/* $NetBSD: disksubr.c,v 1.2 2019/04/03 22:10:50 christos 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: disksubr.c,v 1.2 2019/04/03 22:10:50 christos Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/disklabel.h>
#include <sys/disk.h>
#include <sys/syslog.h>

#define	NO_MBR_SIGNATURE ((struct mbr_partition *) -1)

static struct mbr_partition *
mbr_findslice(struct mbr_partition* dp, struct buf *bp);

/*
 * Scan MBR for NetBSD partittion.  Return NO_MBR_SIGNATURE if no MBR found
 * Otherwise, copy valid MBR partition-table into dp, and if a NetBSD
 * partition is found, return a pointer to it; else return  NULL.
 */
static
struct mbr_partition *
mbr_findslice(struct mbr_partition *dp, struct buf *bp)
{
	struct mbr_partition *ourdp = NULL;
	uint16_t *mbrmagicp;
	int i;

	/* Note: Magic number is little-endian. */
	mbrmagicp = (uint16_t *)((char *)bp->b_data + MBR_MAGIC_OFFSET);
	if (*mbrmagicp != MBR_MAGIC)
		return (NO_MBR_SIGNATURE);

	/* XXX how do we check veracity/bounds of this? */
	memcpy(dp, (char *)bp->b_data + MBR_PART_OFFSET, MBR_PART_COUNT * sizeof(*dp));

	/* look for NetBSD partition */
	for (i = 0; i < MBR_PART_COUNT; i++) {
		if (dp[i].mbrp_type == MBR_PTYPE_NETBSD) {
			ourdp = &dp[i];
			break;
		}
	}

	return (ourdp);
}


/*
 * 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)
{
	struct mbr_partition *dp;
	struct partition *pp;
	struct dkbad *bdp;
	struct buf *bp;
	struct disklabel *dlp;
	const char *msg = NULL;
	int dospartoff, cyl, i;

	/* minimal requirements for archtypal disk label */
	if (lp->d_secsize == 0)
		lp->d_secsize = DEV_BSIZE;
	if (lp->d_secperunit == 0)
		lp->d_secperunit = 0x1fffffff;
#if 0
	if (lp->d_ncylinders == 16383) {
		printf("disklabel: Disk > 8G ... readjusting chs %d/%d/%d to ",
			lp->d_ncylinders, lp->d_ntracks, lp->d_nsectors);
		lp->d_ncylinders = lp->d_secperunit /  lp->d_ntracks / lp->d_nsectors;
		printf("%d/%d/%d\n",
			lp->d_ncylinders, lp->d_ntracks, lp->d_nsectors);
	}
#endif
	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[i].p_size == 0)
		lp->d_partitions[i].p_size = 0x1fffffff;
	lp->d_partitions[i].p_offset = 0;

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

	/* do dos partitions in the process of getting disklabel? */
	dospartoff = 0;
	cyl = LABELSECTOR / lp->d_secpercyl;
	if (!osdep)
		goto nombrpart;
	dp = osdep->mbrparts;

	/* read master boot record */
	bp->b_blkno = MBR_BBSECTOR;
	bp->b_bcount = lp->d_secsize;
	bp->b_cflags = BC_BUSY;
	bp->b_flags |= B_READ;
	bp->b_cylinder = MBR_BBSECTOR / lp->d_secpercyl;
	(*strat)(bp);

	/* if successful, wander through dos partition table */
	if (biowait(bp)) {
		msg = "dos partition I/O error";
		goto done;
	} else {
		struct mbr_partition *ourdp = NULL;

		ourdp = mbr_findslice(dp, bp);
		if (ourdp ==  NO_MBR_SIGNATURE)
			goto nombrpart;

		for (i = 0; i < MBR_PART_COUNT; i++, dp++) {
			/* Install in partition e, f, g, or h. */
			pp = &lp->d_partitions[RAW_PART + 1 + i];
			pp->p_offset = dp->mbrp_start;
			pp->p_size = dp->mbrp_size;
			if (dp->mbrp_type == MBR_PTYPE_LNXEXT2)
				pp->p_fstype = FS_EX2FS;

			if (dp->mbrp_type == MBR_PTYPE_LNXSWAP)
				pp->p_fstype = FS_SWAP;

			/* is this ours? */
			if (dp == ourdp) {
				/* need sector address for SCSI/IDE,
				 cylinder for ESDI/ST506/RLL */
				dospartoff = dp->mbrp_start;
				cyl = MBR_PCYL(dp->mbrp_scyl, dp->mbrp_ssect);

				/* update disklabel with details */
				lp->d_partitions[2].p_size =
				    dp->mbrp_size;
				lp->d_partitions[2].p_offset =
				    dp->mbrp_start;
			}
		}
		lp->d_npartitions = RAW_PART + 1 + i;
	}

nombrpart:
	/* next, dig out disk label */
	bp->b_blkno = dospartoff + LABELSECTOR;
	bp->b_cylinder = cyl;
	bp->b_bcount = lp->d_secsize;
	bp->b_cflags = BC_BUSY;
	bp->b_flags = B_READ;
	(*strat)(bp);

