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4bbd4c77 KS |
1 | #include <linux/kernel.h> |
2 | #include <linux/errno.h> | |
3 | #include <linux/err.h> | |
4 | #include <linux/spinlock.h> | |
5 | ||
4bbd4c77 | 6 | #include <linux/mm.h> |
3565fce3 | 7 | #include <linux/memremap.h> |
4bbd4c77 KS |
8 | #include <linux/pagemap.h> |
9 | #include <linux/rmap.h> | |
10 | #include <linux/swap.h> | |
11 | #include <linux/swapops.h> | |
12 | ||
2667f50e SC |
13 | #include <linux/sched.h> |
14 | #include <linux/rwsem.h> | |
f30c59e9 | 15 | #include <linux/hugetlb.h> |
1027e443 | 16 | |
2667f50e | 17 | #include <asm/pgtable.h> |
1027e443 | 18 | #include <asm/tlbflush.h> |
2667f50e | 19 | |
4bbd4c77 KS |
20 | #include "internal.h" |
21 | ||
69e68b4f KS |
22 | static struct page *no_page_table(struct vm_area_struct *vma, |
23 | unsigned int flags) | |
4bbd4c77 | 24 | { |
69e68b4f KS |
25 | /* |
26 | * When core dumping an enormous anonymous area that nobody | |
27 | * has touched so far, we don't want to allocate unnecessary pages or | |
28 | * page tables. Return error instead of NULL to skip handle_mm_fault, | |
29 | * then get_dump_page() will return NULL to leave a hole in the dump. | |
30 | * But we can only make this optimization where a hole would surely | |
31 | * be zero-filled if handle_mm_fault() actually did handle it. | |
32 | */ | |
33 | if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault)) | |
34 | return ERR_PTR(-EFAULT); | |
35 | return NULL; | |
36 | } | |
4bbd4c77 | 37 | |
1027e443 KS |
38 | static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, |
39 | pte_t *pte, unsigned int flags) | |
40 | { | |
41 | /* No page to get reference */ | |
42 | if (flags & FOLL_GET) | |
43 | return -EFAULT; | |
44 | ||
45 | if (flags & FOLL_TOUCH) { | |
46 | pte_t entry = *pte; | |
47 | ||
48 | if (flags & FOLL_WRITE) | |
49 | entry = pte_mkdirty(entry); | |
50 | entry = pte_mkyoung(entry); | |
51 | ||
52 | if (!pte_same(*pte, entry)) { | |
53 | set_pte_at(vma->vm_mm, address, pte, entry); | |
54 | update_mmu_cache(vma, address, pte); | |
55 | } | |
56 | } | |
57 | ||
58 | /* Proper page table entry exists, but no corresponding struct page */ | |
59 | return -EEXIST; | |
60 | } | |
61 | ||
69e68b4f KS |
62 | static struct page *follow_page_pte(struct vm_area_struct *vma, |
63 | unsigned long address, pmd_t *pmd, unsigned int flags) | |
64 | { | |
65 | struct mm_struct *mm = vma->vm_mm; | |
3565fce3 | 66 | struct dev_pagemap *pgmap = NULL; |
69e68b4f KS |
67 | struct page *page; |
68 | spinlock_t *ptl; | |
69 | pte_t *ptep, pte; | |
4bbd4c77 | 70 | |
69e68b4f | 71 | retry: |
4bbd4c77 | 72 | if (unlikely(pmd_bad(*pmd))) |
69e68b4f | 73 | return no_page_table(vma, flags); |
4bbd4c77 KS |
74 | |
75 | ptep = pte_offset_map_lock(mm, pmd, address, &ptl); | |
4bbd4c77 KS |
76 | pte = *ptep; |
77 | if (!pte_present(pte)) { | |
78 | swp_entry_t entry; | |
79 | /* | |
80 | * KSM's break_ksm() relies upon recognizing a ksm page | |
81 | * even while it is being migrated, so for that case we | |
82 | * need migration_entry_wait(). | |
83 | */ | |
84 | if (likely(!(flags & FOLL_MIGRATION))) | |
85 | goto no_page; | |
0661a336 | 86 | if (pte_none(pte)) |
4bbd4c77 KS |
87 | goto no_page; |
88 | entry = pte_to_swp_entry(pte); | |
89 | if (!is_migration_entry(entry)) | |
90 | goto no_page; | |
91 | pte_unmap_unlock(ptep, ptl); | |
92 | migration_entry_wait(mm, pmd, address); | |
69e68b4f | 93 | goto retry; |
4bbd4c77 | 94 | } |
8a0516ed | 95 | if ((flags & FOLL_NUMA) && pte_protnone(pte)) |
4bbd4c77 | 96 | goto no_page; |
69e68b4f KS |
97 | if ((flags & FOLL_WRITE) && !pte_write(pte)) { |
98 | pte_unmap_unlock(ptep, ptl); | |
99 | return NULL; | |
100 | } | |
4bbd4c77 KS |
101 | |
102 | page = vm_normal_page(vma, address, pte); | |
3565fce3 DW |
103 | if (!page && pte_devmap(pte) && (flags & FOLL_GET)) { |
104 | /* | |
105 | * Only return device mapping pages in the FOLL_GET case since | |
106 | * they are only valid while holding the pgmap reference. | |
107 | */ | |
108 | pgmap = get_dev_pagemap(pte_pfn(pte), NULL); | |
109 | if (pgmap) | |
110 | page = pte_page(pte); | |
111 | else | |
112 | goto no_page; | |
113 | } else if (unlikely(!page)) { | |
1027e443 KS |
114 | if (flags & FOLL_DUMP) { |
115 | /* Avoid special (like zero) pages in core dumps */ | |
116 | page = ERR_PTR(-EFAULT); | |
117 | goto out; | |
118 | } | |
119 | ||
120 | if (is_zero_pfn(pte_pfn(pte))) { | |
121 | page = pte_page(pte); | |
122 | } else { | |
123 | int ret; | |
124 | ||
125 | ret = follow_pfn_pte(vma, address, ptep, flags); | |
126 | page = ERR_PTR(ret); | |
127 | goto out; | |
128 | } | |
4bbd4c77 KS |
129 | } |
130 | ||
6742d293 KS |
131 | if (flags & FOLL_SPLIT && PageTransCompound(page)) { |
132 | int ret; | |
133 | get_page(page); | |
134 | pte_unmap_unlock(ptep, ptl); | |
135 | lock_page(page); | |
136 | ret = split_huge_page(page); | |
137 | unlock_page(page); | |
138 | put_page(page); | |
139 | if (ret) | |
140 | return ERR_PTR(ret); | |
141 | goto retry; | |
142 | } | |
143 | ||
3565fce3 | 144 | if (flags & FOLL_GET) { |
ddc58f27 | 145 | get_page(page); |
3565fce3 DW |
146 | |
147 | /* drop the pgmap reference now that we hold the page */ | |
148 | if (pgmap) { | |
149 | put_dev_pagemap(pgmap); | |
150 | pgmap = NULL; | |
151 | } | |
152 | } | |
4bbd4c77 KS |
153 | if (flags & FOLL_TOUCH) { |
154 | if ((flags & FOLL_WRITE) && | |
155 | !pte_dirty(pte) && !PageDirty(page)) | |
156 | set_page_dirty(page); | |
157 | /* | |
158 | * pte_mkyoung() would be more correct here, but atomic care | |
159 | * is needed to avoid losing the dirty bit: it is easier to use | |
160 | * mark_page_accessed(). | |
161 | */ | |
162 | mark_page_accessed(page); | |
163 | } | |
de60f5f1 | 164 | if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { |
e90309c9 KS |
165 | /* Do not mlock pte-mapped THP */ |
166 | if (PageTransCompound(page)) | |
167 | goto out; | |
168 | ||
4bbd4c77 KS |
169 | /* |
170 | * The preliminary mapping check is mainly to avoid the | |
171 | * pointless overhead of lock_page on the ZERO_PAGE | |
172 | * which might bounce very badly if there is contention. | |
173 | * | |
174 | * If the page is already locked, we don't need to | |
175 | * handle it now - vmscan will handle it later if and | |
176 | * when it attempts to reclaim the page. | |
177 | */ | |
178 | if (page->mapping && trylock_page(page)) { | |
179 | lru_add_drain(); /* push cached pages to LRU */ | |
180 | /* | |
181 | * Because we lock page here, and migration is | |
182 | * blocked by the pte's page reference, and we | |
183 | * know the page is still mapped, we don't even | |
184 | * need to check for file-cache page truncation. | |
185 | */ | |
186 | mlock_vma_page(page); | |
187 | unlock_page(page); | |
188 | } | |
189 | } | |
1027e443 | 190 | out: |
4bbd4c77 | 191 | pte_unmap_unlock(ptep, ptl); |
4bbd4c77 | 192 | return page; |
4bbd4c77 KS |
193 | no_page: |
194 | pte_unmap_unlock(ptep, ptl); | |
195 | if (!pte_none(pte)) | |
69e68b4f KS |
196 | return NULL; |
