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      1 /* $NetBSD: disksubr.c,v 1.44 2026/07/14 13:34:33 thorpej Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1994, 1995, 1996 Carnegie-Mellon University.
      5  * All rights reserved.
      6  *
      7  * Authors: Keith Bostic, Chris G. Demetriou
      8  *
      9  * Permission to use, copy, modify and distribute this software and
     10  * its documentation is hereby granted, provided that both the copyright
     11  * notice and this permission notice appear in all copies of the
     12  * software, derivative works or modified versions, and any portions
     13  * thereof, and that both notices appear in supporting documentation.
     14  *
     15  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     16  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     17  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     18  *
     19  * Carnegie Mellon requests users of this software to return to
     20  *
     21  *  Software Distribution Coordinator  or  Software.Distribution (at) CS.CMU.EDU
     22  *  School of Computer Science
     23  *  Carnegie Mellon University
     24  *  Pittsburgh PA 15213-3890
     25  *
     26  * any improvements or extensions that they make and grant Carnegie the
     27  * rights to redistribute these changes.
     28  */
     29 
     30 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
     31 
     32 __KERNEL_RCSID(0, "$NetBSD: disksubr.c,v 1.44 2026/07/14 13:34:33 thorpej Exp $");
     33 
     34 #include <sys/param.h>
     35 #include <sys/systm.h>
     36 #include <sys/buf.h>
     37 #include <sys/ioccom.h>
     38 #include <sys/device.h>
     39 #include <sys/disklabel.h>
     40 #include <sys/disk.h>
     41 
     42 #include <machine/cpu.h>
     43 #include <machine/autoconf.h>
     44 
     45 extern device_t bootdv;
     46 
     47 /*
     48  * Attempt to read a disk label from a device
     49  * using the indicated strategy routine.
     50  * The label must be partly set up before this:
     51  * secpercyl and anything required in the strategy routine
     52  * (e.g., sector size) must be filled in before calling us.
     53  * Returns null on success and an error string on failure.
     54  */
     55 const char *
     56 readdisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel *lp, struct cpu_disklabel *clp)
     57 {
     58 	struct buf *bp;
     59 	struct disklabel *dlp;
     60 	const char *msg = NULL;
     61 
     62 	/* minimal requirements for archetypal disk label */
     63 	if (lp->d_secsize == 0)
     64 		lp->d_secsize = DEV_BSIZE;
     65 	if (lp->d_secperunit == 0)
     66 		lp->d_secperunit = 0x1fffffff;
     67 	lp->d_npartitions = RAW_PART + 1;
     68 	if (lp->d_partitions[RAW_PART].p_size == 0)
     69 		lp->d_partitions[RAW_PART].p_size = lp->d_secperunit;
     70 	lp->d_partitions[RAW_PART].p_offset = 0;
     71 
     72 	/* obtain buffer to probe drive with */
     73 	bp = geteblk((int)lp->d_secsize);
     74 
     75 	/* next, dig out disk label */
     76 	bp->b_dev = dev;
     77 	bp->b_blkno = LABELSECTOR;
     78 	bp->b_cylinder = 0;
     79 	bp->b_bcount = lp->d_secsize;
     80 	bp->b_flags |= B_READ;
     81 	(*strat)(bp);
     82 
     83 	/* if successful, locate disk label within block and validate */
     84 	if (biowait(bp)) {
     85 		msg = "disk label read error";
     86 		goto done;
     87 	}
     88 
     89 	dlp = (struct disklabel *)((char *)bp->b_data + LABELOFFSET);
     90 	if (dlp->d_magic == DISKMAGIC) {
     91 		if (dkcksum(dlp))
     92 			msg = "NetBSD disk label corrupted";
     93 		else
     94 			*lp = *dlp;
     95 	} else
     96 		msg = "no disk label";
     97 
     98 done:
     99 	brelse(bp, 0);
    100 	return (msg);
    101 }
    102 
    103 /*
    104  * Write disk label back to device after modification.
    105  * This means write out the rigid disk blocks to represent the
    106  * label.  Hope the user was careful.
    107  */
    108 int
    109 writedisklabel(dev_t dev, void (*strat)(struct buf *), struct disklabel *lp, struct cpu_disklabel *clp)
    110 {
    111 	struct buf *bp;
    112 	struct disklabel *dlp;
    113 	int error = 0;
    114 
    115 	bp = geteblk((int)lp->d_secsize);
    116 	bp->b_dev = dev;
    117 	bp->b_blkno = LABELSECTOR;
    118 	bp->b_cylinder = 0;
    119 	bp->b_bcount = lp->d_secsize;
    120 	bp->b_flags |= B_READ;           /* get current label */
    121 	(*strat)(bp);
    122 	if ((error = biowait(bp)) != 0)
    123 		goto done;
    124 
    125 	dlp = (struct disklabel *)((char *)bp->b_data + LABELOFFSET);
    126 	*dlp = *lp;     /* struct assignment */
    127 
    128 	/*
    129 	 * The Alpha requires that the boot block be checksummed.
    130 	 * The first 63 8-bit quantites are summed into the 64th.
    131 	 */
    132 	{
    133 		int i;
    134 		u_long *dp, sum;
    135 
    136 		dp = (u_long *)bp->b_data;
    137 		sum = 0;
    138 		for (i = 0; i < 63; i++)
    139 			sum += dp[i];
    140 		dp[63] = sum;
    141 	}
    142 
    143 	bp->b_flags &= ~B_READ;
    144 	bp->b_flags |= B_WRITE;
    145 	bp->b_oflags &= ~BO_DONE;
    146 	(*strat)(bp);
    147 	error = biowait(bp);
    148 
    149 done:
    150 	brelse(bp, 0);
    151 	return (error);
    152 }
    153