stack_trace_posix.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Slightly adapted for inclusion in V8.
// Copyright 2016 the V8 project authors. All rights reserved.

#include "src/base/debug/stack_trace.h"

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <map>
#include <memory>
#include <ostream>
#include <string>
#include <vector>

#if V8_LIBC_GLIBC || V8_LIBC_BSD || V8_LIBC_UCLIBC || V8_OS_SOLARIS
#define HAVE_EXECINFO_H 1
#endif

#if HAVE_EXECINFO_H
#include <cxxabi.h>
#include <execinfo.h>
#endif
#if V8_OS_MACOSX
#include <AvailabilityMacros.h>
#endif

#include "src/base/build_config.h"
#include "src/base/free_deleter.h"
#include "src/base/logging.h"
#include "src/base/macros.h"

namespace v8 {
namespace base {
namespace debug {

namespace internal {

// POSIX doesn't define any async-signal safe function for converting
// an integer to ASCII. We'll have to define our own version.
// itoa_r() converts a (signed) integer to ASCII. It returns "buf", if the
// conversion was successful or nullptr otherwise. It never writes more than
// "sz" bytes. Output will be truncated as needed, and a NUL character is always
// appended.
char* itoa_r(intptr_t i, char* buf, size_t sz, int base, size_t padding);

}  // namespace internal

namespace {

volatile sig_atomic_t in_signal_handler = 0;
bool dump_stack_in_signal_handler = true;

// The prefix used for mangled symbols, per the Itanium C++ ABI:
// http://www.codesourcery.com/cxx-abi/abi.html#mangling
const char kMangledSymbolPrefix[] = "_Z";

// Characters that can be used for symbols, generated by Ruby:
// (('a'..'z').to_a+('A'..'Z').to_a+('0'..'9').to_a + ['_']).join
const char kSymbolCharacters[] =
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";

#if HAVE_EXECINFO_H
// Demangles C++ symbols in the given text. Example:
//
// "out/Debug/base_unittests(_ZN10StackTraceC1Ev+0x20) [0x817778c]"
// =>
// "out/Debug/base_unittests(StackTrace::StackTrace()+0x20) [0x817778c]"
void DemangleSymbols(std::string* text) {
  // Note: code in this function is NOT async-signal safe (std::string uses
  // malloc internally).


  std::string::size_type search_from = 0;
  while (search_from < text->size()) {
    // Look for the start of a mangled symbol, from search_from.
    std::string::size_type mangled_start =
        text->find(kMangledSymbolPrefix, search_from);
    if (mangled_start == std::string::npos) {
      break;  // Mangled symbol not found.
    }

    // Look for the end of the mangled symbol.
    std::string::size_type mangled_end =
        text->find_first_not_of(kSymbolCharacters, mangled_start);
    if (mangled_end == std::string::npos) {
      mangled_end = text->size();
    }
    std::string mangled_symbol =
        text->substr(mangled_start, mangled_end - mangled_start);

    // Try to demangle the mangled symbol candidate.
    int status = 0;
    std::unique_ptr<char, FreeDeleter> demangled_symbol(
        abi::__cxa_demangle(mangled_symbol.c_str(), nullptr, nullptr, &status));
    if (status == 0) {  // Demangling is successful.
      // Remove the mangled symbol.
      text->erase(mangled_start, mangled_end - mangled_start);
      // Insert the demangled symbol.
      text->insert(mangled_start, demangled_symbol.get());
      // Next time, we'll start right after the demangled symbol we inserted.
      search_from = mangled_start + strlen(demangled_symbol.get());
    } else {
      // Failed to demangle.  Retry after the "_Z" we just found.
      search_from = mangled_start + 2;
    }
  }
}
#endif  // HAVE_EXECINFO_H

class BacktraceOutputHandler {
 public:
  virtual void HandleOutput(const char* output) = 0;

 protected:
  virtual ~BacktraceOutputHandler() = default;
};

