libs/binder/RecordedTransaction.cpp - third_party/android/platform/frameworks/native - Git at Google

 /*
  * Copyright (C) 2022, 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 <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/scopeguard.h>
 #include <android-base/unique_fd.h>
 #include <binder/RecordedTransaction.h>
 #include <sys/mman.h>
 #include <algorithm>

 using android::Parcel;
 using android::base::borrowed_fd;
 using android::base::unique_fd;
 using android::binder::debug::RecordedTransaction;

 #define PADDING8(s) ((8 - (s) % 8) % 8)

 static_assert(PADDING8(0) == 0);
 static_assert(PADDING8(1) == 7);
 static_assert(PADDING8(7) == 1);
 static_assert(PADDING8(8) == 0);

 // Transactions are sequentially recorded to a file descriptor.
 //
 // An individual RecordedTransaction is written with the following format:
 //
 // WARNING: Though the following format is designed to be stable and
 // extensible, it is under active development and should be considered
 // unstable until this warning is removed.
 //
 // A RecordedTransaction is written to a file as a sequence of Chunks.
 //
 // A Chunk consists of a ChunkDescriptor, Data, Padding, and a Checksum.
 //
 // The ChunkDescriptor identifies the type of Data in the chunk, and the size
 // of the Data.
 //
 // The Data may be any uint32 number of bytes in length in [0-0xfffffff0].
 //
 // Padding is between [0-7] zero-bytes after the Data such that the Chunk ends
 // on an 8-byte boundary. The ChunkDescriptor's dataSize does not include the
 // size of Padding.
 //
 // The checksum is a 64-bit wide XOR of all previous data from the start of the
 // ChunkDescriptor to the end of Padding.
 //
 // ┌───────────────────────────┐
 // │Chunk                      │
 // │┌────────────────────────┐ │
 // ││ChunkDescriptor         │ │
 // ││┌───────────┬──────────┐│ │
 // │││chunkType  │dataSize  ├┼─┼─┐
 // │││uint32_t   │uint32_t  ││ │ │
 // ││└───────────┴──────────┘│ │ │
 // │└────────────────────────┘ │ │
 // │┌─────────────────────────┐│ │
 // ││Data                     ││ │
 // ││bytes * dataSize         │◀─┘
 // ││   ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤│
 // ││           Padding       ││
 // │└───┴─────────────────────┘│
 // │┌─────────────────────────┐│
 // ││checksum                 ││
 // ││uint64_t                 ││
 // │└─────────────────────────┘│
 // └───────────────────────────┘
 //
 // A RecordedTransaction is written as a Header Chunk with fields about the
 // transaction, a Data Parcel chunk, a Reply Parcel Chunk, and an End Chunk.
 // ┌──────────────────────┐
 // │     Header Chunk     │
 // ├──────────────────────┤
 // │  Sent Parcel Chunk   │
 // ├──────────────────────┤
 // │  Reply Parcel Chunk  │
 // ├──────────────────────┤
 // ║      End Chunk       ║
 // ╚══════════════════════╝
 //
 // On reading a RecordedTransaction, an unrecognized chunk is checksummed
 // then skipped according to size information in the ChunkDescriptor. Chunks
 // are read and either assimilated or skipped until an End Chunk is
 // encountered. This has three notable implications:
 //
 // 1. Older and newer implementations should be able to read one another's
 //    Transactions, though there will be loss of information.
 // 2. With the exception of the End Chunk, Chunks can appear in any order
 //    and even repeat, though this is not recommended.
 // 3. If any Chunk is repeated, old values will be overwritten by versions
 //    encountered later in the file.
 //
 // No effort is made to ensure the expected chunks are present. A single
 // End Chunk may therefore produce an empty, meaningless RecordedTransaction.

