sys/arch/acorn32/stand/lib/riscospart.c

   1 /*      $NetBSD: riscospart.c,v 1.1 2006/04/01 19:08:08 bjh21 Exp $     */
   2
   3 /*-
   4  * Copyright (c) 2006 Ben Harris
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. The name of the author may not be used to endorse or promote products
  16  *    derived from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 /*
  31  * Copyright (c) 1995 Mark Brinicombe
  32  * All rights reserved.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  * 1. Redistributions of source code must retain the above copyright
  38  *    notice, this list of conditions and the following disclaimer.
  39  * 2. Redistributions in binary form must reproduce the above copyright
  40  *    notice, this list of conditions and the following disclaimer in the
  41  *    documentation and/or other materials provided with the distribution.
  42  * 3. All advertising materials mentioning features or use of this software
  43  *    must display the following acknowledgement:
  44  *      This product includes software developed by the University of
  45  *      California, Berkeley and its contributors.
  46  * 4. Neither the name of the University nor the names of its contributors
  47  *    may be used to endorse or promote products derived from this software
  48  *    without specific prior written permission.
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  60  * SUCH DAMAGE.
  61  */
  62
  63 #include <sys/types.h>
  64 #include <sys/param.h>
  65 #include <sys/disklabel.h>
  66 #include <sys/disklabel_acorn.h>
  67
  68 #include <lib/libsa/stand.h>
  69
  70 #include "riscospart.h"
  71
  72 /*
  73  * This function should be shared between here,
  74  * sys/arch/arm/arm/disksubr_acorn.c, and
  75  * sys/fs/filecorefs/filecore_utils.c, rather than being copied.
  76  */
  77 /*
  78  * static int filecore_checksum(u_char *bootblock)
  79  *
  80  * Calculates the filecore boot block checksum. This is used to validate
  81  * a filecore boot block on the disk.  If a boot block is validated then
  82  * it is used to locate the partition table. If the boot block is not
  83  * validated, it is assumed that the whole disk is NetBSD.
  84  *
  85  * The basic algorithm is:
  86  *
  87  *      for (each byte in block, excluding checksum) {
  88  *              sum += byte;
  89  *              if (sum > 255)
  90  *                      sum -= 255;
  91  *      }
  92  *
  93  * That's equivalent to summing all of the bytes in the block
  94  * (excluding the checksum byte, of course), then calculating the
  95  * checksum as "cksum = sum - ((sum - 1) / 255) * 255)".  That
  96  * expression may or may not yield a faster checksum function,
  97  * but it's easier to reason about.
  98  *
  99  * Note that if you have a block filled with bytes of a single
 100  * value "X" (regardless of that value!) and calculate the cksum
 101  * of the block (excluding the checksum byte), you will _always_
 102  * end up with a checksum of X.  (Do the math; that can be derived
 103  * from the checksum calculation function!)  That means that
 104  * blocks which contain bytes which all have the same value will
 105  * always checksum properly.  That's a _very_ unlikely occurence
 106  * (probably impossible, actually) for a valid filecore boot block,
 107  * so we treat such blocks as invalid.
 108  */
 109 static int
 110 filecore_checksum(u_char *bootblock)
 111 {
 112         u_char byte0, accum_diff;
 113         u_int sum;
 114         int i;
 115
 116         sum = 0;
 117         accum_diff = 0;
 118         byte0 = bootblock[0];
 119
 120         /*
 121          * Sum the contents of the block, keeping track of whether
 122          * or not all bytes are the same.  If 'accum_diff' ends up
 123          * being zero, all of the bytes are, in fact, the same.
 124          */
 125         for (i = 0; i < 511; ++i) {
 126                 sum += bootblock[i];
 127                 accum_diff |= bootblock[i] ^ byte0;
 128         }
 129
 130         /*
 131          * Check to see if the checksum byte is the same as the
 132          * rest of the bytes, too.  (Note that if all of the bytes
 133          * are the same except the checksum, a checksum compare
 134          * won't succeed, but that's not our problem.)
 135          */
 136         accum_diff |= bootblock[i] ^ byte0;
 137
 138         /* All bytes in block are the same; call it invalid. */
 139         if (accum_diff == 0)
 140                 return (-1);
 141
 142         return (sum - ((sum - 1) / 255) * 255);
 143 }
 144
 145
 146 int
 147 getdisklabel_acorn(struct open_file *f, struct disklabel *lp)
 148 {
 149         size_t rsize;
 150         int err;
 151         char *buf;
 152         struct filecore_bootblock *bb;
 153         daddr_t labelsect;
 154         char *msg;
 155
 156         buf = alloc(DEV_BSIZE);
 157         err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ,
 158             FILECORE_BOOT_SECTOR, DEV_BSIZE, buf, &rsize);
 159         if (err != 0) goto out;
 160         bb = (struct filecore_bootblock *) buf;
 161         if (bb->checksum == filecore_checksum((u_char *)bb)) {
 162                 if (bb->partition_type == PARTITION_FORMAT_RISCBSD)
 163                         labelsect = (daddr_t)bb->partition_cyl_low *
 164                             bb->heads * bb->secspertrack + LABELSECTOR;
 165                 else {
 166                         err = EUNLAB;
 167                         goto out;
 168                 }
 169         } else
 170                 labelsect = LABELSECTOR;
 171         err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ,
 172             labelsect, DEV_BSIZE, buf, &rsize);
 173         if (err != 0) goto out;
 174         msg = getdisklabel(buf, lp);
 175         if (msg) {
 176                 printf("%s\n", msg);
 177                 err = ERDLAB;
 178         }
 179 out:
 180         dealloc(buf, DEV_BSIZE);
 181         return err;
 182 }