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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
Steve Capper2667f502014-10-09 15:29:14 -070013#include <linux/sched.h>
14#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
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070063static struct page *follow_page_pte(struct vm_area_struct *vma,
64 unsigned long address, pmd_t *pmd, unsigned int flags)
65{
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070066 struct mm_struct *mm = vma->vm_mm;
Dan Williams3565fce2016-01-15 16:56:55 -080067 struct dev_pagemap *pgmap = NULL;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070068 struct page *page;
69 spinlock_t *ptl;
70 pte_t *ptep, pte;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070071
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070072retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070073 if (unlikely(pmd_bad(*pmd)))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070074 return no_page_table(vma, flags);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070075
76 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070077 pte = *ptep;
78 if (!pte_present(pte)) {
79 swp_entry_t entry;
80 /*
81 * KSM's break_ksm() relies upon recognizing a ksm page
82 * even while it is being migrated, so for that case we
83 * need migration_entry_wait().
84 */
85 if (likely(!(flags & FOLL_MIGRATION)))
86 goto no_page;
Kirill A. Shutemov0661a332015-02-10 14:10:04 -080087 if (pte_none(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070088 goto no_page;
89 entry = pte_to_swp_entry(pte);
90 if (!is_migration_entry(entry))
91 goto no_page;
92 pte_unmap_unlock(ptep, ptl);
93 migration_entry_wait(mm, pmd, address);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070094 goto retry;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070095 }
Mel Gorman8a0516e2015-02-12 14:58:22 -080096 if ((flags & FOLL_NUMA) && pte_protnone(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070097 goto no_page;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070098 if ((flags & FOLL_WRITE) && !pte_write(pte)) {
99 pte_unmap_unlock(ptep, ptl);
100 return NULL;
101 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700102
103 page = vm_normal_page(vma, address, pte);
Dan Williams3565fce2016-01-15 16:56:55 -0800104 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
105 /*
106 * Only return device mapping pages in the FOLL_GET case since
107 * they are only valid while holding the pgmap reference.
108 */
109 pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
110 if (pgmap)
111 page = pte_page(pte);
112 else
113 goto no_page;
114 } else if (unlikely(!page)) {
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700115 if (flags & FOLL_DUMP) {
116 /* Avoid special (like zero) pages in core dumps */
117 page = ERR_PTR(-EFAULT);
118 goto out;
119 }
120
121 if (is_zero_pfn(pte_pfn(pte))) {
122 page = pte_page(pte);
123 } else {
124 int ret;
125
126 ret = follow_pfn_pte(vma, address, ptep, flags);
127 page = ERR_PTR(ret);
128 goto out;
129 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700130 }
131
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800132 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
133 int ret;
134 get_page(page);
135 pte_unmap_unlock(ptep, ptl);
136 lock_page(page);
137 ret = split_huge_page(page);
138 unlock_page(page);
139 put_page(page);
140 if (ret)
141 return ERR_PTR(ret);
142 goto retry;
143 }
144
Dan Williams3565fce2016-01-15 16:56:55 -0800145 if (flags & FOLL_GET) {
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -0800146 get_page(page);
Dan Williams3565fce2016-01-15 16:56:55 -0800147
148 /* drop the pgmap reference now that we hold the page */
149 if (pgmap) {
150 put_dev_pagemap(pgmap);
151 pgmap = NULL;
152 }
153 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700154 if (flags & FOLL_TOUCH) {
155 if ((flags & FOLL_WRITE) &&
156 !pte_dirty(pte) && !PageDirty(page))
157 set_page_dirty(page);
158 /*
159 * pte_mkyoung() would be more correct here, but atomic care
160 * is needed to avoid losing the dirty bit: it is easier to use
161 * mark_page_accessed().
162 */
163 mark_page_accessed(page);
164 }
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800165 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
Kirill A. Shutemove90309c2016-01-15 16:54:33 -0800166 /* Do not mlock pte-mapped THP */
167 if (PageTransCompound(page))
168 goto out;
169
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700170 /*
171 * The preliminary mapping check is mainly to avoid the
172 * pointless overhead of lock_page on the ZERO_PAGE
173 * which might bounce very badly if there is contention.
174 *
175 * If the page is already locked, we don't need to
176 * handle it now - vmscan will handle it later if and
177 * when it attempts to reclaim the page.
178 */
179 if (page->mapping && trylock_page(page)) {
180 lru_add_drain(); /* push cached pages to LRU */
181 /*
182 * Because we lock page here, and migration is
183 * blocked by the pte's page reference, and we
184 * know the page is still mapped, we don't even
185 * need to check for file-cache page truncation.
186 */
187 mlock_vma_page(page);
188 unlock_page(page);
189 }
190 }
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700191out:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700192 pte_unmap_unlock(ptep, ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700193 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700194no_page:
195 pte_unmap_unlock(ptep, ptl);
196 if (!pte_none(pte))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700197 return NULL;
198 return no_page_table(vma, flags);
199}
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700200
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700201/**
202 * follow_page_mask - look up a page descriptor from a user-virtual address
203 * @vma: vm_area_struct mapping @address
204 * @address: virtual address to look up
205 * @flags: flags modifying lookup behaviour
206 * @page_mask: on output, *page_mask is set according to the size of the page
207 *
208 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
209 *
210 * Returns the mapped (struct page *), %NULL if no mapping exists, or
211 * an error pointer if there is a mapping to something not represented
212 * by a page descriptor (see also vm_normal_page()).