 RecordedTransaction::RecordedTransaction(RecordedTransaction&& t) noexcept {
     mData = t.mData;
     mSent.setData(t.getDataParcel().data(), t.getDataParcel().dataSize());
     mReply.setData(t.getReplyParcel().data(), t.getReplyParcel().dataSize());
 }

 std::optional<RecordedTransaction> RecordedTransaction::fromDetails(
         const String16& interfaceName, uint32_t code, uint32_t flags, timespec timestamp,
         const Parcel& dataParcel, const Parcel& replyParcel, status_t err) {
     RecordedTransaction t;
     t.mData.mHeader = {code,
                        flags,
                        static_cast<int32_t>(err),
                        dataParcel.isForRpc() ? static_cast<uint32_t>(1) : static_cast<uint32_t>(0),
                        static_cast<int64_t>(timestamp.tv_sec),
                        static_cast<int32_t>(timestamp.tv_nsec),
                        0};

     t.mData.mInterfaceName = std::string(String8(interfaceName).string());
     if (interfaceName.size() != t.mData.mInterfaceName.size()) {
         LOG(ERROR) << "Interface Name is not valid. Contains characters that aren't single byte "
                       "utf-8.";
         return std::nullopt;
     }

     if (t.mSent.setData(dataParcel.data(), dataParcel.dataBufferSize()) != android::NO_ERROR) {
         LOG(ERROR) << "Failed to set sent parcel data.";
         return std::nullopt;
     }

     if (t.mReply.setData(replyParcel.data(), replyParcel.dataBufferSize()) != android::NO_ERROR) {
         LOG(ERROR) << "Failed to set reply parcel data.";
         return std::nullopt;
     }

     return std::optional<RecordedTransaction>(std::move(t));
 }

 enum {
     HEADER_CHUNK = 1,
     DATA_PARCEL_CHUNK = 2,
     REPLY_PARCEL_CHUNK = 3,
     INTERFACE_NAME_CHUNK = 4,
     END_CHUNK = 0x00ffffff,
 };

 struct ChunkDescriptor {
     uint32_t chunkType = 0;
     uint32_t dataSize = 0;
 };
 static_assert(sizeof(ChunkDescriptor) % 8 == 0);

 constexpr uint32_t kMaxChunkDataSize = 0xfffffff0;
 typedef uint64_t transaction_checksum_t;

 static android::status_t readChunkDescriptor(borrowed_fd fd, ChunkDescriptor* chunkOut,
                                              transaction_checksum_t* sum) {
     if (!android::base::ReadFully(fd, chunkOut, sizeof(ChunkDescriptor))) {
         LOG(ERROR) << "Failed to read Chunk Descriptor from fd " << fd.get();
         return android::UNKNOWN_ERROR;
     }

     *sum ^= *reinterpret_cast<transaction_checksum_t*>(chunkOut);
     return android::NO_ERROR;
 }

 std::optional<RecordedTransaction> RecordedTransaction::fromFile(const unique_fd& fd) {
     RecordedTransaction t;
     ChunkDescriptor chunk;
     const long pageSize = sysconf(_SC_PAGE_SIZE);
     struct stat fileStat;
     if (fstat(fd.get(), &fileStat) != 0) {
         LOG(ERROR) << "Unable to get file information";
         return std::nullopt;
     }

     off_t fdCurrentPosition = lseek(fd.get(), 0, SEEK_CUR);
     if (fdCurrentPosition == -1) {
         LOG(ERROR) << "Invalid offset in file descriptor.";
         return std::nullopt;
     }
     do {
         if (fileStat.st_size < (fdCurrentPosition + (off_t)sizeof(ChunkDescriptor))) {
             LOG(ERROR) << "Not enough file remains to contain expected chunk descriptor";
             return std::nullopt;
         }
         transaction_checksum_t checksum = 0;
         if (NO_ERROR != readChunkDescriptor(fd, &chunk, &checksum)) {
             LOG(ERROR) << "Failed to read chunk descriptor.";
             return std::nullopt;
         }

         fdCurrentPosition = lseek(fd.get(), 0, SEEK_CUR);
         if (fdCurrentPosition == -1) {
             LOG(ERROR) << "Invalid offset in file descriptor.";
             return std::nullopt;
         }
         off_t mmapPageAlignedStart = (fdCurrentPosition / pageSize) * pageSize;
         off_t mmapPayloadStartOffset = fdCurrentPosition - mmapPageAlignedStart;

