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1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/export.h>
3#include <linux/bvec.h>
4#include <linux/fault-inject-usercopy.h>
5#include <linux/uio.h>
6#include <linux/pagemap.h>
7#include <linux/highmem.h>
8#include <linux/slab.h>
9#include <linux/vmalloc.h>
10#include <linux/splice.h>
11#include <linux/compat.h>
12#include <linux/scatterlist.h>
13#include <linux/instrumented.h>
14#include <linux/iov_iter.h>
15
16static __always_inline
17size_t copy_to_user_iter(void __user *iter_to, size_t progress,
18 size_t len, void *from, void *priv2)
19{
20 if (should_fail_usercopy())
21 return len;
22 if (access_ok(iter_to, len)) {
23 from += progress;
24 instrument_copy_to_user(iter_to, from, len);
25 len = raw_copy_to_user(iter_to, from, len);
26 }
27 return len;
28}
29
30static __always_inline
31size_t copy_to_user_iter_nofault(void __user *iter_to, size_t progress,
32 size_t len, void *from, void *priv2)
33{
34 ssize_t res;
35
36 if (should_fail_usercopy())
37 return len;
38
39 from += progress;
40 res = copy_to_user_nofault(iter_to, from, len);
41 return res < 0 ? len : res;
42}
43
44static __always_inline
45size_t copy_from_user_iter(void __user *iter_from, size_t progress,
46 size_t len, void *to, void *priv2)
47{
48 size_t res = len;
49
50 if (should_fail_usercopy())
51 return len;
52 if (access_ok(iter_from, len)) {
53 to += progress;
54 instrument_copy_from_user_before(to, iter_from, len);
55 res = raw_copy_from_user(to, iter_from, len);
56 instrument_copy_from_user_after(to, iter_from, len, res);
57 }
58 return res;
59}
60
61static __always_inline
62size_t memcpy_to_iter(void *iter_to, size_t progress,
63 size_t len, void *from, void *priv2)
64{
65 memcpy(iter_to, from + progress, len);
66 return 0;
67}
68
69static __always_inline
70size_t memcpy_from_iter(void *iter_from, size_t progress,
71 size_t len, void *to, void *priv2)
72{
73 memcpy(to + progress, iter_from, len);
74 return 0;
75}
76
77/*
78 * fault_in_iov_iter_readable - fault in iov iterator for reading
79 * @i: iterator
80 * @size: maximum length
81 *
82 * Fault in one or more iovecs of the given iov_iter, to a maximum length of
83 * @size. For each iovec, fault in each page that constitutes the iovec.
84 *
85 * Returns the number of bytes not faulted in (like copy_to_user() and
86 * copy_from_user()).
87 *
88 * Always returns 0 for non-userspace iterators.
89 */
90size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
91{
92 if (iter_is_ubuf(i)) {
93 size_t n = min(size, iov_iter_count(i));
94 n -= fault_in_readable(i->ubuf + i->iov_offset, n);
95 return size - n;
96 } else if (iter_is_iovec(i)) {
97 size_t count = min(size, iov_iter_count(i));
98 const struct iovec *p;
99 size_t skip;
100
101 size -= count;
102 for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
103 size_t len = min(count, p->iov_len - skip);
104 size_t ret;
105
106 if (unlikely(!len))
107 continue;
108 ret = fault_in_readable(p->iov_base + skip, len);
109 count -= len - ret;
110 if (ret)
111 break;
112 }
113 return count + size;
114 }
115 return 0;
116}
117EXPORT_SYMBOL(fault_in_iov_iter_readable);
118
119/*
120 * fault_in_iov_iter_writeable - fault in iov iterator for writing
121 * @i: iterator
122 * @size: maximum length
123 *
124 * Faults in the iterator using get_user_pages(), i.e., without triggering
125 * hardware page faults. This is primarily useful when we already know that
126 * some or all of the pages in @i aren't in memory.
127 *
128 * Returns the number of bytes not faulted in, like copy_to_user() and
129 * copy_from_user().
130 *
131 * Always returns 0 for non-user-space iterators.
132 */
133size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
134{
135 if (iter_is_ubuf(i)) {
136 size_t n = min(size, iov_iter_count(i));
137 n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n);
138 return size - n;
139 } else if (iter_is_iovec(i)) {
140 size_t count = min(size, iov_iter_count(i));
141 const struct iovec *p;
142 size_t skip;
143
144 size -= count;
145 for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
146 size_t len = min(count, p->iov_len - skip);
147 size_t ret;
148
149 if (unlikely(!len))
150 continue;
151 ret = fault_in_safe_writeable(p->iov_base + skip, len);
152 count -= len - ret;
153 if (ret)
154 break;
155 }
156 return count + size;
157 }
158 return 0;
159}
160EXPORT_SYMBOL(fault_in_iov_iter_writeable);
161
162void iov_iter_init(struct iov_iter *i, unsigned int direction,
163 const struct iovec *iov, unsigned long nr_segs,
164 size_t count)
165{
166 WARN_ON(direction & ~(READ | WRITE));
167 *i = (struct iov_iter) {
168 .iter_type = ITER_IOVEC,
169 .nofault = false,
170 .data_source = direction,
171 .__iov = iov,
172 .nr_segs = nr_segs,
173 .iov_offset = 0,
174 .count = count
175 };
176}
177EXPORT_SYMBOL(iov_iter_init);
178
179size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
180{
181 if (WARN_ON_ONCE(i->data_source))
182 return 0;
183 if (user_backed_iter(i))
184 might_fault();
185 return iterate_and_advance(i, bytes, (void *)addr,
186 copy_to_user_iter, memcpy_to_iter);
187}
188EXPORT_SYMBOL(_copy_to_iter);
189
190#ifdef CONFIG_ARCH_HAS_COPY_MC
191static __always_inline
192size_t copy_to_user_iter_mc(void __user *iter_to, size_t progress,
193 size_t len, void *from, void *priv2)
194{
195 if (access_ok(iter_to, len)) {
196 from += progress;
197 instrument_copy_to_user(iter_to, from, len);
198 len = copy_mc_to_user(iter_to, from, len);
199 }
200 return len;
201}
202
203static __always_inline
204size_t memcpy_to_iter_mc(void *iter_to, size_t progress,
205 size_t len, void *from, void *priv2)
206{
207 return copy_mc_to_kernel(iter_to, from + progress, len);
208}
209
210/**
211 * _copy_mc_to_iter - copy to iter with source memory error exception handling
212 * @addr: source kernel address
213 * @bytes: total transfer length
214 * @i: destination iterator
215 *
216 * The pmem driver deploys this for the dax operation
217 * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
218 * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
219 * successfully copied.
