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/*
* Copyright (C) 2017 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 <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <memory>
#include <mutex>
#include <string>
#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include <unwindstack/Memory.h>
namespace unwindstack {
Memory* MapInfo::GetFileMemory() {
std::unique_ptr<MemoryFileAtOffset> memory(new MemoryFileAtOffset);
if (offset == 0) {
if (memory->Init(name, 0)) {
return memory.release();
}
return nullptr;
}
// There are two possibilities when the offset is non-zero.
// - There is an elf file embedded in a file.
// - The whole file is an elf file, and the offset needs to be saved.
//
// Map in just the part of the file for the map. If this is not
// a valid elf, then reinit as if the whole file is an elf file.
// If the offset is a valid elf, then determine the size of the map
// and reinit to that size. This is needed because the dynamic linker
// only maps in a portion of the original elf, and never the symbol
// file data.
uint64_t map_size = end - start;
if (!memory->Init(name, offset, map_size)) {
return nullptr;
}
bool valid;
uint64_t max_size;
Elf::GetInfo(memory.get(), &valid, &max_size);
if (!valid) {
// Init as if the whole file is an elf.
if (memory->Init(name, 0)) {
elf_offset = offset;
return memory.release();
}
return nullptr;
}
if (max_size > map_size) {
if (memory->Init(name, offset, max_size)) {
return memory.release();
}
// Try to reinit using the default map_size.
if (memory->Init(name, offset, map_size)) {
return memory.release();
}
return nullptr;
}
return memory.release();
}
Memory* MapInfo::CreateMemory(const std::shared_ptr<Memory>& process_memory) {
if (end <= start) {
return nullptr;
}
elf_offset = 0;
// Fail on device maps.
if (flags & MAPS_FLAGS_DEVICE_MAP) {
return nullptr;
}
// First try and use the file associated with the info.
if (!name.empty()) {
Memory* memory = GetFileMemory();
if (memory != nullptr) {
return memory;
}
}
// If the map isn't readable, don't bother trying to read from process memory.
if (!(flags & PROT_READ)) {
return nullptr;
}
// Need to verify that this elf is valid. It's possible that
// only part of the elf file to be mapped into memory is in the executable
// map. In this case, there will be another read-only map that includes the
// first part of the elf file. This is done if the linker rosegment
// option is used.
std::unique_ptr<MemoryRange> memory(new MemoryRange(process_memory, start, end - start, 0));
bool valid;
uint64_t max_size;
Elf::GetInfo(memory.get(), &valid, &max_size);
if (valid) {
// Valid elf, we are done.
return memory.release();
}
if (name.empty() || maps_ == nullptr) {
return nullptr;
}
// Find the read-only map that has the same name and has an offset closest
// to the current offset but less than the offset of the current map.
// For shared libraries, there should be a r-x map that has a non-zero
// offset and then a r-- map that has a zero offset.
// For shared libraries loaded from an apk, there should be a r-x map that
// has a non-zero offset and then a r-- map that has a non-zero offset less
// than the offset from the r-x map.
uint64_t closest_offset = 0;
MapInfo* ro_map_info = nullptr;
for (auto map_info : *maps_) {
if (map_info->flags == PROT_READ && map_info->name == name && map_info->offset < offset &&
map_info->offset >= closest_offset) {
ro_map_info = map_info;
closest_offset = ro_map_info->offset;
}
}
if (ro_map_info != nullptr) {
// Make sure that relative pc values are corrected properly.
elf_offset = offset - closest_offset;
MemoryRanges* ranges = new MemoryRanges;
ranges->Insert(new MemoryRange(process_memory, ro_map_info->start,
ro_map_info->end - ro_map_info->start, 0));
ranges->Insert(new MemoryRange(process_memory, start, end - start, elf_offset));
return ranges;
}
return nullptr;
}
Elf* MapInfo::GetElf(const std::shared_ptr<Memory>& process_memory, bool init_gnu_debugdata) {
// Make sure no other thread is trying to add the elf to this map.
std::lock_guard<std::mutex> guard(mutex_);
if (elf.get() != nullptr) {
return elf.get();
}
bool locked = false;
if (Elf::CachingEnabled() && !name.empty()) {
Elf::CacheLock();
locked = true;
if (Elf::CacheGet(this)) {
Elf::CacheUnlock();
return elf.get();
}
}
Memory* memory = CreateMemory(process_memory);
if (locked) {
if (Elf::CacheAfterCreateMemory(this)) {
delete memory;
Elf::CacheUnlock();
return elf.get();
}
}
elf.reset(new Elf(memory));
// If the init fails, keep the elf around as an invalid object so we
// don't try to reinit the object.
elf->Init(init_gnu_debugdata);
if (locked) {
Elf::CacheAdd(this);
Elf::CacheUnlock();
}
return elf.get();
}
uint64_t MapInfo::GetLoadBias(const std::shared_ptr<Memory>& process_memory) {
uint64_t cur_load_bias = load_bias.load();
if (cur_load_bias != static_cast<uint64_t>(-1)) {
return cur_load_bias;
}
{
// Make sure no other thread is trying to add the elf to this map.
std::lock_guard<std::mutex> guard(mutex_);
if (elf != nullptr) {
if (elf->valid()) {
cur_load_bias = elf->GetLoadBias();
load_bias = cur_load_bias;
return cur_load_bias;
} else {
load_bias = 0;
return 0;
}
}
}
// Call lightweight static function that will only read enough of the
// elf data to get the load bias.
std::unique_ptr<Memory> memory(CreateMemory(process_memory));
cur_load_bias = Elf::GetLoadBias(memory.get());
load_bias = cur_load_bias;
return cur_load_bias;
}
} // namespace unwindstack
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