libbacktrace/BacktraceMap.cpp

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "backtrace-map"

#include <ctype.h>
#include <inttypes.h>
#include <stdint.h>
#include <sys/types.h>
#include <unistd.h>

#include <log/log.h>

#include <android-base/stringprintf.h>
#include <backtrace/Backtrace.h>
#include <backtrace/BacktraceMap.h>
#include <backtrace/backtrace_constants.h>
#if defined(__linux__)
#include <procinfo/process_map.h>
#endif

using android::base::StringPrintf;

std::string backtrace_map_t::Name() const {
  if (!name.empty()) return name;
  if (start == 0 && end == 0) return "";
  return StringPrintf("<anonymous:%" PRIPTR ">", start);
}

BacktraceMap::BacktraceMap(pid_t pid) : pid_(pid) {
  if (pid_ < 0) {
    pid_ = getpid();
  }
}

BacktraceMap::~BacktraceMap() {}

void BacktraceMap::FillIn(uint64_t addr, backtrace_map_t* map) {
  ScopedBacktraceMapIteratorLock lock(this);
  for (auto it = begin(); it != end(); ++it) {
    const backtrace_map_t* entry = *it;
    if (addr >= entry->start && addr < entry->end) {
      *map = *entry;
      return;
    }
  }
  *map = {};
}

#if defined(__APPLE__)
static bool ParseLine(const char* line, backtrace_map_t* map) {
  uint64_t start;
  uint64_t end;
  char permissions[5];
  int name_pos;

  // Mac OS vmmap(1) output:
  // __TEXT                 0009f000-000a1000 [    8K     8K] r-x/rwx SM=COW
  // /Volumes/android/dalvik-dev/out/host/darwin-x86/bin/libcorkscrew_test\n
  // 012345678901234567890123456789012345678901234567890123456789
  // 0         1         2         3         4         5
  if (sscanf(line, "%*21c %" SCNx64 "-%" SCNx64 " [%*13c] %3c/%*3c SM=%*3c  %n", &start, &end,
             permissions, &name_pos) != 3) {
    return false;
  }

  map->start = start;
  map->end = end;
  map->flags = PROT_NONE;
  if (permissions[0] == 'r') {
    map->flags |= PROT_READ;
  }
  if (permissions[1] == 'w') {
    map->flags |= PROT_WRITE;
  }
  if (permissions[2] == 'x') {
    map->flags |= PROT_EXEC;
  }

  map->name = line + name_pos;
  if (!map->name.empty() && map->name[map->name.length() - 1] == '\n') {
    map->name.erase(map->name.length() - 1);
  }

  ALOGV("Parsed map: start=%p, end=%p, flags=%x, name=%s", reinterpret_cast<void*>(map->start),
        reinterpret_cast<void*>(map->end), map->flags, map->name.c_str());
  return true;
}
#endif  // defined(__APPLE__)

bool BacktraceMap::Build() {
#if defined(__APPLE__)
  char
      cmd[sizeof(pid_t) * 3 + sizeof("vmmap -w -resident -submap -allSplitLibs -interleaved ") + 1];
  char line[1024];
  // cmd is guaranteed to always be big enough to hold this string.
  snprintf(cmd, sizeof(cmd), "vmmap -w -resident -submap -allSplitLibs -interleaved %d", pid_);
  FILE* fp = popen(cmd, "r");
  if (fp == nullptr) {
    return false;
  }

  while (fgets(line, sizeof(line), fp)) {
    backtrace_map_t map;
    if (ParseLine(line, &map)) {
      maps_.push_back(map);
    }
  }
  pclose(fp);
  return true;
#else
  return android::procinfo::ReadProcessMaps(
      pid_, [&](uint64_t start, uint64_t end, uint16_t flags, uint64_t, ino_t, const char* name) {
        maps_.resize(maps_.size() + 1);
        backtrace_map_t& map = maps_.back();
        map.start = start;
        map.end = end;
        map.flags = flags;
        map.name = name;
      });
#endif
}

#if defined(__APPLE__)
// Corkscrew and libunwind don't compile on the mac, so create a generic
// map object.
BacktraceMap* BacktraceMap::Create(pid_t pid, bool /*uncached*/) {
  BacktraceMap* map = new BacktraceMap(pid);
  if (!map->Build()) {
    delete map;
    return nullptr;
  }
  return map;
}
#endif