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 #include "dm-verity-fec.h"
9 #include <linux/math64.h>
10 
11 #define DM_MSG_PREFIX	"verity-fec"
12 
13 /*
14  * If error correction has been configured, returns true.
15  */
verity_fec_is_enabled(struct dm_verity * v)16 bool verity_fec_is_enabled(struct dm_verity *v)
17 {
18 	return v->fec && v->fec->dev;
19 }
20 
21 /*
22  * Return a pointer to dm_verity_fec_io after dm_verity_io and its variable
23  * length fields.
24  */
fec_io(struct dm_verity_io * io)25 static inline struct dm_verity_fec_io *fec_io(struct dm_verity_io *io)
26 {
27 	return (struct dm_verity_fec_io *)
28 		((char *)io + io->v->ti->per_io_data_size - sizeof(struct dm_verity_fec_io));
29 }
30 
31 /*
32  * Return an interleaved offset for a byte in RS block.
33  */
fec_interleave(struct dm_verity * v,u64 offset)34 static inline u64 fec_interleave(struct dm_verity *v, u64 offset)
35 {
36 	u32 mod;
37 
38 	mod = do_div(offset, v->fec->rsn);
39 	return offset + mod * (v->fec->rounds << v->data_dev_block_bits);
40 }
41 
42 /*
43  * Decode an RS block using Reed-Solomon.
44  */
fec_decode_rs8(struct dm_verity * v,struct dm_verity_fec_io * fio,u8 * data,u8 * fec,int neras)45 static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,
46 			  u8 *data, u8 *fec, int neras)
47 {
48 	int i;
49 	uint16_t par[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
50 
51 	for (i = 0; i < v->fec->roots; i++)
52 		par[i] = fec[i];
53 
54 	return decode_rs8(fio->rs, data, par, v->fec->rsn, NULL, neras,
55 			  fio->erasures, 0, NULL);
56 }
57 
58 /*
59  * Read error-correcting codes for the requested RS block. Returns a pointer
60  * to the data block. Caller is responsible for releasing buf.
61  */
fec_read_parity(struct dm_verity * v,u64 rsb,int index,unsigned int * offset,struct dm_buffer ** buf,unsigned short ioprio)62 static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
63 			   unsigned int *offset, struct dm_buffer **buf,
64 			   unsigned short ioprio)
65 {
66 	u64 position, block, rem;
67 	u8 *res;
68 
69 	position = (index + rsb) * v->fec->roots;
70 	block = div64_u64_rem(position, v->fec->io_size, &rem);
71 	*offset = (unsigned int)rem;
72 
73 	res = dm_bufio_read_with_ioprio(v->fec->bufio, block, buf, ioprio);
74 	if (IS_ERR(res)) {
75 		DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
76 		      v->data_dev->name, (unsigned long long)rsb,
77 		      (unsigned long long)block, PTR_ERR(res));
78 		*buf = NULL;
79 	}
80 
81 	return res;
82 }
83 
84 /* Loop over each preallocated buffer slot. */
85 #define fec_for_each_prealloc_buffer(__i) \
86 	for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
87 
88 /* Loop over each extra buffer slot. */
89 #define fec_for_each_extra_buffer(io, __i) \
90 	for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
91 
92 /* Loop over each allocated buffer. */
93 #define fec_for_each_buffer(io, __i) \
94 	for (__i = 0; __i < (io)->nbufs; __i++)
95 
96 /* Loop over each RS block in each allocated buffer. */
97 #define fec_for_each_buffer_rs_block(io, __i, __j) \
98 	fec_for_each_buffer(io, __i) \
99 		for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
100 
101 /*
102  * Return a pointer to the current RS block when called inside
103  * fec_for_each_buffer_rs_block.
104  */
fec_buffer_rs_block(struct dm_verity * v,struct dm_verity_fec_io * fio,unsigned int i,unsigned int j)105 static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
106 				      struct dm_verity_fec_io *fio,
107 				      unsigned int i, unsigned int j)
108 {
109 	return &fio->bufs[i][j * v->fec->rsn];
110 }
111 
112 /*
113  * Return an index to the current RS block when called inside
114  * fec_for_each_buffer_rs_block.
