serenity/Kernel/Storage/Partition/EBRPartitionTable.cpp

/*
 * Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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#include <AK/ByteBuffer.h>
#include <Kernel/Storage/Partition/EBRPartitionTable.h>

namespace Kernel {

Result<NonnullOwnPtr<EBRPartitionTable>, PartitionTable::Error> EBRPartitionTable::try_to_initialize(const StorageDevice& device)
{
    auto table = make<EBRPartitionTable>(device);
    if (table->is_protective_mbr())
        return { PartitionTable::Error::MBRProtective };
    if (!table->is_valid())
        return { PartitionTable::Error::Invalid };
    return table;
}

void EBRPartitionTable::search_extended_partition(const StorageDevice& device, MBRPartitionTable& checked_ebr, u64 current_block_offset, size_t limit)
{
    if (limit == 0)
        return;
    // EBRs should not carry more than 2 partitions (because they need to form a linked list)
    ASSERT(checked_ebr.partitions_count() <= 2);
    auto checked_logical_partition = checked_ebr.partition(0);

    // If we are pointed to an invalid logical partition, something is seriously wrong.
    ASSERT(checked_logical_partition.has_value());
    m_partitions.append(checked_logical_partition.value().offset(current_block_offset));
    if (!checked_ebr.contains_ebr())
        return;
    current_block_offset += checked_ebr.partition(1).value().start_block();
    auto next_ebr = MBRPartitionTable::try_to_initialize(device, current_block_offset);
    if (!next_ebr)
        return;
    search_extended_partition(device, *next_ebr, current_block_offset, (limit - 1));
}

EBRPartitionTable::EBRPartitionTable(const StorageDevice& device)
    : MBRPartitionTable(device)
{
    if (!is_header_valid())
        return;
    m_valid = true;

    ASSERT(partitions_count() == 0);

    auto& header = this->header();
    for (size_t index = 0; index < 4; index++) {
        auto& entry = header.entry[index];
        // Start enumerating all logical partitions
        if (entry.type == 0xf) {
            auto checked_ebr = MBRPartitionTable::try_to_initialize(device, entry.offset);
            if (!checked_ebr)
                continue;
            // It's quite unlikely to see that amount of partitions, so stop at 128 partitions.
            search_extended_partition(device, *checked_ebr, entry.offset, 128);
            continue;
        }

        if (entry.offset == 0x00) {
            continue;
        }
        auto partition_type = ByteBuffer::create_zeroed(sizeof(u8));
        partition_type.data()[0] = entry.type;
        m_partitions.append(DiskPartitionMetadata({ entry.offset, (entry.offset + entry.length), partition_type }));
    }
}

EBRPartitionTable::~EBRPartitionTable()
{
}

}