	/* if successful, locate disk label within block and validate */
	if (biowait(bp)) {
		msg = "disk label I/O error";
		goto done;
	}
	for (dlp = (struct disklabel *)bp->b_data;
	    dlp <= (struct disklabel *)
		((char *)bp->b_data + lp->d_secsize - sizeof(*dlp));
	    dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
		if (dlp->d_magic != DISKMAGIC || dlp->d_magic2 != DISKMAGIC) {
			if (msg == NULL)
				msg = "no disk label";
		} else if (dlp->d_npartitions > MAXPARTITIONS ||
			   dkcksum(dlp) != 0)
			msg = "disk label corrupted";
		else {
			*lp = *dlp;
			msg = NULL;
			break;
		}
	}

	if (msg)
		goto done;

	/* obtain bad sector table if requested and present */
	if (osdep && (lp->d_flags & D_BADSECT)) {
		struct dkbad *db;

		bdp = &osdep->bad;
		i = 0;
		do {
			/* read a bad sector table */
			bp->b_cflags = BC_BUSY;
			bp->b_flags = B_READ;
			bp->b_blkno = lp->d_secperunit - lp->d_nsectors + i;
			if (lp->d_secsize > DEV_BSIZE)
				bp->b_blkno *= lp->d_secsize / DEV_BSIZE;
			else
				bp->b_blkno /= DEV_BSIZE / lp->d_secsize;
			bp->b_bcount = lp->d_secsize;
			bp->b_cylinder = lp->d_ncylinders - 1;
			(*strat)(bp);

			/* if successful, validate, otherwise try another */
			if (biowait(bp)) {
				msg = "bad sector table I/O error";
			} else {
				db = (struct dkbad *)(bp->b_data);
#define	DKBAD_MAGIC 0x4321
				if (db->bt_mbz == 0
					&& db->bt_flag == DKBAD_MAGIC) {
					msg = NULL;
					*bdp = *db;
					break;
				} else
					msg = "bad sector table corrupted";
			}
		} while (bp->b_error && (i += 2) < 10 &&
			i < lp->d_nsectors);
	}

done:
	brelse(bp, BC_INVAL);
	return (msg);
}

/*
 * Write disk label back to device after modification.
 */
int
writedisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel *lp, struct cpu_disklabel *osdep)
{
	struct mbr_partition *dp;
	struct buf *bp;
	struct disklabel *dlp;
	int error, dospartoff, cyl;

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

	/* do dos partitions in the process of getting disklabel? */
	dospartoff = 0;
	cyl = LABELSECTOR / lp->d_secpercyl;
	if (!osdep)
		goto nombrpart;
	dp = osdep->mbrparts;

	/* read master boot record */
	bp->b_blkno = MBR_BBSECTOR;
	bp->b_bcount = lp->d_secsize;
	bp->b_cflags = BC_BUSY;
	bp->b_flags = B_READ;
	bp->b_cylinder = MBR_BBSECTOR / lp->d_secpercyl;
	(*strat)(bp);

	if ((error = biowait(bp)) == 0) {
		struct mbr_partition *ourdp = NULL;

		ourdp = mbr_findslice(dp, bp);
		if (ourdp ==  NO_MBR_SIGNATURE)
			goto nombrpart;

		if (ourdp) {
			/* need sector address for SCSI/IDE,
			 cylinder for ESDI/ST506/RLL */
			dospartoff = ourdp->mbrp_start;
			cyl = MBR_PCYL(ourdp->mbrp_scyl, ourdp->mbrp_ssect);
		}
	}

nombrpart:
	/* next, dig out disk label */
	bp->b_blkno = dospartoff + LABELSECTOR;
	bp->b_cylinder = cyl;
	bp->b_bcount = lp->d_secsize;
	bp->b_cflags = BC_BUSY;
	bp->b_flags = B_READ;
	(*strat)(bp);

	/* if successful, locate disk label within block and validate */
	if ((error = biowait(bp)) != 0)
		goto done;
	for (dlp = (struct disklabel *)bp->b_data;
	    dlp <= (struct disklabel *)
		((char *)bp->b_data + lp->d_secsize - sizeof(*dlp));
	    dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
		if (dlp->d_magic == DISKMAGIC && dlp->d_magic2 == DISKMAGIC &&
		    dkcksum(dlp) == 0) {
			*dlp = *lp;
			bp->b_cflags = BC_BUSY;
			bp->b_flags = B_WRITE;
			(*strat)(bp);
			error = biowait(bp);
			goto done;
		}
	}
	error = ESRCH;

done:
	brelse(bp, BC_INVAL);
	return (error);
}