         if (chunk.dataSize > kMaxChunkDataSize) {
             LOG(ERROR) << "Chunk data exceeds maximum size.";
             return std::nullopt;
         }

         size_t chunkPayloadSize =
                 chunk.dataSize + PADDING8(chunk.dataSize) + sizeof(transaction_checksum_t);

         if (chunkPayloadSize > (size_t)(fileStat.st_size - fdCurrentPosition)) {
             LOG(ERROR) << "Chunk payload exceeds remaining file size.";
             return std::nullopt;
         }

         if (PADDING8(chunkPayloadSize) != 0) {
             LOG(ERROR) << "Invalid chunk size, not aligned " << chunkPayloadSize;
             return std::nullopt;
         }

         size_t memoryMappedSize = chunkPayloadSize + mmapPayloadStartOffset;
         void* mappedMemory =
                 mmap(NULL, memoryMappedSize, PROT_READ, MAP_SHARED, fd.get(), mmapPageAlignedStart);
         auto mmap_guard = android::base::make_scope_guard(
                 [mappedMemory, memoryMappedSize] { munmap(mappedMemory, memoryMappedSize); });

         transaction_checksum_t* payloadMap =
                 reinterpret_cast<transaction_checksum_t*>(mappedMemory);
         payloadMap += mmapPayloadStartOffset /
                 sizeof(transaction_checksum_t); // Skip chunk descriptor and required mmap
                                                 // page-alignment
         if (payloadMap == MAP_FAILED) {
             LOG(ERROR) << "Memory mapping failed for fd " << fd.get() << ": " << errno << " "
                        << strerror(errno);
             return std::nullopt;
         }
         for (size_t checksumIndex = 0;
              checksumIndex < chunkPayloadSize / sizeof(transaction_checksum_t); checksumIndex++) {
             checksum ^= payloadMap[checksumIndex];
         }
         if (checksum != 0) {
             LOG(ERROR) << "Checksum failed.";
             return std::nullopt;
         }

         fdCurrentPosition = lseek(fd.get(), chunkPayloadSize, SEEK_CUR);
         if (fdCurrentPosition == -1) {
             LOG(ERROR) << "Invalid offset in file descriptor.";
             return std::nullopt;
         }

         switch (chunk.chunkType) {
             case HEADER_CHUNK: {
                 if (chunk.dataSize != static_cast<uint32_t>(sizeof(TransactionHeader))) {
                     LOG(ERROR) << "Header Chunk indicated size " << chunk.dataSize << "; Expected "
                                << sizeof(TransactionHeader) << ".";
                     return std::nullopt;
                 }
                 t.mData.mHeader = *reinterpret_cast<TransactionHeader*>(payloadMap);
                 break;
             }
             case INTERFACE_NAME_CHUNK: {
                 t.mData.mInterfaceName =
                         std::string(reinterpret_cast<char*>(payloadMap), chunk.dataSize);
                 break;
             }
             case DATA_PARCEL_CHUNK: {
                 if (t.mSent.setData(reinterpret_cast<const unsigned char*>(payloadMap),
                                     chunk.dataSize) != android::NO_ERROR) {
                     LOG(ERROR) << "Failed to set sent parcel data.";
                     return std::nullopt;
                 }
                 break;
             }
             case REPLY_PARCEL_CHUNK: {
                 if (t.mReply.setData(reinterpret_cast<const unsigned char*>(payloadMap),
                                      chunk.dataSize) != android::NO_ERROR) {
                     LOG(ERROR) << "Failed to set reply parcel data.";
                     return std::nullopt;
                 }
                 break;
             }
             case END_CHUNK:
                 break;
             default:
                 LOG(INFO) << "Unrecognized chunk.";
                 break;
         }
     } while (chunk.chunkType != END_CHUNK);

     return std::optional<RecordedTransaction>(std::move(t));
 }

 android::status_t RecordedTransaction::writeChunk(borrowed_fd fd, uint32_t chunkType,
                                                   size_t byteCount, const uint8_t* data) const {
     if (byteCount > kMaxChunkDataSize) {
         LOG(ERROR) << "Chunk data exceeds maximum size";
         return BAD_VALUE;
     }
     ChunkDescriptor descriptor = {.chunkType = chunkType,
                                   .dataSize = static_cast<uint32_t>(byteCount)};
     // Prepare Chunk content as byte *
     const std::byte* descriptorBytes = reinterpret_cast<const std::byte*>(&descriptor);
     const std::byte* dataBytes = reinterpret_cast<const std::byte*>(data);