213 */
214struct page *follow_page_mask(struct vm_area_struct *vma,
215 unsigned long address, unsigned int flags,
216 unsigned int *page_mask)
217{
218 pgd_t *pgd;
219 pud_t *pud;
220 pmd_t *pmd;
221 spinlock_t *ptl;
222 struct page *page;
223 struct mm_struct *mm = vma->vm_mm;
224
225 *page_mask = 0;
226
227 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
228 if (!IS_ERR(page)) {
229 BUG_ON(flags & FOLL_GET);
230 return page;
231 }
232
233 pgd = pgd_offset(mm, address);
234 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
235 return no_page_table(vma, flags);
236
237 pud = pud_offset(pgd, address);
238 if (pud_none(*pud))
239 return no_page_table(vma, flags);
240 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800241 page = follow_huge_pud(mm, address, pud, flags);
242 if (page)
243 return page;
244 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700245 }
246 if (unlikely(pud_bad(*pud)))
247 return no_page_table(vma, flags);
248
249 pmd = pmd_offset(pud, address);
250 if (pmd_none(*pmd))
251 return no_page_table(vma, flags);
252 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800253 page = follow_huge_pmd(mm, address, pmd, flags);
254 if (page)
255 return page;
256 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700257 }
Mel Gorman8a0516e2015-02-12 14:58:22 -0800258 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700259 return no_page_table(vma, flags);
Dan Williams3565fce2016-01-15 16:56:55 -0800260 if (pmd_devmap(*pmd)) {
261 ptl = pmd_lock(mm, pmd);
262 page = follow_devmap_pmd(vma, address, pmd, flags);
263 spin_unlock(ptl);
264 if (page)
265 return page;
266 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800267 if (likely(!pmd_trans_huge(*pmd)))
268 return follow_page_pte(vma, address, pmd, flags);
269
270 ptl = pmd_lock(mm, pmd);
271 if (unlikely(!pmd_trans_huge(*pmd))) {
272 spin_unlock(ptl);
273 return follow_page_pte(vma, address, pmd, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700274 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800275 if (flags & FOLL_SPLIT) {
276 int ret;
277 page = pmd_page(*pmd);
278 if (is_huge_zero_page(page)) {
279 spin_unlock(ptl);
280 ret = 0;
Kirill A. Shutemov78ddc532016-01-15 16:52:42 -0800281 split_huge_pmd(vma, pmd, address);
Naoya Horiguchi337d9ab2016-07-26 15:24:03 -0700282 if (pmd_trans_unstable(pmd))
283 ret = -EBUSY;
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800284 } else {
285 get_page(page);
286 spin_unlock(ptl);
287 lock_page(page);
288 ret = split_huge_page(page);
289 unlock_page(page);
290 put_page(page);
Kirill A. Shutemovbaa355f2016-07-26 15:25:51 -0700291 if (pmd_none(*pmd))
292 return no_page_table(vma, flags);
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800293 }
294
295 return ret ? ERR_PTR(ret) :
296 follow_page_pte(vma, address, pmd, flags);
297 }
298
299 page = follow_trans_huge_pmd(vma, address, pmd, flags);
300 spin_unlock(ptl);
301 *page_mask = HPAGE_PMD_NR - 1;
302 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700303}
304
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700305static int get_gate_page(struct mm_struct *mm, unsigned long address,
306 unsigned int gup_flags, struct vm_area_struct **vma,
307 struct page **page)
308{
309 pgd_t *pgd;
310 pud_t *pud;
311 pmd_t *pmd;
312 pte_t *pte;
313 int ret = -EFAULT;
314
315 /* user gate pages are read-only */
316 if (gup_flags & FOLL_WRITE)
317 return -EFAULT;
318 if (address > TASK_SIZE)
319 pgd = pgd_offset_k(address);
320 else
321 pgd = pgd_offset_gate(mm, address);
322 BUG_ON(pgd_none(*pgd));
323 pud = pud_offset(pgd, address);
324 BUG_ON(pud_none(*pud));
325 pmd = pmd_offset(pud, address);
326 if (pmd_none(*pmd))
327 return -EFAULT;
328 VM_BUG_ON(pmd_trans_huge(*pmd));
329 pte = pte_offset_map(pmd, address);
330 if (pte_none(*pte))
331 goto unmap;
332 *vma = get_gate_vma(mm);
333 if (!page)
334 goto out;
335 *page = vm_normal_page(*vma, address, *pte);
336 if (!*page) {
337 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
338 goto unmap;
339 *page = pte_page(*pte);
340 }
341 get_page(*page);
342out:
343 ret = 0;
344unmap:
345 pte_unmap(pte);
346 return ret;
347}
348
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700349/*
350 * mmap_sem must be held on entry. If @nonblocking != NULL and
351 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
352 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
353 */
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700354static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
355 unsigned long address, unsigned int *flags, int *nonblocking)
356{
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700357 unsigned int fault_flags = 0;
358 int ret;
359
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800360 /* mlock all present pages, but do not fault in new pages */
361 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
362 return -ENOENT;
Kirill A. Shutemov84d33df2015-04-14 15:44:37 -0700363 /* For mm_populate(), just skip the stack guard page. */
364 if ((*flags & FOLL_POPULATE) &&
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700365 (stack_guard_page_start(vma, address) ||
366 stack_guard_page_end(vma, address + PAGE_SIZE)))
367 return -ENOENT;
368 if (*flags & FOLL_WRITE)
369 fault_flags |= FAULT_FLAG_WRITE;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800370 if (*flags & FOLL_REMOTE)
371 fault_flags |= FAULT_FLAG_REMOTE;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700372 if (nonblocking)
373 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
374 if (*flags & FOLL_NOWAIT)
375 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
Andres Lagar-Cavilla234b2392014-09-17 10:51:48 -0700376 if (*flags & FOLL_TRIED) {
377 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
378 fault_flags |= FAULT_FLAG_TRIED;
379 }
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700380
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700381 ret = handle_mm_fault(vma, address, fault_flags);
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700382 if (ret & VM_FAULT_ERROR) {
383 if (ret & VM_FAULT_OOM)
384 return -ENOMEM;
385 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
386 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
Linus Torvalds33692f22015-01-29 10:51:32 -0800387 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700388 return -EFAULT;
389 BUG();
390 }
391
392 if (tsk) {
393 if (ret & VM_FAULT_MAJOR)
394 tsk->maj_flt++;
395 else
396 tsk->min_flt++;
397 }
398
399 if (ret & VM_FAULT_RETRY) {
400 if (nonblocking)
401 *nonblocking = 0;
402 return -EBUSY;
403 }
404
405 /*
406 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
407 * necessary, even if maybe_mkwrite decided not to set pte_write. We
408 * can thus safely do subsequent page lookups as if they were reads.
409 * But only do so when looping for pte_write is futile: in some cases
410 * userspace may also be wanting to write to the gotten user page,
411 * which a read fault here might prevent (a readonly page might get
412 * reCOWed by userspace write).
