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 "backtrace.h"
40 #include "debug_log.h"
41 #include "MapData.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
73 struct stack_crawl_state_t {
74 uintptr_t* frames;
75 size_t frame_count;
76 size_t cur_frame = 0;
77
stack_crawl_state_tstack_crawl_state_t78 stack_crawl_state_t(uintptr_t* frames, size_t frame_count)
79 : frames(frames), frame_count(frame_count) {}
80 };
81
trace_function(__unwind_context * context,void * arg)82 static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg) {
83 stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
84
85 uintptr_t ip = _Unwind_GetIP(context);
86
87 // The instruction pointer is pointing at the instruction after the return
88 // call on all architectures.
89 // Modify the pc to point at the real function.
90 if (ip != 0) {
91 #if defined(__arm__)
92 // If the ip is suspiciously low, do nothing to avoid a segfault trying
93 // to access this memory.
94 if (ip >= 4096) {
95 // Check bits [15:11] of the first halfword assuming the instruction
96 // is 32 bits long. If the bits are any of these values, then our
97 // assumption was correct:
98 // b11101
99 // b11110
100 // b11111
101 // Otherwise, this is a 16 bit instruction.
102 uint16_t value = (*reinterpret_cast<uint16_t*>(ip - 2)) >> 11;
103 if (value == 0x1f || value == 0x1e || value == 0x1d) {
104 ip -= 4;
105 } else {
106 ip -= 2;
107 }
108 }
109 #elif defined(__aarch64__)
110 // All instructions are 4 bytes long, skip back one instruction.
111 ip -= 4;
112 #elif defined(__i386__) || defined(__x86_64__)
113 // It's difficult to decode exactly where the previous instruction is,
114 // so subtract 1 to estimate where the instruction lives.
115 ip--;
116 #endif
117
118 // Do not record the frames that fall in our own shared library.
119 if (g_current_code_map && (ip >= g_current_code_map->start) && ip < g_current_code_map->end) {
120 return _URC_NO_REASON;
121 }
122 }
123
124 state->frames[state->cur_frame++] = ip;
125 return (state->cur_frame >= state->frame_count) ? _URC_END_OF_STACK : _URC_NO_REASON;
126 }
127
backtrace_get(uintptr_t * frames,size_t frame_count)128 size_t backtrace_get(uintptr_t* frames, size_t frame_count) {
129 stack_crawl_state_t state(frames, frame_count);
130 _Unwind_Backtrace(trace_function, &state);
131 return state.cur_frame;
132 }
133
backtrace_string(const uintptr_t * frames,size_t frame_count)134 std::string backtrace_string(const uintptr_t* frames, size_t frame_count) {
135 std::string str;
136
137 for (size_t frame_num = 0; frame_num < frame_count; frame_num++) {
138 uintptr_t offset = 0;
139 const char* symbol = nullptr;
140
141 Dl_info info;
142 if (dladdr(reinterpret_cast<void*>(frames[frame_num]), &info) != 0) {
143 offset = reinterpret_cast<uintptr_t>(info.dli_saddr);
144 symbol = info.dli_sname;
145 }
146
147 uintptr_t rel_pc = offset;
148 const MapEntry* entry = g_map_data.find(frames[frame_num], &rel_pc);
149
150 const char* soname = (entry != nullptr) ? entry->name.c_str() : info.dli_fname;
151 if (soname == nullptr) {
152 soname = "<unknown>";
153 }
154 char buf[1024];
155 if (symbol != nullptr) {
156 char* demangled_symbol = __cxa_demangle(symbol, nullptr, nullptr, nullptr);
157 const char* best_name = (demangled_symbol != nullptr) ? demangled_symbol : symbol;
158
159 __libc_format_buffer(buf, sizeof(buf),
160 " #%02zd pc %" PAD_PTR " %s (%s+%" PRIuPTR ")\n", frame_num,
161 rel_pc, soname, best_name, frames[frame_num] - offset);
162 free(demangled_symbol);
163 } else {
164 __libc_format_buffer(buf, sizeof(buf),
165 " #%02zd pc %" PAD_PTR " %s\n", frame_num, rel_pc, soname);
166 }
167 str += buf;
168 }
169
170 return str;
171 }
172
backtrace_log(const uintptr_t * frames,size_t frame_count)173 void backtrace_log(const uintptr_t* frames, size_t frame_count) {
174 error_log_string(backtrace_string(frames, frame_count).c_str());
175 }
176