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
init_memory(memory_t * memory,const map_info_t * map_info_list)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
init_memory_ptrace(memory_t * memory,pid_t tid)43 void init_memory_ptrace(memory_t* memory, pid_t tid) {
44 memory->tid = tid;
45 memory->map_info_list = NULL;
46 }
47
try_get_word(const memory_t * memory,uintptr_t ptr,uint32_t * out_value)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
try_get_word_ptrace(pid_t tid,uintptr_t ptr,uint32_t * out_value)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
load_ptrace_map_info_data(pid_t pid,map_info_t * mi)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
load_ptrace_context(pid_t pid)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
free_ptrace_map_info_data(map_info_t * mi)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
free_ptrace_context(ptrace_context_t * context)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
find_symbol_ptrace(const ptrace_context_t * context,uintptr_t addr,const map_info_t ** out_map_info,const symbol_t ** out_symbol)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