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Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/err.h>
4#include <linux/spinlock.h>
5
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07006#include <linux/mm.h>
Dan Williams3565fce2016-01-15 16:56:55 -08007#include <linux/memremap.h>
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07008#include <linux/pagemap.h>
9#include <linux/rmap.h>
10#include <linux/swap.h>
11#include <linux/swapops.h>
12
Ingo Molnar174cd4b2017-02-02 19:15:33 +010013#include <linux/sched/signal.h>
Steve Capper2667f502014-10-09 15:29:14 -070014#include <linux/rwsem.h>
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +053015#include <linux/hugetlb.h>
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070016
Dave Hansen33a709b2016-02-12 13:02:19 -080017#include <asm/mmu_context.h>
Steve Capper2667f502014-10-09 15:29:14 -070018#include <asm/pgtable.h>
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070019#include <asm/tlbflush.h>
Steve Capper2667f502014-10-09 15:29:14 -070020
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070021#include "internal.h"
22
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070023static struct page *no_page_table(struct vm_area_struct *vma,
24 unsigned int flags)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070025{
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070026 /*
27 * When core dumping an enormous anonymous area that nobody
28 * has touched so far, we don't want to allocate unnecessary pages or
29 * page tables. Return error instead of NULL to skip handle_mm_fault,
30 * then get_dump_page() will return NULL to leave a hole in the dump.
31 * But we can only make this optimization where a hole would surely
32 * be zero-filled if handle_mm_fault() actually did handle it.
33 */
34 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
35 return ERR_PTR(-EFAULT);
36 return NULL;
37}
38
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070039static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
40 pte_t *pte, unsigned int flags)
41{
42 /* No page to get reference */
43 if (flags & FOLL_GET)
44 return -EFAULT;
45
46 if (flags & FOLL_TOUCH) {
47 pte_t entry = *pte;
48
49 if (flags & FOLL_WRITE)
50 entry = pte_mkdirty(entry);
51 entry = pte_mkyoung(entry);
52
53 if (!pte_same(*pte, entry)) {
54 set_pte_at(vma->vm_mm, address, pte, entry);
55 update_mmu_cache(vma, address, pte);
56 }
57 }
58
59 /* Proper page table entry exists, but no corresponding struct page */
60 return -EEXIST;
61}
62
Linus Torvalds19be0ea2016-10-13 13:07:36 -070063/*
64 * FOLL_FORCE can write to even unwritable pte's, but only
65 * after we've gone through a COW cycle and they are dirty.
66 */
67static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
68{
Linus Torvaldsf6f37322017-12-15 18:53:22 -080069 return pte_write(pte) ||
Linus Torvalds19be0ea2016-10-13 13:07:36 -070070 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
71}
72
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070073static struct page *follow_page_pte(struct vm_area_struct *vma,
74 unsigned long address, pmd_t *pmd, unsigned int flags)
75{
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070076 struct mm_struct *mm = vma->vm_mm;
Dan Williams3565fce2016-01-15 16:56:55 -080077 struct dev_pagemap *pgmap = NULL;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070078 struct page *page;
79 spinlock_t *ptl;
80 pte_t *ptep, pte;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070081
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070082retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070083 if (unlikely(pmd_bad(*pmd)))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070084 return no_page_table(vma, flags);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070085
86 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070087 pte = *ptep;
88 if (!pte_present(pte)) {
89 swp_entry_t entry;
90 /*
91 * KSM's break_ksm() relies upon recognizing a ksm page
92 * even while it is being migrated, so for that case we
93 * need migration_entry_wait().
94 */
95 if (likely(!(flags & FOLL_MIGRATION)))
96 goto no_page;
Kirill A. Shutemov0661a332015-02-10 14:10:04 -080097 if (pte_none(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070098 goto no_page;
99 entry = pte_to_swp_entry(pte);
100 if (!is_migration_entry(entry))
101 goto no_page;
102 pte_unmap_unlock(ptep, ptl);
103 migration_entry_wait(mm, pmd, address);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700104 goto retry;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700105 }
Mel Gorman8a0516e2015-02-12 14:58:22 -0800106 if ((flags & FOLL_NUMA) && pte_protnone(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700107 goto no_page;
Linus Torvalds19be0ea2016-10-13 13:07:36 -0700108 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700109 pte_unmap_unlock(ptep, ptl);
110 return NULL;
111 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700112
113 page = vm_normal_page(vma, address, pte);
Dan Williams3565fce2016-01-15 16:56:55 -0800114 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
115 /*
116 * Only return device mapping pages in the FOLL_GET case since
117 * they are only valid while holding the pgmap reference.
118 */
119 pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
120 if (pgmap)
121 page = pte_page(pte);
122 else
123 goto no_page;
124 } else if (unlikely(!page)) {
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700125 if (flags & FOLL_DUMP) {
126 /* Avoid special (like zero) pages in core dumps */
127 page = ERR_PTR(-EFAULT);
128 goto out;
129 }
130
131 if (is_zero_pfn(pte_pfn(pte))) {
132 page = pte_page(pte);
133 } else {
134 int ret;
135
136 ret = follow_pfn_pte(vma, address, ptep, flags);
137 page = ERR_PTR(ret);
138 goto out;
139 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700140 }
141
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800142 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
143 int ret;
144 get_page(page);
145 pte_unmap_unlock(ptep, ptl);
146 lock_page(page);
147 ret = split_huge_page(page);
148 unlock_page(page);
149 put_page(page);
150 if (ret)
151 return ERR_PTR(ret);
152 goto retry;
153 }
154
Dan Williams3565fce2016-01-15 16:56:55 -0800155 if (flags & FOLL_GET) {
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -0800156 get_page(page);
Dan Williams3565fce2016-01-15 16:56:55 -0800157
158 /* drop the pgmap reference now that we hold the page */
159 if (pgmap) {
160 put_dev_pagemap(pgmap);
161 pgmap = NULL;
162 }
163 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700164 if (flags & FOLL_TOUCH) {
165 if ((flags & FOLL_WRITE) &&
166 !pte_dirty(pte) && !PageDirty(page))
167 set_page_dirty(page);
168 /*
169 * pte_mkyoung() would be more correct here, but atomic care
170 * is needed to avoid losing the dirty bit: it is easier to use
171 * mark_page_accessed().
172 */
173 mark_page_accessed(page);
174 }
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800175 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
Kirill A. Shutemove90309c2016-01-15 16:54:33 -0800176 /* Do not mlock pte-mapped THP */
177 if (PageTransCompound(page))
178 goto out;
179
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700180 /*
181 * The preliminary mapping check is mainly to avoid the
182 * pointless overhead of lock_page on the ZERO_PAGE
183 * which might bounce very badly if there is contention.
184 *
185 * If the page is already locked, we don't need to
186 * handle it now - vmscan will handle it later if and
187 * when it attempts to reclaim the page.
188 */
189 if (page->mapping && trylock_page(page)) {
190 lru_add_drain(); /* push cached pages to LRU */
191 /*
192 * Because we lock page here, and migration is
193 * blocked by the pte's page reference, and we
194 * know the page is still mapped, we don't even
195 * need to check for file-cache page truncation.
196 */
197 mlock_vma_page(page);
198 unlock_page(page);
199 }
200 }
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700201out:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700202 pte_unmap_unlock(ptep, ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700203 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700204no_page:
205 pte_unmap_unlock(ptep, ptl);
206 if (!pte_none(pte))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700207 return NULL;
208 return no_page_table(vma, flags);
209}
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700210
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700211static struct page *follow_pmd_mask(struct vm_area_struct *vma,
212 unsigned long address, pud_t *pudp,
213 unsigned int flags, unsigned int *page_mask)
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700214{
Huang Ying68827282018-06-07 17:06:34 -0700215 pmd_t *pmd, pmdval;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700216 spinlock_t *ptl;
217 struct page *page;
218 struct mm_struct *mm = vma->vm_mm;
219
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700220 pmd = pmd_offset(pudp, address);
Huang Ying68827282018-06-07 17:06:34 -0700221 /*
222 * The READ_ONCE() will stabilize the pmdval in a register or
223 * on the stack so that it will stop changing under the code.