197 | return no_page_table(vma, flags); | |
198 | } | |
199 | ||
200 | /** | |
201 | * follow_page_mask - look up a page descriptor from a user-virtual address | |
202 | * @vma: vm_area_struct mapping @address | |
203 | * @address: virtual address to look up | |
204 | * @flags: flags modifying lookup behaviour | |
205 | * @page_mask: on output, *page_mask is set according to the size of the page | |
206 | * | |
207 | * @flags can have FOLL_ flags set, defined in <linux/mm.h> | |
208 | * | |
209 | * Returns the mapped (struct page *), %NULL if no mapping exists, or | |
210 | * an error pointer if there is a mapping to something not represented | |
211 | * by a page descriptor (see also vm_normal_page()). | |
212 | */ | |
213 | struct page *follow_page_mask(struct vm_area_struct *vma, | |
214 | unsigned long address, unsigned int flags, | |
215 | unsigned int *page_mask) | |
216 | { | |
217 | pgd_t *pgd; | |
218 | pud_t *pud; | |
219 | pmd_t *pmd; | |
220 | spinlock_t *ptl; | |
221 | struct page *page; | |
222 | struct mm_struct *mm = vma->vm_mm; | |
223 | ||
224 | *page_mask = 0; | |
225 | ||
226 | page = follow_huge_addr(mm, address, flags & FOLL_WRITE); | |
227 | if (!IS_ERR(page)) { | |
228 | BUG_ON(flags & FOLL_GET); | |
4bbd4c77 | 229 | return page; |
69e68b4f | 230 | } |
4bbd4c77 | 231 | |
69e68b4f KS |
232 | pgd = pgd_offset(mm, address); |
233 | if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) | |
234 | return no_page_table(vma, flags); | |
235 | ||
236 | pud = pud_offset(pgd, address); | |
237 | if (pud_none(*pud)) | |
238 | return no_page_table(vma, flags); | |
239 | if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) { | |
e66f17ff NH |
240 | page = follow_huge_pud(mm, address, pud, flags); |
241 | if (page) | |
242 | return page; | |
243 | return no_page_table(vma, flags); | |
69e68b4f KS |
244 | } |
245 | if (unlikely(pud_bad(*pud))) | |
246 | return no_page_table(vma, flags); | |
247 | ||
248 | pmd = pmd_offset(pud, address); | |
249 | if (pmd_none(*pmd)) | |
250 | return no_page_table(vma, flags); | |
251 | if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) { | |
e66f17ff NH |
252 | page = follow_huge_pmd(mm, address, pmd, flags); |
253 | if (page) | |
254 | return page; | |
255 | return no_page_table(vma, flags); | |
69e68b4f | 256 | } |
8a0516ed | 257 | if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) |
69e68b4f | 258 | return no_page_table(vma, flags); |
3565fce3 DW |
259 | if (pmd_devmap(*pmd)) { |
260 | ptl = pmd_lock(mm, pmd); | |
261 | page = follow_devmap_pmd(vma, address, pmd, flags); | |
262 | spin_unlock(ptl); | |
263 | if (page) | |
264 | return page; | |
265 | } | |
6742d293 KS |
266 | if (likely(!pmd_trans_huge(*pmd))) |
267 | return follow_page_pte(vma, address, pmd, flags); | |
268 | ||
269 | ptl = pmd_lock(mm, pmd); | |
270 | if (unlikely(!pmd_trans_huge(*pmd))) { | |
271 | spin_unlock(ptl); | |
272 | return follow_page_pte(vma, address, pmd, flags); | |
273 | } | |
6742d293 KS |
274 | if (flags & FOLL_SPLIT) { |
275 | int ret; | |
276 | page = pmd_page(*pmd); | |
277 | if (is_huge_zero_page(page)) { | |
278 | spin_unlock(ptl); | |
279 | ret = 0; | |
78ddc534 | 280 | split_huge_pmd(vma, pmd, address); |
6742d293 KS |
281 | } else { |
282 | get_page(page); | |
69e68b4f | 283 | spin_unlock(ptl); |
6742d293 KS |
284 | lock_page(page); |
285 | ret = split_huge_page(page); | |
286 | unlock_page(page); | |
287 | put_page(page); | |
288 | } | |
289 | ||
290 | return ret ? ERR_PTR(ret) : | |
291 | follow_page_pte(vma, address, pmd, flags); | |
69e68b4f | 292 | } |
6742d293 KS |
293 | |
294 | page = follow_trans_huge_pmd(vma, address, pmd, flags); | |
295 | spin_unlock(ptl); | |
296 | *page_mask = HPAGE_PMD_NR - 1; | |
297 | return page; | |
4bbd4c77 KS |
298 | } |
299 | ||
f2b495ca KS |
300 | static int get_gate_page(struct mm_struct *mm, unsigned long address, |
301 | unsigned int gup_flags, struct vm_area_struct **vma, | |
302 | struct page **page) | |
303 | { | |
304 | pgd_t *pgd; | |
305 | pud_t *pud; | |
306 | pmd_t *pmd; | |
307 | pte_t *pte; | |
308 | int ret = -EFAULT; | |
309 | ||
310 | /* user gate pages are read-only */ | |
311 | if (gup_flags & FOLL_WRITE) | |
312 | return -EFAULT; | |
313 | if (address > TASK_SIZE) | |
314 | pgd = pgd_offset_k(address); | |
315 | else | |
316 | pgd = pgd_offset_gate(mm, address); | |
317 | BUG_ON(pgd_none(*pgd)); | |
318 | pud = pud_offset(pgd, address); | |
319 | BUG_ON(pud_none(*pud)); | |
320 | pmd = pmd_offset(pud, address); | |
321 | if (pmd_none(*pmd)) | |
322 | return -EFAULT; | |
323 | VM_BUG_ON(pmd_trans_huge(*pmd)); | |
324 | pte = pte_offset_map(pmd, address); | |
325 | if (pte_none(*pte)) | |
326 | goto unmap; | |
327 | *vma = get_gate_vma(mm); | |
328 | if (!page) | |
329 | goto out; | |
330 | *page = vm_normal_page(*vma, address, *pte); | |
331 | if (!*page) { | |
332 | if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte))) | |
333 | goto unmap; | |
334 | *page = pte_page(*pte); | |
335 | } | |
336 | get_page(*page); | |
337 | out: | |
338 | ret = 0; | |
339 | unmap: | |
340 | pte_unmap(pte); | |
341 | return ret; | |
342 | } | |
343 | ||
9a95f3cf PC |
344 | /* |
345 | * mmap_sem must be held on entry. If @nonblocking != NULL and | |
346 | * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released. | |
347 | * If it is, *@nonblocking will be set to 0 and -EBUSY returned. | |
348 | */ | |
16744483 KS |
349 | static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, |
350 | unsigned long address, unsigned int *flags, int *nonblocking) | |
351 | { | |
352 | struct mm_struct *mm = vma->vm_mm; | |
353 | unsigned int fault_flags = 0; | |
354 | int ret; | |
355 | ||
de60f5f1 EM |
356 | /* mlock all present pages, but do not fault in new pages */ |
357 | if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) | |
358 | return -ENOENT; | |
84d33df2 KS |
359 | /* For mm_populate(), just skip the stack guard page. */ |
360 | if ((*flags & FOLL_POPULATE) && | |
16744483 KS |
361 | (stack_guard_page_start(vma, address) || |
362 | stack_guard_page_end(vma, address + PAGE_SIZE))) | |
363 | return -ENOENT; | |
364 | if (*flags & FOLL_WRITE) | |
365 | fault_flags |= FAULT_FLAG_WRITE; | |
366 | if (nonblocking) | |
367 | fault_flags |= FAULT_FLAG_ALLOW_RETRY; | |
368 | if (*flags & FOLL_NOWAIT) | |
369 | fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; | |
234b239b ALC |
370 | if (*flags & FOLL_TRIED) { |
371 | VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY); | |
372 | fault_flags |= FAULT_FLAG_TRIED; | |
373 | } | |
16744483 KS |
374 | |
375 | ret = handle_mm_fault(mm, vma, address, fault_flags); | |
376 | if (ret & VM_FAULT_ERROR) { | |
377 | if (ret & VM_FAULT_OOM) | |
378 | return -ENOMEM; | |
379 | if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) | |
380 | return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT; | |
33692f27 | 381 | if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV)) |
16744483 KS |
382 | return -EFAULT; |
383 | BUG(); | |
384 | } | |
385 | ||