413 */
414 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
415 *flags &= ~FOLL_WRITE;
416 return 0;
417}
418
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700419static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
420{
421 vm_flags_t vm_flags = vma->vm_flags;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800422 int write = (gup_flags & FOLL_WRITE);
423 int foreign = (gup_flags & FOLL_REMOTE);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700424
425 if (vm_flags & (VM_IO | VM_PFNMAP))
426 return -EFAULT;
427
Dave Hansen1b2ee122016-02-12 13:02:21 -0800428 if (write) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700429 if (!(vm_flags & VM_WRITE)) {
430 if (!(gup_flags & FOLL_FORCE))
431 return -EFAULT;
432 /*
433 * We used to let the write,force case do COW in a
434 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
435 * set a breakpoint in a read-only mapping of an
436 * executable, without corrupting the file (yet only
437 * when that file had been opened for writing!).
438 * Anon pages in shared mappings are surprising: now
439 * just reject it.
440 */
Hugh Dickins46435362016-01-30 18:03:16 -0800441 if (!is_cow_mapping(vm_flags))
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700442 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700443 }
444 } else if (!(vm_flags & VM_READ)) {
445 if (!(gup_flags & FOLL_FORCE))
446 return -EFAULT;
447 /*
448 * Is there actually any vma we can reach here which does not
449 * have VM_MAYREAD set?
450 */
451 if (!(vm_flags & VM_MAYREAD))
452 return -EFAULT;
453 }
Dave Hansend61172b2016-02-12 13:02:24 -0800454 /*
455 * gups are always data accesses, not instruction
456 * fetches, so execute=false here
457 */
458 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800459 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700460 return 0;
461}
462
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700463/**
464 * __get_user_pages() - pin user pages in memory
465 * @tsk: task_struct of target task
466 * @mm: mm_struct of target mm
467 * @start: starting user address
468 * @nr_pages: number of pages from start to pin
469 * @gup_flags: flags modifying pin behaviour
470 * @pages: array that receives pointers to the pages pinned.
471 * Should be at least nr_pages long. Or NULL, if caller
472 * only intends to ensure the pages are faulted in.
473 * @vmas: array of pointers to vmas corresponding to each page.
474 * Or NULL if the caller does not require them.
475 * @nonblocking: whether waiting for disk IO or mmap_sem contention
476 *
477 * Returns number of pages pinned. This may be fewer than the number
478 * requested. If nr_pages is 0 or negative, returns 0. If no pages
479 * were pinned, returns -errno. Each page returned must be released
480 * with a put_page() call when it is finished with. vmas will only
481 * remain valid while mmap_sem is held.
482 *
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700483 * Must be called with mmap_sem held. It may be released. See below.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700484 *
485 * __get_user_pages walks a process's page tables and takes a reference to
486 * each struct page that each user address corresponds to at a given
487 * instant. That is, it takes the page that would be accessed if a user
488 * thread accesses the given user virtual address at that instant.
489 *
490 * This does not guarantee that the page exists in the user mappings when
491 * __get_user_pages returns, and there may even be a completely different
492 * page there in some cases (eg. if mmapped pagecache has been invalidated
493 * and subsequently re faulted). However it does guarantee that the page
494 * won't be freed completely. And mostly callers simply care that the page
495 * contains data that was valid *at some point in time*. Typically, an IO
496 * or similar operation cannot guarantee anything stronger anyway because
497 * locks can't be held over the syscall boundary.
498 *
499 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
500 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
501 * appropriate) must be called after the page is finished with, and
502 * before put_page is called.
503 *
504 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
505 * or mmap_sem contention, and if waiting is needed to pin all pages,
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700506 * *@nonblocking will be set to 0. Further, if @gup_flags does not
507 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
508 * this case.
509 *
510 * A caller using such a combination of @nonblocking and @gup_flags
511 * must therefore hold the mmap_sem for reading only, and recognize
512 * when it's been released. Otherwise, it must be held for either
513 * reading or writing and will not be released.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700514 *
515 * In most cases, get_user_pages or get_user_pages_fast should be used
516 * instead of __get_user_pages. __get_user_pages should be used only if
517 * you need some special @gup_flags.
518 */
519long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
520 unsigned long start, unsigned long nr_pages,
521 unsigned int gup_flags, struct page **pages,
522 struct vm_area_struct **vmas, int *nonblocking)
523{
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700524 long i = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700525 unsigned int page_mask;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700526 struct vm_area_struct *vma = NULL;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700527
528 if (!nr_pages)
529 return 0;
530
531 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
532
533 /*
534 * If FOLL_FORCE is set then do not force a full fault as the hinting
535 * fault information is unrelated to the reference behaviour of a task
536 * using the address space
537 */
538 if (!(gup_flags & FOLL_FORCE))
539 gup_flags |= FOLL_NUMA;
540
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700541 do {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700542 struct page *page;
543 unsigned int foll_flags = gup_flags;
544 unsigned int page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700545
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700546 /* first iteration or cross vma bound */
547 if (!vma || start >= vma->vm_end) {
548 vma = find_extend_vma(mm, start);
549 if (!vma && in_gate_area(mm, start)) {
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700550 int ret;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700551 ret = get_gate_page(mm, start & PAGE_MASK,
552 gup_flags, &vma,
553 pages ? &pages[i] : NULL);
554 if (ret)
555 return i ? : ret;
556 page_mask = 0;
557 goto next_page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700558 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700559
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700560 if (!vma || check_vma_flags(vma, gup_flags))
561 return i ? : -EFAULT;
562 if (is_vm_hugetlb_page(vma)) {
563 i = follow_hugetlb_page(mm, vma, pages, vmas,
564 &start, &nr_pages, i,
565 gup_flags);
566 continue;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700567 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700568 }
569retry:
570 /*
571 * If we have a pending SIGKILL, don't keep faulting pages and
572 * potentially allocating memory.
573 */
574 if (unlikely(fatal_signal_pending(current)))
575 return i ? i : -ERESTARTSYS;
576 cond_resched();
577 page = follow_page_mask(vma, start, foll_flags, &page_mask);
578 if (!page) {
579 int ret;
580 ret = faultin_page(tsk, vma, start, &foll_flags,
581 nonblocking);
582 switch (ret) {
583 case 0:
584 goto retry;
585 case -EFAULT:
586 case -ENOMEM:
587 case -EHWPOISON:
588 return i ? i : ret;
589 case -EBUSY:
590 return i;
591 case -ENOENT:
592 goto next_page;
593 }
594 BUG();
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700595 } else if (PTR_ERR(page) == -EEXIST) {
596 /*
597 * Proper page table entry exists, but no corresponding
598 * struct page.
