1	// SPDX-License-Identifier: GPL-2.0-only
2	#include <linux/kernel.h>
3	#include <linux/errno.h>
4	#include <linux/err.h>
5	#include <linux/spinlock.h>
6
7	#include <linux/mm.h>
8	#include <linux/memremap.h>
9	#include <linux/pagemap.h>
10	#include <linux/rmap.h>
11	#include <linux/swap.h>
12	#include <linux/swapops.h>
13	#include <linux/secretmem.h>
14
15	#include <linux/sched/signal.h>
16	#include <linux/rwsem.h>
17	#include <linux/hugetlb.h>
18	#include <linux/migrate.h>
19	#include <linux/mm_inline.h>
20	#include <linux/sched/mm.h>
21	#include <linux/shmem_fs.h>
22
23	#include <asm/mmu_context.h>
24	#include <asm/tlbflush.h>
25
26	#include "internal.h"
27
28	struct follow_page_context {
29	struct dev_pagemap *pgmap;
30	unsigned int page_mask;
31	};
32
33	static inline void sanity_check_pinned_pages(struct page **pages,
34	unsigned long npages)
35	{
36	if (!IS_ENABLED(CONFIG_DEBUG_VM))
37	return;
38
39	/*
40	* We only pin anonymous pages if they are exclusive. Once pinned, we
41	* can no longer turn them possibly shared and PageAnonExclusive() will
42	* stick around until the page is freed.
43	*
44	* We'd like to verify that our pinned anonymous pages are still mapped
45	* exclusively. The issue with anon THP is that we don't know how
46	* they are/were mapped when pinning them. However, for anon
47	* THP we can assume that either the given page (PTE-mapped THP) or
48	* the head page (PMD-mapped THP) should be PageAnonExclusive(). If
49	* neither is the case, there is certainly something wrong.
50	*/
51	for (; npages; npages--, pages++) {
52	struct page *page = *pages;
53	struct folio *folio = page_folio(page);
54
55	if (is_zero_page(page) ||
56	!folio_test_anon(folio))
57	continue;
58	if (!folio_test_large(folio) || folio_test_hugetlb(folio))
59	VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
60	else
61	/* Either a PTE-mapped or a PMD-mapped THP. */
62	VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) &&
63	!PageAnonExclusive(page), page);
64	}
65	}
66
67	/*
68	* Return the folio with ref appropriately incremented,
69	* or NULL if that failed.
70	*/
71	static inline struct folio *try_get_folio(struct page *page, int refs)
72	{
73	struct folio *folio;
74
75	retry:
76	folio = page_folio(page);
77	if (WARN_ON_ONCE(folio_ref_count(folio) < 0))
78	return NULL;
79	if (unlikely(!folio_ref_try_add_rcu(folio, refs)))
80	return NULL;
81
82	/*
83	* At this point we have a stable reference to the folio; but it
84	* could be that between calling page_folio() and the refcount
85	* increment, the folio was split, in which case we'd end up
86	* holding a reference on a folio that has nothing to do with the page
87	* we were given anymore.
88	* So now that the folio is stable, recheck that the page still
89	* belongs to this folio.
90	*/
91	if (unlikely(page_folio(page) != folio)) {
92	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
93	folio_put_refs(folio, refs);
94	goto retry;
95	}
96
97	return folio;
98	}
99
100	/**
101	* try_grab_folio() - Attempt to get or pin a folio.
102	* @page: pointer to page to be grabbed
103	* @refs: the value to (effectively) add to the folio's refcount
104	* @flags: gup flags: these are the FOLL_* flag values.
105	*
106	* "grab" names in this file mean, "look at flags to decide whether to use
107	* FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
108	*
109	* Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
110	* same time. (That's true throughout the get_user_pages*() and
111	* pin_user_pages*() APIs.) Cases:
112	*
113	* FOLL_GET: folio's refcount will be incremented by @refs.
114	*
115	* FOLL_PIN on large folios: folio's refcount will be incremented by
116	* @refs, and its pincount will be incremented by @refs.
117	*
118	* FOLL_PIN on single-page folios: folio's refcount will be incremented by
119	* @refs * GUP_PIN_COUNTING_BIAS.
120	*
121	* Return: The folio containing @page (with refcount appropriately
122	* incremented) for success, or NULL upon failure. If neither FOLL_GET
123	* nor FOLL_PIN was set, that's considered failure, and furthermore,
124	* a likely bug in the caller, so a warning is also emitted.
125	*/
126	struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
127	{
128	struct folio *folio;
129
130	if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
131	return NULL;
132
133	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
134	return NULL;
135
136	if (flags & FOLL_GET)
137	return try_get_folio(page, refs);
138
139	/* FOLL_PIN is set */
140
141	/*
142	* Don't take a pin on the zero page - it's not going anywhere
143	* and it is used in a *lot* of places.
144	*/
145	if (is_zero_page(page))
146	return page_folio(page);
147
148	folio = try_get_folio(page, refs);
149	if (!folio)
150	return NULL;
151
152	/*
153	* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
154	* right zone, so fail and let the caller fall back to the slow
155	* path.
156	*/
157	if (unlikely((flags & FOLL_LONGTERM) &&
158	!folio_is_longterm_pinnable(folio))) {
159	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
160	folio_put_refs(folio, refs);
161	return NULL;
162	}
163
164	/*
165	* When pinning a large folio, use an exact count to track it.
166	*
167	* However, be sure to *also* increment the normal folio
168	* refcount field at least once, so that the folio really
169	* is pinned. That's why the refcount from the earlier
170	* try_get_folio() is left intact.
171	*/
172	if (folio_test_large(folio))
173	atomic_add(i: refs, v: &folio->_pincount);
174	else
175	folio_ref_add(folio,
176	nr: refs * (GUP_PIN_COUNTING_BIAS - 1));
177	/*
178	* Adjust the pincount before re-checking the PTE for changes.
179	* This is essentially a smp_mb() and is paired with a memory
180	* barrier in page_try_share_anon_rmap().
181	*/
182	smp_mb__after_atomic();
183
184	node_stat_mod_folio(folio, item: NR_FOLL_PIN_ACQUIRED, nr: refs);
185
186	return folio;
187	}
188
189	static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
190	{
191	if (flags & FOLL_PIN) {
192	if (is_zero_folio(folio))
193	return;
194	node_stat_mod_folio(folio, item: NR_FOLL_PIN_RELEASED, nr: refs);
195	if (folio_test_large(folio))
196	atomic_sub(i: refs, v: &folio->_pincount);
197	else
198	refs *= GUP_PIN_COUNTING_BIAS;
199	}
200
201	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
202	folio_put_refs(folio, refs);
203	}
204
205	/**
206	* try_grab_page() - elevate a page's refcount by a flag-dependent amount
207	* @page: pointer to page to be grabbed
208	* @flags: gup flags: these are the FOLL_* flag values.
209	*
210	* This might not do anything at all, depending on the flags argument.
211	*
212	* "grab" names in this file mean, "look at flags to decide whether to use
213	* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
214	*
215	* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
216	* time. Cases: please see the try_grab_folio() documentation, with
217	* "refs=1".
218	*
219	* Return: 0 for success, or if no action was required (if neither FOLL_PIN
220	* nor FOLL_GET was set, nothing is done). A negative error code for failure:
221	*
222	* -ENOMEM FOLL_GET or FOLL_PIN was set, but the page could not
223	* be grabbed.
224	*/
225	int __must_check try_grab_page(struct page *page, unsigned int flags)
226	{
227	struct folio *folio = page_folio(page);
228
229	if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
230	return -ENOMEM;
231
232	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
233	return -EREMOTEIO;
234
235	if (flags & FOLL_GET)
236	folio_ref_inc(folio);
237	else if (flags & FOLL_PIN) {
238	/*
239	* Don't take a pin on the zero page - it's not going anywhere
240	* and it is used in a *lot* of places.
241	*/
242	if (is_zero_page(page))
243	return 0;
244
245	/*
246	* Similar to try_grab_folio(): be sure to *also*
247	* increment the normal page refcount field at least once,
248	* so that the page really is pinned.
249	*/
250	if (folio_test_large(folio)) {
251	folio_ref_add(folio, nr: 1);
252	atomic_add(i: 1, v: &folio->_pincount);
253	} else {
254	folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
255	}
256
257	node_stat_mod_folio(folio, item: NR_FOLL_PIN_ACQUIRED, nr: 1);
258	}
259
260	return 0;
261	}
262
263	/**
264	* unpin_user_page() - release a dma-pinned page
265	* @page: pointer to page to be released
266	*
267	* Pages that were pinned via pin_user_pages*() must be released via either
268	* unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
269	* that such pages can be separately tracked and uniquely handled. In
270	* particular, interactions with RDMA and filesystems need special handling.
271	*/
272	void unpin_user_page(struct page *page)
273	{
274	sanity_check_pinned_pages(pages: &page, npages: 1);
275	gup_put_folio(page_folio(page), refs: 1, flags: FOLL_PIN);
276	}
277	EXPORT_SYMBOL(unpin_user_page);
278
279	/**
280	* folio_add_pin - Try to get an additional pin on a pinned folio
281	* @folio: The folio to be pinned
282	*
283	* Get an additional pin on a folio we already have a pin on. Makes no change
284	* if the folio is a zero_page.
285	*/
286	void folio_add_pin(struct folio *folio)
287	{
288	if (is_zero_folio(folio))
289	return;
290
291	/*
292	* Similar to try_grab_folio(): be sure to *also* increment the normal
293	* page refcount field at least once, so that the page really is
294	* pinned.
295	*/
296	if (folio_test_large(folio)) {
297	WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1);
298	folio_ref_inc(folio);
299	atomic_inc(v: &folio->_pincount);
300	} else {
301	WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS);
302	folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
303	}
304	}
305
306	static inline struct folio *gup_folio_range_next(struct page *start,
307	unsigned long npages, unsigned long i, unsigned int *ntails)
308	{
309	struct page *next = nth_page(start, i);
310	struct folio *folio = page_folio(next);
311	unsigned int nr = 1;
312
313	if (folio_test_large(folio))
314	nr = min_t(unsigned int, npages - i,
315	folio_nr_pages(folio) - folio_page_idx(folio, next));
316
317	*ntails = nr;
318	return folio;
319	}
320
321	static inline struct folio *gup_folio_next(struct page **list,
322	unsigned long npages, unsigned long i, unsigned int *ntails)
323	{
324	struct folio *folio = page_folio(list[i]);
325	unsigned int nr;
326
327	for (nr = i + 1; nr < npages; nr++) {
328	if (page_folio(list[nr]) != folio)
329	break;
330	}
331
332	*ntails = nr - i;
333	return folio;
334	}
335
336	/**
337	* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
338	* @pages: array of pages to be maybe marked dirty, and definitely released.
339	* @npages: number of pages in the @pages array.
340	* @make_dirty: whether to mark the pages dirty
341	*
342	* "gup-pinned page" refers to a page that has had one of the get_user_pages()
343	* variants called on that page.
344	*
345	* For each page in the @pages array, make that page (or its head page, if a
346	* compound page) dirty, if @make_dirty is true, and if the page was previously
347	* listed as clean. In any case, releases all pages using unpin_user_page(),
348	* possibly via unpin_user_pages(), for the non-dirty case.
349	*
350	* Please see the unpin_user_page() documentation for details.
351	*
352	* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
353	* required, then the caller should a) verify that this is really correct,
354	* because _lock() is usually required, and b) hand code it:
355	* set_page_dirty_lock(), unpin_user_page().
356	*
357	*/
358	void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
359	bool make_dirty)
360	{
361	unsigned long i;
362	struct folio *folio;
363	unsigned int nr;
364
365	if (!make_dirty) {
366	unpin_user_pages(pages, npages);
367	return;
368	}
369
370	sanity_check_pinned_pages(pages, npages);
371	for (i = 0; i < npages; i += nr) {
372	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
373	/*
374	* Checking PageDirty at this point may race with
375	* clear_page_dirty_for_io(), but that's OK. Two key
376	* cases:
377	*
378	* 1) This code sees the page as already dirty, so it
379	* skips the call to set_page_dirty(). That could happen
380	* because clear_page_dirty_for_io() called
381	* page_mkclean(), followed by set_page_dirty().
382	* However, now the page is going to get written back,
383	* which meets the original intention of setting it
384	* dirty, so all is well: clear_page_dirty_for_io() goes
385	* on to call TestClearPageDirty(), and write the page
386	* back.
387	*
388	* 2) This code sees the page as clean, so it calls
389	* set_page_dirty(). The page stays dirty, despite being
390	* written back, so it gets written back again in the
391	* next writeback cycle. This is harmless.
392	*/
393	if (!folio_test_dirty(folio)) {
394	folio_lock(folio);
395	folio_mark_dirty(folio);
396	folio_unlock(folio);
397	}
398	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
399	}
400	}
401	EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
402
403	/**
404	* unpin_user_page_range_dirty_lock() - release and optionally dirty
405	* gup-pinned page range
406	*
407	* @page: the starting page of a range maybe marked dirty, and definitely released.
408	* @npages: number of consecutive pages to release.
409	* @make_dirty: whether to mark the pages dirty
410	*
411	* "gup-pinned page range" refers to a range of pages that has had one of the
412	* pin_user_pages() variants called on that page.
413	*
414	* For the page ranges defined by [page .. page+npages], make that range (or
415	* its head pages, if a compound page) dirty, if @make_dirty is true, and if the
416	* page range was previously listed as clean.
417	*
418	* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
419	* required, then the caller should a) verify that this is really correct,
420	* because _lock() is usually required, and b) hand code it:
421	* set_page_dirty_lock(), unpin_user_page().
422	*
423	*/
424	void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
425	bool make_dirty)
426	{
427	unsigned long i;
428	struct folio *folio;
429	unsigned int nr;
430
431	for (i = 0; i < npages; i += nr) {
432	folio = gup_folio_range_next(start: page, npages, i, ntails: &nr);
433	if (make_dirty && !folio_test_dirty(folio)) {
434	folio_lock(folio);
435	folio_mark_dirty(folio);
436	folio_unlock(folio);
437	}
438	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
439	}
440	}
441	EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
442
443	static void unpin_user_pages_lockless(struct page **pages, unsigned long npages)
444	{
445	unsigned long i;
446	struct folio *folio;
447	unsigned int nr;
448
449	/*
450	* Don't perform any sanity checks because we might have raced with
451	* fork() and some anonymous pages might now actually be shared --
452	* which is why we're unpinning after all.