220 *
221 * The main differences between this and typical _copy_to_iter().
222 *
223 * * Typical tail/residue handling after a fault retries the copy
224 * byte-by-byte until the fault happens again. Re-triggering machine
225 * checks is potentially fatal so the implementation uses source
226 * alignment and poison alignment assumptions to avoid re-triggering
227 * hardware exceptions.
228 *
229 * * ITER_KVEC and ITER_BVEC can return short copies. Compare to
230 * copy_to_iter() where only ITER_IOVEC attempts might return a short copy.
231 *
232 * Return: number of bytes copied (may be %0)
233 */
234size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
235{
236 if (WARN_ON_ONCE(i->data_source))
237 return 0;
238 if (user_backed_iter(i))
239 might_fault();
240 return iterate_and_advance(i, bytes, (void *)addr,
241 copy_to_user_iter_mc, memcpy_to_iter_mc);
242}
243EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
244#endif /* CONFIG_ARCH_HAS_COPY_MC */
245
246static __always_inline
247size_t __copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
248{
249 return iterate_and_advance(i, bytes, addr,
250 copy_from_user_iter, memcpy_from_iter);
251}
252
253size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
254{
255 if (WARN_ON_ONCE(!i->data_source))
256 return 0;
257
258 if (user_backed_iter(i))
259 might_fault();
260 return __copy_from_iter(addr, bytes, i);
261}
262EXPORT_SYMBOL(_copy_from_iter);
263
264static __always_inline
265size_t copy_from_user_iter_nocache(void __user *iter_from, size_t progress,
266 size_t len, void *to, void *priv2)
267{
268 return __copy_from_user_inatomic_nocache(to + progress, iter_from, len);
269}
270
271size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
272{
273 if (WARN_ON_ONCE(!i->data_source))
274 return 0;
275
276 return iterate_and_advance(i, bytes, addr,
277 copy_from_user_iter_nocache,
278 memcpy_from_iter);
279}
280EXPORT_SYMBOL(_copy_from_iter_nocache);
281
282#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
283static __always_inline
284size_t copy_from_user_iter_flushcache(void __user *iter_from, size_t progress,
285 size_t len, void *to, void *priv2)
286{
287 return __copy_from_user_flushcache(to + progress, iter_from, len);
288}
289
290static __always_inline
291size_t memcpy_from_iter_flushcache(void *iter_from, size_t progress,
292 size_t len, void *to, void *priv2)
293{
294 memcpy_flushcache(to + progress, iter_from, len);
295 return 0;
296}
297
298/**
299 * _copy_from_iter_flushcache - write destination through cpu cache
300 * @addr: destination kernel address
301 * @bytes: total transfer length
302 * @i: source iterator
303 *
304 * The pmem driver arranges for filesystem-dax to use this facility via
305 * dax_copy_from_iter() for ensuring that writes to persistent memory
306 * are flushed through the CPU cache. It is differentiated from
307 * _copy_from_iter_nocache() in that guarantees all data is flushed for
308 * all iterator types. The _copy_from_iter_nocache() only attempts to
309 * bypass the cache for the ITER_IOVEC case, and on some archs may use
310 * instructions that strand dirty-data in the cache.
311 *
312 * Return: number of bytes copied (may be %0)
313 */
314size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
315{
316 if (WARN_ON_ONCE(!i->data_source))
317 return 0;
318
319 return iterate_and_advance(i, bytes, addr,
320 copy_from_user_iter_flushcache,
321 memcpy_from_iter_flushcache);
322}
323EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
324#endif
325
326static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
327{
328 struct page *head;
329 size_t v = n + offset;
330
331 /*
332 * The general case needs to access the page order in order
333 * to compute the page size.
334 * However, we mostly deal with order-0 pages and thus can
335 * avoid a possible cache line miss for requests that fit all
336 * page orders.
337 */
338 if (n <= v && v <= PAGE_SIZE)
339 return true;
340
341 head = compound_head(page);
342 v += (page - head) << PAGE_SHIFT;
343
344 if (WARN_ON(n > v || v > page_size(head)))
345 return false;
346 return true;
347}
348
349size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
350 struct iov_iter *i)
351{
352 size_t res = 0;
353 if (!page_copy_sane(page, offset, bytes))
354 return 0;
355 if (WARN_ON_ONCE(i->data_source))
356 return 0;
357 page += offset / PAGE_SIZE; // first subpage
358 offset %= PAGE_SIZE;
359 while (1) {
360 void *kaddr = kmap_local_page(page);
361 size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
362 n = _copy_to_iter(kaddr + offset, n, i);
363 kunmap_local(kaddr);
364 res += n;
365 bytes -= n;
366 if (!bytes || !n)
367 break;
368 offset += n;
369 if (offset == PAGE_SIZE) {
370 page++;
371 offset = 0;
372 }
373 }
374 return res;
375}
376EXPORT_SYMBOL(copy_page_to_iter);
377
378size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes,
379 struct iov_iter *i)
380{
381 size_t res = 0;
382
383 if (!page_copy_sane(page, offset, bytes))
384 return 0;
385 if (WARN_ON_ONCE(i->data_source))
386 return 0;
387 page += offset / PAGE_SIZE; // first subpage
388 offset %= PAGE_SIZE;
389 while (1) {
390 void *kaddr = kmap_local_page(page);
391 size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
392
393 n = iterate_and_advance(i, n, kaddr + offset,
394 copy_to_user_iter_nofault,
395 memcpy_to_iter);
396 kunmap_local(kaddr);
397 res += n;
398 bytes -= n;
399 if (!bytes || !n)
400 break;
401 offset += n;
402 if (offset == PAGE_SIZE) {
403 page++;
404 offset = 0;
405 }
406 }
407 return res;
408}
409EXPORT_SYMBOL(copy_page_to_iter_nofault);
410
411size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
412 struct iov_iter *i)
413{
414 size_t res = 0;
415 if (!page_copy_sane(page, offset, bytes))
