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(to: iter_to, from, n: len);
25 len = raw_copy_to_user(dst: iter_to, src: from, size: 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(dst: iter_to, src: from, size: 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, from: iter_from, n: len);
55 res = raw_copy_from_user(dst: to, src: iter_from, size: len);
56 instrument_copy_from_user_after(to, from: iter_from, n: len, left: 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(to: iter_to, from: 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: to + progress, from: 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(uaddr: i->ubuf + i->iov_offset, size: 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(iter: 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(uaddr: p->iov_base + skip, size: 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(uaddr: i->ubuf + i->iov_offset, size: 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(iter: 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(uaddr: p->iov_base + skip, size: 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(iter: i, len: bytes, priv: (void *)addr,
186 ustep: copy_to_user_iter, step: 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(to: iter_to, from, n: len);
198 len = copy_mc_to_user(to: 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(to: iter_to, from: 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(iter: i, len: bytes, priv: (void *)addr,
241 ustep: copy_to_user_iter_mc, step: 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(iter: i, len: bytes, priv: addr,
250 ustep: copy_from_user_iter, step: 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(dst: to + progress, src: iter_from, size: 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(iter: i, len: bytes, priv: addr,
277 ustep: copy_from_user_iter_nocache,
278 step: 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(dst: to + progress, src: iter_from, size: 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(dst: to + progress, src: iter_from, cnt: 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(iter: i, len: bytes, priv: addr,
320 ustep: copy_from_user_iter_flushcache,
321 step: 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, n: 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, n: 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(iter: i, len: n, priv: kaddr + offset,
394 ustep: copy_to_user_iter_nofault,
395 step: 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, n: 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(to: iter_to, n: 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(s: iter_to, c: 0, n: len);
450 return 0;
451}
452
453size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
454{
455 return iterate_and_advance(iter: i, len: bytes, NULL,
456 ustep: zero_to_user_iter, step: zero_to_iter);
457}
458EXPORT_SYMBOL(iov_iter_zero);
459
460size_t copy_folio_from_iter_atomic(struct folio *folio, 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: &folio->page, offset, n: bytes))
466 return 0;
467 if (WARN_ON_ONCE(!i->data_source))
468 return 0;
469
470 do {
471 char *to = kmap_local_folio(folio, offset);
472
473 n = bytes - copied;
474 if (folio_test_partial_kmap(folio) &&
475 n > PAGE_SIZE - offset_in_page(offset))
476 n = PAGE_SIZE - offset_in_page(offset);
477
478 pagefault_disable();
479 n = __copy_from_iter(addr: to, bytes: n, i);
480 pagefault_enable();
481 kunmap_local(to);
482 copied += n;
483 offset += n;
484 } while (copied != bytes && n > 0);
485
486 return copied;
487}
488EXPORT_SYMBOL(copy_folio_from_iter_atomic);
489
490static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
491{
492 const struct bio_vec *bvec, *end;
493
494 if (!i->count)
495 return;
496 i->count -= size;
497
498 size += i->iov_offset;
499
500 for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
501 if (likely(size < bvec->bv_len))
502 break;
503 size -= bvec->bv_len;
504 }
505 i->iov_offset = size;
506 i->nr_segs -= bvec - i->bvec;
507 i->bvec = bvec;
508}
509
510static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
511{
512 const struct iovec *iov, *end;
513
514 if (!i->count)
515 return;
516 i->count -= size;
517
518 size += i->iov_offset; // from beginning of current segment
519 for (iov = iter_iov(iter: i), end = iov + i->nr_segs; iov < end; iov++) {
520 if (likely(size < iov->iov_len))
521 break;
522 size -= iov->iov_len;
523 }
524 i->iov_offset = size;
525 i->nr_segs -= iov - iter_iov(iter: i);
526 i->__iov = iov;
527}
528
529static void iov_iter_folioq_advance(struct iov_iter *i, size_t size)
530{
531 const struct folio_queue *folioq = i->folioq;
532 unsigned int slot = i->folioq_slot;
533
534 if (!i->count)
535 return;
536 i->count -= size;
537
538 if (slot >= folioq_nr_slots(folioq)) {
539 folioq = folioq->next;
540 slot = 0;
541 }
542
543 size += i->iov_offset; /* From beginning of current segment. */
544 do {
545 size_t fsize = folioq_folio_size(folioq, slot);
546
547 if (likely(size < fsize))
548 break;
549 size -= fsize;
550 slot++;
551 if (slot >= folioq_nr_slots(folioq) && folioq->next) {
552 folioq = folioq->next;
553 slot = 0;
554 }
555 } while (size);
556
557 i->iov_offset = size;
558 i->folioq_slot = slot;
559 i->folioq = folioq;
560}
561
562void iov_iter_advance(struct iov_iter *i, size_t size)
563{
564 if (unlikely(i->count < size))
565 size = i->count;
566 if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
567 i->iov_offset += size;
568 i->count -= size;
569 } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
570 /* iovec and kvec have identical layouts */
571 iov_iter_iovec_advance(i, size);
572 } else if (iov_iter_is_bvec(i)) {
573 iov_iter_bvec_advance(i, size);
574 } else if (iov_iter_is_folioq(i)) {
575 iov_iter_folioq_advance(i, size);
576 } else if (iov_iter_is_discard(i)) {
577 i->count -= size;
578 }
579}
580EXPORT_SYMBOL(iov_iter_advance);
581
582static void iov_iter_folioq_revert(struct iov_iter *i, size_t unroll)
583{
584 const struct folio_queue *folioq = i->folioq;
585 unsigned int slot = i->folioq_slot;
586
587 for (;;) {
588 size_t fsize;
589
590 if (slot == 0) {
591 folioq = folioq->prev;
592 slot = folioq_nr_slots(folioq);
593 }
594 slot--;
595
596 fsize = folioq_folio_size(folioq, slot);
597 if (unroll <= fsize) {
598 i->iov_offset = fsize - unroll;
599 break;
600 }
601 unroll -= fsize;
602 }
603
604 i->folioq_slot = slot;
605 i->folioq = folioq;
606}
607
608void iov_iter_revert(struct iov_iter *i, size_t unroll)
609{
610 if (!unroll)
611 return;
612 if (WARN_ON(unroll > MAX_RW_COUNT))
613 return;
614 i->count += unroll;
615 if (unlikely(iov_iter_is_discard(i)))
616 return;
617 if (unroll <= i->iov_offset) {
618 i->iov_offset -= unroll;
619 return;
620 }
621 unroll -= i->iov_offset;
622 if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
623 BUG(); /* We should never go beyond the start of the specified
624 * range since we might then be straying into pages that
625 * aren't pinned.
