1/*
2 * Copyright (C) 2015 Google, Inc.
3 *
4 * Author: Sami Tolvanen <samitolvanen@google.com>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the Free
8 * Software Foundation; either version 2 of the License, or (at your option)
9 * any later version.
10 */
11
12#ifndef DM_VERITY_FEC_H
13#define DM_VERITY_FEC_H
14
15#include "dm-verity.h"
16#include <linux/rslib.h>
17
18/* Reed-Solomon(M, N) parameters */
19#define DM_VERITY_FEC_RSM 255
20#define DM_VERITY_FEC_MAX_RSN 253
21#define DM_VERITY_FEC_MIN_RSN 231 /* ~10% space overhead */
22
23/* buffers for deinterleaving and decoding */
24#define DM_VERITY_FEC_BUF_PREALLOC 1 /* buffers to preallocate */
25#define DM_VERITY_FEC_BUF_RS_BITS 4 /* 1 << RS blocks per buffer */
26/* we need buffers for at most 1 << block size RS blocks */
27#define DM_VERITY_FEC_BUF_MAX \
28 (1 << (PAGE_SHIFT - DM_VERITY_FEC_BUF_RS_BITS))
29
30/* maximum recursion level for verity_fec_decode */
31#define DM_VERITY_FEC_MAX_RECURSION 4
32
33#define DM_VERITY_OPT_FEC_DEV "use_fec_from_device"
34#define DM_VERITY_OPT_FEC_BLOCKS "fec_blocks"
35#define DM_VERITY_OPT_FEC_START "fec_start"
36#define DM_VERITY_OPT_FEC_ROOTS "fec_roots"
37
38/* configuration */
39struct dm_verity_fec {
40 struct dm_dev *dev; /* parity data device */
41 struct dm_bufio_client *data_bufio; /* for data dev access */
42 struct dm_bufio_client *bufio; /* for parity data access */
43 sector_t start; /* parity data start in blocks */
44 sector_t blocks; /* number of blocks covered */
45 sector_t rounds; /* number of interleaving rounds */
46 sector_t hash_blocks; /* blocks covered after v->hash_start */
47 unsigned char roots; /* number of parity bytes, M-N of RS(M, N) */
48 unsigned char rsn; /* N of RS(M, N) */
49 mempool_t rs_pool; /* mempool for fio->rs */
50 mempool_t prealloc_pool; /* mempool for preallocated buffers */
51 mempool_t extra_pool; /* mempool for extra buffers */
52 mempool_t output_pool; /* mempool for output */
53 struct kmem_cache *cache; /* cache for buffers */
54};
55
56/* per-bio data */
57struct dm_verity_fec_io {
58 struct rs_control *rs; /* Reed-Solomon state */
59 int erasures[DM_VERITY_FEC_MAX_RSN]; /* erasures for decode_rs8 */
60 u8 *bufs[DM_VERITY_FEC_BUF_MAX]; /* bufs for deinterleaving */
61 unsigned nbufs; /* number of buffers allocated */
62 u8 *output; /* buffer for corrected output */
63 size_t output_pos;
64 unsigned level; /* recursion level */
65};
66
67#ifdef CONFIG_DM_VERITY_FEC
68
69/* each feature parameter requires a value */
70#define DM_VERITY_OPTS_FEC 8
71
72extern bool verity_fec_is_enabled(struct dm_verity *v);
73
74extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
75 enum verity_block_type type, sector_t block,
76 u8 *dest, struct bvec_iter *iter);
77
78extern unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
79 char *result, unsigned maxlen);
80
81extern void verity_fec_finish_io(struct dm_verity_io *io);
82extern void verity_fec_init_io(struct dm_verity_io *io);
83
84extern bool verity_is_fec_opt_arg(const char *arg_name);
85extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
86 struct dm_verity *v, unsigned *argc,
87 const char *arg_name);
88
89extern void verity_fec_dtr(struct dm_verity *v);
90
91extern int verity_fec_ctr_alloc(struct dm_verity *v);
92extern int verity_fec_ctr(struct dm_verity *v);
93
94#else /* !CONFIG_DM_VERITY_FEC */
95
96#define DM_VERITY_OPTS_FEC 0
97
98static inline bool verity_fec_is_enabled(struct dm_verity *v)
99{
100 return false;
101}
102
103static inline int verity_fec_decode(struct dm_verity *v,
104 struct dm_verity_io *io,
105 enum verity_block_type type,
106 sector_t block, u8 *dest,
107 struct bvec_iter *iter)
108{
109 return -EOPNOTSUPP;
110}
111
112static inline unsigned verity_fec_status_table(struct dm_verity *v,
113 unsigned sz, char *result,
114 unsigned maxlen)
115{
116 return sz;
117}
118
119static inline void verity_fec_finish_io(struct dm_verity_io *io)
120{
121}
122
123static inline void verity_fec_init_io(struct dm_verity_io *io)
124{
125}
126
127static inline bool verity_is_fec_opt_arg(const char *arg_name)
128{
129 return false;
130}
131
132static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
133 struct dm_verity *v,
134 unsigned *argc,
135 const char *arg_name)
136{
137 return -EINVAL;
138}
139
140static inline void verity_fec_dtr(struct dm_verity *v)
141{
142}
143
144static inline int verity_fec_ctr_alloc(struct dm_verity *v)
145{
146 return 0;
147}
148
149static inline int verity_fec_ctr(struct dm_verity *v)
150{
151 return 0;
152}
153
154#endif /* CONFIG_DM_VERITY_FEC */
155
156#endif /* DM_VERITY_FEC_H */
157