#if HAVE_EXECINFO_H
void OutputPointer(void* pointer, BacktraceOutputHandler* handler) {
  // This should be more than enough to store a 64-bit number in hex:
  // 16 hex digits + 1 for null-terminator.
  char buf[17] = {'\0'};
  handler->HandleOutput("0x");
  internal::itoa_r(reinterpret_cast<intptr_t>(pointer), buf, sizeof(buf), 16,
                   12);
  handler->HandleOutput(buf);
}

void ProcessBacktrace(void* const* trace, size_t size,
                      BacktraceOutputHandler* handler) {
  // NOTE: This code MUST be async-signal safe (it's used by in-process
  // stack dumping signal handler). NO malloc or stdio is allowed here.
  handler->HandleOutput("\n");
  handler->HandleOutput("==== C stack trace ===============================\n");
  handler->HandleOutput("\n");

  bool printed = false;

  // Below part is async-signal unsafe (uses malloc), so execute it only
  // when we are not executing the signal handler.
  if (in_signal_handler == 0) {
    std::unique_ptr<char*, FreeDeleter> trace_symbols(
        backtrace_symbols(trace, static_cast<int>(size)));
    if (trace_symbols.get()) {
      for (size_t i = 0; i < size; ++i) {
        std::string trace_symbol = trace_symbols.get()[i];
        DemangleSymbols(&trace_symbol);
        handler->HandleOutput("    ");
        handler->HandleOutput(trace_symbol.c_str());
        handler->HandleOutput("\n");
      }

      printed = true;
    }
  }

  if (!printed) {
    for (size_t i = 0; i < size; ++i) {
      handler->HandleOutput(" [");
      OutputPointer(trace[i], handler);
      handler->HandleOutput("]\n");
    }
  }
}
#endif  // HAVE_EXECINFO_H

void PrintToStderr(const char* output) {
  // NOTE: This code MUST be async-signal safe (it's used by in-process
  // stack dumping signal handler). NO malloc or stdio is allowed here.
  ssize_t return_val = write(STDERR_FILENO, output, strlen(output));
  USE(return_val);
}

void StackDumpSignalHandler(int signal, siginfo_t* info, void* void_context) {
  // NOTE: This code MUST be async-signal safe.
  // NO malloc or stdio is allowed here.

  // Record the fact that we are in the signal handler now, so that the rest
  // of StackTrace can behave in an async-signal-safe manner.
  in_signal_handler = 1;

  PrintToStderr("Received signal ");
  char buf[1024] = {0};
  internal::itoa_r(signal, buf, sizeof(buf), 10, 0);
  PrintToStderr(buf);
  if (signal == SIGBUS) {
    if (info->si_code == BUS_ADRALN)
      PrintToStderr(" BUS_ADRALN ");
    else if (info->si_code == BUS_ADRERR)
      PrintToStderr(" BUS_ADRERR ");
    else if (info->si_code == BUS_OBJERR)
      PrintToStderr(" BUS_OBJERR ");
    else
      PrintToStderr(" <unknown> ");
  } else if (signal == SIGFPE) {
    if (info->si_code == FPE_FLTDIV)
      PrintToStderr(" FPE_FLTDIV ");
    else if (info->si_code == FPE_FLTINV)
      PrintToStderr(" FPE_FLTINV ");
    else if (info->si_code == FPE_FLTOVF)
      PrintToStderr(" FPE_FLTOVF ");
    else if (info->si_code == FPE_FLTRES)
      PrintToStderr(" FPE_FLTRES ");
    else if (info->si_code == FPE_FLTSUB)
      PrintToStderr(" FPE_FLTSUB ");
    else if (info->si_code == FPE_FLTUND)
      PrintToStderr(" FPE_FLTUND ");
    else if (info->si_code == FPE_INTDIV)
      PrintToStderr(" FPE_INTDIV ");
    else if (info->si_code == FPE_INTOVF)
      PrintToStderr(" FPE_INTOVF ");
    else
      PrintToStderr(" <unknown> ");
  } else if (signal == SIGILL) {
    if (info->si_code == ILL_BADSTK)
      PrintToStderr(" ILL_BADSTK ");
    else if (info->si_code == ILL_COPROC)
      PrintToStderr(" ILL_COPROC ");
    else if (info->si_code == ILL_ILLOPN)
      PrintToStderr(" ILL_ILLOPN ");
    else if (info->si_code == ILL_ILLADR)
      PrintToStderr(" ILL_ILLADR ");
    else if (info->si_code == ILL_ILLTRP)
      PrintToStderr(" ILL_ILLTRP ");
    else if (info->si_code == ILL_PRVOPC)
      PrintToStderr(" ILL_PRVOPC ");
    else if (info->si_code == ILL_PRVREG)
      PrintToStderr(" ILL_PRVREG ");
    else
      PrintToStderr(" <unknown> ");
  } else if (signal == SIGSEGV) {
    if (info->si_code == SEGV_MAPERR)
      PrintToStderr(" SEGV_MAPERR ");
    else if (info->si_code == SEGV_ACCERR)
      PrintToStderr(" SEGV_ACCERR ");
    else
      PrintToStderr(" <unknown> ");
  }
  if (signal == SIGBUS || signal == SIGFPE || signal == SIGILL ||
      signal == SIGSEGV) {
    internal::itoa_r(reinterpret_cast<intptr_t>(info->si_addr), buf,
                     sizeof(buf), 16, 12);
    PrintToStderr(buf);
  }
  PrintToStderr("\n");
  if (dump_stack_in_signal_handler) {
    debug::StackTrace().Print();
    PrintToStderr("[end of stack trace]\n");
  }