626 */
627 } else if (iov_iter_is_bvec(i)) {
628 const struct bio_vec *bvec = i->bvec;
629 while (1) {
630 size_t n = (--bvec)->bv_len;
631 i->nr_segs++;
632 if (unroll <= n) {
633 i->bvec = bvec;
634 i->iov_offset = n - unroll;
635 return;
636 }
637 unroll -= n;
638 }
639 } else if (iov_iter_is_folioq(i)) {
640 i->iov_offset = 0;
641 iov_iter_folioq_revert(i, unroll);
642 } else { /* same logics for iovec and kvec */
643 const struct iovec *iov = iter_iov(iter: i);
644 while (1) {
645 size_t n = (--iov)->iov_len;
646 i->nr_segs++;
647 if (unroll <= n) {
648 i->__iov = iov;
649 i->iov_offset = n - unroll;
650 return;
651 }
652 unroll -= n;
653 }
654 }
655}
656EXPORT_SYMBOL(iov_iter_revert);
657
658/*
659 * Return the count of just the current iov_iter segment.
660 */
661size_t iov_iter_single_seg_count(const struct iov_iter *i)
662{
663 if (i->nr_segs > 1) {
664 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
665 return min(i->count, iter_iov(i)->iov_len - i->iov_offset);
666 if (iov_iter_is_bvec(i))
667 return min(i->count, i->bvec->bv_len - i->iov_offset);
668 }
669 if (unlikely(iov_iter_is_folioq(i)))
670 return !i->count ? 0 :
671 umin(folioq_folio_size(i->folioq, i->folioq_slot), i->count);
672 return i->count;
673}
674EXPORT_SYMBOL(iov_iter_single_seg_count);
675
676void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
677 const struct kvec *kvec, unsigned long nr_segs,
678 size_t count)
679{
680 WARN_ON(direction & ~(READ | WRITE));
681 *i = (struct iov_iter){
682 .iter_type = ITER_KVEC,
683 .data_source = direction,
684 .kvec = kvec,
685 .nr_segs = nr_segs,
686 .iov_offset = 0,
687 .count = count
688 };
689}
690EXPORT_SYMBOL(iov_iter_kvec);
691
692void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
693 const struct bio_vec *bvec, unsigned long nr_segs,
694 size_t count)
695{
696 WARN_ON(direction & ~(READ | WRITE));
697 *i = (struct iov_iter){
698 .iter_type = ITER_BVEC,
699 .data_source = direction,
700 .bvec = bvec,
701 .nr_segs = nr_segs,
702 .iov_offset = 0,
703 .count = count
704 };
705}
706EXPORT_SYMBOL(iov_iter_bvec);
707
708/**
709 * iov_iter_folio_queue - Initialise an I/O iterator to use the folios in a folio queue
710 * @i: The iterator to initialise.
711 * @direction: The direction of the transfer.
712 * @folioq: The starting point in the folio queue.
713 * @first_slot: The first slot in the folio queue to use
714 * @offset: The offset into the folio in the first slot to start at
715 * @count: The size of the I/O buffer in bytes.
716 *
717 * Set up an I/O iterator to either draw data out of the pages attached to an
718 * inode or to inject data into those pages. The pages *must* be prevented
719 * from evaporation, either by taking a ref on them or locking them by the
720 * caller.
721 */
722void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction,
723 const struct folio_queue *folioq, unsigned int first_slot,
724 unsigned int offset, size_t count)
725{
726 BUG_ON(direction & ~1);
727 *i = (struct iov_iter) {
728 .iter_type = ITER_FOLIOQ,
729 .data_source = direction,
730 .folioq = folioq,
731 .folioq_slot = first_slot,
732 .count = count,
733 .iov_offset = offset,
734 };
735}
736EXPORT_SYMBOL(iov_iter_folio_queue);
737
738/**
739 * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
740 * @i: The iterator to initialise.
741 * @direction: The direction of the transfer.
742 * @xarray: The xarray to access.
743 * @start: The start file position.
744 * @count: The size of the I/O buffer in bytes.
745 *
746 * Set up an I/O iterator to either draw data out of the pages attached to an
747 * inode or to inject data into those pages. The pages *must* be prevented
748 * from evaporation, either by taking a ref on them or locking them by the
749 * caller.
750 */
751void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
752 struct xarray *xarray, loff_t start, size_t count)
753{
754 BUG_ON(direction & ~1);
755 *i = (struct iov_iter) {
756 .iter_type = ITER_XARRAY,
757 .data_source = direction,
758 .xarray = xarray,
759 .xarray_start = start,
760 .count = count,
761 .iov_offset = 0
762 };
763}
764EXPORT_SYMBOL(iov_iter_xarray);
765
766/**
767 * iov_iter_discard - Initialise an I/O iterator that discards data
768 * @i: The iterator to initialise.
769 * @direction: The direction of the transfer.
770 * @count: The size of the I/O buffer in bytes.
771 *
772 * Set up an I/O iterator that just discards everything that's written to it.
773 * It's only available as a READ iterator.
