/*      $NetBSD: subr_disk_mbr.c,v 1.62 2026/07/14 13:34:37 thorpej Exp $       */

/*
 * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      @(#)ufs_disksubr.c      7.16 (Berkeley) 5/4/91
 */

/*
 * Code to find a NetBSD label on a disk that contains an i386 style MBR.
 * The first NetBSD label found in the 2nd sector of a NetBSD partition
 * is used.
 * If we don't find a label searching the MBR, we look at the start of the
 * disk, if that fails then a label is faked up from the MBR.
 *
 * If there isn't a disklabel or anything in the MBR then the disc is searched
 * for ecma-167/iso9660/udf style partition indicators.
 * Useful for media or files that contain single filesystems (etc).
 *
 * This code will read host endian netbsd labels from little endian MBR.
 *
 * Based on the i386 disksubr.c
 *
 * Since the mbr only has 32bit fields for sector addresses, we do the same.
 *
 * XXX There are potential problems writing labels to disks where there
 * is only space for 8 netbsd partitions but this code has been compiled
 * with MAXPARTITIONS=16.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_disk_mbr.c,v 1.62 2026/07/14 13:34:37 thorpej Exp $");

#ifdef _KERNEL_OPT
#include "opt_mbr.h"
#include "opt_disklabel.h"
#endif /* _KERNEL_OPT */

#include <sys/param.h>
#include <sys/types.h>

#include <sys/bootblock.h>
#include <sys/buf.h>
#include <sys/cdio.h>
#include <sys/conf.h>
#include <sys/disk.h>
#include <sys/disklabel.h>
#include <sys/fcntl.h>
#include <sys/kauth.h>
#include <sys/sdt.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/vnode.h>

#include <fs/udf/ecma167-udf.h>

typedef struct mbr_partition mbr_partition_t;

/*
 * We allocate a buffer 3 sectors large, and look in all....
 * That means we find labels written by other ports with different offsets.
 * LABELSECTOR and LABELOFFSET are only used if the disk doesn't have a label.
 */
#define SCANBLOCKS 3
#define DISKLABEL_SIZE 404
#if LABELSECTOR*DEV_BSIZE + LABELOFFSET > SCANBLOCKS*DEV_BSIZE - DISKLABEL_SIZE
#if _MACHINE != ews4800mips /* XXX: fail silently, ews4800mips LABELSECTOR */
#error Invalid LABELSECTOR or LABELOFFSET
#endif
#endif

#define MBR_LABELSECTOR 1

#define SCAN_CONTINUE   0
#define SCAN_FOUND      1
#define SCAN_ERROR      2

typedef struct mbr_args {
        struct disklabel *lp;
        void            (*strat)(struct buf *);
        struct buf      *bp;
        const char      *msg;
        int             error;
        int             written;        /* number of times we wrote label */
        int             found_mbr;      /* set if disk has a valid mbr */
        uint            label_sector;   /* where we found the label */
        int             action;
        uint32_t        secperunit;
#define READ_LABEL      1
#define UPDATE_LABEL    2
#define WRITE_LABEL     3
} mbr_args_t;

static int validate_label(mbr_args_t *, uint);
static int look_netbsd_part(mbr_args_t *, mbr_partition_t *, int, uint);
static int write_netbsd_label(mbr_args_t *, mbr_partition_t *, int, uint);

static int
read_sector(mbr_args_t *a, uint sector, int count)
{
        int error;

        error = disk_read_sectors(a->strat, a->lp, a->bp, sector, count);
        if (error != 0)
                a->error = error;
        return error;
}

/*
 * Scan MBR for partitions, call 'action' routine for each.
 */

static int
scan_mbr(mbr_args_t *a, int (*actn)(mbr_args_t *, mbr_partition_t *, int, uint))
{
        mbr_partition_t ptns[MBR_PART_COUNT];
        mbr_partition_t *dp;
        struct mbr_sector *mbr;
        uint ext_base, this_ext, next_ext;
        int rval;
        int i;
        int j;
#ifdef COMPAT_386BSD_MBRPART
        int dp_386bsd = -1;
        int ap_386bsd = -1;
#endif

        ext_base = 0;
        this_ext = 0;
        for (;;) {
                if (read_sector(a, this_ext, 1)) {
                        a->msg = "dos partition I/O error";
                        return SCAN_ERROR;
                }

                /* Note: Magic number is little-endian. */
                mbr = (void *)a->bp->b_data;
                if (mbr->mbr_magic != htole16(MBR_MAGIC))
                        return SCAN_CONTINUE;

