Partition Table: Add support for Extended partitions

Now also MBR configurations with extended partitions are supported.

Kernel/Devices/EBRPartitionTable.cpp

@@ -0,0 +1,196 @@
+/*
+ * Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/ByteBuffer.h>
+#include <Kernel/Devices/EBRPartitionTable.h>
+
+#define EBR_DEBUG
+
+EBRPartitionTable::EBRPartitionTable(NonnullRefPtr<DiskDevice> device)
+    : m_device(move(device))
+{
+}
+
+EBRPartitionTable::~EBRPartitionTable()
+{
+}
+
+const MBRPartitionHeader& EBRPartitionTable::header() const
+{
+    return *reinterpret_cast<const MBRPartitionHeader*>(m_cached_mbr_header);
+}
+
+const EBRPartitionExtension& EBRPartitionTable::ebr_extension() const
+{
+    return *reinterpret_cast<const EBRPartitionExtension*>(m_cached_ebr_header);
+}
+
+int EBRPartitionTable::index_of_ebr_container() const
+{
+    for (int i = 0; i < 4; i++) {
+        if (header().entry[i].type == EBR_CHS_CONTAINER || header().entry[i].type == EBR_LBA_CONTAINER)
+            return i;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+bool EBRPartitionTable::initialize()
+{
+    if (!m_device->read_block(0, m_cached_mbr_header)) {
+        return false;
+    }
+    auto& header = this->header();
+
+    m_ebr_container_id = index_of_ebr_container() + 1;
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::initialize: MBR_signature=%#x\n", header.mbr_signature);
+#endif
+
+    if (header.mbr_signature != MBR_SIGNATURE) {
+        kprintf("EBRPartitionTable::initialize: bad MBR signature %#x\n", header.mbr_signature);
+        return false;
+    }
+
+    auto& ebr_entry = header.entry[m_ebr_container_id - 1];
+    if (!m_device->read_block(ebr_entry.offset, m_cached_ebr_header)) {
+        return false;
+    }
+    size_t index = 1;
+    while (index < 128) { // Unlikely to encounter a disk with 128 partitions in this configuration...
+        if (ebr_extension().next_chained_ebr_extension.offset == 0 && ebr_extension().next_chained_ebr_extension.type == 0) {
+            break;
+        }
+        index++;
+        if (!m_device->read_block(ebr_extension().next_chained_ebr_extension.offset, m_cached_ebr_header)) {
+            return false;
+        }
+    }
+
+    m_ebr_chained_extensions_count = index;
+
+    kprintf("EBRPartitionTable::initialize: Extended partitions count - %d\n", m_ebr_chained_extensions_count);
+
+    return true;
+}
+
+RefPtr<DiskPartition> EBRPartitionTable::get_non_extended_partition(unsigned index)
+{
+    auto& header = this->header();
+    auto& entry = header.entry[index - 1];
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: status=%#x offset=%#x\n", entry.status, entry.offset);
+#endif
+
+    if (entry.offset == 0x00) {
+#ifdef EBR_DEBUG
+        kprintf("EBRPartitionTable::partition: missing partition requested index=%d\n", index);
+#endif
+
+        return nullptr;
+    }
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: found partition index=%d type=%x\n", index, entry.type);
+#endif
+
+    return DiskPartition::create(m_device, entry.offset, (entry.offset + entry.length));
+}
+
+RefPtr<DiskPartition> EBRPartitionTable::get_extended_partition(unsigned index)
+{
+
+    unsigned relative_index = index - m_ebr_container_id;
+    auto& header = this->header();
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: relative index %d\n", relative_index);
+#endif
+
+    auto& ebr_entry = header.entry[m_ebr_container_id - 1];
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: Extended partition, offset 0x%x, type %x\n", ebr_entry.offset, ebr_entry.type);
+#endif
+
+    if (!m_device->read_block(ebr_entry.offset, m_cached_ebr_header)) {
+        return nullptr;
+    }
+    size_t i = 0;
+    while (i < relative_index) {
+#ifdef EBR_DEBUG
+        kprintf("EBRPartitionTable::partition: logical partition, relative offset 0x%x, type %x\n", ebr_extension().entry.offset, ebr_extension().entry.type);
+        kprintf("EBRPartitionTable::partition: next logical partition, relative offset 0x%x, type %x\n", ebr_extension().next_chained_ebr_extension.offset, ebr_extension().next_chained_ebr_extension.type);
+#endif
+        if (ebr_extension().next_chained_ebr_extension.offset == 0 && ebr_extension().next_chained_ebr_extension.type == 0) {
+            break;
+        }
+
+        i++;
+        if (!m_device->read_block(ebr_extension().next_chained_ebr_extension.offset, m_cached_ebr_header)) {
+            return nullptr;
+        }
+    }
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: status=%#x offset=%#x\n", ebr_extension().entry.status, ebr_extension().entry.offset + ebr_entry.offset);
+#endif
+
+    if (ebr_extension().entry.offset == 0x00) {
+#ifdef EBR_DEBUG
+        kprintf("EBRPartitionTable::partition: missing partition requested index=%d\n", index);
+#endif
+
+        return nullptr;
+    }
+
+#ifdef EBR_DEBUG
+    kprintf("EBRPartitionTable::partition: found partition index=%d type=%x\n", index, ebr_extension().entry.type);
+#endif
+
+    return DiskPartition::create(m_device, ebr_extension().entry.offset + ebr_entry.offset, (ebr_extension().entry.offset + ebr_entry.offset + ebr_extension().entry.length));
+}
+
+bool EBRPartitionTable::index_is_extended_partition(unsigned index) const
+{
+    return !(m_ebr_container_id > index || index > (m_ebr_container_id + m_ebr_chained_extensions_count));
+}
+
+RefPtr<DiskPartition> EBRPartitionTable::partition(unsigned index)
+{
+    ASSERT(index >= 1 && index <= m_ebr_chained_extensions_count + 4);
+
+    auto& header = this->header();
+    if (header.mbr_signature != MBR_SIGNATURE) {
+        kprintf("EBRPartitionTable::initialize: bad MBR signature - not initalized? %#x\n", header.mbr_signature);
+        return nullptr;
+    }
+    if (index_is_extended_partition(index))
+        return get_extended_partition(index);
+    if (index > 4)
+        return get_non_extended_partition(index - m_ebr_chained_extensions_count);
+    return get_non_extended_partition(index);
+}

Kernel/Devices/EBRPartitionTable.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/RefPtr.h>
+#include <AK/Vector.h>
+#include <Kernel/Devices/DiskDevice.h>
+#include <Kernel/Devices/DiskPartition.h>
+#include <Kernel/Devices/MBRPartitionTable.h>
+
+struct [[gnu::packed]] EBRPartitionExtension
+{
+    u8 unused_area[446];
+    MBRPartitionEntry entry;
+    MBRPartitionEntry next_chained_ebr_extension;
+    MBRPartitionEntry unused[2];
+    u16 mbr_signature;
+};
+
+class EBRPartitionTable {
+
+public:
+    explicit EBRPartitionTable(NonnullRefPtr<DiskDevice>);
+    ~EBRPartitionTable();
+
+    bool initialize();
+    RefPtr<DiskPartition> partition(unsigned index);
+
+private:
+    int index_of_ebr_container() const;
+    NonnullRefPtr<DiskDevice> m_device;
+
+    const MBRPartitionHeader& header() const;
+    const EBRPartitionExtension& ebr_extension() const;
+
+    bool index_is_extended_partition(unsigned index) const;
+
+    RefPtr<DiskPartition> get_extended_partition(unsigned index);
+    RefPtr<DiskPartition> get_non_extended_partition(unsigned index);
+    u8 m_ebr_container_id { 0 };
+    size_t m_ebr_chained_extensions_count { 0 };
+    u8 m_cached_mbr_header[512];
+    u8 m_cached_ebr_header[512];
+};

Kernel/Devices/MBRPartitionTable.cpp

@@ -63,6 +63,15 @@ bool MBRPartitionTable::initialize()
     return true;
 }
 
+bool MBRPartitionTable::contains_ebr() const
+{
+    for (int i = 0; i < 4; i++) {
+        if (header().entry[i].type == EBR_CHS_CONTAINER || header().entry[i].type == EBR_LBA_CONTAINER)
+            return true;
+    }
+    return false;
+}
+
 bool MBRPartitionTable::is_protective_mbr() const
 {
     return header().entry[0].type == MBR_PROTECTIVE;

Kernel/Devices/MBRPartitionTable.h

@@ -33,6 +33,8 @@
 
 #define MBR_SIGNATURE 0xaa55
 #define MBR_PROTECTIVE 0xEE
+#define EBR_CHS_CONTAINER 0x05
+#define EBR_LBA_CONTAINER 0x0F
 
 struct [[gnu::packed]] MBRPartitionEntry
 {
@@ -60,11 +62,12 @@ class MBRPartitionTable {
     AK_MAKE_ETERNAL
 
 public:
-    MBRPartitionTable(NonnullRefPtr<DiskDevice>);
+    explicit MBRPartitionTable(NonnullRefPtr<DiskDevice>);
     ~MBRPartitionTable();
 
     bool initialize();
     bool is_protective_mbr() const;
+    bool contains_ebr() const;
     RefPtr<DiskPartition> partition(unsigned index);
 
 private:

Kernel/Makefile

@@ -25,6 +25,7 @@ OBJS = \
     Devices/FloppyDiskDevice.o \
     Devices/FullDevice.o \
     Devices/GPTPartitionTable.o \
+    Devices/EBRPartitionTable.o \
     Devices/KeyboardDevice.o \
     Devices/MBRPartitionTable.o \
     Devices/MBVGADevice.o \

Kernel/init.cpp

@@ -42,6 +42,7 @@
 #include <Kernel/Devices/BXVGADevice.h>
 #include <Kernel/Devices/DebugLogDevice.h>
 #include <Kernel/Devices/DiskPartition.h>
+#include <Kernel/Devices/EBRPartitionTable.h>
 #include <Kernel/Devices/FloppyDiskDevice.h>
 #include <Kernel/Devices/FullDevice.h>
 #include <Kernel/Devices/GPTPartitionTable.h>
@@ -273,6 +274,19 @@ void init_stage2()
             root_dev = *partition;
         } else {
             dbgprintf("MBR Partitioned Storage Detected!\n");
+            if (mbr.contains_ebr()) {
+                EBRPartitionTable ebr(root_dev);
+                if (!ebr.initialize()) {
+                    kprintf("init_stage2: couldn't read EBR from disk\n");
+                    hang();
+                }
+                auto partition = ebr.partition(partition_number);
+                if (!partition) {
+                    kprintf("init_stage2: couldn't get partition %d\n", partition_number);
+                    hang();
+                }
+                root_dev = *partition;
+            } else {
                 if (partition_number < 1 || partition_number > 4) {
                     kprintf("init_stage2: invalid partition number %d; expected 1 to 4\n", partition_number);
                     hang();
@@ -285,6 +299,7 @@ void init_stage2()
                 root_dev = *partition;
             }
         }
+    }
 
     auto e2fs = Ext2FS::create(root_dev);
     if (!e2fs->initialize()) {