blob: c74bad1bf6e8f2423c19cb8b6c3a386272ef8252 [file] [log] [blame]
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{
69 return pte_write(pte) ||
70 ((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
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700211/**
212 * follow_page_mask - look up a page descriptor from a user-virtual address
213 * @vma: vm_area_struct mapping @address
214 * @address: virtual address to look up
215 * @flags: flags modifying lookup behaviour
216 * @page_mask: on output, *page_mask is set according to the size of the page
217 *
218 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
219 *
220 * Returns the mapped (struct page *), %NULL if no mapping exists, or
221 * an error pointer if there is a mapping to something not represented
222 * by a page descriptor (see also vm_normal_page()).
223 */
224struct page *follow_page_mask(struct vm_area_struct *vma,
225 unsigned long address, unsigned int flags,
226 unsigned int *page_mask)
227{
228 pgd_t *pgd;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300229 p4d_t *p4d;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700230 pud_t *pud;
231 pmd_t *pmd;
232 spinlock_t *ptl;
233 struct page *page;
234 struct mm_struct *mm = vma->vm_mm;
235
236 *page_mask = 0;
237
238 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
239 if (!IS_ERR(page)) {
240 BUG_ON(flags & FOLL_GET);
241 return page;
242 }
243
244 pgd = pgd_offset(mm, address);
245 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
246 return no_page_table(vma, flags);
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300247 p4d = p4d_offset(pgd, address);
248 if (p4d_none(*p4d))
249 return no_page_table(vma, flags);
250 BUILD_BUG_ON(p4d_huge(*p4d));
251 if (unlikely(p4d_bad(*p4d)))
252 return no_page_table(vma, flags);
253 pud = pud_offset(p4d, address);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700254 if (pud_none(*pud))
255 return no_page_table(vma, flags);
256 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800257 page = follow_huge_pud(mm, address, pud, flags);
258 if (page)
259 return page;
260 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700261 }
Matthew Wilcoxa00cc7d2017-02-24 14:57:02 -0800262 if (pud_devmap(*pud)) {
263 ptl = pud_lock(mm, pud);
264 page = follow_devmap_pud(vma, address, pud, flags);
265 spin_unlock(ptl);
266 if (page)
267 return page;
268 }
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700269 if (unlikely(pud_bad(*pud)))
270 return no_page_table(vma, flags);
271
272 pmd = pmd_offset(pud, address);
273 if (pmd_none(*pmd))
274 return no_page_table(vma, flags);
275 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800276 page = follow_huge_pmd(mm, address, pmd, flags);
277 if (page)
278 return page;
279 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700280 }
Dan Williams3565fce2016-01-15 16:56:55 -0800281 if (pmd_devmap(*pmd)) {
282 ptl = pmd_lock(mm, pmd);
283 page = follow_devmap_pmd(vma, address, pmd, flags);
284 spin_unlock(ptl);
285 if (page)
286 return page;
287 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800288 if (likely(!pmd_trans_huge(*pmd)))
289 return follow_page_pte(vma, address, pmd, flags);
290
Aneesh Kumar K.Vdb08f202017-02-24 14:59:53 -0800291 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
292 return no_page_table(vma, flags);
293
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800294 ptl = pmd_lock(mm, pmd);
295 if (unlikely(!pmd_trans_huge(*pmd))) {
296 spin_unlock(ptl);
297 return follow_page_pte(vma, address, pmd, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700298 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800299 if (flags & FOLL_SPLIT) {
300 int ret;
301 page = pmd_page(*pmd);
302 if (is_huge_zero_page(page)) {
303 spin_unlock(ptl);
304 ret = 0;
Kirill A. Shutemov78ddc532016-01-15 16:52:42 -0800305 split_huge_pmd(vma, pmd, address);
Naoya Horiguchi337d9ab2016-07-26 15:24:03 -0700306 if (pmd_trans_unstable(pmd))
307 ret = -EBUSY;
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800308 } else {
309 get_page(page);
310 spin_unlock(ptl);
311 lock_page(page);
312 ret = split_huge_page(page);
313 unlock_page(page);
314 put_page(page);
Kirill A. Shutemovbaa355f2016-07-26 15:25:51 -0700315 if (pmd_none(*pmd))
316 return no_page_table(vma, flags);
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800317 }
318
319 return ret ? ERR_PTR(ret) :
320 follow_page_pte(vma, address, pmd, flags);
321 }
322
323 page = follow_trans_huge_pmd(vma, address, pmd, flags);
324 spin_unlock(ptl);
325 *page_mask = HPAGE_PMD_NR - 1;
326 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700327}
328
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700329static int get_gate_page(struct mm_struct *mm, unsigned long address,
330 unsigned int gup_flags, struct vm_area_struct **vma,
331 struct page **page)
332{
333 pgd_t *pgd;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300334 p4d_t *p4d;
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700335 pud_t *pud;
336 pmd_t *pmd;
337 pte_t *pte;
338 int ret = -EFAULT;
339
340 /* user gate pages are read-only */
341 if (gup_flags & FOLL_WRITE)
342 return -EFAULT;
343 if (address > TASK_SIZE)
344 pgd = pgd_offset_k(address);
345 else
346 pgd = pgd_offset_gate(mm, address);
347 BUG_ON(pgd_none(*pgd));
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300348 p4d = p4d_offset(pgd, address);
349 BUG_ON(p4d_none(*p4d));
350 pud = pud_offset(p4d, address);
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700351 BUG_ON(pud_none(*pud));
352 pmd = pmd_offset(pud, address);
353 if (pmd_none(*pmd))
354 return -EFAULT;
355 VM_BUG_ON(pmd_trans_huge(*pmd));
356 pte = pte_offset_map(pmd, address);
357 if (pte_none(*pte))
358 goto unmap;
359 *vma = get_gate_vma(mm);
360 if (!page)
361 goto out;
362 *page = vm_normal_page(*vma, address, *pte);
363 if (!*page) {
364 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
365 goto unmap;
366 *page = pte_page(*pte);
367 }
368 get_page(*page);
369out:
370 ret = 0;
371unmap:
372 pte_unmap(pte);
373 return ret;
374}
375
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700376/*
377 * mmap_sem must be held on entry. If @nonblocking != NULL and
378 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
379 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
380 */
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700381static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
382 unsigned long address, unsigned int *flags, int *nonblocking)
383{
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700384 unsigned int fault_flags = 0;
385 int ret;
386
