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 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 68 void backtrace_startup() { 69 _Unwind_Backtrace(find_current_map, nullptr); 70 } 71 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 79 stack_crawl_state_t(uintptr_t* frames, size_t frame_count) 80 : frames(frames), frame_count(frame_count) {} 81 }; 82 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 } 128 129 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 } 134 135 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->elf_start_offset != 0) { 160 snprintf(offset_buf, sizeof(offset_buf), " (offset 0x%" PRIxPTR ")", entry->elf_start_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 } 180 181 void backtrace_log(const uintptr_t* frames, size_t frame_count) { 182 error_log_string(backtrace_string(frames, frame_count).c_str()); 183 } 184