774 */
775void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
776{
777 BUG_ON(direction != READ);
778 *i = (struct iov_iter){
779 .iter_type = ITER_DISCARD,
780 .data_source = false,
781 .count = count,
782 .iov_offset = 0
783 };
784}
785EXPORT_SYMBOL(iov_iter_discard);
786
787static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
788{
789 const struct iovec *iov = iter_iov(iter: i);
790 unsigned long res = 0;
791 size_t size = i->count;
792 size_t skip = i->iov_offset;
793
794 do {
795 size_t len = iov->iov_len - skip;
796 if (len) {
797 res |= (unsigned long)iov->iov_base + skip;
798 if (len > size)
799 len = size;
800 res |= len;
801 size -= len;
802 }
803 iov++;
804 skip = 0;
805 } while (size);
806 return res;
807}
808
809static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
810{
811 const struct bio_vec *bvec = i->bvec;
812 unsigned res = 0;
813 size_t size = i->count;
814 unsigned skip = i->iov_offset;
815
816 do {
817 size_t len = bvec->bv_len - skip;
818 res |= (unsigned long)bvec->bv_offset + skip;
819 if (len > size)
820 len = size;
821 res |= len;
822 bvec++;
823 size -= len;
824 skip = 0;
825 } while (size);
826
827 return res;
828}
829
830unsigned long iov_iter_alignment(const struct iov_iter *i)
831{
832 if (likely(iter_is_ubuf(i))) {
833 size_t size = i->count;
834 if (size)
835 return ((unsigned long)i->ubuf + i->iov_offset) | size;
836 return 0;
837 }
838
839 /* iovec and kvec have identical layouts */
840 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
841 return iov_iter_alignment_iovec(i);
842
843 if (iov_iter_is_bvec(i))
844 return iov_iter_alignment_bvec(i);
845
846 /* With both xarray and folioq types, we're dealing with whole folios. */
847 if (iov_iter_is_folioq(i))
848 return i->iov_offset | i->count;
849 if (iov_iter_is_xarray(i))
850 return (i->xarray_start + i->iov_offset) | i->count;
851
852 return 0;
853}
854EXPORT_SYMBOL(iov_iter_alignment);
855
856unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
857{
858 unsigned long res = 0;
859 unsigned long v = 0;
860 size_t size = i->count;
861 unsigned k;
862
863 if (iter_is_ubuf(i))
864 return 0;
865
866 if (WARN_ON(!iter_is_iovec(i)))
867 return ~0U;
868
869 for (k = 0; k < i->nr_segs; k++) {
870 const struct iovec *iov = iter_iov(iter: i) + k;
871 if (iov->iov_len) {
872 unsigned long base = (unsigned long)iov->iov_base;
873 if (v) // if not the first one
874 res |= base | v; // this start | previous end
875 v = base + iov->iov_len;
876 if (size <= iov->iov_len)
877 break;
878 size -= iov->iov_len;
879 }
880 }
881 return res;
882}
883EXPORT_SYMBOL(iov_iter_gap_alignment);
884
885static int want_pages_array(struct page ***res, size_t size,
886 size_t start, unsigned int maxpages)
887{
888 unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
889
890 if (count > maxpages)
891 count = maxpages;
892 WARN_ON(!count); // caller should've prevented that
893 if (!*res) {
894 *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
895 if (!*res)
896 return 0;
897 }
898 return count;
899}
900
901static ssize_t iter_folioq_get_pages(struct iov_iter *iter,
902 struct page ***ppages, size_t maxsize,
903 unsigned maxpages, size_t *_start_offset)
904{
905 const struct folio_queue *folioq = iter->folioq;
906 struct page **pages;
907 unsigned int slot = iter->folioq_slot;
908 size_t extracted = 0, count = iter->count, iov_offset = iter->iov_offset;
909
910 if (slot >= folioq_nr_slots(folioq)) {
911 folioq = folioq->next;
912 slot = 0;
913 if (WARN_ON(iov_offset != 0))
914 return -EIO;
915 }
916
917 maxpages = want_pages_array(res: ppages, size: maxsize, start: iov_offset & ~PAGE_MASK, maxpages);
918 if (!maxpages)
919 return -ENOMEM;
920 *_start_offset = iov_offset & ~PAGE_MASK;
921 pages = *ppages;
922
923 for (;;) {
924 struct folio *folio = folioq_folio(folioq, slot);
925 size_t offset = iov_offset, fsize = folioq_folio_size(folioq, slot);
926 size_t part = PAGE_SIZE - offset % PAGE_SIZE;
927
928 if (offset < fsize) {
929 part = umin(part, umin(maxsize - extracted, fsize - offset));
930 count -= part;
931 iov_offset += part;
932 extracted += part;
933
934 *pages = folio_page(folio, offset / PAGE_SIZE);
935 get_page(page: *pages);
936 pages++;
937 maxpages--;
938 }
939
940 if (maxpages == 0 || extracted >= maxsize)
941 break;
942
943 if (iov_offset >= fsize) {
944 iov_offset = 0;
945 slot++;
946 if (slot == folioq_nr_slots(folioq) && folioq->next) {
947 folioq = folioq->next;
948 slot = 0;
949 }
950 }
951 }
952
953 iter->count = count;
954 iter->iov_offset = iov_offset;
955 iter->folioq = folioq;
956 iter->folioq_slot = slot;
957 return extracted;
958}
959
960static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
961 pgoff_t index, unsigned int nr_pages)
962{
963 XA_STATE(xas, xa, index);
964 struct folio *folio;
965 unsigned int ret = 0;
966
967 rcu_read_lock();
968 for (folio = xas_load(&xas); folio; folio = xas_next(xas: &xas)) {
969 if (xas_retry(xas: &xas, entry: folio))
970 continue;
971
972 /* Has the folio moved or been split? */
