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126 lines
4.2 KiB
C++
126 lines
4.2 KiB
C++
/*
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* Copyright (c) 2020-2022, Liav A. <liavalb@hotmail.co.il>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Debug.h>
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#include <LibPartition/MBRPartitionTable.h>
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namespace Partition {
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#define MBR_SIGNATURE 0xaa55
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#define MBR_PROTECTIVE 0xEE
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#define EBR_CHS_CONTAINER 0x05
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#define EBR_LBA_CONTAINER 0x0F
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ErrorOr<NonnullOwnPtr<MBRPartitionTable>> MBRPartitionTable::try_to_initialize(PartitionableDevice device)
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{
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auto table = TRY(adopt_nonnull_own_or_enomem(new (nothrow) MBRPartitionTable(move(device))));
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if (table->contains_ebr())
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return Error::from_errno(ENOTSUP);
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if (table->is_protective_mbr())
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return Error::from_errno(ENOTSUP);
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if (!table->is_valid())
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return Error::from_errno(EINVAL);
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return table;
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}
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OwnPtr<MBRPartitionTable> MBRPartitionTable::try_to_initialize(PartitionableDevice device, u32 start_lba)
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{
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auto table = adopt_nonnull_own_or_enomem(new (nothrow) MBRPartitionTable(move(device), start_lba)).release_value_but_fixme_should_propagate_errors();
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if (!table->is_valid())
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return {};
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return table;
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}
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bool MBRPartitionTable::read_boot_record()
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{
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if (block_size() != 512)
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return false;
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auto maybe_error = m_device.read_block(m_start_lba, m_cached_header.bytes());
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m_header_valid = !maybe_error.is_error();
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return m_header_valid;
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}
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MBRPartitionTable::MBRPartitionTable(PartitionableDevice device, u32 start_lba)
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: PartitionTable(move(device))
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, m_start_lba(start_lba)
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, m_cached_header(ByteBuffer::create_zeroed(block_size()).release_value_but_fixme_should_propagate_errors()) // FIXME: Do something sensible if this fails because of OOM.
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{
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if (!read_boot_record() || !initialize())
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return;
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m_header_valid = true;
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auto& header = this->header();
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for (size_t index = 0; index < 4; index++) {
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auto& entry = header.entry[index];
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if (entry.offset == 0x00) {
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continue;
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}
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// We have to place these in stack variables, since try_empend will try to take a reference to them, which is UB (since they're gnu::packed and unaligned)
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u64 const block_offset = entry.offset;
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u64 const block_limit = (entry.offset + entry.length) - 1;
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u8 const partition_type = entry.type;
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MUST(m_partitions.try_empend(block_offset, block_limit, partition_type));
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}
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m_valid = true;
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}
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MBRPartitionTable::MBRPartitionTable(PartitionableDevice device)
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: PartitionTable(move(device))
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, m_start_lba(0)
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, m_cached_header(ByteBuffer::create_zeroed(block_size()).release_value_but_fixme_should_propagate_errors()) // FIXME: Do something sensible if this fails because of OOM.
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{
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if (!read_boot_record() || contains_ebr() || is_protective_mbr() || !initialize())
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return;
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auto& header = this->header();
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for (size_t index = 0; index < 4; index++) {
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auto& entry = header.entry[index];
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if (entry.offset == 0x00) {
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continue;
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}
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// We have to place these in stack variables, since try_empend will try to take a reference to them, which is UB (since they're gnu::packed and unaligned)
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u64 const block_offset = entry.offset;
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u64 const block_limit = (entry.offset + entry.length) - 1;
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u8 const partition_type = entry.type;
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MUST(m_partitions.try_empend(block_offset, block_limit, partition_type));
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}
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m_valid = true;
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}
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MBRPartitionTable::~MBRPartitionTable() = default;
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MBRPartitionTable::Header const& MBRPartitionTable::header() const
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{
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return *(MBRPartitionTable::Header const*)m_cached_header.data();
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}
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bool MBRPartitionTable::initialize()
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{
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auto& header = this->header();
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dbgln_if(MBR_DEBUG, "Master Boot Record: mbr_signature={:#08x}", header.mbr_signature);
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if (header.mbr_signature != MBR_SIGNATURE) {
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dbgln("Master Boot Record: invalid signature");
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return false;
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}
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return true;
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}
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bool MBRPartitionTable::contains_ebr() const
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{
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for (int i = 0; i < 4; i++) {
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if (header().entry[i].type == EBR_CHS_CONTAINER || header().entry[i].type == EBR_LBA_CONTAINER)
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return true;
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}
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return false;
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}
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bool MBRPartitionTable::is_protective_mbr() const
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{
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return header().entry[0].type == MBR_PROTECTIVE;
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}
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}
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