115  */
fec_buffer_rs_index(unsigned int i,unsigned int j)116 static inline unsigned int fec_buffer_rs_index(unsigned int i, unsigned int j)
117 {
118 	return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
119 }
120 
121 /*
122  * Decode all RS blocks from buffers and copy corrected bytes into fio->output
123  * starting from block_offset.
124  */
fec_decode_bufs(struct dm_verity * v,struct dm_verity_io * io,struct dm_verity_fec_io * fio,u64 rsb,int byte_index,unsigned int block_offset,int neras)125 static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
126 			   struct dm_verity_fec_io *fio, u64 rsb, int byte_index,
127 			   unsigned int block_offset, int neras)
128 {
129 	int r, corrected = 0, res;
130 	struct dm_buffer *buf;
131 	unsigned int n, i, offset;
132 	u8 *par, *block;
133 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
134 
135 	par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
136 	if (IS_ERR(par))
137 		return PTR_ERR(par);
138 
139 	/*
140 	 * Decode the RS blocks we have in bufs. Each RS block results in
141 	 * one corrected target byte and consumes fec->roots parity bytes.
142 	 */
143 	fec_for_each_buffer_rs_block(fio, n, i) {
144 		block = fec_buffer_rs_block(v, fio, n, i);
145 		res = fec_decode_rs8(v, fio, block, &par[offset], neras);
146 		if (res < 0) {
147 			r = res;
148 			goto error;
149 		}
150 
151 		corrected += res;
152 		fio->output[block_offset] = block[byte_index];
153 
154 		block_offset++;
155 		if (block_offset >= 1 << v->data_dev_block_bits)
156 			goto done;
157 
158 		/* read the next block when we run out of parity bytes */
159 		offset += v->fec->roots;
160 		if (offset >= v->fec->io_size) {
161 			dm_bufio_release(buf);
162 
163 			par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
164 			if (IS_ERR(par))
165 				return PTR_ERR(par);
166 		}
167 	}
168 done:
169 	r = corrected;
170 error:
171 	dm_bufio_release(buf);
172 
173 	if (r < 0 && neras)
174 		DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
175 			    v->data_dev->name, (unsigned long long)rsb, r);
176 	else if (r > 0)
177 		DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
178 			     v->data_dev->name, (unsigned long long)rsb, r);
179 
180 	return r;
181 }
182 
183 /*
184  * Locate data block erasures using verity hashes.
185  */
fec_is_erasure(struct dm_verity * v,struct dm_verity_io * io,u8 * want_digest,u8 * data)186 static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
187 			  u8 *want_digest, u8 *data)
188 {
189 	if (unlikely(verity_hash(v, io, data, 1 << v->data_dev_block_bits,
190 				 verity_io_real_digest(v, io), true)))
191 		return 0;
192 
193 	return memcmp(verity_io_real_digest(v, io), want_digest,
194 		      v->digest_size) != 0;
195 }
196 
197 /*
198  * Read data blocks that are part of the RS block and deinterleave as much as
199  * fits into buffers. Check for erasure locations if @neras is non-NULL.
