libunwindstack/MapInfo.cpp - platform_system_core - Gitiles

 /*
  * 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 <android-base/stringprintf.h>

 #include <unwindstack/Elf.h>
 #include <unwindstack/MapInfo.h>
 #include <unwindstack/Maps.h>
 #include <unwindstack/Memory.h>

 namespace unwindstack {

 bool MapInfo::InitFileMemoryFromPreviousReadOnlyMap(MemoryFileAtOffset* memory) {
   // One last attempt, see if the previous map is read-only with the
   // same name and stretches across this map.
   if (prev_map == nullptr || prev_map->flags != PROT_READ) {
     return false;
   }

   uint64_t map_size = end - prev_map->end;
   if (!memory->Init(name, prev_map->offset, map_size)) {
     return false;
   }

   uint64_t max_size;
   if (!Elf::GetInfo(memory, &max_size) || max_size < map_size) {
     return false;
   }

   if (!memory->Init(name, prev_map->offset, max_size)) {
     return false;
   }

   elf_offset = offset - prev_map->offset;
   elf_start_offset = prev_map->offset;
   return true;
 }

 Memory* MapInfo::GetFileMemory() {
   std::unique_ptr<MemoryFileAtOffset> memory(new MemoryFileAtOffset);
   if (offset == 0) {
     if (memory->Init(name, 0)) {
       return memory.release();
     }
     return nullptr;
   }

   // These are the possibilities when the offset is non-zero.
   // - There is an elf file embedded in a file, and the offset is the
   //   the start of the elf in the file.
   // - There is an elf file embedded in a file, and the offset is the
   //   the start of the executable part of the file. The actual start
   //   of the elf is in the read-only segment preceeding this map.
   // - 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;
   }

   // Check if the start of this map is an embedded elf.
   uint64_t max_size = 0;
   if (Elf::GetInfo(memory.get(), &max_size)) {
     elf_start_offset = offset;
     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();
       }
       elf_start_offset = 0;
       return nullptr;
     }
     return memory.release();
   }

   // No elf at offset, try to init as if the whole file is an elf.
   if (memory->Init(name, 0) && Elf::IsValidElf(memory.get())) {
     elf_offset = offset;
     // Need to check how to set the elf start offset. If this map is not
     // the r-x map of a r-- map, then use the real offset value. Otherwise,
     // use 0.
     if (prev_map == nullptr || prev_map->offset != 0 || prev_map->flags != PROT_READ ||
         prev_map->name != name) {
       elf_start_offset = offset;
     }
     return memory.release();
   }

   // See if the map previous to this one contains a read-only map
   // that represents the real start of the elf data.
   if (InitFileMemoryFromPreviousReadOnlyMap(memory.get())) {
     return memory.release();
   }

   // Failed to find elf at start of file or at read-only map, return
   // file object from the current map.
   if (memory->Init(name, offset, map_size)) {
     return memory.release();
   }
   return nullptr;
 }

 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 (process_memory == nullptr) {
     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));
   if (Elf::IsValidElf(memory.get())) {
     memory_backed_elf = true;
     return memory.release();
   }

   // Find the read-only map by looking at the previous map. The linker
   // doesn't guarantee that this invariant will always be true. However,
   // if that changes, there is likely something else that will change and
   // break something.
   if (offset == 0 || name.empty() || prev_map == nullptr || prev_map->name != name ||
       prev_map->offset >= offset) {
     return nullptr;
   }

   // Make sure that relative pc values are corrected properly.
   elf_offset = offset - prev_map->offset;
   // Use this as the elf start offset, otherwise, you always get offsets into
   // the r-x section, which is not quite the right information.
   elf_start_offset = prev_map->offset;

   MemoryRanges* ranges = new MemoryRanges;
   ranges->Insert(
       new MemoryRange(process_memory, prev_map->start, prev_map->end - prev_map->start, 0));
   ranges->Insert(new MemoryRange(process_memory, start, end - start, elf_offset));

   memory_backed_elf = true;
   return ranges;
 }

 Elf* MapInfo::GetElf(const std::shared_ptr<Memory>& process_memory, ArchEnum expected_arch) {
   {
     // 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();
     if (elf->valid() && expected_arch != elf->arch()) {
       // Make the elf invalid, mismatch between arch and expected arch.
       elf->Invalidate();
     }

     if (locked) {
       Elf::CacheAdd(this);
       Elf::CacheUnlock();
     }
   }

   // If there is a read-only map then a read-execute map that represents the
   // same elf object, make sure the previous map is using the same elf
   // object if it hasn't already been set.
   if (prev_map != nullptr && elf_start_offset != offset && prev_map->offset == elf_start_offset &&
       prev_map->name == name) {
     std::lock_guard<std::mutex> guard(prev_map->mutex_);
     if (prev_map->elf.get() == nullptr) {
       prev_map->elf = elf;
       prev_map->memory_backed_elf = memory_backed_elf;
     }
   }
   return elf.get();
 }

 bool MapInfo::GetFunctionName(uint64_t addr, std::string* name, uint64_t* func_offset) {
   {
     // Make sure no other thread is trying to update this elf object.
     std::lock_guard<std::mutex> guard(mutex_);
     if (elf == nullptr) {
       return false;
     }
   }
   // No longer need the lock, once the elf object is created, it is not deleted
   // until this object is deleted.
   return elf->GetFunctionName(addr, name, func_offset);
 }

