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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright (C) 2015 Google, Inc.
*
* Author: Sami Tolvanen <samitolvanen@google.com>
*/
#ifndef DM_VERITY_FEC_H
#define DM_VERITY_FEC_H
#include "dm-verity.h"
#include <linux/rslib.h>
/* Reed-Solomon(n, k) parameters */
#define DM_VERITY_FEC_RS_N 255
#define DM_VERITY_FEC_MIN_ROOTS 2 /* RS(255, 253): ~0.8% space overhead */
#define DM_VERITY_FEC_MAX_ROOTS 24 /* RS(255, 231): ~10% space overhead */
/* buffers for deinterleaving and decoding */
#define DM_VERITY_FEC_BUF_RS_BITS 4 /* log2(RS messages per buffer) */
#define DM_VERITY_OPT_FEC_DEV "use_fec_from_device"
#define DM_VERITY_OPT_FEC_BLOCKS "fec_blocks"
#define DM_VERITY_OPT_FEC_START "fec_start"
#define DM_VERITY_OPT_FEC_ROOTS "fec_roots"
/* configuration */
struct dm_verity_fec {
struct dm_dev *dev; /* parity data device */
struct dm_bufio_client *data_bufio; /* for data dev access */
struct dm_bufio_client *bufio; /* for parity data access */
size_t block_size; /* size of data, hash, and parity blocks in bytes */
sector_t start; /* parity data start in blocks */
sector_t blocks; /* number of blocks covered */
sector_t region_blocks; /* blocks per region: ceil(blocks / rs_k) */
sector_t hash_blocks; /* blocks covered after v->hash_start */
unsigned char roots; /* parity bytes per RS codeword, n-k of RS(n, k) */
unsigned char rs_k; /* message bytes per RS codeword, k of RS(n, k) */
mempool_t fio_pool; /* mempool for dm_verity_fec_io */
mempool_t rs_pool; /* mempool for fio->rs */
mempool_t prealloc_pool; /* mempool for preallocated buffers */
mempool_t output_pool; /* mempool for output */
struct kmem_cache *cache; /* cache for buffers */
atomic64_t corrected; /* corrected errors */
};
/* per-bio data */
struct dm_verity_fec_io {
struct rs_control *rs; /* Reed-Solomon state */
int erasures[DM_VERITY_FEC_MAX_ROOTS]; /* erasures for decode_rs8 */
u8 *output; /* buffer for corrected output */
unsigned int level; /* recursion level */
unsigned int nbufs; /* number of buffers allocated */
/*
* Buffers for deinterleaving RS codewords. Each buffer has space for
* the message bytes of (1 << DM_VERITY_FEC_BUF_RS_BITS) RS codewords.
* The array length is fec_max_nbufs(v), and we try to allocate that
* many buffers. However, in low-memory situations we may be unable to
* allocate all buffers. 'nbufs' holds the number actually allocated.
*/
u8 *bufs[];
};
#ifdef CONFIG_DM_VERITY_FEC
/* each feature parameter requires a value */
#define DM_VERITY_OPTS_FEC 8
/* Returns true if forward error correction is enabled. */
static inline bool verity_fec_is_enabled(struct dm_verity *v)
{
return v->fec && v->fec->dev;
}
extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
enum verity_block_type type, const u8 *want_digest,
sector_t block, u8 *dest);
extern unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz,
char *result, unsigned int maxlen);
extern void __verity_fec_finish_io(struct dm_verity_io *io);
static inline void verity_fec_finish_io(struct dm_verity_io *io)
{
if (unlikely(io->fec_io))
__verity_fec_finish_io(io);
}
static inline void verity_fec_init_io(struct dm_verity_io *io)
{
io->fec_io = NULL;
}
extern bool verity_is_fec_opt_arg(const char *arg_name);
extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
struct dm_verity *v, unsigned int *argc,
const char *arg_name);
extern void verity_fec_dtr(struct dm_verity *v);
extern int verity_fec_ctr_alloc(struct dm_verity *v);
extern int verity_fec_ctr(struct dm_verity *v);
#else /* !CONFIG_DM_VERITY_FEC */
#define DM_VERITY_OPTS_FEC 0
static inline bool verity_fec_is_enabled(struct dm_verity *v)
{
return false;
}
static inline int verity_fec_decode(struct dm_verity *v,
struct dm_verity_io *io,
enum verity_block_type type,
const u8 *want_digest,
sector_t block, u8 *dest)
{
return -EOPNOTSUPP;
}
static inline unsigned int verity_fec_status_table(struct dm_verity *v,
unsigned int sz, char *result,
unsigned int maxlen)
{
return sz;
}
static inline void verity_fec_finish_io(struct dm_verity_io *io)
{
}
static inline void verity_fec_init_io(struct dm_verity_io *io)
{
}
static inline bool verity_is_fec_opt_arg(const char *arg_name)
{
return false;
}
static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
struct dm_verity *v,
unsigned int *argc,
const char *arg_name)
{
return -EINVAL;
}
static inline void verity_fec_dtr(struct dm_verity *v)
{
}
static inline int verity_fec_ctr_alloc(struct dm_verity *v)
{
return 0;
}
static inline int verity_fec_ctr(struct dm_verity *v)
{
return 0;
}
#endif /* CONFIG_DM_VERITY_FEC */
#endif /* DM_VERITY_FEC_H */
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