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![Russell King](/assets/img/avatar_default.png)
When scanning the map for a fragment id, we need to keep track of the free space links, so we don't inadvertently believe that the freespace link is a valid fragment id. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
407 lines
10 KiB
C
407 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/fs/adfs/map.c
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*
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* Copyright (C) 1997-2002 Russell King
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*/
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#include <linux/slab.h>
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#include <linux/statfs.h>
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#include <asm/unaligned.h>
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#include "adfs.h"
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/*
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* The ADFS map is basically a set of sectors. Each sector is called a
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* zone which contains a bitstream made up of variable sized fragments.
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* Each bit refers to a set of bytes in the filesystem, defined by
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* log2bpmb. This may be larger or smaller than the sector size, but
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* the overall size it describes will always be a round number of
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* sectors. A fragment id is always idlen bits long.
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*
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* < idlen > < n > <1>
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* +---------+-------//---------+---+
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* | frag id | 0000....000000 | 1 |
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* +---------+-------//---------+---+
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*
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* The physical disk space used by a fragment is taken from the start of
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* the fragment id up to and including the '1' bit - ie, idlen + n + 1
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* bits.
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*
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* A fragment id can be repeated multiple times in the whole map for
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* large or fragmented files. The first map zone a fragment starts in
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* is given by fragment id / ids_per_zone - this allows objects to start
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* from any zone on the disk.
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*
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* Free space is described by a linked list of fragments. Each free
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* fragment describes free space in the same way as the other fragments,
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* however, the frag id specifies an offset (in map bits) from the end
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* of this fragment to the start of the next free fragment.
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*
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* Objects stored on the disk are allocated object ids (we use these as
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* our inode numbers.) Object ids contain a fragment id and an optional
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* offset. This allows a directory fragment to contain small files
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* associated with that directory.
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*/
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/*
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* For the future...
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*/
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static DEFINE_RWLOCK(adfs_map_lock);
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/*
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* This is fun. We need to load up to 19 bits from the map at an
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* arbitrary bit alignment. (We're limited to 19 bits by F+ version 2).
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*/
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#define GET_FRAG_ID(_map,_start,_idmask) \
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({ \
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unsigned char *_m = _map + (_start >> 3); \
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u32 _frag = get_unaligned_le32(_m); \
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_frag >>= (_start & 7); \
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_frag & _idmask; \
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})
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/*
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* return the map bit offset of the fragment frag_id in the zone dm.
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* Note that the loop is optimised for best asm code - look at the
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* output of:
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* gcc -D__KERNEL__ -O2 -I../../include -o - -S map.c
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*/
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static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
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const u32 frag_id, unsigned int *offset)
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{
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const unsigned int endbit = dm->dm_endbit;
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const u32 idmask = (1 << idlen) - 1;
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unsigned char *map = dm->dm_bh->b_data;
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unsigned int start = dm->dm_startbit;
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unsigned int freelink, fragend;
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u32 frag;
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frag = GET_FRAG_ID(map, 8, idmask & 0x7fff);
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freelink = frag ? 8 + frag : 0;
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do {
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frag = GET_FRAG_ID(map, start, idmask);
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fragend = find_next_bit_le(map, endbit, start + idlen);
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if (fragend >= endbit)
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goto error;
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if (start == freelink) {
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freelink += frag & 0x7fff;
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} else if (frag == frag_id) {
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unsigned int length = fragend + 1 - start;
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if (*offset < length)
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return start + *offset;
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*offset -= length;
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}
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start = fragend + 1;
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} while (start < endbit);
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return -1;
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error:
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printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n",
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frag, start, fragend);
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return -1;
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}
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/*
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* Scan the free space map, for this zone, calculating the total
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* number of map bits in each free space fragment.