224 */
225 pmdval = READ_ONCE(*pmd);
226 if (pmd_none(pmdval))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700227 return no_page_table(vma, flags);
Huang Ying68827282018-06-07 17:06:34 -0700228 if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800229 page = follow_huge_pmd(mm, address, pmd, flags);
230 if (page)
231 return page;
232 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700233 }
Huang Ying68827282018-06-07 17:06:34 -0700234 if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700235 page = follow_huge_pd(vma, address,
Huang Ying68827282018-06-07 17:06:34 -0700236 __hugepd(pmd_val(pmdval)), flags,
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700237 PMD_SHIFT);
238 if (page)
239 return page;
240 return no_page_table(vma, flags);
241 }
Zi Yan84c3fc42017-09-08 16:11:01 -0700242retry:
Huang Ying68827282018-06-07 17:06:34 -0700243 if (!pmd_present(pmdval)) {
Zi Yan84c3fc42017-09-08 16:11:01 -0700244 if (likely(!(flags & FOLL_MIGRATION)))
245 return no_page_table(vma, flags);
246 VM_BUG_ON(thp_migration_supported() &&
Huang Ying68827282018-06-07 17:06:34 -0700247 !is_pmd_migration_entry(pmdval));
248 if (is_pmd_migration_entry(pmdval))
Zi Yan84c3fc42017-09-08 16:11:01 -0700249 pmd_migration_entry_wait(mm, pmd);
Huang Ying68827282018-06-07 17:06:34 -0700250 pmdval = READ_ONCE(*pmd);
251 /*
252 * MADV_DONTNEED may convert the pmd to null because
253 * mmap_sem is held in read mode
254 */
255 if (pmd_none(pmdval))
256 return no_page_table(vma, flags);
Zi Yan84c3fc42017-09-08 16:11:01 -0700257 goto retry;
258 }
Huang Ying68827282018-06-07 17:06:34 -0700259 if (pmd_devmap(pmdval)) {
Dan Williams3565fce2016-01-15 16:56:55 -0800260 ptl = pmd_lock(mm, pmd);
261 page = follow_devmap_pmd(vma, address, pmd, flags);
262 spin_unlock(ptl);
263 if (page)
264 return page;
265 }
Huang Ying68827282018-06-07 17:06:34 -0700266 if (likely(!pmd_trans_huge(pmdval)))
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800267 return follow_page_pte(vma, address, pmd, flags);
268
Huang Ying68827282018-06-07 17:06:34 -0700269 if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
Aneesh Kumar K.Vdb08f202017-02-24 14:59:53 -0800270 return no_page_table(vma, flags);
271
Zi Yan84c3fc42017-09-08 16:11:01 -0700272retry_locked:
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800273 ptl = pmd_lock(mm, pmd);
Huang Ying68827282018-06-07 17:06:34 -0700274 if (unlikely(pmd_none(*pmd))) {
275 spin_unlock(ptl);
276 return no_page_table(vma, flags);
277 }
Zi Yan84c3fc42017-09-08 16:11:01 -0700278 if (unlikely(!pmd_present(*pmd))) {
279 spin_unlock(ptl);
280 if (likely(!(flags & FOLL_MIGRATION)))
281 return no_page_table(vma, flags);
282 pmd_migration_entry_wait(mm, pmd);
283 goto retry_locked;
284 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800285 if (unlikely(!pmd_trans_huge(*pmd))) {
286 spin_unlock(ptl);
287 return follow_page_pte(vma, address, pmd, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700288 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800289 if (flags & FOLL_SPLIT) {
290 int ret;
291 page = pmd_page(*pmd);
292 if (is_huge_zero_page(page)) {
293 spin_unlock(ptl);
294 ret = 0;
Kirill A. Shutemov78ddc532016-01-15 16:52:42 -0800295 split_huge_pmd(vma, pmd, address);
Naoya Horiguchi337d9ab2016-07-26 15:24:03 -0700296 if (pmd_trans_unstable(pmd))
297 ret = -EBUSY;
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800298 } else {
299 get_page(page);
300 spin_unlock(ptl);
301 lock_page(page);
302 ret = split_huge_page(page);
303 unlock_page(page);
304 put_page(page);
Kirill A. Shutemovbaa355f2016-07-26 15:25:51 -0700305 if (pmd_none(*pmd))
306 return no_page_table(vma, flags);
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800307 }
308
309 return ret ? ERR_PTR(ret) :
310 follow_page_pte(vma, address, pmd, flags);
311 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800312 page = follow_trans_huge_pmd(vma, address, pmd, flags);
313 spin_unlock(ptl);
314 *page_mask = HPAGE_PMD_NR - 1;
315 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700316}
317
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700318
319static struct page *follow_pud_mask(struct vm_area_struct *vma,
320 unsigned long address, p4d_t *p4dp,
321 unsigned int flags, unsigned int *page_mask)
322{
323 pud_t *pud;
324 spinlock_t *ptl;
325 struct page *page;
326 struct mm_struct *mm = vma->vm_mm;
327
328 pud = pud_offset(p4dp, address);
329 if (pud_none(*pud))
330 return no_page_table(vma, flags);
331 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
332 page = follow_huge_pud(mm, address, pud, flags);
333 if (page)
334 return page;
335 return no_page_table(vma, flags);
336 }
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700337 if (is_hugepd(__hugepd(pud_val(*pud)))) {
338 page = follow_huge_pd(vma, address,
339 __hugepd(pud_val(*pud)), flags,
340 PUD_SHIFT);
341 if (page)
342 return page;
343 return no_page_table(vma, flags);
344 }
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700345 if (pud_devmap(*pud)) {
346 ptl = pud_lock(mm, pud);
347 page = follow_devmap_pud(vma, address, pud, flags);
348 spin_unlock(ptl);
349 if (page)
350 return page;
351 }
352 if (unlikely(pud_bad(*pud)))
353 return no_page_table(vma, flags);
354
355 return follow_pmd_mask(vma, address, pud, flags, page_mask);
356}
357
358
359static struct page *follow_p4d_mask(struct vm_area_struct *vma,
360 unsigned long address, pgd_t *pgdp,
361 unsigned int flags, unsigned int *page_mask)
362{
363 p4d_t *p4d;
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700364 struct page *page;
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700365
366 p4d = p4d_offset(pgdp, address);
367 if (p4d_none(*p4d))
368 return no_page_table(vma, flags);
369 BUILD_BUG_ON(p4d_huge(*p4d));
370 if (unlikely(p4d_bad(*p4d)))
371 return no_page_table(vma, flags);
372
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700373 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
374 page = follow_huge_pd(vma, address,
375 __hugepd(p4d_val(*p4d)), flags,
376 P4D_SHIFT);
377 if (page)
378 return page;
379 return no_page_table(vma, flags);
380 }
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700381 return follow_pud_mask(vma, address, p4d, flags, page_mask);
382}
383
384/**
385 * follow_page_mask - look up a page descriptor from a user-virtual address
386 * @vma: vm_area_struct mapping @address
387 * @address: virtual address to look up
388 * @flags: flags modifying lookup behaviour
389 * @page_mask: on output, *page_mask is set according to the size of the page
390 *
391 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
392 *
393 * Returns the mapped (struct page *), %NULL if no mapping exists, or
394 * an error pointer if there is a mapping to something not represented
395 * by a page descriptor (see also vm_normal_page()).
396 */
397struct page *follow_page_mask(struct vm_area_struct *vma,
398 unsigned long address, unsigned int flags,
399 unsigned int *page_mask)
400{
401 pgd_t *pgd;
402 struct page *page;
403 struct mm_struct *mm = vma->vm_mm;
404
405 *page_mask = 0;
406
407 /* make this handle hugepd */
408 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
409 if (!IS_ERR(page)) {
410 BUG_ON(flags & FOLL_GET);
411 return page;
412 }
413
414 pgd = pgd_offset(mm, address);
415
416 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
417 return no_page_table(vma, flags);
418
Anshuman Khandualfaaa5b62017-07-06 15:38:50 -0700419 if (pgd_huge(*pgd)) {
420 page = follow_huge_pgd(mm, address, pgd, flags);
421 if (page)
422 return page;
423 return no_page_table(vma, flags);
424 }
Aneesh Kumar K.V4dc71452017-07-06 15:38:56 -0700425 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
426 page = follow_huge_pd(vma, address,
427 __hugepd(pgd_val(*pgd)), flags,
428 PGDIR_SHIFT);
429 if (page)
430 return page;
431 return no_page_table(vma, flags);
432 }
Anshuman Khandualfaaa5b62017-07-06 15:38:50 -0700433
Aneesh Kumar K.V080dbb62017-07-06 15:38:44 -0700434 return follow_p4d_mask(vma, address, pgd, flags, page_mask);
435}
436
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700437static int get_gate_page(struct mm_struct *mm, unsigned long address,
438 unsigned int gup_flags, struct vm_area_struct **vma,
439 struct page **page)
440{
441 pgd_t *pgd;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300442 p4d_t *p4d;
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700443 pud_t *pud;
444 pmd_t *pmd;
445 pte_t *pte;
446 int ret = -EFAULT;
447
448 /* user gate pages are read-only */
449 if (gup_flags & FOLL_WRITE)
450 return -EFAULT;
451 if (address > TASK_SIZE)
452 pgd = pgd_offset_k(address);
453 else
454 pgd = pgd_offset_gate(mm, address);
455 BUG_ON(pgd_none(*pgd));
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300456 p4d = p4d_offset(pgd, address);
457 BUG_ON(p4d_none(*p4d));
458 pud = pud_offset(p4d, address);
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700459 BUG_ON(pud_none(*pud));
460 pmd = pmd_offset(pud, address);
Zi Yan84c3fc42017-09-08 16:11:01 -0700461 if (!pmd_present(*pmd))
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700462 return -EFAULT;
463 VM_BUG_ON(pmd_trans_huge(*pmd));
464 pte = pte_offset_map(pmd, address);
465 if (pte_none(*pte))
466 goto unmap;
467 *vma = get_gate_vma(mm);
468 if (!page)
469 goto out;
470 *page = vm_normal_page(*vma, address, *pte);
471 if (!*page) {
472 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
473 goto unmap;
474 *page = pte_page(*pte);
Jérôme Glissedf6ad692017-09-08 16:12:24 -0700475
476 /*
477 * This should never happen (a device public page in the gate
478 * area).
