHandlerString = |
| *new (&crashHandlerStringStorage) CrashHandlerString; |
| |
| // If we crash while trying to print the stack trace, we still want the system |
| // crash handling to have some partial information. That'll work out as long |
| // as the SmallString doesn't allocate. If it does allocate then the system |
| // crash handling will see some garbage because the inline buffer now contains |
| // a pointer. |
| setCrashLogMessage(crashHandlerString.c_str()); |
| |
| { |
| raw_svector_ostream Stream(crashHandlerString); |
| PrintCurStackTrace(Stream); |
| } |
| |
| if (!crashHandlerString.empty()) { |
| setCrashLogMessage(crashHandlerString.c_str()); |
| errs() << crashHandlerString.str(); |
| } else |
| setCrashLogMessage("No crash information."); |
| #endif |
| } |
| |
| static void printForSigInfoIfNeeded() { |
| unsigned CurrentSigInfoGeneration = |
| GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed); |
| if (ThreadLocalSigInfoGenerationCounter == 0 || |
| ThreadLocalSigInfoGenerationCounter == CurrentSigInfoGeneration) { |
| return; |
| } |
| |
| PrintCurStackTrace(errs()); |
| ThreadLocalSigInfoGenerationCounter = CurrentSigInfoGeneration; |
| } |
| |
| #endif // ENABLE_BACKTRACES |
| |
| void llvm::setBugReportMsg(const char *Msg) { |
| BugReportMsg = Msg; |
| } |
| |
| const char *llvm::getBugReportMsg() { |
| return BugReportMsg; |
| } |
| |
| PrettyStackTraceEntry::PrettyStackTraceEntry() { |
| #if ENABLE_BACKTRACES |
| // Handle SIGINFO first, because we haven't finished constructing yet. |
| printForSigInfoIfNeeded(); |
| // Link ourselves. |
| NextEntry = PrettyStackTraceHead; |
| PrettyStackTraceHead = this; |
| #endif |
| } |
| |
| PrettyStackTraceEntry::~PrettyStackTraceEntry() { |
| #if ENABLE_BACKTRACES |
| assert(PrettyStackTraceHead == this && |
| "Pretty stack trace entry destruction is out of order"); |
| PrettyStackTraceHead = NextEntry; |
| // Handle SIGINFO first, because we already started destructing. |
| printForSigInfoIfNeeded(); |
| #endif |
| } |
| |
| void PrettyStackTraceString::print(raw_ostream &OS) const { OS << Str << "\n"; } |
| |
| PrettyStackTraceFormat::PrettyStackTraceFormat(const char *Format, ...) { |
| va_list AP; |
| va_start(AP, Format); |
| const int SizeOrError = vsnprintf(nullptr, 0, Format, AP); |
| va_end(AP); |
| if (SizeOrError < 0) { |
| return; |
| } |
| |
| const int Size = SizeOrError + 1; // '\0' |
| Str.resize(Size); |
| va_start(AP, Format); |
| vsnprintf(Str.data(), Size, Format, AP); |
| va_end(AP); |
| } |
| |
| void PrettyStackTraceFormat::print(raw_ostream &OS) const { OS << Str << "\n"; } |
| |
| void PrettyStackTraceProgram::print(raw_ostream &OS) const { |
| OS << "Program arguments: "; |
| // Print the argument list. |
| for (int I = 0; I < ArgC; ++I) { |
| const bool HaveSpace = ::strchr(ArgV[I], ' '); |
| if (I) |
| OS << ' '; |
| if (HaveSpace) |
| OS << '"'; |
| OS.write_escaped(ArgV[I]); |
| if (HaveSpace) |
| OS << '"'; |
| } |
| OS << '\n'; |
| } |
| |
| #if ENABLE_BACKTRACES |
| static bool RegisterCrashPrinter() { |
| sys::AddSignalHandler(CrashHandler, nullptr); |
| return false; |
| } |
| #endif |
| |
| void llvm::EnablePrettyStackTrace() { |
| #if ENABLE_BACKTRACES |
| // The first time this is called, we register the crash printer. |
| static bool HandlerRegistered = RegisterCrashPrinter(); |
| (void)HandlerRegistered; |
| #endif |
| } |
| |
| void llvm::EnablePrettyStackTraceOnSigInfoForThisThread(bool ShouldEnable) { |
| #if ENABLE_BACKTRACES |
| if (!ShouldEnable) { |
| ThreadLocalSigInfoGenerationCounter = 0; |
| return; |
| } |
| |
| // The first time this is called, we register the SIGINFO handler. |
| static bool HandlerRegistered = []{ |
| sys::SetInfoSignalFunction([]{ |
| GlobalSigInfoGenerationCounter.fetch_add(1, std::memory_order_relaxed); |
| }); |
| return false; |
| }(); |
| (void)HandlerRegistered; |
| |
| // Next, enable it for the current thread. |
| ThreadLocalSigInfoGenerationCounter = |
| GlobalSigInfoGenerationCounter.load(std::memory_order_relaxed); |
| #endif |
| } |
| |
| const void *llvm::SavePrettyStackState() { |
| #if ENABLE_BACKTRACES |
| return PrettyStackTraceHead; |
| #else |
| return nullptr; |
| #endif |
| } |
| |
| void llvm::RestorePrettyStackState(const void *Top) { |
| #if ENABLE_BACKTRACES |
| PrettyStackTraceHead = |
| static_cast<PrettyStackTraceEntry *>(const_cast<void *>(Top)); |
| #endif |
| } |
| |
| void LLVMEnablePrettyStackTrace() { |
| EnablePrettyStackTrace(); |
| } |