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/* raid6_recover.c - module to recover from faulty RAID6 arrays. */
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2006,2007,2008,2009 Free Software Foundation, Inc.
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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#include <grub/disk.h>
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#include <grub/misc.h>
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#include <grub/raid.h>
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static grub_uint8_t raid6_table1[256][256];
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static grub_uint8_t raid6_table2[256][256];
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grub_raid_block_mul (grub_uint8_t mul, char *buf, int size)
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p = (grub_uint8_t *) buf;
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for (i = 0; i < size; i++, p++)
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*p = raid6_table1[mul][*p];
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grub_raid6_init_table (void)
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for (i = 0; i < 256; i++)
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raid6_table1[i][1] = raid6_table1[1][i] = i;
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for (i = 2; i < 256; i++)
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for (j = i; j < 256; j++)
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c = raid6_table1[n][j];
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c = (c << 1) ^ ((c & 0x80) ? 0x1d : 0);
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raid6_table1[j][i] = raid6_table1[i][j] = c;
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raid6_table2[0][0] = 1;
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for (i = 1; i < 256; i++)
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raid6_table2[i][i] = raid6_table1[raid6_table2[i - 1][i - 1]][2];
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for (i = 0; i < 254; i++)
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for (j = 0; j < 254; j++)
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c = n = raid6_table2[k][k] ^ 1;
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for (k = 0; k < 253; k++)
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c = raid6_table1[c][n];
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raid6_table2[i][j] = raid6_table1[raid6_table2[255 - j][255 - j]][c];
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grub_raid6_recover (struct grub_raid_array *array, int disknr, int p,
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char *buf, grub_disk_addr_t sector, int size)
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int bad1 = -1, bad2 = -1;
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char *pbuf = 0, *qbuf = 0;
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size <<= GRUB_DISK_SECTOR_BITS;
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pbuf = grub_zalloc (size);
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qbuf = grub_zalloc (size);
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if (q == (int) array->total_devs)
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if (pos == (int) array->total_devs)
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for (i = 0; i < (int) array->total_devs - 2; i++)
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if ((array->device[pos]) &&
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(! grub_disk_read (array->device[pos], sector, 0, size, buf)))
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grub_raid_block_xor (pbuf, buf, size);
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grub_raid_block_mul (raid6_table2[i][i], buf, size);
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grub_raid_block_xor (qbuf, buf, size);
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/* Too many bad devices */
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grub_errno = GRUB_ERR_NONE;
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if (pos == (int) array->total_devs)
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/* Invalid disknr or p */
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if ((array->device[p]) &&
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(! grub_disk_read (array->device[p], sector, 0, size, buf)))
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grub_raid_block_xor (buf, pbuf, size);
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if (! array->device[q])
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grub_error (GRUB_ERR_READ_ERROR, "not enough disk to restore");
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grub_errno = GRUB_ERR_NONE;
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if (grub_disk_read (array->device[q], sector, 0, size, buf))
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grub_raid_block_xor (buf, qbuf, size);
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grub_raid_block_mul (raid6_table2[255 - bad1][255 - bad1], buf,
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/* Two bad devices */
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if ((! array->device[p]) || (! array->device[q]))
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grub_error (GRUB_ERR_READ_ERROR, "not enough disk to restore");
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if (grub_disk_read (array->device[p], sector, 0, size, buf))
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grub_raid_block_xor (pbuf, buf, size);
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if (grub_disk_read (array->device[q], sector, 0, size, buf))
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grub_raid_block_xor (qbuf, buf, size);
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c = raid6_table2[bad2][bad1];
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grub_raid_block_mul (c, qbuf, size);
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c = raid6_table1[raid6_table2[bad2][bad2]][c];
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grub_raid_block_mul (c, pbuf, size);
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grub_raid_block_xor (pbuf, qbuf, size);
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grub_memcpy (buf, pbuf, size);
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GRUB_MOD_INIT(raid6rec)
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grub_raid6_init_table ();
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grub_raid6_recover_func = grub_raid6_recover;
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GRUB_MOD_FINI(raid6rec)
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grub_raid6_recover_func = 0;