 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;
 }

 MapInfo::~MapInfo() {
   uintptr_t id = build_id.load();
   if (id != 0) {
     delete reinterpret_cast<std::string*>(id);
   }
 }

 std::string MapInfo::GetBuildID() {
   uintptr_t id = build_id.load();
   if (build_id != 0) {
     return *reinterpret_cast<std::string*>(id);
   }

   // No need to lock, at worst if multiple threads do this at the same
   // time it should be detected and only one thread should win and
   // save the data.
   std::unique_ptr<std::string> cur_build_id(new std::string);

   // Now need to see if the elf object exists.
   // Make sure no other thread is trying to add the elf to this map.
   mutex_.lock();
   Elf* elf_obj = elf.get();
   mutex_.unlock();
   if (elf_obj != nullptr) {
     *cur_build_id = elf_obj->GetBuildID();
   } else {
     // This will only work if we can get the file associated with this memory.
     // If this is only available in memory, then the section name information
     // is not present and we will not be able to find the build id info.
     std::unique_ptr<Memory> memory(GetFileMemory());
     if (memory != nullptr) {
       *cur_build_id = Elf::GetBuildID(memory.get());
     }
   }

   id = reinterpret_cast<uintptr_t>(cur_build_id.get());
   uintptr_t expected_id = 0;
   if (build_id.compare_exchange_weak(expected_id, id)) {
     // Value saved, so make sure the memory is not freed.
     cur_build_id.release();
   }
   return *reinterpret_cast<std::string*>(id);
 }

 std::string MapInfo::GetPrintableBuildID() {
   std::string raw_build_id = GetBuildID();
   if (raw_build_id.empty()) {
     return "";
   }
   std::string printable_build_id;
   for (const char& c : raw_build_id) {
     // Use %hhx to avoid sign extension on abis that have signed chars.
     printable_build_id += android::base::StringPrintf("%02hhx", c);
   }
   return printable_build_id;
 }

 }  // namespace unwindstack
	/*
	* 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 <android-base/stringprintf.h>

	#include <unwindstack/Elf.h>
	#include <unwindstack/MapInfo.h>
	#include <unwindstack/Maps.h>
	#include <unwindstack/Memory.h>

	namespace unwindstack {

	bool MapInfo::InitFileMemoryFromPreviousReadOnlyMap(MemoryFileAtOffset* memory) {
	// One last attempt, see if the previous map is read-only with the
	// same name and stretches across this map.
	if (prev_map == nullptr \|\| prev_map->flags != PROT_READ) {
	return false;
	}

	uint64_t map_size = end - prev_map->end;
	if (!memory->Init(name, prev_map->offset, map_size)) {
	return false;
	}

	uint64_t max_size;
	if (!Elf::GetInfo(memory, &max_size) \|\| max_size < map_size) {
	return false;
	}

	if (!memory->Init(name, prev_map->offset, max_size)) {
	return false;
	}

	elf_offset = offset - prev_map->offset;
	elf_start_offset = prev_map->offset;
	return true;
	}

	Memory* MapInfo::GetFileMemory() {
	std::unique_ptr<MemoryFileAtOffset> memory(new MemoryFileAtOffset);
	if (offset == 0) {
	if (memory->Init(name, 0)) {
	return memory.release();
	}
	return nullptr;
	}

	// These are the possibilities when the offset is non-zero.
	// - There is an elf file embedded in a file, and the offset is the
	// the start of the elf in the file.
	// - There is an elf file embedded in a file, and the offset is the
	// the start of the executable part of the file. The actual start
	// of the elf is in the read-only segment preceeding this map.
	// - 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;
	}

	// Check if the start of this map is an embedded elf.
	uint64_t max_size = 0;
	if (Elf::GetInfo(memory.get(), &max_size)) {
	elf_start_offset = offset;
	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();
	}
	elf_start_offset = 0;
	return nullptr;
	}
	return memory.release();
	}

	// No elf at offset, try to init as if the whole file is an elf.
	if (memory->Init(name, 0) && Elf::IsValidElf(memory.get())) {
	elf_offset = offset;
	// Need to check how to set the elf start offset. If this map is not
	// the r-x map of a r-- map, then use the real offset value. Otherwise,
	// use 0.
	if (prev_map == nullptr \|\| prev_map->offset != 0 \|\| prev_map->flags != PROT_READ \|\|
	prev_map->name != name) {
	elf_start_offset = offset;
	}
	return memory.release();
	}