     // Add Chunk to intermediate buffer, except checksum
     std::vector<std::byte> buffer;
     buffer.insert(buffer.end(), descriptorBytes, descriptorBytes + sizeof(ChunkDescriptor));
     buffer.insert(buffer.end(), dataBytes, dataBytes + byteCount);
     std::byte zero{0};
     buffer.insert(buffer.end(), PADDING8(byteCount), zero);

     // Calculate checksum from buffer
     transaction_checksum_t* checksumData = reinterpret_cast<transaction_checksum_t*>(buffer.data());
     transaction_checksum_t checksumValue = 0;
     for (size_t idx = 0; idx < (buffer.size() / sizeof(transaction_checksum_t)); idx++) {
         checksumValue ^= checksumData[idx];
     }

     // Write checksum to buffer
     std::byte* checksumBytes = reinterpret_cast<std::byte*>(&checksumValue);
     buffer.insert(buffer.end(), checksumBytes, checksumBytes + sizeof(transaction_checksum_t));

     // Write buffer to file
     if (!android::base::WriteFully(fd, buffer.data(), buffer.size())) {
         LOG(ERROR) << "Failed to write chunk fd " << fd.get();
         return UNKNOWN_ERROR;
     }
     return NO_ERROR;
 }

 android::status_t RecordedTransaction::dumpToFile(const unique_fd& fd) const {
     if (NO_ERROR !=
         writeChunk(fd, HEADER_CHUNK, sizeof(TransactionHeader),
                    reinterpret_cast<const uint8_t*>(&(mData.mHeader)))) {
         LOG(ERROR) << "Failed to write transactionHeader to fd " << fd.get();
         return UNKNOWN_ERROR;
     }
     if (NO_ERROR !=
         writeChunk(fd, INTERFACE_NAME_CHUNK, mData.mInterfaceName.size() * sizeof(uint8_t),
                    reinterpret_cast<const uint8_t*>(mData.mInterfaceName.c_str()))) {
         LOG(INFO) << "Failed to write Interface Name Chunk to fd " << fd.get();
         return UNKNOWN_ERROR;
     }

     if (NO_ERROR != writeChunk(fd, DATA_PARCEL_CHUNK, mSent.dataBufferSize(), mSent.data())) {
         LOG(ERROR) << "Failed to write sent Parcel to fd " << fd.get();
         return UNKNOWN_ERROR;
     }
     if (NO_ERROR != writeChunk(fd, REPLY_PARCEL_CHUNK, mReply.dataBufferSize(), mReply.data())) {
         LOG(ERROR) << "Failed to write reply Parcel to fd " << fd.get();
         return UNKNOWN_ERROR;
     }
     if (NO_ERROR != writeChunk(fd, END_CHUNK, 0, NULL)) {
         LOG(ERROR) << "Failed to write end chunk to fd " << fd.get();
         return UNKNOWN_ERROR;
     }
     return NO_ERROR;
 }

 const std::string& RecordedTransaction::getInterfaceName() const {
     return mData.mInterfaceName;
 }

 uint32_t RecordedTransaction::getCode() const {
     return mData.mHeader.code;
 }

 uint32_t RecordedTransaction::getFlags() const {
     return mData.mHeader.flags;
 }

 int32_t RecordedTransaction::getReturnedStatus() const {
     return mData.mHeader.statusReturned;
 }

 timespec RecordedTransaction::getTimestamp() const {
     time_t sec = mData.mHeader.timestampSeconds;
     int32_t nsec = mData.mHeader.timestampNanoseconds;
     return (timespec){.tv_sec = sec, .tv_nsec = nsec};
 }

 uint32_t RecordedTransaction::getVersion() const {
     return mData.mHeader.version;
 }

 const Parcel& RecordedTransaction::getDataParcel() const {
     return mSent;
 }

 const Parcel& RecordedTransaction::getReplyParcel() const {
     return mReply;
 }
	/*
	* Copyright (C) 2022, 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 <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/scopeguard.h>
	#include <android-base/unique_fd.h>
	#include <binder/RecordedTransaction.h>
	#include <sys/mman.h>
	#include <algorithm>

	using android::Parcel;
	using android::base::borrowed_fd;
	using android::base::unique_fd;
	using android::binder::debug::RecordedTransaction;