479 */
480 if (is_device_public_page(*page))
481 goto unmap;
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700482 }
483 get_page(*page);
484out:
485 ret = 0;
486unmap:
487 pte_unmap(pte);
488 return ret;
489}
490
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700491/*
492 * mmap_sem must be held on entry. If @nonblocking != NULL and
493 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
494 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
495 */
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700496static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
497 unsigned long address, unsigned int *flags, int *nonblocking)
498{
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700499 unsigned int fault_flags = 0;
Souptick Joarder2b740302018-08-23 17:01:36 -0700500 vm_fault_t ret;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700501
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800502 /* mlock all present pages, but do not fault in new pages */
503 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
504 return -ENOENT;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700505 if (*flags & FOLL_WRITE)
506 fault_flags |= FAULT_FLAG_WRITE;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800507 if (*flags & FOLL_REMOTE)
508 fault_flags |= FAULT_FLAG_REMOTE;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700509 if (nonblocking)
510 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
511 if (*flags & FOLL_NOWAIT)
512 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
Andres Lagar-Cavilla234b2392014-09-17 10:51:48 -0700513 if (*flags & FOLL_TRIED) {
514 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
515 fault_flags |= FAULT_FLAG_TRIED;
516 }
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700517
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700518 ret = handle_mm_fault(vma, address, fault_flags);
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700519 if (ret & VM_FAULT_ERROR) {
James Morse9a291a72017-06-02 14:46:46 -0700520 int err = vm_fault_to_errno(ret, *flags);
521
522 if (err)
523 return err;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700524 BUG();
525 }
526
527 if (tsk) {
528 if (ret & VM_FAULT_MAJOR)
529 tsk->maj_flt++;
530 else
531 tsk->min_flt++;
532 }
533
534 if (ret & VM_FAULT_RETRY) {
Andrea Arcangeli96312e62018-03-09 15:51:06 -0800535 if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700536 *nonblocking = 0;
537 return -EBUSY;
538 }
539
540 /*
541 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
542 * necessary, even if maybe_mkwrite decided not to set pte_write. We
543 * can thus safely do subsequent page lookups as if they were reads.
544 * But only do so when looping for pte_write is futile: in some cases
545 * userspace may also be wanting to write to the gotten user page,
546 * which a read fault here might prevent (a readonly page might get
547 * reCOWed by userspace write).
548 */
549 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
Mario Leinweber29231172018-04-05 16:24:18 -0700550 *flags |= FOLL_COW;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700551 return 0;
552}
553
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700554static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
555{
556 vm_flags_t vm_flags = vma->vm_flags;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800557 int write = (gup_flags & FOLL_WRITE);
558 int foreign = (gup_flags & FOLL_REMOTE);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700559
560 if (vm_flags & (VM_IO | VM_PFNMAP))
561 return -EFAULT;
562
Willy Tarreau7f7ccc22018-05-11 08:11:44 +0200563 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
564 return -EFAULT;
565
Dave Hansen1b2ee122016-02-12 13:02:21 -0800566 if (write) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700567 if (!(vm_flags & VM_WRITE)) {
568 if (!(gup_flags & FOLL_FORCE))
569 return -EFAULT;
570 /*
571 * We used to let the write,force case do COW in a
572 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
573 * set a breakpoint in a read-only mapping of an
574 * executable, without corrupting the file (yet only
575 * when that file had been opened for writing!).
576 * Anon pages in shared mappings are surprising: now
577 * just reject it.
578 */
Hugh Dickins46435362016-01-30 18:03:16 -0800579 if (!is_cow_mapping(vm_flags))
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700580 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700581 }
582 } else if (!(vm_flags & VM_READ)) {
583 if (!(gup_flags & FOLL_FORCE))
584 return -EFAULT;
585 /*
586 * Is there actually any vma we can reach here which does not
587 * have VM_MAYREAD set?
588 */
589 if (!(vm_flags & VM_MAYREAD))
590 return -EFAULT;
591 }
Dave Hansend61172b2016-02-12 13:02:24 -0800592 /*
593 * gups are always data accesses, not instruction
594 * fetches, so execute=false here
595 */
596 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800597 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700598 return 0;
599}
600
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700601/**
602 * __get_user_pages() - pin user pages in memory
603 * @tsk: task_struct of target task
604 * @mm: mm_struct of target mm
605 * @start: starting user address
606 * @nr_pages: number of pages from start to pin
607 * @gup_flags: flags modifying pin behaviour
608 * @pages: array that receives pointers to the pages pinned.
609 * Should be at least nr_pages long. Or NULL, if caller
610 * only intends to ensure the pages are faulted in.
611 * @vmas: array of pointers to vmas corresponding to each page.
612 * Or NULL if the caller does not require them.
613 * @nonblocking: whether waiting for disk IO or mmap_sem contention
614 *
615 * Returns number of pages pinned. This may be fewer than the number
616 * requested. If nr_pages is 0 or negative, returns 0. If no pages
617 * were pinned, returns -errno. Each page returned must be released
618 * with a put_page() call when it is finished with. vmas will only
619 * remain valid while mmap_sem is held.
620 *
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700621 * Must be called with mmap_sem held. It may be released. See below.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700622 *
623 * __get_user_pages walks a process's page tables and takes a reference to
624 * each struct page that each user address corresponds to at a given
625 * instant. That is, it takes the page that would be accessed if a user
626 * thread accesses the given user virtual address at that instant.
627 *
628 * This does not guarantee that the page exists in the user mappings when
629 * __get_user_pages returns, and there may even be a completely different
630 * page there in some cases (eg. if mmapped pagecache has been invalidated
631 * and subsequently re faulted). However it does guarantee that the page
632 * won't be freed completely. And mostly callers simply care that the page
633 * contains data that was valid *at some point in time*. Typically, an IO
634 * or similar operation cannot guarantee anything stronger anyway because
635 * locks can't be held over the syscall boundary.
636 *
637 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
638 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
639 * appropriate) must be called after the page is finished with, and
640 * before put_page is called.
641 *
642 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
643 * or mmap_sem contention, and if waiting is needed to pin all pages,
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700644 * *@nonblocking will be set to 0. Further, if @gup_flags does not
645 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
646 * this case.
647 *
648 * A caller using such a combination of @nonblocking and @gup_flags
649 * must therefore hold the mmap_sem for reading only, and recognize
650 * when it's been released. Otherwise, it must be held for either
651 * reading or writing and will not be released.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700652 *
653 * In most cases, get_user_pages or get_user_pages_fast should be used
654 * instead of __get_user_pages. __get_user_pages should be used only if
655 * you need some special @gup_flags.
656 */
Lorenzo Stoakes0d731752016-10-24 10:57:25 +0100657static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700658 unsigned long start, unsigned long nr_pages,
659 unsigned int gup_flags, struct page **pages,
660 struct vm_area_struct **vmas, int *nonblocking)
661{
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700662 long i = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700663 unsigned int page_mask;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700664 struct vm_area_struct *vma = NULL;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700665
666 if (!nr_pages)
667 return 0;
668
669 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
670
671 /*
672 * If FOLL_FORCE is set then do not force a full fault as the hinting
673 * fault information is unrelated to the reference behaviour of a task
674 * using the address space
675 */
676 if (!(gup_flags & FOLL_FORCE))
677 gup_flags |= FOLL_NUMA;
678
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700679 do {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700680 struct page *page;
681 unsigned int foll_flags = gup_flags;
682 unsigned int page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700683
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700684 /* first iteration or cross vma bound */
685 if (!vma || start >= vma->vm_end) {
686 vma = find_extend_vma(mm, start);
687 if (!vma && in_gate_area(mm, start)) {
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700688 int ret;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700689 ret = get_gate_page(mm, start & PAGE_MASK,
690 gup_flags, &vma,
691 pages ? &pages[i] : NULL);
692 if (ret)
693 return i ? : ret;
694 page_mask = 0;
695 goto next_page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700696 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700697
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700698 if (!vma || check_vma_flags(vma, gup_flags))
699 return i ? : -EFAULT;
700 if (is_vm_hugetlb_page(vma)) {
701 i = follow_hugetlb_page(mm, vma, pages, vmas,
702 &start, &nr_pages, i,
Andrea Arcangeli87ffc112017-02-22 15:43:13 -0800703 gup_flags, nonblocking);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700704 continue;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700705 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700706 }
707retry:
708 /*
709 * If we have a pending SIGKILL, don't keep faulting pages and
710 * potentially allocating memory.