599 */
600 goto next_page;
601 } else if (IS_ERR(page)) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700602 return i ? i : PTR_ERR(page);
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700603 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700604 if (pages) {
605 pages[i] = page;
606 flush_anon_page(vma, page, start);
607 flush_dcache_page(page);
608 page_mask = 0;
609 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700610next_page:
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700611 if (vmas) {
612 vmas[i] = vma;
613 page_mask = 0;
614 }
615 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
616 if (page_increm > nr_pages)
617 page_increm = nr_pages;
618 i += page_increm;
619 start += page_increm * PAGE_SIZE;
620 nr_pages -= page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700621 } while (nr_pages);
622 return i;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700623}
624EXPORT_SYMBOL(__get_user_pages);
625
Dave Hansend4925e02016-02-12 13:02:16 -0800626bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
627{
Dave Hansen1b2ee122016-02-12 13:02:21 -0800628 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
629 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
Dave Hansen33a709b2016-02-12 13:02:19 -0800630 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
Dave Hansend4925e02016-02-12 13:02:16 -0800631
632 if (!(vm_flags & vma->vm_flags))
633 return false;
634
Dave Hansen33a709b2016-02-12 13:02:19 -0800635 /*
636 * The architecture might have a hardware protection
Dave Hansen1b2ee122016-02-12 13:02:21 -0800637 * mechanism other than read/write that can deny access.
Dave Hansend61172b2016-02-12 13:02:24 -0800638 *
639 * gup always represents data access, not instruction
640 * fetches, so execute=false here:
Dave Hansen33a709b2016-02-12 13:02:19 -0800641 */
Dave Hansend61172b2016-02-12 13:02:24 -0800642 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800643 return false;
644
Dave Hansend4925e02016-02-12 13:02:16 -0800645 return true;
646}
647
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700648/*
649 * fixup_user_fault() - manually resolve a user page fault
650 * @tsk: the task_struct to use for page fault accounting, or
651 * NULL if faults are not to be recorded.
652 * @mm: mm_struct of target mm
653 * @address: user address
654 * @fault_flags:flags to pass down to handle_mm_fault()
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800655 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
656 * does not allow retry
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700657 *
658 * This is meant to be called in the specific scenario where for locking reasons
659 * we try to access user memory in atomic context (within a pagefault_disable()
660 * section), this returns -EFAULT, and we want to resolve the user fault before
661 * trying again.
662 *
663 * Typically this is meant to be used by the futex code.
664 *
665 * The main difference with get_user_pages() is that this function will
666 * unconditionally call handle_mm_fault() which will in turn perform all the
667 * necessary SW fixup of the dirty and young bits in the PTE, while
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800668 * get_user_pages() only guarantees to update these in the struct page.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700669 *
670 * This is important for some architectures where those bits also gate the
671 * access permission to the page because they are maintained in software. On
672 * such architectures, gup() will not be enough to make a subsequent access
673 * succeed.
674 *
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800675 * This function will not return with an unlocked mmap_sem. So it has not the
676 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700677 */
678int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800679 unsigned long address, unsigned int fault_flags,
680 bool *unlocked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700681{
682 struct vm_area_struct *vma;
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800683 int ret, major = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700684
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800685 if (unlocked)
686 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
687
688retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700689 vma = find_extend_vma(mm, address);
690 if (!vma || address < vma->vm_start)
691 return -EFAULT;
692
Dave Hansend4925e02016-02-12 13:02:16 -0800693 if (!vma_permits_fault(vma, fault_flags))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700694 return -EFAULT;
695
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700696 ret = handle_mm_fault(vma, address, fault_flags);
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800697 major |= ret & VM_FAULT_MAJOR;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700698 if (ret & VM_FAULT_ERROR) {
699 if (ret & VM_FAULT_OOM)
700 return -ENOMEM;
701 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
702 return -EHWPOISON;
Linus Torvalds33692f22015-01-29 10:51:32 -0800703 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700704 return -EFAULT;
705 BUG();
706 }
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800707
708 if (ret & VM_FAULT_RETRY) {
709 down_read(&mm->mmap_sem);
710 if (!(fault_flags & FAULT_FLAG_TRIED)) {
711 *unlocked = true;
712 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
713 fault_flags |= FAULT_FLAG_TRIED;
714 goto retry;
715 }
716 }
717
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700718 if (tsk) {
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800719 if (major)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700720 tsk->maj_flt++;
721 else
722 tsk->min_flt++;
723 }
724 return 0;
725}
726
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800727static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
728 struct mm_struct *mm,
729 unsigned long start,
730 unsigned long nr_pages,
731 int write, int force,
732 struct page **pages,
733 struct vm_area_struct **vmas,
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800734 int *locked, bool notify_drop,
735 unsigned int flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800736{
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800737 long ret, pages_done;
738 bool lock_dropped;
739
740 if (locked) {
741 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
742 BUG_ON(vmas);
743 /* check caller initialized locked */
744 BUG_ON(*locked != 1);
745 }
746
747 if (pages)
748 flags |= FOLL_GET;
749 if (write)
750 flags |= FOLL_WRITE;
751 if (force)
752 flags |= FOLL_FORCE;
753
754 pages_done = 0;
755 lock_dropped = false;
756 for (;;) {
757 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
758 vmas, locked);
759 if (!locked)
760 /* VM_FAULT_RETRY couldn't trigger, bypass */
761 return ret;
762
763 /* VM_FAULT_RETRY cannot return errors */
764 if (!*locked) {
765 BUG_ON(ret < 0);
766 BUG_ON(ret >= nr_pages);
767 }
768
769 if (!pages)
770 /* If it's a prefault don't insist harder */
771 return ret;
772
773 if (ret > 0) {
774 nr_pages -= ret;
775 pages_done += ret;
776 if (!nr_pages)
777 break;
778 }
779 if (*locked) {
780 /* VM_FAULT_RETRY didn't trigger */
781 if (!pages_done)
782 pages_done = ret;
783 break;
784 }
785 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
786 pages += ret;
787 start += ret << PAGE_SHIFT;
788
789 /*
790 * Repeat on the address that fired VM_FAULT_RETRY
791 * without FAULT_FLAG_ALLOW_RETRY but with
792 * FAULT_FLAG_TRIED.