453	*/
454	for (i = 0; i < npages; i += nr) {
455	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
456	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
457	}
458	}
459
460	/**
461	* unpin_user_pages() - release an array of gup-pinned pages.
462	* @pages: array of pages to be marked dirty and released.
463	* @npages: number of pages in the @pages array.
464	*
465	* For each page in the @pages array, release the page using unpin_user_page().
466	*
467	* Please see the unpin_user_page() documentation for details.
468	*/
469	void unpin_user_pages(struct page **pages, unsigned long npages)
470	{
471	unsigned long i;
472	struct folio *folio;
473	unsigned int nr;
474
475	/*
476	* If this WARN_ON() fires, then the system *might* be leaking pages (by
477	* leaving them pinned), but probably not. More likely, gup/pup returned
478	* a hard -ERRNO error to the caller, who erroneously passed it here.
479	*/
480	if (WARN_ON(IS_ERR_VALUE(npages)))
481	return;
482
483	sanity_check_pinned_pages(pages, npages);
484	for (i = 0; i < npages; i += nr) {
485	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
486	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
487	}
488	}
489	EXPORT_SYMBOL(unpin_user_pages);
490
491	/*
492	* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
493	* lifecycle. Avoid setting the bit unless necessary, or it might cause write
494	* cache bouncing on large SMP machines for concurrent pinned gups.
495	*/
496	static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
497	{
498	if (!test_bit(MMF_HAS_PINNED, mm_flags))
499	set_bit(MMF_HAS_PINNED, addr: mm_flags);
500	}
501
502	#ifdef CONFIG_MMU
503	static struct page *no_page_table(struct vm_area_struct *vma,
504	unsigned int flags)
505	{
506	/*
507	* When core dumping an enormous anonymous area that nobody
508	* has touched so far, we don't want to allocate unnecessary pages or
509	* page tables. Return error instead of NULL to skip handle_mm_fault,
510	* then get_dump_page() will return NULL to leave a hole in the dump.
511	* But we can only make this optimization where a hole would surely
512	* be zero-filled if handle_mm_fault() actually did handle it.
513	*/
514	if ((flags & FOLL_DUMP) &&
515	(vma_is_anonymous(vma) || !vma->vm_ops->fault))
516	return ERR_PTR(error: -EFAULT);
517	return NULL;
518	}
519
520	static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
521	pte_t *pte, unsigned int flags)
522	{
523	if (flags & FOLL_TOUCH) {
524	pte_t orig_entry = ptep_get(ptep: pte);
525	pte_t entry = orig_entry;
526
527	if (flags & FOLL_WRITE)
528	entry = pte_mkdirty(pte: entry);
529	entry = pte_mkyoung(pte: entry);
530
531	if (!pte_same(a: orig_entry, b: entry)) {
532	set_pte_at(vma->vm_mm, address, pte, entry);
533	update_mmu_cache(vma, addr: address, ptep: pte);
534	}
535	}
536
537	/* Proper page table entry exists, but no corresponding struct page */
538	return -EEXIST;
539	}
540
541	/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */
542	static inline bool can_follow_write_pte(pte_t pte, struct page *page,
543	struct vm_area_struct *vma,
544	unsigned int flags)
545	{
546	/* If the pte is writable, we can write to the page. */
547	if (pte_write(pte))
548	return true;
549
550	/* Maybe FOLL_FORCE is set to override it? */
551	if (!(flags & FOLL_FORCE))
552	return false;
553
554	/* But FOLL_FORCE has no effect on shared mappings */
555	if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
556	return false;
557
558	/* ... or read-only private ones */
559	if (!(vma->vm_flags & VM_MAYWRITE))
560	return false;
561
562	/* ... or already writable ones that just need to take a write fault */
563	if (vma->vm_flags & VM_WRITE)
564	return false;
565
566	/*
567	* See can_change_pte_writable(): we broke COW and could map the page
568	* writable if we have an exclusive anonymous page ...
569	*/
570	if (!page || !PageAnon(page) || !PageAnonExclusive(page))
571	return false;
572
573	/* ... and a write-fault isn't required for other reasons. */
574	if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
575	return false;
576	return !userfaultfd_pte_wp(vma, pte);
577	}
578
579	static struct page *follow_page_pte(struct vm_area_struct *vma,
580	unsigned long address, pmd_t *pmd, unsigned int flags,
581	struct dev_pagemap **pgmap)
582	{
583	struct mm_struct *mm = vma->vm_mm;
584	struct page *page;
585	spinlock_t *ptl;
586	pte_t *ptep, pte;
587	int ret;
588
589	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
590	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
591	(FOLL_PIN | FOLL_GET)))
592	return ERR_PTR(error: -EINVAL);
593
594	ptep = pte_offset_map_lock(mm, pmd, addr: address, ptlp: &ptl);
595	if (!ptep)
596	return no_page_table(vma, flags);
597	pte = ptep_get(ptep);
598	if (!pte_present(a: pte))
599	goto no_page;
600	if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags))
601	goto no_page;
602
603	page = vm_normal_page(vma, addr: address, pte);
604
605	/*
606	* We only care about anon pages in can_follow_write_pte() and don't
607	* have to worry about pte_devmap() because they are never anon.
608	*/
609	if ((flags & FOLL_WRITE) &&
610	!can_follow_write_pte(pte, page, vma, flags)) {
611	page = NULL;
612	goto out;
613	}
614
615	if (!page && pte_devmap(a: pte) && (flags & (FOLL_GET | FOLL_PIN))) {
616	/*
617	* Only return device mapping pages in the FOLL_GET or FOLL_PIN
618	* case since they are only valid while holding the pgmap
619	* reference.
620	*/
621	*pgmap = get_dev_pagemap(pfn: pte_pfn(pte), pgmap: *pgmap);
622	if (*pgmap)
623	page = pte_page(pte);
624	else
625	goto no_page;
626	} else if (unlikely(!page)) {
627	if (flags & FOLL_DUMP) {
628	/* Avoid special (like zero) pages in core dumps */
629	page = ERR_PTR(error: -EFAULT);
630	goto out;
631	}
632
633	if (is_zero_pfn(pfn: pte_pfn(pte))) {
634	page = pte_page(pte);
635	} else {
636	ret = follow_pfn_pte(vma, address, pte: ptep, flags);
637	page = ERR_PTR(error: ret);
638	goto out;
639	}
640	}
641
642	if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) {
643	page = ERR_PTR(error: -EMLINK);
644	goto out;
645	}
646
647	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
648	!PageAnonExclusive(page), page);
649
650	/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
651	ret = try_grab_page(page, flags);
652	if (unlikely(ret)) {
653	page = ERR_PTR(error: ret);
654	goto out;
655	}
656
657	/*
658	* We need to make the page accessible if and only if we are going
659	* to access its content (the FOLL_PIN case). Please see
660	* Documentation/core-api/pin_user_pages.rst for details.
661	*/
662	if (flags & FOLL_PIN) {
663	ret = arch_make_page_accessible(page);
664	if (ret) {
665	unpin_user_page(page);
666	page = ERR_PTR(error: ret);
667	goto out;
668	}
669	}
670	if (flags & FOLL_TOUCH) {
671	if ((flags & FOLL_WRITE) &&
672	!pte_dirty(pte) && !PageDirty(page))
673	set_page_dirty(page);
674	/*
675	* pte_mkyoung() would be more correct here, but atomic care
676	* is needed to avoid losing the dirty bit: it is easier to use
677	* mark_page_accessed().
678	*/
679	mark_page_accessed(page);
680	}
681	out:
682	pte_unmap_unlock(ptep, ptl);
683	return page;
684	no_page:
685	pte_unmap_unlock(ptep, ptl);
686	if (!pte_none(pte))
687	return NULL;
688	return no_page_table(vma, flags);
689	}
690
691	static struct page *follow_pmd_mask(struct vm_area_struct *vma,
692	unsigned long address, pud_t *pudp,
693	unsigned int flags,
694	struct follow_page_context *ctx)
695	{
696	pmd_t *pmd, pmdval;
697	spinlock_t *ptl;
698	struct page *page;
699	struct mm_struct *mm = vma->vm_mm;
700
701	pmd = pmd_offset(pud: pudp, address);
702	pmdval = pmdp_get_lockless(pmdp: pmd);
703	if (pmd_none(pmd: pmdval))
704	return no_page_table(vma, flags);
705	if (!pmd_present(pmd: pmdval))
706	return no_page_table(vma, flags);
707	if (pmd_devmap(pmd: pmdval)) {
708	ptl = pmd_lock(mm, pmd);
709	page = follow_devmap_pmd(vma, addr: address, pmd, flags, pgmap: &ctx->pgmap);
710	spin_unlock(lock: ptl);
711	if (page)
712	return page;
713	}
714	if (likely(!pmd_trans_huge(pmdval)))
715	return follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
716
717	if (pmd_protnone(pmd: pmdval) && !gup_can_follow_protnone(vma, flags))
718	return no_page_table(vma, flags);
719
720	ptl = pmd_lock(mm, pmd);
721	if (unlikely(!pmd_present(*pmd))) {
722	spin_unlock(lock: ptl);
723	return no_page_table(vma, flags);
724	}
725	if (unlikely(!pmd_trans_huge(*pmd))) {
726	spin_unlock(lock: ptl);
727	return follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
728	}
729	if (flags & FOLL_SPLIT_PMD) {
730	spin_unlock(lock: ptl);
731	split_huge_pmd(vma, pmd, address);
732	/* If pmd was left empty, stuff a page table in there quickly */
733	return pte_alloc(mm, pmd) ? ERR_PTR(error: -ENOMEM) :
734	follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
735	}
736	page = follow_trans_huge_pmd(vma, addr: address, pmd, flags);
737	spin_unlock(lock: ptl);
738	ctx->page_mask = HPAGE_PMD_NR - 1;
739	return page;
740	}
741
742	static struct page *follow_pud_mask(struct vm_area_struct *vma,
743	unsigned long address, p4d_t *p4dp,
744	unsigned int flags,
745	struct follow_page_context *ctx)
746	{
747	pud_t *pud;
748	spinlock_t *ptl;
749	struct page *page;
750	struct mm_struct *mm = vma->vm_mm;
751
752	pud = pud_offset(p4d: p4dp, address);
753	if (pud_none(pud: *pud))
754	return no_page_table(vma, flags);
755	if (pud_devmap(pud: *pud)) {
756	ptl = pud_lock(mm, pud);
757	page = follow_devmap_pud(vma, addr: address, pud, flags, pgmap: &ctx->pgmap);
758	spin_unlock(lock: ptl);
759	if (page)
760	return page;
761	}
762	if (unlikely(pud_bad(*pud)))
763	return no_page_table(vma, flags);
764
765	return follow_pmd_mask(vma, address, pudp: pud, flags, ctx);
766	}
767
768	static struct page *follow_p4d_mask(struct vm_area_struct *vma,
769	unsigned long address, pgd_t *pgdp,
770	unsigned int flags,
771	struct follow_page_context *ctx)
772	{
773	p4d_t *p4d;
774
775	p4d = p4d_offset(pgd: pgdp, address);
776	if (p4d_none(p4d: *p4d))
777	return no_page_table(vma, flags);
778	BUILD_BUG_ON(p4d_huge(*p4d));
779	if (unlikely(p4d_bad(*p4d)))
780	return no_page_table(vma, flags);
781
782	return follow_pud_mask(vma, address, p4dp: p4d, flags, ctx);
783	}
784
785	/**
786	* follow_page_mask - look up a page descriptor from a user-virtual address
787	* @vma: vm_area_struct mapping @address
788	* @address: virtual address to look up
789	* @flags: flags modifying lookup behaviour
790	* @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
791	* pointer to output page_mask
792	*
793	* @flags can have FOLL_ flags set, defined in <linux/mm.h>
794	*
795	* When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
796	* the device's dev_pagemap metadata to avoid repeating expensive lookups.
797	*
798	* When getting an anonymous page and the caller has to trigger unsharing
799	* of a shared anonymous page first, -EMLINK is returned. The caller should
800	* trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only
801	* relevant with FOLL_PIN and !FOLL_WRITE.
802	*
803	* On output, the @ctx->page_mask is set according to the size of the page.
804	*
805	* Return: the mapped (struct page *), %NULL if no mapping exists, or
806	* an error pointer if there is a mapping to something not represented
807	* by a page descriptor (see also vm_normal_page()).
808	*/
809	static struct page *follow_page_mask(struct vm_area_struct *vma,
810	unsigned long address, unsigned int flags,
811	struct follow_page_context *ctx)
812	{
813	pgd_t *pgd;
814	struct mm_struct *mm = vma->vm_mm;
815
816	ctx->page_mask = 0;
817
818	/*
819	* Call hugetlb_follow_page_mask for hugetlb vmas as it will use
820	* special hugetlb page table walking code. This eliminates the
821	* need to check for hugetlb entries in the general walking code.
822	*/
823	if (is_vm_hugetlb_page(vma))
824	return hugetlb_follow_page_mask(vma, address, flags,
825	page_mask: &ctx->page_mask);
826
827	pgd = pgd_offset(mm, address);
828
829	if (pgd_none(pgd: *pgd) || unlikely(pgd_bad(*pgd)))
830	return no_page_table(vma, flags);
831
832	return follow_p4d_mask(vma, address, pgdp: pgd, flags, ctx);
833	}
834
835	struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
836	unsigned int foll_flags)
837	{
838	struct follow_page_context ctx = { NULL };
839	struct page *page;
840
841	if (vma_is_secretmem(vma))
842	return NULL;
843
844	if (WARN_ON_ONCE(foll_flags & FOLL_PIN))
845	return NULL;
846
847	/*
848	* We never set FOLL_HONOR_NUMA_FAULT because callers don't expect
849	* to fail on PROT_NONE-mapped pages.
