cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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map.c (10362B)


      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 *  linux/fs/adfs/map.c
      4 *
      5 *  Copyright (C) 1997-2002 Russell King
      6 */
      7#include <linux/slab.h>
      8#include <linux/statfs.h>
      9#include <asm/unaligned.h>
     10#include "adfs.h"
     11
     12/*
     13 * The ADFS map is basically a set of sectors.  Each sector is called a
     14 * zone which contains a bitstream made up of variable sized fragments.
     15 * Each bit refers to a set of bytes in the filesystem, defined by
     16 * log2bpmb.  This may be larger or smaller than the sector size, but
     17 * the overall size it describes will always be a round number of
     18 * sectors.  A fragment id is always idlen bits long.
     19 *
     20 *  < idlen > <       n        > <1>
     21 * +---------+-------//---------+---+
     22 * | frag id |  0000....000000  | 1 |
     23 * +---------+-------//---------+---+
     24 *
     25 * The physical disk space used by a fragment is taken from the start of
     26 * the fragment id up to and including the '1' bit - ie, idlen + n + 1
     27 * bits.
     28 *
     29 * A fragment id can be repeated multiple times in the whole map for
     30 * large or fragmented files.  The first map zone a fragment starts in
     31 * is given by fragment id / ids_per_zone - this allows objects to start
     32 * from any zone on the disk.
     33 *
     34 * Free space is described by a linked list of fragments.  Each free
     35 * fragment describes free space in the same way as the other fragments,
     36 * however, the frag id specifies an offset (in map bits) from the end
     37 * of this fragment to the start of the next free fragment.
     38 *
     39 * Objects stored on the disk are allocated object ids (we use these as
     40 * our inode numbers.)  Object ids contain a fragment id and an optional
     41 * offset.  This allows a directory fragment to contain small files
     42 * associated with that directory.
     43 */
     44
     45/*
     46 * For the future...
     47 */
     48static DEFINE_RWLOCK(adfs_map_lock);
     49
     50/*
     51 * This is fun.  We need to load up to 19 bits from the map at an
     52 * arbitrary bit alignment.  (We're limited to 19 bits by F+ version 2).
     53 */
     54#define GET_FRAG_ID(_map,_start,_idmask)				\
     55	({								\
     56		unsigned char *_m = _map + (_start >> 3);		\
     57		u32 _frag = get_unaligned_le32(_m);			\
     58		_frag >>= (_start & 7);					\
     59		_frag & _idmask;					\
     60	})
     61
     62/*
     63 * return the map bit offset of the fragment frag_id in the zone dm.
     64 * Note that the loop is optimised for best asm code - look at the
     65 * output of:
     66 *  gcc -D__KERNEL__ -O2 -I../../include -o - -S map.c
     67 */
     68static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
     69		       const u32 frag_id, unsigned int *offset)
     70{
     71	const unsigned int endbit = dm->dm_endbit;
     72	const u32 idmask = (1 << idlen) - 1;
     73	unsigned char *map = dm->dm_bh->b_data;
     74	unsigned int start = dm->dm_startbit;
     75	unsigned int freelink, fragend;
     76	u32 frag;
     77
     78	frag = GET_FRAG_ID(map, 8, idmask & 0x7fff);
     79	freelink = frag ? 8 + frag : 0;
     80
     81	do {
     82		frag = GET_FRAG_ID(map, start, idmask);
     83
     84		fragend = find_next_bit_le(map, endbit, start + idlen);
     85		if (fragend >= endbit)
     86			goto error;
     87
     88		if (start == freelink) {
     89			freelink += frag & 0x7fff;
     90		} else if (frag == frag_id) {
     91			unsigned int length = fragend + 1 - start;
     92
     93			if (*offset < length)
     94				return start + *offset;
     95			*offset -= length;
     96		}
     97
     98		start = fragend + 1;
     99	} while (start < endbit);
    100	return -1;
    101
    102error:
    103	printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n",
    104		frag, start, fragend);
    105	return -1;
    106}
    107
    108/*
    109 * Scan the free space map, for this zone, calculating the total
    110 * number of map bits in each free space fragment.
    111 *
    112 * Note: idmask is limited to 15 bits [3.2]
    113 */
    114static unsigned int
    115scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm)
    116{
    117	const unsigned int endbit = dm->dm_endbit;
    118	const unsigned int idlen  = asb->s_idlen;
    119	const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
    120	const u32 idmask = (1 << frag_idlen) - 1;
    121	unsigned char *map = dm->dm_bh->b_data;
    122	unsigned int start = 8, fragend;
    123	u32 frag;
    124	unsigned long total = 0;
    125
    126	/*
    127	 * get fragment id
    128	 */
    129	frag = GET_FRAG_ID(map, start, idmask);
    130
    131	/*
    132	 * If the freelink is null, then no free fragments
    133	 * exist in this zone.
