xref: /openbmc/linux/drivers/md/dm-verity-fec.c (revision d32fd6bb9f2bc8178cdd65ebec1ad670a8bfa241)
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,unsigned int par_buf_offset,struct dm_buffer ** buf)62 static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
63 			   unsigned int *offset, unsigned int par_buf_offset,
64 			  struct dm_buffer **buf)
65 {
66 	u64 position, block, rem;
67 	u8 *res;
68 
69 	/* We have already part of parity bytes read, skip to the next block */
70 	if (par_buf_offset)
71 		index++;
72 
73 	position = (index + rsb) * v->fec->roots;
74 	block = div64_u64_rem(position, v->fec->io_size, &rem);
75 	*offset = par_buf_offset ? 0 : (unsigned int)rem;
76 
77 	res = dm_bufio_read(v->fec->bufio, block, buf);
78 	if (IS_ERR(res)) {
79 		DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
80 		      v->data_dev->name, (unsigned long long)rsb,
81 		      (unsigned long long)block, PTR_ERR(res));
82 		*buf = NULL;
83 	}
84 
85 	return res;
86 }
87 
88 /* Loop over each preallocated buffer slot. */
89 #define fec_for_each_prealloc_buffer(__i) \
90 	for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
91 
92 /* Loop over each extra buffer slot. */
93 #define fec_for_each_extra_buffer(io, __i) \
94 	for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
95 
96 /* Loop over each allocated buffer. */
97 #define fec_for_each_buffer(io, __i) \
98 	for (__i = 0; __i < (io)->nbufs; __i++)
99 
100 /* Loop over each RS block in each allocated buffer. */
101 #define fec_for_each_buffer_rs_block(io, __i, __j) \
102 	fec_for_each_buffer(io, __i) \
103 		for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
104 
105 /*
106  * Return a pointer to the current RS block when called inside
107  * fec_for_each_buffer_rs_block.
108  */
fec_buffer_rs_block(struct dm_verity * v,struct dm_verity_fec_io * fio,unsigned int i,unsigned int j)109 static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
110 				      struct dm_verity_fec_io *fio,
111 				      unsigned int i, unsigned int j)
112 {
113 	return &fio->bufs[i][j * v->fec->rsn];
114 }
115 
116 /*
117  * Return an index to the current RS block when called inside
118  * fec_for_each_buffer_rs_block.
119  */
fec_buffer_rs_index(unsigned int i,unsigned int j)120 static inline unsigned int fec_buffer_rs_index(unsigned int i, unsigned int j)
121 {
122 	return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
123 }
124 
125 /*
126  * Decode all RS blocks from buffers and copy corrected bytes into fio->output
127  * starting from block_offset.
128  */
fec_decode_bufs(struct dm_verity * v,struct dm_verity_fec_io * fio,u64 rsb,int byte_index,unsigned int block_offset,int neras)129 static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
130 			   u64 rsb, int byte_index, unsigned int block_offset,
131 			   int neras)
132 {
133 	int r, corrected = 0, res;
134 	struct dm_buffer *buf;
135 	unsigned int n, i, offset, par_buf_offset = 0;
136 	u8 *par, *block, par_buf[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
137 
138 	par = fec_read_parity(v, rsb, block_offset, &offset,
139 			      par_buf_offset, &buf);
140 	if (IS_ERR(par))
141 		return PTR_ERR(par);
142 
143 	/*
144 	 * Decode the RS blocks we have in bufs. Each RS block results in
145 	 * one corrected target byte and consumes fec->roots parity bytes.