386 | if (tsk) { | |
387 | if (ret & VM_FAULT_MAJOR) | |
388 | tsk->maj_flt++; | |
389 | else | |
390 | tsk->min_flt++; | |
391 | } | |
392 | ||
393 | if (ret & VM_FAULT_RETRY) { | |
394 | if (nonblocking) | |
395 | *nonblocking = 0; | |
396 | return -EBUSY; | |
397 | } | |
398 | ||
399 | /* | |
400 | * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when | |
401 | * necessary, even if maybe_mkwrite decided not to set pte_write. We | |
402 | * can thus safely do subsequent page lookups as if they were reads. | |
403 | * But only do so when looping for pte_write is futile: in some cases | |
404 | * userspace may also be wanting to write to the gotten user page, | |
405 | * which a read fault here might prevent (a readonly page might get | |
406 | * reCOWed by userspace write). | |
407 | */ | |
408 | if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) | |
409 | *flags &= ~FOLL_WRITE; | |
410 | return 0; | |
411 | } | |
412 | ||
fa5bb209 KS |
413 | static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) |
414 | { | |
415 | vm_flags_t vm_flags = vma->vm_flags; | |
416 | ||
417 | if (vm_flags & (VM_IO | VM_PFNMAP)) | |
418 | return -EFAULT; | |
419 | ||
420 | if (gup_flags & FOLL_WRITE) { | |
421 | if (!(vm_flags & VM_WRITE)) { | |
422 | if (!(gup_flags & FOLL_FORCE)) | |
423 | return -EFAULT; | |
424 | /* | |
425 | * We used to let the write,force case do COW in a | |
426 | * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could | |
427 | * set a breakpoint in a read-only mapping of an | |
428 | * executable, without corrupting the file (yet only | |
429 | * when that file had been opened for writing!). | |
430 | * Anon pages in shared mappings are surprising: now | |
431 | * just reject it. | |
432 | */ | |
46435364 | 433 | if (!is_cow_mapping(vm_flags)) |
fa5bb209 | 434 | return -EFAULT; |
fa5bb209 KS |
435 | } |
436 | } else if (!(vm_flags & VM_READ)) { | |
437 | if (!(gup_flags & FOLL_FORCE)) | |
438 | return -EFAULT; | |
439 | /* | |
440 | * Is there actually any vma we can reach here which does not | |
441 | * have VM_MAYREAD set? | |
442 | */ | |
443 | if (!(vm_flags & VM_MAYREAD)) | |
444 | return -EFAULT; | |
445 | } | |
446 | return 0; | |
447 | } | |
448 | ||
4bbd4c77 KS |
449 | /** |
450 | * __get_user_pages() - pin user pages in memory | |
451 | * @tsk: task_struct of target task | |
452 | * @mm: mm_struct of target mm | |
453 | * @start: starting user address | |
454 | * @nr_pages: number of pages from start to pin | |
455 | * @gup_flags: flags modifying pin behaviour | |
456 | * @pages: array that receives pointers to the pages pinned. | |
457 | * Should be at least nr_pages long. Or NULL, if caller | |
458 | * only intends to ensure the pages are faulted in. | |
459 | * @vmas: array of pointers to vmas corresponding to each page. | |
460 | * Or NULL if the caller does not require them. | |
461 | * @nonblocking: whether waiting for disk IO or mmap_sem contention | |
462 | * | |
463 | * Returns number of pages pinned. This may be fewer than the number | |
464 | * requested. If nr_pages is 0 or negative, returns 0. If no pages | |
465 | * were pinned, returns -errno. Each page returned must be released | |
466 | * with a put_page() call when it is finished with. vmas will only | |
467 | * remain valid while mmap_sem is held. | |
468 | * | |
9a95f3cf | 469 | * Must be called with mmap_sem held. It may be released. See below. |
4bbd4c77 KS |
470 | * |
471 | * __get_user_pages walks a process's page tables and takes a reference to | |
472 | * each struct page that each user address corresponds to at a given | |
473 | * instant. That is, it takes the page that would be accessed if a user | |
474 | * thread accesses the given user virtual address at that instant. | |
475 | * | |
476 | * This does not guarantee that the page exists in the user mappings when | |
477 | * __get_user_pages returns, and there may even be a completely different | |
478 | * page there in some cases (eg. if mmapped pagecache has been invalidated | |
479 | * and subsequently re faulted). However it does guarantee that the page | |
480 | * won't be freed completely. And mostly callers simply care that the page | |
481 | * contains data that was valid *at some point in time*. Typically, an IO | |
482 | * or similar operation cannot guarantee anything stronger anyway because | |
483 | * locks can't be held over the syscall boundary. | |
484 | * | |
485 | * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If | |
486 | * the page is written to, set_page_dirty (or set_page_dirty_lock, as | |
487 | * appropriate) must be called after the page is finished with, and | |
488 | * before put_page is called. | |
489 | * | |
490 | * If @nonblocking != NULL, __get_user_pages will not wait for disk IO | |
491 | * or mmap_sem contention, and if waiting is needed to pin all pages, | |
9a95f3cf PC |
492 | * *@nonblocking will be set to 0. Further, if @gup_flags does not |
493 | * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in | |
494 | * this case. | |
495 | * | |
496 | * A caller using such a combination of @nonblocking and @gup_flags | |
497 | * must therefore hold the mmap_sem for reading only, and recognize | |
498 | * when it's been released. Otherwise, it must be held for either | |
499 | * reading or writing and will not be released. | |
4bbd4c77 KS |
500 | * |
501 | * In most cases, get_user_pages or get_user_pages_fast should be used | |
502 | * instead of __get_user_pages. __get_user_pages should be used only if | |
503 | * you need some special @gup_flags. | |
504 | */ | |
505 | long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, | |
506 | unsigned long start, unsigned long nr_pages, | |
507 | unsigned int gup_flags, struct page **pages, | |
508 | struct vm_area_struct **vmas, int *nonblocking) | |
509 | { | |
fa5bb209 | 510 | long i = 0; |
4bbd4c77 | 511 | unsigned int page_mask; |
fa5bb209 | 512 | struct vm_area_struct *vma = NULL; |
4bbd4c77 KS |
513 | |
514 | if (!nr_pages) | |
515 | return 0; | |
516 | ||
517 | VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); | |
518 | ||
519 | /* | |
520 | * If FOLL_FORCE is set then do not force a full fault as the hinting | |
521 | * fault information is unrelated to the reference behaviour of a task | |
522 | * using the address space | |
523 | */ | |
524 | if (!(gup_flags & FOLL_FORCE)) | |
525 | gup_flags |= FOLL_NUMA; | |
526 | ||
4bbd4c77 | 527 | do { |
fa5bb209 KS |
528 | struct page *page; |
529 | unsigned int foll_flags = gup_flags; | |
530 | unsigned int page_increm; | |
531 | ||
532 | /* first iteration or cross vma bound */ | |
533 | if (!vma || start >= vma->vm_end) { | |
534 | vma = find_extend_vma(mm, start); | |
535 | if (!vma && in_gate_area(mm, start)) { | |
536 | int ret; | |
537 | ret = get_gate_page(mm, start & PAGE_MASK, | |
538 | gup_flags, &vma, | |
539 | pages ? &pages[i] : NULL); | |
540 | if (ret) | |
541 | return i ? : ret; | |
542 | page_mask = 0; | |
543 | goto next_page; | |
544 | } | |
4bbd4c77 | 545 | |
fa5bb209 KS |
