ptrace.c revision 501edd29b823ce1301d2effdd3a9e4b6e2b20b76
1/* 2 * Copyright (C) 2011 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#define LOG_TAG "Corkscrew" 18//#define LOG_NDEBUG 0 19 20#include "ptrace-arch.h" 21#include <corkscrew/ptrace.h> 22 23#include <errno.h> 24#include <sys/ptrace.h> 25#include <cutils/log.h> 26 27static const uint32_t ELF_MAGIC = 0x464C457f; // "ELF\0177" 28 29#ifndef PAGE_SIZE 30#define PAGE_SIZE 4096 31#endif 32 33#ifndef PAGE_MASK 34#define PAGE_MASK (~(PAGE_SIZE - 1)) 35#endif 36 37bool try_get_word(pid_t tid, uintptr_t ptr, uint32_t* out_value) { 38 if (ptr & 3) { 39 LOGV("try_get_word: invalid pointer 0x%08x", ptr); 40 *out_value = 0; 41 return false; 42 } 43 if (tid < 0) { 44#if 0 /*unreliable, unclear whether this is safe from a signal handler context*/ 45 // Determine whether the pointer is likely to be valid before dereferencing it. 46 unsigned char vec[1]; 47 while (mincore((void*)(ptr & PAGE_MASK), sizeof(uint32_t), vec)) { 48 if (errno != EAGAIN && errno != EINTR) { 49 LOGV("try_get_word: invalid pointer 0x%08x, mincore() errno=%d", ptr, errno); 50 *out_value = 0; 51 return false; 52 } 53 } 54#endif 55 *out_value = *(uint32_t*)ptr; 56 return true; 57 } else { 58 // ptrace() returns -1 and sets errno when the operation fails. 59 // To disambiguate -1 from a valid result, we clear errno beforehand. 60 errno = 0; 61 *out_value = ptrace(PTRACE_PEEKTEXT, tid, (void*)ptr, NULL); 62 if (*out_value == 0xffffffffL && errno) { 63 LOGV("try_get_word: invalid pointer 0x%08x, ptrace() errno=%d", ptr, errno); 64 *out_value = 0; 65 return false; 66 } 67 return true; 68 } 69} 70 71static void load_ptrace_map_info_data(pid_t pid, map_info_t* mi) { 72 if (mi->is_executable) { 73 uint32_t elf_magic; 74 if (try_get_word(pid, mi->start, &elf_magic) && elf_magic == ELF_MAGIC) { 75 map_info_data_t* data = (map_info_data_t*)calloc(1, sizeof(map_info_data_t)); 76 if (data) { 77 mi->data = data; 78 if (mi->name[0]) { 79 data->symbol_table = load_symbol_table(mi->name); 80 } 81#ifdef CORKSCREW_HAVE_ARCH 82 load_ptrace_map_info_data_arch(pid, mi, data); 83#endif 84 } 85 } 86 } 87} 88 89ptrace_context_t* load_ptrace_context(pid_t pid) { 90 ptrace_context_t* context = 91 (ptrace_context_t*)calloc(1, sizeof(ptrace_context_t)); 92 if (context) { 93 context->map_info_list = load_map_info_list(pid); 94 for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) { 95 load_ptrace_map_info_data(pid, mi); 96 } 97 } 98 return context; 99} 100 101static void free_ptrace_map_info_data(map_info_t* mi) { 102 map_info_data_t* data = (map_info_data_t*)mi->data; 103 if (data) { 104 if (data->symbol_table) { 105 free_symbol_table(data->symbol_table); 106 } 107#ifdef CORKSCREW_HAVE_ARCH 108 free_ptrace_map_info_data_arch(mi, data); 109#endif 110 free(data); 111 mi->data = NULL; 112 } 113} 114 115void free_ptrace_context(ptrace_context_t* context) { 116 for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) { 117 free_ptrace_map_info_data(mi); 118 } 119 free_map_info_list(context->map_info_list); 120} 121 122void find_symbol_ptrace(const ptrace_context_t* context, 123 uintptr_t addr, const map_info_t** out_map_info, const symbol_t** out_symbol) { 124 const map_info_t* mi = find_map_info(context->map_info_list, addr); 125 const symbol_t* symbol = NULL; 126 if (mi) { 127 const map_info_data_t* data = (const map_info_data_t*)mi->data; 128 if (data && data->symbol_table) { 129 symbol = find_symbol(data->symbol_table, addr - mi->start); 130 } 131 } 132 *out_map_info = mi; 133 *out_symbol = symbol; 134} 135