  if (::signal(signal, SIG_DFL) == SIG_ERR) _exit(1);
}

class PrintBacktraceOutputHandler : public BacktraceOutputHandler {
 public:
  PrintBacktraceOutputHandler() = default;

  void HandleOutput(const char* output) override {
    // NOTE: This code MUST be async-signal safe (it's used by in-process
    // stack dumping signal handler). NO malloc or stdio is allowed here.
    PrintToStderr(output);
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(PrintBacktraceOutputHandler);
};

class StreamBacktraceOutputHandler : public BacktraceOutputHandler {
 public:
  explicit StreamBacktraceOutputHandler(std::ostream* os) : os_(os) {}

  void HandleOutput(const char* output) override { (*os_) << output; }

 private:
  std::ostream* os_;

  DISALLOW_COPY_AND_ASSIGN(StreamBacktraceOutputHandler);
};

void WarmUpBacktrace() {
  // Warm up stack trace infrastructure. It turns out that on the first
  // call glibc initializes some internal data structures using pthread_once,
  // and even backtrace() can call malloc(), leading to hangs.
  //
  // Example stack trace snippet (with tcmalloc):
  //
  // #8  0x0000000000a173b5 in tc_malloc
  //             at ./third_party/tcmalloc/chromium/src/debugallocation.cc:1161
  // #9  0x00007ffff7de7900 in _dl_map_object_deps at dl-deps.c:517
  // #10 0x00007ffff7ded8a9 in dl_open_worker at dl-open.c:262
  // #11 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
  // #12 0x00007ffff7ded31a in _dl_open (file=0x7ffff625e298 "libgcc_s.so.1")
  //             at dl-open.c:639
  // #13 0x00007ffff6215602 in do_dlopen at dl-libc.c:89
  // #14 0x00007ffff7de9176 in _dl_catch_error at dl-error.c:178
  // #15 0x00007ffff62156c4 in dlerror_run at dl-libc.c:48
  // #16 __GI___libc_dlopen_mode at dl-libc.c:165
  // #17 0x00007ffff61ef8f5 in init
  //             at ../sysdeps/x86_64/../ia64/backtrace.c:53
  // #18 0x00007ffff6aad400 in pthread_once
  //             at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_once.S:104
  // #19 0x00007ffff61efa14 in __GI___backtrace
  //             at ../sysdeps/x86_64/../ia64/backtrace.c:104
  // #20 0x0000000000752a54 in base::debug::StackTrace::StackTrace
  //             at base/debug/stack_trace_posix.cc:175
  // #21 0x00000000007a4ae5 in
  //             base::(anonymous namespace)::StackDumpSignalHandler
  //             at base/process_util_posix.cc:172
  // #22 <signal handler called>
  StackTrace stack_trace;
}

