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