1 /*
2 * Copyright (C) 2012 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <ctype.h>
30 #include <elf.h>
31 #include <inttypes.h>
32 #include <link.h>
33 #include <stdio.h>
34 #include <stdlib.h>
35 #include <string.h>
36 #include <sys/mman.h>
37 #include <sys/uio.h>
38 #include <unistd.h>
39
40 #include <vector>
41
42 #include "MapData.h"
43
44 // Format of /proc/<PID>/maps:
45 // 6f000000-6f01e000 rwxp 00000000 00:0c 16389419 /system/lib/libcomposer.so
parse_line(char * line)46 static MapEntry* parse_line(char* line) {
47 uintptr_t start;
48 uintptr_t end;
49 uintptr_t offset;
50 int flags;
51 char permissions[5];
52 int name_pos;
53 if (sscanf(line, "%" PRIxPTR "-%" PRIxPTR " %4s %" PRIxPTR " %*x:%*x %*d %n", &start, &end,
54 permissions, &offset, &name_pos) < 2) {
55 return nullptr;
56 }
57
58 const char* name = line + name_pos;
59 size_t name_len = strlen(name);
60 if (name_len && name[name_len - 1] == '\n') {
61 name_len -= 1;
62 }
63
64 flags = 0;
65 if (permissions[0] == 'r') {
66 flags |= PROT_READ;
67 }
68 if (permissions[2] == 'x') {
69 flags |= PROT_EXEC;
70 }
71
72 MapEntry* entry = new MapEntry(start, end, offset, name, name_len, flags);
73 if (!(flags & PROT_READ)) {
74 // This will make sure that an unreadable map will prevent attempts to read
75 // elf data from the map.
76 entry->SetInvalid();
77 }
78 return entry;
79 }
80
Init()81 void MapEntry::Init() {
82 if (init_) {
83 return;
84 }
85 init_ = true;
86
87 uintptr_t end_addr;
88 if (__builtin_add_overflow(start_, SELFMAG, &end_addr) || end_addr >= end_) {
89 return;
90 }
91
92 ElfW(Ehdr) ehdr;
93 struct iovec src_io = {.iov_base = reinterpret_cast<void*>(start_), .iov_len = SELFMAG};
94 struct iovec dst_io = {.iov_base = ehdr.e_ident, .iov_len = SELFMAG};
95 ssize_t rc = process_vm_readv(getpid(), &dst_io, 1, &src_io, 1, 0);
96 valid_ = rc == SELFMAG && IS_ELF(ehdr);
97 }
98
GetLoadBias()99 uintptr_t MapEntry::GetLoadBias() {
100 if (!valid_) {
101 return 0;
102 }
103
104 if (load_bias_read_) {
105 return load_bias_;
106 }
107
108 load_bias_read_ = true;
109
110 ElfW(Ehdr) ehdr;
111 struct iovec src_io = {.iov_base = reinterpret_cast<void*>(start_), .iov_len = sizeof(ehdr)};
112 struct iovec dst_io = {.iov_base = &ehdr, .iov_len = sizeof(ehdr)};
113 ssize_t rc = process_vm_readv(getpid(), &dst_io, 1, &src_io, 1, 0);
114 if (rc != sizeof(ehdr)) {
115 return 0;
116 }
117
118 uintptr_t addr = start_ + ehdr.e_phoff;
119 for (size_t i = 0; i < ehdr.e_phnum; i++) {
120 ElfW(Phdr) phdr;
121
122 src_io.iov_base = reinterpret_cast<void*>(addr);
123 src_io.iov_len = sizeof(phdr);
124 dst_io.iov_base = &phdr;
125 dst_io.iov_len = sizeof(phdr);
126 rc = process_vm_readv(getpid(), &dst_io, 1, &src_io, 1, 0);
127 if (rc != sizeof(phdr)) {
128 return 0;
129 }
130 if ((phdr.p_type == PT_LOAD) && (phdr.p_flags & PF_X) ) {
131 load_bias_ = phdr.p_vaddr - phdr.p_offset;
132 return load_bias_;
133 }
134 addr += sizeof(phdr);
135 }
136 return 0;
137 }
138
ReadMaps()139 void MapData::ReadMaps() {
140 std::lock_guard<std::mutex> lock(m_);
141 FILE* fp = fopen("/proc/self/maps", "re");
142 if (fp == nullptr) {
143 return;
144 }
145
146 ClearEntries();
147
148 std::vector<char> buffer(1024);
149 while (fgets(buffer.data(), buffer.size(), fp) != nullptr) {
150 MapEntry* entry = parse_line(buffer.data());
151 if (entry == nullptr) {
152 break;
153 }
154 entries_.insert(entry);
155 }
156 fclose(fp);
157 }
158
ClearEntries()159 void MapData::ClearEntries() {
160 for (auto* entry : entries_) {
161 delete entry;
162 }
163 entries_.clear();
164 }
165
~MapData()166 MapData::~MapData() {
167 ClearEntries();
168 }
169
170 // Find the containing map info for the PC.
find(uintptr_t pc,uintptr_t * rel_pc)171 const MapEntry* MapData::find(uintptr_t pc, uintptr_t* rel_pc) {
172 MapEntry pc_entry(pc);
173
174 std::lock_guard<std::mutex> lock(m_);
175 auto it = entries_.find(&pc_entry);
176 if (it == entries_.end()) {
177 return nullptr;
178 }
179
180 MapEntry* entry = *it;
181 entry->Init();
182
183 if (rel_pc != nullptr) {
184 // Need to check to see if this is a read-execute map and the read-only
185 // map is the previous one.
186 if (!entry->valid() && it != entries_.begin()) {
187 MapEntry* prev_entry = *--it;
188 if (prev_entry->flags() == PROT_READ && prev_entry->offset() < entry->offset() &&
189 prev_entry->name() == entry->name()) {
190 prev_entry->Init();
191
192 if (prev_entry->valid()) {
193 entry->set_elf_start_offset(prev_entry->offset());
194 *rel_pc = pc - entry->start() + entry->offset() + prev_entry->GetLoadBias();
195 return entry;
196 }
197 }
198 }
199 *rel_pc = pc - entry->start() + entry->offset() + entry->GetLoadBias();
200 }
201 return entry;
202 }
203