973 if (unlikely(folio != xas_reload(&xas))) {
974 xas_reset(xas: &xas);
975 continue;
976 }
977
978 pages[ret] = folio_file_page(folio, index: xas.xa_index);
979 folio_get(folio);
980 if (++ret == nr_pages)
981 break;
982 }
983 rcu_read_unlock();
984 return ret;
985}
986
987static ssize_t iter_xarray_get_pages(struct iov_iter *i,
988 struct page ***pages, size_t maxsize,
989 unsigned maxpages, size_t *_start_offset)
990{
991 unsigned nr, offset, count;
992 pgoff_t index;
993 loff_t pos;
994
995 pos = i->xarray_start + i->iov_offset;
996 index = pos >> PAGE_SHIFT;
997 offset = pos & ~PAGE_MASK;
998 *_start_offset = offset;
999
1000 count = want_pages_array(res: pages, size: maxsize, start: offset, maxpages);
1001 if (!count)
1002 return -ENOMEM;
1003 nr = iter_xarray_populate_pages(pages: *pages, xa: i->xarray, index, nr_pages: count);
1004 if (nr == 0)
1005 return 0;
1006
1007 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1008 i->iov_offset += maxsize;
1009 i->count -= maxsize;
1010 return maxsize;
1011}
1012
1013/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
1014static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
1015{
1016 size_t skip;
1017 long k;
1018
1019 if (iter_is_ubuf(i))
1020 return (unsigned long)i->ubuf + i->iov_offset;
1021
1022 for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
1023 const struct iovec *iov = iter_iov(iter: i) + k;
1024 size_t len = iov->iov_len - skip;
1025
1026 if (unlikely(!len))
1027 continue;
1028 if (*size > len)
1029 *size = len;
1030 return (unsigned long)iov->iov_base + skip;
1031 }
1032 BUG(); // if it had been empty, we wouldn't get called
1033}
1034
1035/* must be done on non-empty ITER_BVEC one */
1036static struct page *first_bvec_segment(const struct iov_iter *i,
1037 size_t *size, size_t *start)
1038{
1039 struct page *page;
1040 size_t skip = i->iov_offset, len;
1041
1042 len = i->bvec->bv_len - skip;
1043 if (*size > len)
1044 *size = len;
1045 skip += i->bvec->bv_offset;
1046 page = i->bvec->bv_page + skip / PAGE_SIZE;
1047 *start = skip % PAGE_SIZE;
1048 return page;
1049}
1050
1051static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
1052 struct page ***pages, size_t maxsize,
1053 unsigned int maxpages, size_t *start)
1054{
1055 unsigned int n, gup_flags = 0;
1056
1057 if (maxsize > i->count)
1058 maxsize = i->count;
1059 if (!maxsize)
1060 return 0;
1061 if (maxsize > MAX_RW_COUNT)
1062 maxsize = MAX_RW_COUNT;
1063
1064 if (likely(user_backed_iter(i))) {
1065 unsigned long addr;
1066 int res;
1067
1068 if (iov_iter_rw(i) != WRITE)
1069 gup_flags |= FOLL_WRITE;
1070 if (i->nofault)
1071 gup_flags |= FOLL_NOFAULT;
1072
1073 addr = first_iovec_segment(i, size: &maxsize);
1074 *start = addr % PAGE_SIZE;
1075 addr &= PAGE_MASK;
1076 n = want_pages_array(res: pages, size: maxsize, start: *start, maxpages);
1077 if (!n)
1078 return -ENOMEM;
1079 res = get_user_pages_fast(start: addr, nr_pages: n, gup_flags, pages: *pages);
1080 if (unlikely(res <= 0))
1081 return res;
1082 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
1083 iov_iter_advance(i, maxsize);
1084 return maxsize;
1085 }
1086 if (iov_iter_is_bvec(i)) {
1087 struct page **p;
1088 struct page *page;
1089
1090 page = first_bvec_segment(i, size: &maxsize, start);
1091 n = want_pages_array(res: pages, size: maxsize, start: *start, maxpages);
1092 if (!n)
1093 return -ENOMEM;
1094 p = *pages;
1095 for (int k = 0; k < n; k++) {
1096 struct folio *folio = page_folio(page + k);
1097 p[k] = page + k;
1098 if (!folio_test_slab(folio))
1099 folio_get(folio);
1100 }
1101 maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
1102 i->count -= maxsize;
1103 i->iov_offset += maxsize;
1104 if (i->iov_offset == i->bvec->bv_len) {
1105 i->iov_offset = 0;
1106 i->bvec++;
1107 i->nr_segs--;
1108 }
1109 return maxsize;
1110 }
1111 if (iov_iter_is_folioq(i))
1112 return iter_folioq_get_pages(iter: i, ppages: pages, maxsize, maxpages, start_offset: start);
1113 if (iov_iter_is_xarray(i))
1114 return iter_xarray_get_pages(i, pages, maxsize, maxpages, start_offset: start);
1115 return -EFAULT;
1116}
1117
1118ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
1119 size_t maxsize, unsigned maxpages, size_t *start)
1120{
1121 if (!maxpages)
1122 return 0;
1123 BUG_ON(!pages);
1124
1125 return __iov_iter_get_pages_alloc(i, pages: &pages, maxsize, maxpages, start);
1126}
1127EXPORT_SYMBOL(iov_iter_get_pages2);
1128
1129ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
1130 struct page ***pages, size_t maxsize, size_t *start)
1131{
1132 ssize_t len;
1133
1134 *pages = NULL;
1135
1136 len = __iov_iter_get_pages_alloc(i, pages, maxsize, maxpages: ~0U, start);
1137 if (len <= 0) {
1138 kvfree(addr: *pages);
1139 *pages = NULL;
1140 }
1141 return len;
1142}
1143EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
1144
1145static int iov_npages(const struct iov_iter *i, int maxpages)
1146{
1147 size_t skip = i->iov_offset, size = i->count;
1148 const struct iovec *p;
1149 int npages = 0;
1150
