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 <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 //-------------------------------------------------------------------------
UnwindMap(pid_t pid)35 UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
36 }
37
~UnwindMap()38 UnwindMap::~UnwindMap() {
39 unw_map_cursor_destroy(&map_cursor_);
40 unw_map_cursor_clear(&map_cursor_);
41 }
42
GenerateMap()43 bool 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.flags = unw_map.flags;
55 map.name = unw_map.path;
56
57 // The maps are in descending order, but we want them in ascending order.
58 maps_.push_front(map);
59 }
60
61 return true;
62 }
63
Build()64 bool UnwindMap::Build() {
65 return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
66 }
67
UnwindMapLocal()68 UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
69 }
70
~UnwindMapLocal()71 UnwindMapLocal::~UnwindMapLocal() {
72 if (map_created_) {
73 unw_map_local_destroy();
74 unw_map_cursor_clear(&map_cursor_);
75 }
76 }
77
GenerateMap()78 bool UnwindMapLocal::GenerateMap() {
79 // It's possible for the map to be regenerated while this loop is occurring.
80 // If that happens, get the map again, but only try at most three times
81 // before giving up.
82 for (int i = 0; i < 3; i++) {
83 maps_.clear();
84
85 unw_map_local_cursor_get(&map_cursor_);
86
87 unw_map_t unw_map;
88 int ret;
89 while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
90 backtrace_map_t map;
91
92 map.start = unw_map.start;
93 map.end = unw_map.end;
94 map.flags = unw_map.flags;
95 map.name = unw_map.path;
96
97 free(unw_map.path);
98
99 // The maps are in descending order, but we want them in ascending order.
100 maps_.push_front(map);
101 }
102 // Check to see if the map changed while getting the data.
103 if (ret != -UNW_EINVAL) {
104 return true;
105 }
106 }
107
108 BACK_LOGW("Unable to generate the map.");
109 return false;
110 }
111
Build()112 bool UnwindMapLocal::Build() {
113 return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
114 }
115
Find(uintptr_t addr)116 const backtrace_map_t* UnwindMapLocal::Find(uintptr_t addr) {
117 const backtrace_map_t* map = BacktraceMap::Find(addr);
118 if (!map) {
119 // Check to see if the underlying map changed and regenerate the map
120 // if it did.
121 if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
122 if (GenerateMap()) {
123 map = BacktraceMap::Find(addr);
124 }
125 }
126 }
127 return map;
128 }
129
130 //-------------------------------------------------------------------------
131 // BacktraceMap create function.
132 //-------------------------------------------------------------------------
Create(pid_t pid,bool uncached)133 BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
134 BacktraceMap* map;
135
136 if (uncached) {
137 // Force use of the base class to parse the maps when this call is made.
138 map = new BacktraceMap(pid);
139 } else if (pid == getpid()) {
140 map = new UnwindMapLocal();
141 } else {
142 map = new UnwindMap(pid);
143 }
144 if (!map->Build()) {
145 delete map;
146 return NULL;
147 }
148 return map;
149 }
150