1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <errno.h> 18 #include <stdint.h> 19 #include <string.h> 20 #include <sys/param.h> 21 #include <sys/ptrace.h> 22 #include <sys/types.h> 23 #include <ucontext.h> 24 #include <unistd.h> 25 26 #include <backtrace/Backtrace.h> 27 #include <backtrace/BacktraceMap.h> 28 29 #include "BacktraceLog.h" 30 #include "BacktracePtrace.h" 31 #include "thread_utils.h" 32 33 #if !defined(__APPLE__) 34 static bool PtraceRead(pid_t tid, uintptr_t addr, word_t* out_value) { 35 // ptrace() returns -1 and sets errno when the operation fails. 36 // To disambiguate -1 from a valid result, we clear errno beforehand. 37 errno = 0; 38 *out_value = ptrace(PTRACE_PEEKTEXT, tid, reinterpret_cast<void*>(addr), nullptr); 39 if (*out_value == static_cast<word_t>(-1) && errno) { 40 return false; 41 } 42 return true; 43 } 44 #endif 45 46 bool BacktracePtrace::ReadWord(uintptr_t ptr, word_t* out_value) { 47 #if defined(__APPLE__) 48 BACK_LOGW("MacOS does not support reading from another pid."); 49 return false; 50 #else 51 if (!VerifyReadWordArgs(ptr, out_value)) { 52 return false; 53 } 54 55 backtrace_map_t map; 56 FillInMap(ptr, &map); 57 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) { 58 return false; 59 } 60 61 return PtraceRead(Tid(), ptr, out_value); 62 #endif 63 } 64 65 size_t BacktracePtrace::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) { 66 #if defined(__APPLE__) 67 BACK_LOGW("MacOS does not support reading from another pid."); 68 return 0; 69 #else 70 backtrace_map_t map; 71 FillInMap(addr, &map); 72 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) { 73 return 0; 74 } 75 76 bytes = MIN(map.end - addr, bytes); 77 size_t bytes_read = 0; 78 word_t data_word; 79 size_t align_bytes = addr & (sizeof(word_t) - 1); 80 if (align_bytes != 0) { 81 if (!PtraceRead(Tid(), addr & ~(sizeof(word_t) - 1), &data_word)) { 82 return 0; 83 } 84 size_t copy_bytes = MIN(sizeof(word_t) - align_bytes, bytes); 85 memcpy(buffer, reinterpret_cast<uint8_t*>(&data_word) + align_bytes, copy_bytes); 86 addr += copy_bytes; 87 buffer += copy_bytes; 88 bytes -= copy_bytes; 89 bytes_read += copy_bytes; 90 } 91 92 size_t num_words = bytes / sizeof(word_t); 93 for (size_t i = 0; i < num_words; i++) { 94 if (!PtraceRead(Tid(), addr, &data_word)) { 95 return bytes_read; 96 } 97 memcpy(buffer, &data_word, sizeof(word_t)); 98 buffer += sizeof(word_t); 99 addr += sizeof(word_t); 100 bytes_read += sizeof(word_t); 101 } 102 103 size_t left_over = bytes & (sizeof(word_t) - 1); 104 if (left_over) { 105 if (!PtraceRead(Tid(), addr, &data_word)) { 106 return bytes_read; 107 } 108 memcpy(buffer, &data_word, left_over); 109 bytes_read += left_over; 110 } 111 return bytes_read; 112 #endif 113 } 114
