1 /*
2 * Copyright (C) 2018 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 #include <stdint.h>
18 #include <string.h>
19 #include <sys/mman.h>
20
21 #include <string>
22 #include <vector>
23
24 #include <android-base/file.h>
25
26 #include <unwindstack/Global.h>
27 #include <unwindstack/MapInfo.h>
28 #include <unwindstack/Maps.h>
29 #include <unwindstack/Memory.h>
30
31 namespace unwindstack {
32
Global(std::shared_ptr<Memory> & memory)33 Global::Global(std::shared_ptr<Memory>& memory) : memory_(memory) {}
Global(std::shared_ptr<Memory> & memory,std::vector<std::string> & search_libs)34 Global::Global(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs)
35 : memory_(memory), search_libs_(search_libs) {}
36
SetArch(ArchEnum arch)37 void Global::SetArch(ArchEnum arch) {
38 if (arch_ == ARCH_UNKNOWN) {
39 arch_ = arch;
40 ProcessArch();
41 }
42 }
43
Searchable(const std::string & name)44 bool Global::Searchable(const std::string& name) {
45 if (search_libs_.empty()) {
46 return true;
47 }
48
49 if (name.empty()) {
50 return false;
51 }
52
53 std::string base_name = android::base::Basename(name);
54 for (const std::string& lib : search_libs_) {
55 if (base_name == lib) {
56 return true;
57 }
58 }
59 return false;
60 }
61
FindAndReadVariable(Maps * maps,const char * var_str)62 void Global::FindAndReadVariable(Maps* maps, const char* var_str) {
63 std::string variable(var_str);
64 // When looking for global variables, do not arbitrarily search every
65 // readable map. Instead look for a specific pattern that must exist.
66 // The pattern should be a readable map, followed by a read-write
67 // map with a non-zero offset.
68 // For example:
69 // f0000-f1000 0 r-- /system/lib/libc.so
70 // f1000-f2000 1000 r-x /system/lib/libc.so
71 // f2000-f3000 2000 rw- /system/lib/libc.so
72 // This also works:
73 // f0000-f2000 0 r-- /system/lib/libc.so
74 // f2000-f3000 2000 rw- /system/lib/libc.so
75 // It is also possible to see empty maps after the read-only like so:
76 // f0000-f1000 0 r-- /system/lib/libc.so
77 // f1000-f2000 0 ---
78 // f2000-f3000 1000 r-x /system/lib/libc.so
79 // f3000-f4000 2000 rw- /system/lib/libc.so
80 MapInfo* map_zero = nullptr;
81 for (const auto& info : *maps) {
82 if ((info->flags() & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE) &&
83 map_zero != nullptr && Searchable(info->name()) && info->name() == map_zero->name()) {
84 Elf* elf = map_zero->GetElf(memory_, arch());
85 uint64_t ptr;
86 if (elf->GetGlobalVariableOffset(variable, &ptr) && ptr != 0) {
87 uint64_t offset_end = info->offset() + info->end() - info->start();
88 if (ptr >= info->offset() && ptr < offset_end) {
89 ptr = info->start() + ptr - info->offset();
90 if (ReadVariableData(ptr)) {
91 break;
92 }
93 }
94 }
95 } else if (info->offset() == 0 && !info->name().empty()) {
96 map_zero = info.get();
97 }
98 }
99 }
100
101 } // namespace unwindstack
102