    134	 */
    135	if (frag == 0)
    136		return 0;
    137
    138	do {
    139		start += frag;
    140
    141		frag = GET_FRAG_ID(map, start, idmask);
    142
    143		fragend = find_next_bit_le(map, endbit, start + idlen);
    144		if (fragend >= endbit)
    145			goto error;
    146
    147		total += fragend + 1 - start;
    148	} while (frag >= idlen + 1);
    149
    150	if (frag != 0)
    151		printk(KERN_ERR "adfs: undersized free fragment\n");
    152
    153	return total;
    154error:
    155	printk(KERN_ERR "adfs: oversized free fragment\n");
    156	return 0;
    157}
    158
    159static int scan_map(struct adfs_sb_info *asb, unsigned int zone,
    160		    const u32 frag_id, unsigned int mapoff)
    161{
    162	const unsigned int idlen = asb->s_idlen;
    163	struct adfs_discmap *dm, *dm_end;
    164	int result;
    165
    166	dm	= asb->s_map + zone;
    167	zone	= asb->s_map_size;
    168	dm_end	= asb->s_map + zone;
    169
    170	do {
    171		result = lookup_zone(dm, idlen, frag_id, &mapoff);
    172
    173		if (result != -1)
    174			goto found;
    175
    176		dm ++;
    177		if (dm == dm_end)
    178			dm = asb->s_map;
    179	} while (--zone > 0);
    180
    181	return -1;
    182found:
    183	result -= dm->dm_startbit;
    184	result += dm->dm_startblk;
    185
    186	return result;
    187}
    188
    189/*
    190 * calculate the amount of free blocks in the map.
    191 *
    192 *              n=1
    193 *  total_free = E(free_in_zone_n)
    194 *              nzones
    195 */
    196void adfs_map_statfs(struct super_block *sb, struct kstatfs *buf)
    197{
    198	struct adfs_sb_info *asb = ADFS_SB(sb);
    199	struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map);
    200	struct adfs_discmap *dm;
    201	unsigned int total = 0;
    202	unsigned int zone;
    203
    204	dm   = asb->s_map;
    205	zone = asb->s_map_size;
    206
    207	do {
    208		total += scan_free_map(asb, dm++);
    209	} while (--zone > 0);
    210
    211	buf->f_blocks  = adfs_disc_size(dr) >> sb->s_blocksize_bits;
    212	buf->f_files   = asb->s_ids_per_zone * asb->s_map_size;
    213	buf->f_bavail  =
    214	buf->f_bfree   = signed_asl(total, asb->s_map2blk);
    215}
    216
    217int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset)
    218{
    219	struct adfs_sb_info *asb = ADFS_SB(sb);
    220	unsigned int zone, mapoff;
    221	int result;
    222
    223	/*
    224	 * map & root fragment is special - it starts in the center of the
    225	 * disk.  The other fragments start at zone (frag / ids_per_zone)
    226	 */
    227	if (frag_id == ADFS_ROOT_FRAG)
    228		zone = asb->s_map_size >> 1;
    229	else
    230		zone = frag_id / asb->s_ids_per_zone;
    231
    232	if (zone >= asb->s_map_size)
    233		goto bad_fragment;
    234
    235	/* Convert sector offset to map offset */
    236	mapoff = signed_asl(offset, -asb->s_map2blk);
    237
    238	read_lock(&adfs_map_lock);
    239	result = scan_map(asb, zone, frag_id, mapoff);
    240	read_unlock(&adfs_map_lock);
    241
    242	if (result > 0) {
    243		unsigned int secoff;
    244
    245		/* Calculate sector offset into map block */
    246		secoff = offset - signed_asl(mapoff, asb->s_map2blk);
    247		return secoff + signed_asl(result, asb->s_map2blk);
    248	}
    249
    250	adfs_error(sb, "fragment 0x%04x at offset %d not found in map",
    251		   frag_id, offset);
    252	return 0;
    253
    254bad_fragment:
    255	adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)",
    256		   frag_id, zone, asb->s_map_size);
    257	return 0;
    258}
    259
    260static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map)
    261{
    262	unsigned int v0, v1, v2, v3;
    263	int i;
    264
    265	v0 = v1 = v2 = v3 = 0;
    266	for (i = sb->s_blocksize - 4; i; i -= 4) {
    267		v0 += map[i]     + (v3 >> 8);
    268		v3 &= 0xff;
    269		v1 += map[i + 1] + (v0 >> 8);
    270		v0 &= 0xff;
    271		v2 += map[i + 2] + (v1 >> 8);
    272		v1 &= 0xff;
    273		v3 += map[i + 3] + (v2 >> 8);
    274		v2 &= 0xff;
    275	}