546 | if (!vma || check_vma_flags(vma, gup_flags)) |
547 | return i ? : -EFAULT; | |
548 | if (is_vm_hugetlb_page(vma)) { | |
549 | i = follow_hugetlb_page(mm, vma, pages, vmas, | |
550 | &start, &nr_pages, i, | |
551 | gup_flags); | |
552 | continue; | |
4bbd4c77 | 553 | } |
fa5bb209 KS |
554 | } |
555 | retry: | |
556 | /* | |
557 | * If we have a pending SIGKILL, don't keep faulting pages and | |
558 | * potentially allocating memory. | |
559 | */ | |
560 | if (unlikely(fatal_signal_pending(current))) | |
561 | return i ? i : -ERESTARTSYS; | |
562 | cond_resched(); | |
563 | page = follow_page_mask(vma, start, foll_flags, &page_mask); | |
564 | if (!page) { | |
565 | int ret; | |
566 | ret = faultin_page(tsk, vma, start, &foll_flags, | |
567 | nonblocking); | |
568 | switch (ret) { | |
569 | case 0: | |
570 | goto retry; | |
571 | case -EFAULT: | |
572 | case -ENOMEM: | |
573 | case -EHWPOISON: | |
574 | return i ? i : ret; | |
575 | case -EBUSY: | |
576 | return i; | |
577 | case -ENOENT: | |
578 | goto next_page; | |
4bbd4c77 | 579 | } |
fa5bb209 | 580 | BUG(); |
1027e443 KS |
581 | } else if (PTR_ERR(page) == -EEXIST) { |
582 | /* | |
583 | * Proper page table entry exists, but no corresponding | |
584 | * struct page. | |
585 | */ | |
586 | goto next_page; | |
587 | } else if (IS_ERR(page)) { | |
fa5bb209 | 588 | return i ? i : PTR_ERR(page); |
1027e443 | 589 | } |
fa5bb209 KS |
590 | if (pages) { |
591 | pages[i] = page; | |
592 | flush_anon_page(vma, page, start); | |
593 | flush_dcache_page(page); | |
594 | page_mask = 0; | |
4bbd4c77 | 595 | } |
4bbd4c77 | 596 | next_page: |
fa5bb209 KS |
597 | if (vmas) { |
598 | vmas[i] = vma; | |
599 | page_mask = 0; | |
600 | } | |
601 | page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); | |
602 | if (page_increm > nr_pages) | |
603 | page_increm = nr_pages; | |
604 | i += page_increm; | |
605 | start += page_increm * PAGE_SIZE; | |
606 | nr_pages -= page_increm; | |
4bbd4c77 KS |
607 | } while (nr_pages); |
608 | return i; | |
4bbd4c77 KS |
609 | } |
610 | EXPORT_SYMBOL(__get_user_pages); | |
611 | ||
612 | /* | |
613 | * fixup_user_fault() - manually resolve a user page fault | |
614 | * @tsk: the task_struct to use for page fault accounting, or | |
615 | * NULL if faults are not to be recorded. | |
616 | * @mm: mm_struct of target mm | |
617 | * @address: user address | |
618 | * @fault_flags:flags to pass down to handle_mm_fault() | |
4a9e1cda DD |
619 | * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller |
620 | * does not allow retry | |
4bbd4c77 KS |
621 | * |
622 | * This is meant to be called in the specific scenario where for locking reasons | |
623 | * we try to access user memory in atomic context (within a pagefault_disable() | |
624 | * section), this returns -EFAULT, and we want to resolve the user fault before | |
625 | * trying again. | |
626 | * | |
627 | * Typically this is meant to be used by the futex code. | |
628 | * | |
629 | * The main difference with get_user_pages() is that this function will | |
630 | * unconditionally call handle_mm_fault() which will in turn perform all the | |
631 | * necessary SW fixup of the dirty and young bits in the PTE, while | |
4a9e1cda | 632 | * get_user_pages() only guarantees to update these in the struct page. |
4bbd4c77 KS |
633 | * |
634 | * This is important for some architectures where those bits also gate the | |
635 | * access permission to the page because they are maintained in software. On | |
636 | * such architectures, gup() will not be enough to make a subsequent access | |
637 | * succeed. | |
638 | * | |
4a9e1cda DD |
639 | * This function will not return with an unlocked mmap_sem. So it has not the |
640 | * same semantics wrt the @mm->mmap_sem as does filemap_fault(). | |
4bbd4c77 KS |
641 | */ |
642 | int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, | |
4a9e1cda DD |
643 | unsigned long address, unsigned int fault_flags, |
644 | bool *unlocked) | |
4bbd4c77 KS |
645 | { |
646 | struct vm_area_struct *vma; | |
647 | vm_flags_t vm_flags; | |
4a9e1cda DD |
648 | int ret, major = 0; |
649 | ||
650 | if (unlocked) | |
651 | fault_flags |= FAULT_FLAG_ALLOW_RETRY; | |
4bbd4c77 | 652 | |
4a9e1cda | 653 | retry: |
4bbd4c77 KS |
654 | vma = find_extend_vma(mm, address); |
655 | if (!vma || address < vma->vm_start) | |
656 | return -EFAULT; | |
657 | ||
658 | vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ; | |
659 | if (!(vm_flags & vma->vm_flags)) | |
660 | return -EFAULT; | |
661 | ||
662 | ret = handle_mm_fault(mm, vma, address, fault_flags); | |
4a9e1cda | 663 | major |= ret & VM_FAULT_MAJOR; |
4bbd4c77 KS |
664 | if (ret & VM_FAULT_ERROR) { |
665 | if (ret & VM_FAULT_OOM) | |
666 | return -ENOMEM; | |
667 | if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) | |
668 | return -EHWPOISON; | |
33692f27 | 669 | if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV)) |
4bbd4c77 KS |
670 | return -EFAULT; |
671 | BUG(); | |
672 | } | |
4a9e1cda DD |
673 | |
674 | if (ret & VM_FAULT_RETRY) { | |
675 | down_read(&mm->mmap_sem); | |
676 | if (!(fault_flags & FAULT_FLAG_TRIED)) { | |
677 | *unlocked = true; | |
678 | fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; | |
679 | fault_flags |= FAULT_FLAG_TRIED; | |
680 | goto retry; | |
681 | } | |
682 | } | |
683 | ||
4bbd4c77 | 684 | if (tsk) { |
4a9e1cda | 685 | if (major) |
4bbd4c77 KS |
686 | tsk->maj_flt++; |
687 | else | |
688 | tsk->min_flt++; | |
689 | } | |
690 | return 0; | |
691 | } | |
692 | ||
f0818f47 AA |
693 | static __always_inline long __get_user_pages_locked(struct task_struct *tsk, |
694 | struct mm_struct *mm, | |
695 | unsigned long start, | |
696 | unsigned long nr_pages, | |
697 | int write, int force, | |
698 | struct page **pages, | |
699 | struct vm_area_struct **vmas, | |
0fd71a56 AA |
700 | int *locked, bool notify_drop, |
701 | unsigned int flags) | |
f0818f47 | 702 | { |
f0818f47 AA |
703 | long ret, pages_done; |
704 | bool lock_dropped; | |
705 | ||
706 | if (locked) { | |
707 | /* if VM_FAULT_RETRY can be returned, vmas become invalid */ | |
708 | BUG_ON(vmas); | |
709 | /* check caller initialized locked */ | |
710 | BUG_ON(*locked != 1); | |
711 | } | |
712 | ||
713 | if (pages) | |
714 | flags |= FOLL_GET; | |
715 | if (write) | |
716 | flags |= FOLL_WRITE; | |
717 | if (force) | |
718 | flags |= FOLL_FORCE; | |
719 | ||
720 | pages_done = 0; | |
721 | lock_dropped = false; | |
722 | for (;;) { | |
723 | ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages, | |
724 | vmas, locked); | |
725 | if (!locked) | |
726 | /* VM_FAULT_RETRY couldn't trigger, bypass */ | |
727 | return ret; | |
728 | ||
729 | /* VM_FAULT_RETRY cannot return errors */ | |
730 | if (!*locked) { | |
731 | BUG_ON(ret < 0); | |
732 | BUG_ON(ret >= nr_pages); | |
733 | } | |
734 | ||
735 | if (!pages) | |
736 | /* If it's a prefault don't insist harder */ | |
737 | return ret; | |
738 | ||
739 | if (ret > 0) { | |
740 | nr_pages -= ret; | |
741 | pages_done += ret; | |
742 | if (!nr_pages) | |
743 | break; | |
