ntloader/disk/gpt.c

/*
 *  ntloader  --  Microsoft Windows NT6+ loader
 *  Copyright (C) 2025  A1ive.
 *
 *  ntloader is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published
 *  by the Free Software Foundation, either version 3 of the License,
 *  or (at your option) any later version.
 *
 *  ntloader is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with ntloader.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include "msdos.h"
#include "gpt.h"
#include "fsuuid.h"
#include "cmdline.h"
#include "ntloader.h"

static uint8_t gpt_magic[8] = GPT_HEADER_MAGIC;

static const gpt_part_guid_t gpt_part_type_empty = GPT_PART_TYPE_EMPTY;

int
check_gpt_partmap (void *disk,
                   int (*disk_read) (void *disk, uint64_t sector,
                                     size_t len, void *buf))
{
    uint8_t sector[1024];
    struct gpt_header gpt;
    struct gpt_part_entry entry;
    uint32_t i;

    /* Read the GPT header */
    if (!disk_read (disk, 1, sizeof (gpt), &gpt))
        return 0;

    if (memcmp (gpt.magic, gpt_magic, sizeof (gpt_magic)) != 0)
    {
        DBG ("GPT magic not found\n");
        return 0;
    }

    for (i = 0; i < gpt.maxpart; i++)
    {
        uint64_t entry_ofs = i * gpt.entry_size;
        uint64_t entry_lba = entry_ofs >> 9;
        entry_ofs -= (entry_lba << 9);
        entry_lba += gpt.partitions;
        if (!disk_read (disk, entry_lba, 512, sector) ||
            !disk_read (disk, entry_lba + 1, 512, sector + 512))
            return 0;
        memcpy (&entry, sector + entry_ofs, sizeof (entry));

        if (memcmp (&gpt_part_type_empty, &entry.type, sizeof (entry.type)) == 0)
            continue;

        DBG ("part %d ", i);
        if (check_fsuuid (disk, entry.start, disk_read))
        {
            DBG ("GPT LBA=%lld\n", (unsigned long long)entry.start);
            memcpy (nt_cmdline->partid, &entry.guid, 16);
            nt_cmdline->partmap = 0x00;
            memcpy (nt_cmdline->diskid, &gpt.guid, 16);
            return 1;
        }
    }
    return 0;
}