arch/all-pc/boot/grub2-aros/grub-core/disk/raid6_recover.c

   1 /* raid6_recover.c - module to recover from faulty RAID6 arrays.  */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2006,2007,2008,2009  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/dl.h>
  21 #include <grub/disk.h>
  22 #include <grub/mm.h>
  23 #include <grub/err.h>
  24 #include <grub/misc.h>
  25 #include <grub/diskfilter.h>
  26 #include <grub/crypto.h>
  27
  28 GRUB_MOD_LICENSE ("GPLv3+");
  29
  30 /* x**y.  */
  31 static grub_uint8_t powx[255 * 2];
  32 /* Such an s that x**s = y */
  33 static unsigned powx_inv[256];
  34 static const grub_uint8_t poly = 0x1d;
  35
  36 static void
  37 grub_raid_block_mulx (unsigned mul, char *buf, grub_size_t size)
  38 {
  39   grub_size_t i;
  40   grub_uint8_t *p;
  41
  42   p = (grub_uint8_t *) buf;
  43   for (i = 0; i < size; i++, p++)
  44     if (*p)
  45       *p = powx[mul + powx_inv[*p]];
  46 }
  47
  48 static void
  49 grub_raid6_init_table (void)
  50 {
  51   unsigned i;
  52
  53   grub_uint8_t cur = 1;
  54   for (i = 0; i < 255; i++)
  55     {
  56       powx[i] = cur;
  57       powx[i + 255] = cur;
  58       powx_inv[cur] = i;
  59       if (cur & 0x80)
  60         cur = (cur << 1) ^ poly;
  61       else
  62         cur <<= 1;
  63     }
  64 }
  65
  66 static grub_err_t
  67 grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
  68                     char *buf, grub_disk_addr_t sector, grub_size_t size)
  69 {
  70   int i, q, pos;
  71   int bad1 = -1, bad2 = -1;
  72   char *pbuf = 0, *qbuf = 0;
  73
  74   size <<= GRUB_DISK_SECTOR_BITS;
  75   pbuf = grub_zalloc (size);
  76   if (!pbuf)
  77     goto quit;
  78
  79   qbuf = grub_zalloc (size);
  80   if (!qbuf)
  81     goto quit;
  82
  83   q = p + 1;
  84   if (q == (int) array->node_count)
  85     q = 0;
  86
  87   pos = q + 1;
  88   if (pos == (int) array->node_count)
  89     pos = 0;
  90
  91   for (i = 0; i < (int) array->node_count - 2; i++)
  92     {
  93       int c;
  94       if (array->layout & GRUB_RAID_LAYOUT_MUL_FROM_POS)
  95         c = pos;
  96       else
  97         c = i;
  98       if (pos == disknr)
  99         bad1 = c;
 100       else
 101         {
 102           if (! grub_diskfilter_read_node (&array->nodes[pos], sector,
 103                                            size >> GRUB_DISK_SECTOR_BITS, buf))
 104             {
 105               grub_crypto_xor (pbuf, pbuf, buf, size);
 106               grub_raid_block_mulx (c, buf, size);
 107               grub_crypto_xor (qbuf, qbuf, buf, size);
 108             }
 109           else
 110             {
 111               /* Too many bad devices */
 112               if (bad2 >= 0)
 113                 goto quit;
 114
 115               bad2 = c;
 116               grub_errno = GRUB_ERR_NONE;
 117             }
 118         }
 119
 120       pos++;
 121       if (pos == (int) array->node_count)
 122         pos = 0;
 123     }
 124
 125   /* Invalid disknr or p */
 126   if (bad1 < 0)
 127     goto quit;
 128
 129   if (bad2 < 0)
 130     {
 131       /* One bad device */
 132       if ((! grub_diskfilter_read_node (&array->nodes[p], sector,
 133                                         size >> GRUB_DISK_SECTOR_BITS, buf)))
 134         {
 135           grub_crypto_xor (buf, buf, pbuf, size);
 136           goto quit;
 137         }
 138
 139       grub_errno = GRUB_ERR_NONE;
 140       if (grub_diskfilter_read_node (&array->nodes[q], sector,
 141                                      size >> GRUB_DISK_SECTOR_BITS, buf))
 142         goto quit;
 143
 144       grub_crypto_xor (buf, buf, qbuf, size);
 145       grub_raid_block_mulx (255 - bad1, buf,
 146                            size);
 147     }
 148   else
 149     {
 150       /* Two bad devices */
 151       unsigned c;
 152
 153       if (grub_diskfilter_read_node (&array->nodes[p], sector,
 154                                      size >> GRUB_DISK_SECTOR_BITS, buf))
 155         goto quit;
 156
 157       grub_crypto_xor (pbuf, pbuf, buf, size);
 158
 159       if (grub_diskfilter_read_node (&array->nodes[q], sector,
 160                                      size >> GRUB_DISK_SECTOR_BITS, buf))
 161         goto quit;
 162
 163       grub_crypto_xor (qbuf, qbuf, buf, size);
 164
 165       c = ((255 ^ bad1)
 166            + (255 ^ powx_inv[(powx[bad2 + (bad1 ^ 255)] ^ 1)])) % 255;
 167       grub_raid_block_mulx (c, qbuf, size);
 168
 169       c = ((unsigned) bad2 + c) % 255;
 170       grub_raid_block_mulx (c, pbuf, size);
 171
 172       grub_crypto_xor (pbuf, pbuf, qbuf, size);
 173       grub_memcpy (buf, pbuf, size);
 174     }
 175
 176 quit:
 177   grub_free (pbuf);
 178   grub_free (qbuf);
 179
 180   return grub_errno;
 181 }
 182
 183 GRUB_MOD_INIT(raid6rec)
 184 {
 185   grub_raid6_init_table ();
 186   grub_raid6_recover_func = grub_raid6_recover;
 187 }
 188
 189 GRUB_MOD_FINI(raid6rec)
 190 {
 191   grub_raid6_recover_func = 0;
 192 }