200  */
fec_read_bufs(struct dm_verity * v,struct dm_verity_io * io,u64 rsb,u64 target,unsigned int block_offset,int * neras)201 static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
202 			 u64 rsb, u64 target, unsigned int block_offset,
203 			 int *neras)
204 {
205 	bool is_zero;
206 	int i, j, target_index = -1;
207 	struct dm_buffer *buf;
208 	struct dm_bufio_client *bufio;
209 	struct dm_verity_fec_io *fio = fec_io(io);
210 	u64 block, ileaved;
211 	u8 *bbuf, *rs_block;
212 	u8 want_digest[HASH_MAX_DIGESTSIZE];
213 	unsigned int n, k;
214 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
215 
216 	if (neras)
217 		*neras = 0;
218 
219 	if (WARN_ON(v->digest_size > sizeof(want_digest)))
220 		return -EINVAL;
221 
222 	/*
223 	 * read each of the rsn data blocks that are part of the RS block, and
224 	 * interleave contents to available bufs
225 	 */
226 	for (i = 0; i < v->fec->rsn; i++) {
227 		ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
228 
229 		/*
230 		 * target is the data block we want to correct, target_index is
231 		 * the index of this block within the rsn RS blocks
232 		 */
233 		if (ileaved == target)
234 			target_index = i;
235 
236 		block = ileaved >> v->data_dev_block_bits;
237 		bufio = v->fec->data_bufio;
238 
239 		if (block >= v->data_blocks) {
240 			block -= v->data_blocks;
241 
242 			/*
243 			 * blocks outside the area were assumed to contain
244 			 * zeros when encoding data was generated
245 			 */
246 			if (unlikely(block >= v->fec->hash_blocks))
247 				continue;
248 
249 			block += v->hash_start;
250 			bufio = v->bufio;
251 		}
252 
253 		bbuf = dm_bufio_read_with_ioprio(bufio, block, &buf, bio_prio(bio));
254 		if (IS_ERR(bbuf)) {
255 			DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
256 				     v->data_dev->name,
257 				     (unsigned long long)rsb,
258 				     (unsigned long long)block, PTR_ERR(bbuf));
259 
260 			/* assume the block is corrupted */
261 			if (neras && *neras <= v->fec->roots)
262 				fio->erasures[(*neras)++] = i;
263 
264 			continue;
265 		}
266 
267 		/* locate erasures if the block is on the data device */
268 		if (bufio == v->fec->data_bufio &&
269 		    verity_hash_for_block(v, io, block, want_digest,
270 					  &is_zero) == 0) {
271 			/* skip known zero blocks entirely */
272 			if (is_zero)
273 				goto done;
274 
275 			/*
276 			 * skip if we have already found the theoretical
277 			 * maximum number (i.e. fec->roots) of erasures
278 			 */
279 			if (neras && *neras <= v->fec->roots &&
280 			    fec_is_erasure(v, io, want_digest, bbuf))
281 				fio->erasures[(*neras)++] = i;
282 		}
283 
284 		/*
285 		 * deinterleave and copy the bytes that fit into bufs,
286 		 * starting from block_offset
287 		 */
288 		fec_for_each_buffer_rs_block(fio, n, j) {
289 			k = fec_buffer_rs_index(n, j) + block_offset;
290 
291 			if (k >= 1 << v->data_dev_block_bits)
292 				goto done;
293 
294 			rs_block = fec_buffer_rs_block(v, fio, n, j);
295 			rs_block[i] = bbuf[k];
296 		}
297 done:
298 		dm_bufio_release(buf);
299 	}
300 
301 	return target_index;
302 }
303 
304 /*
305  * Allocate RS control structure and FEC buffers from preallocated mempools,
306  * and attempt to allocate as many extra buffers as available.
307  */
fec_alloc_bufs(struct dm_verity * v,struct dm_verity_fec_io * fio)308 static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
309 {
310 	unsigned int n;
311 
312 	if (!fio->rs)
313 		fio->rs = mempool_alloc(&v->fec->rs_pool, GFP_NOIO);
314 
315 	fec_for_each_prealloc_buffer(n) {
316 		if (fio->bufs[n])
317 			continue;
318 
319 		fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOWAIT);
320 		if (unlikely(!fio->bufs[n])) {
321 			DMERR("failed to allocate FEC buffer");
322 			return -ENOMEM;
323 		}
324 	}
325 
326 	/* try to allocate the maximum number of buffers */
327 	fec_for_each_extra_buffer(fio, n) {
328 		if (fio->bufs[n])
329 			continue;
330 
331 		fio->bufs[n] = mempool_alloc(&v->fec->extra_pool, GFP_NOWAIT);
332 		/* we can manage with even one buffer if necessary */
333 		if (unlikely(!fio->bufs[n]))
334 			break;
335 	}
336 	fio->nbufs = n;
337 
338 	if (!fio->output)
339 		fio->output = mempool_alloc(&v->fec->output_pool, GFP_NOIO);
340 
341 	return 0;
342 }
343 
344 /*
345  * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
346  * zeroed before deinterleaving.