793 */
794 *locked = 1;
795 lock_dropped = true;
796 down_read(&mm->mmap_sem);
797 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
798 pages, NULL, NULL);
799 if (ret != 1) {
800 BUG_ON(ret > 1);
801 if (!pages_done)
802 pages_done = ret;
803 break;
804 }
805 nr_pages--;
806 pages_done++;
807 if (!nr_pages)
808 break;
809 pages++;
810 start += PAGE_SIZE;
811 }
812 if (notify_drop && lock_dropped && *locked) {
813 /*
814 * We must let the caller know we temporarily dropped the lock
815 * and so the critical section protected by it was lost.
816 */
817 up_read(&mm->mmap_sem);
818 *locked = 0;
819 }
820 return pages_done;
821}
822
823/*
824 * We can leverage the VM_FAULT_RETRY functionality in the page fault
825 * paths better by using either get_user_pages_locked() or
826 * get_user_pages_unlocked().
827 *
828 * get_user_pages_locked() is suitable to replace the form:
829 *
830 * down_read(&mm->mmap_sem);
831 * do_something()
832 * get_user_pages(tsk, mm, ..., pages, NULL);
833 * up_read(&mm->mmap_sem);
834 *
835 * to:
836 *
837 * int locked = 1;
838 * down_read(&mm->mmap_sem);
839 * do_something()
840 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
841 * if (locked)
842 * up_read(&mm->mmap_sem);
843 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200844long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800845 int write, int force, struct page **pages,
846 int *locked)
847{
Dave Hansencde70142016-02-12 13:01:55 -0800848 return __get_user_pages_locked(current, current->mm, start, nr_pages,
849 write, force, pages, NULL, locked, true,
850 FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800851}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200852EXPORT_SYMBOL(get_user_pages_locked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800853
854/*
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800855 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
856 * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
857 *
858 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
859 * caller if required (just like with __get_user_pages). "FOLL_GET",
860 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
861 * according to the parameters "pages", "write", "force"
862 * respectively.
863 */
864__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
865 unsigned long start, unsigned long nr_pages,
866 int write, int force, struct page **pages,
867 unsigned int gup_flags)
868{
869 long ret;
870 int locked = 1;
871 down_read(&mm->mmap_sem);
872 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
873 pages, NULL, &locked, false, gup_flags);
874 if (locked)
875 up_read(&mm->mmap_sem);
876 return ret;
877}
878EXPORT_SYMBOL(__get_user_pages_unlocked);
879
880/*
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800881 * get_user_pages_unlocked() is suitable to replace the form:
882 *
883 * down_read(&mm->mmap_sem);
884 * get_user_pages(tsk, mm, ..., pages, NULL);
885 * up_read(&mm->mmap_sem);
886 *
887 * with:
888 *
889 * get_user_pages_unlocked(tsk, mm, ..., pages);
890 *
891 * It is functionally equivalent to get_user_pages_fast so
892 * get_user_pages_fast should be used instead, if the two parameters
893 * "tsk" and "mm" are respectively equal to current and current->mm,
894 * or if "force" shall be set to 1 (get_user_pages_fast misses the
895 * "force" parameter).
896 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200897long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800898 int write, int force, struct page **pages)
899{
Dave Hansencde70142016-02-12 13:01:55 -0800900 return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
901 write, force, pages, FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800902}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200903EXPORT_SYMBOL(get_user_pages_unlocked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800904
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700905/*
Dave Hansen1e987792016-02-12 13:01:54 -0800906 * get_user_pages_remote() - pin user pages in memory
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700907 * @tsk: the task_struct to use for page fault accounting, or
908 * NULL if faults are not to be recorded.
909 * @mm: mm_struct of target mm
910 * @start: starting user address
911 * @nr_pages: number of pages from start to pin
912 * @write: whether pages will be written to by the caller
913 * @force: whether to force access even when user mapping is currently
914 * protected (but never forces write access to shared mapping).
915 * @pages: array that receives pointers to the pages pinned.
916 * Should be at least nr_pages long. Or NULL, if caller
917 * only intends to ensure the pages are faulted in.
918 * @vmas: array of pointers to vmas corresponding to each page.
919 * Or NULL if the caller does not require them.
920 *
921 * Returns number of pages pinned. This may be fewer than the number
922 * requested. If nr_pages is 0 or negative, returns 0. If no pages
923 * were pinned, returns -errno. Each page returned must be released
924 * with a put_page() call when it is finished with. vmas will only
925 * remain valid while mmap_sem is held.
926 *
927 * Must be called with mmap_sem held for read or write.
928 *
929 * get_user_pages walks a process's page tables and takes a reference to
930 * each struct page that each user address corresponds to at a given
931 * instant. That is, it takes the page that would be accessed if a user
932 * thread accesses the given user virtual address at that instant.
933 *
934 * This does not guarantee that the page exists in the user mappings when
935 * get_user_pages returns, and there may even be a completely different
936 * page there in some cases (eg. if mmapped pagecache has been invalidated
937 * and subsequently re faulted). However it does guarantee that the page
938 * won't be freed completely. And mostly callers simply care that the page
939 * contains data that was valid *at some point in time*. Typically, an IO
940 * or similar operation cannot guarantee anything stronger anyway because
941 * locks can't be held over the syscall boundary.
942 *
943 * If write=0, the page must not be written to. If the page is written to,
944 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
945 * after the page is finished with, and before put_page is called.
946 *
947 * get_user_pages is typically used for fewer-copy IO operations, to get a
948 * handle on the memory by some means other than accesses via the user virtual
949 * addresses. The pages may be submitted for DMA to devices or accessed via
950 * their kernel linear mapping (via the kmap APIs). Care should be taken to
951 * use the correct cache flushing APIs.
952 *
953 * See also get_user_pages_fast, for performance critical applications.
