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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 %p", (void*) ptr);
     50     if (ptr & 3) {
     51         ALOGV("try_get_word: invalid pointer %p", (void*) 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 %p not in a readable map", (void*) ptr);
     58             *out_value = 0xffffffffL;
     59             return false;
     60         }
     61         *out_value = *(uint32_t*)ptr;
     62         return true;
     63     } else {
     64 #if defined(__APPLE__)
     65         ALOGV("no ptrace on Mac OS");
     66         return false;
     67 #else
     68         // ptrace() returns -1 and sets errno when the operation fails.
     69         // To disambiguate -1 from a valid result, we clear errno beforehand.
     70         errno = 0;
     71         *out_value = ptrace(PTRACE_PEEKTEXT, memory->tid, (void*)ptr, NULL);
     72         if (*out_value == 0xffffffffL && errno) {
     73             ALOGV("try_get_word: invalid pointer 0x%08x reading from tid %d, "
     74                     "ptrace() errno=%d", ptr, memory->tid, errno);
     75             return false;
     76         }
     77         return true;
     78 #endif
     79     }
     80 }
     81 
     82 bool try_get_word_ptrace(pid_t tid, uintptr_t ptr, uint32_t* out_value) {
     83     memory_t memory;
     84     init_memory_ptrace(&memory, tid);
     85     return try_get_word(&memory, ptr, out_value);
     86 }
     87 
     88 static void load_ptrace_map_info_data(pid_t pid, map_info_t* mi) {
     89     if (mi->is_executable && mi->is_readable) {
     90         uint32_t elf_magic;
     91         if (try_get_word_ptrace(pid, mi->start, &elf_magic) && elf_magic == ELF_MAGIC) {
     92             map_info_data_t* data = (map_info_data_t*)calloc(1, sizeof(map_info_data_t));
     93             if (data) {
     94                 mi->data = data;
     95                 if (mi->name[0]) {
     96                     data->symbol_table = load_symbol_table(mi->name);
     97                 }
     98 #ifdef CORKSCREW_HAVE_ARCH
     99                 load_ptrace_map_info_data_arch(pid, mi, data);
    100 #endif
    101             }
    102         }
    103     }
    104 }
    105 
    106 ptrace_context_t* load_ptrace_context(pid_t pid) {
    107     ptrace_context_t* context =
    108             (ptrace_context_t*)calloc(1, sizeof(ptrace_context_t));
    109     if (context) {
    110         context->map_info_list = load_map_info_list(pid);
    111         for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) {
    112             load_ptrace_map_info_data(pid, mi);
    113         }
    114     }
    115     return context;
    116 }
    117 
    118 static void free_ptrace_map_info_data(map_info_t* mi) {
    119     map_info_data_t* data = (map_info_data_t*)mi->data;
    120     if (data) {
    121         if (data->symbol_table) {
    122             free_symbol_table(data->symbol_table);
    123         }
    124 #ifdef CORKSCREW_HAVE_ARCH
    125         free_ptrace_map_info_data_arch(mi, data);
    126 #endif
    127         free(data);
    128         mi->data = NULL;
    129     }
    130 }
    131 
    132 void free_ptrace_context(ptrace_context_t* context) {
    133     for (map_info_t* mi = context->map_info_list; mi; mi = mi->next) {
    134         free_ptrace_map_info_data(mi);
    135     }
    136     free_map_info_list(context->map_info_list);
    137     free(context);
    138 }
    139 
    140 void find_symbol_ptrace(const ptrace_context_t* context,
    141         uintptr_t addr, const map_info_t** out_map_info, const symbol_t** out_symbol) {
    142     const map_info_t* mi = find_map_info(context->map_info_list, addr);
    143     const symbol_t* symbol = NULL;
    144     if (mi) {
    145         const map_info_data_t* data = (const map_info_data_t*)mi->data;
    146         if (data && data->symbol_table) {
    147             symbol = find_symbol(data->symbol_table, addr - mi->start);
    148         }
    149     }
    150     *out_map_info = mi;
    151     *out_symbol = symbol;
    152 }
    153