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 <pthread.h>
18 #include <stdint.h>
19 #include <stdlib.h>
20 #include <sys/types.h>
21 #include <unistd.h>
22
23 #include <backtrace/BacktraceMap.h>
24
25 #include <libunwind.h>
26
27 #include "BacktraceLog.h"
28 #include "UnwindMap.h"
29
30 //-------------------------------------------------------------------------
31 // libunwind has a single shared address space for the current process
32 // aka local. If multiple maps are created for the current pid, then
33 // only update the local address space once, and keep a reference count
34 // of maps using the same map cursor.
35 //-------------------------------------------------------------------------
UnwindMap(pid_t pid)36 UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
37 unw_map_cursor_clear(&map_cursor_);
38 }
39
UnwindMapRemote(pid_t pid)40 UnwindMapRemote::UnwindMapRemote(pid_t pid) : UnwindMap(pid) {
41 }
42
~UnwindMapRemote()43 UnwindMapRemote::~UnwindMapRemote() {
44 unw_map_cursor_destroy(&map_cursor_);
45 unw_map_cursor_clear(&map_cursor_);
46 }
47
GenerateMap()48 bool UnwindMapRemote::GenerateMap() {
49 // Use the map_cursor information to construct the BacktraceMap data
50 // rather than reparsing /proc/self/maps.
51 unw_map_cursor_reset(&map_cursor_);
52
53 unw_map_t unw_map;
54 while (unw_map_cursor_get_next(&map_cursor_, &unw_map)) {
55 backtrace_map_t map;
56
57 map.start = unw_map.start;
58 map.end = unw_map.end;
59 map.offset = unw_map.offset;
60 map.load_base = unw_map.load_base;
61 map.flags = unw_map.flags;
62 map.name = unw_map.path;
63
64 // The maps are in descending order, but we want them in ascending order.
65 maps_.push_front(map);
66 }
67
68 return true;
69 }
70
Build()71 bool UnwindMapRemote::Build() {
72 return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
73 }
74
UnwindMapLocal()75 UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
76 pthread_rwlock_init(&map_lock_, nullptr);
77 }
78
~UnwindMapLocal()79 UnwindMapLocal::~UnwindMapLocal() {
80 if (map_created_) {
81 unw_map_local_destroy();
82 unw_map_cursor_clear(&map_cursor_);
83 }
84 }
85
GenerateMap()86 bool UnwindMapLocal::GenerateMap() {
87 // Lock so that multiple threads cannot modify the maps data at the
88 // same time.
89 pthread_rwlock_wrlock(&map_lock_);
90
91 // It's possible for the map to be regenerated while this loop is occurring.
92 // If that happens, get the map again, but only try at most three times
93 // before giving up.
94 bool generated = false;
95 for (int i = 0; i < 3; i++) {
96 maps_.clear();
97
98 // Save the map data retrieved so we can tell if it changes.
99 unw_map_local_cursor_get(&map_cursor_);
100
101 unw_map_t unw_map;
102 int ret;
103 while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
104 backtrace_map_t map;
105
106 map.start = unw_map.start;
107 map.end = unw_map.end;
108 map.offset = unw_map.offset;
109 map.load_base = unw_map.load_base;
110 map.flags = unw_map.flags;
111 map.name = unw_map.path;
112
113 free(unw_map.path);
114
115 // The maps are in descending order, but we want them in ascending order.
116 maps_.push_front(map);
117 }
118 // Check to see if the map changed while getting the data.
119 if (ret != -UNW_EINVAL) {
120 generated = true;
121 break;
122 }
123 }
124
125 pthread_rwlock_unlock(&map_lock_);
126
127 if (!generated) {
128 BACK_LOGW("Unable to generate the map.");
129 }
130 return generated;
131 }
132
Build()133 bool UnwindMapLocal::Build() {
134 return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
135 }
136
FillIn(uintptr_t addr,backtrace_map_t * map)137 void UnwindMapLocal::FillIn(uintptr_t addr, backtrace_map_t* map) {
138 BacktraceMap::FillIn(addr, map);
139 if (!IsValid(*map)) {
140 // Check to see if the underlying map changed and regenerate the map
141 // if it did.
142 if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
143 if (GenerateMap()) {
144 BacktraceMap::FillIn(addr, map);
145 }
146 }
147 }
148 }
149
150 //-------------------------------------------------------------------------
151 // BacktraceMap create function.
152 //-------------------------------------------------------------------------
Create(pid_t pid,bool uncached)153 BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
154 BacktraceMap* map;
155
156 if (uncached) {
157 // Force use of the base class to parse the maps when this call is made.
158 map = new BacktraceMap(pid);
159 } else if (pid == getpid()) {
160 map = new UnwindMapLocal();
161 } else {
162 map = new UnwindMapRemote(pid);
163 }
164 if (!map->Build()) {
165 delete map;
166 return nullptr;
167 }
168 return map;
169 }
170