1 /*
2 * Copyright (C) 2013 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 <sys/types.h>
19 #include <ucontext.h>
20
21 #include <libunwind.h>
22 #include <libunwind-ptrace.h>
23
24 #include <backtrace/Backtrace.h>
25 #include <backtrace/BacktraceMap.h>
26
27 #include "BacktraceLog.h"
28 #include "UnwindMap.h"
29 #include "UnwindPtrace.h"
30
UnwindPtrace(pid_t pid,pid_t tid,BacktraceMap * map)31 UnwindPtrace::UnwindPtrace(pid_t pid, pid_t tid, BacktraceMap* map)
32 : BacktracePtrace(pid, tid, map), addr_space_(nullptr), upt_info_(nullptr) {
33 }
34
~UnwindPtrace()35 UnwindPtrace::~UnwindPtrace() {
36 if (upt_info_) {
37 _UPT_destroy(upt_info_);
38 upt_info_ = nullptr;
39 }
40
41 if (addr_space_) {
42 // Remove the map from the address space before destroying it.
43 // It will be freed in the UnwindMap destructor.
44 unw_map_set(addr_space_, nullptr);
45
46 unw_destroy_addr_space(addr_space_);
47 addr_space_ = nullptr;
48 }
49 }
50
Init()51 bool UnwindPtrace::Init() {
52 if (upt_info_) {
53 return true;
54 }
55
56 if (addr_space_) {
57 // If somehow the addr_space_ gets initialized but upt_info_ doesn't,
58 // then that indicates there is some kind of failure.
59 return false;
60 }
61
62 addr_space_ = unw_create_addr_space(&_UPT_accessors, 0);
63 if (!addr_space_) {
64 BACK_LOGW("unw_create_addr_space failed.");
65 error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
66 return false;
67 }
68
69 UnwindMap* map = static_cast<UnwindMap*>(GetMap());
70 unw_map_set(addr_space_, map->GetMapCursor());
71
72 upt_info_ = reinterpret_cast<struct UPT_info*>(_UPT_create(Tid()));
73 if (!upt_info_) {
74 BACK_LOGW("Failed to create upt info.");
75 error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
76 return false;
77 }
78
79 return true;
80 }
81
Unwind(size_t num_ignore_frames,ucontext_t * ucontext)82 bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
83 if (GetMap() == nullptr) {
84 // Without a map object, we can't do anything.
85 error_ = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
86 return false;
87 }
88
89 error_ = BACKTRACE_UNWIND_NO_ERROR;
90
91 if (ucontext) {
92 BACK_LOGW("Unwinding from a specified context not supported yet.");
93 error_ = BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION;
94 return false;
95 }
96
97 if (!Init()) {
98 return false;
99 }
100
101 unw_cursor_t cursor;
102 int ret = unw_init_remote(&cursor, addr_space_, upt_info_);
103 if (ret < 0) {
104 BACK_LOGW("unw_init_remote failed %d", ret);
105 error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
106 return false;
107 }
108
109 size_t num_frames = 0;
110 do {
111 unw_word_t pc;
112 ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);
113 if (ret < 0) {
114 BACK_LOGW("Failed to read IP %d", ret);
115 break;
116 }
117 unw_word_t sp;
118 ret = unw_get_reg(&cursor, UNW_REG_SP, &sp);
119 if (ret < 0) {
120 BACK_LOGW("Failed to read SP %d", ret);
121 break;
122 }
123
124 if (num_ignore_frames == 0) {
125 frames_.resize(num_frames+1);
126 backtrace_frame_data_t* frame = &frames_.at(num_frames);
127 frame->num = num_frames;
128 frame->pc = static_cast<uintptr_t>(pc);
129 frame->sp = static_cast<uintptr_t>(sp);
130 frame->stack_size = 0;
131
132 if (num_frames > 0) {
133 backtrace_frame_data_t* prev = &frames_.at(num_frames-1);
134 prev->stack_size = frame->sp - prev->sp;
135 }
136
137 FillInMap(frame->pc, &frame->map);
138
139 frame->func_name = GetFunctionName(frame->pc, &frame->func_offset, &frame->map);
140
141 num_frames++;
142 // If the pc is in a device map, then don't try to step.
143 if (frame->map.flags & PROT_DEVICE_MAP) {
144 break;
145 }
146 } else {
147 // If the pc is in a device map, then don't try to step.
148 backtrace_map_t map;
149 FillInMap(pc, &map);
150 if (map.flags & PROT_DEVICE_MAP) {
151 break;
152 }
153 num_ignore_frames--;
154 }
155 // Verify the sp is not in a device map.
156 backtrace_map_t map;
157 FillInMap(sp, &map);
158 if (map.flags & PROT_DEVICE_MAP) {
159 break;
160 }
161 ret = unw_step (&cursor);
162 } while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
163
164 return true;
165 }
166
GetFunctionNameRaw(uintptr_t pc,uintptr_t * offset)167 std::string UnwindPtrace::GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) {
168 if (!Init()) {
169 return "";
170 }
171
172 *offset = 0;
173 char buf[512];
174 unw_word_t value;
175 if (unw_get_proc_name_by_ip(addr_space_, pc, buf, sizeof(buf), &value,
176 upt_info_) >= 0 && buf[0] != '\0') {
177 *offset = static_cast<uintptr_t>(value);
178 return buf;
179 }
180 return "";
181 }
182