347  */
fec_init_bufs(struct dm_verity * v,struct dm_verity_fec_io * fio)348 static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
349 {
350 	unsigned int n;
351 
352 	fec_for_each_buffer(fio, n)
353 		memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
354 
355 	memset(fio->erasures, 0, sizeof(fio->erasures));
356 }
357 
358 /*
359  * Decode all RS blocks in a single data block and return the target block
360  * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
361  * hashes to locate erasures.
362  */
fec_decode_rsb(struct dm_verity * v,struct dm_verity_io * io,struct dm_verity_fec_io * fio,u64 rsb,u64 offset,bool use_erasures)363 static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
364 			  struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
365 			  bool use_erasures)
366 {
367 	int r, neras = 0;
368 	unsigned int pos;
369 
370 	r = fec_alloc_bufs(v, fio);
371 	if (unlikely(r < 0))
372 		return r;
373 
374 	for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
375 		fec_init_bufs(v, fio);
376 
377 		r = fec_read_bufs(v, io, rsb, offset, pos,
378 				  use_erasures ? &neras : NULL);
379 		if (unlikely(r < 0))
380 			return r;
381 
382 		r = fec_decode_bufs(v, io, fio, rsb, r, pos, neras);
383 		if (r < 0)
384 			return r;
385 
386 		pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
387 	}
388 
389 	/* Always re-validate the corrected block against the expected hash */
390 	r = verity_hash(v, io, fio->output, 1 << v->data_dev_block_bits,
391 			verity_io_real_digest(v, io), true);
392 	if (unlikely(r < 0))
393 		return r;
394 
395 	if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io),
396 		   v->digest_size)) {
397 		DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
398 			    v->data_dev->name, (unsigned long long)rsb, neras);
399 		return -EILSEQ;
400 	}
401 
402 	return 0;
403 }
404 
405 /* Correct errors in a block. Copies corrected block to dest. */
verity_fec_decode(struct dm_verity * v,struct dm_verity_io * io,enum verity_block_type type,sector_t block,u8 * dest)406 int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
407 		      enum verity_block_type type, sector_t block, u8 *dest)
408 {
409 	int r;
410 	struct dm_verity_fec_io *fio = fec_io(io);
411 	u64 offset, res, rsb;
412 
413 	if (!verity_fec_is_enabled(v))
414 		return -EOPNOTSUPP;
415 
416 	if (fio->level >= DM_VERITY_FEC_MAX_RECURSION) {
417 		DMWARN_LIMIT("%s: FEC: recursion too deep", v->data_dev->name);
418 		return -EIO;
419 	}
420 
421 	fio->level++;
422 
423 	if (type == DM_VERITY_BLOCK_TYPE_METADATA)
424 		block = block - v->hash_start + v->data_blocks;
425 
426 	/*
427 	 * For RS(M, N), the continuous FEC data is divided into blocks of N
428 	 * bytes. Since block size may not be divisible by N, the last block
429 	 * is zero padded when decoding.
430 	 *
431 	 * Each byte of the block is covered by a different RS(M, N) code,
432 	 * and each code is interleaved over N blocks to make it less likely
433 	 * that bursty corruption will leave us in unrecoverable state.
434 	 */
435 
436 	offset = block << v->data_dev_block_bits;
437 	res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
438 
439 	/*
440 	 * The base RS block we can feed to the interleaver to find out all
441 	 * blocks required for decoding.
442 	 */
443 	rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
444 
445 	/*
446 	 * Locating erasures is slow, so attempt to recover the block without
447 	 * them first. Do a second attempt with erasures if the corruption is
448 	 * bad enough.