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800387 /* mlock all present pages, but do not fault in new pages */
388 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
389 return -ENOENT;
Kirill A. Shutemov84d33df2015-04-14 15:44:37 -0700390 /* For mm_populate(), just skip the stack guard page. */
391 if ((*flags & FOLL_POPULATE) &&
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700392 (stack_guard_page_start(vma, address) ||
393 stack_guard_page_end(vma, address + PAGE_SIZE)))
394 return -ENOENT;
395 if (*flags & FOLL_WRITE)
396 fault_flags |= FAULT_FLAG_WRITE;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800397 if (*flags & FOLL_REMOTE)
398 fault_flags |= FAULT_FLAG_REMOTE;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700399 if (nonblocking)
400 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
401 if (*flags & FOLL_NOWAIT)
402 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
Andres Lagar-Cavilla234b2392014-09-17 10:51:48 -0700403 if (*flags & FOLL_TRIED) {
404 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
405 fault_flags |= FAULT_FLAG_TRIED;
406 }
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700407
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700408 ret = handle_mm_fault(vma, address, fault_flags);
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700409 if (ret & VM_FAULT_ERROR) {
410 if (ret & VM_FAULT_OOM)
411 return -ENOMEM;
412 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
413 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
Linus Torvalds33692f22015-01-29 10:51:32 -0800414 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700415 return -EFAULT;
416 BUG();
417 }
418
419 if (tsk) {
420 if (ret & VM_FAULT_MAJOR)
421 tsk->maj_flt++;
422 else
423 tsk->min_flt++;
424 }
425
426 if (ret & VM_FAULT_RETRY) {
427 if (nonblocking)
428 *nonblocking = 0;
429 return -EBUSY;
430 }
431
432 /*
433 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
434 * necessary, even if maybe_mkwrite decided not to set pte_write. We
435 * can thus safely do subsequent page lookups as if they were reads.
436 * But only do so when looping for pte_write is futile: in some cases
437 * userspace may also be wanting to write to the gotten user page,
438 * which a read fault here might prevent (a readonly page might get
439 * reCOWed by userspace write).
440 */
441 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
Linus Torvalds19be0ea2016-10-13 13:07:36 -0700442 *flags |= FOLL_COW;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700443 return 0;
444}
445
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700446static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
447{
448 vm_flags_t vm_flags = vma->vm_flags;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800449 int write = (gup_flags & FOLL_WRITE);
450 int foreign = (gup_flags & FOLL_REMOTE);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700451
452 if (vm_flags & (VM_IO | VM_PFNMAP))
453 return -EFAULT;
454
Dave Hansen1b2ee122016-02-12 13:02:21 -0800455 if (write) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700456 if (!(vm_flags & VM_WRITE)) {
457 if (!(gup_flags & FOLL_FORCE))
458 return -EFAULT;
459 /*
460 * We used to let the write,force case do COW in a
461 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
462 * set a breakpoint in a read-only mapping of an
463 * executable, without corrupting the file (yet only
464 * when that file had been opened for writing!).
465 * Anon pages in shared mappings are surprising: now
466 * just reject it.
467 */
Hugh Dickins46435362016-01-30 18:03:16 -0800468 if (!is_cow_mapping(vm_flags))
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700469 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700470 }
471 } else if (!(vm_flags & VM_READ)) {
472 if (!(gup_flags & FOLL_FORCE))
473 return -EFAULT;
474 /*
475 * Is there actually any vma we can reach here which does not
476 * have VM_MAYREAD set?
477 */
478 if (!(vm_flags & VM_MAYREAD))
479 return -EFAULT;
480 }
Dave Hansend61172b2016-02-12 13:02:24 -0800481 /*
482 * gups are always data accesses, not instruction
483 * fetches, so execute=false here
484 */
485 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800486 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700487 return 0;
488}
489
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700490/**
491 * __get_user_pages() - pin user pages in memory
492 * @tsk: task_struct of target task
493 * @mm: mm_struct of target mm
494 * @start: starting user address
495 * @nr_pages: number of pages from start to pin
496 * @gup_flags: flags modifying pin behaviour
497 * @pages: array that receives pointers to the pages pinned.
498 * Should be at least nr_pages long. Or NULL, if caller
499 * only intends to ensure the pages are faulted in.
500 * @vmas: array of pointers to vmas corresponding to each page.
501 * Or NULL if the caller does not require them.
502 * @nonblocking: whether waiting for disk IO or mmap_sem contention
503 *
504 * Returns number of pages pinned. This may be fewer than the number
505 * requested. If nr_pages is 0 or negative, returns 0. If no pages
506 * were pinned, returns -errno. Each page returned must be released
507 * with a put_page() call when it is finished with. vmas will only
508 * remain valid while mmap_sem is held.
509 *
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700510 * Must be called with mmap_sem held. It may be released. See below.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700511 *
512 * __get_user_pages walks a process's page tables and takes a reference to
513 * each struct page that each user address corresponds to at a given
514 * instant. That is, it takes the page that would be accessed if a user
515 * thread accesses the given user virtual address at that instant.
516 *
517 * This does not guarantee that the page exists in the user mappings when
518 * __get_user_pages returns, and there may even be a completely different
519 * page there in some cases (eg. if mmapped pagecache has been invalidated
520 * and subsequently re faulted). However it does guarantee that the page
521 * won't be freed completely. And mostly callers simply care that the page
522 * contains data that was valid *at some point in time*. Typically, an IO
523 * or similar operation cannot guarantee anything stronger anyway because
524 * locks can't be held over the syscall boundary.
525 *
526 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
527 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
528 * appropriate) must be called after the page is finished with, and
529 * before put_page is called.
