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 <demangle.h>
40
41 #include "MapData.h"
42 #include "backtrace.h"
43 #include "debug_log.h"
44
45 #if defined(__LP64__)
46 #define PAD_PTR "016" PRIxPTR
47 #else
48 #define PAD_PTR "08" PRIxPTR
49 #endif
50
51 typedef struct _Unwind_Context __unwind_context;
52
53 extern "C" char* __cxa_demangle(const char*, char*, size_t*, int*);
54
55 static MapData g_map_data;
56 static const MapEntry* g_current_code_map = nullptr;
57
find_current_map(__unwind_context * context,void *)58 static _Unwind_Reason_Code find_current_map(__unwind_context* context, void*) {
59 uintptr_t ip = _Unwind_GetIP(context);
60
61 if (ip == 0) {
62 return _URC_END_OF_STACK;
63 }
64 g_current_code_map = g_map_data.find(ip);
65 return _URC_END_OF_STACK;
66 }
67
backtrace_startup()68 void backtrace_startup() {
69 _Unwind_Backtrace(find_current_map, nullptr);
70 }
71
backtrace_shutdown()72 void backtrace_shutdown() {}
73
74 struct stack_crawl_state_t {
75 uintptr_t* frames;
76 size_t frame_count;
77 size_t cur_frame = 0;
78
stack_crawl_state_tstack_crawl_state_t79 stack_crawl_state_t(uintptr_t* frames, size_t frame_count)
80 : frames(frames), frame_count(frame_count) {}
81 };
82
trace_function(__unwind_context * context,void * arg)83 static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg) {
84 stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
85
86 uintptr_t ip = _Unwind_GetIP(context);
87
88 // The instruction pointer is pointing at the instruction after the return
89 // call on all architectures.
90 // Modify the pc to point at the real function.
91 if (ip != 0) {
92 #if defined(__arm__)
93 // If the ip is suspiciously low, do nothing to avoid a segfault trying
94 // to access this memory.
95 if (ip >= 4096) {
96 // Check bits [15:11] of the first halfword assuming the instruction
97 // is 32 bits long. If the bits are any of these values, then our
98 // assumption was correct:
99 // b11101
100 // b11110
101 // b11111
102 // Otherwise, this is a 16 bit instruction.
103 uint16_t value = (*reinterpret_cast<uint16_t*>(ip - 2)) >> 11;
104 if (value == 0x1f || value == 0x1e || value == 0x1d) {
105 ip -= 4;
106 } else {
107 ip -= 2;
108 }
109 }
110 #elif defined(__aarch64__)
111 // All instructions are 4 bytes long, skip back one instruction.
112 ip -= 4;
113 #elif defined(__i386__) || defined(__x86_64__)
114 // It's difficult to decode exactly where the previous instruction is,
115 // so subtract 1 to estimate where the instruction lives.
116 ip--;
117 #endif
118
119 // Do not record the frames that fall in our own shared library.
120 if (g_current_code_map && (ip >= g_current_code_map->start) && ip < g_current_code_map->end) {
121 return _URC_NO_REASON;
122 }
123 }
124
125 state->frames[state->cur_frame++] = ip;
126 return (state->cur_frame >= state->frame_count) ? _URC_END_OF_STACK : _URC_NO_REASON;
127 }
128
backtrace_get(uintptr_t * frames,size_t frame_count)129 size_t backtrace_get(uintptr_t* frames, size_t frame_count) {
130 stack_crawl_state_t state(frames, frame_count);
131 _Unwind_Backtrace(trace_function, &state);
132 return state.cur_frame;
133 }
134
backtrace_string(const uintptr_t * frames,size_t frame_count)135 std::string backtrace_string(const uintptr_t* frames, size_t frame_count) {
136 std::string str;
137
138 for (size_t frame_num = 0; frame_num < frame_count; frame_num++) {
139 uintptr_t offset = 0;
140 const char* symbol = nullptr;
141
142 Dl_info info;
143 if (dladdr(reinterpret_cast<void*>(frames[frame_num]), &info) != 0) {
144 offset = reinterpret_cast<uintptr_t>(info.dli_saddr);
145 symbol = info.dli_sname;
146 } else {
147 info.dli_fname = nullptr;
148 }
149
150 uintptr_t rel_pc = offset;
151 const MapEntry* entry = g_map_data.find(frames[frame_num], &rel_pc);
152
153 const char* soname = (entry != nullptr) ? entry->name.c_str() : info.dli_fname;
154 if (soname == nullptr) {
155 soname = "<unknown>";
156 }
157
158 char offset_buf[128];
159 if (entry != nullptr && entry->offset != 0) {
160 snprintf(offset_buf, sizeof(offset_buf), " (offset 0x%" PRIxPTR ")", entry->offset);
161 } else {
162 offset_buf[0] = '\0';
163 }
164
165 char buf[1024];
166 if (symbol != nullptr) {
167 async_safe_format_buffer(buf, sizeof(buf),
168 " #%02zd pc %" PAD_PTR " %s%s (%s+%" PRIuPTR ")\n",
169 frame_num, rel_pc, soname, offset_buf, demangle(symbol).c_str(),
170 frames[frame_num] - offset);
171 } else {
172 async_safe_format_buffer(buf, sizeof(buf), " #%02zd pc %" PAD_PTR " %s%s\n",
173 frame_num, rel_pc, soname, offset_buf);
174 }
175 str += buf;
176 }
177
178 return str;
179 }
180
backtrace_log(const uintptr_t * frames,size_t frame_count)181 void backtrace_log(const uintptr_t* frames, size_t frame_count) {
182 error_log_string(backtrace_string(frames, frame_count).c_str());
183 }
184