	#define PADDING8(s) ((8 - (s) % 8) % 8)

	static_assert(PADDING8(0) == 0);
	static_assert(PADDING8(1) == 7);
	static_assert(PADDING8(7) == 1);
	static_assert(PADDING8(8) == 0);

	// Transactions are sequentially recorded to a file descriptor.
	//
	// An individual RecordedTransaction is written with the following format:
	//
	// WARNING: Though the following format is designed to be stable and
	// extensible, it is under active development and should be considered
	// unstable until this warning is removed.
	//
	// A RecordedTransaction is written to a file as a sequence of Chunks.
	//
	// A Chunk consists of a ChunkDescriptor, Data, Padding, and a Checksum.
	//
	// The ChunkDescriptor identifies the type of Data in the chunk, and the size
	// of the Data.
	//
	// The Data may be any uint32 number of bytes in length in [0-0xfffffff0].
	//
	// Padding is between [0-7] zero-bytes after the Data such that the Chunk ends
	// on an 8-byte boundary. The ChunkDescriptor's dataSize does not include the
	// size of Padding.
	//
	// The checksum is a 64-bit wide XOR of all previous data from the start of the
	// ChunkDescriptor to the end of Padding.
	//
	// ┌───────────────────────────┐
	// │Chunk │
	// │┌────────────────────────┐ │
	// ││ChunkDescriptor │ │
	// ││┌───────────┬──────────┐│ │
	// │││chunkType │dataSize ├┼─┼─┐
	// │││uint32_t │uint32_t ││ │ │
	// ││└───────────┴──────────┘│ │ │
	// │└────────────────────────┘ │ │
	// │┌─────────────────────────┐│ │
	// ││Data ││ │
	// ││bytes * dataSize │◀─┘
	// ││ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤│
	// ││ Padding ││
	// │└───┴─────────────────────┘│
	// │┌─────────────────────────┐│
	// ││checksum ││
	// ││uint64_t ││
	// │└─────────────────────────┘│
	// └───────────────────────────┘
	//
	// A RecordedTransaction is written as a Header Chunk with fields about the
	// transaction, a Data Parcel chunk, a Reply Parcel Chunk, and an End Chunk.
	// ┌──────────────────────┐
	// │ Header Chunk │
	// ├──────────────────────┤
	// │ Sent Parcel Chunk │
	// ├──────────────────────┤
	// │ Reply Parcel Chunk │
	// ├──────────────────────┤
	// ║ End Chunk ║
	// ╚══════════════════════╝
	//
	// On reading a RecordedTransaction, an unrecognized chunk is checksummed
	// then skipped according to size information in the ChunkDescriptor. Chunks
	// are read and either assimilated or skipped until an End Chunk is
	// encountered. This has three notable implications:
	//
	// 1. Older and newer implementations should be able to read one another's
	// Transactions, though there will be loss of information.
	// 2. With the exception of the End Chunk, Chunks can appear in any order
	// and even repeat, though this is not recommended.
	// 3. If any Chunk is repeated, old values will be overwritten by versions
	// encountered later in the file.
	//
	// No effort is made to ensure the expected chunks are present. A single
	// End Chunk may therefore produce an empty, meaningless RecordedTransaction.