530 *
531 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
532 * or mmap_sem contention, and if waiting is needed to pin all pages,
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700533 * *@nonblocking will be set to 0. Further, if @gup_flags does not
534 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
535 * this case.
536 *
537 * A caller using such a combination of @nonblocking and @gup_flags
538 * must therefore hold the mmap_sem for reading only, and recognize
539 * when it's been released. Otherwise, it must be held for either
540 * reading or writing and will not be released.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700541 *
542 * In most cases, get_user_pages or get_user_pages_fast should be used
543 * instead of __get_user_pages. __get_user_pages should be used only if
544 * you need some special @gup_flags.
545 */
Lorenzo Stoakes0d731752016-10-24 10:57:25 +0100546static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700547 unsigned long start, unsigned long nr_pages,
548 unsigned int gup_flags, struct page **pages,
549 struct vm_area_struct **vmas, int *nonblocking)
550{
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700551 long i = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700552 unsigned int page_mask;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700553 struct vm_area_struct *vma = NULL;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700554
555 if (!nr_pages)
556 return 0;
557
558 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
559
560 /*
561 * If FOLL_FORCE is set then do not force a full fault as the hinting
562 * fault information is unrelated to the reference behaviour of a task
563 * using the address space
564 */
565 if (!(gup_flags & FOLL_FORCE))
566 gup_flags |= FOLL_NUMA;
567
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700568 do {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700569 struct page *page;
570 unsigned int foll_flags = gup_flags;
571 unsigned int page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700572
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700573 /* first iteration or cross vma bound */
574 if (!vma || start >= vma->vm_end) {
575 vma = find_extend_vma(mm, start);
576 if (!vma && in_gate_area(mm, start)) {
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700577 int ret;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700578 ret = get_gate_page(mm, start & PAGE_MASK,
579 gup_flags, &vma,
580 pages ? &pages[i] : NULL);
581 if (ret)
582 return i ? : ret;
583 page_mask = 0;
584 goto next_page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700585 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700586
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700587 if (!vma || check_vma_flags(vma, gup_flags))
588 return i ? : -EFAULT;
589 if (is_vm_hugetlb_page(vma)) {
590 i = follow_hugetlb_page(mm, vma, pages, vmas,
591 &start, &nr_pages, i,
Andrea Arcangeli87ffc112017-02-22 15:43:13 -0800592 gup_flags, nonblocking);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700593 continue;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700594 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700595 }
596retry:
597 /*
598 * If we have a pending SIGKILL, don't keep faulting pages and
599 * potentially allocating memory.
600 */
601 if (unlikely(fatal_signal_pending(current)))
602 return i ? i : -ERESTARTSYS;
603 cond_resched();
604 page = follow_page_mask(vma, start, foll_flags, &page_mask);
605 if (!page) {
606 int ret;
607 ret = faultin_page(tsk, vma, start, &foll_flags,
608 nonblocking);
609 switch (ret) {
610 case 0:
611 goto retry;
612 case -EFAULT:
613 case -ENOMEM:
614 case -EHWPOISON:
615 return i ? i : ret;
616 case -EBUSY:
617 return i;
618 case -ENOENT:
619 goto next_page;
620 }
621 BUG();
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700622 } else if (PTR_ERR(page) == -EEXIST) {
623 /*
624 * Proper page table entry exists, but no corresponding
625 * struct page.
626 */
627 goto next_page;
628 } else if (IS_ERR(page)) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700629 return i ? i : PTR_ERR(page);
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700630 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700631 if (pages) {
632 pages[i] = page;
633 flush_anon_page(vma, page, start);
634 flush_dcache_page(page);
635 page_mask = 0;
636 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700637next_page:
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700638 if (vmas) {
639 vmas[i] = vma;
640 page_mask = 0;
641 }
642 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
643 if (page_increm > nr_pages)
644 page_increm = nr_pages;
645 i += page_increm;
646 start += page_increm * PAGE_SIZE;
647 nr_pages -= page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700648 } while (nr_pages);
649 return i;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700650}
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700651
Tobias Klauser771ab432016-12-12 16:41:53 -0800652static bool vma_permits_fault(struct vm_area_struct *vma,
653 unsigned int fault_flags)
Dave Hansend4925e02016-02-12 13:02:16 -0800654{
Dave Hansen1b2ee122016-02-12 13:02:21 -0800655 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
656 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
Dave Hansen33a709b2016-02-12 13:02:19 -0800657 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
Dave Hansend4925e02016-02-12 13:02:16 -0800658
659 if (!(vm_flags & vma->vm_flags))
660 return false;
661
Dave Hansen33a709b2016-02-12 13:02:19 -0800662 /*
663 * The architecture might have a hardware protection
Dave Hansen1b2ee122016-02-12 13:02:21 -0800664 * mechanism other than read/write that can deny access.
Dave Hansend61172b2016-02-12 13:02:24 -0800665 *
666 * gup always represents data access, not instruction
667 * fetches, so execute=false here:
Dave Hansen33a709b2016-02-12 13:02:19 -0800668 */
Dave Hansend61172b2016-02-12 13:02:24 -0800669 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800670 return false;
671
Dave Hansend4925e02016-02-12 13:02:16 -0800672 return true;
673}
674
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700675/*
676 * fixup_user_fault() - manually resolve a user page fault
677 * @tsk: the task_struct to use for page fault accounting, or
678 * NULL if faults are not to be recorded.
679 * @mm: mm_struct of target mm
680 * @address: user address
681 * @fault_flags:flags to pass down to handle_mm_fault()
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800682 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
683 * does not allow retry
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700684 *
685 * This is meant to be called in the specific scenario where for locking reasons
686 * we try to access user memory in atomic context (within a pagefault_disable()
687 * section), this returns -EFAULT, and we want to resolve the user fault before
688 * trying again.
689 *
690 * Typically this is meant to be used by the futex code.
