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Kernel: Implement MBR partition loader (#168)

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This implements a basic MBR partition loader, which removes the reliance
on a hard-coded filesystem offset in the stage2 init.
This commit is contained in:
Conrad Pankoff 2019-06-02 22:57:44 +10:00 • committed by Andreas Kling
parent 466a817950
commit c02b8b715d
4 changed files with 133 additions and 9 deletions
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61
Kernel/Devices/MBRPartitionTable.cpp Normal file
View file

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#include <AK/ByteBuffer.h>
#include <Kernel/Devices/MBRPartitionTable.h>
#define MBR_DEBUG
MBRPartitionTable::MBRPartitionTable(Retained<DiskDevice>&& device)
: m_device(move(device))
{
}
MBRPartitionTable::~MBRPartitionTable()
{
}
const MBRPartitionHeader& MBRPartitionTable::header() const
{
return *reinterpret_cast<const MBRPartitionHeader*>(m_cached_header);
}
bool MBRPartitionTable::initialize()
{
if (!m_device->read_block(0, m_cached_header)) {
return false;
}
auto& header = this->header();
#ifdef MBR_DEBUG
kprintf("MBRPartitionTable::initialize: mbr_signature=%#x\n", header.mbr_signature);
#endif
if (header.mbr_signature != MBR_SIGNATURE) {
kprintf("MBRPartitionTable::initialize: bad mbr signature %#x\n", header.mbr_signature);
return false;
}
return true;
}
RetainPtr<DiskPartition> MBRPartitionTable::partition(unsigned index)
{
ASSERT(index >= 1 && index <= 4);
auto& header = this->header();
auto& entry = header.entry[index - 1];
if (header.mbr_signature != MBR_SIGNATURE) {
kprintf("MBRPartitionTable::initialize: bad mbr signature - not initalized? %#x\n", header.mbr_signature);
return nullptr;
}
#ifdef MBR_DEBUG
kprintf("MBRPartitionTable::partition: status=%#x offset=%#x\n", entry.status, entry.offset);
#endif
if (entry.status == 0x00) {
return nullptr;
}
return DiskPartition::create(m_device.copy_ref(), entry.offset);
}