1 /*
2 * Copyright (C) 2012 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <dlfcn.h>
30 #include <errno.h>
31 #include <inttypes.h>
32 #include <malloc.h>
33 #include <pthread.h>
34 #include <string.h>
35 #include <sys/types.h>
36 #include <unistd.h>
37 #include <unwind.h>
38
39 #include "MapData.h"
40 #include "backtrace.h"
41 #include "debug_log.h"
42
43 #if defined(__LP64__)
44 #define PAD_PTR "016" PRIxPTR
45 #else
46 #define PAD_PTR "08" PRIxPTR
47 #endif
48
49 typedef struct _Unwind_Context __unwind_context;
50
51 extern "C" char* __cxa_demangle(const char*, char*, size_t*, int*);
52
53 static MapData g_map_data;
54 static const MapEntry* g_current_code_map = nullptr;
55
find_current_map(__unwind_context * context,void *)56 static _Unwind_Reason_Code find_current_map(__unwind_context* context, void*) {
57 uintptr_t ip = _Unwind_GetIP(context);
58
59 if (ip == 0) {
60 return _URC_END_OF_STACK;
61 }
62 g_current_code_map = g_map_data.find(ip);
63 return _URC_END_OF_STACK;
64 }
65
backtrace_startup()66 void backtrace_startup() {
67 _Unwind_Backtrace(find_current_map, nullptr);
68 }
69
backtrace_shutdown()70 void backtrace_shutdown() {}
71
72 struct stack_crawl_state_t {
73 uintptr_t* frames;
74 size_t frame_count;
75 size_t cur_frame = 0;
76
stack_crawl_state_tstack_crawl_state_t77 stack_crawl_state_t(uintptr_t* frames, size_t frame_count)
78 : frames(frames), frame_count(frame_count) {}
79 };
80
trace_function(__unwind_context * context,void * arg)81 static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg) {
82 stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
83
84 uintptr_t ip = _Unwind_GetIP(context);
85
86 // The instruction pointer is pointing at the instruction after the return
87 // call on all architectures.
88 // Modify the pc to point at the real function.
89 if (ip != 0) {
90 #if defined(__arm__)
91 // If the ip is suspiciously low, do nothing to avoid a segfault trying
92 // to access this memory.
93 if (ip >= 4096) {
94 // Check bits [15:11] of the first halfword assuming the instruction
95 // is 32 bits long. If the bits are any of these values, then our
96 // assumption was correct:
97 // b11101
98 // b11110
99 // b11111
100 // Otherwise, this is a 16 bit instruction.
101 uint16_t value = (*reinterpret_cast<uint16_t*>(ip - 2)) >> 11;
102 if (value == 0x1f || value == 0x1e || value == 0x1d) {
103 ip -= 4;
104 } else {
105 ip -= 2;
106 }
107 }
108 #elif defined(__aarch64__)
109 // All instructions are 4 bytes long, skip back one instruction.
110 ip -= 4;
111 #elif defined(__i386__) || defined(__x86_64__)
112 // It's difficult to decode exactly where the previous instruction is,
113 // so subtract 1 to estimate where the instruction lives.
114 ip--;
115 #endif
116
117 // Do not record the frames that fall in our own shared library.
118 if (g_current_code_map && (ip >= g_current_code_map->start) && ip < g_current_code_map->end) {
119 return _URC_NO_REASON;
120 }
121 }
122
123 state->frames[state->cur_frame++] = ip;
124 return (state->cur_frame >= state->frame_count) ? _URC_END_OF_STACK : _URC_NO_REASON;
125 }
126
backtrace_get(uintptr_t * frames,size_t frame_count)127 size_t backtrace_get(uintptr_t* frames, size_t frame_count) {
128 stack_crawl_state_t state(frames, frame_count);
129 _Unwind_Backtrace(trace_function, &state);
130 return state.cur_frame;
131 }
132
backtrace_string(const uintptr_t * frames,size_t frame_count)133 std::string backtrace_string(const uintptr_t* frames, size_t frame_count) {
134 std::string str;
135
136 for (size_t frame_num = 0; frame_num < frame_count; frame_num++) {
137 uintptr_t offset = 0;
138 const char* symbol = nullptr;
139
140 Dl_info info;
141 if (dladdr(reinterpret_cast<void*>(frames[frame_num]), &info) != 0) {
142 offset = reinterpret_cast<uintptr_t>(info.dli_saddr);
143 symbol = info.dli_sname;
144 } else {
145 info.dli_fname = nullptr;
146 }
147
148 uintptr_t rel_pc = offset;
149 const MapEntry* entry = g_map_data.find(frames[frame_num], &rel_pc);
150
151 const char* soname = (entry != nullptr) ? entry->name.c_str() : info.dli_fname;
152 if (soname == nullptr) {
153 soname = "<unknown>";
154 }
155
156 char offset_buf[128];
157 if (entry != nullptr && entry->elf_start_offset != 0) {
158 snprintf(offset_buf, sizeof(offset_buf), " (offset 0x%" PRIxPTR ")", entry->elf_start_offset);
159 } else {
160 offset_buf[0] = '\0';
161 }
162
163 char buf[1024];
164 if (symbol != nullptr) {
165 char* demangled_name = __cxa_demangle(symbol, nullptr, nullptr, nullptr);
166 const char* name;
167 if (demangled_name != nullptr) {
168 name = demangled_name;
169 } else {
170 name = symbol;
171 }
172 async_safe_format_buffer(buf, sizeof(buf),
173 " #%02zd pc %" PAD_PTR " %s%s (%s+%" PRIuPTR ")\n",
174 frame_num, rel_pc, soname, offset_buf, name,
175 frames[frame_num] - offset);
176 free(demangled_name);
177 } else {
178 async_safe_format_buffer(buf, sizeof(buf), " #%02zd pc %" PAD_PTR " %s%s\n",
179 frame_num, rel_pc, soname, offset_buf);
180 }
181 str += buf;
182 }
183
184 return str;
185 }
186
backtrace_log(const uintptr_t * frames,size_t frame_count)187 void backtrace_log(const uintptr_t* frames, size_t frame_count) {
188 error_log_string(backtrace_string(frames, frame_count).c_str());
189 }
190