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800954 *
955 * get_user_pages should be phased out in favor of
956 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
957 * should use get_user_pages because it cannot pass
958 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700959 */
Dave Hansen1e987792016-02-12 13:01:54 -0800960long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
961 unsigned long start, unsigned long nr_pages,
962 int write, int force, struct page **pages,
963 struct vm_area_struct **vmas)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700964{
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800965 return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
Dave Hansen1e987792016-02-12 13:01:54 -0800966 pages, vmas, NULL, false,
967 FOLL_TOUCH | FOLL_REMOTE);
968}
969EXPORT_SYMBOL(get_user_pages_remote);
970
971/*
Dave Hansend4edcf02016-02-12 13:01:56 -0800972 * This is the same as get_user_pages_remote(), just with a
973 * less-flexible calling convention where we assume that the task
974 * and mm being operated on are the current task's. We also
975 * obviously don't pass FOLL_REMOTE in here.
Dave Hansen1e987792016-02-12 13:01:54 -0800976 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200977long get_user_pages(unsigned long start, unsigned long nr_pages,
Dave Hansen1e987792016-02-12 13:01:54 -0800978 int write, int force, struct page **pages,
979 struct vm_area_struct **vmas)
980{
Dave Hansencde70142016-02-12 13:01:55 -0800981 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Dave Hansen1e987792016-02-12 13:01:54 -0800982 write, force, pages, vmas, NULL, false,
983 FOLL_TOUCH);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700984}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200985EXPORT_SYMBOL(get_user_pages);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700986
987/**
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -0700988 * populate_vma_page_range() - populate a range of pages in the vma.
989 * @vma: target vma
990 * @start: start address
991 * @end: end address
992 * @nonblocking:
993 *
994 * This takes care of mlocking the pages too if VM_LOCKED is set.
995 *
996 * return 0 on success, negative error code on error.
997 *
998 * vma->vm_mm->mmap_sem must be held.
999 *
1000 * If @nonblocking is NULL, it may be held for read or write and will
1001 * be unperturbed.
1002 *
1003 * If @nonblocking is non-NULL, it must held for read only and may be
1004 * released. If it's released, *@nonblocking will be set to 0.
1005 */
1006long populate_vma_page_range(struct vm_area_struct *vma,
1007 unsigned long start, unsigned long end, int *nonblocking)
1008{
1009 struct mm_struct *mm = vma->vm_mm;
1010 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1011 int gup_flags;
1012
1013 VM_BUG_ON(start & ~PAGE_MASK);
1014 VM_BUG_ON(end & ~PAGE_MASK);
1015 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1016 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1017 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1018
Eric B Munsonde60f5f2015-11-05 18:51:36 -08001019 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1020 if (vma->vm_flags & VM_LOCKONFAULT)
1021 gup_flags &= ~FOLL_POPULATE;
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001022 /*
1023 * We want to touch writable mappings with a write fault in order
1024 * to break COW, except for shared mappings because these don't COW
1025 * and we would not want to dirty them for nothing.
1026 */
1027 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1028 gup_flags |= FOLL_WRITE;
1029
1030 /*
1031 * We want mlock to succeed for regions that have any permissions
1032 * other than PROT_NONE.
1033 */
1034 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1035 gup_flags |= FOLL_FORCE;
1036
1037 /*
1038 * We made sure addr is within a VMA, so the following will
1039 * not result in a stack expansion that recurses back here.
1040 */
1041 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1042 NULL, NULL, nonblocking);
1043}
1044
1045/*
1046 * __mm_populate - populate and/or mlock pages within a range of address space.
1047 *
1048 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1049 * flags. VMAs must be already marked with the desired vm_flags, and
1050 * mmap_sem must not be held.
1051 */
1052int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1053{
1054 struct mm_struct *mm = current->mm;
1055 unsigned long end, nstart, nend;
1056 struct vm_area_struct *vma = NULL;
1057 int locked = 0;
1058 long ret = 0;
1059
1060 VM_BUG_ON(start & ~PAGE_MASK);
1061 VM_BUG_ON(len != PAGE_ALIGN(len));
1062 end = start + len;
1063
1064 for (nstart = start; nstart < end; nstart = nend) {
1065 /*
1066 * We want to fault in pages for [nstart; end) address range.
1067 * Find first corresponding VMA.
1068 */
1069 if (!locked) {
1070 locked = 1;
1071 down_read(&mm->mmap_sem);
1072 vma = find_vma(mm, nstart);
1073 } else if (nstart >= vma->vm_end)
1074 vma = vma->vm_next;
1075 if (!vma || vma->vm_start >= end)
1076 break;
1077 /*
1078 * Set [nstart; nend) to intersection of desired address
1079 * range with the first VMA. Also, skip undesirable VMA types.
1080 */
1081 nend = min(end, vma->vm_end);
1082 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1083 continue;
1084 if (nstart < vma->vm_start)
1085 nstart = vma->vm_start;
1086 /*
1087 * Now fault in a range of pages. populate_vma_page_range()
1088 * double checks the vma flags, so that it won't mlock pages
1089 * if the vma was already munlocked.
1090 */
1091 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1092 if (ret < 0) {
1093 if (ignore_errors) {
1094 ret = 0;
1095 continue; /* continue at next VMA */
1096 }
1097 break;
1098 }
1099 nend = nstart + ret * PAGE_SIZE;
1100 ret = 0;
1101 }
1102 if (locked)
1103 up_read(&mm->mmap_sem);
1104 return ret; /* 0 or negative error code */
1105}
1106
1107/**
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001108 * get_dump_page() - pin user page in memory while writing it to core dump
1109 * @addr: user address
1110 *
1111 * Returns struct page pointer of user page pinned for dump,
Kirill A. Shutemovea1754a2016-04-01 15:29:48 +03001112 * to be freed afterwards by put_page().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001113 *
1114 * Returns NULL on any kind of failure - a hole must then be inserted into
1115 * the corefile, to preserve alignment with its headers; and also returns
1116 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1117 * allowing a hole to be left in the corefile to save diskspace.
1118 *
1119 * Called without mmap_sem, but after all other threads have been killed.
1120 */
1121#ifdef CONFIG_ELF_CORE
1122struct page *get_dump_page(unsigned long addr)
1123{
1124 struct vm_area_struct *vma;
1125 struct page *page;
1126
1127 if (__get_user_pages(current, current->mm, addr, 1,
1128 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1129 NULL) < 1)
1130 return NULL;
1131 flush_cache_page(vma, addr, page_to_pfn(page));
1132 return page;
1133}
1134#endif /* CONFIG_ELF_CORE */
Steve Capper2667f502014-10-09 15:29:14 -07001135
1136/*
1137 * Generic RCU Fast GUP
1138 *
1139 * get_user_pages_fast attempts to pin user pages by walking the page
1140 * tables directly and avoids taking locks. Thus the walker needs to be
1141 * protected from page table pages being freed from under it, and should
1142 * block any THP splits.
