Kernel: Introduce a new partitioning subsystem

The partitioning code was very outdated, and required a full refactor.
The new subsystem removes duplicated code and uses more AK containers.

The most important change is that all implementations of the
PartitionTable class conform to one interface, which made it possible
to remove unnecessary code in the EBRPartitionTable class.

Finding partitions is now done in the StorageManagement singleton,
instead of doing so in init.cpp.

Also, now we don't try to find partitions on demand - the kernel will
try to detect if a StorageDevice is partitioned, and if so, will check
what is the partition table, which could be MBR, GUID or EBR.
Then, it will create DiskPartitionMetadata object for each partition
that is available in the partition table. This object will be used
by the partition enumeration code to create a DiskPartition with the
correct minor number.

Kernel/Storage/Partition/MBRPartitionTable.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -33,38 +33,105 @@
 
 namespace Kernel {
 
-MBRPartitionTable::MBRPartitionTable(NonnullRefPtr<BlockDevice> device)
-    : m_device(move(device))
+#define MBR_SIGNATURE 0xaa55
+#define MBR_PROTECTIVE 0xEE
+#define EBR_CHS_CONTAINER 0x05
+#define EBR_LBA_CONTAINER 0x0F
+
+Result<NonnullOwnPtr<MBRPartitionTable>, PartitionTable::Error> MBRPartitionTable::try_to_initialize(const StorageDevice& device)
 {
+    auto table = make<MBRPartitionTable>(device);
+    if (table->contains_ebr())
+        return { PartitionTable::Error::ConatinsEBR };
+    if (table->is_protective_mbr())
+        return { PartitionTable::Error::MBRProtective };
+    if (!table->is_valid())
+        return { PartitionTable::Error::Invalid };
+    return table;
+}
+
+OwnPtr<MBRPartitionTable> MBRPartitionTable::try_to_initialize(const StorageDevice& device, u32 start_lba)
+{
+    auto table = make<MBRPartitionTable>(device, start_lba);
+    if (!table->is_valid())
+        return nullptr;
+    return table;
+}
+
+bool MBRPartitionTable::read_boot_record()
+{
+    auto buffer = UserOrKernelBuffer::for_kernel_buffer(m_cached_header.data());
+    if (!m_device->read_block(m_start_lba, buffer))
+        return false;
+    m_header_valid = true;
+    return m_header_valid;
+}
+
+MBRPartitionTable::MBRPartitionTable(const StorageDevice& device, u32 start_lba)
+    : PartitionTable(device)
+    , m_start_lba(start_lba)
+    , m_cached_header(ByteBuffer::create_zeroed(m_device->block_size()))
+{
+    if (!read_boot_record() || !initialize())
+        return;
+
+    m_header_valid = true;
+
+    auto& header = this->header();
+    for (size_t index = 0; index < 4; index++) {
+        auto& entry = header.entry[index];
+        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 }));
+    }
+    m_valid = true;
+}
+
+MBRPartitionTable::MBRPartitionTable(const StorageDevice& device)
+    : PartitionTable(device)
+    , m_start_lba(0)
+    , m_cached_header(ByteBuffer::create_zeroed(m_device->block_size()))
+{
+    if (!read_boot_record() || contains_ebr() || is_protective_mbr() || !initialize())
+        return;
+
+    auto& header = this->header();
+    for (size_t index = 0; index < 4; index++) {
+        auto& entry = header.entry[index];
+        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 }));
+    }
+    m_valid = true;
 }
 
 MBRPartitionTable::~MBRPartitionTable()
 {
 }
 
-const MBRPartitionHeader& MBRPartitionTable::header() const
+const MBRPartitionTable::Header& MBRPartitionTable::header() const
 {
-    return *reinterpret_cast<const MBRPartitionHeader*>(m_cached_header);
+    return *(const MBRPartitionTable::Header*)m_cached_header.data();
 }
 
 bool MBRPartitionTable::initialize()
 {
-    auto header_buffer = UserOrKernelBuffer::for_kernel_buffer(m_cached_header);
-    if (!m_device->read_block(0, header_buffer)) {
-        return false;
-    }
-
     auto& header = this->header();
-
 #ifdef MBR_DEBUG
-    klog() << "MBRPartitionTable::initialize: mbr_signature=0x" << String::format("%x", header.mbr_signature);
-#endif
 
+    klog() << "Master Boot Record: mbr_signature=0x" << String::format("%x", header.mbr_signature);
+
+#endif
     if (header.mbr_signature != MBR_SIGNATURE) {
-        klog() << "MBRPartitionTable::initialize: bad mbr signature 0x" << String::format("%x", header.mbr_signature);
+        klog() << "Master Boot Record: invalid signature";
         return false;
     }
-
     return true;
 }
 
@@ -82,35 +149,4 @@ bool MBRPartitionTable::is_protective_mbr() const
     return header().entry[0].type == MBR_PROTECTIVE;
 }
 
-RefPtr<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) {
-        klog() << "MBRPartitionTable::initialize: bad mbr signature - not initialized? 0x" << String::format("%x", header.mbr_signature);
-        return nullptr;
-    }
-
-#ifdef MBR_DEBUG
-    klog() << "MBRPartitionTable::partition: status=0x" << String::format("%x", entry.status) << " offset=0x" << String::format("%x", entry.offset);
-#endif
-
-    if (entry.offset == 0x00) {
-#ifdef MBR_DEBUG
-        klog() << "MBRPartitionTable::partition: missing partition requested index=" << index;
-#endif
-
-        return nullptr;
-    }
-
-#ifdef MBR_DEBUG
-    klog() << "MBRPartitionTable::partition: found partition index=" << index << " type=" << String::format("%x", entry.type);
-#endif
-
-    return DiskPartition::create(m_device, entry.offset, (entry.offset + entry.length));
-}
-
 }