    276	v0 +=           v3 >> 8;
    277	v1 += map[1] + (v0 >> 8);
    278	v2 += map[2] + (v1 >> 8);
    279	v3 += map[3] + (v2 >> 8);
    280
    281	return v0 ^ v1 ^ v2 ^ v3;
    282}
    283
    284static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm)
    285{
    286	unsigned char crosscheck = 0, zonecheck = 1;
    287	int i;
    288
    289	for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
    290		unsigned char *map;
    291
    292		map = dm[i].dm_bh->b_data;
    293
    294		if (adfs_calczonecheck(sb, map) != map[0]) {
    295			adfs_error(sb, "zone %d fails zonecheck", i);
    296			zonecheck = 0;
    297		}
    298		crosscheck ^= map[3];
    299	}
    300	if (crosscheck != 0xff)
    301		adfs_error(sb, "crosscheck != 0xff");
    302	return crosscheck == 0xff && zonecheck;
    303}
    304
    305/*
    306 * Layout the map - the first zone contains a copy of the disc record,
    307 * and the last zone must be limited to the size of the filesystem.
    308 */
    309static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones,
    310			    struct adfs_discrecord *dr)
    311{
    312	unsigned int zone, zone_size;
    313	u64 size;
    314
    315	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
    316
    317	dm[0].dm_bh       = NULL;
    318	dm[0].dm_startblk = 0;
    319	dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS;
    320	dm[0].dm_endbit   = 32 + zone_size;
    321
    322	for (zone = 1; zone < nzones; zone++) {
    323		dm[zone].dm_bh       = NULL;
    324		dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
    325		dm[zone].dm_startbit = 32;
    326		dm[zone].dm_endbit   = 32 + zone_size;
    327	}
    328
    329	size = adfs_disc_size(dr) >> dr->log2bpmb;
    330	size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS;
    331	dm[nzones - 1].dm_endbit = 32 + size;
    332}
    333
    334static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb,
    335			 unsigned int map_addr, unsigned int nzones)
    336{
    337	unsigned int zone;
    338
    339	for (zone = 0; zone < nzones; zone++) {
    340		dm[zone].dm_bh = sb_bread(sb, map_addr + zone);
    341		if (!dm[zone].dm_bh)
    342			return -EIO;
    343	}
    344
    345	return 0;
    346}
    347
    348static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones)
    349{
    350	unsigned int zone;
    351
    352	for (zone = 0; zone < nzones; zone++)
    353		brelse(dm[zone].dm_bh);
    354}
    355
    356struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr)
    357{
    358	struct adfs_sb_info *asb = ADFS_SB(sb);
    359	struct adfs_discmap *dm;
    360	unsigned int map_addr, zone_size, nzones;
    361	int ret;
    362
    363	nzones    = dr->nzones | dr->nzones_high << 8;
    364	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
    365
    366	asb->s_idlen = dr->idlen;
    367	asb->s_map_size = nzones;
    368	asb->s_map2blk = dr->log2bpmb - dr->log2secsize;
    369	asb->s_log2sharesize = dr->log2sharesize;
    370	asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);
    371
    372	map_addr = (nzones >> 1) * zone_size -
    373		     ((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
    374	map_addr = signed_asl(map_addr, asb->s_map2blk);
    375
    376	dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL);
    377	if (dm == NULL) {
    378		adfs_error(sb, "not enough memory");
    379		return ERR_PTR(-ENOMEM);
    380	}
    381
    382	adfs_map_layout(dm, nzones, dr);
    383
    384	ret = adfs_map_read(dm, sb, map_addr, nzones);
    385	if (ret) {
    386		adfs_error(sb, "unable to read map");
    387		goto error_free;
    388	}
    389
    390	if (adfs_checkmap(sb, dm))
    391		return dm;
    392
    393	adfs_error(sb, "map corrupted");
    394
    395error_free:
    396	adfs_map_relse(dm, nzones);
    397	kfree(dm);
    398	return ERR_PTR(-EIO);
    399}
    400
    401void adfs_free_map(struct super_block *sb)
    402{
    403	struct adfs_sb_info *asb = ADFS_SB(sb);
    404
    405	adfs_map_relse(asb->s_map, asb->s_map_size);
    406	kfree(asb->s_map);
    407}