850	*/
851	page = follow_page_mask(vma, address, flags: foll_flags, ctx: &ctx);
852	if (ctx.pgmap)
853	put_dev_pagemap(pgmap: ctx.pgmap);
854	return page;
855	}
856
857	static int get_gate_page(struct mm_struct *mm, unsigned long address,
858	unsigned int gup_flags, struct vm_area_struct **vma,
859	struct page **page)
860	{
861	pgd_t *pgd;
862	p4d_t *p4d;
863	pud_t *pud;
864	pmd_t *pmd;
865	pte_t *pte;
866	pte_t entry;
867	int ret = -EFAULT;
868
869	/* user gate pages are read-only */
870	if (gup_flags & FOLL_WRITE)
871	return -EFAULT;
872	if (address > TASK_SIZE)
873	pgd = pgd_offset_k(address);
874	else
875	pgd = pgd_offset_gate(mm, address);
876	if (pgd_none(pgd: *pgd))
877	return -EFAULT;
878	p4d = p4d_offset(pgd, address);
879	if (p4d_none(p4d: *p4d))
880	return -EFAULT;
881	pud = pud_offset(p4d, address);
882	if (pud_none(pud: *pud))
883	return -EFAULT;
884	pmd = pmd_offset(pud, address);
885	if (!pmd_present(pmd: *pmd))
886	return -EFAULT;
887	pte = pte_offset_map(pmd, addr: address);
888	if (!pte)
889	return -EFAULT;
890	entry = ptep_get(ptep: pte);
891	if (pte_none(pte: entry))
892	goto unmap;
893	*vma = get_gate_vma(mm);
894	if (!page)
895	goto out;
896	*page = vm_normal_page(vma: *vma, addr: address, pte: entry);
897	if (!*page) {
898	if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pfn: pte_pfn(pte: entry)))
899	goto unmap;
900	*page = pte_page(entry);
901	}
902	ret = try_grab_page(page: *page, flags: gup_flags);
903	if (unlikely(ret))
904	goto unmap;
905	out:
906	ret = 0;
907	unmap:
908	pte_unmap(pte);
909	return ret;
910	}
911
912	/*
913	* mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not
914	* FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set
915	* to 0 and -EBUSY returned.
916	*/
917	static int faultin_page(struct vm_area_struct *vma,
918	unsigned long address, unsigned int *flags, bool unshare,
919	int *locked)
920	{
921	unsigned int fault_flags = 0;
922	vm_fault_t ret;
923
924	if (*flags & FOLL_NOFAULT)
925	return -EFAULT;
926	if (*flags & FOLL_WRITE)
927	fault_flags |= FAULT_FLAG_WRITE;
928	if (*flags & FOLL_REMOTE)
929	fault_flags |= FAULT_FLAG_REMOTE;
930	if (*flags & FOLL_UNLOCKABLE) {
931	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
932	/*
933	* FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set
934	* FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE.
935	* That's because some callers may not be prepared to
936	* handle early exits caused by non-fatal signals.
937	*/
938	if (*flags & FOLL_INTERRUPTIBLE)
939	fault_flags |= FAULT_FLAG_INTERRUPTIBLE;
940	}
941	if (*flags & FOLL_NOWAIT)
942	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
943	if (*flags & FOLL_TRIED) {
944	/*
945	* Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
946	* can co-exist
947	*/
948	fault_flags |= FAULT_FLAG_TRIED;
949	}
950	if (unshare) {
951	fault_flags |= FAULT_FLAG_UNSHARE;
952	/* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */
953	VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE);
954	}
955
956	ret = handle_mm_fault(vma, address, flags: fault_flags, NULL);
957
958	if (ret & VM_FAULT_COMPLETED) {
959	/*
960	* With FAULT_FLAG_RETRY_NOWAIT we'll never release the
961	* mmap lock in the page fault handler. Sanity check this.
962	*/
963	WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
964	*locked = 0;
965
966	/*
967	* We should do the same as VM_FAULT_RETRY, but let's not
968	* return -EBUSY since that's not reflecting the reality of
969	* what has happened - we've just fully completed a page
970	* fault, with the mmap lock released. Use -EAGAIN to show
971	* that we want to take the mmap lock _again_.
972	*/
973	return -EAGAIN;
974	}
975
976	if (ret & VM_FAULT_ERROR) {
977	int err = vm_fault_to_errno(vm_fault: ret, foll_flags: *flags);
978
979	if (err)
980	return err;
981	BUG();
982	}
983
984	if (ret & VM_FAULT_RETRY) {
985	if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
986	*locked = 0;
987	return -EBUSY;
988	}
989
990	return 0;
991	}
992
993	/*
994	* Writing to file-backed mappings which require folio dirty tracking using GUP
995	* is a fundamentally broken operation, as kernel write access to GUP mappings
996	* do not adhere to the semantics expected by a file system.
997	*
998	* Consider the following scenario:-
999	*
1000	* 1. A folio is written to via GUP which write-faults the memory, notifying
1001	* the file system and dirtying the folio.
1002	* 2. Later, writeback is triggered, resulting in the folio being cleaned and
1003	* the PTE being marked read-only.
1004	* 3. The GUP caller writes to the folio, as it is mapped read/write via the
1005	* direct mapping.
1006	* 4. The GUP caller, now done with the page, unpins it and sets it dirty
1007	* (though it does not have to).
1008	*
1009	* This results in both data being written to a folio without writenotify, and
1010	* the folio being dirtied unexpectedly (if the caller decides to do so).
1011	*/
1012	static bool writable_file_mapping_allowed(struct vm_area_struct *vma,
1013	unsigned long gup_flags)
1014	{
1015	/*
1016	* If we aren't pinning then no problematic write can occur. A long term
1017	* pin is the most egregious case so this is the case we disallow.
1018	*/
1019	if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) !=
1020	(FOLL_PIN | FOLL_LONGTERM))
1021	return true;
1022
1023	/*
1024	* If the VMA does not require dirty tracking then no problematic write
1025	* can occur either.
1026	*/
1027	return !vma_needs_dirty_tracking(vma);
1028	}
1029
1030	static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
1031	{
1032	vm_flags_t vm_flags = vma->vm_flags;
1033	int write = (gup_flags & FOLL_WRITE);
1034	int foreign = (gup_flags & FOLL_REMOTE);
1035	bool vma_anon = vma_is_anonymous(vma);
1036
1037	if (vm_flags & (VM_IO | VM_PFNMAP))
1038	return -EFAULT;
1039
1040	if ((gup_flags & FOLL_ANON) && !vma_anon)
1041	return -EFAULT;
1042
1043	if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
1044	return -EOPNOTSUPP;
1045
1046	if (vma_is_secretmem(vma))
1047	return -EFAULT;
1048
1049	if (write) {
1050	if (!vma_anon &&
1051	!writable_file_mapping_allowed(vma, gup_flags))
1052	return -EFAULT;
1053
1054	if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
1055	if (!(gup_flags & FOLL_FORCE))
1056	return -EFAULT;
1057	/* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */
1058	if (is_vm_hugetlb_page(vma))
1059	return -EFAULT;
1060	/*
1061	* We used to let the write,force case do COW in a
1062	* VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
1063	* set a breakpoint in a read-only mapping of an
1064	* executable, without corrupting the file (yet only
1065	* when that file had been opened for writing!).
1066	* Anon pages in shared mappings are surprising: now
1067	* just reject it.
1068	*/
1069	if (!is_cow_mapping(flags: vm_flags))
1070	return -EFAULT;
1071	}
1072	} else if (!(vm_flags & VM_READ)) {
1073	if (!(gup_flags & FOLL_FORCE))
1074	return -EFAULT;
1075	/*
1076	* Is there actually any vma we can reach here which does not
1077	* have VM_MAYREAD set?
1078	*/
1079	if (!(vm_flags & VM_MAYREAD))
1080	return -EFAULT;
1081	}
1082	/*
1083	* gups are always data accesses, not instruction
1084	* fetches, so execute=false here
1085	*/
1086	if (!arch_vma_access_permitted(vma, write, execute: false, foreign))
1087	return -EFAULT;
1088	return 0;
1089	}
1090
1091	/*
1092	* This is "vma_lookup()", but with a warning if we would have
1093	* historically expanded the stack in the GUP code.
1094	*/
1095	static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm,
1096	unsigned long addr)
1097	{
1098	#ifdef CONFIG_STACK_GROWSUP
1099	return vma_lookup(mm, addr);
1100	#else
1101	static volatile unsigned long next_warn;
1102	struct vm_area_struct *vma;
1103	unsigned long now, next;
1104
1105	vma = find_vma(mm, addr);
1106	if (!vma || (addr >= vma->vm_start))
1107	return vma;
1108
1109	/* Only warn for half-way relevant accesses */
1110	if (!(vma->vm_flags & VM_GROWSDOWN))
1111	return NULL;
1112	if (vma->vm_start - addr > 65536)
1113	return NULL;
1114
1115	/* Let's not warn more than once an hour.. */
1116	now = jiffies; next = next_warn;
1117	if (next && time_before(now, next))
1118	return NULL;
1119	next_warn = now + 60*60*HZ;
1120
1121	/* Let people know things may have changed. */
1122	pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n",
1123	current->comm, task_pid_nr(current),
1124	vma->vm_start, vma->vm_end, addr);
1125	dump_stack();
1126	return NULL;
1127	#endif
1128	}
1129
1130	/**
1131	* __get_user_pages() - pin user pages in memory
1132	* @mm: mm_struct of target mm
1133	* @start: starting user address
1134	* @nr_pages: number of pages from start to pin
1135	* @gup_flags: flags modifying pin behaviour
1136	* @pages: array that receives pointers to the pages pinned.
1137	* Should be at least nr_pages long. Or NULL, if caller
1138	* only intends to ensure the pages are faulted in.
1139	* @locked: whether we're still with the mmap_lock held
1140	*
1141	* Returns either number of pages pinned (which may be less than the
1142	* number requested), or an error. Details about the return value:
1143	*
1144	* -- If nr_pages is 0, returns 0.
1145	* -- If nr_pages is >0, but no pages were pinned, returns -errno.
1146	* -- If nr_pages is >0, and some pages were pinned, returns the number of
1147	* pages pinned. Again, this may be less than nr_pages.
1148	* -- 0 return value is possible when the fault would need to be retried.
1149	*
1150	* The caller is responsible for releasing returned @pages, via put_page().
1151	*
1152	* Must be called with mmap_lock held. It may be released. See below.
1153	*
1154	* __get_user_pages walks a process's page tables and takes a reference to
1155	* each struct page that each user address corresponds to at a given
1156	* instant. That is, it takes the page that would be accessed if a user
1157	* thread accesses the given user virtual address at that instant.
1158	*
1159	* This does not guarantee that the page exists in the user mappings when
1160	* __get_user_pages returns, and there may even be a completely different
1161	* page there in some cases (eg. if mmapped pagecache has been invalidated
1162	* and subsequently re-faulted). However it does guarantee that the page
1163	* won't be freed completely. And mostly callers simply care that the page
1164	* contains data that was valid *at some point in time*. Typically, an IO
1165	* or similar operation cannot guarantee anything stronger anyway because
1166	* locks can't be held over the syscall boundary.
1167	*
1168	* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1169	* the page is written to, set_page_dirty (or set_page_dirty_lock, as
1170	* appropriate) must be called after the page is finished with, and
1171	* before put_page is called.
1172	*
1173	* If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may
1174	* be released. If this happens *@locked will be set to 0 on return.
1175	*
1176	* A caller using such a combination of @gup_flags must therefore hold the
1177	* mmap_lock for reading only, and recognize when it's been released. Otherwise,
1178	* it must be held for either reading or writing and will not be released.
1179	*
1180	* In most cases, get_user_pages or get_user_pages_fast should be used
1181	* instead of __get_user_pages. __get_user_pages should be used only if
1182	* you need some special @gup_flags.
1183	*/
1184	static long __get_user_pages(struct mm_struct *mm,
1185	unsigned long start, unsigned long nr_pages,
1186	unsigned int gup_flags, struct page **pages,
1187	int *locked)
1188	{
1189	long ret = 0, i = 0;
1190	struct vm_area_struct *vma = NULL;
1191	struct follow_page_context ctx = { NULL };
1192
1193	if (!nr_pages)
1194	return 0;
1195
1196	start = untagged_addr_remote(mm, start);
1197
1198	VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1199
1200	do {
1201	struct page *page;
1202	unsigned int foll_flags = gup_flags;
1203	unsigned int page_increm;
1204
1205	/* first iteration or cross vma bound */
1206	if (!vma || start >= vma->vm_end) {
1207	vma = gup_vma_lookup(mm, addr: start);
1208	if (!vma && in_gate_area(mm, addr: start)) {
1209	ret = get_gate_page(mm, address: start & PAGE_MASK,
1210	gup_flags, vma: &vma,
1211	page: pages ? &page : NULL);
1212	if (ret)
1213	goto out;
1214	ctx.page_mask = 0;
1215	goto next_page;
1216	}
1217
1218	if (!vma) {
1219	ret = -EFAULT;
1220	goto out;
1221	}
1222	ret = check_vma_flags(vma, gup_flags);
1223	if (ret)
1224	goto out;
1225	}
1226	retry:
1227	/*
1228	* If we have a pending SIGKILL, don't keep faulting pages and
1229	* potentially allocating memory.
1230	*/
1231	if (fatal_signal_pending(current)) {
1232	ret = -EINTR;
1233	goto out;
1234	}
1235	cond_resched();
1236
1237	page = follow_page_mask(vma, address: start, flags: foll_flags, ctx: &ctx);
1238	if (!page || PTR_ERR(ptr: page) == -EMLINK) {
1239	ret = faultin_page(vma, address: start, flags: &foll_flags,
1240	unshare: PTR_ERR(ptr: page) == -EMLINK, locked);
1241	switch (ret) {
1242	case 0:
1243	goto retry;
1244	case -EBUSY:
1245	case -EAGAIN:
1246	ret = 0;
1247	fallthrough;
1248	case -EFAULT:
1249	case -ENOMEM:
1250	case -EHWPOISON:
1251	goto out;
1252	}
1253	BUG();
1254	} else if (PTR_ERR(ptr: page) == -EEXIST) {
1255	/*
1256	* Proper page table entry exists, but no corresponding
1257	* struct page. If the caller expects **pages to be
1258	* filled in, bail out now, because that can't be done
1259	* for this page.
1260	*/
1261	if (pages) {
1262	ret = PTR_ERR(ptr: page);
1263	goto out;
1264	}
1265	} else if (IS_ERR(ptr: page)) {
1266	ret = PTR_ERR(ptr: page);
1267	goto out;
1268	}
1269	next_page:
1270	page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1271	if (page_increm > nr_pages)
1272	page_increm = nr_pages;
1273
1274	if (pages) {
1275	struct page *subpage;
1276	unsigned int j;
1277
1278	/*
1279	* This must be a large folio (and doesn't need to
1280	* be the whole folio; it can be part of it), do
1281	* the refcount work for all the subpages too.