711 */
712 if (unlikely(fatal_signal_pending(current)))
713 return i ? i : -ERESTARTSYS;
714 cond_resched();
715 page = follow_page_mask(vma, start, foll_flags, &page_mask);
716 if (!page) {
717 int ret;
718 ret = faultin_page(tsk, vma, start, &foll_flags,
719 nonblocking);
720 switch (ret) {
721 case 0:
722 goto retry;
723 case -EFAULT:
724 case -ENOMEM:
725 case -EHWPOISON:
726 return i ? i : ret;
727 case -EBUSY:
728 return i;
729 case -ENOENT:
730 goto next_page;
731 }
732 BUG();
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700733 } else if (PTR_ERR(page) == -EEXIST) {
734 /*
735 * Proper page table entry exists, but no corresponding
736 * struct page.
737 */
738 goto next_page;
739 } else if (IS_ERR(page)) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700740 return i ? i : PTR_ERR(page);
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700741 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700742 if (pages) {
743 pages[i] = page;
744 flush_anon_page(vma, page, start);
745 flush_dcache_page(page);
746 page_mask = 0;
747 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700748next_page:
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700749 if (vmas) {
750 vmas[i] = vma;
751 page_mask = 0;
752 }
753 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
754 if (page_increm > nr_pages)
755 page_increm = nr_pages;
756 i += page_increm;
757 start += page_increm * PAGE_SIZE;
758 nr_pages -= page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700759 } while (nr_pages);
760 return i;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700761}
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700762
Tobias Klauser771ab432016-12-12 16:41:53 -0800763static bool vma_permits_fault(struct vm_area_struct *vma,
764 unsigned int fault_flags)
Dave Hansend4925e02016-02-12 13:02:16 -0800765{
Dave Hansen1b2ee122016-02-12 13:02:21 -0800766 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
767 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
Dave Hansen33a709b2016-02-12 13:02:19 -0800768 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
Dave Hansend4925e02016-02-12 13:02:16 -0800769
770 if (!(vm_flags & vma->vm_flags))
771 return false;
772
Dave Hansen33a709b2016-02-12 13:02:19 -0800773 /*
774 * The architecture might have a hardware protection
Dave Hansen1b2ee122016-02-12 13:02:21 -0800775 * mechanism other than read/write that can deny access.
Dave Hansend61172b2016-02-12 13:02:24 -0800776 *
777 * gup always represents data access, not instruction
778 * fetches, so execute=false here:
Dave Hansen33a709b2016-02-12 13:02:19 -0800779 */
Dave Hansend61172b2016-02-12 13:02:24 -0800780 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800781 return false;
782
Dave Hansend4925e02016-02-12 13:02:16 -0800783 return true;
784}
785
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700786/*
787 * fixup_user_fault() - manually resolve a user page fault
788 * @tsk: the task_struct to use for page fault accounting, or
789 * NULL if faults are not to be recorded.
790 * @mm: mm_struct of target mm
791 * @address: user address
792 * @fault_flags:flags to pass down to handle_mm_fault()
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800793 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
794 * does not allow retry
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700795 *
796 * This is meant to be called in the specific scenario where for locking reasons
797 * we try to access user memory in atomic context (within a pagefault_disable()
798 * section), this returns -EFAULT, and we want to resolve the user fault before
799 * trying again.
800 *
801 * Typically this is meant to be used by the futex code.
802 *
803 * The main difference with get_user_pages() is that this function will
804 * unconditionally call handle_mm_fault() which will in turn perform all the
805 * necessary SW fixup of the dirty and young bits in the PTE, while
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800806 * get_user_pages() only guarantees to update these in the struct page.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700807 *
808 * This is important for some architectures where those bits also gate the
809 * access permission to the page because they are maintained in software. On
810 * such architectures, gup() will not be enough to make a subsequent access
811 * succeed.
812 *
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800813 * This function will not return with an unlocked mmap_sem. So it has not the
814 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700815 */
816int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800817 unsigned long address, unsigned int fault_flags,
818 bool *unlocked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700819{
820 struct vm_area_struct *vma;
Souptick Joarder2b740302018-08-23 17:01:36 -0700821 vm_fault_t ret, major = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700822
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800823 if (unlocked)
824 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
825
826retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700827 vma = find_extend_vma(mm, address);
828 if (!vma || address < vma->vm_start)
829 return -EFAULT;
830
Dave Hansend4925e02016-02-12 13:02:16 -0800831 if (!vma_permits_fault(vma, fault_flags))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700832 return -EFAULT;
833
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700834 ret = handle_mm_fault(vma, address, fault_flags);
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800835 major |= ret & VM_FAULT_MAJOR;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700836 if (ret & VM_FAULT_ERROR) {
James Morse9a291a72017-06-02 14:46:46 -0700837 int err = vm_fault_to_errno(ret, 0);
838
839 if (err)
840 return err;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700841 BUG();
842 }
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800843
844 if (ret & VM_FAULT_RETRY) {
845 down_read(&mm->mmap_sem);
846 if (!(fault_flags & FAULT_FLAG_TRIED)) {
847 *unlocked = true;
848 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
849 fault_flags |= FAULT_FLAG_TRIED;
850 goto retry;
851 }
852 }
853
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700854 if (tsk) {
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800855 if (major)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700856 tsk->maj_flt++;
857 else
858 tsk->min_flt++;
859 }
860 return 0;
861}
Paolo Bonziniadd6a0c2016-06-07 17:51:18 +0200862EXPORT_SYMBOL_GPL(fixup_user_fault);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700863
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800864static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
865 struct mm_struct *mm,
866 unsigned long start,
867 unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800868 struct page **pages,
869 struct vm_area_struct **vmas,
Al Viroe7167122017-11-19 11:32:05 -0500870 int *locked,
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800871 unsigned int flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800872{
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800873 long ret, pages_done;
874 bool lock_dropped;
875
876 if (locked) {
877 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
878 BUG_ON(vmas);
879 /* check caller initialized locked */
880 BUG_ON(*locked != 1);
881 }
882
883 if (pages)
884 flags |= FOLL_GET;
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800885
886 pages_done = 0;
887 lock_dropped = false;
888 for (;;) {
889 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
890 vmas, locked);
891 if (!locked)
892 /* VM_FAULT_RETRY couldn't trigger, bypass */
893 return ret;
894
895 /* VM_FAULT_RETRY cannot return errors */
896 if (!*locked) {
897 BUG_ON(ret < 0);
898 BUG_ON(ret >= nr_pages);
899 }
900
901 if (!pages)
902 /* If it's a prefault don't insist harder */
903 return ret;
904
905 if (ret > 0) {
906 nr_pages -= ret;
907 pages_done += ret;
908 if (!nr_pages)
909 break;
910 }
911 if (*locked) {
Andrea Arcangeli96312e62018-03-09 15:51:06 -0800912 /*
913 * VM_FAULT_RETRY didn't trigger or it was a
914 * FOLL_NOWAIT.
915 */
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800916 if (!pages_done)
917 pages_done = ret;
918 break;
919 }
920 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
921 pages += ret;
922 start += ret << PAGE_SHIFT;
923
924 /*
925 * Repeat on the address that fired VM_FAULT_RETRY
926 * without FAULT_FLAG_ALLOW_RETRY but with
927 * FAULT_FLAG_TRIED.
928 */
929 *locked = 1;
930 lock_dropped = true;
931 down_read(&mm->mmap_sem);
932 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
933 pages, NULL, NULL);
934 if (ret != 1) {
935 BUG_ON(ret > 1);
936 if (!pages_done)
937 pages_done = ret;
938 break;
939 }
940 nr_pages--;
941 pages_done++;
942 if (!nr_pages)
943 break;
944 pages++;
945 start += PAGE_SIZE;
946 }
Al Viroe7167122017-11-19 11:32:05 -0500947 if (lock_dropped && *locked) {
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800948 /*
949 * We must let the caller know we temporarily dropped the lock
950 * and so the critical section protected by it was lost.
951 */
952 up_read(&mm->mmap_sem);
953 *locked = 0;
954 }
955 return pages_done;
956}
957
958/*
959 * We can leverage the VM_FAULT_RETRY functionality in the page fault
960 * paths better by using either get_user_pages_locked() or
961 * get_user_pages_unlocked().