                /*
                 * If this is a protective MBR, bail now.
                 */
                if (mbr->mbr_parts[0].mbrp_type == MBR_PTYPE_PMBR
                    && mbr->mbr_parts[1].mbrp_type == MBR_PTYPE_UNUSED
                    && mbr->mbr_parts[2].mbrp_type == MBR_PTYPE_UNUSED
                    && mbr->mbr_parts[3].mbrp_type == MBR_PTYPE_UNUSED)
                        return SCAN_CONTINUE;

                /* Copy data out of buffer so action can use bp */
                memcpy(ptns, &mbr->mbr_parts, sizeof ptns);

                /* Look for drivers and skip them */
                if (ext_base == 0 && ptns[0].mbrp_type == MBR_PTYPE_DM6_DDO) {
                        /* We've found a DM6 DDO partition type (used by
                         * the Ontrack Disk Manager drivers).
                         *
                         * Ensure that there are no other partitions in the
                         * MBR and jump to the real partition table (stored
                         * in the first sector of the second track). */
                        bool ok = true;

                        for (i = 1; i < MBR_PART_COUNT; i++)
                                if (ptns[i].mbrp_type != MBR_PTYPE_UNUSED)
                                        ok = false;

                        if (ok) {
                                this_ext = le32toh(a->lp->d_secpercyl /
                                    a->lp->d_ntracks);
                                continue;
                        }
                }

                /* look for NetBSD partition */
                next_ext = 0;
                dp = ptns;
                j = 0;
                for (i = 0; i < MBR_PART_COUNT; i++, dp++) {
                        if (dp->mbrp_type == MBR_PTYPE_UNUSED)
                                continue;
                        /* Check end of partition is inside disk limits */
                        if ((uint64_t)ext_base + le32toh(dp->mbrp_start) +
                            le32toh(dp->mbrp_size) > a->lp->d_secperunit) {
                                /* This mbr doesn't look good.... */
                                a->msg = "mbr partition exceeds disk size";
                                /* ...but don't report this as an error (yet) */
                                return SCAN_CONTINUE;
                        }
                        a->found_mbr = 1;
                        if (MBR_IS_EXTENDED(dp->mbrp_type)) {
                                next_ext = le32toh(dp->mbrp_start);
                                continue;
                        }
#ifdef COMPAT_386BSD_MBRPART
                        if (dp->mbrp_type == MBR_PTYPE_386BSD) {
                                /*
                                 * If more than one matches, take last,
                                 * as NetBSD install tool does.
                                 */
                                if (this_ext == 0) {
                                        dp_386bsd = i;
                                        ap_386bsd = j;
                                }
                                continue;
                        }
#endif
                        rval = (*actn)(a, dp, j, this_ext);
                        if (rval != SCAN_CONTINUE)
                                return rval;
                        j++;
                }
                if (next_ext == 0)
                        break;
                if (ext_base == 0) {
                        ext_base = next_ext;
                        next_ext = 0;
                }
                next_ext += ext_base;
                if (next_ext <= this_ext)
                        break;
                this_ext = next_ext;
        }
#ifdef COMPAT_386BSD_MBRPART
        if (this_ext == 0 && dp_386bsd != -1)
                return (*actn)(a, &ptns[dp_386bsd], ap_386bsd, 0);
#endif
        return SCAN_CONTINUE;
}


static void
scan_iso_vrs_session(mbr_args_t *a, uint32_t first_sector,
        int *is_iso9660, int *is_udf)
{
        struct vrs_desc *vrsd;
        uint64_t vrs;
        int sector_size;
        int inc;

        sector_size = a->lp->d_secsize;
        inc  = MAX(1, 2048 / sector_size);

        /* by definition */
        vrs = ((32*1024 + sector_size - 1) / sector_size)
                + first_sector;

        /* read first vrs sector */
        if (read_sector(a, vrs, 1))
                return;

        /* skip all CD001 records */
        vrsd = a->bp->b_data;
        /* printf("vrsd->identifier = `%s`\n", vrsd->identifier); */
        while (memcmp(vrsd->identifier, "CD001", 5) == 0) {
                /* for sure */
                *is_iso9660 = first_sector;

                vrs += inc;
                if (read_sector(a, vrs, 1))
                        return;
        }

        /* search for BEA01 */
        vrsd = a->bp->b_data;
        /* printf("vrsd->identifier = `%s`\n", vrsd->identifier); */
        if (memcmp(vrsd->identifier, "BEA01", 5))
                return;