1151 for (p = iter_iov(iter: i); size; skip = 0, p++) {
1152 unsigned offs = offset_in_page(p->iov_base + skip);
1153 size_t len = min(p->iov_len - skip, size);
1154
1155 if (len) {
1156 size -= len;
1157 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1158 if (unlikely(npages > maxpages))
1159 return maxpages;
1160 }
1161 }
1162 return npages;
1163}
1164
1165static int bvec_npages(const struct iov_iter *i, int maxpages)
1166{
1167 size_t skip = i->iov_offset, size = i->count;
1168 const struct bio_vec *p;
1169 int npages = 0;
1170
1171 for (p = i->bvec; size; skip = 0, p++) {
1172 unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
1173 size_t len = min(p->bv_len - skip, size);
1174
1175 size -= len;
1176 npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1177 if (unlikely(npages > maxpages))
1178 return maxpages;
1179 }
1180 return npages;
1181}
1182
1183int iov_iter_npages(const struct iov_iter *i, int maxpages)
1184{
1185 if (unlikely(!i->count))
1186 return 0;
1187 if (likely(iter_is_ubuf(i))) {
1188 unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
1189 int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
1190 return min(npages, maxpages);
1191 }
1192 /* iovec and kvec have identical layouts */
1193 if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1194 return iov_npages(i, maxpages);
1195 if (iov_iter_is_bvec(i))
1196 return bvec_npages(i, maxpages);
1197 if (iov_iter_is_folioq(i)) {
1198 unsigned offset = i->iov_offset % PAGE_SIZE;
1199 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1200 return min(npages, maxpages);
1201 }
1202 if (iov_iter_is_xarray(i)) {
1203 unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
1204 int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1205 return min(npages, maxpages);
1206 }
1207 return 0;
1208}
1209EXPORT_SYMBOL(iov_iter_npages);
1210
1211const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1212{
1213 *new = *old;
1214 if (iov_iter_is_bvec(i: new))
1215 return new->bvec = kmemdup(new->bvec,
1216 new->nr_segs * sizeof(struct bio_vec),
1217 flags);
1218 else if (iov_iter_is_kvec(i: new) || iter_is_iovec(i: new))
1219 /* iovec and kvec have identical layout */
1220 return new->__iov = kmemdup(new->__iov,
1221 new->nr_segs * sizeof(struct iovec),
1222 flags);
1223 return NULL;
1224}
1225EXPORT_SYMBOL(dup_iter);
1226
1227static __noclone int copy_compat_iovec_from_user(struct iovec *iov,
1228 const struct iovec __user *uvec, u32 nr_segs)
1229{
1230 const struct compat_iovec __user *uiov =
1231 (const struct compat_iovec __user *)uvec;
1232 int ret = -EFAULT;
1233 u32 i;
1234
1235 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1236 return -EFAULT;
1237
1238 for (i = 0; i < nr_segs; i++) {
1239 compat_uptr_t buf;
1240 compat_ssize_t len;
1241
1242 unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
1243 unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
1244
1245 /* check for compat_size_t not fitting in compat_ssize_t .. */
1246 if (len < 0) {
1247 ret = -EINVAL;
1248 goto uaccess_end;
1249 }
1250 iov[i].iov_base = compat_ptr(uptr: buf);
1251 iov[i].iov_len = len;
1252 }
1253
1254 ret = 0;
1255uaccess_end:
1256 user_access_end();
1257 return ret;
1258}
1259
1260static __noclone int copy_iovec_from_user(struct iovec *iov,
1261 const struct iovec __user *uiov, unsigned long nr_segs)
1262{
1263 int ret = -EFAULT;
1264
1265 if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1266 return -EFAULT;
1267
1268 do {
1269 void __user *buf;
1270 ssize_t len;
1271
1272 unsafe_get_user(len, &uiov->iov_len, uaccess_end);
1273 unsafe_get_user(buf, &uiov->iov_base, uaccess_end);
1274
1275 /* check for size_t not fitting in ssize_t .. */
1276 if (unlikely(len < 0)) {
1277 ret = -EINVAL;
1278 goto uaccess_end;
1279 }
1280 iov->iov_base = buf;
1281 iov->iov_len = len;
1282
1283 uiov++; iov++;
1284 } while (--nr_segs);
1285
1286 ret = 0;
1287uaccess_end:
1288 user_access_end();
1289 return ret;
1290}
1291
1292struct iovec *iovec_from_user(const struct iovec __user *uvec,
1293 unsigned long nr_segs, unsigned long fast_segs,
1294 struct iovec *fast_iov, bool compat)
1295{
1296 struct iovec *iov = fast_iov;
1297 int ret;
1298
1299 /*
1300 * SuS says "The readv() function *may* fail if the iovcnt argument was
1301 * less than or equal to 0, or greater than {IOV_MAX}. Linux has
1302 * traditionally returned zero for zero segments, so...
1303 */
1304 if (nr_segs == 0)
1305 return iov;
1306 if (nr_segs > UIO_MAXIOV)
1307 return ERR_PTR(error: -EINVAL);
1308 if (nr_segs > fast_segs) {
1309 iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
1310 if (!iov)
1311 return ERR_PTR(error: -ENOMEM);
1312 }
1313
1314 if (unlikely(compat))
1315 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
1316 else
1317 ret = copy_iovec_from_user(iov, uiov: uvec, nr_segs);
1318 if (ret) {
1319 if (iov != fast_iov)
1320 kfree(objp: iov);
1321 return ERR_PTR(error: ret);
1322 }
1323
1324 return iov;
1325}
1326
1327/*
1328 * Single segment iovec supplied by the user, import it as ITER_UBUF.
