tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Copyright (C) 2015 Google, Inc.
4 *
5 * Author: Sami Tolvanen <samitolvanen@google.com>
6 */
7
8#ifndef DM_VERITY_FEC_H
9#define DM_VERITY_FEC_H
10
11#include "dm-verity.h"
12#include <linux/rslib.h>
13
14/* Reed-Solomon(n, k) parameters */
15#define DM_VERITY_FEC_RS_N 255
16#define DM_VERITY_FEC_MIN_ROOTS 2 /* RS(255, 253): ~0.8% space overhead */
17#define DM_VERITY_FEC_MAX_ROOTS 24 /* RS(255, 231): ~10% space overhead */
18
19/* buffers for deinterleaving and decoding */
20#define DM_VERITY_FEC_BUF_RS_BITS 4 /* log2(RS messages per buffer) */
21
22#define DM_VERITY_OPT_FEC_DEV "use_fec_from_device"
23#define DM_VERITY_OPT_FEC_BLOCKS "fec_blocks"
24#define DM_VERITY_OPT_FEC_START "fec_start"
25#define DM_VERITY_OPT_FEC_ROOTS "fec_roots"
26
27/* configuration */
28struct dm_verity_fec {
29 struct dm_dev *dev; /* parity data device */
30 struct dm_bufio_client *data_bufio; /* for data dev access */
31 struct dm_bufio_client *bufio; /* for parity data access */
32 size_t block_size; /* size of data, hash, and parity blocks in bytes */
33 sector_t start; /* parity data start in blocks */
34 sector_t blocks; /* number of blocks covered */
35 sector_t region_blocks; /* blocks per region: ceil(blocks / rs_k) */
36 sector_t hash_blocks; /* blocks covered after v->hash_start */
37 unsigned char roots; /* parity bytes per RS codeword, n-k of RS(n, k) */
38 unsigned char rs_k; /* message bytes per RS codeword, k of RS(n, k) */
39 mempool_t fio_pool; /* mempool for dm_verity_fec_io */
40 mempool_t rs_pool; /* mempool for fio->rs */
41 mempool_t prealloc_pool; /* mempool for preallocated buffers */
42 mempool_t output_pool; /* mempool for output */
43 struct kmem_cache *cache; /* cache for buffers */
44 atomic64_t corrected; /* corrected errors */
45};
46
47/* per-bio data */
48struct dm_verity_fec_io {
49 struct rs_control *rs; /* Reed-Solomon state */
50 int erasures[DM_VERITY_FEC_MAX_ROOTS + 1]; /* erasures for decode_rs8 */
51 u8 *output; /* buffer for corrected output */
52 unsigned int level; /* recursion level */
53 unsigned int nbufs; /* number of buffers allocated */
54 /*
55 * Buffers for deinterleaving RS codewords. Each buffer has space for
56 * the message bytes of (1 << DM_VERITY_FEC_BUF_RS_BITS) RS codewords.
57 * The array length is fec_max_nbufs(v), and we try to allocate that
58 * many buffers. However, in low-memory situations we may be unable to
59 * allocate all buffers. 'nbufs' holds the number actually allocated.
60 */
61 u8 *bufs[];
62};
63
64#ifdef CONFIG_DM_VERITY_FEC
65
66/* each feature parameter requires a value */
67#define DM_VERITY_OPTS_FEC 8
68
69/* Returns true if forward error correction is enabled. */
70static inline bool verity_fec_is_enabled(struct dm_verity *v)
71{
72 return v->fec && v->fec->dev;
73}
74
75extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
76 enum verity_block_type type, const u8 *want_digest,
77 sector_t block, u8 *dest);
78
79extern unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz,
80 char *result, unsigned int maxlen);
81
82extern void __verity_fec_finish_io(struct dm_verity_io *io);
83static inline void verity_fec_finish_io(struct dm_verity_io *io)
84{
85 if (unlikely(io->fec_io))
86 __verity_fec_finish_io(io);
87}
88
89static inline void verity_fec_init_io(struct dm_verity_io *io)
90{
91 io->fec_io = NULL;
92}
93
94extern bool verity_is_fec_opt_arg(const char *arg_name);
95extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
96 struct dm_verity *v, unsigned int *argc,
97 const char *arg_name);
98
99extern void verity_fec_dtr(struct dm_verity *v);
100
101extern int verity_fec_ctr_alloc(struct dm_verity *v);
102extern int verity_fec_ctr(struct dm_verity *v);
103
104#else /* !CONFIG_DM_VERITY_FEC */
105
106#define DM_VERITY_OPTS_FEC 0
107
108static inline bool verity_fec_is_enabled(struct dm_verity *v)
109{
110 return false;
111}
112
113static inline int verity_fec_decode(struct dm_verity *v,
114 struct dm_verity_io *io,
115 enum verity_block_type type,
116 const u8 *want_digest,
117 sector_t block, u8 *dest)
118{
119 return -EOPNOTSUPP;
120}
121
122static inline unsigned int verity_fec_status_table(struct dm_verity *v,
123 unsigned int sz, char *result,
124 unsigned int maxlen)
125{
126 return sz;
127}
128
129static inline void verity_fec_finish_io(struct dm_verity_io *io)
130{
131}
132
133static inline void verity_fec_init_io(struct dm_verity_io *io)
134{
135}
136
137static inline bool verity_is_fec_opt_arg(const char *arg_name)
138{
139 return false;
140}
141
142static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
143 struct dm_verity *v,
144 unsigned int *argc,
145 const char *arg_name)
146{
147 return -EINVAL;
148}
149
150static inline void verity_fec_dtr(struct dm_verity *v)
151{
152}
153
154static inline int verity_fec_ctr_alloc(struct dm_verity *v)
155{
156 return 0;
157}
158
159static inline int verity_fec_ctr(struct dm_verity *v)
160{
161 return 0;
162}
163
164#endif /* CONFIG_DM_VERITY_FEC */
165
166#endif /* DM_VERITY_FEC_H */