/* * 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 <android-base/file.h> #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(); } } bool Global::Searchable(const std::string& name) { if (search_libs_.empty()) { return true; } if (name.empty()) { return false; } std::string base_name = android::base::Basename(name); for (const std::string& lib : search_libs_) { if (base_name == lib) { return true; } } return false; } 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 // It is also possible to see empty maps after the read-only like so: // f0000-f1000 0 r-- /system/lib/libc.so // f1000-f2000 0 --- // f2000-f3000 1000 r-x /system/lib/libc.so // f3000-f4000 2000 rw- /system/lib/libc.so MapInfo* map_zero = nullptr; for (const auto& info : *maps) { if ((info->flags() & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE) && map_zero != nullptr && Searchable(info->name()) && info->name() == map_zero->name()) { Elf* elf = map_zero->GetElf(memory_, arch()); uint64_t ptr; if (elf->GetGlobalVariableOffset(variable, &ptr) && ptr != 0) { uint64_t offset_end = info->offset() + info->end() - info->start(); if (ptr >= info->offset() && ptr < offset_end) { ptr = info->start() + ptr - info->offset(); if (ReadVariableData(ptr)) { break; } } } } else if (info->offset() == 0 && !info->name().empty()) { map_zero = info.get(); } } } } // namespace unwindstack