691 *
692 * The main difference with get_user_pages() is that this function will
693 * unconditionally call handle_mm_fault() which will in turn perform all the
694 * necessary SW fixup of the dirty and young bits in the PTE, while
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800695 * get_user_pages() only guarantees to update these in the struct page.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700696 *
697 * This is important for some architectures where those bits also gate the
698 * access permission to the page because they are maintained in software. On
699 * such architectures, gup() will not be enough to make a subsequent access
700 * succeed.
701 *
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800702 * This function will not return with an unlocked mmap_sem. So it has not the
703 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700704 */
705int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800706 unsigned long address, unsigned int fault_flags,
707 bool *unlocked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700708{
709 struct vm_area_struct *vma;
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800710 int ret, major = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700711
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800712 if (unlocked)
713 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
714
715retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700716 vma = find_extend_vma(mm, address);
717 if (!vma || address < vma->vm_start)
718 return -EFAULT;
719
Dave Hansend4925e02016-02-12 13:02:16 -0800720 if (!vma_permits_fault(vma, fault_flags))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700721 return -EFAULT;
722
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700723 ret = handle_mm_fault(vma, address, fault_flags);
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800724 major |= ret & VM_FAULT_MAJOR;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700725 if (ret & VM_FAULT_ERROR) {
726 if (ret & VM_FAULT_OOM)
727 return -ENOMEM;
728 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
729 return -EHWPOISON;
Linus Torvalds33692f22015-01-29 10:51:32 -0800730 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700731 return -EFAULT;
732 BUG();
733 }
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800734
735 if (ret & VM_FAULT_RETRY) {
736 down_read(&mm->mmap_sem);
737 if (!(fault_flags & FAULT_FLAG_TRIED)) {
738 *unlocked = true;
739 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
740 fault_flags |= FAULT_FLAG_TRIED;
741 goto retry;
742 }
743 }
744
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700745 if (tsk) {
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800746 if (major)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700747 tsk->maj_flt++;
748 else
749 tsk->min_flt++;
750 }
751 return 0;
752}
Paolo Bonziniadd6a0c2016-06-07 17:51:18 +0200753EXPORT_SYMBOL_GPL(fixup_user_fault);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700754
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800755static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
756 struct mm_struct *mm,
757 unsigned long start,
758 unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800759 struct page **pages,
760 struct vm_area_struct **vmas,
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800761 int *locked, bool notify_drop,
762 unsigned int flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800763{
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800764 long ret, pages_done;
765 bool lock_dropped;
766
767 if (locked) {
768 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
769 BUG_ON(vmas);
770 /* check caller initialized locked */
771 BUG_ON(*locked != 1);
772 }
773
774 if (pages)
775 flags |= FOLL_GET;
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800776
777 pages_done = 0;
778 lock_dropped = false;
779 for (;;) {
780 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
781 vmas, locked);
782 if (!locked)
783 /* VM_FAULT_RETRY couldn't trigger, bypass */
784 return ret;
785
786 /* VM_FAULT_RETRY cannot return errors */
787 if (!*locked) {
788 BUG_ON(ret < 0);
789 BUG_ON(ret >= nr_pages);
790 }
791
792 if (!pages)
793 /* If it's a prefault don't insist harder */
794 return ret;
795
796 if (ret > 0) {
797 nr_pages -= ret;
798 pages_done += ret;
799 if (!nr_pages)
800 break;
801 }
802 if (*locked) {
803 /* VM_FAULT_RETRY didn't trigger */
804 if (!pages_done)
805 pages_done = ret;
806 break;
807 }
808 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
809 pages += ret;
810 start += ret << PAGE_SHIFT;
811
812 /*
813 * Repeat on the address that fired VM_FAULT_RETRY
814 * without FAULT_FLAG_ALLOW_RETRY but with
815 * FAULT_FLAG_TRIED.
816 */
817 *locked = 1;
818 lock_dropped = true;
819 down_read(&mm->mmap_sem);
820 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
821 pages, NULL, NULL);
822 if (ret != 1) {
823 BUG_ON(ret > 1);
824 if (!pages_done)
825 pages_done = ret;
826 break;
827 }
828 nr_pages--;
829 pages_done++;
830 if (!nr_pages)
831 break;
832 pages++;
833 start += PAGE_SIZE;
834 }
835 if (notify_drop && lock_dropped && *locked) {
836 /*
837 * We must let the caller know we temporarily dropped the lock
838 * and so the critical section protected by it was lost.
839 */
840 up_read(&mm->mmap_sem);
841 *locked = 0;
842 }
843 return pages_done;
844}
845
846/*
847 * We can leverage the VM_FAULT_RETRY functionality in the page fault
848 * paths better by using either get_user_pages_locked() or
849 * get_user_pages_unlocked().
850 *
851 * get_user_pages_locked() is suitable to replace the form:
852 *
853 * down_read(&mm->mmap_sem);
854 * do_something()
855 * get_user_pages(tsk, mm, ..., pages, NULL);
856 * up_read(&mm->mmap_sem);
857 *
858 * to:
859 *
860 * int locked = 1;
861 * down_read(&mm->mmap_sem);
862 * do_something()
863 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
864 * if (locked)
865 * up_read(&mm->mmap_sem);
866 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200867long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes3b913172016-10-13 01:20:14 +0100868 unsigned int gup_flags, struct page **pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800869 int *locked)
870{
Dave Hansencde70142016-02-12 13:01:55 -0800871 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Lorenzo Stoakes3b913172016-10-13 01:20:14 +0100872 pages, NULL, locked, true,
873 gup_flags | FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800874}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200875EXPORT_SYMBOL(get_user_pages_locked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800876
877/*
Lorenzo Stoakes80a79512016-12-12 16:42:46 -0800878 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows for
879 * tsk, mm to be specified.
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800880 *
881 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
Lorenzo Stoakes80a79512016-12-12 16:42:46 -0800882 * caller if required (just like with __get_user_pages). "FOLL_GET"
883 * is set implicitly if "pages" is non-NULL.