1282	*
1283	* NOTE: here the page may not be the head page
1284	* e.g. when start addr is not thp-size aligned.
1285	* try_grab_folio() should have taken care of tail
1286	* pages.
1287	*/
1288	if (page_increm > 1) {
1289	struct folio *folio;
1290
1291	/*
1292	* Since we already hold refcount on the
1293	* large folio, this should never fail.
1294	*/
1295	folio = try_grab_folio(page, refs: page_increm - 1,
1296	flags: foll_flags);
1297	if (WARN_ON_ONCE(!folio)) {
1298	/*
1299	* Release the 1st page ref if the
1300	* folio is problematic, fail hard.
1301	*/
1302	gup_put_folio(page_folio(page), refs: 1,
1303	flags: foll_flags);
1304	ret = -EFAULT;
1305	goto out;
1306	}
1307	}
1308
1309	for (j = 0; j < page_increm; j++) {
1310	subpage = nth_page(page, j);
1311	pages[i + j] = subpage;
1312	flush_anon_page(vma, page: subpage, vmaddr: start + j * PAGE_SIZE);
1313	flush_dcache_page(page: subpage);
1314	}
1315	}
1316
1317	i += page_increm;
1318	start += page_increm * PAGE_SIZE;
1319	nr_pages -= page_increm;
1320	} while (nr_pages);
1321	out:
1322	if (ctx.pgmap)
1323	put_dev_pagemap(pgmap: ctx.pgmap);
1324	return i ? i : ret;
1325	}
1326
1327	static bool vma_permits_fault(struct vm_area_struct *vma,
1328	unsigned int fault_flags)
1329	{
1330	bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1331	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1332	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1333
1334	if (!(vm_flags & vma->vm_flags))
1335	return false;
1336
1337	/*
1338	* The architecture might have a hardware protection
1339	* mechanism other than read/write that can deny access.
1340	*
1341	* gup always represents data access, not instruction
1342	* fetches, so execute=false here:
1343	*/
1344	if (!arch_vma_access_permitted(vma, write, execute: false, foreign))
1345	return false;
1346
1347	return true;
1348	}
1349
1350	/**
1351	* fixup_user_fault() - manually resolve a user page fault
1352	* @mm: mm_struct of target mm
1353	* @address: user address
1354	* @fault_flags:flags to pass down to handle_mm_fault()
1355	* @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller
1356	* does not allow retry. If NULL, the caller must guarantee
1357	* that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
1358	*
1359	* This is meant to be called in the specific scenario where for locking reasons
1360	* we try to access user memory in atomic context (within a pagefault_disable()
1361	* section), this returns -EFAULT, and we want to resolve the user fault before
1362	* trying again.
1363	*
1364	* Typically this is meant to be used by the futex code.
1365	*
1366	* The main difference with get_user_pages() is that this function will
1367	* unconditionally call handle_mm_fault() which will in turn perform all the
1368	* necessary SW fixup of the dirty and young bits in the PTE, while
1369	* get_user_pages() only guarantees to update these in the struct page.
1370	*
1371	* This is important for some architectures where those bits also gate the
1372	* access permission to the page because they are maintained in software. On
1373	* such architectures, gup() will not be enough to make a subsequent access
1374	* succeed.
1375	*
1376	* This function will not return with an unlocked mmap_lock. So it has not the
1377	* same semantics wrt the @mm->mmap_lock as does filemap_fault().
1378	*/
1379	int fixup_user_fault(struct mm_struct *mm,
1380	unsigned long address, unsigned int fault_flags,
1381	bool *unlocked)
1382	{
1383	struct vm_area_struct *vma;
1384	vm_fault_t ret;
1385
1386	address = untagged_addr_remote(mm, address);
1387
1388	if (unlocked)
1389	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1390
1391	retry:
1392	vma = gup_vma_lookup(mm, addr: address);
1393	if (!vma)
1394	return -EFAULT;
1395
1396	if (!vma_permits_fault(vma, fault_flags))
1397	return -EFAULT;
1398
1399	if ((fault_flags & FAULT_FLAG_KILLABLE) &&
1400	fatal_signal_pending(current))
1401	return -EINTR;
1402
1403	ret = handle_mm_fault(vma, address, flags: fault_flags, NULL);
1404
1405	if (ret & VM_FAULT_COMPLETED) {
1406	/*
1407	* NOTE: it's a pity that we need to retake the lock here
1408	* to pair with the unlock() in the callers. Ideally we
1409	* could tell the callers so they do not need to unlock.
1410	*/
1411	mmap_read_lock(mm);
1412	*unlocked = true;
1413	return 0;
1414	}
1415
1416	if (ret & VM_FAULT_ERROR) {
1417	int err = vm_fault_to_errno(vm_fault: ret, foll_flags: 0);
1418
1419	if (err)
1420	return err;
1421	BUG();
1422	}
1423
1424	if (ret & VM_FAULT_RETRY) {
1425	mmap_read_lock(mm);
1426	*unlocked = true;
1427	fault_flags |= FAULT_FLAG_TRIED;
1428	goto retry;
1429	}
1430
1431	return 0;
1432	}
1433	EXPORT_SYMBOL_GPL(fixup_user_fault);
1434
1435	/*
1436	* GUP always responds to fatal signals. When FOLL_INTERRUPTIBLE is
1437	* specified, it'll also respond to generic signals. The caller of GUP
1438	* that has FOLL_INTERRUPTIBLE should take care of the GUP interruption.
1439	*/
1440	static bool gup_signal_pending(unsigned int flags)
1441	{
1442	if (fatal_signal_pending(current))
1443	return true;
1444
1445	if (!(flags & FOLL_INTERRUPTIBLE))
1446	return false;
1447
1448	return signal_pending(current);
1449	}
1450
1451	/*
1452	* Locking: (*locked == 1) means that the mmap_lock has already been acquired by
1453	* the caller. This function may drop the mmap_lock. If it does so, then it will
1454	* set (*locked = 0).
1455	*
1456	* (*locked == 0) means that the caller expects this function to acquire and
1457	* drop the mmap_lock. Therefore, the value of *locked will still be zero when
1458	* the function returns, even though it may have changed temporarily during
1459	* function execution.
1460	*
1461	* Please note that this function, unlike __get_user_pages(), will not return 0
1462	* for nr_pages > 0, unless FOLL_NOWAIT is used.
1463	*/
1464	static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
1465	unsigned long start,
1466	unsigned long nr_pages,
1467	struct page **pages,
1468	int *locked,
1469	unsigned int flags)
1470	{
1471	long ret, pages_done;
1472	bool must_unlock = false;
1473
1474	if (!nr_pages)
1475	return 0;
1476
1477	/*
1478	* The internal caller expects GUP to manage the lock internally and the
1479	* lock must be released when this returns.
1480	*/
1481	if (!*locked) {
1482	if (mmap_read_lock_killable(mm))
1483	return -EAGAIN;
1484	must_unlock = true;
1485	*locked = 1;
1486	}
1487	else
1488	mmap_assert_locked(mm);
1489
1490	if (flags & FOLL_PIN)
1491	mm_set_has_pinned_flag(mm_flags: &mm->flags);
1492
1493	/*
1494	* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1495	* is to set FOLL_GET if the caller wants pages[] filled in (but has
1496	* carelessly failed to specify FOLL_GET), so keep doing that, but only
1497	* for FOLL_GET, not for the newer FOLL_PIN.
1498	*
1499	* FOLL_PIN always expects pages to be non-null, but no need to assert
1500	* that here, as any failures will be obvious enough.
1501	*/
1502	if (pages && !(flags & FOLL_PIN))
1503	flags |= FOLL_GET;
1504
1505	pages_done = 0;
1506	for (;;) {
1507	ret = __get_user_pages(mm, start, nr_pages, gup_flags: flags, pages,
1508	locked);
1509	if (!(flags & FOLL_UNLOCKABLE)) {
1510	/* VM_FAULT_RETRY couldn't trigger, bypass */
1511	pages_done = ret;
1512	break;
1513	}
1514
1515	/* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */
1516	if (!*locked) {
1517	BUG_ON(ret < 0);
1518	BUG_ON(ret >= nr_pages);
1519	}
1520
1521	if (ret > 0) {
1522	nr_pages -= ret;
1523	pages_done += ret;
1524	if (!nr_pages)
1525	break;
1526	}
1527	if (*locked) {
1528	/*
1529	* VM_FAULT_RETRY didn't trigger or it was a
1530	* FOLL_NOWAIT.
1531	*/
1532	if (!pages_done)
1533	pages_done = ret;
1534	break;
1535	}
1536	/*
1537	* VM_FAULT_RETRY triggered, so seek to the faulting offset.
1538	* For the prefault case (!pages) we only update counts.
1539	*/
1540	if (likely(pages))
1541	pages += ret;
1542	start += ret << PAGE_SHIFT;
1543
1544	/* The lock was temporarily dropped, so we must unlock later */
1545	must_unlock = true;
1546
1547	retry:
1548	/*
1549	* Repeat on the address that fired VM_FAULT_RETRY
1550	* with both FAULT_FLAG_ALLOW_RETRY and
1551	* FAULT_FLAG_TRIED. Note that GUP can be interrupted
1552	* by fatal signals of even common signals, depending on
1553	* the caller's request. So we need to check it before we
1554	* start trying again otherwise it can loop forever.
1555	*/
1556	if (gup_signal_pending(flags)) {
1557	if (!pages_done)
1558	pages_done = -EINTR;
1559	break;
1560	}
1561
1562	ret = mmap_read_lock_killable(mm);
1563	if (ret) {
1564	BUG_ON(ret > 0);
1565	if (!pages_done)
1566	pages_done = ret;
1567	break;
1568	}
1569
1570	*locked = 1;
1571	ret = __get_user_pages(mm, start, nr_pages: 1, gup_flags: flags | FOLL_TRIED,
1572	pages, locked);
1573	if (!*locked) {
1574	/* Continue to retry until we succeeded */
1575	BUG_ON(ret != 0);
1576	goto retry;
1577	}
1578	if (ret != 1) {
1579	BUG_ON(ret > 1);
1580	if (!pages_done)
1581	pages_done = ret;
1582	break;
1583	}
1584	nr_pages--;
1585	pages_done++;
1586	if (!nr_pages)
1587	break;
1588	if (likely(pages))
1589	pages++;
1590	start += PAGE_SIZE;
1591	}
1592	if (must_unlock && *locked) {
1593	/*
1594	* We either temporarily dropped the lock, or the caller
1595	* requested that we both acquire and drop the lock. Either way,
1596	* we must now unlock, and notify the caller of that state.
1597	*/
1598	mmap_read_unlock(mm);
1599	*locked = 0;
1600	}
1601
1602	/*
1603	* Failing to pin anything implies something has gone wrong (except when
1604	* FOLL_NOWAIT is specified).
1605	*/
1606	if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
1607	return -EFAULT;
1608
1609	return pages_done;
1610	}
1611
1612	/**
1613	* populate_vma_page_range() - populate a range of pages in the vma.
1614	* @vma: target vma
1615	* @start: start address
1616	* @end: end address
1617	* @locked: whether the mmap_lock is still held
1618	*
1619	* This takes care of mlocking the pages too if VM_LOCKED is set.
1620	*
1621	* Return either number of pages pinned in the vma, or a negative error
1622	* code on error.
1623	*
1624	* vma->vm_mm->mmap_lock must be held.
1625	*
1626	* If @locked is NULL, it may be held for read or write and will
1627	* be unperturbed.
1628	*
1629	* If @locked is non-NULL, it must held for read only and may be
1630	* released. If it's released, *@locked will be set to 0.
1631	*/
1632	long populate_vma_page_range(struct vm_area_struct *vma,
1633	unsigned long start, unsigned long end, int *locked)
1634	{
1635	struct mm_struct *mm = vma->vm_mm;
1636	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1637	int local_locked = 1;
1638	int gup_flags;
1639	long ret;
1640
1641	VM_BUG_ON(!PAGE_ALIGNED(start));
1642	VM_BUG_ON(!PAGE_ALIGNED(end));
1643	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1644	VM_BUG_ON_VMA(end > vma->vm_end, vma);
1645	mmap_assert_locked(mm);
1646
1647	/*
1648	* Rightly or wrongly, the VM_LOCKONFAULT case has never used
1649	* faultin_page() to break COW, so it has no work to do here.
1650	*/
1651	if (vma->vm_flags & VM_LOCKONFAULT)
1652	return nr_pages;
1653
1654	gup_flags = FOLL_TOUCH;
1655	/*
1656	* We want to touch writable mappings with a write fault in order
1657	* to break COW, except for shared mappings because these don't COW
1658	* and we would not want to dirty them for nothing.
1659	*/
1660	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1661	gup_flags |= FOLL_WRITE;
1662
1663	/*
1664	* We want mlock to succeed for regions that have any permissions
1665	* other than PROT_NONE.
1666	*/
1667	if (vma_is_accessible(vma))
1668	gup_flags |= FOLL_FORCE;
1669
1670	if (locked)
1671	gup_flags |= FOLL_UNLOCKABLE;
1672
1673	/*
1674	* We made sure addr is within a VMA, so the following will
1675	* not result in a stack expansion that recurses back here.
1676	*/
1677	ret = __get_user_pages(mm, start, nr_pages, gup_flags,
1678	NULL, locked: locked ? locked : &local_locked);
1679	lru_add_drain();
1680	return ret;
1681	}
1682
1683	/*
1684	* faultin_vma_page_range() - populate (prefault) page tables inside the
1685	* given VMA range readable/writable
1686	*
1687	* This takes care of mlocking the pages, too, if VM_LOCKED is set.
1688	*
1689	* @vma: target vma
1690	* @start: start address
1691	* @end: end address
1692	* @write: whether to prefault readable or writable
1693	* @locked: whether the mmap_lock is still held
1694	*
1695	* Returns either number of processed pages in the vma, or a negative error
1696	* code on error (see __get_user_pages()).
1697	*
1698	* vma->vm_mm->mmap_lock must be held. The range must be page-aligned and
1699	* covered by the VMA. If it's released, *@locked will be set to 0.