1329 */
1330static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
1331 struct iovec **iovp, struct iov_iter *i,
1332 bool compat)
1333{
1334 struct iovec *iov = *iovp;
1335 ssize_t ret;
1336
1337 *iovp = NULL;
1338
1339 if (compat)
1340 ret = copy_compat_iovec_from_user(iov, uvec, nr_segs: 1);
1341 else
1342 ret = copy_iovec_from_user(iov, uiov: uvec, nr_segs: 1);
1343 if (unlikely(ret))
1344 return ret;
1345
1346 ret = import_ubuf(type, buf: iov->iov_base, len: iov->iov_len, i);
1347 if (unlikely(ret))
1348 return ret;
1349 return i->count;
1350}
1351
1352ssize_t __import_iovec(int type, const struct iovec __user *uvec,
1353 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
1354 struct iov_iter *i, bool compat)
1355{
1356 ssize_t total_len = 0;
1357 unsigned long seg;
1358 struct iovec *iov;
1359
1360 if (nr_segs == 1)
1361 return __import_iovec_ubuf(type, uvec, iovp, i, compat);
1362
1363 iov = iovec_from_user(uvec, nr_segs, fast_segs, fast_iov: *iovp, compat);
1364 if (IS_ERR(ptr: iov)) {
1365 *iovp = NULL;
1366 return PTR_ERR(ptr: iov);
1367 }
1368
1369 /*
1370 * According to the Single Unix Specification we should return EINVAL if
1371 * an element length is < 0 when cast to ssize_t or if the total length
1372 * would overflow the ssize_t return value of the system call.
1373 *
1374 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
1375 * overflow case.
1376 */
1377 for (seg = 0; seg < nr_segs; seg++) {
1378 ssize_t len = (ssize_t)iov[seg].iov_len;
1379
1380 if (!access_ok(iov[seg].iov_base, len)) {
1381 if (iov != *iovp)
1382 kfree(objp: iov);
1383 *iovp = NULL;
1384 return -EFAULT;
1385 }
1386
1387 if (len > MAX_RW_COUNT - total_len) {
1388 len = MAX_RW_COUNT - total_len;
1389 iov[seg].iov_len = len;
1390 }
1391 total_len += len;
1392 }
1393
1394 iov_iter_init(i, type, iov, nr_segs, total_len);
1395 if (iov == *iovp)
1396 *iovp = NULL;
1397 else
1398 *iovp = iov;
1399 return total_len;
1400}
1401
1402/**
1403 * import_iovec() - Copy an array of &struct iovec from userspace
1404 * into the kernel, check that it is valid, and initialize a new
1405 * &struct iov_iter iterator to access it.
1406 *
1407 * @type: One of %READ or %WRITE.
1408 * @uvec: Pointer to the userspace array.
1409 * @nr_segs: Number of elements in userspace array.
1410 * @fast_segs: Number of elements in @iov.
1411 * @iovp: (input and output parameter) Pointer to pointer to (usually small
1412 * on-stack) kernel array.
1413 * @i: Pointer to iterator that will be initialized on success.
1414 *
1415 * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1416 * then this function places %NULL in *@iov on return. Otherwise, a new
1417 * array will be allocated and the result placed in *@iov. This means that
1418 * the caller may call kfree() on *@iov regardless of whether the small
1419 * on-stack array was used or not (and regardless of whether this function
1420 * returns an error or not).
1421 *
1422 * Return: Negative error code on error, bytes imported on success
1423 */
1424ssize_t import_iovec(int type, const struct iovec __user *uvec,
1425 unsigned nr_segs, unsigned fast_segs,
1426 struct iovec **iovp, struct iov_iter *i)
1427{
1428 return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
1429 in_compat_syscall());
1430}
1431EXPORT_SYMBOL(import_iovec);
1432
1433int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
1434{
1435 if (len > MAX_RW_COUNT)
1436 len = MAX_RW_COUNT;
1437 if (unlikely(!access_ok(buf, len)))
1438 return -EFAULT;
1439
1440 iov_iter_ubuf(i, direction: rw, buf, count: len);
1441 return 0;
1442}
1443EXPORT_SYMBOL_GPL(import_ubuf);
1444
1445/**
1446 * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
1447 * iov_iter_save_state() was called.
1448 *
1449 * @i: &struct iov_iter to restore
1450 * @state: state to restore from
1451 *
1452 * Used after iov_iter_save_state() to bring restore @i, if operations may
1453 * have advanced it.
1454 *
1455 * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
1456 */
1457void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
1458{
1459 if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) &&
1460 !iter_is_ubuf(i)) && !iov_iter_is_kvec(i))
1461 return;
1462 i->iov_offset = state->iov_offset;
1463 i->count = state->count;
1464 if (iter_is_ubuf(i))
1465 return;
1466 /*
1467 * For the *vec iters, nr_segs + iov is constant - if we increment
1468 * the vec, then we also decrement the nr_segs count. Hence we don't
1469 * need to track both of these, just one is enough and we can deduct
1470 * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
1471 * size, so we can just increment the iov pointer as they are unionzed.
1472 * ITER_BVEC _may_ be the same size on some archs, but on others it is
1473 * not. Be safe and handle it separately.
1474 */
1475 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
1476 if (iov_iter_is_bvec(i))
1477 i->bvec -= state->nr_segs - i->nr_segs;
1478 else
1479 i->__iov -= state->nr_segs - i->nr_segs;
1480 i->nr_segs = state->nr_segs;
1481}
1482
1483/*
1484 * Extract a list of contiguous pages from an ITER_FOLIOQ iterator. This does
1485 * not get references on the pages, nor does it get a pin on them.