}  // namespace

bool EnableInProcessStackDumping() {
  // When running in an application, our code typically expects SIGPIPE
  // to be ignored.  Therefore, when testing that same code, it should run
  // with SIGPIPE ignored as well.
  struct sigaction sigpipe_action;
  memset(&sigpipe_action, 0, sizeof(sigpipe_action));
  sigpipe_action.sa_handler = SIG_IGN;
  sigemptyset(&sigpipe_action.sa_mask);
  bool success = (sigaction(SIGPIPE, &sigpipe_action, nullptr) == 0);

  // Avoid hangs during backtrace initialization, see above.
  WarmUpBacktrace();

  struct sigaction action;
  memset(&action, 0, sizeof(action));
  action.sa_flags = SA_RESETHAND | SA_SIGINFO;
  action.sa_sigaction = &StackDumpSignalHandler;
  sigemptyset(&action.sa_mask);

  success &= (sigaction(SIGILL, &action, nullptr) == 0);
  success &= (sigaction(SIGABRT, &action, nullptr) == 0);
  success &= (sigaction(SIGFPE, &action, nullptr) == 0);
  success &= (sigaction(SIGBUS, &action, nullptr) == 0);
  success &= (sigaction(SIGSEGV, &action, nullptr) == 0);
  success &= (sigaction(SIGSYS, &action, nullptr) == 0);

  dump_stack_in_signal_handler = true;

  return success;
}

void DisableSignalStackDump() {
  dump_stack_in_signal_handler = false;
}

StackTrace::StackTrace() {
  // NOTE: This code MUST be async-signal safe (it's used by in-process
  // stack dumping signal handler). NO malloc or stdio is allowed here.

#if HAVE_EXECINFO_H
  // Though the backtrace API man page does not list any possible negative
  // return values, we take no chance.
  count_ = static_cast<size_t>(backtrace(trace_, arraysize(trace_)));
#else
  count_ = 0;
#endif
}

void StackTrace::Print() const {
  // NOTE: This code MUST be async-signal safe (it's used by in-process
  // stack dumping signal handler). NO malloc or stdio is allowed here.

#if HAVE_EXECINFO_H
  PrintBacktraceOutputHandler handler;
  ProcessBacktrace(trace_, count_, &handler);
#endif
}

void StackTrace::OutputToStream(std::ostream* os) const {
#if HAVE_EXECINFO_H
  StreamBacktraceOutputHandler handler(os);
  ProcessBacktrace(trace_, count_, &handler);
#endif
}

namespace internal {

// NOTE: code from sandbox/linux/seccomp-bpf/demo.cc.
char* itoa_r(intptr_t i, char* buf, size_t sz, int base, size_t padding) {
  // Make sure we can write at least one NUL byte.
  size_t n = 1;
  if (n > sz) return nullptr;

  if (base < 2 || base > 16) {
    buf[0] = '\0';
    return nullptr;
  }

  char* start = buf;

  uintptr_t j = i;

  // Handle negative numbers (only for base 10).
  if (i < 0 && base == 10) {
    // This does "j = -i" while avoiding integer overflow.
    j = static_cast<uintptr_t>(-(i + 1)) + 1;

    // Make sure we can write the '-' character.
    if (++n > sz) {
      buf[0] = '\0';
      return nullptr;
    }
    *start++ = '-';
  }

  // Loop until we have converted the entire number. Output at least one
  // character (i.e. '0').
  char* ptr = start;
  do {
    // Make sure there is still enough space left in our output buffer.
    if (++n > sz) {
      buf[0] = '\0';
      return nullptr;
    }

    // Output the next digit.
    *ptr++ = "0123456789abcdef"[j % base];
    j /= base;

    if (padding > 0) padding--;
  } while (j > 0 || padding > 0);

  // Terminate the output with a NUL character.
  *ptr = '\0';

  // Conversion to ASCII actually resulted in the digits being in reverse
  // order. We can't easily generate them in forward order, as we can't tell
  // the number of characters needed until we are done converting.
  // So, now, we reverse the string (except for the possible "-" sign).
  while (--ptr > start) {
    char ch = *ptr;
    *ptr = *start;
    *start++ = ch;
  }
  return buf;
}

}  // namespace internal

}  // namespace debug
}  // namespace base
}  // namespace v8