449 	 */
450 	r = fec_decode_rsb(v, io, fio, rsb, offset, false);
451 	if (r < 0) {
452 		r = fec_decode_rsb(v, io, fio, rsb, offset, true);
453 		if (r < 0)
454 			goto done;
455 	}
456 
457 	memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
458 
459 done:
460 	fio->level--;
461 	return r;
462 }
463 
464 /*
465  * Clean up per-bio data.
466  */
verity_fec_finish_io(struct dm_verity_io * io)467 void verity_fec_finish_io(struct dm_verity_io *io)
468 {
469 	unsigned int n;
470 	struct dm_verity_fec *f = io->v->fec;
471 	struct dm_verity_fec_io *fio = fec_io(io);
472 
473 	if (!verity_fec_is_enabled(io->v))
474 		return;
475 
476 	mempool_free(fio->rs, &f->rs_pool);
477 
478 	fec_for_each_prealloc_buffer(n)
479 		mempool_free(fio->bufs[n], &f->prealloc_pool);
480 
481 	fec_for_each_extra_buffer(fio, n)
482 		mempool_free(fio->bufs[n], &f->extra_pool);
483 
484 	mempool_free(fio->output, &f->output_pool);
485 }
486 
487 /*
488  * Initialize per-bio data.
489  */
verity_fec_init_io(struct dm_verity_io * io)490 void verity_fec_init_io(struct dm_verity_io *io)
491 {
492 	struct dm_verity_fec_io *fio = fec_io(io);
493 
494 	if (!verity_fec_is_enabled(io->v))
495 		return;
496 
497 	fio->rs = NULL;
498 	memset(fio->bufs, 0, sizeof(fio->bufs));
499 	fio->nbufs = 0;
500 	fio->output = NULL;
501 	fio->level = 0;
502 }
503 
504 /*
505  * Append feature arguments and values to the status table.
506  */
verity_fec_status_table(struct dm_verity * v,unsigned int sz,char * result,unsigned int maxlen)507 unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz,
508 				 char *result, unsigned int maxlen)
509 {
510 	if (!verity_fec_is_enabled(v))
511 		return sz;
512 
513 	DMEMIT(" " DM_VERITY_OPT_FEC_DEV " %s "
514 	       DM_VERITY_OPT_FEC_BLOCKS " %llu "
515 	       DM_VERITY_OPT_FEC_START " %llu "
516 	       DM_VERITY_OPT_FEC_ROOTS " %d",
517 	       v->fec->dev->name,
518 	       (unsigned long long)v->fec->blocks,
519 	       (unsigned long long)v->fec->start,
520 	       v->fec->roots);
521 
522 	return sz;
523 }
524 
verity_fec_dtr(struct dm_verity * v)525 void verity_fec_dtr(struct dm_verity *v)
526 {
527 	struct dm_verity_fec *f = v->fec;
528 
529 	if (!verity_fec_is_enabled(v))
530 		goto out;
531 
532 	mempool_exit(&f->rs_pool);
533 	mempool_exit(&f->prealloc_pool);
534 	mempool_exit(&f->extra_pool);
535 	mempool_exit(&f->output_pool);
536 	kmem_cache_destroy(f->cache);
537 
538 	if (f->data_bufio)
539 		dm_bufio_client_destroy(f->data_bufio);
540 	if (f->bufio)
541 		dm_bufio_client_destroy(f->bufio);
542 
543 	if (f->dev)
544 		dm_put_device(v->ti, f->dev);
545 out:
546 	kfree(f);
547 	v->fec = NULL;
548 }
549 
fec_rs_alloc(gfp_t gfp_mask,void * pool_data)550 static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
551 {
552 	struct dm_verity *v = pool_data;
553 
554 	return init_rs_gfp(8, 0x11d, 0, 1, v->fec->roots, gfp_mask);
555 }
556 
fec_rs_free(void * element,void * pool_data)557 static void fec_rs_free(void *element, void *pool_data)
558 {
559 	struct rs_control *rs = element;
560 
561 	if (rs)
562 		free_rs(rs);
563 }
564 
verity_is_fec_opt_arg(const char * arg_name)565 bool verity_is_fec_opt_arg(const char *arg_name)
566 {
567 	return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
568 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
569 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
570 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
571 }
572 
verity_fec_parse_opt_args(struct dm_arg_set * as,struct dm_verity * v,unsigned int * argc,const char * arg_name)573 int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
574 			      unsigned int *argc, const char *arg_name)
575 {
576 	int r;
577 	struct dm_target *ti = v->ti;
578 	const char *arg_value;
579 	unsigned long long num_ll;
580 	unsigned char num_c;
581 	char dummy;
582 
583 	if (!*argc) {
584 		ti->error = "FEC feature arguments require a value";
585 		return -EINVAL;
586 	}
587 
588 	arg_value = dm_shift_arg(as);
589 	(*argc)--;
590 
591 	if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
592 		r = dm_get_device(ti, arg_value, BLK_OPEN_READ, &v->fec->dev);
593 		if (r) {
594 			ti->error = "FEC device lookup failed";
595 			return r;
596 		}
597 
598 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
599 		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
600 		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
601 		     >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
602 			ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
603 			return -EINVAL;
604 		}
605 		v->fec->blocks = num_ll;
606 
607 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
608 		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
609 		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
610 		     (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
611 			ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
612 			return -EINVAL;
613 		}
614 		v->fec->start = num_ll;
615 
616 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
617 		if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
618 		    num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
619 		    num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
620 			ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
621 			return -EINVAL;
622 		}
623 		v->fec->roots = num_c;
624 
625 	} else {
626 		ti->error = "Unrecognized verity FEC feature request";
627 		return -EINVAL;
628 	}
629 
630 	return 0;
631 }
632 
633 /*
634  * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
635  */
verity_fec_ctr_alloc(struct dm_verity * v)636 int verity_fec_ctr_alloc(struct dm_verity *v)
637 {
638 	struct dm_verity_fec *f;
639 
640 	f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
641 	if (!f) {
642 		v->ti->error = "Cannot allocate FEC structure";
643 		return -ENOMEM;
644 	}
645 	v->fec = f;
646 
647 	return 0;
648 }
649 
650 /*
651  * Validate arguments and preallocate memory. Must be called after arguments
652  * have been parsed using verity_fec_parse_opt_args.
653  */
verity_fec_ctr(struct dm_verity * v)654 int verity_fec_ctr(struct dm_verity *v)
655 {
656 	struct dm_verity_fec *f = v->fec;
657 	struct dm_target *ti = v->ti;
658 	u64 hash_blocks, fec_blocks;
659 	int ret;
660 
661 	if (!verity_fec_is_enabled(v)) {
662 		verity_fec_dtr(v);
663 		return 0;
664 	}
665 
666 	/*
667 	 * FEC is computed over data blocks, possible metadata, and
668 	 * hash blocks. In other words, FEC covers total of fec_blocks
669 	 * blocks consisting of the following:
670 	 *
671 	 *  data blocks | hash blocks | metadata (optional)
672 	 *
673 	 * We allow metadata after hash blocks to support a use case
674 	 * where all data is stored on the same device and FEC covers
675 	 * the entire area.
676 	 *
677 	 * If metadata is included, we require it to be available on the
678 	 * hash device after the hash blocks.
679 	 */
680 
681 	hash_blocks = v->hash_blocks - v->hash_start;
682 
683 	/*
684 	 * Require matching block sizes for data and hash devices for
685 	 * simplicity.
686 	 */
687 	if (v->data_dev_block_bits != v->hash_dev_block_bits) {
688 		ti->error = "Block sizes must match to use FEC";
689 		return -EINVAL;
690 	}
691 
692 	if (!f->roots) {
693 		ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
694 		return -EINVAL;
695 	}
696 	f->rsn = DM_VERITY_FEC_RSM - f->roots;
697 
698 	if (!f->blocks) {
699 		ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
700 		return -EINVAL;
701 	}
702 
703 	f->rounds = f->blocks;
704 	if (sector_div(f->rounds, f->rsn))
705 		f->rounds++;
706 
707 	/*
708 	 * Due to optional metadata, f->blocks can be larger than
709 	 * data_blocks and hash_blocks combined.