962 *
963 * get_user_pages_locked() is suitable to replace the form:
964 *
965 * down_read(&mm->mmap_sem);
966 * do_something()
967 * get_user_pages(tsk, mm, ..., pages, NULL);
968 * up_read(&mm->mmap_sem);
969 *
970 * to:
971 *
972 * int locked = 1;
973 * down_read(&mm->mmap_sem);
974 * do_something()
975 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
976 * if (locked)
977 * up_read(&mm->mmap_sem);
978 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200979long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes3b913172016-10-13 01:20:14 +0100980 unsigned int gup_flags, struct page **pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800981 int *locked)
982{
Dave Hansencde70142016-02-12 13:01:55 -0800983 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Al Viroe7167122017-11-19 11:32:05 -0500984 pages, NULL, locked,
Lorenzo Stoakes3b913172016-10-13 01:20:14 +0100985 gup_flags | FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800986}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200987EXPORT_SYMBOL(get_user_pages_locked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800988
989/*
990 * get_user_pages_unlocked() is suitable to replace the form:
991 *
992 * down_read(&mm->mmap_sem);
993 * get_user_pages(tsk, mm, ..., pages, NULL);
994 * up_read(&mm->mmap_sem);
995 *
996 * with:
997 *
998 * get_user_pages_unlocked(tsk, mm, ..., pages);
999 *
1000 * It is functionally equivalent to get_user_pages_fast so
Lorenzo Stoakes80a79512016-12-12 16:42:46 -08001001 * get_user_pages_fast should be used instead if specific gup_flags
1002 * (e.g. FOLL_FORCE) are not required.
Andrea Arcangelif0818f42015-02-11 15:27:17 -08001003 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001004long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakesc1641542016-10-13 01:20:13 +01001005 struct page **pages, unsigned int gup_flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -08001006{
Al Viroc803c9c2017-11-18 14:17:46 -05001007 struct mm_struct *mm = current->mm;
1008 int locked = 1;
1009 long ret;
1010
1011 down_read(&mm->mmap_sem);
1012 ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
Al Viroe7167122017-11-19 11:32:05 -05001013 &locked, gup_flags | FOLL_TOUCH);
Al Viroc803c9c2017-11-18 14:17:46 -05001014 if (locked)
1015 up_read(&mm->mmap_sem);
1016 return ret;
Andrea Arcangelif0818f42015-02-11 15:27:17 -08001017}
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001018EXPORT_SYMBOL(get_user_pages_unlocked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -08001019
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001020/*
Dave Hansen1e987792016-02-12 13:01:54 -08001021 * get_user_pages_remote() - pin user pages in memory
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001022 * @tsk: the task_struct to use for page fault accounting, or
1023 * NULL if faults are not to be recorded.
1024 * @mm: mm_struct of target mm
1025 * @start: starting user address
1026 * @nr_pages: number of pages from start to pin
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +01001027 * @gup_flags: flags modifying lookup behaviour
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001028 * @pages: array that receives pointers to the pages pinned.
1029 * Should be at least nr_pages long. Or NULL, if caller
1030 * only intends to ensure the pages are faulted in.
1031 * @vmas: array of pointers to vmas corresponding to each page.
1032 * Or NULL if the caller does not require them.
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -08001033 * @locked: pointer to lock flag indicating whether lock is held and
1034 * subsequently whether VM_FAULT_RETRY functionality can be
1035 * utilised. Lock must initially be held.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001036 *
1037 * Returns number of pages pinned. This may be fewer than the number
1038 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1039 * were pinned, returns -errno. Each page returned must be released
1040 * with a put_page() call when it is finished with. vmas will only
1041 * remain valid while mmap_sem is held.
1042 *
1043 * Must be called with mmap_sem held for read or write.
1044 *
1045 * get_user_pages walks a process's page tables and takes a reference to
1046 * each struct page that each user address corresponds to at a given
1047 * instant. That is, it takes the page that would be accessed if a user
1048 * thread accesses the given user virtual address at that instant.
1049 *
1050 * This does not guarantee that the page exists in the user mappings when
1051 * get_user_pages returns, and there may even be a completely different
1052 * page there in some cases (eg. if mmapped pagecache has been invalidated
1053 * and subsequently re faulted). However it does guarantee that the page
1054 * won't be freed completely. And mostly callers simply care that the page
1055 * contains data that was valid *at some point in time*. Typically, an IO
1056 * or similar operation cannot guarantee anything stronger anyway because
1057 * locks can't be held over the syscall boundary.
1058 *
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +01001059 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1060 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1061 * be called after the page is finished with, and before put_page is called.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001062 *
1063 * get_user_pages is typically used for fewer-copy IO operations, to get a
1064 * handle on the memory by some means other than accesses via the user virtual
1065 * addresses. The pages may be submitted for DMA to devices or accessed via
1066 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1067 * use the correct cache flushing APIs.
1068 *
1069 * See also get_user_pages_fast, for performance critical applications.
Andrea Arcangelif0818f42015-02-11 15:27:17 -08001070 *
1071 * get_user_pages should be phased out in favor of
1072 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1073 * should use get_user_pages because it cannot pass
1074 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001075 */
Dave Hansen1e987792016-02-12 13:01:54 -08001076long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1077 unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +01001078 unsigned int gup_flags, struct page **pages,
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -08001079 struct vm_area_struct **vmas, int *locked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001080{
Lorenzo Stoakes859110d2016-10-13 01:20:11 +01001081 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
Al Viroe7167122017-11-19 11:32:05 -05001082 locked,
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +01001083 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
Dave Hansen1e987792016-02-12 13:01:54 -08001084}
1085EXPORT_SYMBOL(get_user_pages_remote);
1086
1087/*
Dave Hansend4edcf02016-02-12 13:01:56 -08001088 * This is the same as get_user_pages_remote(), just with a
1089 * less-flexible calling convention where we assume that the task
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -08001090 * and mm being operated on are the current task's and don't allow
1091 * passing of a locked parameter. We also obviously don't pass
1092 * FOLL_REMOTE in here.
Dave Hansen1e987792016-02-12 13:01:54 -08001093 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001094long get_user_pages(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes768ae302016-10-13 01:20:16 +01001095 unsigned int gup_flags, struct page **pages,
Dave Hansen1e987792016-02-12 13:01:54 -08001096 struct vm_area_struct **vmas)
1097{
Dave Hansencde70142016-02-12 13:01:55 -08001098 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Al Viroe7167122017-11-19 11:32:05 -05001099 pages, vmas, NULL,
Lorenzo Stoakes768ae302016-10-13 01:20:16 +01001100 gup_flags | FOLL_TOUCH);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001101}
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001102EXPORT_SYMBOL(get_user_pages);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001103
Dan Williams2bb6d282017-11-29 16:10:35 -08001104#ifdef CONFIG_FS_DAX
1105/*
1106 * This is the same as get_user_pages() in that it assumes we are
1107 * operating on the current task's mm, but it goes further to validate
1108 * that the vmas associated with the address range are suitable for
1109 * longterm elevated page reference counts. For example, filesystem-dax
1110 * mappings are subject to the lifetime enforced by the filesystem and
1111 * we need guarantees that longterm users like RDMA and V4L2 only
1112 * establish mappings that have a kernel enforced revocation mechanism.
1113 *
1114 * "longterm" == userspace controlled elevated page count lifetime.
1115 * Contrast this to iov_iter_get_pages() usages which are transient.
1116 */
1117long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
1118 unsigned int gup_flags, struct page **pages,
1119 struct vm_area_struct **vmas_arg)
1120{
1121 struct vm_area_struct **vmas = vmas_arg;
1122 struct vm_area_struct *vma_prev = NULL;
1123 long rc, i;
1124
1125 if (!pages)
1126 return -EINVAL;
1127
1128 if (!vmas) {
1129 vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *),
1130 GFP_KERNEL);
1131 if (!vmas)
1132 return -ENOMEM;
1133 }
1134
1135 rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas);
1136
1137 for (i = 0; i < rc; i++) {
1138 struct vm_area_struct *vma = vmas[i];
1139
1140 if (vma == vma_prev)
1141 continue;
1142
1143 vma_prev = vma;
1144
1145 if (vma_is_fsdax(vma))
1146 break;
1147 }
1148
1149 /*
1150 * Either get_user_pages() failed, or the vma validation
1151 * succeeded, in either case we don't need to put_page() before
1152 * returning.
1153 */
1154 if (i >= rc)
1155 goto out;
1156
1157 for (i = 0; i < rc; i++)
1158 put_page(pages[i]);
1159 rc = -EOPNOTSUPP;
1160out:
1161 if (vmas != vmas_arg)
1162 kfree(vmas);
1163 return rc;
1164}
1165EXPORT_SYMBOL(get_user_pages_longterm);
1166#endif /* CONFIG_FS_DAX */
1167
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001168/**
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001169 * populate_vma_page_range() - populate a range of pages in the vma.
1170 * @vma: target vma
1171 * @start: start address
1172 * @end: end address
1173 * @nonblocking:
1174 *
1175 * This takes care of mlocking the pages too if VM_LOCKED is set.