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*
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* Note: idmask is limited to 15 bits [3.2]
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*/
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static unsigned int
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scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm)
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{
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const unsigned int endbit = dm->dm_endbit;
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const unsigned int idlen = asb->s_idlen;
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const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
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const u32 idmask = (1 << frag_idlen) - 1;
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unsigned char *map = dm->dm_bh->b_data;
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unsigned int start = 8, fragend;
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u32 frag;
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unsigned long total = 0;
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/*
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* get fragment id
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*/
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frag = GET_FRAG_ID(map, start, idmask);
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/*
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* If the freelink is null, then no free fragments
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* exist in this zone.
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*/
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if (frag == 0)
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return 0;
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do {
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start += frag;
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frag = GET_FRAG_ID(map, start, idmask);
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fragend = find_next_bit_le(map, endbit, start + idlen);
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if (fragend >= endbit)
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goto error;
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total += fragend + 1 - start;
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} while (frag >= idlen + 1);
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if (frag != 0)
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printk(KERN_ERR "adfs: undersized free fragment\n");
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return total;
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error:
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printk(KERN_ERR "adfs: oversized free fragment\n");
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return 0;
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}
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static int scan_map(struct adfs_sb_info *asb, unsigned int zone,
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const u32 frag_id, unsigned int mapoff)
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{
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const unsigned int idlen = asb->s_idlen;
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struct adfs_discmap *dm, *dm_end;
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int result;
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dm = asb->s_map + zone;
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zone = asb->s_map_size;
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dm_end = asb->s_map + zone;
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do {
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result = lookup_zone(dm, idlen, frag_id, &mapoff);
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if (result != -1)
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goto found;
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dm ++;
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if (dm == dm_end)
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dm = asb->s_map;
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} while (--zone > 0);
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return -1;
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found:
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result -= dm->dm_startbit;
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result += dm->dm_startblk;
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return result;
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}
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/*
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* calculate the amount of free blocks in the map.
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*
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* n=1
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* total_free = E(free_in_zone_n)
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* nzones
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*/
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void adfs_map_statfs(struct super_block *sb, struct kstatfs *buf)
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{
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struct adfs_sb_info *asb = ADFS_SB(sb);
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struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map);
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struct adfs_discmap *dm;
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unsigned int total = 0;
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unsigned int zone;
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dm = asb->s_map;
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zone = asb->s_map_size;
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do {
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total += scan_free_map(asb, dm++);
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} while (--zone > 0);
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buf->f_blocks = adfs_disc_size(dr) >> sb->s_blocksize_bits;
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buf->f_files = asb->s_ids_per_zone * asb->s_map_size;
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buf->f_bavail =
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buf->f_bfree = signed_asl(total, asb->s_map2blk);
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}
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int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset)
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{
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struct adfs_sb_info *asb = ADFS_SB(sb);
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unsigned int zone, mapoff;
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int result;
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/*
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* map & root fragment is special - it starts in the center of the
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* disk. The other fragments start at zone (frag / ids_per_zone)
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*/
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if (frag_id == ADFS_ROOT_FRAG)
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zone = asb->s_map_size >> 1;
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else
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zone = frag_id / asb->s_ids_per_zone;
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if (zone >= asb->s_map_size)
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goto bad_fragment;
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/* Convert sector offset to map offset */
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mapoff = signed_asl(offset, -asb->s_map2blk);
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read_lock(&adfs_map_lock);
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result = scan_map(asb, zone, frag_id, mapoff);
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read_unlock(&adfs_map_lock);
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if (result > 0) {
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unsigned int secoff;
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/* Calculate sector offset into map block */
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secoff = offset - signed_asl(mapoff, asb->s_map2blk);
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return secoff + signed_asl(result, asb->s_map2blk);
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}
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adfs_error(sb, "fragment 0x%04x at offset %d not found in map",
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frag_id, offset);
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return 0;
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bad_fragment:
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adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)",
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frag_id, zone, asb->s_map_size);
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return 0;
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}
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static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map)
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{
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unsigned int v0, v1, v2, v3;
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int i;
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v0 = v1 = v2 = v3 = 0;
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for (i = sb->s_blocksize - 4; i; i -= 4) {
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v0 += map[i] + (v3 >> 8);
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v3 &= 0xff;
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v1 += map[i + 1] + (v0 >> 8);
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v0 &= 0xff;
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v2 += map[i + 2] + (v1 >> 8);
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v1 &= 0xff;
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v3 += map[i + 3] + (v2 >> 8);
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v2 &= 0xff;
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}
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v0 += v3 >> 8;
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v1 += map[1] + (v0 >> 8);
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v2 += map[2] + (v1 >> 8);
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v3 += map[3] + (v2 >> 8);
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return v0 ^ v1 ^ v2 ^ v3;
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}
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static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm)
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{
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unsigned char crosscheck = 0, zonecheck = 1;
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int i;
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for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
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unsigned char *map;
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map = dm[i].dm_bh->b_data;
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if (adfs_calczonecheck(sb, map) != map[0]) {
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adfs_error(sb, "zone %d fails zonecheck", i);
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zonecheck = 0;
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}
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crosscheck ^= map[3];
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}
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if (crosscheck != 0xff)
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adfs_error(sb, "crosscheck != 0xff");
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return crosscheck == 0xff && zonecheck;
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}
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/*
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* Layout the map - the first zone contains a copy of the disc record,
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* and the last zone must be limited to the size of the filesystem.
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*/
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static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones,
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struct adfs_discrecord *dr)
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{
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unsigned int zone, zone_size;
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u64 size;
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zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
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dm[0].dm_bh = NULL;
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dm[0].dm_startblk = 0;
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dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS;
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dm[0].dm_endbit = 32 + zone_size;
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for (zone = 1; zone < nzones; zone++) {
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dm[zone].dm_bh = NULL;
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dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
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dm[zone].dm_startbit = 32;
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dm[zone].dm_endbit = 32 + zone_size;
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}
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size = adfs_disc_size(dr) >> dr->log2bpmb;
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size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS;
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dm[nzones - 1].dm_endbit = 32 + size;
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}
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static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb,
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unsigned int map_addr, unsigned int nzones)
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{
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unsigned int zone;
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for (zone = 0; zone < nzones; zone++) {
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dm[zone].dm_bh = sb_bread(sb, map_addr + zone);
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if (!dm[zone].dm_bh)
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return -EIO;
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}
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return 0;
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}
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static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones)
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{
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unsigned int zone;
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for (zone = 0; zone < nzones; zone++)
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brelse(dm[zone].dm_bh);
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}
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struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr)
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{
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struct adfs_sb_info *asb = ADFS_SB(sb);
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struct adfs_discmap *dm;
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unsigned int map_addr, zone_size, nzones;
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int ret;
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nzones = dr->nzones | dr->nzones_high << 8;
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zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
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asb->s_idlen = dr->idlen;
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asb->s_map_size = nzones;
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asb->s_map2blk = dr->log2bpmb - dr->log2secsize;
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asb->s_log2sharesize = dr->log2sharesize;
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asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);
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map_addr = (nzones >> 1) * zone_size -
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((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
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map_addr = signed_asl(map_addr, asb->s_map2blk);
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dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL);
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if (dm == NULL) {
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adfs_error(sb, "not enough memory");
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return ERR_PTR(-ENOMEM);
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}
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adfs_map_layout(dm, nzones, dr);
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ret = adfs_map_read(dm, sb, map_addr, nzones);
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if (ret) {
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adfs_error(sb, "unable to read map");
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goto error_free;
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}
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if (adfs_checkmap(sb, dm))
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return dm;
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adfs_error(sb, "map corrupted");
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error_free:
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adfs_map_relse(dm, nzones);
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kfree(dm);
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return ERR_PTR(-EIO);
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}
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void adfs_free_map(struct super_block *sb)
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{
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struct adfs_sb_info *asb = ADFS_SB(sb);
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adfs_map_relse(asb->s_map, asb->s_map_size);
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kfree(asb->s_map);
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}
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