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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdint.h>
#include <string.h>
#include <sys/mman.h>
#include <string>
#include <vector>
#include <unwindstack/Global.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include <unwindstack/Memory.h>
namespace unwindstack {
Global::Global(std::shared_ptr<Memory>& memory) : memory_(memory) {}
Global::Global(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs)
: memory_(memory), search_libs_(search_libs) {}
void Global::SetArch(ArchEnum arch) {
if (arch_ == ARCH_UNKNOWN) {
arch_ = arch;
ProcessArch();
}
}
uint64_t Global::GetVariableOffset(MapInfo* info, const std::string& variable) {
if (!search_libs_.empty()) {
bool found = false;
const char* lib = basename(info->name.c_str());
for (const std::string& name : search_libs_) {
if (name == lib) {
found = true;
break;
}
}
if (!found) {
return 0;
}
}
Elf* elf = info->GetElf(memory_, arch());
uint64_t ptr;
// Find first non-empty list (libraries might be loaded multiple times).
if (elf->GetGlobalVariable(variable, &ptr) && ptr != 0) {
return ptr + info->start;
}
return 0;
}
void Global::FindAndReadVariable(Maps* maps, const char* var_str) {
std::string variable(var_str);
// When looking for global variables, do not arbitrarily search every
// readable map. Instead look for a specific pattern that must exist.
// The pattern should be a readable map, followed by a read-write
// map with a non-zero offset.
// For example:
// f0000-f1000 0 r-- /system/lib/libc.so
// f1000-f2000 1000 r-x /system/lib/libc.so
// f2000-f3000 2000 rw- /system/lib/libc.so
// This also works:
// f0000-f2000 0 r-- /system/lib/libc.so
// f2000-f3000 2000 rw- /system/lib/libc.so
MapInfo* map_start = nullptr;
for (MapInfo* info : *maps) {
if (map_start != nullptr) {
if (map_start->name == info->name) {
if (info->offset != 0 &&
(info->flags & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE)) {
uint64_t ptr = GetVariableOffset(map_start, variable);
if (ptr != 0 && ReadVariableData(ptr)) {
break;
} else {
// Failed to find the global variable, do not bother trying again.
map_start = nullptr;
}
}
} else {
map_start = nullptr;
}
}
if (map_start == nullptr && (info->flags & PROT_READ) && info->offset == 0 &&
!info->name.empty()) {
map_start = info;
}
}
}
} // namespace unwindstack
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