1176 *
1177 * return 0 on success, negative error code on error.
1178 *
1179 * vma->vm_mm->mmap_sem must be held.
1180 *
1181 * If @nonblocking is NULL, it may be held for read or write and will
1182 * be unperturbed.
1183 *
1184 * If @nonblocking is non-NULL, it must held for read only and may be
1185 * released. If it's released, *@nonblocking will be set to 0.
1186 */
1187long populate_vma_page_range(struct vm_area_struct *vma,
1188 unsigned long start, unsigned long end, int *nonblocking)
1189{
1190 struct mm_struct *mm = vma->vm_mm;
1191 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1192 int gup_flags;
1193
1194 VM_BUG_ON(start & ~PAGE_MASK);
1195 VM_BUG_ON(end & ~PAGE_MASK);
1196 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1197 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1198 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1199
Eric B Munsonde60f5f2015-11-05 18:51:36 -08001200 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1201 if (vma->vm_flags & VM_LOCKONFAULT)
1202 gup_flags &= ~FOLL_POPULATE;
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001203 /*
1204 * We want to touch writable mappings with a write fault in order
1205 * to break COW, except for shared mappings because these don't COW
1206 * and we would not want to dirty them for nothing.
1207 */
1208 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1209 gup_flags |= FOLL_WRITE;
1210
1211 /*
1212 * We want mlock to succeed for regions that have any permissions
1213 * other than PROT_NONE.
1214 */
1215 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1216 gup_flags |= FOLL_FORCE;
1217
1218 /*
1219 * We made sure addr is within a VMA, so the following will
1220 * not result in a stack expansion that recurses back here.
1221 */
1222 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1223 NULL, NULL, nonblocking);
1224}
1225
1226/*
1227 * __mm_populate - populate and/or mlock pages within a range of address space.
1228 *
1229 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1230 * flags. VMAs must be already marked with the desired vm_flags, and
1231 * mmap_sem must not be held.
1232 */
1233int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1234{
1235 struct mm_struct *mm = current->mm;
1236 unsigned long end, nstart, nend;
1237 struct vm_area_struct *vma = NULL;
1238 int locked = 0;
1239 long ret = 0;
1240
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001241 end = start + len;
1242
1243 for (nstart = start; nstart < end; nstart = nend) {
1244 /*
1245 * We want to fault in pages for [nstart; end) address range.
1246 * Find first corresponding VMA.
1247 */
1248 if (!locked) {
1249 locked = 1;
1250 down_read(&mm->mmap_sem);
1251 vma = find_vma(mm, nstart);
1252 } else if (nstart >= vma->vm_end)
1253 vma = vma->vm_next;
1254 if (!vma || vma->vm_start >= end)
1255 break;
1256 /*
1257 * Set [nstart; nend) to intersection of desired address
1258 * range with the first VMA. Also, skip undesirable VMA types.
1259 */
1260 nend = min(end, vma->vm_end);
1261 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1262 continue;
1263 if (nstart < vma->vm_start)
1264 nstart = vma->vm_start;
1265 /*
1266 * Now fault in a range of pages. populate_vma_page_range()
1267 * double checks the vma flags, so that it won't mlock pages
1268 * if the vma was already munlocked.
1269 */
1270 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1271 if (ret < 0) {
1272 if (ignore_errors) {
1273 ret = 0;
1274 continue; /* continue at next VMA */
1275 }
1276 break;
1277 }
1278 nend = nstart + ret * PAGE_SIZE;
1279 ret = 0;
1280 }
1281 if (locked)
1282 up_read(&mm->mmap_sem);
1283 return ret; /* 0 or negative error code */
1284}
1285
1286/**
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001287 * get_dump_page() - pin user page in memory while writing it to core dump
1288 * @addr: user address
1289 *
1290 * Returns struct page pointer of user page pinned for dump,
Kirill A. Shutemovea1754a2016-04-01 15:29:48 +03001291 * to be freed afterwards by put_page().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001292 *
1293 * Returns NULL on any kind of failure - a hole must then be inserted into
1294 * the corefile, to preserve alignment with its headers; and also returns
1295 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1296 * allowing a hole to be left in the corefile to save diskspace.
1297 *
1298 * Called without mmap_sem, but after all other threads have been killed.
1299 */
1300#ifdef CONFIG_ELF_CORE
1301struct page *get_dump_page(unsigned long addr)
1302{
1303 struct vm_area_struct *vma;
1304 struct page *page;
1305
1306 if (__get_user_pages(current, current->mm, addr, 1,
1307 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1308 NULL) < 1)
1309 return NULL;
1310 flush_cache_page(vma, addr, page_to_pfn(page));
1311 return page;
1312}
1313#endif /* CONFIG_ELF_CORE */
Steve Capper2667f502014-10-09 15:29:14 -07001314
1315/*
Kirill A. Shutemove5855132017-06-06 14:31:20 +03001316 * Generic Fast GUP
Steve Capper2667f502014-10-09 15:29:14 -07001317 *
1318 * get_user_pages_fast attempts to pin user pages by walking the page
1319 * tables directly and avoids taking locks. Thus the walker needs to be
1320 * protected from page table pages being freed from under it, and should
1321 * block any THP splits.
1322 *
1323 * One way to achieve this is to have the walker disable interrupts, and
1324 * rely on IPIs from the TLB flushing code blocking before the page table
1325 * pages are freed. This is unsuitable for architectures that do not need
1326 * to broadcast an IPI when invalidating TLBs.
1327 *
1328 * Another way to achieve this is to batch up page table containing pages
1329 * belonging to more than one mm_user, then rcu_sched a callback to free those
1330 * pages. Disabling interrupts will allow the fast_gup walker to both block
1331 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1332 * (which is a relatively rare event). The code below adopts this strategy.
1333 *
1334 * Before activating this code, please be aware that the following assumptions
1335 * are currently made:
1336 *
Kirill A. Shutemove5855132017-06-06 14:31:20 +03001337 * *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
1338 * free pages containing page tables or TLB flushing requires IPI broadcast.
Steve Capper2667f502014-10-09 15:29:14 -07001339 *
Steve Capper2667f502014-10-09 15:29:14 -07001340 * *) ptes can be read atomically by the architecture.
1341 *
1342 * *) access_ok is sufficient to validate userspace address ranges.
1343 *
1344 * The last two assumptions can be relaxed by the addition of helper functions.
1345 *
1346 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1347 */
Kirill A. Shutemove5855132017-06-06 14:31:20 +03001348#ifdef CONFIG_HAVE_GENERIC_GUP
Steve Capper2667f502014-10-09 15:29:14 -07001349
Kirill A. Shutemov0005d202017-03-16 18:26:51 +03001350#ifndef gup_get_pte
1351/*
1352 * We assume that the PTE can be read atomically. If this is not the case for
1353 * your architecture, please provide the helper.
1354 */
1355static inline pte_t gup_get_pte(pte_t *ptep)
1356{
1357 return READ_ONCE(*ptep);
1358}
1359#endif
1360
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001361static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
1362{
1363 while ((*nr) - nr_start) {
1364 struct page *page = pages[--(*nr)];
1365
1366 ClearPageReferenced(page);
1367 put_page(page);
1368 }
1369}
1370
Laurent Dufour3010a5e2018-06-07 17:06:08 -07001371#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
Steve Capper2667f502014-10-09 15:29:14 -07001372static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1373 int write, struct page **pages, int *nr)
1374{
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001375 struct dev_pagemap *pgmap = NULL;
1376 int nr_start = *nr, ret = 0;
Steve Capper2667f502014-10-09 15:29:14 -07001377 pte_t *ptep, *ptem;
Steve Capper2667f502014-10-09 15:29:14 -07001378
1379 ptem = ptep = pte_offset_map(&pmd, addr);
1380 do {
Kirill A. Shutemov0005d202017-03-16 18:26:51 +03001381 pte_t pte = gup_get_pte(ptep);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001382 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001383
1384 /*
1385 * Similar to the PMD case below, NUMA hinting must take slow
Mel Gorman8a0516e2015-02-12 14:58:22 -08001386 * path using the pte_protnone check.