	RecordedTransaction::RecordedTransaction(RecordedTransaction&& t) noexcept {
	mData = t.mData;
	mSent.setData(t.getDataParcel().data(), t.getDataParcel().dataSize());
	mReply.setData(t.getReplyParcel().data(), t.getReplyParcel().dataSize());
	}

	std::optional<RecordedTransaction> RecordedTransaction::fromDetails(
	const String16& interfaceName, uint32_t code, uint32_t flags, timespec timestamp,
	const Parcel& dataParcel, const Parcel& replyParcel, status_t err) {
	RecordedTransaction t;
	t.mData.mHeader = {code,
	flags,
	static_cast<int32_t>(err),
	dataParcel.isForRpc() ? static_cast<uint32_t>(1) : static_cast<uint32_t>(0),
	static_cast<int64_t>(timestamp.tv_sec),
	static_cast<int32_t>(timestamp.tv_nsec),
	0};

	t.mData.mInterfaceName = std::string(String8(interfaceName).string());
	if (interfaceName.size() != t.mData.mInterfaceName.size()) {
	LOG(ERROR) << "Interface Name is not valid. Contains characters that aren't single byte "
	"utf-8.";
	return std::nullopt;
	}

	if (t.mSent.setData(dataParcel.data(), dataParcel.dataBufferSize()) != android::NO_ERROR) {
	LOG(ERROR) << "Failed to set sent parcel data.";
	return std::nullopt;
	}

	if (t.mReply.setData(replyParcel.data(), replyParcel.dataBufferSize()) != android::NO_ERROR) {
	LOG(ERROR) << "Failed to set reply parcel data.";
	return std::nullopt;
	}

	return std::optional<RecordedTransaction>(std::move(t));
	}

	enum {
	HEADER_CHUNK = 1,
	DATA_PARCEL_CHUNK = 2,
	REPLY_PARCEL_CHUNK = 3,
	INTERFACE_NAME_CHUNK = 4,
	END_CHUNK = 0x00ffffff,
	};

	struct ChunkDescriptor {
	uint32_t chunkType = 0;
	uint32_t dataSize = 0;
	};
	static_assert(sizeof(ChunkDescriptor) % 8 == 0);

	constexpr uint32_t kMaxChunkDataSize = 0xfffffff0;
	typedef uint64_t transaction_checksum_t;

	static android::status_t readChunkDescriptor(borrowed_fd fd, ChunkDescriptor* chunkOut,
	transaction_checksum_t* sum) {
	if (!android::base::ReadFully(fd, chunkOut, sizeof(ChunkDescriptor))) {
	LOG(ERROR) << "Failed to read Chunk Descriptor from fd " << fd.get();
	return android::UNKNOWN_ERROR;
	}

	sum ^= reinterpret_cast<transaction_checksum_t*>(chunkOut);
	return android::NO_ERROR;
	}

	std::optional<RecordedTransaction> RecordedTransaction::fromFile(const unique_fd& fd) {
	RecordedTransaction t;
	ChunkDescriptor chunk;
	const long pageSize = sysconf(_SC_PAGE_SIZE);
	struct stat fileStat;
	if (fstat(fd.get(), &fileStat) != 0) {
	LOG(ERROR) << "Unable to get file information";
	return std::nullopt;
	}

	off_t fdCurrentPosition = lseek(fd.get(), 0, SEEK_CUR);
	if (fdCurrentPosition == -1) {
	LOG(ERROR) << "Invalid offset in file descriptor.";
	return std::nullopt;
	}
	do {
	if (fileStat.st_size < (fdCurrentPosition + (off_t)sizeof(ChunkDescriptor))) {
	LOG(ERROR) << "Not enough file remains to contain expected chunk descriptor";
	return std::nullopt;
	}
	transaction_checksum_t checksum = 0;
	if (NO_ERROR != readChunkDescriptor(fd, &chunk, &checksum)) {
	LOG(ERROR) << "Failed to read chunk descriptor.";
	return std::nullopt;
	}

	fdCurrentPosition = lseek(fd.get(), 0, SEEK_CUR);
	if (fdCurrentPosition == -1) {
	LOG(ERROR) << "Invalid offset in file descriptor.";
	return std::nullopt;
	}
	off_t mmapPageAlignedStart = (fdCurrentPosition / pageSize) * pageSize;
	off_t mmapPayloadStartOffset = fdCurrentPosition - mmapPageAlignedStart;

