part_gpt.c

Go to the documentation of this file.

/*
 * PROJECT:     FreeLoader
 * LICENSE:     MIT (https://spdx.org/licenses/MIT)
 * PURPOSE:     GPT partitioning scheme support
 * COPYRIGHT:   Copyright 2026 Justin Miller <justin.miller@reactos.org>
 */
 
/* INCLUDES ******************************************************************/
 
#ifndef _M_ARM
// #include <freeldr.h>
#include "part_gpt.h"
 
// #include <debug.h>
// DBG_DEFAULT_CHANNEL(DISK);
 
 
/* FUNCTIONS *****************************************************************/
 
//static // Used also in uefidisk.c
BOOLEAN
DiskReadGptHeader(
    _In_ UCHAR DriveNumber,
    _Out_ PGPT_TABLE_HEADER GptHeader)
{
    /* Read GPT header (1 sector) from LBA 1 */
    if (!MachDiskReadLogicalSectors(DriveNumber, EFI_HEADER_LOCATION, 1, DiskReadBuffer))
        return FALSE;
    RtlCopyMemory(GptHeader, DiskReadBuffer, sizeof(*GptHeader));
 
    /* Verify GPT signature */
    if (!RtlEqualMemory(GptHeader->Signature, EFI_PARTITION_HEADER_SIGNATURE, 8))
        return FALSE;
 
    /* Verify revision */
    if (GptHeader->Revision != EFI_TABLE_REVISION)
    {
        TRACE("GPT header has unsupported revision: 0x%x\n", GptHeader->Revision);
        return FALSE;
    }
 
    return TRUE;
}
 
BOOLEAN
DiskGetGptPartitionEntry(
    _In_ UCHAR DriveNumber,
    _In_ ULONG SectorSize, // BlockSize
    _In_ ULONG PartitionNumber,
    _Out_ PPARTITION_INFORMATION PartitionEntry)
{
    GPT_TABLE_HEADER GptHeader;
    GPT_PARTITION_ENTRY GptEntry;
    ULONGLONG EntryLba;
    ULONG EntryOffset;
    ULONG EntriesPerBlock;
    GUID UnusedGuid = EFI_PART_TYPE_UNUSED_GUID;
    GUID SystemGuid = EFI_PART_TYPE_EFI_SYSTEM_PART_GUID;
 
    ASSERT(SectorSize >= 512);
 
    /* Read GPT header */
    if (!DiskReadGptHeader(DriveNumber, &GptHeader))
        return FALSE;
 
    /* Validate partition number */
    //if (PartitionNumber == 0 || PartitionNumber > GptHeader.NumberOfPartitionEntries)
    if (!(1 <= PartitionNumber && PartitionNumber <= GptHeader.NumberOfPartitionEntries))
        return FALSE;
 
    /* Convert to 0-based index */
    ULONG EntryIndex = PartitionNumber - 1;
 
    EntriesPerBlock = SectorSize / GptHeader.SizeOfPartitionEntry;
    EntryLba = GptHeader.PartitionEntryLba + (EntryIndex / EntriesPerBlock);
    EntryOffset = (EntryIndex % EntriesPerBlock) * GptHeader.SizeOfPartitionEntry;
 
    /* Read the block containing the partition entry */
    if (!MachDiskReadLogicalSectors(DriveNumber, EntryLba, 1, DiskReadBuffer))
        return FALSE;
 
    /* Extract partition entry */
    RtlCopyMemory(&GptEntry, (PUCHAR)DiskReadBuffer + EntryOffset, sizeof(GptEntry));
 
    /* Check if partition is unused */
    if (RtlEqualMemory(&GptEntry.PartitionTypeGuid, &UnusedGuid, sizeof(UnusedGuid)))
        return FALSE;
 
    /* Calculate partition size in blocks */
    ULONGLONG PartitionSizeBlocks = GptEntry.EndingLba - GptEntry.StartingLba + 1;
 
    /* Convert GPT entry to standard-style entry */
    PartitionEntry->StartingOffset.QuadPart  = (GptEntry.StartingLba * SectorSize);
    PartitionEntry->PartitionLength.QuadPart = (PartitionSizeBlocks * SectorSize);
    PartitionEntry->HiddenSectors = 0;
    PartitionEntry->PartitionNumber = PartitionNumber;
    PartitionEntry->PartitionType = PARTITION_GPT; /* Mark as GPT partition */
    PartitionEntry->BootIndicator = RtlEqualMemory(&GptEntry.PartitionTypeGuid, &SystemGuid, sizeof(SystemGuid));
    PartitionEntry->RecognizedPartition = TRUE;
    PartitionEntry->RewritePartition = FALSE;
 
    return TRUE;
}
 
#endif