base/debug/stack_trace_android.cc

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

#include "base/debug/stack_trace.h"

#include <android/log.h>
#include <dlfcn.h>
#include <stddef.h>
#include <unwind.h>

#include <algorithm>
#include <ostream>
#include <string_view>

#include "base/compiler_specific.h"
#include "base/debug/debugging_buildflags.h"
#include "base/debug/elf_reader.h"
#include "base/debug/proc_maps_linux.h"
#include "base/memory/raw_ptr.h"
#include "base/strings/strcat.h"
#include "base/strings/stringprintf.h"
#include "base/threading/thread_restrictions.h"

#ifdef __LP64__
#define FMT_ADDR "0x%016lx"
#else
#define FMT_ADDR "0x%08x"
#endif

#if BUILDFLAG(EXCLUDE_UNWIND_TABLES) && \
    BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
#define UNWIND_WITH_FRAME_POINTERS 1
#else
#define UNWIND_WITH_FRAME_POINTERS 0
#endif

namespace {

#if !UNWIND_WITH_FRAME_POINTERS
struct StackCrawlState {
  StackCrawlState(uintptr_t* frames, size_t max_depth)
      : frames(frames),
        frame_count(0),
        max_depth(max_depth),
        have_skipped_self(false) {}

  raw_ptr<uintptr_t, AllowPtrArithmetic> frames;
  size_t frame_count;
  size_t max_depth;
  bool have_skipped_self;
};

_Unwind_Reason_Code TraceStackFrame(_Unwind_Context* context, void* arg) {
  StackCrawlState* state = static_cast<StackCrawlState*>(arg);
  uintptr_t ip = _Unwind_GetIP(context);

  // The first stack frame is this function itself.  Skip it.
  if (ip != 0 && !state->have_skipped_self) {
    state->have_skipped_self = true;
    return _URC_NO_REASON;
  }

  UNSAFE_TODO(state->frames[state->frame_count++] = ip);
  if (state->frame_count >= state->max_depth) {
    return _URC_END_OF_STACK;
  }
  return _URC_NO_REASON;
}
#endif  // !UNWIND_WITH_FRAME_POINTERS

}  // namespace

namespace base {
namespace debug {

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.
  // TODO(phajdan.jr): De-duplicate this SIGPIPE code.
  struct sigaction action = {};
  action.sa_handler = SIG_IGN;
  sigemptyset(&action.sa_mask);
  return (sigaction(SIGPIPE, &action, NULL) == 0);
}

size_t CollectStackTrace(span<const void*> trace) {
#if UNWIND_WITH_FRAME_POINTERS
  return TraceStackFramePointers(trace, 0);
#else
  StackCrawlState state(reinterpret_cast<uintptr_t*>(trace.data()),
                        trace.size());
  _Unwind_Backtrace(&TraceStackFrame, &state);
  return state.frame_count;
#endif
#undef UNWIND_WITH_FRAME_POINTERS
}

// static
void StackTrace::PrintMessageWithPrefix(cstring_view prefix_string,
                                        cstring_view message) {
  if (!prefix_string.empty()) {
    __android_log_write(ANDROID_LOG_ERROR, "chromium",
                        StrCat({prefix_string, message}).c_str());
  } else {
    __android_log_write(ANDROID_LOG_ERROR, "chromium", message.c_str());
  }
}

void StackTrace::PrintWithPrefixImpl(cstring_view prefix_string) const {
  std::string backtrace = ToStringWithPrefix(prefix_string);
  __android_log_write(ANDROID_LOG_ERROR, "chromium", backtrace.c_str());
}

// NOTE: Native libraries in APKs are stripped before installing. Print out the
// relocatable address and library names so host computers can use tools to
// symbolize and demangle (e.g., addr2line, c++filt).
void StackTrace::OutputToStreamWithPrefixImpl(
    std::ostream* os,
    cstring_view prefix_string) const {
  std::string proc_maps;
  std::vector<MappedMemoryRegion> regions;
  // Allow IO to read /proc/self/maps. Reading this file doesn't hit the disk
  // since it lives in procfs, and this is currently used to print a stack trace
  // on fatal log messages in debug builds only. If the restriction is enabled
  // then it will recursively trigger fatal failures when this enters on the
  // UI thread.
  base::ScopedAllowBlocking scoped_allow_blocking;
  if (!ReadProcMaps(&proc_maps)) {
    __android_log_write(ANDROID_LOG_ERROR, "chromium",
                        "Failed to read /proc/self/maps");
  } else if (!ParseProcMaps(proc_maps, &regions)) {
    __android_log_write(ANDROID_LOG_ERROR, "chromium",
                        "Failed to parse /proc/self/maps");
  }

  for (size_t i = 0; i < count_; ++i) {
    // Subtract one as return address of function may be in the next
    // function when a function is annotated as noreturn.
    uintptr_t address = reinterpret_cast<uintptr_t>(trace_[i]) - 1;

    std::vector<MappedMemoryRegion>::iterator iter = regions.begin();
    while (iter != regions.end()) {
      if (address >= iter->start && address < iter->end &&
          !iter->path.empty()) {
        break;
      }
      ++iter;
    }

    *os << prefix_string;

    Dl_info dl_info;
    const bool dl_info_found =
        dladdr(reinterpret_cast<const void*>(address), &dl_info) &&
        dl_info.dli_fbase;

    // Adjust absolute address to be an offset within the mapped region, to
    // match the format dumped by Android's crash output.
    if (iter != regions.end()) {
      address -= iter->start;
    }

    // The format below intentionally matches that of Android's debuggerd
    // output. This simplifies decoding by scripts such as stack.py.
    *os << base::StringPrintf("#%02zd pc " FMT_ADDR " ", i, address);

    if (iter != regions.end()) {
      *os << base::StringPrintf("%s", iter->path.c_str());
      if (iter->path.ends_with(".apk")) {
        *os << base::StringPrintf(" (offset 0x%llx)", iter->offset);
      }
    } else {
      *os << "<unknown>";
    }

    if (dl_info_found) {
      ElfBuildIdBuffer build_id;
      size_t build_id_len =
          ReadElfBuildId(dl_info.dli_fbase, /*uppercase=*/false, build_id);
      if (build_id_len > 0) {
        *os << " (BuildId: " << std::string_view(build_id, build_id_len) << ")";
      }
    }

    *os << "\n";
  }
}

}  // namespace debug
}  // namespace base