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800884 */
Lorenzo Stoakes8b7457e2016-12-14 15:06:55 -0800885static __always_inline long __get_user_pages_unlocked(struct task_struct *tsk,
886 struct mm_struct *mm, unsigned long start,
887 unsigned long nr_pages, struct page **pages,
888 unsigned int gup_flags)
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800889{
890 long ret;
891 int locked = 1;
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100892
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800893 down_read(&mm->mmap_sem);
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100894 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
895 &locked, false, gup_flags);
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800896 if (locked)
897 up_read(&mm->mmap_sem);
898 return ret;
899}
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800900
901/*
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800902 * get_user_pages_unlocked() is suitable to replace the form:
903 *
904 * down_read(&mm->mmap_sem);
905 * get_user_pages(tsk, mm, ..., pages, NULL);
906 * up_read(&mm->mmap_sem);
907 *
908 * with:
909 *
910 * get_user_pages_unlocked(tsk, mm, ..., pages);
911 *
912 * It is functionally equivalent to get_user_pages_fast so
Lorenzo Stoakes80a79512016-12-12 16:42:46 -0800913 * get_user_pages_fast should be used instead if specific gup_flags
914 * (e.g. FOLL_FORCE) are not required.
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800915 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200916long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakesc1641542016-10-13 01:20:13 +0100917 struct page **pages, unsigned int gup_flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800918{
Dave Hansencde70142016-02-12 13:01:55 -0800919 return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
Lorenzo Stoakesc1641542016-10-13 01:20:13 +0100920 pages, gup_flags | FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800921}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200922EXPORT_SYMBOL(get_user_pages_unlocked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800923
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700924/*
Dave Hansen1e987792016-02-12 13:01:54 -0800925 * get_user_pages_remote() - pin user pages in memory
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700926 * @tsk: the task_struct to use for page fault accounting, or
927 * NULL if faults are not to be recorded.
928 * @mm: mm_struct of target mm
929 * @start: starting user address
930 * @nr_pages: number of pages from start to pin
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +0100931 * @gup_flags: flags modifying lookup behaviour
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700932 * @pages: array that receives pointers to the pages pinned.
933 * Should be at least nr_pages long. Or NULL, if caller
934 * only intends to ensure the pages are faulted in.
935 * @vmas: array of pointers to vmas corresponding to each page.
936 * Or NULL if the caller does not require them.
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -0800937 * @locked: pointer to lock flag indicating whether lock is held and
938 * subsequently whether VM_FAULT_RETRY functionality can be
939 * utilised. Lock must initially be held.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700940 *
941 * Returns number of pages pinned. This may be fewer than the number
942 * requested. If nr_pages is 0 or negative, returns 0. If no pages
943 * were pinned, returns -errno. Each page returned must be released
944 * with a put_page() call when it is finished with. vmas will only
945 * remain valid while mmap_sem is held.
946 *
947 * Must be called with mmap_sem held for read or write.
948 *
949 * get_user_pages walks a process's page tables and takes a reference to
950 * each struct page that each user address corresponds to at a given
951 * instant. That is, it takes the page that would be accessed if a user
952 * thread accesses the given user virtual address at that instant.
953 *
954 * This does not guarantee that the page exists in the user mappings when
955 * get_user_pages returns, and there may even be a completely different
956 * page there in some cases (eg. if mmapped pagecache has been invalidated
957 * and subsequently re faulted). However it does guarantee that the page
958 * won't be freed completely. And mostly callers simply care that the page
959 * contains data that was valid *at some point in time*. Typically, an IO
960 * or similar operation cannot guarantee anything stronger anyway because
961 * locks can't be held over the syscall boundary.
962 *
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +0100963 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
964 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
965 * be called after the page is finished with, and before put_page is called.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700966 *
967 * get_user_pages is typically used for fewer-copy IO operations, to get a
968 * handle on the memory by some means other than accesses via the user virtual
969 * addresses. The pages may be submitted for DMA to devices or accessed via
970 * their kernel linear mapping (via the kmap APIs). Care should be taken to
971 * use the correct cache flushing APIs.
972 *
973 * See also get_user_pages_fast, for performance critical applications.
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800974 *
975 * get_user_pages should be phased out in favor of
976 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
977 * should use get_user_pages because it cannot pass
978 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700979 */
Dave Hansen1e987792016-02-12 13:01:54 -0800980long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
981 unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +0100982 unsigned int gup_flags, struct page **pages,
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -0800983 struct vm_area_struct **vmas, int *locked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700984{
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100985 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -0800986 locked, true,
Lorenzo Stoakes9beae1e2016-10-13 01:20:17 +0100987 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
Dave Hansen1e987792016-02-12 13:01:54 -0800988}
989EXPORT_SYMBOL(get_user_pages_remote);
990
991/*
Dave Hansend4edcf02016-02-12 13:01:56 -0800992 * This is the same as get_user_pages_remote(), just with a
993 * less-flexible calling convention where we assume that the task
Lorenzo Stoakes5b56d492016-12-14 15:06:52 -0800994 * and mm being operated on are the current task's and don't allow
995 * passing of a locked parameter. We also obviously don't pass
996 * FOLL_REMOTE in here.
Dave Hansen1e987792016-02-12 13:01:54 -0800997 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200998long get_user_pages(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakes768ae302016-10-13 01:20:16 +0100999 unsigned int gup_flags, struct page **pages,
Dave Hansen1e987792016-02-12 13:01:54 -08001000 struct vm_area_struct **vmas)
1001{
Dave Hansencde70142016-02-12 13:01:55 -08001002 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Lorenzo Stoakes768ae302016-10-13 01:20:16 +01001003 pages, vmas, NULL, false,
1004 gup_flags | FOLL_TOUCH);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001005}
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001006EXPORT_SYMBOL(get_user_pages);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001007
1008/**
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001009 * populate_vma_page_range() - populate a range of pages in the vma.
1010 * @vma: target vma
1011 * @start: start address
1012 * @end: end address
1013 * @nonblocking:
1014 *
1015 * This takes care of mlocking the pages too if VM_LOCKED is set.
1016 *
1017 * return 0 on success, negative error code on error.
1018 *
1019 * vma->vm_mm->mmap_sem must be held.
1020 *
1021 * If @nonblocking is NULL, it may be held for read or write and will
1022 * be unperturbed.
1023 *
1024 * If @nonblocking is non-NULL, it must held for read only and may be
1025 * released. If it's released, *@nonblocking will be set to 0.
1026 */
1027long populate_vma_page_range(struct vm_area_struct *vma,
1028 unsigned long start, unsigned long end, int *nonblocking)
1029{
1030 struct mm_struct *mm = vma->vm_mm;
1031 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1032 int gup_flags;
1033
1034 VM_BUG_ON(start & ~PAGE_MASK);
1035 VM_BUG_ON(end & ~PAGE_MASK);
1036 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1037 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1038 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1039
Eric B Munsonde60f5f2015-11-05 18:51:36 -08001040 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1041 if (vma->vm_flags & VM_LOCKONFAULT)
1042 gup_flags &= ~FOLL_POPULATE;
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001043 /*
1044 * We want to touch writable mappings with a write fault in order
1045 * to break COW, except for shared mappings because these don't COW
1046 * and we would not want to dirty them for nothing.
1047 */
1048 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1049 gup_flags |= FOLL_WRITE;
1050
1051 /*
1052 * We want mlock to succeed for regions that have any permissions
1053 * other than PROT_NONE.
1054 */
1055 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1056 gup_flags |= FOLL_FORCE;
1057
1058 /*
1059 * We made sure addr is within a VMA, so the following will
1060 * not result in a stack expansion that recurses back here.
1061 */
1062 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1063 NULL, NULL, nonblocking);
1064}
1065
1066/*
1067 * __mm_populate - populate and/or mlock pages within a range of address space.
1068 *
1069 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1070 * flags. VMAs must be already marked with the desired vm_flags, and
1071 * mmap_sem must not be held.
1072 */
1073int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1074{
1075 struct mm_struct *mm = current->mm;
1076 unsigned long end, nstart, nend;
1077 struct vm_area_struct *vma = NULL;
1078 int locked = 0;
1079 long ret = 0;
1080
1081 VM_BUG_ON(start & ~PAGE_MASK);
1082 VM_BUG_ON(len != PAGE_ALIGN(len));
1083 end = start + len;
1084
1085 for (nstart = start; nstart < end; nstart = nend) {
1086 /*
1087 * We want to fault in pages for [nstart; end) address range.
1088 * Find first corresponding VMA.
1089 */
1090 if (!locked) {
1091 locked = 1;
1092 down_read(&mm->mmap_sem);
1093 vma = find_vma(mm, nstart);
1094 } else if (nstart >= vma->vm_end)
1095 vma = vma->vm_next;
1096 if (!vma || vma->vm_start >= end)
1097 break;
1098 /*
1099 * Set [nstart; nend) to intersection of desired address
1100 * range with the first VMA. Also, skip undesirable VMA types.
1101 */
1102 nend = min(end, vma->vm_end);
1103 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1104 continue;
1105 if (nstart < vma->vm_start)
1106 nstart = vma->vm_start;
1107 /*
1108 * Now fault in a range of pages. populate_vma_page_range()
1109 * double checks the vma flags, so that it won't mlock pages
1110 * if the vma was already munlocked.
1111 */
1112 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1113 if (ret < 0) {
1114 if (ignore_errors) {
1115 ret = 0;
1116 continue; /* continue at next VMA */
1117 }
1118 break;
1119 }
1120 nend = nstart + ret * PAGE_SIZE;
1121 ret = 0;
1122 }
1123 if (locked)
1124 up_read(&mm->mmap_sem);
1125 return ret; /* 0 or negative error code */
1126}
1127
1128/**
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001129 * get_dump_page() - pin user page in memory while writing it to core dump
1130 * @addr: user address
1131 *
1132 * Returns struct page pointer of user page pinned for dump,
Kirill A. Shutemovea1754a2016-04-01 15:29:48 +03001133 * to be freed afterwards by put_page().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001134 *
1135 * Returns NULL on any kind of failure - a hole must then be inserted into
1136 * the corefile, to preserve alignment with its headers; and also returns
1137 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1138 * allowing a hole to be left in the corefile to save diskspace.
1139 *
1140 * Called without mmap_sem, but after all other threads have been killed.
1141 */
1142#ifdef CONFIG_ELF_CORE
1143struct page *get_dump_page(unsigned long addr)
1144{
1145 struct vm_area_struct *vma;
1146 struct page *page;
1147
1148 if (__get_user_pages(current, current->mm, addr, 1,
1149 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1150 NULL) < 1)
1151 return NULL;
1152 flush_cache_page(vma, addr, page_to_pfn(page));
1153 return page;
1154}
1155#endif /* CONFIG_ELF_CORE */
Steve Capper2667f502014-10-09 15:29:14 -07001156
1157/*
1158 * Generic RCU Fast GUP
1159 *
1160 * get_user_pages_fast attempts to pin user pages by walking the page
1161 * tables directly and avoids taking locks. Thus the walker needs to be
1162 * protected from page table pages being freed from under it, and should
1163 * block any THP splits.
1164 *
1165 * One way to achieve this is to have the walker disable interrupts, and
1166 * rely on IPIs from the TLB flushing code blocking before the page table
1167 * pages are freed. This is unsuitable for architectures that do not need
1168 * to broadcast an IPI when invalidating TLBs.
1169 *
1170 * Another way to achieve this is to batch up page table containing pages
1171 * belonging to more than one mm_user, then rcu_sched a callback to free those
1172 * pages. Disabling interrupts will allow the fast_gup walker to both block
1173 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1174 * (which is a relatively rare event). The code below adopts this strategy.
1175 *
1176 * Before activating this code, please be aware that the following assumptions
1177 * are currently made:
1178 *
1179 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1180 * pages containing page tables.
1181 *
Steve Capper2667f502014-10-09 15:29:14 -07001182 * *) ptes can be read atomically by the architecture.
1183 *
1184 * *) access_ok is sufficient to validate userspace address ranges.
1185 *
1186 * The last two assumptions can be relaxed by the addition of helper functions.
1187 *
1188 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1189 */
1190#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1191
1192#ifdef __HAVE_ARCH_PTE_SPECIAL
1193static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1194 int write, struct page **pages, int *nr)
1195{
1196 pte_t *ptep, *ptem;
1197 int ret = 0;
1198
1199 ptem = ptep = pte_offset_map(&pmd, addr);
1200 do {
1201 /*
1202 * In the line below we are assuming that the pte can be read
1203 * atomically. If this is not the case for your architecture,
1204 * please wrap this in a helper function!
1205 *
1206 * for an example see gup_get_pte in arch/x86/mm/gup.c
1207 */
Jason Low9d8c47e2015-04-15 16:14:05 -07001208 pte_t pte = READ_ONCE(*ptep);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001209 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001210
1211 /*
1212 * Similar to the PMD case below, NUMA hinting must take slow
Mel Gorman8a0516e2015-02-12 14:58:22 -08001213 * path using the pte_protnone check.
Steve Capper2667f502014-10-09 15:29:14 -07001214 */
1215 if (!pte_present(pte) || pte_special(pte) ||
Mel Gorman8a0516e2015-02-12 14:58:22 -08001216 pte_protnone(pte) || (write && !pte_write(pte)))
Steve Capper2667f502014-10-09 15:29:14 -07001217 goto pte_unmap;
1218
Dave Hansen33a709b2016-02-12 13:02:19 -08001219 if (!arch_pte_access_permitted(pte, write))
1220 goto pte_unmap;
1221
Steve Capper2667f502014-10-09 15:29:14 -07001222 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1223 page = pte_page(pte);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001224 head = compound_head(page);
Steve Capper2667f502014-10-09 15:29:14 -07001225
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001226 if (!page_cache_get_speculative(head))
Steve Capper2667f502014-10-09 15:29:14 -07001227 goto pte_unmap;
1228
1229 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001230 put_page(head);
Steve Capper2667f502014-10-09 15:29:14 -07001231 goto pte_unmap;
1232 }
1233
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001234 VM_BUG_ON_PAGE(compound_head(page) != head, page);
Steve Capper2667f502014-10-09 15:29:14 -07001235 pages[*nr] = page;
1236 (*nr)++;
1237
1238 } while (ptep++, addr += PAGE_SIZE, addr != end);
1239
1240 ret = 1;
1241
1242pte_unmap:
1243 pte_unmap(ptem);
1244 return ret;
1245}
1246#else
1247
1248/*
1249 * If we can't determine whether or not a pte is special, then fail immediately
1250 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1251 * to be special.
1252 *
1253 * For a futex to be placed on a THP tail page, get_futex_key requires a
1254 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1255 * useful to have gup_huge_pmd even if we can't operate on ptes.
1256 */
1257static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1258 int write, struct page **pages, int *nr)
1259{
1260 return 0;
1261}
1262#endif /* __HAVE_ARCH_PTE_SPECIAL */
1263
1264static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1265 unsigned long end, int write, struct page **pages, int *nr)
1266{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001267 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001268 int refs;
1269
1270 if (write && !pmd_write(orig))
1271 return 0;
1272
1273 refs = 0;
1274 head = pmd_page(orig);
1275 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001276 do {
1277 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1278 pages[*nr] = page;
1279 (*nr)++;
1280 page++;
1281 refs++;
1282 } while (addr += PAGE_SIZE, addr != end);
1283
1284 if (!page_cache_add_speculative(head, refs)) {
1285 *nr -= refs;
1286 return 0;
1287 }
1288
1289 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1290 *nr -= refs;
1291 while (refs--)
1292 put_page(head);
1293 return 0;
1294 }
1295
Steve Capper2667f502014-10-09 15:29:14 -07001296 return 1;
1297}
1298
1299static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1300 unsigned long end, int write, struct page **pages, int *nr)
1301{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001302 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001303 int refs;
1304
1305 if (write && !pud_write(orig))
1306 return 0;
1307
1308 refs = 0;
1309 head = pud_page(orig);
1310 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001311 do {
1312 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1313 pages[*nr] = page;
1314 (*nr)++;
1315 page++;
1316 refs++;
1317 } while (addr += PAGE_SIZE, addr != end);
1318
1319 if (!page_cache_add_speculative(head, refs)) {
1320 *nr -= refs;
1321 return 0;
1322 }
1323
1324 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1325 *nr -= refs;
1326 while (refs--)
1327 put_page(head);
1328 return 0;
1329 }
1330
Steve Capper2667f502014-10-09 15:29:14 -07001331 return 1;
1332}
1333
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301334static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1335 unsigned long end, int write,
1336 struct page **pages, int *nr)
1337{
1338 int refs;
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001339 struct page *head, *page;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301340
1341 if (write && !pgd_write(orig))
1342 return 0;
1343
1344 refs = 0;
1345 head = pgd_page(orig);
1346 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301347 do {
1348 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1349 pages[*nr] = page;
1350 (*nr)++;
1351 page++;
1352 refs++;
1353 } while (addr += PAGE_SIZE, addr != end);
1354
1355 if (!page_cache_add_speculative(head, refs)) {
1356 *nr -= refs;
1357 return 0;
1358 }
1359
1360 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1361 *nr -= refs;
1362 while (refs--)
1363 put_page(head);
1364 return 0;
1365 }
1366
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301367 return 1;
1368}
1369
Steve Capper2667f502014-10-09 15:29:14 -07001370static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1371 int write, struct page **pages, int *nr)
1372{
1373 unsigned long next;
1374 pmd_t *pmdp;
1375
1376 pmdp = pmd_offset(&pud, addr);
1377 do {
Christian Borntraeger38c5ce92015-01-06 22:54:46 +01001378 pmd_t pmd = READ_ONCE(*pmdp);
Steve Capper2667f502014-10-09 15:29:14 -07001379
1380 next = pmd_addr_end(addr, end);
Kirill A. Shutemov4b471e82016-01-15 16:53:39 -08001381 if (pmd_none(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001382 return 0;
1383
1384 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1385 /*
1386 * NUMA hinting faults need to be handled in the GUP
1387 * slowpath for accounting purposes and so that they
1388 * can be serialised against THP migration.
1389 */
Mel Gorman8a0516e2015-02-12 14:58:22 -08001390 if (pmd_protnone(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001391 return 0;
1392
1393 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1394 pages, nr))
1395 return 0;
1396
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301397 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1398 /*
1399 * architecture have different format for hugetlbfs
1400 * pmd format and THP pmd format
1401 */
1402 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1403 PMD_SHIFT, next, write, pages, nr))
1404 return 0;
Steve Capper2667f502014-10-09 15:29:14 -07001405 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1406 return 0;
1407 } while (pmdp++, addr = next, addr != end);
1408
1409 return 1;
1410}
1411
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001412static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301413 int write, struct page **pages, int *nr)
Steve Capper2667f502014-10-09 15:29:14 -07001414{
1415 unsigned long next;
1416 pud_t *pudp;
1417
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001418 pudp = pud_offset(&p4d, addr);
Steve Capper2667f502014-10-09 15:29:14 -07001419 do {
Christian Borntraegere37c6982014-12-07 21:41:33 +01001420 pud_t pud = READ_ONCE(*pudp);
Steve Capper2667f502014-10-09 15:29:14 -07001421
1422 next = pud_addr_end(addr, end);
1423 if (pud_none(pud))
1424 return 0;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301425 if (unlikely(pud_huge(pud))) {
Steve Capper2667f502014-10-09 15:29:14 -07001426 if (!gup_huge_pud(pud, pudp, addr, next, write,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301427 pages, nr))
1428 return 0;
1429 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1430 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1431 PUD_SHIFT, next, write, pages, nr))
Steve Capper2667f502014-10-09 15:29:14 -07001432 return 0;
1433 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1434 return 0;
1435 } while (pudp++, addr = next, addr != end);
1436
1437 return 1;
1438}
1439
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001440static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
1441 int write, struct page **pages, int *nr)
1442{
1443 unsigned long next;
1444 p4d_t *p4dp;
1445
1446 p4dp = p4d_offset(&pgd, addr);
1447 do {
1448 p4d_t p4d = READ_ONCE(*p4dp);
1449
1450 next = p4d_addr_end(addr, end);
1451 if (p4d_none(p4d))
1452 return 0;
1453 BUILD_BUG_ON(p4d_huge(p4d));
1454 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
1455 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
1456 P4D_SHIFT, next, write, pages, nr))
1457 return 0;
1458 } else if (!gup_p4d_range(p4d, addr, next, write, pages, nr))
1459 return 0;
1460 } while (p4dp++, addr = next, addr != end);
1461
1462 return 1;
1463}
1464
Steve Capper2667f502014-10-09 15:29:14 -07001465/*
1466 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1467 * the regular GUP. It will only return non-negative values.
1468 */
1469int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1470 struct page **pages)
1471{
1472 struct mm_struct *mm = current->mm;
1473 unsigned long addr, len, end;
1474 unsigned long next, flags;
1475 pgd_t *pgdp;
1476 int nr = 0;
1477
1478 start &= PAGE_MASK;
1479 addr = start;
1480 len = (unsigned long) nr_pages << PAGE_SHIFT;
1481 end = start + len;
1482
1483 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1484 start, len)))
1485 return 0;
1486
1487 /*
1488 * Disable interrupts. We use the nested form as we can already have
1489 * interrupts disabled by get_futex_key.
1490 *
1491 * With interrupts disabled, we block page table pages from being
1492 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1493 * for more details.
1494 *
1495 * We do not adopt an rcu_read_lock(.) here as we also want to
1496 * block IPIs that come from THPs splitting.
1497 */
1498
1499 local_irq_save(flags);
1500 pgdp = pgd_offset(mm, addr);
1501 do {
Jason Low9d8c47e2015-04-15 16:14:05 -07001502 pgd_t pgd = READ_ONCE(*pgdp);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301503
Steve Capper2667f502014-10-09 15:29:14 -07001504 next = pgd_addr_end(addr, end);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301505 if (pgd_none(pgd))
Steve Capper2667f502014-10-09 15:29:14 -07001506 break;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301507 if (unlikely(pgd_huge(pgd))) {
1508 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1509 pages, &nr))
1510 break;
1511 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1512 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1513 PGDIR_SHIFT, next, write, pages, &nr))
1514 break;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +03001515 } else if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
Steve Capper2667f502014-10-09 15:29:14 -07001516 break;
1517 } while (pgdp++, addr = next, addr != end);
1518 local_irq_restore(flags);
1519
1520 return nr;
1521}
1522
1523/**
1524 * get_user_pages_fast() - pin user pages in memory
1525 * @start: starting user address
1526 * @nr_pages: number of pages from start to pin
1527 * @write: whether pages will be written to
1528 * @pages: array that receives pointers to the pages pinned.
1529 * Should be at least nr_pages long.
1530 *
1531 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1532 * If not successful, it will fall back to taking the lock and
1533 * calling get_user_pages().
1534 *
1535 * Returns number of pages pinned. This may be fewer than the number
1536 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1537 * were pinned, returns -errno.
1538 */
1539int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1540 struct page **pages)
1541{
Steve Capper2667f502014-10-09 15:29:14 -07001542 int nr, ret;
1543
1544 start &= PAGE_MASK;
1545 nr = __get_user_pages_fast(start, nr_pages, write, pages);
1546 ret = nr;
1547
1548 if (nr < nr_pages) {
1549 /* Try to get the remaining pages with get_user_pages */
1550 start += nr << PAGE_SHIFT;
1551 pages += nr;
1552
Lorenzo Stoakesc1641542016-10-13 01:20:13 +01001553 ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
1554 write ? FOLL_WRITE : 0);
Steve Capper2667f502014-10-09 15:29:14 -07001555
1556 /* Have to be a bit careful with return values */
1557 if (nr > 0) {
1558 if (ret < 0)
1559 ret = nr;
1560 else
1561 ret += nr;
1562 }
1563 }
1564
1565 return ret;
1566}
1567
1568#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */