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      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 <stdlib.h>
     25 #include <sys/ptrace.h>
     26 #include <cutils/log.h>
     27 
     28 static const uint32_t ELF_MAGIC = 0x464C457f; // "ELF\0177"
     29 
     30 #ifndef PAGE_SIZE
     31 #define PAGE_SIZE 4096
     32 #endif
     33 
     34 #ifndef PAGE_MASK
     35 #define PAGE_MASK (~(PAGE_SIZE - 1))
     36 #endif
     37 
     38 void init_memory(memory_t* memory, const map_info_t* map_info_list) {
     39     memory->tid = -1;
     40     memory->map_info_list = map_info_list;
     41 }
     42 
     43 void init_memory_ptrace(memory_t* memory, pid_t tid) {
     44     memory->tid = tid;
     45     memory->map_info_list = NULL;
     46 }
     47 
     48 bool try_get_word(const memory_t* memory, uintptr_t ptr, uint32_t* out_value) {
     49     ALOGV("try_get_word: reading word at 0x%08x", ptr);
     50     if (ptr & 3) {
     51         ALOGV("try_get_word: invalid pointer 0x%08x", ptr);
     52         *out_value = 0xffffffffL;
     53         return false;
     54     }
     55     if (memory->tid < 0) {
     56         if (!is_readable_map(memory->map_info_list, ptr)) {
     57             ALOGV("try_get_word: pointer 0x%08x not in a readable map", ptr);
     58             *out_value = 0xffffffffL;
     59             return false;
     60         }
     61         *out_value = *(uint32_t*)ptr;
     62         return true;
     63     } else {
     64         // ptrace() returns -1 and sets errno when the operation fails.
     65         // To disambiguate -1 from a valid result, we clear errno beforehand.
     66         errno = 0;
     67         *out_value = ptrace(PTRACE_PEEKTEXT, memory->tid, (void*)ptr, NULL);
     68         if (*out_value == 0xffffffffL && errno) {
     69             ALOGV("try_get_word: invalid pointer 0x%08x reading from tid %d, "
     70                     "ptrace() errno=%d", ptr, memory->tid, errno);
     71             return false;
     72         }
     73         return true;
     74     }
     75 }
     76 
     77 bool try_get_word_ptrace(pid_t tid, uintptr_t ptr, uint32_t* out_value) {
     78     memory_t memory;
     79     init_memory_ptrace(&memory, tid);
     80     return try_get_word(&memory, ptr, out_value);
     81 }
     82 
     83 static void load_ptrace_map_info_data(pid_t pid, map_info_t* mi) {
     84     if (mi->is_executable && mi->is_readable) {
     85         uint32_t elf_magic;
     86         if (try_get_word_ptrace(pid, mi->start, &elf_magic) && elf_magic == ELF_MAGIC) {
     87             map_info_data_t* data = (map_info_data_t*)calloc(1, sizeof(map_info_data_t));
     88             if (data) {
     89                 mi->data = data;
     90                 if (mi->name[0]) {
     91                     data->symbol_table = load_symbol_table(mi->name);
     92                 }
     93 #ifdef CORKSCREW_HAVE_ARCH
     94                 load_ptrace_map_info_data_arch(pid, mi, data);
     95 #endif
     96             }
     97         }
     98     }
     99 }
    100 
    101 ptrace_context_t* load_ptrace_context(pid_t pid) {
    102     ptrace_context_t* context =
    103             (ptrace_context_t*)calloc(1, sizeof(ptrace_context_t));
    104     if (context) {
    105         context->map_info_list = load_map_info_list(pid);
    106         for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) {
    107             load_ptrace_map_info_data(pid, mi);
    108         }
    109     }
    110     return context;
    111 }
    112 
    113 static void free_ptrace_map_info_data(map_info_t* mi) {
    114     map_info_data_t* data = (map_info_data_t*)mi->data;
    115     if (data) {
    116         if (data->symbol_table) {
    117             free_symbol_table(data->symbol_table);
    118         }
    119 #ifdef CORKSCREW_HAVE_ARCH
    120         free_ptrace_map_info_data_arch(mi, data);
    121 #endif
    122         free(data);
    123         mi->data = NULL;
    124     }
    125 }
    126 
    127 void free_ptrace_context(ptrace_context_t* context) {
    128     for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) {
    129         free_ptrace_map_info_data(mi);
    130     }
    131     free_map_info_list(context->map_info_list);
    132 }
    133 
    134 void find_symbol_ptrace(const ptrace_context_t* context,
    135         uintptr_t addr, const map_info_t** out_map_info, const symbol_t** out_symbol) {
    136     const map_info_t* mi = find_map_info(context->map_info_list, addr);
    137     const symbol_t* symbol = NULL;
    138     if (mi) {
    139         const map_info_data_t* data = (const map_info_data_t*)mi->data;
    140         if (data && data->symbol_table) {
    141             symbol = find_symbol(data->symbol_table, addr - mi->start);
    142         }
    143     }
    144     *out_map_info = mi;
    145     *out_symbol = symbol;
    146 }
    147