UnwindMap.cpp revision af67fb247540ef084a0b644e1d3bf225db4de6bd 
1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdint.h>
18#include <stdlib.h>
19#include <sys/types.h>
20#include <unistd.h>
21
22#include <backtrace/BacktraceMap.h>
23
24#include <libunwind.h>
25
26#include "BacktraceLog.h"
27#include "UnwindMap.h"
28
29//-------------------------------------------------------------------------
30// libunwind has a single shared address space for the current process
31// aka local. If multiple maps are created for the current pid, then
32// only update the local address space once, and keep a reference count
33// of maps using the same map cursor.
34//-------------------------------------------------------------------------
35UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
36}
37
38UnwindMap::~UnwindMap() {
39  unw_map_cursor_destroy(&map_cursor_);
40  unw_map_cursor_clear(&map_cursor_);
41}
42
43bool UnwindMap::GenerateMap() {
44  // Use the map_cursor information to construct the BacktraceMap data
45  // rather than reparsing /proc/self/maps.
46  unw_map_cursor_reset(&map_cursor_);
47
48  unw_map_t unw_map;
49  while (unw_map_cursor_get_next(&map_cursor_, &unw_map)) {
50    backtrace_map_t map;
51
52    map.start = unw_map.start;
53    map.end = unw_map.end;
54    map.offset = unw_map.offset;
55    map.load_base = unw_map.load_base;
56    map.flags = unw_map.flags;
57    map.name = unw_map.path;
58
59    // The maps are in descending order, but we want them in ascending order.
60    maps_.push_front(map);
61  }
62
63  return true;
64}
65
66bool UnwindMap::Build() {
67  return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
68}
69
70UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
71}
72
73UnwindMapLocal::~UnwindMapLocal() {
74  if (map_created_) {
75    unw_map_local_destroy();
76    unw_map_cursor_clear(&map_cursor_);
77  }
78}
79
80bool UnwindMapLocal::GenerateMap() {
81  // It's possible for the map to be regenerated while this loop is occurring.
82  // If that happens, get the map again, but only try at most three times
83  // before giving up.
84  for (int i = 0; i < 3; i++) {
85    maps_.clear();
86
87    unw_map_local_cursor_get(&map_cursor_);
88
89    unw_map_t unw_map;
90    int ret;
91    while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
92      backtrace_map_t map;
93
94      map.start = unw_map.start;
95      map.end = unw_map.end;
96      map.offset = unw_map.offset;
97      map.load_base = unw_map.load_base;
98      map.flags = unw_map.flags;
99      map.name = unw_map.path;
100
101      free(unw_map.path);
102
103      // The maps are in descending order, but we want them in ascending order.
104      maps_.push_front(map);
105    }
106    // Check to see if the map changed while getting the data.
107    if (ret != -UNW_EINVAL) {
108      return true;
109    }
110  }
111
112  BACK_LOGW("Unable to generate the map.");
113  return false;
114}
115
116bool UnwindMapLocal::Build() {
117  return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
118}
119
120void UnwindMapLocal::FillIn(uintptr_t addr, backtrace_map_t* map) {
121  BacktraceMap::FillIn(addr, map);
122  if (!IsValid(*map)) {
123    // Check to see if the underlying map changed and regenerate the map
124    // if it did.
125    if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
126      if (GenerateMap()) {
127        BacktraceMap::FillIn(addr, map);
128      }
129    }
130  }
131}
132
133//-------------------------------------------------------------------------
134// BacktraceMap create function.
135//-------------------------------------------------------------------------
136BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
137  BacktraceMap* map;
138
139  if (uncached) {
140    // Force use of the base class to parse the maps when this call is made.
141    map = new BacktraceMap(pid);
142  } else if (pid == getpid()) {
143    map = new UnwindMapLocal();
144  } else {
145    map = new UnwindMap(pid);
146  }
147  if (!map->Build()) {
148    delete map;
149    return nullptr;
150  }
151  return map;
152}
153