146 	 */
147 	fec_for_each_buffer_rs_block(fio, n, i) {
148 		block = fec_buffer_rs_block(v, fio, n, i);
149 		memcpy(&par_buf[par_buf_offset], &par[offset], v->fec->roots - par_buf_offset);
150 		res = fec_decode_rs8(v, fio, block, par_buf, neras);
151 		if (res < 0) {
152 			r = res;
153 			goto error;
154 		}
155 
156 		corrected += res;
157 		fio->output[block_offset] = block[byte_index];
158 
159 		block_offset++;
160 		if (block_offset >= 1 << v->data_dev_block_bits)
161 			goto done;
162 
163 		/* Read the next block when we run out of parity bytes */
164 		offset += (v->fec->roots - par_buf_offset);
165 		/* Check if parity bytes are split between blocks */
166 		if (offset < v->fec->io_size && (offset + v->fec->roots) > v->fec->io_size) {
167 			par_buf_offset = v->fec->io_size - offset;
168 			memcpy(par_buf, &par[offset], par_buf_offset);
169 			offset += par_buf_offset;
170 		} else
171 			par_buf_offset = 0;
172 
173 		if (offset >= v->fec->io_size) {
174 			dm_bufio_release(buf);
175 
176 			par = fec_read_parity(v, rsb, block_offset, &offset,
177 					      par_buf_offset, &buf);
178 			if (IS_ERR(par))
179 				return PTR_ERR(par);
180 		}
181 	}
182 done:
183 	r = corrected;
184 error:
185 	dm_bufio_release(buf);
186 
187 	if (r < 0 && neras)
188 		DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
189 			    v->data_dev->name, (unsigned long long)rsb, r);
190 	else if (r > 0)
191 		DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
192 			     v->data_dev->name, (unsigned long long)rsb, r);
193 
194 	return r;
195 }
196 
197 /*
198  * Locate data block erasures using verity hashes.
199  */
fec_is_erasure(struct dm_verity * v,struct dm_verity_io * io,u8 * want_digest,u8 * data)200 static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
201 			  u8 *want_digest, u8 *data)
202 {
203 	if (unlikely(verity_hash(v, verity_io_hash_req(v, io),
204 				 data, 1 << v->data_dev_block_bits,
205 				 verity_io_real_digest(v, io), true)))
206 		return 0;
207 
208 	return memcmp(verity_io_real_digest(v, io), want_digest,
209 		      v->digest_size) != 0;
210 }
211 
212 /*
213  * Read data blocks that are part of the RS block and deinterleave as much as
214  * fits into buffers. Check for erasure locations if @neras is non-NULL.
215  */
fec_read_bufs(struct dm_verity * v,struct dm_verity_io * io,u64 rsb,u64 target,unsigned int block_offset,int * neras)216 static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
217 			 u64 rsb, u64 target, unsigned int block_offset,
218 			 int *neras)
219 {
220 	bool is_zero;
221 	int i, j, target_index = -1;
222 	struct dm_buffer *buf;
223 	struct dm_bufio_client *bufio;
224 	struct dm_verity_fec_io *fio = fec_io(io);
225 	u64 block, ileaved;
226 	u8 *bbuf, *rs_block;
227 	u8 want_digest[HASH_MAX_DIGESTSIZE];
228 	unsigned int n, k;
229 
230 	if (neras)
231 		*neras = 0;
232 
233 	if (WARN_ON(v->digest_size > sizeof(want_digest)))
234 		return -EINVAL;
235 
236 	/*
237 	 * read each of the rsn data blocks that are part of the RS block, and
238 	 * interleave contents to available bufs
239 	 */
240 	for (i = 0; i < v->fec->rsn; i++) {
241 		ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
242 
243 		/*
244 		 * target is the data block we want to correct, target_index is
245 		 * the index of this block within the rsn RS blocks
246 		 */
247 		if (ileaved == target)
248 			target_index = i;
249 
250 		block = ileaved >> v->data_dev_block_bits;
251 		bufio = v->fec->data_bufio;
252 
253 		if (block >= v->data_blocks) {
254 			block -= v->data_blocks;
255 
256 			/*
257 			 * blocks outside the area were assumed to contain
258 			 * zeros when encoding data was generated
259 			 */
260 			if (unlikely(block >= v->fec->hash_blocks))
261 				continue;
262 
263 			block += v->hash_start;
264 			bufio = v->bufio;
265 		}
266 
267 		bbuf = dm_bufio_read(bufio, block, &buf);
268 		if (IS_ERR(bbuf)) {
269 			DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
270 				     v->data_dev->name,
271 				     (unsigned long long)rsb,
272 				     (unsigned long long)block, PTR_ERR(bbuf));
273 
274 			/* assume the block is corrupted */
275 			if (neras && *neras <= v->fec->roots)
276 				fio->erasures[(*neras)++] = i;
277 
278 			continue;
279 		}
280 
281 		/* locate erasures if the block is on the data device */
282 		if (bufio == v->fec->data_bufio &&
283 		    verity_hash_for_block(v, io, block, want_digest,
284 					  &is_zero) == 0) {
285 			/* skip known zero blocks entirely */
286 			if (is_zero)
287 				goto done;
288 
289 			/*
290 			 * skip if we have already found the theoretical
291 			 * maximum number (i.e. fec->roots) of erasures
292 			 */
293 			if (neras && *neras <= v->fec->roots &&
294 			    fec_is_erasure(v, io, want_digest, bbuf))
295 				fio->erasures[(*neras)++] = i;
296 		}
297 
298 		/*
299 		 * deinterleave and copy the bytes that fit into bufs,
300 		 * starting from block_offset
301 		 */
302 		fec_for_each_buffer_rs_block(fio, n, j) {
303 			k = fec_buffer_rs_index(n, j) + block_offset;
304 
305 			if (k >= 1 << v->data_dev_block_bits)
306 				goto done;
307 
308 			rs_block = fec_buffer_rs_block(v, fio, n, j);
309 			rs_block[i] = bbuf[k];
310 		}
311 done:
312 		dm_bufio_release(buf);
313 	}
314 
315 	return target_index;
316 }
317 
318 /*
319  * Allocate RS control structure and FEC buffers from preallocated mempools,
320  * and attempt to allocate as many extra buffers as available.
321  */
fec_alloc_bufs(struct dm_verity * v,struct dm_verity_fec_io * fio)322 static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
323 {
324 	unsigned int n;
325 
326 	if (!fio->rs)
327 		fio->rs = mempool_alloc(&v->fec->rs_pool, GFP_NOIO);
328 
329 	fec_for_each_prealloc_buffer(n) {
330 		if (fio->bufs[n])
331 			continue;
332 
333 		fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOWAIT);
334 		if (unlikely(!fio->bufs[n])) {
335 			DMERR("failed to allocate FEC buffer");
336 			return -ENOMEM;
337 		}
338 	}
339 
340 	/* try to allocate the maximum number of buffers */
341 	fec_for_each_extra_buffer(fio, n) {
342 		if (fio->bufs[n])
343 			continue;
344 
345 		fio->bufs[n] = mempool_alloc(&v->fec->extra_pool, GFP_NOWAIT);
346 		/* we can manage with even one buffer if necessary */
347 		if (unlikely(!fio->bufs[n]))
348 			break;
349 	}
350 	fio->nbufs = n;
351 
352 	if (!fio->output)
353 		fio->output = mempool_alloc(&v->fec->output_pool, GFP_NOIO);
354 
355 	return 0;
356 }
357 
358 /*
359  * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
360  * zeroed before deinterleaving.
361  */
fec_init_bufs(struct dm_verity * v,struct dm_verity_fec_io * fio)362 static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
363 {
364 	unsigned int n;
365 
366 	fec_for_each_buffer(fio, n)
367 		memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
368 
369 	memset(fio->erasures, 0, sizeof(fio->erasures));
370 }
371 
372 /*
373  * Decode all RS blocks in a single data block and return the target block
374  * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
375  * hashes to locate erasures.
376  */
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)377 static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
378 			  struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
379 			  bool use_erasures)
380 {
381 	int r, neras = 0;
382 	unsigned int pos;
383 
384 	r = fec_alloc_bufs(v, fio);
385 	if (unlikely(r < 0))
386 		return r;
387 
388 	for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
389 		fec_init_bufs(v, fio);
390 
391 		r = fec_read_bufs(v, io, rsb, offset, pos,
392 				  use_erasures ? &neras : NULL);
393 		if (unlikely(r < 0))
394 			return r;
395 
396 		r = fec_decode_bufs(v, fio, rsb, r, pos, neras);
397 		if (r < 0)
398 			return r;
399 
400 		pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
401 	}
402 
403 	/* Always re-validate the corrected block against the expected hash */
404 	r = verity_hash(v, verity_io_hash_req(v, io), fio->output,
405 			1 << v->data_dev_block_bits,
406 			verity_io_real_digest(v, io), true);
407 	if (unlikely(r < 0))
408 		return r;
409 
410 	if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io),
411 		   v->digest_size)) {
412 		DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
413 			    v->data_dev->name, (unsigned long long)rsb, neras);
414 		return -EILSEQ;
415 	}
416 
417 	return 0;
418 }
419 
fec_bv_copy(struct dm_verity * v,struct dm_verity_io * io,u8 * data,size_t len)420 static int fec_bv_copy(struct dm_verity *v, struct dm_verity_io *io, u8 *data,
421 		       size_t len)
422 {
423 	struct dm_verity_fec_io *fio = fec_io(io);
424 
425 	memcpy(data, &fio->output[fio->output_pos], len);
426 	fio->output_pos += len;
427 
428 	return 0;
429 }
430 
431 /*
432  * Correct errors in a block. Copies corrected block to dest if non-NULL,
433  * otherwise to a bio_vec starting from iter.
434  */
verity_fec_decode(struct dm_verity * v,struct dm_verity_io * io,enum verity_block_type type,sector_t block,u8 * dest,struct bvec_iter * iter)435 int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
436 		      enum verity_block_type type, sector_t block, u8 *dest,
437 		      struct bvec_iter *iter)
438 {
439 	int r;
440 	struct dm_verity_fec_io *fio = fec_io(io);
441 	u64 offset, res, rsb;
442 
443 	if (!verity_fec_is_enabled(v))
444 		return -EOPNOTSUPP;
445 
446 	if (fio->level >= DM_VERITY_FEC_MAX_RECURSION) {
447 		DMWARN_LIMIT("%s: FEC: recursion too deep", v->data_dev->name);
448 		return -EIO;
449 	}
450 
451 	fio->level++;
452 
453 	if (type == DM_VERITY_BLOCK_TYPE_METADATA)
454 		block = block - v->hash_start + v->data_blocks;
455 
456 	/*
457 	 * For RS(M, N), the continuous FEC data is divided into blocks of N
458 	 * bytes. Since block size may not be divisible by N, the last block
459 	 * is zero padded when decoding.
460 	 *
461 	 * Each byte of the block is covered by a different RS(M, N) code,
462 	 * and each code is interleaved over N blocks to make it less likely
463 	 * that bursty corruption will leave us in unrecoverable state.
464 	 */
465 
466 	offset = block << v->data_dev_block_bits;
467 	res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
468 
469 	/*
470 	 * The base RS block we can feed to the interleaver to find out all
471 	 * blocks required for decoding.
472 	 */
473 	rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
474 
475 	/*
476 	 * Locating erasures is slow, so attempt to recover the block without
477 	 * them first. Do a second attempt with erasures if the corruption is
478 	 * bad enough.
479 	 */
480 	r = fec_decode_rsb(v, io, fio, rsb, offset, false);
481 	if (r < 0) {
482 		r = fec_decode_rsb(v, io, fio, rsb, offset, true);
483 		if (r < 0)
484 			goto done;
485 	}
486 
487 	if (dest)
488 		memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
489 	else if (iter) {
490 		fio->output_pos = 0;
491 		r = verity_for_bv_block(v, io, iter, fec_bv_copy);
492 	}
493 
494 done:
495 	fio->level--;
496 	return r;
497 }
498 
499 /*
500  * Clean up per-bio data.
501  */
verity_fec_finish_io(struct dm_verity_io * io)502 void verity_fec_finish_io(struct dm_verity_io *io)
503 {
504 	unsigned int n;
505 	struct dm_verity_fec *f = io->v->fec;
506 	struct dm_verity_fec_io *fio = fec_io(io);
507 
508 	if (!verity_fec_is_enabled(io->v))
509 		return;
510 
511 	mempool_free(fio->rs, &f->rs_pool);
512 
513 	fec_for_each_prealloc_buffer(n)
514 		mempool_free(fio->bufs[n], &f->prealloc_pool);
515 
516 	fec_for_each_extra_buffer(fio, n)
517 		mempool_free(fio->bufs[n], &f->extra_pool);
518 
519 	mempool_free(fio->output, &f->output_pool);
520 }
521 
522 /*
523  * Initialize per-bio data.
524  */
verity_fec_init_io(struct dm_verity_io * io)525 void verity_fec_init_io(struct dm_verity_io *io)
526 {
527 	struct dm_verity_fec_io *fio = fec_io(io);
528 
529 	if (!verity_fec_is_enabled(io->v))
530 		return;
531 
532 	fio->rs = NULL;
533 	memset(fio->bufs, 0, sizeof(fio->bufs));
534 	fio->nbufs = 0;
535 	fio->output = NULL;
536 	fio->level = 0;
537 }
538 
539 /*
540  * Append feature arguments and values to the status table.
541  */
verity_fec_status_table(struct dm_verity * v,unsigned int sz,char * result,unsigned int maxlen)542 unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz,
543 				 char *result, unsigned int maxlen)
544 {
545 	if (!verity_fec_is_enabled(v))
546 		return sz;
547 
548 	DMEMIT(" " DM_VERITY_OPT_FEC_DEV " %s "
549 	       DM_VERITY_OPT_FEC_BLOCKS " %llu "
550 	       DM_VERITY_OPT_FEC_START " %llu "
551 	       DM_VERITY_OPT_FEC_ROOTS " %d",
552 	       v->fec->dev->name,
553 	       (unsigned long long)v->fec->blocks,
554 	       (unsigned long long)v->fec->start,
555 	       v->fec->roots);
556 
557 	return sz;
558 }
559 
verity_fec_dtr(struct dm_verity * v)560 void verity_fec_dtr(struct dm_verity *v)
561 {
562 	struct dm_verity_fec *f = v->fec;
563 
564 	if (!verity_fec_is_enabled(v))
565 		goto out;
566 
567 	mempool_exit(&f->rs_pool);
568 	mempool_exit(&f->prealloc_pool);
569 	mempool_exit(&f->extra_pool);
570 	mempool_exit(&f->output_pool);
571 	kmem_cache_destroy(f->cache);
572 
573 	if (f->data_bufio)
574 		dm_bufio_client_destroy(f->data_bufio);
575 	if (f->bufio)
576 		dm_bufio_client_destroy(f->bufio);
577 
578 	if (f->dev)
579 		dm_put_device(v->ti, f->dev);
580 out:
581 	kfree(f);
582 	v->fec = NULL;
583 }
584 
fec_rs_alloc(gfp_t gfp_mask,void * pool_data)585 static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
586 {
587 	struct dm_verity *v = pool_data;
588 
589 	return init_rs_gfp(8, 0x11d, 0, 1, v->fec->roots, gfp_mask);
590 }
591 
fec_rs_free(void * element,void * pool_data)592 static void fec_rs_free(void *element, void *pool_data)
593 {
594 	struct rs_control *rs = element;
595 
596 	if (rs)
597 		free_rs(rs);
598 }
599 
verity_is_fec_opt_arg(const char * arg_name)600 bool verity_is_fec_opt_arg(const char *arg_name)
601 {
602 	return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
603 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
604 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
605 		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
606 }
607 
verity_fec_parse_opt_args(struct dm_arg_set * as,struct dm_verity * v,unsigned int * argc,const char * arg_name)608 int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
609 			      unsigned int *argc, const char *arg_name)
610 {
611 	int r;
612 	struct dm_target *ti = v->ti;
613 	const char *arg_value;
614 	unsigned long long num_ll;
615 	unsigned char num_c;
616 	char dummy;
617 
618 	if (!*argc) {
619 		ti->error = "FEC feature arguments require a value";
620 		return -EINVAL;
621 	}
622 
623 	arg_value = dm_shift_arg(as);
624 	(*argc)--;
625 
626 	if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
627 		r = dm_get_device(ti, arg_value, BLK_OPEN_READ, &v->fec->dev);
628 		if (r) {
629 			ti->error = "FEC device lookup failed";
630 			return r;
631 		}
632 
633 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
634 		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
635 		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
636 		     >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
637 			ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
638 			return -EINVAL;
639 		}
640 		v->fec->blocks = num_ll;
641 
642 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
643 		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
644 		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
645 		     (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
646 			ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
647 			return -EINVAL;
648 		}
649 		v->fec->start = num_ll;
650 
651 	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
652 		if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
653 		    num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
654 		    num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
655 			ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
656 			return -EINVAL;
657 		}
658 		v->fec->roots = num_c;
659 
660 	} else {
661 		ti->error = "Unrecognized verity FEC feature request";
662 		return -EINVAL;
663 	}
664 
665 	return 0;
666 }
667 
668 /*
669  * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
670  */
verity_fec_ctr_alloc(struct dm_verity * v)671 int verity_fec_ctr_alloc(struct dm_verity *v)
672 {
673 	struct dm_verity_fec *f;
674 
675 	f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
676 	if (!f) {
677 		v->ti->error = "Cannot allocate FEC structure";
678 		return -ENOMEM;
679 	}
680 	v->fec = f;
681 
682 	return 0;
683 }
684 
685 /*
686  * Validate arguments and preallocate memory. Must be called after arguments
687  * have been parsed using verity_fec_parse_opt_args.
688  */
verity_fec_ctr(struct dm_verity * v)689 int verity_fec_ctr(struct dm_verity *v)
690 {
691 	struct dm_verity_fec *f = v->fec;
692 	struct dm_target *ti = v->ti;
693 	u64 hash_blocks, fec_blocks;
694 	int ret;
695 
696 	if (!verity_fec_is_enabled(v)) {
697 		verity_fec_dtr(v);
698 		return 0;
699 	}
700 
701 	/*
702 	 * FEC is computed over data blocks, possible metadata, and
703 	 * hash blocks. In other words, FEC covers total of fec_blocks
704 	 * blocks consisting of the following:
705 	 *
706 	 *  data blocks | hash blocks | metadata (optional)
707 	 *
708 	 * We allow metadata after hash blocks to support a use case
709 	 * where all data is stored on the same device and FEC covers
710 	 * the entire area.
711 	 *
712 	 * If metadata is included, we require it to be available on the
713 	 * hash device after the hash blocks.
714 	 */
715 
716 	hash_blocks = v->hash_blocks - v->hash_start;
717 
718 	/*
719 	 * Require matching block sizes for data and hash devices for
720 	 * simplicity.
721 	 */
722 	if (v->data_dev_block_bits != v->hash_dev_block_bits) {
723 		ti->error = "Block sizes must match to use FEC";
724 		return -EINVAL;
725 	}
726 
727 	if (!f->roots) {
728 		ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
729 		return -EINVAL;
730 	}
731 	f->rsn = DM_VERITY_FEC_RSM - f->roots;
732 
733 	if (!f->blocks) {
734 		ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
735 		return -EINVAL;
736 	}
737 
738 	f->rounds = f->blocks;
739 	if (sector_div(f->rounds, f->rsn))
740 		f->rounds++;
741 
742 	/*
743 	 * Due to optional metadata, f->blocks can be larger than
744 	 * data_blocks and hash_blocks combined.
745 	 */
746 	if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
747 		ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
748 		return -EINVAL;
749 	}
750 
751 	/*
752 	 * Metadata is accessed through the hash device, so we require
753 	 * it to be large enough.
754 	 */
755 	f->hash_blocks = f->blocks - v->data_blocks;
756 	if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
757 		ti->error = "Hash device is too small for "
758 			DM_VERITY_OPT_FEC_BLOCKS;
759 		return -E2BIG;
760 	}
761 
762 	f->io_size = 1 << v->data_dev_block_bits;
763 
764 	f->bufio = dm_bufio_client_create(f->dev->bdev,
765 					  f->io_size,
766 					  1, 0, NULL, NULL, 0);
767 	if (IS_ERR(f->bufio)) {
768 		ti->error = "Cannot initialize FEC bufio client";
769 		return PTR_ERR(f->bufio);
770 	}
771 
772 	dm_bufio_set_sector_offset(f->bufio, f->start << (v->data_dev_block_bits - SECTOR_SHIFT));
773 
774 	fec_blocks = div64_u64(f->rounds * f->roots, v->fec->roots << SECTOR_SHIFT);
775 	if (dm_bufio_get_device_size(f->bufio) < fec_blocks) {
776 		ti->error = "FEC device is too small";
777 		return -E2BIG;
778 	}
779 
780 	f->data_bufio = dm_bufio_client_create(v->data_dev->bdev,
781 					       1 << v->data_dev_block_bits,
782 					       1, 0, NULL, NULL, 0);
783 	if (IS_ERR(f->data_bufio)) {
784 		ti->error = "Cannot initialize FEC data bufio client";
785 		return PTR_ERR(f->data_bufio);
786 	}
787 
788 	if (dm_bufio_get_device_size(f->data_bufio) < v->data_blocks) {
789 		ti->error = "Data device is too small";
790 		return -E2BIG;
791 	}
792 
793 	/* Preallocate an rs_control structure for each worker thread */
794 	ret = mempool_init(&f->rs_pool, num_online_cpus(), fec_rs_alloc,
795 			   fec_rs_free, (void *) v);
796 	if (ret) {
797 		ti->error = "Cannot allocate RS pool";
798 		return ret;
799 	}
800 
801 	f->cache = kmem_cache_create("dm_verity_fec_buffers",
802 				     f->rsn << DM_VERITY_FEC_BUF_RS_BITS,
803 				     0, 0, NULL);
804 	if (!f->cache) {
805 		ti->error = "Cannot create FEC buffer cache";
806 		return -ENOMEM;
807 	}
808 
809 	/* Preallocate DM_VERITY_FEC_BUF_PREALLOC buffers for each thread */
810 	ret = mempool_init_slab_pool(&f->prealloc_pool, num_online_cpus() *
811 				     DM_VERITY_FEC_BUF_PREALLOC,
812 				     f->cache);
813 	if (ret) {
814 		ti->error = "Cannot allocate FEC buffer prealloc pool";
815 		return ret;
816 	}
817 
818 	ret = mempool_init_slab_pool(&f->extra_pool, 0, f->cache);
819 	if (ret) {
820 		ti->error = "Cannot allocate FEC buffer extra pool";
821 		return ret;
822 	}
823 
824 	/* Preallocate an output buffer for each thread */
825 	ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
826 					1 << v->data_dev_block_bits);
827 	if (ret) {
828 		ti->error = "Cannot allocate FEC output pool";
829 		return ret;
830 	}
831 
832 	/* Reserve space for our per-bio data */
833 	ti->per_io_data_size += sizeof(struct dm_verity_fec_io);
834 
835 	return 0;
836 }
837