1486 */
1487static ssize_t iov_iter_extract_folioq_pages(struct iov_iter *i,
1488 struct page ***pages, size_t maxsize,
1489 unsigned int maxpages,
1490 iov_iter_extraction_t extraction_flags,
1491 size_t *offset0)
1492{
1493 const struct folio_queue *folioq = i->folioq;
1494 struct page **p;
1495 unsigned int nr = 0;
1496 size_t extracted = 0, offset, slot = i->folioq_slot;
1497
1498 if (slot >= folioq_nr_slots(folioq)) {
1499 folioq = folioq->next;
1500 slot = 0;
1501 if (WARN_ON(i->iov_offset != 0))
1502 return -EIO;
1503 }
1504
1505 offset = i->iov_offset & ~PAGE_MASK;
1506 *offset0 = offset;
1507
1508 maxpages = want_pages_array(res: pages, size: maxsize, start: offset, maxpages);
1509 if (!maxpages)
1510 return -ENOMEM;
1511 p = *pages;
1512
1513 for (;;) {
1514 struct folio *folio = folioq_folio(folioq, slot);
1515 size_t offset = i->iov_offset, fsize = folioq_folio_size(folioq, slot);
1516 size_t part = PAGE_SIZE - offset % PAGE_SIZE;
1517
1518 if (offset < fsize) {
1519 part = umin(part, umin(maxsize - extracted, fsize - offset));
1520 i->count -= part;
1521 i->iov_offset += part;
1522 extracted += part;
1523
1524 p[nr++] = folio_page(folio, offset / PAGE_SIZE);
1525 }
1526
1527 if (nr >= maxpages || extracted >= maxsize)
1528 break;
1529
1530 if (i->iov_offset >= fsize) {
1531 i->iov_offset = 0;
1532 slot++;
1533 if (slot == folioq_nr_slots(folioq) && folioq->next) {
1534 folioq = folioq->next;
1535 slot = 0;
1536 }
1537 }
1538 }
1539
1540 i->folioq = folioq;
1541 i->folioq_slot = slot;
1542 return extracted;
1543}
1544
1545/*
1546 * Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
1547 * get references on the pages, nor does it get a pin on them.
1548 */
1549static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
1550 struct page ***pages, size_t maxsize,
1551 unsigned int maxpages,
1552 iov_iter_extraction_t extraction_flags,
1553 size_t *offset0)
1554{
1555 struct page **p;
1556 struct folio *folio;
1557 unsigned int nr = 0, offset;
1558 loff_t pos = i->xarray_start + i->iov_offset;
1559 XA_STATE(xas, i->xarray, pos >> PAGE_SHIFT);
1560
1561 offset = pos & ~PAGE_MASK;
1562 *offset0 = offset;
1563
1564 maxpages = want_pages_array(res: pages, size: maxsize, start: offset, maxpages);
1565 if (!maxpages)
1566 return -ENOMEM;
1567 p = *pages;
1568
1569 rcu_read_lock();
1570 for (folio = xas_load(&xas); folio; folio = xas_next(xas: &xas)) {
1571 if (xas_retry(xas: &xas, entry: folio))
1572 continue;
1573
1574 /* Has the folio moved or been split? */
1575 if (unlikely(folio != xas_reload(&xas))) {
1576 xas_reset(xas: &xas);
1577 continue;
1578 }
1579
1580 p[nr++] = folio_file_page(folio, index: xas.xa_index);
1581 if (nr == maxpages)
1582 break;
1583 }
1584 rcu_read_unlock();
1585
1586 maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1587 iov_iter_advance(i, maxsize);
1588 return maxsize;
1589}
1590
1591/*
1592 * Extract a list of virtually contiguous pages from an ITER_BVEC iterator.
1593 * This does not get references on the pages, nor does it get a pin on them.
1594 */
1595static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i,
1596 struct page ***pages, size_t maxsize,
1597 unsigned int maxpages,
1598 iov_iter_extraction_t extraction_flags,
1599 size_t *offset0)
1600{
1601 size_t skip = i->iov_offset, size = 0;
1602 struct bvec_iter bi;
1603 int k = 0;
1604
1605 if (i->nr_segs == 0)
1606 return 0;
1607
1608 if (i->iov_offset == i->bvec->bv_len) {
1609 i->iov_offset = 0;
1610 i->nr_segs--;
1611 i->bvec++;
1612 skip = 0;
1613 }
1614 bi.bi_idx = 0;
1615 bi.bi_size = maxsize;
1616 bi.bi_bvec_done = skip;
1617
1618 maxpages = want_pages_array(res: pages, size: maxsize, start: skip, maxpages);
1619
1620 while (bi.bi_size && bi.bi_idx < i->nr_segs) {
1621 struct bio_vec bv = bvec_iter_bvec(i->bvec, bi);
1622
1623 /*
1624 * The iov_iter_extract_pages interface only allows an offset
1625 * into the first page. Break out of the loop if we see an
1626 * offset into subsequent pages, the caller will have to call
1627 * iov_iter_extract_pages again for the reminder.
1628 */
1629 if (k) {
1630 if (bv.bv_offset)
1631 break;
1632 } else {
1633 *offset0 = bv.bv_offset;
1634 }
1635
1636 (*pages)[k++] = bv.bv_page;
1637 size += bv.bv_len;
1638
1639 if (k >= maxpages)
1640 break;
1641
1642 /*
1643 * We are done when the end of the bvec doesn't align to a page
1644 * boundary as that would create a hole in the returned space.
1645 * The caller will handle this with another call to
1646 * iov_iter_extract_pages.
1647 */
1648 if (bv.bv_offset + bv.bv_len != PAGE_SIZE)
1649 break;
1650
1651 bvec_iter_advance_single(bv: i->bvec, iter: &bi, bytes: bv.bv_len);
1652 }
1653
1654 iov_iter_advance(i, size);
1655 return size;
1656}
1657
1658/*
1659 * Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
1660 * This does not get references on the pages, nor does it get a pin on them.
1661 */
1662static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i,
1663 struct page ***pages, size_t maxsize,
1664 unsigned int maxpages,
1665 iov_iter_extraction_t extraction_flags,
1666 size_t *offset0)
1667{
1668 struct page **p, *page;
1669 const void *kaddr;
1670 size_t skip = i->iov_offset, offset, len, size;
1671 int k;
1672
1673 for (;;) {
1674 if (i->nr_segs == 0)
1675 return 0;
1676 size = min(maxsize, i->kvec->iov_len - skip);
1677 if (size)
1678 break;
1679 i->iov_offset = 0;
1680 i->nr_segs--;
1681 i->kvec++;
1682 skip = 0;
1683 }
1684
1685 kaddr = i->kvec->iov_base + skip;
1686 offset = (unsigned long)kaddr & ~PAGE_MASK;
1687 *offset0 = offset;
1688
1689 maxpages = want_pages_array(res: pages, size, start: offset, maxpages);
1690 if (!maxpages)
1691 return -ENOMEM;
1692 p = *pages;
1693
1694 kaddr -= offset;
1695 len = offset + size;
1696 for (k = 0; k < maxpages; k++) {
1697 size_t seg = min_t(size_t, len, PAGE_SIZE);
1698
1699 if (is_vmalloc_or_module_addr(x: kaddr))
1700 page = vmalloc_to_page(addr: kaddr);
1701 else
1702 page = virt_to_page(kaddr);
1703
1704 p[k] = page;
1705 len -= seg;
1706 kaddr += PAGE_SIZE;
1707 }
1708
1709 size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
1710 iov_iter_advance(i, size);
1711 return size;
1712}
1713
1714/*
1715 * Extract a list of contiguous pages from a user iterator and get a pin on
1716 * each of them. This should only be used if the iterator is user-backed
1717 * (IOBUF/UBUF).
1718 *
1719 * It does not get refs on the pages, but the pages must be unpinned by the
1720 * caller once the transfer is complete.
1721 *
1722 * This is safe to be used where background IO/DMA *is* going to be modifying
1723 * the buffer; using a pin rather than a ref makes forces fork() to give the
1724 * child a copy of the page.
1725 */
1726static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
1727 struct page ***pages,
1728 size_t maxsize,
1729 unsigned int maxpages,
1730 iov_iter_extraction_t extraction_flags,
1731 size_t *offset0)
1732{
1733 unsigned long addr;
1734 unsigned int gup_flags = 0;
1735 size_t offset;
1736 int res;
1737
1738 if (i->data_source == ITER_DEST)
1739 gup_flags |= FOLL_WRITE;
1740 if (extraction_flags & ITER_ALLOW_P2PDMA)
1741 gup_flags |= FOLL_PCI_P2PDMA;
1742 if (i->nofault)
1743 gup_flags |= FOLL_NOFAULT;
1744
1745 addr = first_iovec_segment(i, size: &maxsize);
1746 *offset0 = offset = addr % PAGE_SIZE;
1747 addr &= PAGE_MASK;
1748 maxpages = want_pages_array(res: pages, size: maxsize, start: offset, maxpages);
1749 if (!maxpages)
1750 return -ENOMEM;
1751 res = pin_user_pages_fast(start: addr, nr_pages: maxpages, gup_flags, pages: *pages);
1752 if (unlikely(res <= 0))
1753 return res;
1754 maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
1755 iov_iter_advance(i, maxsize);
1756 return maxsize;
1757}
1758
1759/**
1760 * iov_iter_extract_pages - Extract a list of contiguous pages from an iterator
1761 * @i: The iterator to extract from
1762 * @pages: Where to return the list of pages
1763 * @maxsize: The maximum amount of iterator to extract
1764 * @maxpages: The maximum size of the list of pages
1765 * @extraction_flags: Flags to qualify request
1766 * @offset0: Where to return the starting offset into (*@pages)[0]
1767 *
1768 * Extract a list of contiguous pages from the current point of the iterator,
1769 * advancing the iterator. The maximum number of pages and the maximum amount
1770 * of page contents can be set.
1771 *
1772 * If *@pages is NULL, a page list will be allocated to the required size and
1773 * *@pages will be set to its base. If *@pages is not NULL, it will be assumed
1774 * that the caller allocated a page list at least @maxpages in size and this
1775 * will be filled in.
1776 *
1777 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
1778 * be allowed on the pages extracted.
1779 *
1780 * The iov_iter_extract_will_pin() function can be used to query how cleanup
1781 * should be performed.
1782 *
1783 * Extra refs or pins on the pages may be obtained as follows:
1784 *
1785 * (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be
1786 * added to the pages, but refs will not be taken.
1787 * iov_iter_extract_will_pin() will return true.
1788 *
1789 * (*) If the iterator is ITER_KVEC, ITER_BVEC, ITER_FOLIOQ or ITER_XARRAY, the
1790 * pages are merely listed; no extra refs or pins are obtained.
1791 * iov_iter_extract_will_pin() will return 0.
1792 *
1793 * Note also:
1794 *
1795 * (*) Use with ITER_DISCARD is not supported as that has no content.
1796 *
1797 * On success, the function sets *@pages to the new pagelist, if allocated, and
1798 * sets *offset0 to the offset into the first page.
1799 *
1800 * It may also return -ENOMEM and -EFAULT.
1801 */
1802ssize_t iov_iter_extract_pages(struct iov_iter *i,
1803 struct page ***pages,
1804 size_t maxsize,
1805 unsigned int maxpages,
1806 iov_iter_extraction_t extraction_flags,
1807 size_t *offset0)
1808{
1809 maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
1810 if (!maxsize)
1811 return 0;
1812
1813 if (likely(user_backed_iter(i)))
1814 return iov_iter_extract_user_pages(i, pages, maxsize,
1815 maxpages, extraction_flags,
1816 offset0);
1817 if (iov_iter_is_kvec(i))
1818 return iov_iter_extract_kvec_pages(i, pages, maxsize,
1819 maxpages, extraction_flags,
1820 offset0);
1821 if (iov_iter_is_bvec(i))
1822 return iov_iter_extract_bvec_pages(i, pages, maxsize,
1823 maxpages, extraction_flags,
1824 offset0);
1825 if (iov_iter_is_folioq(i))
1826 return iov_iter_extract_folioq_pages(i, pages, maxsize,
1827 maxpages, extraction_flags,
1828 offset0);
1829 if (iov_iter_is_xarray(i))
1830 return iov_iter_extract_xarray_pages(i, pages, maxsize,
1831 maxpages, extraction_flags,
1832 offset0);
1833 return -EFAULT;
1834}
1835EXPORT_SYMBOL_GPL(iov_iter_extract_pages);
1836