        /* read successor */
        vrs += inc;
        if (read_sector(a, vrs, 1))
                return;

        /* check for NSR[23] */
        vrsd = a->bp->b_data;
        /* printf("vrsd->identifier = `%s`\n", vrsd->identifier); */
        if (memcmp(vrsd->identifier, "NSR0", 4))
                return;

        *is_udf = first_sector;
}


/*
 * Scan for ISO Volume Recognition Sequences
 */

static int
scan_iso_vrs(mbr_args_t *a)
{
        struct mmc_discinfo  di;
        struct mmc_trackinfo ti;
        dev_t dev;
        uint64_t sector;
        int is_iso9660, is_udf;
        int tracknr, sessionnr;
        int new_session, error;

        is_iso9660 = is_udf = -1;

        /* parse all sessions of disc if we're on a SCSI MMC device */
        if (a->lp->d_flags & D_SCSI_MMC) {
                /* get disc info */
                dev = a->bp->b_dev;
                error = bdev_ioctl(dev, MMCGETDISCINFO, &di, FKIOCTL, curlwp);
                if (error)
                        goto notmmc;

                /* go through all (data) tracks */
                sessionnr = -1;
                for (tracknr = di.first_track;
                    tracknr <= di.first_track_last_session; tracknr++)
                {
                        ti.tracknr = tracknr;
                        error = bdev_ioctl(dev, MMCGETTRACKINFO, &ti,
                                        FKIOCTL, curlwp);
                        if (error)
                                goto notmmc;
                        new_session = (ti.sessionnr != sessionnr);
                        sessionnr = ti.sessionnr;
                        if (new_session) {
                                if (ti.flags & MMC_TRACKINFO_BLANK)
                                        continue;
                                if (!(ti.flags & MMC_TRACKINFO_DATA))
                                        continue;
                                sector = ti.track_start;
                                scan_iso_vrs_session(a, sector,
                                        &is_iso9660, &is_udf);
                        }
                }
        } else {
notmmc:
                /* try start of disc */
                sector = 0;
                scan_iso_vrs_session(a, sector, &is_iso9660, &is_udf);
        }

        if ((is_iso9660 < 0) && (is_udf < 0))
                return SCAN_CONTINUE;

        strncpy(a->lp->d_typename, "iso partition", 16);

        /* adjust session information for iso9660 partition */
        if (is_iso9660 >= 0) {
                /* set 'a' partition to iso9660 */
                a->lp->d_partitions[0].p_offset = 0;
                a->lp->d_partitions[0].p_size   = a->lp->d_secperunit;
                a->lp->d_partitions[0].p_cdsession = is_iso9660;
                a->lp->d_partitions[0].p_fstype = FS_ISO9660;
        }

        /* UDF doesn't care about the cd session specified here */

        return SCAN_FOUND;
}


/*
 * Attempt to read a disk label from a device
 * using the indicated strategy routine.
 * The label must be partly set up before this:
 * secpercyl, secsize and anything required for a block i/o read
 * operation in the driver's strategy/start routines
 * must be filled in before calling us.
 *
 * If dos partition table requested, attempt to load it and
 * find disklabel inside a DOS partition. Also, if bad block
 * table needed, attempt to extract it as well. Return buffer
 * for use in signalling errors if requested.
 *
 * Returns null on success and an error string on failure.
 */
const char *
readdisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel *lp,
    struct cpu_disklabel *osdep)
{
        int rval;
        int i;
        mbr_args_t a;

        memset(&a, 0, sizeof a);
        a.lp = lp;
        a.strat = strat;
        a.action = READ_LABEL;

        /* minimal requirements for architypal disk label */
        if (lp->d_secsize == 0)
                lp->d_secsize = DEV_BSIZE;
        if (lp->d_secperunit == 0)
                lp->d_secperunit = 0x1fffffff;
        a.secperunit = lp->d_secperunit;
        lp->d_npartitions = RAW_PART + 1;
        for (i = 0; i < RAW_PART; i++) {
                lp->d_partitions[i].p_size = 0;
                lp->d_partitions[i].p_offset = 0;
        }
        if (lp->d_partitions[RAW_PART].p_size == 0)
                lp->d_partitions[RAW_PART].p_size = lp->d_secperunit;
        lp->d_partitions[RAW_PART].p_offset = 0;

        /*
         * Set partition 'a' to be the whole disk.
         * Cleared if we find an mbr or a netbsd label.
         */
        lp->d_partitions[0].p_size = lp->d_partitions[RAW_PART].p_size;
        lp->d_partitions[0].p_fstype = FS_BSDFFS;

        /*
         * Get a buffer big enough to read a disklabel in and initialize it
         * make it three sectors long for the validate_label(); see comment at
         * start of file.
         */
        a.bp = geteblk(SCANBLOCKS * (int)lp->d_secsize);
        a.bp->b_dev = dev;

        if (osdep)
                /*
                 * Scan mbr searching for netbsd partition and saving
                 * bios partition information to use if the netbsd one
                 * is absent.
                 */
                rval = scan_mbr(&a, look_netbsd_part);
        else
                rval = SCAN_CONTINUE;

        if (rval == SCAN_CONTINUE) {
                /* Look at start of disk */
                rval = validate_label(&a, 0);
        }

        if (rval == SCAN_CONTINUE) {
                rval = scan_iso_vrs(&a);
        }
#if 0
        /*
         * Save sector where we found the label for the 'don't overwrite
         * the label' check in bounds_check_with_label.
         */
        if (rval == SCAN_FOUND)
                xxx->label_sector = a.label_sector;
#endif

        brelse(a.bp, 0);
        if (rval == SCAN_ERROR || rval == SCAN_CONTINUE)
                return a.msg;
        return NULL;
}

static int
look_netbsd_part(mbr_args_t *a, mbr_partition_t *dp, int slot, uint ext_base)
{
        struct partition *pp;
        int ptn_base = ext_base + le32toh(dp->mbrp_start);
        int rval;

        if (
#ifdef COMPAT_386BSD_MBRPART
            dp->mbrp_type == MBR_PTYPE_386BSD ||
#endif
            dp->mbrp_type == MBR_PTYPE_NETBSD) {
                rval = validate_label(a, ptn_base);

#if RAW_PART == 3
                /* Put actual location where we found the label into ptn 2 */
                if (rval == SCAN_FOUND || a->lp->d_partitions[2].p_size == 0) {
                        a->lp->d_partitions[2].p_size = le32toh(dp->mbrp_size);
                        a->lp->d_partitions[2].p_offset = ptn_base;
                }
#endif

                /* If we got a netbsd label look no further */
                if (rval == SCAN_FOUND)
                        return rval;
        }

        /* Install main partitions into e..h and extended into i+ */
        if (ext_base == 0)
                slot += 4;
        else {
                slot = 4 + MBR_PART_COUNT;
                pp = &a->lp->d_partitions[slot];
                for (; slot < MAXPARTITIONS; pp++, slot++) {
                        /* This gets called twice - avoid duplicates */
                        if (pp->p_offset == ptn_base &&
                            pp->p_size == le32toh(dp->mbrp_size))
                                break;
                        if (pp->p_size == 0)
                                break;
                }
        }

        if (slot < MAXPARTITIONS) {
                /* Stop 'a' being the entire disk */
                a->lp->d_partitions[0].p_size = 0;
                a->lp->d_partitions[0].p_fstype = 0;

                /* save partition info */
                pp = &a->lp->d_partitions[slot];
                pp->p_offset = ptn_base;
                pp->p_size = le32toh(dp->mbrp_size);
                pp->p_fstype = xlat_mbr_fstype(dp->mbrp_type);

                if (slot >= a->lp->d_npartitions)
                        a->lp->d_npartitions = slot + 1;
        }

        return SCAN_CONTINUE;
}

__noubsan
static bool
check_label_magic(const struct disklabel *dlp, uint32_t diskmagic)
{
        return memcmp(&dlp->d_magic, &diskmagic, sizeof(diskmagic)) == 0 &&
            memcmp(&dlp->d_magic2, &diskmagic, sizeof(diskmagic)) == 0;
}

#ifdef DISKLABEL_EI
/*
 * - For read, convert a label to the native byte order.
 * - For update or write, if a label already exists, keep its byte order.
 *   Otherwise, write a new label in the native byte order.
 */
#endif
static int
validate_label(mbr_args_t *a, uint label_sector)
{
        struct disklabel *dlp;
        char *dlp_lim, *dlp_byte;
        int error;
#ifdef DISKLABEL_EI
        int swapped = 0;
        uint16_t npartitions;
#endif

        /* Next, dig out disk label */
        if (read_sector(a, label_sector, SCANBLOCKS)) {
                a->msg = "disk label read failed";
                return SCAN_ERROR;
        }

        /* Locate disk label within block and validate */
        /*
         * XXX (dsl) This search may be a waste of time, a lot of other i386
         * code assumes the label is at offset LABELOFFSET (=0) in the sector.
         *
         * If we want to support disks from other netbsd ports, then the
         * code should also allow for a shorter label nearer the end of
         * the disk sector, and (IIRC) labels within 8k of the disk start.
         */
        dlp = (void *)a->bp->b_data;
        dlp_lim = (char *)a->bp->b_data + a->bp->b_bcount - sizeof *dlp;
        for (;; dlp = (void *)((char *)dlp + sizeof(uint32_t))) {
                if ((char *)dlp > dlp_lim) {
                        if (a->action != WRITE_LABEL)
                                return SCAN_CONTINUE;
                        /* Write at arch. dependent default location */
                        dlp_byte = (char *)a->bp->b_data + LABELOFFSET;
                        if (label_sector)
                                dlp_byte += MBR_LABELSECTOR * a->lp->d_secsize;
                        else
                                dlp_byte += LABELSECTOR * a->lp->d_secsize;
                        dlp = (void *)dlp_byte;
                        break;
                }
                if (!check_label_magic(dlp, DISKMAGIC))
#ifdef DISKLABEL_EI
                {
                        if (!check_label_magic(dlp, bswap32(DISKMAGIC)))
                                continue;

                        /*
                         * The label is in the other byte order. We need to
                         * checksum before swapping the byte order.
                         */
                        npartitions = bswap16(dlp->d_npartitions);
                        if (npartitions > MAXPARTITIONS ||
                            dkcksum_sized(dlp, npartitions) != 0)
                                goto corrupted;

                        swapped = 1;
                }
#else
                        continue;
#endif
                else if (dlp->d_npartitions > MAXPARTITIONS ||
                         dkcksum(dlp) != 0) {
#ifdef DISKLABEL_EI
corrupted:
#endif
                        a->msg = "disk label corrupted";
                        continue;
                }
                break;
        }

        switch (a->action) {
        case READ_LABEL:
#ifdef DISKLABEL_EI
                if (swapped)
                        disklabel_swap(a->lp, dlp);
                else
                        *a->lp = *dlp;
#else
                *a->lp = *dlp;
#endif
                if ((a->msg = convertdisklabel(a->lp, a->strat, a->bp,
                                              a->secperunit)) != NULL)
                        return SCAN_ERROR;
                a->label_sector = label_sector;
                return SCAN_FOUND;
        case UPDATE_LABEL:
        case WRITE_LABEL:
#ifdef DISKLABEL_EI
                /* DO NOT swap a->lp itself for later references. */
                if (swapped)
                        disklabel_swap(dlp, a->lp);
                else
                        *dlp = *a->lp;
#else
                *dlp = *a->lp;
#endif
                a->bp->b_oflags &= ~BO_DONE;
                a->bp->b_flags &= ~B_READ;
                a->bp->b_flags |= B_WRITE;
                (*a->strat)(a->bp);
                error = biowait(a->bp);
                if (error != 0) {
                        a->error = error;
                        a->msg = "disk label write failed";
                        return SCAN_ERROR;
                }
                a->written++;
                /* Write label to all mbr partitions */
                return SCAN_CONTINUE;
        default:
                return SCAN_ERROR;
        }
}

/*
 * Write disk label back to device after modification.
 */
int
writedisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel *lp,
    struct cpu_disklabel *osdep)
{
        mbr_args_t a;

        memset(&a, 0, sizeof a);
        a.lp = lp;
        a.strat = strat;

        /* get a buffer and initialize it */
        a.bp = geteblk(SCANBLOCKS * (int)lp->d_secsize);
        a.bp->b_dev = dev;

        /* osdep => we expect an mbr with label in netbsd ptn */
        a.action = osdep != NULL ? WRITE_LABEL : UPDATE_LABEL;

        /* Write/update the label to every netbsd mbr partition */
        scan_mbr(&a, write_netbsd_label);

        /* Old write the label at the start of the volume on disks that
         * don't have a valid mbr (always update an existing one) */
        a.action = a.found_mbr ? UPDATE_LABEL : WRITE_LABEL;
        validate_label(&a, 0);

        if (a.written == 0 && a.error == 0)
                a.error = SET_ERROR(ESRCH);

        brelse(a.bp, 0);
        return a.error;
}

static int
write_netbsd_label(mbr_args_t *a, mbr_partition_t *dp, int slot, uint ext_base)
{
        int ptn_base = ext_base + le32toh(dp->mbrp_start);

        if (dp->mbrp_type != MBR_PTYPE_NETBSD)
                return SCAN_CONTINUE;

        return validate_label(a, ptn_base);
}