1700	*/
1701	long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
1702	unsigned long end, bool write, int *locked)
1703	{
1704	struct mm_struct *mm = vma->vm_mm;
1705	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1706	int gup_flags;
1707	long ret;
1708
1709	VM_BUG_ON(!PAGE_ALIGNED(start));
1710	VM_BUG_ON(!PAGE_ALIGNED(end));
1711	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1712	VM_BUG_ON_VMA(end > vma->vm_end, vma);
1713	mmap_assert_locked(mm);
1714
1715	/*
1716	* FOLL_TOUCH: Mark page accessed and thereby young; will also mark
1717	* the page dirty with FOLL_WRITE -- which doesn't make a
1718	* difference with !FOLL_FORCE, because the page is writable
1719	* in the page table.
1720	* FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
1721	* a poisoned page.
1722	* !FOLL_FORCE: Require proper access permissions.
1723	*/
1724	gup_flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_UNLOCKABLE;
1725	if (write)
1726	gup_flags |= FOLL_WRITE;
1727
1728	/*
1729	* We want to report -EINVAL instead of -EFAULT for any permission
1730	* problems or incompatible mappings.
1731	*/
1732	if (check_vma_flags(vma, gup_flags))
1733	return -EINVAL;
1734
1735	ret = __get_user_pages(mm, start, nr_pages, gup_flags,
1736	NULL, locked);
1737	lru_add_drain();
1738	return ret;
1739	}
1740
1741	/*
1742	* __mm_populate - populate and/or mlock pages within a range of address space.
1743	*
1744	* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1745	* flags. VMAs must be already marked with the desired vm_flags, and
1746	* mmap_lock must not be held.
1747	*/
1748	int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1749	{
1750	struct mm_struct *mm = current->mm;
1751	unsigned long end, nstart, nend;
1752	struct vm_area_struct *vma = NULL;
1753	int locked = 0;
1754	long ret = 0;
1755
1756	end = start + len;
1757
1758	for (nstart = start; nstart < end; nstart = nend) {
1759	/*
1760	* We want to fault in pages for [nstart; end) address range.
1761	* Find first corresponding VMA.
1762	*/
1763	if (!locked) {
1764	locked = 1;
1765	mmap_read_lock(mm);
1766	vma = find_vma_intersection(mm, start_addr: nstart, end_addr: end);
1767	} else if (nstart >= vma->vm_end)
1768	vma = find_vma_intersection(mm, start_addr: vma->vm_end, end_addr: end);
1769
1770	if (!vma)
1771	break;
1772	/*
1773	* Set [nstart; nend) to intersection of desired address
1774	* range with the first VMA. Also, skip undesirable VMA types.
1775	*/
1776	nend = min(end, vma->vm_end);
1777	if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1778	continue;
1779	if (nstart < vma->vm_start)
1780	nstart = vma->vm_start;
1781	/*
1782	* Now fault in a range of pages. populate_vma_page_range()
1783	* double checks the vma flags, so that it won't mlock pages
1784	* if the vma was already munlocked.
1785	*/
1786	ret = populate_vma_page_range(vma, start: nstart, end: nend, locked: &locked);
1787	if (ret < 0) {
1788	if (ignore_errors) {
1789	ret = 0;
1790	continue; /* continue at next VMA */
1791	}
1792	break;
1793	}
1794	nend = nstart + ret * PAGE_SIZE;
1795	ret = 0;
1796	}
1797	if (locked)
1798	mmap_read_unlock(mm);
1799	return ret; /* 0 or negative error code */
1800	}
1801	#else /* CONFIG_MMU */
1802	static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
1803	unsigned long nr_pages, struct page **pages,
1804	int *locked, unsigned int foll_flags)
1805	{
1806	struct vm_area_struct *vma;
1807	bool must_unlock = false;
1808	unsigned long vm_flags;
1809	long i;
1810
1811	if (!nr_pages)
1812	return 0;
1813
1814	/*
1815	* The internal caller expects GUP to manage the lock internally and the
1816	* lock must be released when this returns.
1817	*/
1818	if (!*locked) {
1819	if (mmap_read_lock_killable(mm))
1820	return -EAGAIN;
1821	must_unlock = true;
1822	*locked = 1;
1823	}
1824
1825	/* calculate required read or write permissions.
1826	* If FOLL_FORCE is set, we only require the "MAY" flags.
1827	*/
1828	vm_flags = (foll_flags & FOLL_WRITE) ?
1829	(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1830	vm_flags &= (foll_flags & FOLL_FORCE) ?
1831	(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1832
1833	for (i = 0; i < nr_pages; i++) {
1834	vma = find_vma(mm, start);
1835	if (!vma)
1836	break;
1837
1838	/* protect what we can, including chardevs */
1839	if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1840	!(vm_flags & vma->vm_flags))
1841	break;
1842
1843	if (pages) {
1844	pages[i] = virt_to_page((void *)start);
1845	if (pages[i])
1846	get_page(pages[i]);
1847	}
1848
1849	start = (start + PAGE_SIZE) & PAGE_MASK;
1850	}
1851
1852	if (must_unlock && *locked) {
1853	mmap_read_unlock(mm);
1854	*locked = 0;
1855	}
1856
1857	return i ? : -EFAULT;
1858	}
1859	#endif /* !CONFIG_MMU */
1860
1861	/**
1862	* fault_in_writeable - fault in userspace address range for writing
1863	* @uaddr: start of address range
1864	* @size: size of address range
1865	*
1866	* Returns the number of bytes not faulted in (like copy_to_user() and
1867	* copy_from_user()).
1868	*/
1869	size_t fault_in_writeable(char __user *uaddr, size_t size)
1870	{
1871	char __user *start = uaddr, *end;
1872
1873	if (unlikely(size == 0))
1874	return 0;
1875	if (!user_write_access_begin(uaddr, size))
1876	return size;
1877	if (!PAGE_ALIGNED(uaddr)) {
1878	unsafe_put_user(0, uaddr, out);
1879	uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
1880	}
1881	end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
1882	if (unlikely(end < start))
1883	end = NULL;
1884	while (uaddr != end) {
1885	unsafe_put_user(0, uaddr, out);
1886	uaddr += PAGE_SIZE;
1887	}
1888
1889	out:
1890	user_write_access_end();
1891	if (size > uaddr - start)
1892	return size - (uaddr - start);
1893	return 0;
1894	}
1895	EXPORT_SYMBOL(fault_in_writeable);
1896
1897	/**
1898	* fault_in_subpage_writeable - fault in an address range for writing
1899	* @uaddr: start of address range
1900	* @size: size of address range
1901	*
1902	* Fault in a user address range for writing while checking for permissions at
1903	* sub-page granularity (e.g. arm64 MTE). This function should be used when
1904	* the caller cannot guarantee forward progress of a copy_to_user() loop.
1905	*
1906	* Returns the number of bytes not faulted in (like copy_to_user() and
1907	* copy_from_user()).
1908	*/
1909	size_t fault_in_subpage_writeable(char __user *uaddr, size_t size)
1910	{
1911	size_t faulted_in;
1912
1913	/*
1914	* Attempt faulting in at page granularity first for page table
1915	* permission checking. The arch-specific probe_subpage_writeable()
1916	* functions may not check for this.
1917	*/
1918	faulted_in = size - fault_in_writeable(uaddr, size);
1919	if (faulted_in)
1920	faulted_in -= probe_subpage_writeable(uaddr, size: faulted_in);
1921
1922	return size - faulted_in;
1923	}
1924	EXPORT_SYMBOL(fault_in_subpage_writeable);
1925
1926	/*
1927	* fault_in_safe_writeable - fault in an address range for writing
1928	* @uaddr: start of address range
1929	* @size: length of address range
1930	*
1931	* Faults in an address range for writing. This is primarily useful when we
1932	* already know that some or all of the pages in the address range aren't in
1933	* memory.
1934	*
1935	* Unlike fault_in_writeable(), this function is non-destructive.
1936	*
1937	* Note that we don't pin or otherwise hold the pages referenced that we fault
1938	* in. There's no guarantee that they'll stay in memory for any duration of
1939	* time.
1940	*
1941	* Returns the number of bytes not faulted in, like copy_to_user() and
1942	* copy_from_user().
1943	*/
1944	size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
1945	{
1946	unsigned long start = (unsigned long)uaddr, end;
1947	struct mm_struct *mm = current->mm;
1948	bool unlocked = false;
1949
1950	if (unlikely(size == 0))
1951	return 0;
1952	end = PAGE_ALIGN(start + size);
1953	if (end < start)
1954	end = 0;
1955
1956	mmap_read_lock(mm);
1957	do {
1958	if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
1959	break;
1960	start = (start + PAGE_SIZE) & PAGE_MASK;
1961	} while (start != end);
1962	mmap_read_unlock(mm);
1963
1964	if (size > (unsigned long)uaddr - start)
1965	return size - ((unsigned long)uaddr - start);
1966	return 0;
1967	}
1968	EXPORT_SYMBOL(fault_in_safe_writeable);
1969
1970	/**
1971	* fault_in_readable - fault in userspace address range for reading
1972	* @uaddr: start of user address range
1973	* @size: size of user address range
1974	*
1975	* Returns the number of bytes not faulted in (like copy_to_user() and
1976	* copy_from_user()).
1977	*/
1978	size_t fault_in_readable(const char __user *uaddr, size_t size)
1979	{
1980	const char __user *start = uaddr, *end;
1981	volatile char c;
1982
1983	if (unlikely(size == 0))
1984	return 0;
1985	if (!user_read_access_begin(uaddr, size))
1986	return size;
1987	if (!PAGE_ALIGNED(uaddr)) {
1988	unsafe_get_user(c, uaddr, out);
1989	uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
1990	}
1991	end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
1992	if (unlikely(end < start))
1993	end = NULL;
1994	while (uaddr != end) {
1995	unsafe_get_user(c, uaddr, out);
1996	uaddr += PAGE_SIZE;
1997	}
1998
1999	out:
2000	user_read_access_end();
2001	(void)c;
2002	if (size > uaddr - start)
2003	return size - (uaddr - start);
2004	return 0;
2005	}
2006	EXPORT_SYMBOL(fault_in_readable);
2007
2008	/**
2009	* get_dump_page() - pin user page in memory while writing it to core dump
2010	* @addr: user address
2011	*
2012	* Returns struct page pointer of user page pinned for dump,
2013	* to be freed afterwards by put_page().
2014	*
2015	* Returns NULL on any kind of failure - a hole must then be inserted into
2016	* the corefile, to preserve alignment with its headers; and also returns
2017	* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
2018	* allowing a hole to be left in the corefile to save disk space.
2019	*
2020	* Called without mmap_lock (takes and releases the mmap_lock by itself).
2021	*/
2022	#ifdef CONFIG_ELF_CORE
2023	struct page *get_dump_page(unsigned long addr)
2024	{
2025	struct page *page;
2026	int locked = 0;
2027	int ret;
2028
2029	ret = __get_user_pages_locked(current->mm, start: addr, nr_pages: 1, pages: &page, locked: &locked,
2030	flags: FOLL_FORCE | FOLL_DUMP | FOLL_GET);
2031	return (ret == 1) ? page : NULL;
2032	}
2033	#endif /* CONFIG_ELF_CORE */
2034
2035	#ifdef CONFIG_MIGRATION
2036	/*
2037	* Returns the number of collected pages. Return value is always >= 0.
2038	*/
2039	static unsigned long collect_longterm_unpinnable_pages(
2040	struct list_head *movable_page_list,
2041	unsigned long nr_pages,
2042	struct page **pages)
2043	{
2044	unsigned long i, collected = 0;
2045	struct folio *prev_folio = NULL;
2046	bool drain_allow = true;
2047
2048	for (i = 0; i < nr_pages; i++) {
2049	struct folio *folio = page_folio(pages[i]);
2050
2051	if (folio == prev_folio)
2052	continue;
2053	prev_folio = folio;
2054
2055	if (folio_is_longterm_pinnable(folio))
2056	continue;
2057
2058	collected++;
2059
2060	if (folio_is_device_coherent(folio))
2061	continue;
2062
2063	if (folio_test_hugetlb(folio)) {
2064	isolate_hugetlb(folio, list: movable_page_list);
2065	continue;
2066	}
2067
2068	if (!folio_test_lru(folio) && drain_allow) {
2069	lru_add_drain_all();
2070	drain_allow = false;
2071	}
2072
2073	if (!folio_isolate_lru(folio))
2074	continue;
2075
2076	list_add_tail(new: &folio->lru, head: movable_page_list);
2077	node_stat_mod_folio(folio,
2078	item: NR_ISOLATED_ANON + folio_is_file_lru(folio),
2079	nr: folio_nr_pages(folio));
2080	}
2081
2082	return collected;
2083	}
2084
2085	/*
2086	* Unpins all pages and migrates device coherent pages and movable_page_list.
2087	* Returns -EAGAIN if all pages were successfully migrated or -errno for failure
2088	* (or partial success).
2089	*/
2090	static int migrate_longterm_unpinnable_pages(
2091	struct list_head *movable_page_list,
2092	unsigned long nr_pages,
2093	struct page **pages)
2094	{
2095	int ret;
2096	unsigned long i;
2097
2098	for (i = 0; i < nr_pages; i++) {
2099	struct folio *folio = page_folio(pages[i]);
2100
2101	if (folio_is_device_coherent(folio)) {
2102	/*
2103	* Migration will fail if the page is pinned, so convert
2104	* the pin on the source page to a normal reference.
2105	*/
2106	pages[i] = NULL;
2107	folio_get(folio);
2108	gup_put_folio(folio, refs: 1, flags: FOLL_PIN);
2109
2110	if (migrate_device_coherent_page(page: &folio->page)) {
2111	ret = -EBUSY;
2112	goto err;
2113	}
2114
2115	continue;
2116	}
2117
2118	/*
2119	* We can't migrate pages with unexpected references, so drop
2120	* the reference obtained by __get_user_pages_locked().
2121	* Migrating pages have been added to movable_page_list after
2122	* calling folio_isolate_lru() which takes a reference so the
2123	* page won't be freed if it's migrating.
2124	*/
2125	unpin_user_page(pages[i]);
2126	pages[i] = NULL;
2127	}
2128
2129	if (!list_empty(head: movable_page_list)) {
2130	struct migration_target_control mtc = {
2131	.nid = NUMA_NO_NODE,
2132	.gfp_mask = GFP_USER | __GFP_NOWARN,
2133	};
2134
2135	if (migrate_pages(l: movable_page_list, new: alloc_migration_target,
2136	NULL, private: (unsigned long)&mtc, mode: MIGRATE_SYNC,
2137	reason: MR_LONGTERM_PIN, NULL)) {
2138	ret = -ENOMEM;
2139	goto err;
2140	}
2141	}
2142
2143	putback_movable_pages(l: movable_page_list);
2144
2145	return -EAGAIN;
2146
2147	err:
2148	for (i = 0; i < nr_pages; i++)
2149	if (pages[i])
2150	unpin_user_page(pages[i]);
2151	putback_movable_pages(l: movable_page_list);
2152
2153	return ret;
2154	}
2155
2156	/*
2157	* Check whether all pages are *allowed* to be pinned. Rather confusingly, all
2158	* pages in the range are required to be pinned via FOLL_PIN, before calling
2159	* this routine.
2160	*
2161	* If any pages in the range are not allowed to be pinned, then this routine
2162	* will migrate those pages away, unpin all the pages in the range and return
2163	* -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
2164	* call this routine again.
2165	*
2166	* If an error other than -EAGAIN occurs, this indicates a migration failure.
2167	* The caller should give up, and propagate the error back up the call stack.
2168	*
2169	* If everything is OK and all pages in the range are allowed to be pinned, then
2170	* this routine leaves all pages pinned and returns zero for success.
2171	*/
2172	static long check_and_migrate_movable_pages(unsigned long nr_pages,
2173	struct page **pages)
2174	{
2175	unsigned long collected;
2176	LIST_HEAD(movable_page_list);
2177
2178	collected = collect_longterm_unpinnable_pages(movable_page_list: &movable_page_list,
2179	nr_pages, pages);
2180	if (!collected)
2181	return 0;
2182
2183	return migrate_longterm_unpinnable_pages(movable_page_list: &movable_page_list, nr_pages,
2184	pages);
2185	}
2186	#else
2187	static long check_and_migrate_movable_pages(unsigned long nr_pages,
2188	struct page **pages)
2189	{
2190	return 0;
2191	}
2192	#endif /* CONFIG_MIGRATION */
2193
2194	/*
2195	* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
2196	* allows us to process the FOLL_LONGTERM flag.
2197	*/
2198	static long __gup_longterm_locked(struct mm_struct *mm,
2199	unsigned long start,
2200	unsigned long nr_pages,
2201	struct page **pages,
2202	int *locked,
2203	unsigned int gup_flags)
2204	{
2205	unsigned int flags;
2206	long rc, nr_pinned_pages;
2207
2208	if (!(gup_flags & FOLL_LONGTERM))
2209	return __get_user_pages_locked(mm, start, nr_pages, pages,
2210	locked, flags: gup_flags);
2211
2212	flags = memalloc_pin_save();
2213	do {
2214	nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages,
2215	pages, locked,
2216	flags: gup_flags);
2217	if (nr_pinned_pages <= 0) {
2218	rc = nr_pinned_pages;
2219	break;
2220	}
2221
2222	/* FOLL_LONGTERM implies FOLL_PIN */
2223	rc = check_and_migrate_movable_pages(nr_pages: nr_pinned_pages, pages);
2224	} while (rc == -EAGAIN);
2225	memalloc_pin_restore(flags);
2226	return rc ? rc : nr_pinned_pages;
2227	}
2228
2229	/*
2230	* Check that the given flags are valid for the exported gup/pup interface, and
2231	* update them with the required flags that the caller must have set.
2232	*/
2233	static bool is_valid_gup_args(struct page **pages, int *locked,
2234	unsigned int *gup_flags_p, unsigned int to_set)
2235	{
2236	unsigned int gup_flags = *gup_flags_p;
2237
2238	/*
2239	* These flags not allowed to be specified externally to the gup
2240	* interfaces:
2241	* - FOLL_TOUCH/FOLL_PIN/FOLL_TRIED/FOLL_FAST_ONLY are internal only
2242	* - FOLL_REMOTE is internal only and used on follow_page()
2243	* - FOLL_UNLOCKABLE is internal only and used if locked is !NULL
2244	*/
2245	if (WARN_ON_ONCE(gup_flags & INTERNAL_GUP_FLAGS))
2246	return false;
2247
2248	gup_flags |= to_set;
2249	if (locked) {
2250	/* At the external interface locked must be set */
2251	if (WARN_ON_ONCE(*locked != 1))
2252	return false;
2253
2254	gup_flags |= FOLL_UNLOCKABLE;
2255	}
2256
2257	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
2258	if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) ==
2259	(FOLL_PIN | FOLL_GET)))
2260	return false;
2261
2262	/* LONGTERM can only be specified when pinning */
2263	if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM)))
2264	return false;
2265
2266	/* Pages input must be given if using GET/PIN */
2267	if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages))
2268	return false;
2269
2270	/* We want to allow the pgmap to be hot-unplugged at all times */
2271	if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) &&
2272	(gup_flags & FOLL_PCI_P2PDMA)))
2273	return false;
2274
2275	*gup_flags_p = gup_flags;
2276	return true;
2277	}
2278
2279	#ifdef CONFIG_MMU
2280	/**
2281	* get_user_pages_remote() - pin user pages in memory
2282	* @mm: mm_struct of target mm
2283	* @start: starting user address
2284	* @nr_pages: number of pages from start to pin
2285	* @gup_flags: flags modifying lookup behaviour
2286	* @pages: array that receives pointers to the pages pinned.
2287	* Should be at least nr_pages long. Or NULL, if caller
2288	* only intends to ensure the pages are faulted in.
2289	* @locked: pointer to lock flag indicating whether lock is held and
2290	* subsequently whether VM_FAULT_RETRY functionality can be
2291	* utilised. Lock must initially be held.
2292	*
2293	* Returns either number of pages pinned (which may be less than the
2294	* number requested), or an error. Details about the return value:
2295	*
2296	* -- If nr_pages is 0, returns 0.
2297	* -- If nr_pages is >0, but no pages were pinned, returns -errno.
2298	* -- If nr_pages is >0, and some pages were pinned, returns the number of
2299	* pages pinned. Again, this may be less than nr_pages.
2300	*
2301	* The caller is responsible for releasing returned @pages, via put_page().
2302	*
2303	* Must be called with mmap_lock held for read or write.
2304	*
2305	* get_user_pages_remote walks a process's page tables and takes a reference
2306	* to each struct page that each user address corresponds to at a given
2307	* instant. That is, it takes the page that would be accessed if a user
2308	* thread accesses the given user virtual address at that instant.
2309	*
2310	* This does not guarantee that the page exists in the user mappings when
2311	* get_user_pages_remote returns, and there may even be a completely different
2312	* page there in some cases (eg. if mmapped pagecache has been invalidated
2313	* and subsequently re-faulted). However it does guarantee that the page
2314	* won't be freed completely. And mostly callers simply care that the page
2315	* contains data that was valid *at some point in time*. Typically, an IO
2316	* or similar operation cannot guarantee anything stronger anyway because
2317	* locks can't be held over the syscall boundary.
2318	*
2319	* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
2320	* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
2321	* be called after the page is finished with, and before put_page is called.
2322	*
2323	* get_user_pages_remote is typically used for fewer-copy IO operations,
2324	* to get a handle on the memory by some means other than accesses
2325	* via the user virtual addresses. The pages may be submitted for
2326	* DMA to devices or accessed via their kernel linear mapping (via the
2327	* kmap APIs). Care should be taken to use the correct cache flushing APIs.
2328	*
2329	* See also get_user_pages_fast, for performance critical applications.
2330	*
2331	* get_user_pages_remote should be phased out in favor of
2332	* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
2333	* should use get_user_pages_remote because it cannot pass
2334	* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
2335	*/
2336	long get_user_pages_remote(struct mm_struct *mm,
2337	unsigned long start, unsigned long nr_pages,
2338	unsigned int gup_flags, struct page **pages,
2339	int *locked)
2340	{
2341	int local_locked = 1;
2342
2343	if (!is_valid_gup_args(pages, locked, gup_flags_p: &gup_flags,
2344	to_set: FOLL_TOUCH | FOLL_REMOTE))
2345	return -EINVAL;
2346
2347	return __get_user_pages_locked(mm, start, nr_pages, pages,
2348	locked: locked ? locked : &local_locked,
2349	flags: gup_flags);
2350	}
2351	EXPORT_SYMBOL(get_user_pages_remote);
2352
2353	#else /* CONFIG_MMU */
2354	long get_user_pages_remote(struct mm_struct *mm,
2355	unsigned long start, unsigned long nr_pages,
2356	unsigned int gup_flags, struct page **pages,
2357	int *locked)
2358	{
2359	return 0;
2360	}
2361	#endif /* !CONFIG_MMU */
2362
2363	/**
2364	* get_user_pages() - pin user pages in memory
2365	* @start: starting user address
2366	* @nr_pages: number of pages from start to pin
2367	* @gup_flags: flags modifying lookup behaviour
2368	* @pages: array that receives pointers to the pages pinned.
2369	* Should be at least nr_pages long. Or NULL, if caller
2370	* only intends to ensure the pages are faulted in.
2371	*
2372	* This is the same as get_user_pages_remote(), just with a less-flexible
2373	* calling convention where we assume that the mm being operated on belongs to
2374	* the current task, and doesn't allow passing of a locked parameter. We also
2375	* obviously don't pass FOLL_REMOTE in here.
2376	*/
2377	long get_user_pages(unsigned long start, unsigned long nr_pages,
2378	unsigned int gup_flags, struct page **pages)
2379	{
2380	int locked = 1;
2381
2382	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_TOUCH))
2383	return -EINVAL;
2384
2385	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2386	locked: &locked, flags: gup_flags);
2387	}
2388	EXPORT_SYMBOL(get_user_pages);
2389
2390	/*
2391	* get_user_pages_unlocked() is suitable to replace the form:
2392	*
2393	* mmap_read_lock(mm);
2394	* get_user_pages(mm, ..., pages, NULL);
2395	* mmap_read_unlock(mm);
2396	*
2397	* with:
2398	*
2399	* get_user_pages_unlocked(mm, ..., pages);
2400	*
2401	* It is functionally equivalent to get_user_pages_fast so
2402	* get_user_pages_fast should be used instead if specific gup_flags
2403	* (e.g. FOLL_FORCE) are not required.
2404	*/
2405	long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2406	struct page **pages, unsigned int gup_flags)
2407	{
2408	int locked = 0;
2409
2410	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
2411	to_set: FOLL_TOUCH | FOLL_UNLOCKABLE))
2412	return -EINVAL;
2413
2414	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2415	locked: &locked, flags: gup_flags);
2416	}
2417	EXPORT_SYMBOL(get_user_pages_unlocked);
2418
2419	/*
2420	* Fast GUP
2421	*
2422	* get_user_pages_fast attempts to pin user pages by walking the page
2423	* tables directly and avoids taking locks. Thus the walker needs to be
2424	* protected from page table pages being freed from under it, and should
2425	* block any THP splits.
2426	*
2427	* One way to achieve this is to have the walker disable interrupts, and
2428	* rely on IPIs from the TLB flushing code blocking before the page table
2429	* pages are freed. This is unsuitable for architectures that do not need
2430	* to broadcast an IPI when invalidating TLBs.
2431	*
2432	* Another way to achieve this is to batch up page table containing pages
2433	* belonging to more than one mm_user, then rcu_sched a callback to free those
2434	* pages. Disabling interrupts will allow the fast_gup walker to both block
2435	* the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2436	* (which is a relatively rare event). The code below adopts this strategy.
2437	*
2438	* Before activating this code, please be aware that the following assumptions
2439	* are currently made:
2440	*
2441	* *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2442	* free pages containing page tables or TLB flushing requires IPI broadcast.
2443	*
2444	* *) ptes can be read atomically by the architecture.
2445	*
2446	* *) access_ok is sufficient to validate userspace address ranges.
2447	*
2448	* The last two assumptions can be relaxed by the addition of helper functions.
2449	*
2450	* This code is based heavily on the PowerPC implementation by Nick Piggin.
2451	*/
2452	#ifdef CONFIG_HAVE_FAST_GUP
2453
2454	/*
2455	* Used in the GUP-fast path to determine whether a pin is permitted for a
2456	* specific folio.
2457	*
2458	* This call assumes the caller has pinned the folio, that the lowest page table
2459	* level still points to this folio, and that interrupts have been disabled.
2460	*
2461	* Writing to pinned file-backed dirty tracked folios is inherently problematic
2462	* (see comment describing the writable_file_mapping_allowed() function). We
2463	* therefore try to avoid the most egregious case of a long-term mapping doing
2464	* so.
2465	*
2466	* This function cannot be as thorough as that one as the VMA is not available
2467	* in the fast path, so instead we whitelist known good cases and if in doubt,
2468	* fall back to the slow path.
2469	*/
2470	static bool folio_fast_pin_allowed(struct folio *folio, unsigned int flags)
2471	{
2472	struct address_space *mapping;
2473	unsigned long mapping_flags;
2474
2475	/*
2476	* If we aren't pinning then no problematic write can occur. A long term
2477	* pin is the most egregious case so this is the one we disallow.
2478	*/
2479	if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) !=
2480	(FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE))
2481	return true;
2482
2483	/* The folio is pinned, so we can safely access folio fields. */
2484
2485	if (WARN_ON_ONCE(folio_test_slab(folio)))
2486	return false;
2487
2488	/* hugetlb mappings do not require dirty-tracking. */
2489	if (folio_test_hugetlb(folio))
2490	return true;
2491
2492	/*
2493	* GUP-fast disables IRQs. When IRQS are disabled, RCU grace periods
2494	* cannot proceed, which means no actions performed under RCU can
2495	* proceed either.
2496	*
2497	* inodes and thus their mappings are freed under RCU, which means the
2498	* mapping cannot be freed beneath us and thus we can safely dereference
2499	* it.
2500	*/
2501	lockdep_assert_irqs_disabled();
2502
2503	/*
2504	* However, there may be operations which _alter_ the mapping, so ensure
2505	* we read it once and only once.
2506	*/
2507	mapping = READ_ONCE(folio->mapping);
2508
2509	/*
2510	* The mapping may have been truncated, in any case we cannot determine
2511	* if this mapping is safe - fall back to slow path to determine how to
2512	* proceed.
2513	*/
2514	if (!mapping)
2515	return false;
2516
2517	/* Anonymous folios pose no problem. */
2518	mapping_flags = (unsigned long)mapping & PAGE_MAPPING_FLAGS;
2519	if (mapping_flags)
2520	return mapping_flags & PAGE_MAPPING_ANON;
2521
2522	/*
2523	* At this point, we know the mapping is non-null and points to an
2524	* address_space object. The only remaining whitelisted file system is
2525	* shmem.
2526	*/
2527	return shmem_mapping(mapping);
2528	}
2529
2530	static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2531	unsigned int flags,
2532	struct page **pages)
2533	{
2534	while ((*nr) - nr_start) {
2535	struct page *page = pages[--(*nr)];
2536
2537	ClearPageReferenced(page);
2538	if (flags & FOLL_PIN)
2539	unpin_user_page(page);
2540	else
2541	put_page(page);
2542	}
2543	}
2544
2545	#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2546	/*
2547	* Fast-gup relies on pte change detection to avoid concurrent pgtable
2548	* operations.
2549	*
2550	* To pin the page, fast-gup needs to do below in order:
2551	* (1) pin the page (by prefetching pte), then (2) check pte not changed.
2552	*
2553	* For the rest of pgtable operations where pgtable updates can be racy
2554	* with fast-gup, we need to do (1) clear pte, then (2) check whether page
2555	* is pinned.
2556	*
2557	* Above will work for all pte-level operations, including THP split.
2558	*
2559	* For THP collapse, it's a bit more complicated because fast-gup may be
2560	* walking a pgtable page that is being freed (pte is still valid but pmd
2561	* can be cleared already). To avoid race in such condition, we need to
2562	* also check pmd here to make sure pmd doesn't change (corresponds to
2563	* pmdp_collapse_flush() in the THP collapse code path).
2564	*/
2565	static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2566	unsigned long end, unsigned int flags,
2567	struct page **pages, int *nr)
2568	{
2569	struct dev_pagemap *pgmap = NULL;
2570	int nr_start = *nr, ret = 0;
2571	pte_t *ptep, *ptem;
2572
2573	ptem = ptep = pte_offset_map(pmd: &pmd, addr);
2574	if (!ptep)
2575	return 0;
2576	do {
2577	pte_t pte = ptep_get_lockless(ptep);
2578	struct page *page;
2579	struct folio *folio;
2580
2581	/*
2582	* Always fallback to ordinary GUP on PROT_NONE-mapped pages:
2583	* pte_access_permitted() better should reject these pages
2584	* either way: otherwise, GUP-fast might succeed in
2585	* cases where ordinary GUP would fail due to VMA access
2586	* permissions.
2587	*/
2588	if (pte_protnone(pte))
2589	goto pte_unmap;
2590
2591	if (!pte_access_permitted(pte, write: flags & FOLL_WRITE))
2592	goto pte_unmap;
2593
2594	if (pte_devmap(a: pte)) {
2595	if (unlikely(flags & FOLL_LONGTERM))
2596	goto pte_unmap;
2597
2598	pgmap = get_dev_pagemap(pfn: pte_pfn(pte), pgmap);
2599	if (unlikely(!pgmap)) {
2600	undo_dev_pagemap(nr, nr_start, flags, pages);
2601	goto pte_unmap;
2602	}
2603	} else if (pte_special(pte))
2604	goto pte_unmap;
2605
2606	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2607	page = pte_page(pte);
2608
2609	folio = try_grab_folio(page, refs: 1, flags);
2610	if (!folio)
2611	goto pte_unmap;
2612
2613	if (unlikely(folio_is_secretmem(folio))) {
2614	gup_put_folio(folio, refs: 1, flags);
2615	goto pte_unmap;
2616	}
2617
2618	if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
2619	unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2620	gup_put_folio(folio, refs: 1, flags);
2621	goto pte_unmap;
2622	}
2623
2624	if (!folio_fast_pin_allowed(folio, flags)) {
2625	gup_put_folio(folio, refs: 1, flags);
2626	goto pte_unmap;
2627	}
2628
2629	if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) {
2630	gup_put_folio(folio, refs: 1, flags);
2631	goto pte_unmap;
2632	}
2633
2634	/*
2635	* We need to make the page accessible if and only if we are
2636	* going to access its content (the FOLL_PIN case). Please
2637	* see Documentation/core-api/pin_user_pages.rst for
2638	* details.
2639	*/
2640	if (flags & FOLL_PIN) {
2641	ret = arch_make_page_accessible(page);
2642	if (ret) {
2643	gup_put_folio(folio, refs: 1, flags);
2644	goto pte_unmap;
2645	}
2646	}
2647	folio_set_referenced(folio);
2648	pages[*nr] = page;
2649	(*nr)++;
2650	} while (ptep++, addr += PAGE_SIZE, addr != end);
2651
2652	ret = 1;
2653
2654	pte_unmap:
2655	if (pgmap)
2656	put_dev_pagemap(pgmap);
2657	pte_unmap(pte: ptem);
2658	return ret;
2659	}
2660	#else
2661
2662	/*
2663	* If we can't determine whether or not a pte is special, then fail immediately
2664	* for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2665	* to be special.
2666	*
2667	* For a futex to be placed on a THP tail page, get_futex_key requires a
2668	* get_user_pages_fast_only implementation that can pin pages. Thus it's still
2669	* useful to have gup_huge_pmd even if we can't operate on ptes.
2670	*/
2671	static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2672	unsigned long end, unsigned int flags,
2673	struct page **pages, int *nr)
2674	{
2675	return 0;
2676	}
2677	#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2678
2679	#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2680	static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2681	unsigned long end, unsigned int flags,
2682	struct page **pages, int *nr)
2683	{
2684	int nr_start = *nr;
2685	struct dev_pagemap *pgmap = NULL;
2686
2687	do {
2688	struct page *page = pfn_to_page(pfn);
2689
2690	pgmap = get_dev_pagemap(pfn, pgmap);
2691	if (unlikely(!pgmap)) {
2692	undo_dev_pagemap(nr, nr_start, flags, pages);
2693	break;
2694	}
2695
2696	if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
2697	undo_dev_pagemap(nr, nr_start, flags, pages);
2698	break;
2699	}
2700
2701	SetPageReferenced(page);
2702	pages[*nr] = page;
2703	if (unlikely(try_grab_page(page, flags))) {
2704	undo_dev_pagemap(nr, nr_start, flags, pages);
2705	break;
2706	}
2707	(*nr)++;
2708	pfn++;
2709	} while (addr += PAGE_SIZE, addr != end);
2710
2711	put_dev_pagemap(pgmap);
2712	return addr == end;
2713	}
2714
2715	static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2716	unsigned long end, unsigned int flags,
2717	struct page **pages, int *nr)
2718	{
2719	unsigned long fault_pfn;
2720	int nr_start = *nr;
2721
2722	fault_pfn = pmd_pfn(pmd: orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2723	if (!__gup_device_huge(pfn: fault_pfn, addr, end, flags, pages, nr))
2724	return 0;
2725
2726	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2727	undo_dev_pagemap(nr, nr_start, flags, pages);
2728	return 0;
2729	}
2730	return 1;
2731	}
2732
2733	static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2734	unsigned long end, unsigned int flags,
2735	struct page **pages, int *nr)
2736	{
2737	unsigned long fault_pfn;
2738	int nr_start = *nr;
2739
2740	fault_pfn = pud_pfn(pud: orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2741	if (!__gup_device_huge(pfn: fault_pfn, addr, end, flags, pages, nr))
2742	return 0;
2743
2744	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2745	undo_dev_pagemap(nr, nr_start, flags, pages);
2746	return 0;
2747	}
2748	return 1;
2749	}
2750	#else
2751	static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2752	unsigned long end, unsigned int flags,
2753	struct page **pages, int *nr)
2754	{
2755	BUILD_BUG();
2756	return 0;
2757	}
2758
2759	static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2760	unsigned long end, unsigned int flags,
2761	struct page **pages, int *nr)
2762	{
2763	BUILD_BUG();
2764	return 0;
2765	}
2766	#endif
2767
2768	static int record_subpages(struct page *page, unsigned long addr,
2769	unsigned long end, struct page **pages)
2770	{
2771	int nr;
2772
2773	for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
2774	pages[nr] = nth_page(page, nr);
2775
2776	return nr;
2777	}
2778
2779	#ifdef CONFIG_ARCH_HAS_HUGEPD
2780	static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2781	unsigned long sz)
2782	{
2783	unsigned long __boundary = (addr + sz) & ~(sz-1);
2784	return (__boundary - 1 < end - 1) ? __boundary : end;
2785	}
2786
2787	static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2788	unsigned long end, unsigned int flags,
2789	struct page **pages, int *nr)
2790	{
2791	unsigned long pte_end;
2792	struct page *page;
2793	struct folio *folio;
2794	pte_t pte;
2795	int refs;
2796
2797	pte_end = (addr + sz) & ~(sz-1);
2798	if (pte_end < end)
2799	end = pte_end;
2800
2801	pte = huge_ptep_get(ptep);
2802
2803	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2804	return 0;
2805
2806	/* hugepages are never "special" */
2807	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2808
2809	page = nth_page(pte_page(pte), (addr & (sz - 1)) >> PAGE_SHIFT);
2810	refs = record_subpages(page, addr, end, pages + *nr);
2811
2812	folio = try_grab_folio(page, refs, flags);
2813	if (!folio)
2814	return 0;
2815
2816	if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2817	gup_put_folio(folio, refs, flags);
2818	return 0;
2819	}
2820
2821	if (!folio_fast_pin_allowed(folio, flags)) {
2822	gup_put_folio(folio, refs, flags);
2823	return 0;
2824	}
2825
2826	if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) {
2827	gup_put_folio(folio, refs, flags);
2828	return 0;
2829	}
2830
2831	*nr += refs;
2832	folio_set_referenced(folio);
2833	return 1;
2834	}
2835
2836	static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2837	unsigned int pdshift, unsigned long end, unsigned int flags,
2838	struct page **pages, int *nr)
2839	{
2840	pte_t *ptep;
2841	unsigned long sz = 1UL << hugepd_shift(hugepd);
2842	unsigned long next;
2843
2844	ptep = hugepte_offset(hugepd, addr, pdshift);
2845	do {
2846	next = hugepte_addr_end(addr, end, sz);
2847	if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2848	return 0;
2849	} while (ptep++, addr = next, addr != end);
2850
2851	return 1;
2852	}
2853	#else
2854	static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2855	unsigned int pdshift, unsigned long end, unsigned int flags,
2856	struct page **pages, int *nr)
2857	{
2858	return 0;
2859	}
2860	#endif /* CONFIG_ARCH_HAS_HUGEPD */
2861
2862	static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2863	unsigned long end, unsigned int flags,
2864	struct page **pages, int *nr)
2865	{
2866	struct page *page;
2867	struct folio *folio;
2868	int refs;
2869
2870	if (!pmd_access_permitted(pmd: orig, write: flags & FOLL_WRITE))
2871	return 0;
2872
2873	if (pmd_devmap(pmd: orig)) {
2874	if (unlikely(flags & FOLL_LONGTERM))
2875	return 0;
2876	return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2877	pages, nr);
2878	}
2879
2880	page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT);
2881	refs = record_subpages(page, addr, end, pages: pages + *nr);
2882
2883	folio = try_grab_folio(page, refs, flags);
2884	if (!folio)
2885	return 0;
2886
2887	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2888	gup_put_folio(folio, refs, flags);
2889	return 0;
2890	}
2891
2892	if (!folio_fast_pin_allowed(folio, flags)) {
2893	gup_put_folio(folio, refs, flags);
2894	return 0;
2895	}
2896	if (!pmd_write(pmd: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2897	gup_put_folio(folio, refs, flags);
2898	return 0;
2899	}
2900
2901	*nr += refs;
2902	folio_set_referenced(folio);
2903	return 1;
2904	}
2905
2906	static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2907	unsigned long end, unsigned int flags,
2908	struct page **pages, int *nr)
2909	{
2910	struct page *page;
2911	struct folio *folio;
2912	int refs;
2913
2914	if (!pud_access_permitted(pud: orig, write: flags & FOLL_WRITE))
2915	return 0;
2916
2917	if (pud_devmap(pud: orig)) {
2918	if (unlikely(flags & FOLL_LONGTERM))
2919	return 0;
2920	return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2921	pages, nr);
2922	}
2923
2924	page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT);
2925	refs = record_subpages(page, addr, end, pages: pages + *nr);
2926
2927	folio = try_grab_folio(page, refs, flags);
2928	if (!folio)
2929	return 0;
2930
2931	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2932	gup_put_folio(folio, refs, flags);
2933	return 0;
2934	}
2935
2936	if (!folio_fast_pin_allowed(folio, flags)) {
2937	gup_put_folio(folio, refs, flags);
2938	return 0;
2939	}
2940
2941	if (!pud_write(pud: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2942	gup_put_folio(folio, refs, flags);
2943	return 0;
2944	}
2945
2946	*nr += refs;
2947	folio_set_referenced(folio);
2948	return 1;
2949	}
2950
2951	static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2952	unsigned long end, unsigned int flags,
2953	struct page **pages, int *nr)
2954	{
2955	int refs;
2956	struct page *page;
2957	struct folio *folio;
2958
2959	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2960	return 0;
2961
2962	BUILD_BUG_ON(pgd_devmap(orig));
2963
2964	page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2965	refs = record_subpages(page, addr, end, pages: pages + *nr);
2966
2967	folio = try_grab_folio(page, refs, flags);
2968	if (!folio)
2969	return 0;
2970
2971	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2972	gup_put_folio(folio, refs, flags);
2973	return 0;
2974	}
2975
2976	if (!pgd_write(pgd: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2977	gup_put_folio(folio, refs, flags);
2978	return 0;
2979	}
2980
2981	if (!folio_fast_pin_allowed(folio, flags)) {
2982	gup_put_folio(folio, refs, flags);
2983	return 0;
2984	}
2985
2986	*nr += refs;
2987	folio_set_referenced(folio);
2988	return 1;
2989	}
2990
2991	static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
2992	unsigned int flags, struct page **pages, int *nr)
2993	{
2994	unsigned long next;
2995	pmd_t *pmdp;
2996
2997	pmdp = pmd_offset_lockless(pudp, pud, addr);
2998	do {
2999	pmd_t pmd = pmdp_get_lockless(pmdp);
3000
3001	next = pmd_addr_end(addr, end);
3002	if (!pmd_present(pmd))
3003	return 0;
3004
3005	if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
3006	pmd_devmap(pmd))) {
3007	/* See gup_pte_range() */
3008	if (pmd_protnone(pmd))
3009	return 0;
3010
3011	if (!gup_huge_pmd(orig: pmd, pmdp, addr, end: next, flags,
3012	pages, nr))
3013	return 0;
3014
3015	} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
3016	/*
3017	* architecture have different format for hugetlbfs
3018	* pmd format and THP pmd format
3019	*/
3020	if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
3021	PMD_SHIFT, end: next, flags, pages, nr))
3022	return 0;
3023	} else if (!gup_pte_range(pmd, pmdp, addr, end: next, flags, pages, nr))
3024	return 0;
3025	} while (pmdp++, addr = next, addr != end);
3026
3027	return 1;
3028	}
3029
3030	static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
3031	unsigned int flags, struct page **pages, int *nr)
3032	{
3033	unsigned long next;
3034	pud_t *pudp;
3035
3036	pudp = pud_offset_lockless(p4dp, p4d, addr);
3037	do {
3038	pud_t pud = READ_ONCE(*pudp);
3039
3040	next = pud_addr_end(addr, end);
3041	if (unlikely(!pud_present(pud)))
3042	return 0;
3043	if (unlikely(pud_huge(pud) || pud_devmap(pud))) {
3044	if (!gup_huge_pud(orig: pud, pudp, addr, end: next, flags,
3045	pages, nr))
3046	return 0;
3047	} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
3048	if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
3049	PUD_SHIFT, end: next, flags, pages, nr))
3050	return 0;
3051	} else if (!gup_pmd_range(pudp, pud, addr, end: next, flags, pages, nr))
3052	return 0;
3053	} while (pudp++, addr = next, addr != end);
3054
3055	return 1;
3056	}
3057
3058	static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
3059	unsigned int flags, struct page **pages, int *nr)
3060	{
3061	unsigned long next;
3062	p4d_t *p4dp;
3063
3064	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
3065	do {
3066	p4d_t p4d = READ_ONCE(*p4dp);
3067
3068	next = p4d_addr_end(addr, end);
3069	if (p4d_none(p4d))
3070	return 0;
3071	BUILD_BUG_ON(p4d_huge(p4d));
3072	if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
3073	if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
3074	P4D_SHIFT, end: next, flags, pages, nr))
3075	return 0;
3076	} else if (!gup_pud_range(p4dp, p4d, addr, end: next, flags, pages, nr))
3077	return 0;
3078	} while (p4dp++, addr = next, addr != end);
3079
3080	return 1;
3081	}
3082
3083	static void gup_pgd_range(unsigned long addr, unsigned long end,
3084	unsigned int flags, struct page **pages, int *nr)
3085	{
3086	unsigned long next;
3087	pgd_t *pgdp;
3088
3089	pgdp = pgd_offset(current->mm, addr);
3090	do {
3091	pgd_t pgd = READ_ONCE(*pgdp);
3092
3093	next = pgd_addr_end(addr, end);
3094	if (pgd_none(pgd))
3095	return;
3096	if (unlikely(pgd_huge(pgd))) {
3097	if (!gup_huge_pgd(orig: pgd, pgdp, addr, end: next, flags,
3098	pages, nr))
3099	return;
3100	} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
3101	if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
3102	PGDIR_SHIFT, end: next, flags, pages, nr))
3103	return;
3104	} else if (!gup_p4d_range(pgdp, pgd, addr, end: next, flags, pages, nr))
3105	return;
3106	} while (pgdp++, addr = next, addr != end);
3107	}
3108	#else
3109	static inline void gup_pgd_range(unsigned long addr, unsigned long end,
3110	unsigned int flags, struct page **pages, int *nr)
3111	{
3112	}
3113	#endif /* CONFIG_HAVE_FAST_GUP */
3114
3115	#ifndef gup_fast_permitted
3116	/*
3117	* Check if it's allowed to use get_user_pages_fast_only() for the range, or
3118	* we need to fall back to the slow version:
3119	*/
3120	static bool gup_fast_permitted(unsigned long start, unsigned long end)
3121	{
3122	return true;
3123	}
3124	#endif
3125
3126	static unsigned long lockless_pages_from_mm(unsigned long start,
3127	unsigned long end,
3128	unsigned int gup_flags,
3129	struct page **pages)
3130	{
3131	unsigned long flags;
3132	int nr_pinned = 0;
3133	unsigned seq;
3134
3135	if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
3136	!gup_fast_permitted(start, end))
3137	return 0;
3138
3139	if (gup_flags & FOLL_PIN) {
3140	seq = raw_read_seqcount(&current->mm->write_protect_seq);
3141	if (seq & 1)
3142	return 0;
3143	}
3144
3145	/*
3146	* Disable interrupts. The nested form is used, in order to allow full,
3147	* general purpose use of this routine.
3148	*
3149	* With interrupts disabled, we block page table pages from being freed
3150	* from under us. See struct mmu_table_batch comments in
3151	* include/asm-generic/tlb.h for more details.
3152	*
3153	* We do not adopt an rcu_read_lock() here as we also want to block IPIs
3154	* that come from THPs splitting.
3155	*/
3156	local_irq_save(flags);
3157	gup_pgd_range(addr: start, end, flags: gup_flags, pages, nr: &nr_pinned);
3158	local_irq_restore(flags);
3159
3160	/*
3161	* When pinning pages for DMA there could be a concurrent write protect
3162	* from fork() via copy_page_range(), in this case always fail fast GUP.
3163	*/
3164	if (gup_flags & FOLL_PIN) {
3165	if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
3166	unpin_user_pages_lockless(pages, npages: nr_pinned);
3167	return 0;
3168	} else {
3169	sanity_check_pinned_pages(pages, npages: nr_pinned);
3170	}
3171	}
3172	return nr_pinned;
3173	}
3174
3175	static int internal_get_user_pages_fast(unsigned long start,
3176	unsigned long nr_pages,
3177	unsigned int gup_flags,
3178	struct page **pages)
3179	{
3180	unsigned long len, end;
3181	unsigned long nr_pinned;
3182	int locked = 0;
3183	int ret;
3184
3185	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
3186	FOLL_FORCE | FOLL_PIN | FOLL_GET |
3187	FOLL_FAST_ONLY | FOLL_NOFAULT |
3188	FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT)))
3189	return -EINVAL;
3190
3191	if (gup_flags & FOLL_PIN)
3192	mm_set_has_pinned_flag(mm_flags: &current->mm->flags);
3193
3194	if (!(gup_flags & FOLL_FAST_ONLY))
3195	might_lock_read(&current->mm->mmap_lock);
3196
3197	start = untagged_addr(start) & PAGE_MASK;
3198	len = nr_pages << PAGE_SHIFT;
3199	if (check_add_overflow(start, len, &end))
3200	return -EOVERFLOW;
3201	if (end > TASK_SIZE_MAX)
3202	return -EFAULT;
3203	if (unlikely(!access_ok((void __user *)start, len)))
3204	return -EFAULT;
3205
3206	nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
3207	if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
3208	return nr_pinned;
3209
3210	/* Slow path: try to get the remaining pages with get_user_pages */
3211	start += nr_pinned << PAGE_SHIFT;
3212	pages += nr_pinned;
3213	ret = __gup_longterm_locked(current->mm, start, nr_pages: nr_pages - nr_pinned,
3214	pages, locked: &locked,
3215	gup_flags: gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE);
3216	if (ret < 0) {
3217	/*
3218	* The caller has to unpin the pages we already pinned so
3219	* returning -errno is not an option
3220	*/
3221	if (nr_pinned)
3222	return nr_pinned;
3223	return ret;
3224	}
3225	return ret + nr_pinned;
3226	}
3227
3228	/**
3229	* get_user_pages_fast_only() - pin user pages in memory
3230	* @start: starting user address
3231	* @nr_pages: number of pages from start to pin
3232	* @gup_flags: flags modifying pin behaviour
3233	* @pages: array that receives pointers to the pages pinned.
3234	* Should be at least nr_pages long.
3235	*
3236	* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
3237	* the regular GUP.
3238	*
3239	* If the architecture does not support this function, simply return with no
3240	* pages pinned.
3241	*
3242	* Careful, careful! COW breaking can go either way, so a non-write
3243	* access can get ambiguous page results. If you call this function without
3244	* 'write' set, you'd better be sure that you're ok with that ambiguity.
3245	*/
3246	int get_user_pages_fast_only(unsigned long start, int nr_pages,
3247	unsigned int gup_flags, struct page **pages)
3248	{
3249	/*
3250	* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
3251	* because gup fast is always a "pin with a +1 page refcount" request.
3252	*
3253	* FOLL_FAST_ONLY is required in order to match the API description of
3254	* this routine: no fall back to regular ("slow") GUP.
3255	*/
3256	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
3257	to_set: FOLL_GET | FOLL_FAST_ONLY))
3258	return -EINVAL;
3259
3260	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3261	}
3262	EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
3263
3264	/**
3265	* get_user_pages_fast() - pin user pages in memory
3266	* @start: starting user address
3267	* @nr_pages: number of pages from start to pin
3268	* @gup_flags: flags modifying pin behaviour
3269	* @pages: array that receives pointers to the pages pinned.
3270	* Should be at least nr_pages long.
3271	*
3272	* Attempt to pin user pages in memory without taking mm->mmap_lock.
3273	* If not successful, it will fall back to taking the lock and
3274	* calling get_user_pages().
3275	*
3276	* Returns number of pages pinned. This may be fewer than the number requested.
3277	* If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
3278	* -errno.
3279	*/
3280	int get_user_pages_fast(unsigned long start, int nr_pages,
3281	unsigned int gup_flags, struct page **pages)
3282	{
3283	/*
3284	* The caller may or may not have explicitly set FOLL_GET; either way is
3285	* OK. However, internally (within mm/gup.c), gup fast variants must set
3286	* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
3287	* request.
3288	*/
3289	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_GET))
3290	return -EINVAL;
3291	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3292	}
3293	EXPORT_SYMBOL_GPL(get_user_pages_fast);
3294
3295	/**
3296	* pin_user_pages_fast() - pin user pages in memory without taking locks
3297	*
3298	* @start: starting user address
3299	* @nr_pages: number of pages from start to pin
3300	* @gup_flags: flags modifying pin behaviour
3301	* @pages: array that receives pointers to the pages pinned.
3302	* Should be at least nr_pages long.
3303	*
3304	* Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
3305	* get_user_pages_fast() for documentation on the function arguments, because
3306	* the arguments here are identical.
3307	*
3308	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3309	* see Documentation/core-api/pin_user_pages.rst for further details.
3310	*
3311	* Note that if a zero_page is amongst the returned pages, it will not have
3312	* pins in it and unpin_user_page() will not remove pins from it.
3313	*/
3314	int pin_user_pages_fast(unsigned long start, int nr_pages,
3315	unsigned int gup_flags, struct page **pages)
3316	{
3317	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_PIN))
3318	return -EINVAL;
3319	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3320	}
3321	EXPORT_SYMBOL_GPL(pin_user_pages_fast);
3322
3323	/**
3324	* pin_user_pages_remote() - pin pages of a remote process
3325	*
3326	* @mm: mm_struct of target mm
3327	* @start: starting user address
3328	* @nr_pages: number of pages from start to pin
3329	* @gup_flags: flags modifying lookup behaviour
3330	* @pages: array that receives pointers to the pages pinned.
3331	* Should be at least nr_pages long.
3332	* @locked: pointer to lock flag indicating whether lock is held and
3333	* subsequently whether VM_FAULT_RETRY functionality can be
3334	* utilised. Lock must initially be held.
3335	*
3336	* Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
3337	* get_user_pages_remote() for documentation on the function arguments, because
3338	* the arguments here are identical.
3339	*
3340	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3341	* see Documentation/core-api/pin_user_pages.rst for details.
3342	*
3343	* Note that if a zero_page is amongst the returned pages, it will not have
3344	* pins in it and unpin_user_page*() will not remove pins from it.
3345	*/
3346	long pin_user_pages_remote(struct mm_struct *mm,
3347	unsigned long start, unsigned long nr_pages,
3348	unsigned int gup_flags, struct page **pages,
3349	int *locked)
3350	{
3351	int local_locked = 1;
3352
3353	if (!is_valid_gup_args(pages, locked, gup_flags_p: &gup_flags,
3354	to_set: FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
3355	return 0;
3356	return __gup_longterm_locked(mm, start, nr_pages, pages,
3357	locked: locked ? locked : &local_locked,
3358	gup_flags);
3359	}
3360	EXPORT_SYMBOL(pin_user_pages_remote);
3361
3362	/**
3363	* pin_user_pages() - pin user pages in memory for use by other devices
3364	*
3365	* @start: starting user address
3366	* @nr_pages: number of pages from start to pin
3367	* @gup_flags: flags modifying lookup behaviour
3368	* @pages: array that receives pointers to the pages pinned.
3369	* Should be at least nr_pages long.
3370	*
3371	* Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
3372	* FOLL_PIN is set.
3373	*
3374	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3375	* see Documentation/core-api/pin_user_pages.rst for details.
3376	*
3377	* Note that if a zero_page is amongst the returned pages, it will not have
3378	* pins in it and unpin_user_page*() will not remove pins from it.
3379	*/
3380	long pin_user_pages(unsigned long start, unsigned long nr_pages,
3381	unsigned int gup_flags, struct page **pages)
3382	{
3383	int locked = 1;
3384
3385	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_PIN))
3386	return 0;
3387	return __gup_longterm_locked(current->mm, start, nr_pages,
3388	pages, locked: &locked, gup_flags);
3389	}
3390	EXPORT_SYMBOL(pin_user_pages);
3391
3392	/*
3393	* pin_user_pages_unlocked() is the FOLL_PIN variant of
3394	* get_user_pages_unlocked(). Behavior is the same, except that this one sets
3395	* FOLL_PIN and rejects FOLL_GET.
3396	*
3397	* Note that if a zero_page is amongst the returned pages, it will not have
3398	* pins in it and unpin_user_page*() will not remove pins from it.
3399	*/
3400	long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
3401	struct page **pages, unsigned int gup_flags)
3402	{
3403	int locked = 0;
3404
3405	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
3406	to_set: FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE))
3407	return 0;
3408
3409	return __gup_longterm_locked(current->mm, start, nr_pages, pages,
3410	locked: &locked, gup_flags);
3411	}
3412	EXPORT_SYMBOL(pin_user_pages_unlocked);
3413