153 lines
4.1 KiB
C
153 lines
4.1 KiB
C
/* pc.c - Read PC style partition tables. */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2002,2004,2005,2006,2007,2008,2009 Free Software Foundation, Inc.
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*
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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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*
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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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*
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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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*/
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#include <grub/partition.h>
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#include <grub/msdos_partition.h>
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#include <grub/disk.h>
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#include <grub/mm.h>
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#include <grub/misc.h>
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#include <grub/dl.h>
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static struct grub_partition_map grub_msdos_partition_map;
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static grub_err_t
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pc_partition_map_iterate (grub_disk_t disk,
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int (*hook) (grub_disk_t disk,
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const grub_partition_t partition))
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{
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struct grub_partition p;
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struct grub_msdos_partition_mbr mbr;
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int labeln = 0;
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grub_disk_addr_t lastaddr;
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grub_disk_addr_t ext_offset;
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p.offset = 0;
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ext_offset = 0;
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p.data = 0;
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p.number = -1;
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p.partmap = &grub_msdos_partition_map;
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/* Any value different than `p.offset' will satisfy the check during
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first loop. */
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lastaddr = !p.offset;
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while (1)
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{
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int i;
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struct grub_msdos_partition_entry *e;
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/* Read the MBR. */
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if (grub_disk_read (disk, p.offset, 0, sizeof (mbr), &mbr))
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goto finish;
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/* This is our loop-detection algorithm. It works the following way:
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It saves last position which was a power of two. Then it compares the
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saved value with a current one. This way it's guaranteed that the loop
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will be broken by at most third walk.
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*/
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if (labeln && lastaddr == p.offset)
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return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");
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labeln++;
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if ((labeln & (labeln - 1)) == 0)
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lastaddr = p.offset;
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/* Check if it is valid. */
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if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
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return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");
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for (i = 0; i < 4; i++)
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if (mbr.entries[i].flag & 0x7f)
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return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");
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/* Analyze DOS partitions. */
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for (p.index = 0; p.index < 4; p.index++)
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{
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e = mbr.entries + p.index;
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p.start = p.offset + grub_le_to_cpu32 (e->start);
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p.len = grub_le_to_cpu32 (e->length);
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grub_dprintf ("partition",
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"partition %d: flag 0x%x, type 0x%x, start 0x%llx, len 0x%llx\n",
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p.index, e->flag, e->type,
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(unsigned long long) p.start,
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(unsigned long long) p.len);
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/* If this is a GPT partition, this MBR is just a dummy. */
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if (e->type == GRUB_PC_PARTITION_TYPE_GPT_DISK && p.index == 0)
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return grub_error (GRUB_ERR_BAD_PART_TABLE, "dummy mbr");
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/* If this partition is a normal one, call the hook. */
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if (! grub_msdos_partition_is_empty (e->type)
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&& ! grub_msdos_partition_is_extended (e->type))
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{
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p.number++;
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if (hook (disk, &p))
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return grub_errno;
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}
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else if (p.number < 4)
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/* If this partition is a logical one, shouldn't increase the
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partition number. */
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p.number++;
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}
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/* Find an extended partition. */
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for (i = 0; i < 4; i++)
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{
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e = mbr.entries + i;
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if (grub_msdos_partition_is_extended (e->type))
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{
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p.offset = ext_offset + grub_le_to_cpu32 (e->start);
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if (! ext_offset)
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ext_offset = p.offset;
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break;
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}
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}
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/* If no extended partition, the end. */
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if (i == 4)
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break;
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}
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finish:
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return grub_errno;
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}
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/* Partition map type. */
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static struct grub_partition_map grub_msdos_partition_map =
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{
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.name = "msdos",
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.iterate = pc_partition_map_iterate,
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};
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GRUB_MOD_INIT(pc_partition_map)
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{
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grub_partition_map_register (&grub_msdos_partition_map);
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}
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GRUB_MOD_FINI(pc_partition_map)
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{
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grub_partition_map_unregister (&grub_msdos_partition_map);
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}
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