1143 *
1144 * One way to achieve this is to have the walker disable interrupts, and
1145 * rely on IPIs from the TLB flushing code blocking before the page table
1146 * pages are freed. This is unsuitable for architectures that do not need
1147 * to broadcast an IPI when invalidating TLBs.
1148 *
1149 * Another way to achieve this is to batch up page table containing pages
1150 * belonging to more than one mm_user, then rcu_sched a callback to free those
1151 * pages. Disabling interrupts will allow the fast_gup walker to both block
1152 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1153 * (which is a relatively rare event). The code below adopts this strategy.
1154 *
1155 * Before activating this code, please be aware that the following assumptions
1156 * are currently made:
1157 *
1158 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1159 * pages containing page tables.
1160 *
Steve Capper2667f502014-10-09 15:29:14 -07001161 * *) ptes can be read atomically by the architecture.
1162 *
1163 * *) access_ok is sufficient to validate userspace address ranges.
1164 *
1165 * The last two assumptions can be relaxed by the addition of helper functions.
1166 *
1167 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1168 */
1169#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1170
1171#ifdef __HAVE_ARCH_PTE_SPECIAL
1172static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1173 int write, struct page **pages, int *nr)
1174{
1175 pte_t *ptep, *ptem;
1176 int ret = 0;
1177
1178 ptem = ptep = pte_offset_map(&pmd, addr);
1179 do {
1180 /*
1181 * In the line below we are assuming that the pte can be read
1182 * atomically. If this is not the case for your architecture,
1183 * please wrap this in a helper function!
1184 *
1185 * for an example see gup_get_pte in arch/x86/mm/gup.c
1186 */
Jason Low9d8c47e2015-04-15 16:14:05 -07001187 pte_t pte = READ_ONCE(*ptep);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001188 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001189
1190 /*
1191 * Similar to the PMD case below, NUMA hinting must take slow
Mel Gorman8a0516e2015-02-12 14:58:22 -08001192 * path using the pte_protnone check.
Steve Capper2667f502014-10-09 15:29:14 -07001193 */
1194 if (!pte_present(pte) || pte_special(pte) ||
Mel Gorman8a0516e2015-02-12 14:58:22 -08001195 pte_protnone(pte) || (write && !pte_write(pte)))
Steve Capper2667f502014-10-09 15:29:14 -07001196 goto pte_unmap;
1197
Dave Hansen33a709b2016-02-12 13:02:19 -08001198 if (!arch_pte_access_permitted(pte, write))
1199 goto pte_unmap;
1200
Steve Capper2667f502014-10-09 15:29:14 -07001201 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1202 page = pte_page(pte);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001203 head = compound_head(page);
Steve Capper2667f502014-10-09 15:29:14 -07001204
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001205 if (!page_cache_get_speculative(head))
Steve Capper2667f502014-10-09 15:29:14 -07001206 goto pte_unmap;
1207
1208 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001209 put_page(head);
Steve Capper2667f502014-10-09 15:29:14 -07001210 goto pte_unmap;
1211 }
1212
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001213 VM_BUG_ON_PAGE(compound_head(page) != head, page);
Steve Capper2667f502014-10-09 15:29:14 -07001214 pages[*nr] = page;
1215 (*nr)++;
1216
1217 } while (ptep++, addr += PAGE_SIZE, addr != end);
1218
1219 ret = 1;
1220
1221pte_unmap:
1222 pte_unmap(ptem);
1223 return ret;
1224}
1225#else
1226
1227/*
1228 * If we can't determine whether or not a pte is special, then fail immediately
1229 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1230 * to be special.
1231 *
1232 * For a futex to be placed on a THP tail page, get_futex_key requires a
1233 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1234 * useful to have gup_huge_pmd even if we can't operate on ptes.
1235 */
1236static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1237 int write, struct page **pages, int *nr)
1238{
1239 return 0;
1240}
1241#endif /* __HAVE_ARCH_PTE_SPECIAL */
1242
1243static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1244 unsigned long end, int write, struct page **pages, int *nr)
1245{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001246 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001247 int refs;
1248
1249 if (write && !pmd_write(orig))
1250 return 0;
1251
1252 refs = 0;
1253 head = pmd_page(orig);
1254 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001255 do {
1256 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1257 pages[*nr] = page;
1258 (*nr)++;
1259 page++;
1260 refs++;
1261 } while (addr += PAGE_SIZE, addr != end);
1262
1263 if (!page_cache_add_speculative(head, refs)) {
1264 *nr -= refs;
1265 return 0;
1266 }
1267
1268 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1269 *nr -= refs;
1270 while (refs--)
1271 put_page(head);
1272 return 0;
1273 }
1274
Steve Capper2667f502014-10-09 15:29:14 -07001275 return 1;
1276}
1277
1278static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1279 unsigned long end, int write, struct page **pages, int *nr)
1280{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001281 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001282 int refs;
1283
1284 if (write && !pud_write(orig))
1285 return 0;
1286
1287 refs = 0;
1288 head = pud_page(orig);
1289 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001290 do {
1291 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1292 pages[*nr] = page;
1293 (*nr)++;
1294 page++;
1295 refs++;
1296 } while (addr += PAGE_SIZE, addr != end);
1297
1298 if (!page_cache_add_speculative(head, refs)) {
1299 *nr -= refs;
1300 return 0;
1301 }
1302
1303 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1304 *nr -= refs;
1305 while (refs--)
1306 put_page(head);
1307 return 0;
1308 }
1309
Steve Capper2667f502014-10-09 15:29:14 -07001310 return 1;
1311}
1312
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301313static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1314 unsigned long end, int write,
1315 struct page **pages, int *nr)
1316{
1317 int refs;
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001318 struct page *head, *page;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301319
1320 if (write && !pgd_write(orig))
1321 return 0;
1322
1323 refs = 0;
1324 head = pgd_page(orig);
1325 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301326 do {
1327 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1328 pages[*nr] = page;
1329 (*nr)++;
1330 page++;
1331 refs++;
1332 } while (addr += PAGE_SIZE, addr != end);
1333
1334 if (!page_cache_add_speculative(head, refs)) {
1335 *nr -= refs;
1336 return 0;
1337 }
1338
1339 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1340 *nr -= refs;
1341 while (refs--)
1342 put_page(head);
1343 return 0;
1344 }
1345
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301346 return 1;
1347}
1348
Steve Capper2667f502014-10-09 15:29:14 -07001349static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1350 int write, struct page **pages, int *nr)
1351{
1352 unsigned long next;
1353 pmd_t *pmdp;
1354
1355 pmdp = pmd_offset(&pud, addr);
1356 do {
Christian Borntraeger38c5ce92015-01-06 22:54:46 +01001357 pmd_t pmd = READ_ONCE(*pmdp);
Steve Capper2667f502014-10-09 15:29:14 -07001358
1359 next = pmd_addr_end(addr, end);
Kirill A. Shutemov4b471e82016-01-15 16:53:39 -08001360 if (pmd_none(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001361 return 0;
1362
1363 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1364 /*
1365 * NUMA hinting faults need to be handled in the GUP
1366 * slowpath for accounting purposes and so that they
1367 * can be serialised against THP migration.