Steve Capper2667f502014-10-09 15:29:14 -07001387 */
Kirill A. Shutemove7884f82017-03-16 18:26:50 +03001388 if (pte_protnone(pte))
1389 goto pte_unmap;
1390
1391 if (!pte_access_permitted(pte, write))
1392 goto pte_unmap;
1393
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001394 if (pte_devmap(pte)) {
1395 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
1396 if (unlikely(!pgmap)) {
1397 undo_dev_pagemap(nr, nr_start, pages);
1398 goto pte_unmap;
1399 }
1400 } else if (pte_special(pte))
Steve Capper2667f502014-10-09 15:29:14 -07001401 goto pte_unmap;
1402
1403 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1404 page = pte_page(pte);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001405 head = compound_head(page);
Steve Capper2667f502014-10-09 15:29:14 -07001406
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001407 if (!page_cache_get_speculative(head))
Steve Capper2667f502014-10-09 15:29:14 -07001408 goto pte_unmap;
1409
1410 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001411 put_page(head);
Steve Capper2667f502014-10-09 15:29:14 -07001412 goto pte_unmap;
1413 }
1414
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001415 VM_BUG_ON_PAGE(compound_head(page) != head, page);
Kirill A. Shutemove9348052017-03-16 18:26:52 +03001416
1417 SetPageReferenced(page);
Steve Capper2667f502014-10-09 15:29:14 -07001418 pages[*nr] = page;
1419 (*nr)++;
1420
1421 } while (ptep++, addr += PAGE_SIZE, addr != end);
1422
1423 ret = 1;
1424
1425pte_unmap:
Christoph Hellwig832d7aa2017-12-29 08:54:01 +01001426 if (pgmap)
1427 put_dev_pagemap(pgmap);
Steve Capper2667f502014-10-09 15:29:14 -07001428 pte_unmap(ptem);
1429 return ret;
1430}
1431#else
1432
1433/*
1434 * If we can't determine whether or not a pte is special, then fail immediately
1435 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1436 * to be special.
1437 *
1438 * For a futex to be placed on a THP tail page, get_futex_key requires a
1439 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1440 * useful to have gup_huge_pmd even if we can't operate on ptes.
1441 */
1442static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1443 int write, struct page **pages, int *nr)
1444{
1445 return 0;
1446}
Laurent Dufour3010a5e2018-06-07 17:06:08 -07001447#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
Steve Capper2667f502014-10-09 15:29:14 -07001448
Oliver O'Halloran09180ca2017-09-06 16:20:58 -07001449#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001450static int __gup_device_huge(unsigned long pfn, unsigned long addr,
1451 unsigned long end, struct page **pages, int *nr)
1452{
1453 int nr_start = *nr;
1454 struct dev_pagemap *pgmap = NULL;
1455
1456 do {
1457 struct page *page = pfn_to_page(pfn);
1458
1459 pgmap = get_dev_pagemap(pfn, pgmap);
1460 if (unlikely(!pgmap)) {
1461 undo_dev_pagemap(nr, nr_start, pages);
1462 return 0;
1463 }
1464 SetPageReferenced(page);
1465 pages[*nr] = page;
1466 get_page(page);
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001467 (*nr)++;
1468 pfn++;
1469 } while (addr += PAGE_SIZE, addr != end);
Christoph Hellwig832d7aa2017-12-29 08:54:01 +01001470
1471 if (pgmap)
1472 put_dev_pagemap(pgmap);
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001473 return 1;
1474}
1475
Dan Williamsa9b6de72018-04-19 21:32:19 -07001476static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001477 unsigned long end, struct page **pages, int *nr)
1478{
1479 unsigned long fault_pfn;
Dan Williamsa9b6de72018-04-19 21:32:19 -07001480 int nr_start = *nr;
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001481
Dan Williamsa9b6de72018-04-19 21:32:19 -07001482 fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1483 if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
1484 return 0;
1485
1486 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1487 undo_dev_pagemap(nr, nr_start, pages);
1488 return 0;
1489 }
1490 return 1;
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001491}
1492
Dan Williamsa9b6de72018-04-19 21:32:19 -07001493static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001494 unsigned long end, struct page **pages, int *nr)
1495{
1496 unsigned long fault_pfn;
Dan Williamsa9b6de72018-04-19 21:32:19 -07001497 int nr_start = *nr;
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001498
Dan Williamsa9b6de72018-04-19 21:32:19 -07001499 fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1500 if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
1501 return 0;
1502
1503 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1504 undo_dev_pagemap(nr, nr_start, pages);
1505 return 0;
1506 }
1507 return 1;
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001508}
1509#else
Dan Williamsa9b6de72018-04-19 21:32:19 -07001510static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001511 unsigned long end, struct page **pages, int *nr)
1512{
1513 BUILD_BUG();
1514 return 0;
1515}
1516
Dan Williamsa9b6de72018-04-19 21:32:19 -07001517static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001518 unsigned long end, struct page **pages, int *nr)
1519{
1520 BUILD_BUG();
1521 return 0;
1522}
1523#endif
1524
Steve Capper2667f502014-10-09 15:29:14 -07001525static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1526 unsigned long end, int write, struct page **pages, int *nr)
1527{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001528 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001529 int refs;
1530
Kirill A. Shutemove7884f82017-03-16 18:26:50 +03001531 if (!pmd_access_permitted(orig, write))
Steve Capper2667f502014-10-09 15:29:14 -07001532 return 0;
1533
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001534 if (pmd_devmap(orig))
Dan Williamsa9b6de72018-04-19 21:32:19 -07001535 return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001536
Steve Capper2667f502014-10-09 15:29:14 -07001537 refs = 0;
Punit Agrawald63206e2017-07-06 15:39:39 -07001538 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001539 do {
Steve Capper2667f502014-10-09 15:29:14 -07001540 pages[*nr] = page;
1541 (*nr)++;
1542 page++;
1543 refs++;
1544 } while (addr += PAGE_SIZE, addr != end);
1545
Punit Agrawald63206e2017-07-06 15:39:39 -07001546 head = compound_head(pmd_page(orig));
Steve Capper2667f502014-10-09 15:29:14 -07001547 if (!page_cache_add_speculative(head, refs)) {
1548 *nr -= refs;
1549 return 0;
1550 }
1551
1552 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1553 *nr -= refs;
1554 while (refs--)
1555 put_page(head);
1556 return 0;
1557 }
1558
Kirill A. Shutemove9348052017-03-16 18:26:52 +03001559 SetPageReferenced(head);
Steve Capper2667f502014-10-09 15:29:14 -07001560 return 1;
1561}
1562
1563static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1564 unsigned long end, int write, struct page **pages, int *nr)
1565{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001566 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001567 int refs;
1568
Kirill A. Shutemove7884f82017-03-16 18:26:50 +03001569 if (!pud_access_permitted(orig, write))
Steve Capper2667f502014-10-09 15:29:14 -07001570 return 0;
1571
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001572 if (pud_devmap(orig))
Dan Williamsa9b6de72018-04-19 21:32:19 -07001573 return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001574
Steve Capper2667f502014-10-09 15:29:14 -07001575 refs = 0;
Punit Agrawald63206e2017-07-06 15:39:39 -07001576 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001577 do {
Steve Capper2667f502014-10-09 15:29:14 -07001578 pages[*nr] = page;
1579 (*nr)++;
1580 page++;
1581 refs++;
1582 } while (addr += PAGE_SIZE, addr != end);
1583
Punit Agrawald63206e2017-07-06 15:39:39 -07001584 head = compound_head(pud_page(orig));
Steve Capper2667f502014-10-09 15:29:14 -07001585 if (!page_cache_add_speculative(head, refs)) {
1586 *nr -= refs;
1587 return 0;
1588 }
1589
1590 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1591 *nr -= refs;
1592 while (refs--)
1593 put_page(head);
1594 return 0;
1595 }
1596
Kirill A. Shutemove9348052017-03-16 18:26:52 +03001597 SetPageReferenced(head);
Steve Capper2667f502014-10-09 15:29:14 -07001598 return 1;
1599}
1600
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301601static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1602 unsigned long end, int write,
1603 struct page **pages, int *nr)
1604{
1605 int refs;
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001606 struct page *head, *page;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301607
Kirill A. Shutemove7884f82017-03-16 18:26:50 +03001608 if (!pgd_access_permitted(orig, write))
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301609 return 0;
1610
Kirill A. Shutemovb59f65f2017-03-16 18:26:53 +03001611 BUILD_BUG_ON(pgd_devmap(orig));
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301612 refs = 0;
Punit Agrawald63206e2017-07-06 15:39:39 -07001613 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301614 do {
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301615 pages[*nr] = page;
1616 (*nr)++;
1617 page++;
1618 refs++;
1619 } while (addr += PAGE_SIZE, addr != end);
1620
Punit Agrawald63206e2017-07-06 15:39:39 -07001621 head = compound_head(pgd_page(orig));
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301622 if (!page_cache_add_speculative(head, refs)) {
1623 *nr -= refs;
1624 return 0;
1625 }
1626
1627 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1628 *nr -= refs;
1629 while (refs--)
1630 put_page(head);
1631 return 0;
1632 }
1633
Kirill A. Shutemove9348052017-03-16 18:26:52 +03001634 SetPageReferenced(head);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301635 return 1;
1636}
1637
Steve Capper2667f502014-10-09 15:29:14 -07001638static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1639 int write, struct page **pages, int *nr)
1640{
1641 unsigned long next;
1642 pmd_t *pmdp;
1643
1644 pmdp = pmd_offset(&pud, addr);
1645 do {
Christian Borntraeger38c5ce92015-01-06 22:54:46 +01001646 pmd_t pmd = READ_ONCE(*pmdp);
Steve Capper2667f502014-10-09 15:29:14 -07001647
1648 next = pmd_addr_end(addr, end);
Zi Yan84c3fc42017-09-08 16:11:01 -07001649 if (!pmd_present(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001650 return 0;
1651
1652 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1653 /*
1654 * NUMA hinting faults need to be handled in the GUP
1655 * slowpath for accounting purposes and so that they
1656 * can be serialised against THP migration.
1657 */
Mel Gorman8a0516e2015-02-12 14:58:22 -08001658 if (pmd_protnone(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001659 return 0;
1660
1661 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1662 pages, nr))
1663 return 0;
1664
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301665 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1666 /*
1667 * architecture have different format for hugetlbfs
1668 * pmd format and THP pmd format
1669 */
1670 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1671 PMD_SHIFT, next, write, pages, nr))
1672 return 0;
Steve Capper2667f502014-10-09 15:29:14 -07001673 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
Mario Leinweber29231172018-04-05 16:24:18 -07001674 return 0;
Steve Capper2667f502014-10-09 15:29:14 -07001675 } while (pmdp++, addr = next, addr != end);
1676
1677 return 1;
1678}
1679
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001680static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301681 int write, struct page **pages, int *nr)
Steve Capper2667f502014-10-09 15:29:14 -07001682{
1683 unsigned long next;
1684 pud_t *pudp;
1685
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001686 pudp = pud_offset(&p4d, addr);
Steve Capper2667f502014-10-09 15:29:14 -07001687 do {
Christian Borntraegere37c6982014-12-07 21:41:33 +01001688 pud_t pud = READ_ONCE(*pudp);
Steve Capper2667f502014-10-09 15:29:14 -07001689
1690 next = pud_addr_end(addr, end);
1691 if (pud_none(pud))
1692 return 0;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301693 if (unlikely(pud_huge(pud))) {
Steve Capper2667f502014-10-09 15:29:14 -07001694 if (!gup_huge_pud(pud, pudp, addr, next, write,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301695 pages, nr))
1696 return 0;
1697 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1698 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1699 PUD_SHIFT, next, write, pages, nr))
Steve Capper2667f502014-10-09 15:29:14 -07001700 return 0;
1701 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1702 return 0;
1703 } while (pudp++, addr = next, addr != end);
1704
1705 return 1;
1706}
1707
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001708static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
1709 int write, struct page **pages, int *nr)
1710{
1711 unsigned long next;
1712 p4d_t *p4dp;
1713
1714 p4dp = p4d_offset(&pgd, addr);
1715 do {
1716 p4d_t p4d = READ_ONCE(*p4dp);
1717
1718 next = p4d_addr_end(addr, end);
1719 if (p4d_none(p4d))
1720 return 0;
1721 BUILD_BUG_ON(p4d_huge(p4d));
1722 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
1723 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
1724 P4D_SHIFT, next, write, pages, nr))
1725 return 0;
Kirill A. Shutemovce70df02017-03-13 08:22:13 +03001726 } else if (!gup_pud_range(p4d, addr, next, write, pages, nr))
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001727 return 0;
1728 } while (p4dp++, addr = next, addr != end);
1729
1730 return 1;
1731}
1732
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001733static void gup_pgd_range(unsigned long addr, unsigned long end,
1734 int write, struct page **pages, int *nr)
1735{
1736 unsigned long next;
1737 pgd_t *pgdp;
1738
1739 pgdp = pgd_offset(current->mm, addr);
1740 do {
1741 pgd_t pgd = READ_ONCE(*pgdp);
1742
1743 next = pgd_addr_end(addr, end);
1744 if (pgd_none(pgd))
1745 return;
1746 if (unlikely(pgd_huge(pgd))) {
1747 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1748 pages, nr))
1749 return;
1750 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1751 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1752 PGDIR_SHIFT, next, write, pages, nr))
1753 return;
1754 } else if (!gup_p4d_range(pgd, addr, next, write, pages, nr))
1755 return;
1756 } while (pgdp++, addr = next, addr != end);
1757}
1758
1759#ifndef gup_fast_permitted
1760/*
1761 * Check if it's allowed to use __get_user_pages_fast() for the range, or
1762 * we need to fall back to the slow version:
1763 */
1764bool gup_fast_permitted(unsigned long start, int nr_pages, int write)
1765{
1766 unsigned long len, end;
1767
1768 len = (unsigned long) nr_pages << PAGE_SHIFT;
1769 end = start + len;
1770 return end >= start;
1771}
1772#endif
1773
Steve Capper2667f502014-10-09 15:29:14 -07001774/*
1775 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
Michael S. Tsirkind0811072018-04-13 15:35:23 -07001776 * the regular GUP.
1777 * Note a difference with get_user_pages_fast: this always returns the
1778 * number of pages pinned, 0 if no pages were pinned.
Steve Capper2667f502014-10-09 15:29:14 -07001779 */
1780int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1781 struct page **pages)
1782{
Steve Capper2667f502014-10-09 15:29:14 -07001783 unsigned long addr, len, end;
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001784 unsigned long flags;
Steve Capper2667f502014-10-09 15:29:14 -07001785 int nr = 0;
1786
1787 start &= PAGE_MASK;
1788 addr = start;
1789 len = (unsigned long) nr_pages << PAGE_SHIFT;
1790 end = start + len;
1791
1792 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
Arnd Bergmannaa2369f2017-05-03 14:56:12 -07001793 (void __user *)start, len)))
Steve Capper2667f502014-10-09 15:29:14 -07001794 return 0;
1795
1796 /*
1797 * Disable interrupts. We use the nested form as we can already have
1798 * interrupts disabled by get_futex_key.
1799 *
1800 * With interrupts disabled, we block page table pages from being
1801 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1802 * for more details.
1803 *
1804 * We do not adopt an rcu_read_lock(.) here as we also want to
1805 * block IPIs that come from THPs splitting.
1806 */
1807
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001808 if (gup_fast_permitted(start, nr_pages, write)) {
1809 local_irq_save(flags);
1810 gup_pgd_range(addr, end, write, pages, &nr);
1811 local_irq_restore(flags);
1812 }
Steve Capper2667f502014-10-09 15:29:14 -07001813
1814 return nr;
1815}
1816
1817/**
1818 * get_user_pages_fast() - pin user pages in memory
1819 * @start: starting user address
1820 * @nr_pages: number of pages from start to pin
1821 * @write: whether pages will be written to
1822 * @pages: array that receives pointers to the pages pinned.
1823 * Should be at least nr_pages long.
1824 *
1825 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1826 * If not successful, it will fall back to taking the lock and
1827 * calling get_user_pages().
1828 *
1829 * Returns number of pages pinned. This may be fewer than the number
1830 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1831 * were pinned, returns -errno.
1832 */
1833int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1834 struct page **pages)
1835{
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001836 unsigned long addr, len, end;
Kirill A. Shutemov73e10a62017-03-16 18:26:54 +03001837 int nr = 0, ret = 0;
Steve Capper2667f502014-10-09 15:29:14 -07001838
1839 start &= PAGE_MASK;
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001840 addr = start;
1841 len = (unsigned long) nr_pages << PAGE_SHIFT;
1842 end = start + len;
1843
Michael S. Tsirkinc61611f2018-04-13 15:35:20 -07001844 if (nr_pages <= 0)
1845 return 0;
1846
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001847 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1848 (void __user *)start, len)))
Michael S. Tsirkinc61611f2018-04-13 15:35:20 -07001849 return -EFAULT;
Kirill A. Shutemov73e10a62017-03-16 18:26:54 +03001850
1851 if (gup_fast_permitted(start, nr_pages, write)) {
Kirill A. Shutemov5b65c462017-09-09 00:56:03 +03001852 local_irq_disable();
1853 gup_pgd_range(addr, end, write, pages, &nr);
1854 local_irq_enable();
Kirill A. Shutemov73e10a62017-03-16 18:26:54 +03001855 ret = nr;
1856 }
Steve Capper2667f502014-10-09 15:29:14 -07001857
1858 if (nr < nr_pages) {
1859 /* Try to get the remaining pages with get_user_pages */
1860 start += nr << PAGE_SHIFT;
1861 pages += nr;
1862
Lorenzo Stoakesc1641542016-10-13 01:20:13 +01001863 ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
1864 write ? FOLL_WRITE : 0);
Steve Capper2667f502014-10-09 15:29:14 -07001865
1866 /* Have to be a bit careful with return values */
1867 if (nr > 0) {
1868 if (ret < 0)
1869 ret = nr;
1870 else
1871 ret += nr;
1872 }
1873 }
1874
1875 return ret;
1876}
1877
Kirill A. Shutemove5855132017-06-06 14:31:20 +03001878#endif /* CONFIG_HAVE_GENERIC_GUP */