	// See if the map previous to this one contains a read-only map
	// that represents the real start of the elf data.
	if (InitFileMemoryFromPreviousReadOnlyMap(memory.get())) {
	return memory.release();
	}

	// Failed to find elf at start of file or at read-only map, return
	// file object from the current map.
	if (memory->Init(name, offset, map_size)) {
	return memory.release();
	}
	return nullptr;
	}

	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 (process_memory == nullptr) {
	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));
	if (Elf::IsValidElf(memory.get())) {
	memory_backed_elf = true;
	return memory.release();
	}

	// Find the read-only map by looking at the previous map. The linker
	// doesn't guarantee that this invariant will always be true. However,
	// if that changes, there is likely something else that will change and
	// break something.
	if (offset == 0 \|\| name.empty() \|\| prev_map == nullptr \|\| prev_map->name != name \|\|
	prev_map->offset >= offset) {
	return nullptr;
	}

	// Make sure that relative pc values are corrected properly.
	elf_offset = offset - prev_map->offset;
	// Use this as the elf start offset, otherwise, you always get offsets into
	// the r-x section, which is not quite the right information.
	elf_start_offset = prev_map->offset;

	MemoryRanges* ranges = new MemoryRanges;
	ranges->Insert(
	new MemoryRange(process_memory, prev_map->start, prev_map->end - prev_map->start, 0));
	ranges->Insert(new MemoryRange(process_memory, start, end - start, elf_offset));

	memory_backed_elf = true;
	return ranges;
	}

	Elf* MapInfo::GetElf(const std::shared_ptr<Memory>& process_memory, ArchEnum expected_arch) {
	{
	// 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();
	if (elf->valid() && expected_arch != elf->arch()) {
	// Make the elf invalid, mismatch between arch and expected arch.
	elf->Invalidate();
	}

	if (locked) {
	Elf::CacheAdd(this);
	Elf::CacheUnlock();
	}
	}

	// If there is a read-only map then a read-execute map that represents the
	// same elf object, make sure the previous map is using the same elf
	// object if it hasn't already been set.
	if (prev_map != nullptr && elf_start_offset != offset && prev_map->offset == elf_start_offset &&
	prev_map->name == name) {
	std::lock_guard<std::mutex> guard(prev_map->mutex_);
	if (prev_map->elf.get() == nullptr) {
	prev_map->elf = elf;
	prev_map->memory_backed_elf = memory_backed_elf;
	}
	}
	return elf.get();
	}

	bool MapInfo::GetFunctionName(uint64_t addr, std::string* name, uint64_t* func_offset) {
	{
	// Make sure no other thread is trying to update this elf object.
	std::lock_guard<std::mutex> guard(mutex_);
	if (elf == nullptr) {
	return false;
	}
	}
	// No longer need the lock, once the elf object is created, it is not deleted
	// until this object is deleted.
	return elf->GetFunctionName(addr, name, func_offset);
	}

	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;
	}

	MapInfo::~MapInfo() {
	uintptr_t id = build_id.load();
	if (id != 0) {
	delete reinterpret_cast<std::string*>(id);
	}
	}

	std::string MapInfo::GetBuildID() {
	uintptr_t id = build_id.load();
	if (build_id != 0) {
	return reinterpret_cast<std::string>(id);
	}

	// No need to lock, at worst if multiple threads do this at the same
	// time it should be detected and only one thread should win and
	// save the data.
	std::unique_ptr<std::string> cur_build_id(new std::string);

	// Now need to see if the elf object exists.
	// Make sure no other thread is trying to add the elf to this map.
	mutex_.lock();
	Elf* elf_obj = elf.get();
	mutex_.unlock();
	if (elf_obj != nullptr) {
	*cur_build_id = elf_obj->GetBuildID();
	} else {
	// This will only work if we can get the file associated with this memory.
	// If this is only available in memory, then the section name information
	// is not present and we will not be able to find the build id info.
	std::unique_ptr<Memory> memory(GetFileMemory());
	if (memory != nullptr) {
	*cur_build_id = Elf::GetBuildID(memory.get());
	}
	}

	id = reinterpret_cast<uintptr_t>(cur_build_id.get());
	uintptr_t expected_id = 0;
	if (build_id.compare_exchange_weak(expected_id, id)) {
	// Value saved, so make sure the memory is not freed.
	cur_build_id.release();
	}
	return reinterpret_cast<std::string>(id);
	}

	std::string MapInfo::GetPrintableBuildID() {
	std::string raw_build_id = GetBuildID();
	if (raw_build_id.empty()) {
	return "";
	}
	std::string printable_build_id;
	for (const char& c : raw_build_id) {
	// Use %hhx to avoid sign extension on abis that have signed chars.
	printable_build_id += android::base::StringPrintf("%02hhx", c);
	}
	return printable_build_id;
	}

	} // namespace unwindstack