diff options
Diffstat (limited to 'grub-core/disk/raid6_recover.c')
| -rw-r--r-- | grub-core/disk/raid6_recover.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/grub-core/disk/raid6_recover.c b/grub-core/disk/raid6_recover.c new file mode 100644 index 0000000..75fe464 --- /dev/null +++ b/grub-core/disk/raid6_recover.c @@ -0,0 +1,218 @@ +/* raid6_recover.c - module to recover from faulty RAID6 arrays. */ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2006,2007,2008,2009 Free Software Foundation, Inc. + * + * GRUB is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * GRUB is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <grub/dl.h> +#include <grub/disk.h> +#include <grub/mm.h> +#include <grub/err.h> +#include <grub/misc.h> +#include <grub/diskfilter.h> +#include <grub/crypto.h> + +GRUB_MOD_LICENSE ("GPLv3+"); + +/* x**y. */ +static grub_uint8_t powx[255 * 2]; +/* Such an s that x**s = y */ +static unsigned powx_inv[256]; +static const grub_uint8_t poly = 0x1d; + +static void +grub_raid_block_mulx (unsigned mul, char *buf, grub_size_t size) +{ + grub_size_t i; + grub_uint8_t *p; + + p = (grub_uint8_t *) buf; + for (i = 0; i < size; i++, p++) + if (*p) + *p = powx[mul + powx_inv[*p]]; +} + +static void +grub_raid6_init_table (void) +{ + unsigned i; + + grub_uint8_t cur = 1; + for (i = 0; i < 255; i++) + { + powx[i] = cur; + powx[i + 255] = cur; + powx_inv[cur] = i; + if (cur & 0x80) + cur = (cur << 1) ^ poly; + else + cur <<= 1; + } +} + +static unsigned +mod_255 (unsigned x) +{ + while (x > 0xff) + x = (x >> 8) + (x & 0xff); + if (x == 0xff) + return 0; + return x; +} + +static grub_err_t +raid6_recover_read_node (void *data, int disknr, + grub_uint64_t sector, + void *buf, grub_size_t size) +{ + struct grub_diskfilter_segment *array = data; + + return grub_diskfilter_read_node (&array->nodes[disknr], + (grub_disk_addr_t)sector, + size >> GRUB_DISK_SECTOR_BITS, buf); +} + +grub_err_t +grub_raid6_recover_gen (void *data, grub_uint64_t nstripes, int disknr, int p, + char *buf, grub_uint64_t sector, grub_size_t size, + int layout, raid_recover_read_t read_func) +{ + int i, q, pos; + int bad1 = -1, bad2 = -1; + char *pbuf = 0, *qbuf = 0; + + pbuf = grub_zalloc (size); + if (!pbuf) + goto quit; + + qbuf = grub_zalloc (size); + if (!qbuf) + goto quit; + + q = p + 1; + if (q == (int) nstripes) + q = 0; + + pos = q + 1; + if (pos == (int) nstripes) + pos = 0; + + for (i = 0; i < (int) nstripes - 2; i++) + { + int c; + if (layout & GRUB_RAID_LAYOUT_MUL_FROM_POS) + c = pos; + else + c = i; + if (pos == disknr) + bad1 = c; + else + { + if (!read_func (data, pos, sector, buf, size)) + { + grub_crypto_xor (pbuf, pbuf, buf, size); + grub_raid_block_mulx (c, buf, size); + grub_crypto_xor (qbuf, qbuf, buf, size); + } + else + { + /* Too many bad devices */ + if (bad2 >= 0) + goto quit; + + bad2 = c; + grub_errno = GRUB_ERR_NONE; + } + } + + pos++; + if (pos == (int) nstripes) + pos = 0; + } + + /* Invalid disknr or p */ + if (bad1 < 0) + goto quit; + + if (bad2 < 0) + { + /* One bad device */ + if (!read_func (data, p, sector, buf, size)) + { + grub_crypto_xor (buf, buf, pbuf, size); + goto quit; + } + + grub_errno = GRUB_ERR_NONE; + if (read_func (data, q, sector, buf, size)) + goto quit; + + grub_crypto_xor (buf, buf, qbuf, size); + grub_raid_block_mulx (255 - bad1, buf, + size); + } + else + { + /* Two bad devices */ + unsigned c; + + if (read_func (data, p, sector, buf, size)) + goto quit; + + grub_crypto_xor (pbuf, pbuf, buf, size); + + if (read_func (data, q, sector, buf, size)) + goto quit; + + grub_crypto_xor (qbuf, qbuf, buf, size); + + c = mod_255((255 ^ bad1) + + (255 ^ powx_inv[(powx[bad2 + (bad1 ^ 255)] ^ 1)])); + grub_raid_block_mulx (c, qbuf, size); + + c = mod_255((unsigned) bad2 + c); + grub_raid_block_mulx (c, pbuf, size); + + grub_crypto_xor (pbuf, pbuf, qbuf, size); + grub_memcpy (buf, pbuf, size); + } + +quit: + grub_free (pbuf); + grub_free (qbuf); + + return grub_errno; +} + +static grub_err_t +grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p, + char *buf, grub_disk_addr_t sector, grub_size_t size) +{ + return grub_raid6_recover_gen (array, array->node_count, disknr, p, buf, + sector, size << GRUB_DISK_SECTOR_BITS, + array->layout, raid6_recover_read_node); +} + +GRUB_MOD_INIT(raid6rec) +{ + grub_raid6_init_table (); + grub_raid6_recover_func = grub_raid6_recover; +} + +GRUB_MOD_FINI(raid6rec) +{ + grub_raid6_recover_func = 0; +} |