710 	 */
711 	if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
712 		ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
713 		return -EINVAL;
714 	}
715 
716 	/*
717 	 * Metadata is accessed through the hash device, so we require
718 	 * it to be large enough.
719 	 */
720 	f->hash_blocks = f->blocks - v->data_blocks;
721 	if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
722 		ti->error = "Hash device is too small for "
723 			DM_VERITY_OPT_FEC_BLOCKS;
724 		return -E2BIG;
725 	}
726 
727 	if ((f->roots << SECTOR_SHIFT) & ((1 << v->data_dev_block_bits) - 1))
728 		f->io_size = 1 << v->data_dev_block_bits;
729 	else
730 		f->io_size = v->fec->roots << SECTOR_SHIFT;
731 
732 	f->bufio = dm_bufio_client_create(f->dev->bdev,
733 					  f->io_size,
734 					  1, 0, NULL, NULL, 0);
735 	if (IS_ERR(f->bufio)) {
736 		ti->error = "Cannot initialize FEC bufio client";
737 		return PTR_ERR(f->bufio);
738 	}
739 
740 	dm_bufio_set_sector_offset(f->bufio, f->start << (v->data_dev_block_bits - SECTOR_SHIFT));
741 
742 	fec_blocks = div64_u64(f->rounds * f->roots, v->fec->roots << SECTOR_SHIFT);
743 	if (dm_bufio_get_device_size(f->bufio) < fec_blocks) {
744 		ti->error = "FEC device is too small";
745 		return -E2BIG;
746 	}
747 
748 	f->data_bufio = dm_bufio_client_create(v->data_dev->bdev,
749 					       1 << v->data_dev_block_bits,
750 					       1, 0, NULL, NULL, 0);
751 	if (IS_ERR(f->data_bufio)) {
752 		ti->error = "Cannot initialize FEC data bufio client";
753 		return PTR_ERR(f->data_bufio);
754 	}
755 
756 	if (dm_bufio_get_device_size(f->data_bufio) < v->data_blocks) {
757 		ti->error = "Data device is too small";
758 		return -E2BIG;
759 	}
760 
761 	/* Preallocate an rs_control structure for each worker thread */
762 	ret = mempool_init(&f->rs_pool, num_online_cpus(), fec_rs_alloc,
763 			   fec_rs_free, (void *) v);
764 	if (ret) {
765 		ti->error = "Cannot allocate RS pool";
766 		return ret;
767 	}
768 
769 	f->cache = kmem_cache_create("dm_verity_fec_buffers",
770 				     f->rsn << DM_VERITY_FEC_BUF_RS_BITS,
771 				     0, 0, NULL);
772 	if (!f->cache) {
773 		ti->error = "Cannot create FEC buffer cache";
774 		return -ENOMEM;
775 	}
776 
777 	/* Preallocate DM_VERITY_FEC_BUF_PREALLOC buffers for each thread */
778 	ret = mempool_init_slab_pool(&f->prealloc_pool, num_online_cpus() *
779 				     DM_VERITY_FEC_BUF_PREALLOC,
780 				     f->cache);
781 	if (ret) {
782 		ti->error = "Cannot allocate FEC buffer prealloc pool";
783 		return ret;
784 	}
785 
786 	ret = mempool_init_slab_pool(&f->extra_pool, 0, f->cache);
787 	if (ret) {
788 		ti->error = "Cannot allocate FEC buffer extra pool";
789 		return ret;
790 	}
791 
792 	/* Preallocate an output buffer for each thread */
793 	ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
794 					1 << v->data_dev_block_bits);
795 	if (ret) {
796 		ti->error = "Cannot allocate FEC output pool";
797 		return ret;
798 	}
799 
800 	/* Reserve space for our per-bio data */
801 	ti->per_io_data_size += sizeof(struct dm_verity_fec_io);
802 
803 	return 0;
804 }
805