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 //-------------------------------------------------------------------------
UnwindMap(pid_t pid)35 UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
36 unw_map_cursor_clear(&map_cursor_);
37 }
38
UnwindMapRemote(pid_t pid)39 UnwindMapRemote::UnwindMapRemote(pid_t pid) : UnwindMap(pid) {
40 }
41
~UnwindMapRemote()42 UnwindMapRemote::~UnwindMapRemote() {
43 unw_map_cursor_destroy(&map_cursor_);
44 unw_map_cursor_clear(&map_cursor_);
45 }
46
GenerateMap()47 bool UnwindMapRemote::GenerateMap() {
48 // Use the map_cursor information to construct the BacktraceMap data
49 // rather than reparsing /proc/self/maps.
50 unw_map_cursor_reset(&map_cursor_);
51
52 unw_map_t unw_map;
53 while (unw_map_cursor_get_next(&map_cursor_, &unw_map)) {
54 backtrace_map_t map;
55
56 map.start = unw_map.start;
57 map.end = unw_map.end;
58 map.offset = unw_map.offset;
59 map.load_base = unw_map.load_base;
60 map.flags = unw_map.flags;
61 map.name = unw_map.path;
62
63 // The maps are in descending order, but we want them in ascending order.
64 maps_.push_front(map);
65 }
66
67 return true;
68 }
69
Build()70 bool UnwindMapRemote::Build() {
71 return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
72 }
73
UnwindMapLocal()74 UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
75 }
76
~UnwindMapLocal()77 UnwindMapLocal::~UnwindMapLocal() {
78 if (map_created_) {
79 unw_map_local_destroy();
80 unw_map_cursor_clear(&map_cursor_);
81 }
82 }
83
GenerateMap()84 bool UnwindMapLocal::GenerateMap() {
85 // It's possible for the map to be regenerated while this loop is occurring.
86 // If that happens, get the map again, but only try at most three times
87 // before giving up.
88 for (int i = 0; i < 3; i++) {
89 maps_.clear();
90
91 // Save the map data retrieved so we can tell if it changes.
92 unw_map_local_cursor_get(&map_cursor_);
93
94 unw_map_t unw_map;
95 int ret;
96 while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
97 backtrace_map_t map;
98
99 map.start = unw_map.start;
100 map.end = unw_map.end;
101 map.offset = unw_map.offset;
102 map.load_base = unw_map.load_base;
103 map.flags = unw_map.flags;
104 map.name = unw_map.path;
105
106 free(unw_map.path);
107
108 // The maps are in descending order, but we want them in ascending order.
109 maps_.push_front(map);
110 }
111 // Check to see if the map changed while getting the data.
112 if (ret != -UNW_EINVAL) {
113 return true;
114 }
115 }
116
117 BACK_LOGW("Unable to generate the map.");
118 return false;
119 }
120
Build()121 bool UnwindMapLocal::Build() {
122 return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
123 }
124
FillIn(uintptr_t addr,backtrace_map_t * map)125 void UnwindMapLocal::FillIn(uintptr_t addr, backtrace_map_t* map) {
126 BacktraceMap::FillIn(addr, map);
127 if (!IsValid(*map)) {
128 // Check to see if the underlying map changed and regenerate the map
129 // if it did.
130 if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
131 if (GenerateMap()) {
132 BacktraceMap::FillIn(addr, map);
133 }
134 }
135 }
136 }
137
138 //-------------------------------------------------------------------------
139 // BacktraceMap create function.
140 //-------------------------------------------------------------------------
Create(pid_t pid,bool uncached)141 BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
142 BacktraceMap* map;
143
144 if (uncached) {
145 // Force use of the base class to parse the maps when this call is made.
146 map = new BacktraceMap(pid);
147 } else if (pid == getpid()) {
148 map = new UnwindMapLocal();
149 } else {
150 map = new UnwindMapRemote(pid);
151 }
152 if (!map->Build()) {
153 delete map;
154 return nullptr;
155 }
156 return map;
157 }
158