416 return 0;
417 page += offset / PAGE_SIZE; // first subpage
418 offset %= PAGE_SIZE;
419 while (1) {
420 void *kaddr = kmap_local_page(page);
421 size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
422 n = _copy_from_iter(kaddr + offset, n, i);
423 kunmap_local(kaddr);
424 res += n;
425 bytes -= n;
426 if (!bytes || !n)
427 break;
428 offset += n;
429 if (offset == PAGE_SIZE) {
430 page++;
431 offset = 0;
432 }
433 }
434 return res;
435}
436EXPORT_SYMBOL(copy_page_from_iter);
437
438static __always_inline
439size_t zero_to_user_iter(void __user *iter_to, size_t progress,
440 size_t len, void *priv, void *priv2)
441{
442 return clear_user(iter_to, len);
443}
444
445static __always_inline
446size_t zero_to_iter(void *iter_to, size_t progress,
447 size_t len, void *priv, void *priv2)
448{
449 memset(iter_to, 0, len);
450 return 0;
451}
452
453size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
454{
455 return iterate_and_advance(i, bytes, NULL,
456 zero_to_user_iter, zero_to_iter);
457}
458EXPORT_SYMBOL(iov_iter_zero);
459
460size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
461 size_t bytes, struct iov_iter *i)
462{
463 size_t n, copied = 0;
464
465 if (!page_copy_sane(page, offset, bytes))
466 return 0;
467 if (WARN_ON_ONCE(!i->data_source))
468 return 0;
469
470 do {
471 char *p;
472
473 n = bytes - copied;
474 if (PageHighMem(page)) {
475 page += offset / PAGE_SIZE;
476 offset %= PAGE_SIZE;
477 n = min_t(size_t, n, PAGE_SIZE - offset);
478 }
479
480 p = kmap_atomic(page) + offset;
481 n = __copy_from_iter(p, n, i);
482 kunmap_atomic(p);
483 copied += n;
484 offset += n;
485 } while (PageHighMem(page) && copied != bytes && n > 0);
486
487 return copied;
488}
489EXPORT_SYMBOL(copy_page_from_iter_atomic);
490
491static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
492{
493 const struct bio_vec *bvec, *end;
494
495 if (!i->count)
496 return;
497 i->count -= size;
498
499 size += i->iov_offset;
500
501 for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
502 if (likely(size < bvec->bv_len))
503 break;
504 size -= bvec->bv_len;
505 }
506 i->iov_offset = size;
507 i->nr_segs -= bvec - i->bvec;
508 i->bvec = bvec;
509}
510
511static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
512{
513 const struct iovec *iov, *end;
514
515 if (!i->count)
516 return;
517 i->count -= size;
518
519 size += i->iov_offset; // from beginning of current segment
520 for (iov = iter_iov(i), end = iov + i->nr_segs; iov < end; iov++) {
521 if (likely(size < iov->iov_len))
522 break;
523 size -= iov->iov_len;
524 }
525 i->iov_offset = size;
526 i->nr_segs -= iov - iter_iov(i);
527 i->__iov = iov;
528}
529
530void iov_iter_advance(struct iov_iter *i, size_t size)
531{
532 if (unlikely(i->count < size))
533 size = i->count;
534 if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
535 i->iov_offset += size;
536 i->count -= size;
537 } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
538 /* iovec and kvec have identical layouts */
539 iov_iter_iovec_advance(i, size);
540 } else if (iov_iter_is_bvec(i)) {
541 iov_iter_bvec_advance(i, size);
542 } else if (iov_iter_is_discard(i)) {
543 i->count -= size;
544 }
545}
546EXPORT_SYMBOL(iov_iter_advance);
547
548void iov_iter_revert(struct iov_iter *i, size_t unroll)
549{
550 if (!unroll)
551 return;
552 if (WARN_ON(unroll > MAX_RW_COUNT))
553 return;
554 i->count += unroll;
555 if (unlikely(iov_iter_is_discard(i)))
556 return;
557 if (unroll <= i->iov_offset) {
558 i->iov_offset -= unroll;
559 return;
560 }
561 unroll -= i->iov_offset;
562 if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
563 BUG(); /* We should never go beyond the start of the specified
564 * range since we might then be straying into pages that
565 * aren't pinned.
566 */
567 } else if (iov_iter_is_bvec(i)) {
568 const struct bio_vec *bvec = i->bvec;
569 while (1) {
570 size_t n = (--bvec)->bv_len;
571 i->nr_segs++;
572 if (unroll <= n) {
573 i->bvec = bvec;
574 i->iov_offset = n - unroll;
575 return;
576 }
577 unroll -= n;
578 }
579 } else { /* same logics for iovec and kvec */
580 const struct iovec *iov = iter_iov(i);
581 while (1) {
582 size_t n = (--iov)->iov_len;
583 i->nr_segs++;
584 if (unroll <= n) {
585 i->__iov = iov;
586 i->iov_offset = n - unroll;
587 return;
588 }
589 unroll -= n;
590 }
591 }
592}
593EXPORT_SYMBOL(iov_iter_revert);
594
595/*
596 * Return the count of just the current iov_iter segment.
597 */
598size_t iov_iter_single_seg_count(const struct iov_iter *i)
599{
600 if (i->nr_segs > 1) {
601 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
602 return min(i->count, iter_iov(i)->iov_len - i->iov_offset);
603 if (iov_iter_is_bvec(i))
604 return min(i->count, i->bvec->bv_len - i->iov_offset);
605 }
606 return i->count;
607}
608EXPORT_SYMBOL(iov_iter_single_seg_count);
609
610void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
611 const struct kvec *kvec, unsigned long nr_segs,
612 size_t count)
613{
614 WARN_ON(direction & ~(READ | WRITE));
615 *i = (struct iov_iter){
616 .iter_type = ITER_KVEC,
617 .data_source = direction,
618 .kvec = kvec,
619 .nr_segs = nr_segs,
620 .iov_offset = 0,
621 .count = count
622 };
623}
624EXPORT_SYMBOL(iov_iter_kvec);
625
626void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
627 const struct bio_vec *bvec, unsigned long nr_segs,
628 size_t count)
629{
630 WARN_ON(direction & ~(READ | WRITE));
631 *i = (struct iov_iter){
632 .iter_type = ITER_BVEC,
633 .data_source = direction,
634 .bvec = bvec,
635 .nr_segs = nr_segs,
636 .iov_offset = 0,
637 .count = count
638 };
639}
640EXPORT_SYMBOL(iov_iter_bvec);
641
642/**
643 * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
644 * @i: The iterator to initialise.
645 * @direction: The direction of the transfer.
646 * @xarray: The xarray to access.
647 * @start: The start file position.
648 * @count: The size of the I/O buffer in bytes.
649 *
650 * Set up an I/O iterator to either draw data out of the pages attached to an
651 * inode or to inject data into those pages. The pages *must* be prevented
652 * from evaporation, either by taking a ref on them or locking them by the
653 * caller.
654 */
655void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
656 struct xarray *xarray, loff_t start, size_t count)
657{
658 BUG_ON(direction & ~1);
659 *i = (struct iov_iter) {
660 .iter_type = ITER_XARRAY,
661 .data_source = direction,
662 .xarray = xarray,
663 .xarray_start = start,
664 .count = count,
665 .iov_offset = 0
666 };
667}
668EXPORT_SYMBOL(iov_iter_xarray);
669
670/**
671 * iov_iter_discard - Initialise an I/O iterator that discards data
672 * @i: The iterator to initialise.
673 * @direction: The direction of the transfer.
674 * @count: The size of the I/O buffer in bytes.
675 *
676 * Set up an I/O iterator that just discards everything that's written to it.
677 * It's only available as a READ iterator.
678 */
679void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
680{
681 BUG_ON(direction != READ);
682 *i = (struct iov_iter){
683 .iter_type = ITER_DISCARD,
684 .data_source = false,
685 .count = count,
686 .iov_offset = 0
687 };
688}
689EXPORT_SYMBOL(iov_iter_discard);
690
691static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,
692 unsigned len_mask)
693{
694 size_t size = i->count;
695 size_t skip = i->iov_offset;
696 unsigned k;
697
698 for (k = 0; k < i->nr_segs; k++, skip = 0) {
699 const struct iovec *iov = iter_iov(i) + k;
700 size_t len = iov->iov_len - skip;
701
702 if (len > size)
703 len = size;
704 if (len & len_mask)
705 return false;
706 if ((unsigned long)(iov->iov_base + skip) & addr_mask)
707 return false;
708
709 size -= len;
710 if (!size)
711 break;
712 }
713 return true;
714}
715
716static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
717 unsigned len_mask)
718{
719 size_t size = i->count;
720 unsigned skip = i->iov_offset;
721 unsigned k;
722
723 for (k = 0; k < i->nr_segs; k++, skip = 0) {
724 size_t len = i->bvec[k].bv_len - skip;
725
726 if (len > size)
727 len = size;
728 if (len & len_mask)
729 return false;
730 if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask)
731 return false;
732
733 size -= len;
734 if (!size)
735 break;
736 }
737 return true;
738}
739
740/**
741 * iov_iter_is_aligned() - Check if the addresses and lengths of each segments
742 * are aligned to the parameters.
743 *
744 * @i: &struct iov_iter to restore
745 * @addr_mask: bit mask to check against the iov element's addresses
746 * @len_mask: bit mask to check against the iov element's lengths
747 *
748 * Return: false if any addresses or lengths intersect with the provided masks
749 */
750bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
751 unsigned len_mask)
752{
753 if (likely(iter_is_ubuf(i))) {
754 if (i->count & len_mask)
755 return false;
756 if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask)
757 return false;
758 return true;
759 }
760
761 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
762 return iov_iter_aligned_iovec(i, addr_mask, len_mask);
763
764 if (iov_iter_is_bvec(i))
765 return iov_iter_aligned_bvec(i, addr_mask, len_mask);
766
767 if (iov_iter_is_xarray(i)) {
768 if (i->count & len_mask)
769 return false;
770 if ((i->xarray_start + i->iov_offset) & addr_mask)
771 return false;
772 }
773
774 return true;
775}
776EXPORT_SYMBOL_GPL(iov_iter_is_aligned);
777
778static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
779{
780 unsigned long res = 0;
781 size_t size = i->count;
782 size_t skip = i->iov_offset;
783 unsigned k;
784
785 for (k = 0; k < i->nr_segs; k++, skip = 0) {
786 const struct iovec *iov = iter_iov(i) + k;
787 size_t len = iov->iov_len - skip;
788 if (len) {
789 res |= (unsigned long)iov->iov_base + skip;
790 if (len > size)
791 len = size;
792 res |= len;
793 size -= len;
794 if (!size)
795 break;
796 }
797 }
798 return res;
799}
800
801static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
802{
803 unsigned res = 0;
804 size_t size = i->count;
805 unsigned skip = i->iov_offset;
806 unsigned k;
807
808 for (k = 0; k < i->nr_segs; k++, skip = 0) {
809 size_t len = i->bvec[k].bv_len - skip;
810 res |= (unsigned long)i->bvec[k].bv_offset + skip;
811 if (len > size)
812 len = size;
813 res |= len;
814 size -= len;
815 if (!size)
816 break;
817 }
818 return res;
819}
820
821unsigned long iov_iter_alignment(const struct iov_iter *i)
822{
823 if (likely(iter_is_ubuf(i))) {
824 size_t size = i->count;
825 if (size)
826 return ((unsigned long)i->ubuf + i->iov_offset) | size;
827 return 0;
828 }
829
830 /* iovec and kvec have identical layouts */
831 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
832 return iov_iter_alignment_iovec(i);
833
834 if (iov_iter_is_bvec(i))
835 return iov_iter_alignment_bvec(i);
836
837 if (iov_iter_is_xarray(i))
838 return (i->xarray_start + i->iov_offset) | i->count;
839
840 return 0;
841}
842EXPORT_SYMBOL(iov_iter_alignment);
843
844unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
845{
846 unsigned long res = 0;
847 unsigned long v = 0;
848 size_t size = i->count;
849 unsigned k;
850
851 if (iter_is_ubuf(i))
852 return 0;
853
854 if (WARN_ON(!iter_is_iovec(i)))
855 return ~0U;
856
857 for (k = 0; k < i->nr_segs; k++) {
858 const struct iovec *iov = iter_iov(i) + k;
859 if (iov->iov_len) {
860 unsigned long base = (unsigned long)iov->iov_base;
861 if (v) // if not the first one
862 res |= base | v; // this start | previous end
863 v = base + iov->iov_len;
864 if (size <= iov->iov_len)
