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 <unwindstack/Global.h>
25 #include <unwindstack/MapInfo.h>
26 #include <unwindstack/Maps.h>
27 #include <unwindstack/Memory.h>
28
29 namespace unwindstack {
30
Global(std::shared_ptr<Memory> & memory)31 Global::Global(std::shared_ptr<Memory>& memory) : memory_(memory) {}
Global(std::shared_ptr<Memory> & memory,std::vector<std::string> & search_libs)32 Global::Global(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs)
33 : memory_(memory), search_libs_(search_libs) {}
34
SetArch(ArchEnum arch)35 void Global::SetArch(ArchEnum arch) {
36 if (arch_ == ARCH_UNKNOWN) {
37 arch_ = arch;
38 ProcessArch();
39 }
40 }
41
GetVariableOffset(MapInfo * info,const std::string & variable)42 uint64_t Global::GetVariableOffset(MapInfo* info, const std::string& variable) {
43 if (!search_libs_.empty()) {
44 bool found = false;
45 const char* lib = basename(info->name.c_str());
46 for (const std::string& name : search_libs_) {
47 if (name == lib) {
48 found = true;
49 break;
50 }
51 }
52 if (!found) {
53 return 0;
54 }
55 }
56
57 Elf* elf = info->GetElf(memory_, arch());
58 uint64_t ptr;
59 // Find first non-empty list (libraries might be loaded multiple times).
60 if (elf->GetGlobalVariable(variable, &ptr) && ptr != 0) {
61 return ptr + info->start;
62 }
63 return 0;
64 }
65
FindAndReadVariable(Maps * maps,const char * var_str)66 void Global::FindAndReadVariable(Maps* maps, const char* var_str) {
67 std::string variable(var_str);
68 // When looking for global variables, do not arbitrarily search every
69 // readable map. Instead look for a specific pattern that must exist.
70 // The pattern should be a readable map, followed by a read-write
71 // map with a non-zero offset.
72 // For example:
73 // f0000-f1000 0 r-- /system/lib/libc.so
74 // f1000-f2000 1000 r-x /system/lib/libc.so
75 // f2000-f3000 2000 rw- /system/lib/libc.so
76 // This also works:
77 // f0000-f2000 0 r-- /system/lib/libc.so
78 // f2000-f3000 2000 rw- /system/lib/libc.so
79 MapInfo* map_start = nullptr;
80 for (const auto& info : *maps) {
81 if (map_start != nullptr) {
82 if (map_start->name == info->name) {
83 if (info->offset != 0 &&
84 (info->flags & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE)) {
85 uint64_t ptr = GetVariableOffset(map_start, variable);
86 if (ptr != 0 && ReadVariableData(ptr)) {
87 break;
88 } else {
89 // Failed to find the global variable, do not bother trying again.
90 map_start = nullptr;
91 }
92 }
93 } else {
94 map_start = nullptr;
95 }
96 }
97 if (map_start == nullptr && (info->flags & PROT_READ) && info->offset == 0 &&
98 !info->name.empty()) {
99 map_start = info.get();
100 }
101 }
102 }
103
104 } // namespace unwindstack
105