/* 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(M, N) parameters */
#define DM_VERITY_FEC_RSM               255
#define DM_VERITY_FEC_MAX_RSN           253
#define DM_VERITY_FEC_MIN_RSN           231     /* ~10% space overhead */

/* buffers for deinterleaving and decoding */
#define DM_VERITY_FEC_BUF_RS_BITS       4       /* 1 << RS blocks 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 io_size;         /* IO size for roots */
        sector_t start;         /* parity data start in blocks */
        sector_t blocks;        /* number of blocks covered */
        sector_t rounds;        /* number of interleaving rounds */
        sector_t hash_blocks;   /* blocks covered after v->hash_start */
        unsigned char roots;    /* number of parity bytes, M-N of RS(M, N) */
        unsigned char rsn;      /* N of RS(M, N) */
        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_RSN];    /* 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 blocks.  Each buffer has space for
         * the data bytes of (1 << DM_VERITY_FEC_BUF_RS_BITS) RS blocks.  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 */