	if (chunk.dataSize > kMaxChunkDataSize) {
	LOG(ERROR) << "Chunk data exceeds maximum size.";
	return std::nullopt;
	}

	size_t chunkPayloadSize =
	chunk.dataSize + PADDING8(chunk.dataSize) + sizeof(transaction_checksum_t);

	if (chunkPayloadSize > (size_t)(fileStat.st_size - fdCurrentPosition)) {
	LOG(ERROR) << "Chunk payload exceeds remaining file size.";
	return std::nullopt;
	}

	if (PADDING8(chunkPayloadSize) != 0) {
	LOG(ERROR) << "Invalid chunk size, not aligned " << chunkPayloadSize;
	return std::nullopt;
	}

	size_t memoryMappedSize = chunkPayloadSize + mmapPayloadStartOffset;
	void* mappedMemory =
	mmap(NULL, memoryMappedSize, PROT_READ, MAP_SHARED, fd.get(), mmapPageAlignedStart);
	auto mmap_guard = android::base::make_scope_guard(
	[mappedMemory, memoryMappedSize] { munmap(mappedMemory, memoryMappedSize); });

	transaction_checksum_t* payloadMap =
	reinterpret_cast<transaction_checksum_t*>(mappedMemory);
	payloadMap += mmapPayloadStartOffset /
	sizeof(transaction_checksum_t); // Skip chunk descriptor and required mmap
	// page-alignment
	if (payloadMap == MAP_FAILED) {
	LOG(ERROR) << "Memory mapping failed for fd " << fd.get() << ": " << errno << " "
	<< strerror(errno);
	return std::nullopt;
	}
	for (size_t checksumIndex = 0;
	checksumIndex < chunkPayloadSize / sizeof(transaction_checksum_t); checksumIndex++) {
	checksum ^= payloadMap[checksumIndex];
	}
	if (checksum != 0) {
	LOG(ERROR) << "Checksum failed.";
	return std::nullopt;
	}

	fdCurrentPosition = lseek(fd.get(), chunkPayloadSize, SEEK_CUR);
	if (fdCurrentPosition == -1) {
	LOG(ERROR) << "Invalid offset in file descriptor.";
	return std::nullopt;
	}

	switch (chunk.chunkType) {
	case HEADER_CHUNK: {
	if (chunk.dataSize != static_cast<uint32_t>(sizeof(TransactionHeader))) {
	LOG(ERROR) << "Header Chunk indicated size " << chunk.dataSize << "; Expected "
	<< sizeof(TransactionHeader) << ".";
	return std::nullopt;
	}
	t.mData.mHeader = reinterpret_cast<TransactionHeader>(payloadMap);
	break;
	}
	case INTERFACE_NAME_CHUNK: {
	t.mData.mInterfaceName =
	std::string(reinterpret_cast<char*>(payloadMap), chunk.dataSize);
	break;
	}
	case DATA_PARCEL_CHUNK: {
	if (t.mSent.setData(reinterpret_cast<const unsigned char*>(payloadMap),
	chunk.dataSize) != android::NO_ERROR) {
	LOG(ERROR) << "Failed to set sent parcel data.";
	return std::nullopt;
	}
	break;
	}
	case REPLY_PARCEL_CHUNK: {
	if (t.mReply.setData(reinterpret_cast<const unsigned char*>(payloadMap),
	chunk.dataSize) != android::NO_ERROR) {
	LOG(ERROR) << "Failed to set reply parcel data.";
	return std::nullopt;
	}
	break;
	}
	case END_CHUNK:
	break;
	default:
	LOG(INFO) << "Unrecognized chunk.";
	break;
	}
	} while (chunk.chunkType != END_CHUNK);

	return std::optional<RecordedTransaction>(std::move(t));
	}

	android::status_t RecordedTransaction::writeChunk(borrowed_fd fd, uint32_t chunkType,
	size_t byteCount, const uint8_t* data) const {
	if (byteCount > kMaxChunkDataSize) {
	LOG(ERROR) << "Chunk data exceeds maximum size";
	return BAD_VALUE;
	}
	ChunkDescriptor descriptor = {.chunkType = chunkType,
	.dataSize = static_cast<uint32_t>(byteCount)};
	// Prepare Chunk content as byte *
	const std::byte* descriptorBytes = reinterpret_cast<const std::byte*>(&descriptor);
	const std::byte* dataBytes = reinterpret_cast<const std::byte*>(data);