744 | } | |
745 | if (*locked) { | |
746 | /* VM_FAULT_RETRY didn't trigger */ | |
747 | if (!pages_done) | |
748 | pages_done = ret; | |
749 | break; | |
750 | } | |
751 | /* VM_FAULT_RETRY triggered, so seek to the faulting offset */ | |
752 | pages += ret; | |
753 | start += ret << PAGE_SHIFT; | |
754 | ||
755 | /* | |
756 | * Repeat on the address that fired VM_FAULT_RETRY | |
757 | * without FAULT_FLAG_ALLOW_RETRY but with | |
758 | * FAULT_FLAG_TRIED. | |
759 | */ | |
760 | *locked = 1; | |
761 | lock_dropped = true; | |
762 | down_read(&mm->mmap_sem); | |
763 | ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, | |
764 | pages, NULL, NULL); | |
765 | if (ret != 1) { | |
766 | BUG_ON(ret > 1); | |
767 | if (!pages_done) | |
768 | pages_done = ret; | |
769 | break; | |
770 | } | |
771 | nr_pages--; | |
772 | pages_done++; | |
773 | if (!nr_pages) | |
774 | break; | |
775 | pages++; | |
776 | start += PAGE_SIZE; | |
777 | } | |
778 | if (notify_drop && lock_dropped && *locked) { | |
779 | /* | |
780 | * We must let the caller know we temporarily dropped the lock | |
781 | * and so the critical section protected by it was lost. | |
782 | */ | |
783 | up_read(&mm->mmap_sem); | |
784 | *locked = 0; | |
785 | } | |
786 | return pages_done; | |
787 | } | |
788 | ||
789 | /* | |
790 | * We can leverage the VM_FAULT_RETRY functionality in the page fault | |
791 | * paths better by using either get_user_pages_locked() or | |
792 | * get_user_pages_unlocked(). | |
793 | * | |
794 | * get_user_pages_locked() is suitable to replace the form: | |
795 | * | |
796 | * down_read(&mm->mmap_sem); | |
797 | * do_something() | |
798 | * get_user_pages(tsk, mm, ..., pages, NULL); | |
799 | * up_read(&mm->mmap_sem); | |
800 | * | |
801 | * to: | |
802 | * | |
803 | * int locked = 1; | |
804 | * down_read(&mm->mmap_sem); | |
805 | * do_something() | |
806 | * get_user_pages_locked(tsk, mm, ..., pages, &locked); | |
807 | * if (locked) | |
808 | * up_read(&mm->mmap_sem); | |
809 | */ | |
810 | long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm, | |
811 | unsigned long start, unsigned long nr_pages, | |
812 | int write, int force, struct page **pages, | |
813 | int *locked) | |
814 | { | |
815 | return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, | |
0fd71a56 | 816 | pages, NULL, locked, true, FOLL_TOUCH); |
f0818f47 AA |
817 | } |
818 | EXPORT_SYMBOL(get_user_pages_locked); | |
819 | ||
0fd71a56 AA |
820 | /* |
821 | * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to | |
822 | * pass additional gup_flags as last parameter (like FOLL_HWPOISON). | |
823 | * | |
824 | * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the | |
825 | * caller if required (just like with __get_user_pages). "FOLL_GET", | |
826 | * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed | |
827 | * according to the parameters "pages", "write", "force" | |
828 | * respectively. | |
829 | */ | |
830 | __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, | |
831 | unsigned long start, unsigned long nr_pages, | |
832 | int write, int force, struct page **pages, | |
833 | unsigned int gup_flags) | |
834 | { | |
835 | long ret; | |
836 | int locked = 1; | |
837 | down_read(&mm->mmap_sem); | |
838 | ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, | |
839 | pages, NULL, &locked, false, gup_flags); | |
840 | if (locked) | |
841 | up_read(&mm->mmap_sem); | |
842 | return ret; | |
843 | } | |
844 | EXPORT_SYMBOL(__get_user_pages_unlocked); | |
845 | ||
f0818f47 AA |
846 | /* |
847 | * get_user_pages_unlocked() is suitable to replace the form: | |
848 | * | |
849 | * down_read(&mm->mmap_sem); | |
850 | * get_user_pages(tsk, mm, ..., pages, NULL); | |
851 | * up_read(&mm->mmap_sem); | |
852 | * | |
853 | * with: | |
854 | * | |
855 | * get_user_pages_unlocked(tsk, mm, ..., pages); | |
856 | * | |
857 | * It is functionally equivalent to get_user_pages_fast so | |
858 | * get_user_pages_fast should be used instead, if the two parameters | |
859 | * "tsk" and "mm" are respectively equal to current and current->mm, | |
860 | * or if "force" shall be set to 1 (get_user_pages_fast misses the | |
861 | * "force" parameter). | |
862 | */ | |
863 | long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, | |
864 | unsigned long start, unsigned long nr_pages, | |
865 | int write, int force, struct page **pages) | |
866 | { | |
0fd71a56 AA |
867 | return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write, |
868 | force, pages, FOLL_TOUCH); | |
f0818f47 AA |
869 | } |
870 | EXPORT_SYMBOL(get_user_pages_unlocked); | |
871 | ||
4bbd4c77 KS |
872 | /* |
873 | * get_user_pages() - pin user pages in memory | |
874 | * @tsk: the task_struct to use for page fault accounting, or | |
875 | * NULL if faults are not to be recorded. | |
876 | * @mm: mm_struct of target mm | |
877 | * @start: starting user address | |
878 | * @nr_pages: number of pages from start to pin | |
879 | * @write: whether pages will be written to by the caller | |
880 | * @force: whether to force access even when user mapping is currently | |
881 | * protected (but never forces write access to shared mapping). | |
882 | * @pages: array that receives pointers to the pages pinned. | |
883 | * Should be at least nr_pages long. Or NULL, if caller | |
884 | * only intends to ensure the pages are faulted in. | |
885 | * @vmas: array of pointers to vmas corresponding to each page. | |
886 | * Or NULL if the caller does not require them. | |
887 | * | |
888 | * Returns number of pages pinned. This may be fewer than the number | |
889 | * requested. If nr_pages is 0 or negative, returns 0. If no pages | |
890 | * were pinned, returns -errno. Each page returned must be released | |
891 | * with a put_page() call when it is finished with. vmas will only | |
892 | * remain valid while mmap_sem is held. | |
893 | * | |
894 | * Must be called with mmap_sem held for read or write. | |
895 | * | |
896 | * get_user_pages walks a process's page tables and takes a reference to | |
897 | * each struct page that each user address corresponds to at a given | |
898 | * instant. That is, it takes the page that would be accessed if a user | |
899 | * thread accesses the given user virtual address at that instant. | |
900 | * | |
901 | * This does not guarantee that the page exists in the user mappings when | |
902 | * get_user_pages returns, and there may even be a completely different | |
903 | * page there in some cases (eg. if mmapped pagecache has been invalidated | |
904 | * and subsequently re faulted). However it does guarantee that the page | |
905 | * won't be freed completely. And mostly callers simply care that the page | |
906 | * contains data that was valid *at some point in time*. Typically, an IO | |
907 | * or similar operation cannot guarantee anything stronger anyway because | |
908 | * locks can't be held over the syscall boundary. | |
909 | * | |
910 | * If write=0, the page must not be written to. If the page is written to, | |
911 | * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called | |
912 | * after the page is finished with, and before put_page is called. | |
913 | * | |
914 | * get_user_pages is typically used for fewer-copy IO operations, to get a | |
915 | * handle on the memory by some means other than accesses via the user virtual | |
916 | * addresses. The pages may be submitted for DMA to devices or accessed via | |
917 | * their kernel linear mapping (via the kmap APIs). Care should be taken to | |
918 | * use the correct cache flushing APIs. | |
919 | * | |
920 | * See also get_user_pages_fast, for performance critical applications. | |
f0818f47 AA |
921 | * |
922 | * get_user_pages should be phased out in favor of | |
923 | * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing | |
924 | * should use get_user_pages because it cannot pass | |
925 | * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. | |
4bbd4c77 KS |
926 | */ |
927 | long get_user_pages(struct task_struct *tsk, struct mm_struct *mm, | |
928 | unsigned long start, unsigned long nr_pages, int write, | |
929 | int force, struct page **pages, struct vm_area_struct **vmas) | |
930 | { | |
f0818f47 | 931 | return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, |
0fd71a56 | 932 | pages, vmas, NULL, false, FOLL_TOUCH); |
4bbd4c77 KS |
933 | } |
934 | EXPORT_SYMBOL(get_user_pages); | |
935 | ||
acc3c8d1 KS |
936 | /** |
937 | * populate_vma_page_range() - populate a range of pages in the vma. | |
938 | * @vma: target vma | |
939 | * @start: start address | |
940 | * @end: end address | |
941 | * @nonblocking: | |
942 | * | |
943 | * This takes care of mlocking the pages too if VM_LOCKED is set. | |
944 | * | |
945 | * return 0 on success, negative error code on error. | |
946 | * | |
947 | * vma->vm_mm->mmap_sem must be held. | |
948 | * | |
949 | * If @nonblocking is NULL, it may be held for read or write and will | |
950 | * be unperturbed. | |
951 | * | |
952 | * If @nonblocking is non-NULL, it must held for read only and may be | |
953 | * released. If it's released, *@nonblocking will be set to 0. | |
954 | */ | |
955 | long populate_vma_page_range(struct vm_area_struct *vma, | |
956 | unsigned long start, unsigned long end, int *nonblocking) | |
957 | { | |
958 | struct mm_struct *mm = vma->vm_mm; | |
959 | unsigned long nr_pages = (end - start) / PAGE_SIZE; | |
960 | int gup_flags; | |
961 | ||
962 | VM_BUG_ON(start & ~PAGE_MASK); | |
963 | VM_BUG_ON(end & ~PAGE_MASK); | |
964 | VM_BUG_ON_VMA(start < vma->vm_start, vma); | |
965 | VM_BUG_ON_VMA(end > vma->vm_end, vma); | |
966 | VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); | |
967 | ||
de60f5f1 EM |
968 | gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK; |
969 | if (vma->vm_flags & VM_LOCKONFAULT) | |
970 | gup_flags &= ~FOLL_POPULATE; | |
acc3c8d1 KS |
971 | /* |
972 | * We want to touch writable mappings with a write fault in order | |
973 | * to break COW, except for shared mappings because these don't COW | |
974 | * and we would not want to dirty them for nothing. | |
975 | */ | |
976 | if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) | |
977 | gup_flags |= FOLL_WRITE; | |
978 | ||
979 | /* | |
980 | * We want mlock to succeed for regions that have any permissions | |
981 | * other than PROT_NONE. | |
982 | */ | |
983 | if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) | |
984 | gup_flags |= FOLL_FORCE; | |
985 | ||
986 | /* | |
987 | * We made sure addr is within a VMA, so the following will | |
988 | * not result in a stack expansion that recurses back here. | |
989 | */ | |
990 | return __get_user_pages(current, mm, start, nr_pages, gup_flags, | |
991 | NULL, NULL, nonblocking); | |
992 | } | |
993 | ||
994 | /* | |
995 | * __mm_populate - populate and/or mlock pages within a range of address space. | |
996 | * | |
997 | * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap | |
998 | * flags. VMAs must be already marked with the desired vm_flags, and | |
999 | * mmap_sem must not be held. | |
1000 | */ | |
1001 | int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) | |
1002 | { | |
1003 | struct mm_struct *mm = current->mm; | |
1004 | unsigned long end, nstart, nend; | |
1005 | struct vm_area_struct *vma = NULL; | |
1006 | int locked = 0; | |
1007 | long ret = 0; | |
1008 | ||
1009 | VM_BUG_ON(start & ~PAGE_MASK); | |
1010 | VM_BUG_ON(len != PAGE_ALIGN(len)); | |
1011 | end = start + len; | |
1012 | ||
1013 | for (nstart = start; nstart < end; nstart = nend) { | |
1014 | /* | |
1015 | * We want to fault in pages for [nstart; end) address range. | |
1016 | * Find first corresponding VMA. | |
1017 | */ | |
1018 | if (!locked) { | |
1019 | locked = 1; | |
1020 | down_read(&mm->mmap_sem); | |
1021 | vma = find_vma(mm, nstart); | |
1022 | } else if (nstart >= vma->vm_end) | |
1023 | vma = vma->vm_next; | |
1024 | if (!vma || vma->vm_start >= end) | |
1025 | break; | |
1026 | /* | |
1027 | * Set [nstart; nend) to intersection of desired address | |
1028 | * range with the first VMA. Also, skip undesirable VMA types. | |
1029 | */ | |
1030 | nend = min(end, vma->vm_end); | |
1031 | if (vma->vm_flags & (VM_IO | VM_PFNMAP)) | |
1032 | continue; | |
1033 | if (nstart < vma->vm_start) | |
1034 | nstart = vma->vm_start; | |
1035 | /* | |
1036 | * Now fault in a range of pages. populate_vma_page_range() | |
1037 | * double checks the vma flags, so that it won't mlock pages | |
1038 | * if the vma was already munlocked. | |
1039 | */ | |
1040 | ret = populate_vma_page_range(vma, nstart, nend, &locked); | |
1041 | if (ret < 0) { | |
1042 | if (ignore_errors) { | |
1043 | ret = 0; | |
1044 | continue; /* continue at next VMA */ | |
1045 | } | |
1046 | break; | |
1047 | } | |
1048 | nend = nstart + ret * PAGE_SIZE; | |
1049 | ret = 0; | |
1050 | } | |
1051 | if (locked) | |
1052 | up_read(&mm->mmap_sem); | |
1053 | return ret; /* 0 or negative error code */ | |
1054 | } | |
1055 | ||
4bbd4c77 KS |
1056 | /** |
1057 | * get_dump_page() - pin user page in memory while writing it to core dump | |
1058 | * @addr: user address | |
1059 | * | |
1060 | * Returns struct page pointer of user page pinned for dump, | |
1061 | * to be freed afterwards by page_cache_release() or put_page(). | |
1062 | * | |
1063 | * Returns NULL on any kind of failure - a hole must then be inserted into | |
1064 | * the corefile, to preserve alignment with its headers; and also returns | |
1065 | * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - | |
1066 | * allowing a hole to be left in the corefile to save diskspace. | |
1067 | * | |
1068 | * Called without mmap_sem, but after all other threads have been killed. | |
1069 | */ | |
1070 | #ifdef CONFIG_ELF_CORE | |
1071 | struct page *get_dump_page(unsigned long addr) | |
1072 | { | |
1073 | struct vm_area_struct *vma; | |
1074 | struct page *page; | |
1075 | ||
1076 | if (__get_user_pages(current, current->mm, addr, 1, | |
1077 | FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, | |
1078 | NULL) < 1) | |
1079 | return NULL; | |
1080 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
1081 | return page; | |
1082 | } | |
1083 | #endif /* CONFIG_ELF_CORE */ | |
2667f50e SC |
1084 | |
1085 | /* | |
1086 | * Generic RCU Fast GUP | |
1087 | * | |
1088 | * get_user_pages_fast attempts to pin user pages by walking the page | |
1089 | * tables directly and avoids taking locks. Thus the walker needs to be | |
1090 | * protected from page table pages being freed from under it, and should | |
1091 | * block any THP splits. | |
1092 | * | |
1093 | * One way to achieve this is to have the walker disable interrupts, and | |
1094 | * rely on IPIs from the TLB flushing code blocking before the page table | |
1095 | * pages are freed. This is unsuitable for architectures that do not need | |
1096 | * to broadcast an IPI when invalidating TLBs. | |
1097 | * | |
1098 | * Another way to achieve this is to batch up page table containing pages | |
1099 | * belonging to more than one mm_user, then rcu_sched a callback to free those | |
1100 | * pages. Disabling interrupts will allow the fast_gup walker to both block | |
1101 | * the rcu_sched callback, and an IPI that we broadcast for splitting THPs | |
1102 | * (which is a relatively rare event). The code below adopts this strategy. | |
1103 | * | |
1104 | * Before activating this code, please be aware that the following assumptions | |
1105 | * are currently made: | |
1106 | * | |
1107 | * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free | |
1108 | * pages containing page tables. | |
1109 | * | |
2667f50e SC |
1110 | * *) ptes can be read atomically by the architecture. |
1111 | * | |
1112 | * *) access_ok is sufficient to validate userspace address ranges. | |
1113 | * | |
1114 | * The last two assumptions can be relaxed by the addition of helper functions. | |
1115 | * | |
1116 | * This code is based heavily on the PowerPC implementation by Nick Piggin. | |
1117 | */ | |
1118 | #ifdef CONFIG_HAVE_GENERIC_RCU_GUP | |
1119 | ||
1120 | #ifdef __HAVE_ARCH_PTE_SPECIAL | |
1121 | static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, | |
1122 | int write, struct page **pages, int *nr) | |
1123 | { | |
1124 | pte_t *ptep, *ptem; | |
1125 | int ret = 0; | |
1126 | ||
1127 | ptem = ptep = pte_offset_map(&pmd, addr); | |
1128 | do { | |
1129 | /* | |
1130 | * In the line below we are assuming that the pte can be read | |
1131 | * atomically. If this is not the case for your architecture, | |
1132 | * please wrap this in a helper function! | |
1133 | * | |
1134 | * for an example see gup_get_pte in arch/x86/mm/gup.c | |
1135 | */ | |
9d8c47e4 | 1136 | pte_t pte = READ_ONCE(*ptep); |
7aef4172 | 1137 | struct page *head, *page; |
2667f50e SC |
1138 | |
1139 | /* | |
1140 | * Similar to the PMD case below, NUMA hinting must take slow | |
8a0516ed | 1141 | * path using the pte_protnone check. |
2667f50e SC |
1142 | */ |
1143 | if (!pte_present(pte) || pte_special(pte) || | |
8a0516ed | 1144 | pte_protnone(pte) || (write && !pte_write(pte))) |
2667f50e SC |
1145 | goto pte_unmap; |
1146 | ||
1147 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | |
1148 | page = pte_page(pte); | |
7aef4172 | 1149 | head = compound_head(page); |
2667f50e | 1150 | |
7aef4172 | 1151 | if (!page_cache_get_speculative(head)) |
2667f50e SC |
1152 | goto pte_unmap; |
1153 | ||
1154 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { | |
7aef4172 | 1155 | put_page(head); |
2667f50e SC |
1156 | goto pte_unmap; |
1157 | } | |
1158 | ||
7aef4172 | 1159 | VM_BUG_ON_PAGE(compound_head(page) != head, page); |
2667f50e SC |
1160 | pages[*nr] = page; |
1161 | (*nr)++; | |
1162 | ||
1163 | } while (ptep++, addr += PAGE_SIZE, addr != end); | |
1164 | ||
1165 | ret = 1; | |
1166 | ||
1167 | pte_unmap: | |
1168 | pte_unmap(ptem); | |
1169 | return ret; | |
1170 | } | |
1171 | #else | |
1172 | ||
1173 | /* | |
1174 | * If we can't determine whether or not a pte is special, then fail immediately | |
1175 | * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not | |
1176 | * to be special. | |
1177 | * | |
1178 | * For a futex to be placed on a THP tail page, get_futex_key requires a | |
1179 | * __get_user_pages_fast implementation that can pin pages. Thus it's still | |
1180 | * useful to have gup_huge_pmd even if we can't operate on ptes. | |
1181 | */ | |
1182 | static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, | |
1183 | int write, struct page **pages, int *nr) | |
1184 | { | |
1185 | return 0; | |
1186 | } | |
1187 | #endif /* __HAVE_ARCH_PTE_SPECIAL */ | |
1188 | ||
1189 | static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, | |
1190 | unsigned long end, int write, struct page **pages, int *nr) | |
1191 | { | |
ddc58f27 | 1192 | struct page *head, *page; |
2667f50e SC |
1193 | int refs; |
1194 | ||
1195 | if (write && !pmd_write(orig)) | |
1196 | return 0; | |
1197 | ||
1198 | refs = 0; | |
1199 | head = pmd_page(orig); | |
1200 | page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); | |
2667f50e SC |
1201 | do { |
1202 | VM_BUG_ON_PAGE(compound_head(page) != head, page); | |
1203 | pages[*nr] = page; | |
1204 | (*nr)++; | |
1205 | page++; | |
1206 | refs++; | |
1207 | } while (addr += PAGE_SIZE, addr != end); | |
1208 | ||
1209 | if (!page_cache_add_speculative(head, refs)) { | |
1210 | *nr -= refs; | |
1211 | return 0; | |
1212 | } | |
1213 | ||
1214 | if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { | |
1215 | *nr -= refs; | |
1216 | while (refs--) | |
1217 | put_page(head); | |
1218 | return 0; | |
1219 | } | |
1220 | ||
2667f50e SC |
1221 | return 1; |
1222 | } | |
1223 | ||
1224 | static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, | |
1225 | unsigned long end, int write, struct page **pages, int *nr) | |
1226 | { | |
ddc58f27 | 1227 | struct page *head, *page; |
2667f50e SC |
1228 | int refs; |
1229 | ||
1230 | if (write && !pud_write(orig)) | |
1231 | return 0; | |
1232 | ||
1233 | refs = 0; | |
1234 | head = pud_page(orig); | |
1235 | page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); | |
2667f50e SC |
1236 | do { |
1237 | VM_BUG_ON_PAGE(compound_head(page) != head, page); | |
1238 | pages[*nr] = page; | |
1239 | (*nr)++; | |
1240 | page++; | |
1241 | refs++; | |
1242 | } while (addr += PAGE_SIZE, addr != end); | |
1243 | ||
1244 | if (!page_cache_add_speculative(head, refs)) { | |
1245 | *nr -= refs; | |
1246 | return 0; | |
1247 | } | |
1248 | ||
1249 | if (unlikely(pud_val(orig) != pud_val(*pudp))) { | |
1250 | *nr -= refs; | |
1251 | while (refs--) | |
1252 | put_page(head); | |
1253 | return 0; | |
1254 | } | |
1255 | ||
2667f50e SC |
1256 | return 1; |
1257 | } | |
1258 | ||
f30c59e9 AK |
1259 | static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, |
1260 | unsigned long end, int write, | |
1261 | struct page **pages, int *nr) | |
1262 | { | |
1263 | int refs; | |
ddc58f27 | 1264 | struct page *head, *page; |
f30c59e9 AK |
1265 | |
1266 | if (write && !pgd_write(orig)) | |
1267 | return 0; | |
1268 | ||
1269 | refs = 0; | |
1270 | head = pgd_page(orig); | |
1271 | page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); | |
f30c59e9 AK |
1272 | do { |
1273 | VM_BUG_ON_PAGE(compound_head(page) != head, page); | |
1274 | pages[*nr] = page; | |
1275 | (*nr)++; | |
1276 | page++; | |
1277 | refs++; | |
1278 | } while (addr += PAGE_SIZE, addr != end); | |
1279 | ||
1280 | if (!page_cache_add_speculative(head, refs)) { | |
1281 | *nr -= refs; | |
1282 | return 0; | |
1283 | } | |
1284 | ||
1285 | if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { | |
1286 | *nr -= refs; | |
1287 | while (refs--) | |
1288 | put_page(head); | |
1289 | return 0; | |
1290 | } | |
1291 | ||
f30c59e9 AK |
1292 | return 1; |
1293 | } | |
1294 | ||
2667f50e SC |
1295 | static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
1296 | int write, struct page **pages, int *nr) | |
1297 | { | |
1298 | unsigned long next; | |
1299 | pmd_t *pmdp; | |
1300 | ||
1301 | pmdp = pmd_offset(&pud, addr); | |
1302 | do { | |
38c5ce93 | 1303 | pmd_t pmd = READ_ONCE(*pmdp); |
2667f50e SC |
1304 | |
1305 | next = pmd_addr_end(addr, end); | |
4b471e88 | 1306 | if (pmd_none(pmd)) |
2667f50e SC |
1307 | return 0; |
1308 | ||
1309 | if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) { | |
1310 | /* | |
1311 | * NUMA hinting faults need to be handled in the GUP | |
1312 | * slowpath for accounting purposes and so that they | |
1313 | * can be serialised against THP migration. | |
1314 | */ | |
8a0516ed | 1315 | if (pmd_protnone(pmd)) |
2667f50e SC |
1316 | return 0; |
1317 | ||
1318 | if (!gup_huge_pmd(pmd, pmdp, addr, next, write, | |
1319 | pages, nr)) | |
1320 | return 0; | |
1321 | ||
f30c59e9 AK |
1322 | } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { |
1323 | /* | |
1324 | * architecture have different format for hugetlbfs | |
1325 | * pmd format and THP pmd format | |
1326 | */ | |
1327 | if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, | |
1328 | PMD_SHIFT, next, write, pages, nr)) | |
1329 | return 0; | |
2667f50e SC |
1330 | } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) |
1331 | return 0; | |
1332 | } while (pmdp++, addr = next, addr != end); | |
1333 | ||
1334 | return 1; | |
1335 | } | |
1336 | ||
f30c59e9 AK |
1337 | static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, |
1338 | int write, struct page **pages, int *nr) | |
2667f50e SC |
1339 | { |
1340 | unsigned long next; | |
1341 | pud_t *pudp; | |
1342 | ||
f30c59e9 | 1343 | pudp = pud_offset(&pgd, addr); |
2667f50e | 1344 | do { |
e37c6982 | 1345 | pud_t pud = READ_ONCE(*pudp); |
2667f50e SC |
1346 | |
1347 | next = pud_addr_end(addr, end); | |
1348 | if (pud_none(pud)) | |
1349 | return 0; | |
f30c59e9 | 1350 | if (unlikely(pud_huge(pud))) { |
2667f50e | 1351 | if (!gup_huge_pud(pud, pudp, addr, next, write, |
f30c59e9 AK |
1352 | pages, nr)) |
1353 | return 0; | |
1354 | } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { | |
1355 | if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, | |
1356 | PUD_SHIFT, next, write, pages, nr)) | |
2667f50e SC |
1357 | return 0; |
1358 | } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) | |
1359 | return 0; | |
1360 | } while (pudp++, addr = next, addr != end); | |
1361 | ||
1362 | return 1; | |
1363 | } | |
1364 | ||
1365 | /* | |
1366 | * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to | |
1367 | * the regular GUP. It will only return non-negative values. | |
1368 | */ | |
1369 | int __get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
1370 | struct page **pages) | |
1371 | { | |
1372 | struct mm_struct *mm = current->mm; | |
1373 | unsigned long addr, len, end; | |
1374 | unsigned long next, flags; | |
1375 | pgd_t *pgdp; | |
1376 | int nr = 0; | |
1377 | ||
1378 | start &= PAGE_MASK; | |
1379 | addr = start; | |
1380 | len = (unsigned long) nr_pages << PAGE_SHIFT; | |
1381 | end = start + len; | |
1382 | ||
1383 | if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, | |
1384 | start, len))) | |
1385 | return 0; | |
1386 | ||
1387 | /* | |
1388 | * Disable interrupts. We use the nested form as we can already have | |
1389 | * interrupts disabled by get_futex_key. | |
1390 | * | |
1391 | * With interrupts disabled, we block page table pages from being | |
1392 | * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h | |
1393 | * for more details. | |
1394 | * | |
1395 | * We do not adopt an rcu_read_lock(.) here as we also want to | |
1396 | * block IPIs that come from THPs splitting. | |
1397 | */ | |
1398 | ||
1399 | local_irq_save(flags); | |
1400 | pgdp = pgd_offset(mm, addr); | |
1401 | do { | |
9d8c47e4 | 1402 | pgd_t pgd = READ_ONCE(*pgdp); |
f30c59e9 | 1403 | |
2667f50e | 1404 | next = pgd_addr_end(addr, end); |
f30c59e9 | 1405 | if (pgd_none(pgd)) |
2667f50e | 1406 | break; |
f30c59e9 AK |
1407 | if (unlikely(pgd_huge(pgd))) { |
1408 | if (!gup_huge_pgd(pgd, pgdp, addr, next, write, | |
1409 | pages, &nr)) | |
1410 | break; | |
1411 | } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { | |
1412 | if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, | |
1413 | PGDIR_SHIFT, next, write, pages, &nr)) | |
1414 | break; | |
1415 | } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) | |
2667f50e SC |
1416 | break; |
1417 | } while (pgdp++, addr = next, addr != end); | |
1418 | local_irq_restore(flags); | |
1419 | ||
1420 | return nr; | |
1421 | } | |
1422 | ||
1423 | /** | |
1424 | * get_user_pages_fast() - pin user pages in memory | |
1425 | * @start: starting user address | |
1426 | * @nr_pages: number of pages from start to pin | |
1427 | * @write: whether pages will be written to | |
1428 | * @pages: array that receives pointers to the pages pinned. | |
1429 | * Should be at least nr_pages long. | |
1430 | * | |
1431 | * Attempt to pin user pages in memory without taking mm->mmap_sem. | |
1432 | * If not successful, it will fall back to taking the lock and | |
1433 | * calling get_user_pages(). | |
1434 | * | |
1435 | * Returns number of pages pinned. This may be fewer than the number | |
1436 | * requested. If nr_pages is 0 or negative, returns 0. If no pages | |
1437 | * were pinned, returns -errno. | |
1438 | */ | |
1439 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
1440 | struct page **pages) | |
1441 | { | |
1442 | struct mm_struct *mm = current->mm; | |
1443 | int nr, ret; | |
1444 | ||
1445 | start &= PAGE_MASK; | |
1446 | nr = __get_user_pages_fast(start, nr_pages, write, pages); | |
1447 | ret = nr; | |
1448 | ||
1449 | if (nr < nr_pages) { | |
1450 | /* Try to get the remaining pages with get_user_pages */ | |
1451 | start += nr << PAGE_SHIFT; | |
1452 | pages += nr; | |
1453 | ||
a7b78075 AA |
1454 | ret = get_user_pages_unlocked(current, mm, start, |
1455 | nr_pages - nr, write, 0, pages); | |
2667f50e SC |
1456 | |
1457 | /* Have to be a bit careful with return values */ | |
1458 | if (nr > 0) { | |
1459 | if (ret < 0) | |
1460 | ret = nr; | |
1461 | else | |
1462 | ret += nr; | |
1463 | } | |
1464 | } | |
1465 | ||
1466 | return ret; | |
1467 | } | |
1468 | ||
1469 | #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */ |