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 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 66 void backtrace_startup() { 67 _Unwind_Backtrace(find_current_map, nullptr); 68 } 69 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 78 stack_crawl_state_t(uintptr_t* frames, size_t frame_count) 79 : frames(frames), frame_count(frame_count) {} 80 }; 81 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 } 127 128 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 } 133 134 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 } else { 146 info.dli_fname = nullptr; 147 } 148 149 uintptr_t rel_pc = offset; 150 const MapEntry* entry = g_map_data.find(frames[frame_num], &rel_pc); 151 152 const char* soname = (entry != nullptr) ? entry->name.c_str() : info.dli_fname; 153 if (soname == nullptr) { 154 soname = "<unknown>"; 155 } 156 char buf[1024]; 157 if (symbol != nullptr) { 158 char* demangled_symbol = __cxa_demangle(symbol, nullptr, nullptr, nullptr); 159 const char* best_name = (demangled_symbol != nullptr) ? demangled_symbol : symbol; 160 161 __libc_format_buffer(buf, sizeof(buf), 162 " #%02zd pc %" PAD_PTR " %s (%s+%" PRIuPTR ")\n", frame_num, 163 rel_pc, soname, best_name, frames[frame_num] - offset); 164 free(demangled_symbol); 165 } else { 166 __libc_format_buffer(buf, sizeof(buf), 167 " #%02zd pc %" PAD_PTR " %s\n", frame_num, rel_pc, soname); 168 } 169 str += buf; 170 } 171 172 return str; 173 } 174 175 void backtrace_log(const uintptr_t* frames, size_t frame_count) { 176 error_log_string(backtrace_string(frames, frame_count).c_str()); 177 } 178