865 break;
866 size -= iov->iov_len;
867 }
868 }
869 return res;
870}
871EXPORT_SYMBOL(iov_iter_gap_alignment);
872
873static int want_pages_array(struct page ***res, size_t size,
874 size_t start, unsigned int maxpages)
875{
876 unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
877
878 if (count > maxpages)
879 count = maxpages;
880 WARN_ON(!count); // caller should've prevented that
881 if (!*res) {
882 *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
883 if (!*res)
884 return 0;
885 }
886 return count;
887}
888
889static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
890 pgoff_t index, unsigned int nr_pages)
891{
892 XA_STATE(xas, xa, index);
893 struct page *page;
894 unsigned int ret = 0;
895
896 rcu_read_lock();
897 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
898 if (xas_retry(&xas, page))
899 continue;
900
901 /* Has the page moved or been split? */
902 if (unlikely(page != xas_reload(&xas))) {
903 xas_reset(&xas);
904 continue;
905 }
906
907 pages[ret] = find_subpage(page, xas.xa_index);
908 get_page(pages[ret]);
909 if (++ret == nr_pages)
910 break;
911 }
912 rcu_read_unlock();
913 return ret;
914}
915
916static ssize_t iter_xarray_get_pages(struct iov_iter *i,
917 struct page ***pages, size_t maxsize,
918 unsigned maxpages, size_t *_start_offset)
919{
920 unsigned nr, offset, count;
921 pgoff_t index;
922 loff_t pos;
923
924 pos = i->xarray_start + i->iov_offset;
925 index = pos >> PAGE_SHIFT;
926 offset = pos & ~PAGE_MASK;
927 *_start_offset = offset;
928
929 count = want_pages_array(pages, maxsize, offset, maxpages);
930 if (!count)
931 return -ENOMEM;
932 nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
933 if (nr == 0)
934 return 0;
935
936 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
937 i->iov_offset += maxsize;
938 i->count -= maxsize;
939 return maxsize;
940}
941
942/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
943static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
944{
945 size_t skip;
946 long k;
947
948 if (iter_is_ubuf(i))
949 return (unsigned long)i->ubuf + i->iov_offset;
950
951 for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
952 const struct iovec *iov = iter_iov(i) + k;
953 size_t len = iov->iov_len - skip;
954
955 if (unlikely(!len))
956 continue;
957 if (*size > len)
958 *size = len;
959 return (unsigned long)iov->iov_base + skip;
960 }
961 BUG(); // if it had been empty, we wouldn't get called
962}
963
964/* must be done on non-empty ITER_BVEC one */
965static struct page *first_bvec_segment(const struct iov_iter *i,
966 size_t *size, size_t *start)
967{
968 struct page *page;
969 size_t skip = i->iov_offset, len;
970
971 len = i->bvec->bv_len - skip;
972 if (*size > len)
973 *size = len;
974 skip += i->bvec->bv_offset;
975 page = i->bvec->bv_page + skip / PAGE_SIZE;
976 *start = skip % PAGE_SIZE;
977 return page;
978}
979
980static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
981 struct page ***pages, size_t maxsize,
982 unsigned int maxpages, size_t *start)
983{
984 unsigned int n, gup_flags = 0;
985
986 if (maxsize > i->count)
987 maxsize = i->count;
988 if (!maxsize)
989 return 0;
990 if (maxsize > MAX_RW_COUNT)
991 maxsize = MAX_RW_COUNT;
992
993 if (likely(user_backed_iter(i))) {
994 unsigned long addr;
995 int res;
996
997 if (iov_iter_rw(i) != WRITE)
998 gup_flags |= FOLL_WRITE;
999 if (i->nofault)
1000 gup_flags |= FOLL_NOFAULT;
1001
1002 addr = first_iovec_segment(i, &maxsize);
1003 *start = addr % PAGE_SIZE;
1004 addr &= PAGE_MASK;
1005 n = want_pages_array(pages, maxsize, *start, maxpages);
1006 if (!n)
1007 return -ENOMEM;
1008 res = get_user_pages_fast(addr, n, gup_flags, *pages);
1009 if (unlikely(res <= 0))
1010 return res;
1011 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
1012 iov_iter_advance(i, maxsize);
1013 return maxsize;
1014 }
1015 if (iov_iter_is_bvec(i)) {
1016 struct page **p;
1017 struct page *page;
1018
1019 page = first_bvec_segment(i, &maxsize, start);
1020 n = want_pages_array(pages, maxsize, *start, maxpages);
1021 if (!n)
1022 return -ENOMEM;
1023 p = *pages;
1024 for (int k = 0; k < n; k++)
1025 get_page(p[k] = page + k);
1026 maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
1027 i->count -= maxsize;
1028 i->iov_offset += maxsize;
1029 if (i->iov_offset == i->bvec->bv_len) {
1030 i->iov_offset = 0;
1031 i->bvec++;
1032 i->nr_segs--;
1033 }
1034 return maxsize;
1035 }
1036 if (iov_iter_is_xarray(i))
1037 return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
1038 return -EFAULT;
1039}
1040
1041ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
1042 size_t maxsize, unsigned maxpages, size_t *start)
1043{
1044 if (!maxpages)
1045 return 0;
1046 BUG_ON(!pages);
1047
1048 return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
1049}
1050EXPORT_SYMBOL(iov_iter_get_pages2);
1051
1052ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
1053 struct page ***pages, size_t maxsize, size_t *start)
1054{
1055 ssize_t len;
1056
1057 *pages = NULL;
1058
1059 len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
1060 if (len <= 0) {
1061 kvfree(*pages);
1062 *pages = NULL;
1063 }
1064 return len;
1065}
1066EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
1067
1068static int iov_npages(const struct iov_iter *i, int maxpages)
1069{
1070 size_t skip = i->iov_offset, size = i->count;
1071 const struct iovec *p;
1072 int npages = 0;
1073
1074 for (p = iter_iov(i); size; skip = 0, p++) {
1075 unsigned offs = offset_in_page(p->iov_base + skip);
1076 size_t len = min(p->iov_len - skip, size);
1077
1078 if (len) {
1079 size -= len;
1080 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1081 if (unlikely(npages > maxpages))
1082 return maxpages;
1083 }
1084 }
1085 return npages;
1086}
1087
1088static int bvec_npages(const struct iov_iter *i, int maxpages)
1089{
1090 size_t skip = i->iov_offset, size = i->count;
1091 const struct bio_vec *p;
1092 int npages = 0;
1093
1094 for (p = i->bvec; size; skip = 0, p++) {
1095 unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
1096 size_t len = min(p->bv_len - skip, size);
1097
1098 size -= len;
1099 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1100 if (unlikely(npages > maxpages))
1101 return maxpages;
1102 }
1103 return npages;
1104}
1105
1106int iov_iter_npages(const struct iov_iter *i, int maxpages)
1107{
1108 if (unlikely(!i->count))
1109 return 0;
1110 if (likely(iter_is_ubuf(i))) {
1111 unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
1112 int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
1113 return min(npages, maxpages);
1114 }
1115 /* iovec and kvec have identical layouts */
1116 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1117 return iov_npages(i, maxpages);
1118 if (iov_iter_is_bvec(i))
1119 return bvec_npages(i, maxpages);
1120 if (iov_iter_is_xarray(i)) {
1121 unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
1122 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1123 return min(npages, maxpages);
1124 }
1125 return 0;
1126}
1127EXPORT_SYMBOL(iov_iter_npages);
1128
1129const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1130{
1131 *new = *old;
1132 if (iov_iter_is_bvec(new))
1133 return new->bvec = kmemdup(new->bvec,
1134 new->nr_segs * sizeof(struct bio_vec),
1135 flags);
1136 else if (iov_iter_is_kvec(new) || iter_is_iovec(new))
1137 /* iovec and kvec have identical layout */
1138 return new->__iov = kmemdup(new->__iov,
1139 new->nr_segs * sizeof(struct iovec),
1140 flags);
1141 return NULL;
1142}
1143EXPORT_SYMBOL(dup_iter);
1144
1145static __noclone int copy_compat_iovec_from_user(struct iovec *iov,
1146 const struct iovec __user *uvec, unsigned long nr_segs)
1147{
1148 const struct compat_iovec __user *uiov =
1149 (const struct compat_iovec __user *)uvec;
1150 int ret = -EFAULT, i;
1151
1152 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1153 return -EFAULT;
1154
1155 for (i = 0; i < nr_segs; i++) {
1156 compat_uptr_t buf;
1157 compat_ssize_t len;
1158
1159 unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
1160 unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
1161
1162 /* check for compat_size_t not fitting in compat_ssize_t .. */
1163 if (len < 0) {
1164 ret = -EINVAL;
1165 goto uaccess_end;
1166 }
1167 iov[i].iov_base = compat_ptr(buf);
1168 iov[i].iov_len = len;
1169 }
1170
1171 ret = 0;
1172uaccess_end:
1173 user_access_end();
1174 return ret;
1175}
1176
1177static __noclone int copy_iovec_from_user(struct iovec *iov,
1178 const struct iovec __user *uiov, unsigned long nr_segs)
1179{
1180 int ret = -EFAULT;
1181
1182 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1183 return -EFAULT;
1184
1185 do {
1186 void __user *buf;
1187 ssize_t len;
1188
1189 unsafe_get_user(len, &uiov->iov_len, uaccess_end);
1190 unsafe_get_user(buf, &uiov->iov_base, uaccess_end);
1191
1192 /* check for size_t not fitting in ssize_t .. */
1193 if (unlikely(len < 0)) {
1194 ret = -EINVAL;
1195 goto uaccess_end;
1196 }
1197 iov->iov_base = buf;
1198 iov->iov_len = len;
1199
1200 uiov++; iov++;
1201 } while (--nr_segs);
1202
1203 ret = 0;
1204uaccess_end:
1205 user_access_end();
1206 return ret;
1207}
1208
1209struct iovec *iovec_from_user(const struct iovec __user *uvec,
1210 unsigned long nr_segs, unsigned long fast_segs,
1211 struct iovec *fast_iov, bool compat)
1212{
1213 struct iovec *iov = fast_iov;
1214 int ret;
1215
1216 /*
1217 * SuS says "The readv() function *may* fail if the iovcnt argument was
1218 * less than or equal to 0, or greater than {IOV_MAX}. Linux has
1219 * traditionally returned zero for zero segments, so...
1220 */
1221 if (nr_segs == 0)
1222 return iov;
1223 if (nr_segs > UIO_MAXIOV)
1224 return ERR_PTR(-EINVAL);
1225 if (nr_segs > fast_segs) {
1226 iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
1227 if (!iov)
1228 return ERR_PTR(-ENOMEM);
1229 }
1230
1231 if (unlikely(compat))
1232 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
1233 else
1234 ret = copy_iovec_from_user(iov, uvec, nr_segs);
1235 if (ret) {
1236 if (iov != fast_iov)
1237 kfree(iov);
1238 return ERR_PTR(ret);
1239 }
1240
1241 return iov;
1242}
1243
1244/*
1245 * Single segment iovec supplied by the user, import it as ITER_UBUF.
1246 */
1247static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
1248 struct iovec **iovp, struct iov_iter *i,
1249 bool compat)
1250{
1251 struct iovec *iov = *iovp;
1252 ssize_t ret;
1253
1254 if (compat)
1255 ret = copy_compat_iovec_from_user(iov, uvec, 1);
1256 else
1257 ret = copy_iovec_from_user(iov, uvec, 1);
1258 if (unlikely(ret))
1259 return ret;
1260
1261 ret = import_ubuf(type, iov->iov_base, iov->iov_len, i);
1262 if (unlikely(ret))
1263 return ret;
1264 *iovp = NULL;
1265 return i->count;
1266}
1267
1268ssize_t __import_iovec(int type, const struct iovec __user *uvec,
1269 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
1270 struct iov_iter *i, bool compat)
1271{
1272 ssize_t total_len = 0;
1273 unsigned long seg;
1274 struct iovec *iov;
1275
1276 if (nr_segs == 1)
1277 return __import_iovec_ubuf(type, uvec, iovp, i, compat);
1278
1279 iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
1280 if (IS_ERR(iov)) {
1281 *iovp = NULL;
1282 return PTR_ERR(iov);
1283 }
1284
1285 /*
1286 * According to the Single Unix Specification we should return EINVAL if
1287 * an element length is < 0 when cast to ssize_t or if the total length
1288 * would overflow the ssize_t return value of the system call.
1289 *
1290 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
1291 * overflow case.
1292 */
1293 for (seg = 0; seg < nr_segs; seg++) {
1294 ssize_t len = (ssize_t)iov[seg].iov_len;
1295
1296 if (!access_ok(iov[seg].iov_base, len)) {
1297 if (iov != *iovp)
1298 kfree(iov);
1299 *iovp = NULL;
1300 return -EFAULT;
1301 }
1302
1303 if (len > MAX_RW_COUNT - total_len) {
1304 len = MAX_RW_COUNT - total_len;
1305 iov[seg].iov_len = len;
1306 }
1307 total_len += len;
1308 }
1309
1310 iov_iter_init(i, type, iov, nr_segs, total_len);
1311 if (iov == *iovp)
1312 *iovp = NULL;
1313 else
1314 *iovp = iov;
1315 return total_len;
1316}
1317
1318/**
1319 * import_iovec() - Copy an array of &struct iovec from userspace
1320 * into the kernel, check that it is valid, and initialize a new
1321 * &struct iov_iter iterator to access it.
1322 *
1323 * @type: One of %READ or %WRITE.
1324 * @uvec: Pointer to the userspace array.
1325 * @nr_segs: Number of elements in userspace array.
1326 * @fast_segs: Number of elements in @iov.
1327 * @iovp: (input and output parameter) Pointer to pointer to (usually small
1328 * on-stack) kernel array.
1329 * @i: Pointer to iterator that will be initialized on success.
1330 *
1331 * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1332 * then this function places %NULL in *@iov on return. Otherwise, a new
1333 * array will be allocated and the result placed in *@iov. This means that
1334 * the caller may call kfree() on *@iov regardless of whether the small
1335 * on-stack array was used or not (and regardless of whether this function
1336 * returns an error or not).
1337 *
1338 * Return: Negative error code on error, bytes imported on success
1339 */
1340ssize_t import_iovec(int type, const struct iovec __user *uvec,
1341 unsigned nr_segs, unsigned fast_segs,
1342 struct iovec **iovp, struct iov_iter *i)
1343{
1344 return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
1345 in_compat_syscall());
1346}
1347EXPORT_SYMBOL(import_iovec);
1348
1349int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
1350{
1351 if (len > MAX_RW_COUNT)
1352 len = MAX_RW_COUNT;
1353 if (unlikely(!access_ok(buf, len)))
1354 return -EFAULT;
1355
1356 iov_iter_ubuf(i, rw, buf, len);
1357 return 0;
1358}
1359EXPORT_SYMBOL_GPL(import_ubuf);
1360
1361/**
1362 * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
1363 * iov_iter_save_state() was called.
1364 *
1365 * @i: &struct iov_iter to restore
1366 * @state: state to restore from
1367 *
1368 * Used after iov_iter_save_state() to bring restore @i, if operations may
1369 * have advanced it.
1370 *
1371 * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
1372 */
1373void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
1374{
1375 if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) &&
1376 !iter_is_ubuf(i)) && !iov_iter_is_kvec(i))
1377 return;
1378 i->iov_offset = state->iov_offset;
1379 i->count = state->count;
1380 if (iter_is_ubuf(i))
1381 return;
1382 /*
1383 * For the *vec iters, nr_segs + iov is constant - if we increment
1384 * the vec, then we also decrement the nr_segs count. Hence we don't
1385 * need to track both of these, just one is enough and we can deduct
1386 * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
1387 * size, so we can just increment the iov pointer as they are unionzed.
1388 * ITER_BVEC _may_ be the same size on some archs, but on others it is
1389 * not. Be safe and handle it separately.
1390 */
1391 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
1392 if (iov_iter_is_bvec(i))
1393 i->bvec -= state->nr_segs - i->nr_segs;
1394 else
1395 i->__iov -= state->nr_segs - i->nr_segs;
1396 i->nr_segs = state->nr_segs;
1397}
1398
1399/*
1400 * Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
1401 * get references on the pages, nor does it get a pin on them.
1402 */
1403static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
1404 struct page ***pages, size_t maxsize,
1405 unsigned int maxpages,
1406 iov_iter_extraction_t extraction_flags,
1407 size_t *offset0)
1408{
1409 struct page *page, **p;
1410 unsigned int nr = 0, offset;
1411 loff_t pos = i->xarray_start + i->iov_offset;
1412 pgoff_t index = pos >> PAGE_SHIFT;
1413 XA_STATE(xas, i->xarray, index);
1414
1415 offset = pos & ~PAGE_MASK;
1416 *offset0 = offset;
1417
1418 maxpages = want_pages_array(pages, maxsize, offset, maxpages);
1419 if (!maxpages)
1420 return -ENOMEM;
1421 p = *pages;
1422
1423 rcu_read_lock();
1424 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
1425 if (xas_retry(&xas, page))
1426 continue;
1427
1428 /* Has the page moved or been split? */
1429 if (unlikely(page != xas_reload(&xas))) {
1430 xas_reset(&xas);
1431 continue;
1432 }
1433
1434 p[nr++] = find_subpage(page, xas.xa_index);
1435 if (nr == maxpages)
1436 break;
1437 }
1438 rcu_read_unlock();
1439
1440 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1441 iov_iter_advance(i, maxsize);
1442 return maxsize;
1443}
1444
1445/*
1446 * Extract a list of contiguous pages from an ITER_BVEC iterator. This does
1447 * not get references on the pages, nor does it get a pin on them.
1448 */
1449static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i,
1450 struct page ***pages, size_t maxsize,
1451 unsigned int maxpages,
1452 iov_iter_extraction_t extraction_flags,
1453 size_t *offset0)
1454{
1455 struct page **p, *page;
1456 size_t skip = i->iov_offset, offset, size;
1457 int k;
1458
1459 for (;;) {
1460 if (i->nr_segs == 0)
1461 return 0;
1462 size = min(maxsize, i->bvec->bv_len - skip);
1463 if (size)
1464 break;
1465 i->iov_offset = 0;
1466 i->nr_segs--;
1467 i->bvec++;
1468 skip = 0;
1469 }
1470
1471 skip += i->bvec->bv_offset;
1472 page = i->bvec->bv_page + skip / PAGE_SIZE;
1473 offset = skip % PAGE_SIZE;
1474 *offset0 = offset;
1475
1476 maxpages = want_pages_array(pages, size, offset, maxpages);
1477 if (!maxpages)
1478 return -ENOMEM;
1479 p = *pages;
1480 for (k = 0; k < maxpages; k++)
1481 p[k] = page + k;
1482
1483 size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
1484 iov_iter_advance(i, size);
1485 return size;
1486}
1487
1488/*
1489 * Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
1490 * This does not get references on the pages, nor does it get a pin on them.
1491 */
1492static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i,
1493 struct page ***pages, size_t maxsize,
1494 unsigned int maxpages,
1495 iov_iter_extraction_t extraction_flags,
1496 size_t *offset0)
1497{
1498 struct page **p, *page;
1499 const void *kaddr;
1500 size_t skip = i->iov_offset, offset, len, size;
1501 int k;
1502
1503 for (;;) {
1504 if (i->nr_segs == 0)
1505 return 0;
1506 size = min(maxsize, i->kvec->iov_len - skip);
1507 if (size)
1508 break;
1509 i->iov_offset = 0;
1510 i->nr_segs--;
1511 i->kvec++;
1512 skip = 0;
1513 }
1514
1515 kaddr = i->kvec->iov_base + skip;
1516 offset = (unsigned long)kaddr & ~PAGE_MASK;
1517 *offset0 = offset;
1518
1519 maxpages = want_pages_array(pages, size, offset, maxpages);
1520 if (!maxpages)
1521 return -ENOMEM;
1522 p = *pages;
1523
1524 kaddr -= offset;
1525 len = offset + size;
1526 for (k = 0; k < maxpages; k++) {
1527 size_t seg = min_t(size_t, len, PAGE_SIZE);
1528
1529 if (is_vmalloc_or_module_addr(kaddr))
1530 page = vmalloc_to_page(kaddr);
1531 else
1532 page = virt_to_page(kaddr);
1533
1534 p[k] = page;
1535 len -= seg;
1536 kaddr += PAGE_SIZE;
1537 }
1538
1539 size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
1540 iov_iter_advance(i, size);
1541 return size;
1542}
1543
1544/*
1545 * Extract a list of contiguous pages from a user iterator and get a pin on
1546 * each of them. This should only be used if the iterator is user-backed
1547 * (IOBUF/UBUF).
1548 *
1549 * It does not get refs on the pages, but the pages must be unpinned by the
1550 * caller once the transfer is complete.
1551 *
1552 * This is safe to be used where background IO/DMA *is* going to be modifying
1553 * the buffer; using a pin rather than a ref makes forces fork() to give the
1554 * child a copy of the page.
1555 */
1556static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
1557 struct page ***pages,
1558 size_t maxsize,
1559 unsigned int maxpages,
1560 iov_iter_extraction_t extraction_flags,
1561 size_t *offset0)
1562{
1563 unsigned long addr;
1564 unsigned int gup_flags = 0;
1565 size_t offset;
1566 int res;
1567
1568 if (i->data_source == ITER_DEST)
1569 gup_flags |= FOLL_WRITE;
1570 if (extraction_flags & ITER_ALLOW_P2PDMA)
1571 gup_flags |= FOLL_PCI_P2PDMA;
1572 if (i->nofault)
1573 gup_flags |= FOLL_NOFAULT;
1574
1575 addr = first_iovec_segment(i, &maxsize);
1576 *offset0 = offset = addr % PAGE_SIZE;
1577 addr &= PAGE_MASK;
1578 maxpages = want_pages_array(pages, maxsize, offset, maxpages);
1579 if (!maxpages)
1580 return -ENOMEM;
1581 res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
1582 if (unlikely(res <= 0))
1583 return res;
1584 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
1585 iov_iter_advance(i, maxsize);
1586 return maxsize;
1587}
1588
1589/**
1590 * iov_iter_extract_pages - Extract a list of contiguous pages from an iterator
1591 * @i: The iterator to extract from
1592 * @pages: Where to return the list of pages
1593 * @maxsize: The maximum amount of iterator to extract
1594 * @maxpages: The maximum size of the list of pages
1595 * @extraction_flags: Flags to qualify request
1596 * @offset0: Where to return the starting offset into (*@pages)[0]
1597 *
1598 * Extract a list of contiguous pages from the current point of the iterator,
1599 * advancing the iterator. The maximum number of pages and the maximum amount
1600 * of page contents can be set.
1601 *
1602 * If *@pages is NULL, a page list will be allocated to the required size and
1603 * *@pages will be set to its base. If *@pages is not NULL, it will be assumed
1604 * that the caller allocated a page list at least @maxpages in size and this
1605 * will be filled in.
1606 *
1607 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
1608 * be allowed on the pages extracted.
1609 *
1610 * The iov_iter_extract_will_pin() function can be used to query how cleanup
1611 * should be performed.
1612 *
1613 * Extra refs or pins on the pages may be obtained as follows:
1614 *
1615 * (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be
1616 * added to the pages, but refs will not be taken.
1617 * iov_iter_extract_will_pin() will return true.
1618 *
1619 * (*) If the iterator is ITER_KVEC, ITER_BVEC or ITER_XARRAY, the pages are
1620 * merely listed; no extra refs or pins are obtained.
1621 * iov_iter_extract_will_pin() will return 0.
1622 *
1623 * Note also:
1624 *
1625 * (*) Use with ITER_DISCARD is not supported as that has no content.
1626 *
1627 * On success, the function sets *@pages to the new pagelist, if allocated, and
1628 * sets *offset0 to the offset into the first page.
1629 *
1630 * It may also return -ENOMEM and -EFAULT.
1631 */
1632ssize_t iov_iter_extract_pages(struct iov_iter *i,
1633 struct page ***pages,
1634 size_t maxsize,
1635 unsigned int maxpages,
1636 iov_iter_extraction_t extraction_flags,
1637 size_t *offset0)
1638{
1639 maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
1640 if (!maxsize)
1641 return 0;
1642
1643 if (likely(user_backed_iter(i)))
1644 return iov_iter_extract_user_pages(i, pages, maxsize,
1645 maxpages, extraction_flags,
1646 offset0);
1647 if (iov_iter_is_kvec(i))
1648 return iov_iter_extract_kvec_pages(i, pages, maxsize,
1649 maxpages, extraction_flags,
1650 offset0);
1651 if (iov_iter_is_bvec(i))
1652 return iov_iter_extract_bvec_pages(i, pages, maxsize,
1653 maxpages, extraction_flags,
1654 offset0);
1655 if (iov_iter_is_xarray(i))
1656 return iov_iter_extract_xarray_pages(i, pages, maxsize,
1657 maxpages, extraction_flags,
1658 offset0);
1659 return -EFAULT;
1660}
1661EXPORT_SYMBOL_GPL(iov_iter_extract_pages);