	// Add Chunk to intermediate buffer, except checksum
	std::vector<std::byte> buffer;
	buffer.insert(buffer.end(), descriptorBytes, descriptorBytes + sizeof(ChunkDescriptor));
	buffer.insert(buffer.end(), dataBytes, dataBytes + byteCount);
	std::byte zero{0};
	buffer.insert(buffer.end(), PADDING8(byteCount), zero);

	// Calculate checksum from buffer
	transaction_checksum_t* checksumData = reinterpret_cast<transaction_checksum_t*>(buffer.data());
	transaction_checksum_t checksumValue = 0;
	for (size_t idx = 0; idx < (buffer.size() / sizeof(transaction_checksum_t)); idx++) {
	checksumValue ^= checksumData[idx];
	}

	// Write checksum to buffer
	std::byte* checksumBytes = reinterpret_cast<std::byte*>(&checksumValue);
	buffer.insert(buffer.end(), checksumBytes, checksumBytes + sizeof(transaction_checksum_t));

	// Write buffer to file
	if (!android::base::WriteFully(fd, buffer.data(), buffer.size())) {
	LOG(ERROR) << "Failed to write chunk fd " << fd.get();
	return UNKNOWN_ERROR;
	}
	return NO_ERROR;
	}

	android::status_t RecordedTransaction::dumpToFile(const unique_fd& fd) const {
	if (NO_ERROR !=
	writeChunk(fd, HEADER_CHUNK, sizeof(TransactionHeader),
	reinterpret_cast<const uint8_t*>(&(mData.mHeader)))) {
	LOG(ERROR) << "Failed to write transactionHeader to fd " << fd.get();
	return UNKNOWN_ERROR;
	}
	if (NO_ERROR !=
	writeChunk(fd, INTERFACE_NAME_CHUNK, mData.mInterfaceName.size() * sizeof(uint8_t),
	reinterpret_cast<const uint8_t*>(mData.mInterfaceName.c_str()))) {
	LOG(INFO) << "Failed to write Interface Name Chunk to fd " << fd.get();
	return UNKNOWN_ERROR;
	}

	if (NO_ERROR != writeChunk(fd, DATA_PARCEL_CHUNK, mSent.dataBufferSize(), mSent.data())) {
	LOG(ERROR) << "Failed to write sent Parcel to fd " << fd.get();
	return UNKNOWN_ERROR;
	}
	if (NO_ERROR != writeChunk(fd, REPLY_PARCEL_CHUNK, mReply.dataBufferSize(), mReply.data())) {
	LOG(ERROR) << "Failed to write reply Parcel to fd " << fd.get();
	return UNKNOWN_ERROR;
	}
	if (NO_ERROR != writeChunk(fd, END_CHUNK, 0, NULL)) {
	LOG(ERROR) << "Failed to write end chunk to fd " << fd.get();
	return UNKNOWN_ERROR;
	}
	return NO_ERROR;
	}

	const std::string& RecordedTransaction::getInterfaceName() const {
	return mData.mInterfaceName;
	}

	uint32_t RecordedTransaction::getCode() const {
	return mData.mHeader.code;
	}

	uint32_t RecordedTransaction::getFlags() const {
	return mData.mHeader.flags;
	}

	int32_t RecordedTransaction::getReturnedStatus() const {
	return mData.mHeader.statusReturned;
	}

	timespec RecordedTransaction::getTimestamp() const {
	time_t sec = mData.mHeader.timestampSeconds;
	int32_t nsec = mData.mHeader.timestampNanoseconds;
	return (timespec){.tv_sec = sec, .tv_nsec = nsec};
	}

	uint32_t RecordedTransaction::getVersion() const {
	return mData.mHeader.version;
	}

	const Parcel& RecordedTransaction::getDataParcel() const {
	return mSent;
	}

	const Parcel& RecordedTransaction::getReplyParcel() const {
	return mReply;
	}