1368 */
Mel Gorman8a0516e2015-02-12 14:58:22 -08001369 if (pmd_protnone(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001370 return 0;
1371
1372 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1373 pages, nr))
1374 return 0;
1375
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301376 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1377 /*
1378 * architecture have different format for hugetlbfs
1379 * pmd format and THP pmd format
1380 */
1381 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1382 PMD_SHIFT, next, write, pages, nr))
1383 return 0;
Steve Capper2667f502014-10-09 15:29:14 -07001384 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1385 return 0;
1386 } while (pmdp++, addr = next, addr != end);
1387
1388 return 1;
1389}
1390
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301391static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
1392 int write, struct page **pages, int *nr)
Steve Capper2667f502014-10-09 15:29:14 -07001393{
1394 unsigned long next;
1395 pud_t *pudp;
1396
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301397 pudp = pud_offset(&pgd, addr);
Steve Capper2667f502014-10-09 15:29:14 -07001398 do {
Christian Borntraegere37c6982014-12-07 21:41:33 +01001399 pud_t pud = READ_ONCE(*pudp);
Steve Capper2667f502014-10-09 15:29:14 -07001400
1401 next = pud_addr_end(addr, end);
1402 if (pud_none(pud))
1403 return 0;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301404 if (unlikely(pud_huge(pud))) {
Steve Capper2667f502014-10-09 15:29:14 -07001405 if (!gup_huge_pud(pud, pudp, addr, next, write,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301406 pages, nr))
1407 return 0;
1408 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1409 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1410 PUD_SHIFT, next, write, pages, nr))
Steve Capper2667f502014-10-09 15:29:14 -07001411 return 0;
1412 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1413 return 0;
1414 } while (pudp++, addr = next, addr != end);
1415
1416 return 1;
1417}
1418
1419/*
1420 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1421 * the regular GUP. It will only return non-negative values.
1422 */
1423int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1424 struct page **pages)
1425{
1426 struct mm_struct *mm = current->mm;
1427 unsigned long addr, len, end;
1428 unsigned long next, flags;
1429 pgd_t *pgdp;
1430 int nr = 0;
1431
1432 start &= PAGE_MASK;
1433 addr = start;
1434 len = (unsigned long) nr_pages << PAGE_SHIFT;
1435 end = start + len;
1436
1437 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1438 start, len)))
1439 return 0;
1440
1441 /*
1442 * Disable interrupts. We use the nested form as we can already have
1443 * interrupts disabled by get_futex_key.
1444 *
1445 * With interrupts disabled, we block page table pages from being
1446 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1447 * for more details.
1448 *
1449 * We do not adopt an rcu_read_lock(.) here as we also want to
1450 * block IPIs that come from THPs splitting.
1451 */
1452
1453 local_irq_save(flags);
1454 pgdp = pgd_offset(mm, addr);
1455 do {
Jason Low9d8c47e2015-04-15 16:14:05 -07001456 pgd_t pgd = READ_ONCE(*pgdp);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301457
Steve Capper2667f502014-10-09 15:29:14 -07001458 next = pgd_addr_end(addr, end);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301459 if (pgd_none(pgd))
Steve Capper2667f502014-10-09 15:29:14 -07001460 break;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301461 if (unlikely(pgd_huge(pgd))) {
1462 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1463 pages, &nr))
1464 break;
1465 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1466 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1467 PGDIR_SHIFT, next, write, pages, &nr))
1468 break;
1469 } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
Steve Capper2667f502014-10-09 15:29:14 -07001470 break;
1471 } while (pgdp++, addr = next, addr != end);
1472 local_irq_restore(flags);
1473
1474 return nr;
1475}
1476
1477/**
1478 * get_user_pages_fast() - pin user pages in memory
1479 * @start: starting user address
1480 * @nr_pages: number of pages from start to pin
1481 * @write: whether pages will be written to
1482 * @pages: array that receives pointers to the pages pinned.
1483 * Should be at least nr_pages long.
1484 *
1485 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1486 * If not successful, it will fall back to taking the lock and
1487 * calling get_user_pages().
1488 *
1489 * Returns number of pages pinned. This may be fewer than the number
1490 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1491 * were pinned, returns -errno.
1492 */
1493int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1494 struct page **pages)
1495{
Steve Capper2667f502014-10-09 15:29:14 -07001496 int nr, ret;
1497
1498 start &= PAGE_MASK;
1499 nr = __get_user_pages_fast(start, nr_pages, write, pages);
1500 ret = nr;
1501
1502 if (nr < nr_pages) {
1503 /* Try to get the remaining pages with get_user_pages */
1504 start += nr << PAGE_SHIFT;
1505 pages += nr;
1506
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001507 ret = get_user_pages_unlocked(start, nr_pages - nr, write, 0, pages);
Steve Capper2667f502014-10-09 15:29:14 -07001508
1509 /* Have to be a bit careful with return values */
1510 if (nr > 0) {
1511 if (ret < 0)
1512 ret = nr;
1513 else
1514 ret += nr;
1515 }
1516 }
1517
1518 return ret;
1519}
1520
1521#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */