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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | /* | |
3 | * linux/mm/mlock.c | |
4 | * | |
5 | * (C) Copyright 1995 Linus Torvalds | |
6 | * (C) Copyright 2002 Christoph Hellwig | |
7 | */ | |
8 | ||
9 | #include <linux/capability.h> | |
10 | #include <linux/mman.h> | |
11 | #include <linux/mm.h> | |
12 | #include <linux/sched/user.h> | |
13 | #include <linux/swap.h> | |
14 | #include <linux/swapops.h> | |
15 | #include <linux/pagemap.h> | |
16 | #include <linux/pagevec.h> | |
17 | #include <linux/mempolicy.h> | |
18 | #include <linux/syscalls.h> | |
19 | #include <linux/sched.h> | |
20 | #include <linux/export.h> | |
21 | #include <linux/rmap.h> | |
22 | #include <linux/mmzone.h> | |
23 | #include <linux/hugetlb.h> | |
24 | #include <linux/memcontrol.h> | |
25 | #include <linux/mm_inline.h> | |
26 | ||
27 | #include "internal.h" | |
28 | ||
29 | bool can_do_mlock(void) | |
30 | { | |
31 | if (rlimit(RLIMIT_MEMLOCK) != 0) | |
32 | return true; | |
33 | if (capable(CAP_IPC_LOCK)) | |
34 | return true; | |
35 | return false; | |
36 | } | |
37 | EXPORT_SYMBOL(can_do_mlock); | |
38 | ||
39 | /* | |
40 | * Mlocked pages are marked with PageMlocked() flag for efficient testing | |
41 | * in vmscan and, possibly, the fault path; and to support semi-accurate | |
42 | * statistics. | |
43 | * | |
44 | * An mlocked page [PageMlocked(page)] is unevictable. As such, it will | |
45 | * be placed on the LRU "unevictable" list, rather than the [in]active lists. | |
46 | * The unevictable list is an LRU sibling list to the [in]active lists. | |
47 | * PageUnevictable is set to indicate the unevictable state. | |
48 | * | |
49 | * When lazy mlocking via vmscan, it is important to ensure that the | |
50 | * vma's VM_LOCKED status is not concurrently being modified, otherwise we | |
51 | * may have mlocked a page that is being munlocked. So lazy mlock must take | |
52 | * the mmap_sem for read, and verify that the vma really is locked | |
53 | * (see mm/rmap.c). | |
54 | */ | |
55 | ||
56 | /* | |
57 | * LRU accounting for clear_page_mlock() | |
58 | */ | |
59 | void clear_page_mlock(struct page *page) | |
60 | { | |
61 | if (!TestClearPageMlocked(page)) | |
62 | return; | |
63 | ||
64 | mod_zone_page_state(page_zone(page), NR_MLOCK, | |
65 | -hpage_nr_pages(page)); | |
66 | count_vm_event(UNEVICTABLE_PGCLEARED); | |
67 | /* | |
68 | * The previous TestClearPageMlocked() corresponds to the smp_mb() | |
69 | * in __pagevec_lru_add_fn(). | |
70 | * | |
71 | * See __pagevec_lru_add_fn for more explanation. | |
72 | */ | |
73 | if (!isolate_lru_page(page)) { | |
74 | putback_lru_page(page); | |
75 | } else { | |
76 | /* | |
77 | * We lost the race. the page already moved to evictable list. | |
78 | */ | |
79 | if (PageUnevictable(page)) | |
80 | count_vm_event(UNEVICTABLE_PGSTRANDED); | |
81 | } | |
82 | } | |
83 | ||
84 | /* | |
85 | * Mark page as mlocked if not already. | |
86 | * If page on LRU, isolate and putback to move to unevictable list. | |
87 | */ | |
88 | void mlock_vma_page(struct page *page) | |
89 | { | |
90 | /* Serialize with page migration */ | |
91 | BUG_ON(!PageLocked(page)); | |
92 | ||
93 | VM_BUG_ON_PAGE(PageTail(page), page); | |
94 | VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page); | |
95 | ||
96 | if (!TestSetPageMlocked(page)) { | |
97 | mod_zone_page_state(page_zone(page), NR_MLOCK, | |
98 | hpage_nr_pages(page)); | |
99 | count_vm_event(UNEVICTABLE_PGMLOCKED); | |
100 | if (!isolate_lru_page(page)) | |
101 | putback_lru_page(page); | |
102 | } | |
103 | } | |
104 | ||
105 | /* | |
106 | * Isolate a page from LRU with optional get_page() pin. | |
107 | * Assumes lru_lock already held and page already pinned. | |
108 | */ | |
109 | static bool __munlock_isolate_lru_page(struct page *page, bool getpage) | |
110 | { | |
111 | if (PageLRU(page)) { | |
112 | struct lruvec *lruvec; | |
113 | ||
114 | lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page)); | |
115 | if (getpage) | |
116 | get_page(page); | |
117 | ClearPageLRU(page); | |
118 | del_page_from_lru_list(page, lruvec, page_lru(page)); | |
119 | return true; | |
120 | } | |
121 | ||
122 | return false; | |
123 | } | |
124 | ||
125 | /* | |
126 | * Finish munlock after successful page isolation | |
127 | * | |
128 | * Page must be locked. This is a wrapper for try_to_munlock() | |
129 | * and putback_lru_page() with munlock accounting. | |
130 | */ | |
131 | static void __munlock_isolated_page(struct page *page) | |
132 | { | |
133 | /* | |
134 | * Optimization: if the page was mapped just once, that's our mapping | |
135 | * and we don't need to check all the other vmas. | |
136 | */ | |
137 | if (page_mapcount(page) > 1) | |
138 | try_to_munlock(page); | |
139 | ||
140 | /* Did try_to_unlock() succeed or punt? */ | |
141 | if (!PageMlocked(page)) | |
142 | count_vm_event(UNEVICTABLE_PGMUNLOCKED); | |
143 | ||
144 | putback_lru_page(page); | |
145 | } | |
146 | ||
147 | /* | |
148 | * Accounting for page isolation fail during munlock | |
149 | * | |
150 | * Performs accounting when page isolation fails in munlock. There is nothing | |
151 | * else to do because it means some other task has already removed the page | |
152 | * from the LRU. putback_lru_page() will take care of removing the page from | |
153 | * the unevictable list, if necessary. vmscan [page_referenced()] will move | |
154 | * the page back to the unevictable list if some other vma has it mlocked. | |
155 | */ | |
156 | static void __munlock_isolation_failed(struct page *page) | |
157 | { | |
158 | if (PageUnevictable(page)) | |
159 | __count_vm_event(UNEVICTABLE_PGSTRANDED); | |
160 | else | |
161 | __count_vm_event(UNEVICTABLE_PGMUNLOCKED); | |
162 | } | |
163 | ||
164 | /** | |
165 | * munlock_vma_page - munlock a vma page | |
166 | * @page: page to be unlocked, either a normal page or THP page head | |
167 | * | |
168 | * returns the size of the page as a page mask (0 for normal page, | |
169 | * HPAGE_PMD_NR - 1 for THP head page) | |
170 | * | |
171 | * called from munlock()/munmap() path with page supposedly on the LRU. | |
172 | * When we munlock a page, because the vma where we found the page is being | |
173 | * munlock()ed or munmap()ed, we want to check whether other vmas hold the | |
174 | * page locked so that we can leave it on the unevictable lru list and not | |
175 | * bother vmscan with it. However, to walk the page's rmap list in | |
176 | * try_to_munlock() we must isolate the page from the LRU. If some other | |
177 | * task has removed the page from the LRU, we won't be able to do that. | |
178 | * So we clear the PageMlocked as we might not get another chance. If we | |
179 | * can't isolate the page, we leave it for putback_lru_page() and vmscan | |
180 | * [page_referenced()/try_to_unmap()] to deal with. | |
181 | */ | |
182 | unsigned int munlock_vma_page(struct page *page) | |
183 | { | |
184 | int nr_pages; | |
185 | pg_data_t *pgdat = page_pgdat(page); | |
186 | ||
187 | /* For try_to_munlock() and to serialize with page migration */ | |
188 | BUG_ON(!PageLocked(page)); | |
189 | ||
190 | VM_BUG_ON_PAGE(PageTail(page), page); | |
191 | ||
192 | /* | |
193 | * Serialize with any parallel __split_huge_page_refcount() which | |
194 | * might otherwise copy PageMlocked to part of the tail pages before | |
195 | * we clear it in the head page. It also stabilizes hpage_nr_pages(). | |
196 | */ | |
197 | spin_lock_irq(&pgdat->lru_lock); | |
198 | ||
199 | if (!TestClearPageMlocked(page)) { | |
200 | /* Potentially, PTE-mapped THP: do not skip the rest PTEs */ | |
201 | nr_pages = 1; | |
202 | goto unlock_out; | |
203 | } | |
204 | ||
205 | nr_pages = hpage_nr_pages(page); | |
206 | __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); | |
207 | ||
208 | if (__munlock_isolate_lru_page(page, true)) { | |
209 | spin_unlock_irq(&pgdat->lru_lock); | |
210 | __munlock_isolated_page(page); | |
211 | goto out; | |
212 | } | |
213 | __munlock_isolation_failed(page); | |
214 | ||
215 | unlock_out: | |
216 | spin_unlock_irq(&pgdat->lru_lock); | |
217 | ||
218 | out: | |
219 | return nr_pages - 1; | |
220 | } | |
221 | ||
222 | /* | |
223 | * convert get_user_pages() return value to posix mlock() error | |
224 | */ | |
225 | static int __mlock_posix_error_return(long retval) | |
226 | { | |
227 | if (retval == -EFAULT) | |
228 | retval = -ENOMEM; | |
229 | else if (retval == -ENOMEM) | |
230 | retval = -EAGAIN; | |
231 | return retval; | |
232 | } | |
233 | ||
234 | /* | |
235 | * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec() | |
236 | * | |
237 | * The fast path is available only for evictable pages with single mapping. | |
238 | * Then we can bypass the per-cpu pvec and get better performance. | |
239 | * when mapcount > 1 we need try_to_munlock() which can fail. | |
240 | * when !page_evictable(), we need the full redo logic of putback_lru_page to | |
241 | * avoid leaving evictable page in unevictable list. | |
242 | * | |
243 | * In case of success, @page is added to @pvec and @pgrescued is incremented | |
244 | * in case that the page was previously unevictable. @page is also unlocked. | |
245 | */ | |
246 | static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec, | |
247 | int *pgrescued) | |
248 | { | |
249 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
250 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
251 | ||
252 | if (page_mapcount(page) <= 1 && page_evictable(page)) { | |
253 | pagevec_add(pvec, page); | |
254 | if (TestClearPageUnevictable(page)) | |
255 | (*pgrescued)++; | |
256 | unlock_page(page); | |
257 | return true; | |
258 | } | |
259 | ||
260 | return false; | |
261 | } | |
262 | ||
263 | /* | |
264 | * Putback multiple evictable pages to the LRU | |
265 | * | |
266 | * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of | |
267 | * the pages might have meanwhile become unevictable but that is OK. | |
268 | */ | |
269 | static void __putback_lru_fast(struct pagevec *pvec, int pgrescued) | |
270 | { | |
271 | count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec)); | |
272 | /* | |
273 | *__pagevec_lru_add() calls release_pages() so we don't call | |
274 | * put_page() explicitly | |
275 | */ | |
276 | __pagevec_lru_add(pvec); | |
277 | count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); | |
278 | } | |
279 | ||
280 | /* | |
281 | * Munlock a batch of pages from the same zone | |
282 | * | |
283 | * The work is split to two main phases. First phase clears the Mlocked flag | |
284 | * and attempts to isolate the pages, all under a single zone lru lock. | |
285 | * The second phase finishes the munlock only for pages where isolation | |
286 | * succeeded. | |
287 | * | |
288 | * Note that the pagevec may be modified during the process. | |
289 | */ | |
290 | static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) | |
291 | { | |
292 | int i; | |
293 | int nr = pagevec_count(pvec); | |
294 | int delta_munlocked = -nr; | |
295 | struct pagevec pvec_putback; | |
296 | int pgrescued = 0; | |
297 | ||
298 | pagevec_init(&pvec_putback); | |
299 | ||
300 | /* Phase 1: page isolation */ | |
301 | spin_lock_irq(&zone->zone_pgdat->lru_lock); | |
302 | for (i = 0; i < nr; i++) { | |
303 | struct page *page = pvec->pages[i]; | |
304 | ||
305 | if (TestClearPageMlocked(page)) { | |
306 | /* | |
307 | * We already have pin from follow_page_mask() | |
308 | * so we can spare the get_page() here. | |
309 | */ | |
310 | if (__munlock_isolate_lru_page(page, false)) | |
311 | continue; | |
312 | else | |
313 | __munlock_isolation_failed(page); | |
314 | } else { | |
315 | delta_munlocked++; | |
316 | } | |
317 | ||
318 | /* | |
319 | * We won't be munlocking this page in the next phase | |
320 | * but we still need to release the follow_page_mask() | |
321 | * pin. We cannot do it under lru_lock however. If it's | |
322 | * the last pin, __page_cache_release() would deadlock. | |
323 | */ | |
324 | pagevec_add(&pvec_putback, pvec->pages[i]); | |
325 | pvec->pages[i] = NULL; | |
326 | } | |
327 | __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); | |
328 | spin_unlock_irq(&zone->zone_pgdat->lru_lock); | |
329 | ||
330 | /* Now we can release pins of pages that we are not munlocking */ | |
331 | pagevec_release(&pvec_putback); | |
332 | ||
333 | /* Phase 2: page munlock */ | |
334 | for (i = 0; i < nr; i++) { | |
335 | struct page *page = pvec->pages[i]; | |
336 | ||
337 | if (page) { | |
338 | lock_page(page); | |
339 | if (!__putback_lru_fast_prepare(page, &pvec_putback, | |
340 | &pgrescued)) { | |
341 | /* | |
342 | * Slow path. We don't want to lose the last | |
343 | * pin before unlock_page() | |
344 | */ | |
345 | get_page(page); /* for putback_lru_page() */ | |
346 | __munlock_isolated_page(page); | |
347 | unlock_page(page); | |
348 | put_page(page); /* from follow_page_mask() */ | |
349 | } | |
350 | } | |
351 | } | |
352 | ||
353 | /* | |
354 | * Phase 3: page putback for pages that qualified for the fast path | |
355 | * This will also call put_page() to return pin from follow_page_mask() | |
356 | */ | |
357 | if (pagevec_count(&pvec_putback)) | |
358 | __putback_lru_fast(&pvec_putback, pgrescued); | |
359 | } | |
360 | ||
361 | /* | |
362 | * Fill up pagevec for __munlock_pagevec using pte walk | |
363 | * | |
364 | * The function expects that the struct page corresponding to @start address is | |
365 | * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone. | |
366 | * | |
367 | * The rest of @pvec is filled by subsequent pages within the same pmd and same | |
368 | * zone, as long as the pte's are present and vm_normal_page() succeeds. These | |
369 | * pages also get pinned. | |
370 | * | |
371 | * Returns the address of the next page that should be scanned. This equals | |
372 | * @start + PAGE_SIZE when no page could be added by the pte walk. | |
373 | */ | |
374 | static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, | |
375 | struct vm_area_struct *vma, struct zone *zone, | |
376 | unsigned long start, unsigned long end) | |
377 | { | |
378 | pte_t *pte; | |
379 | spinlock_t *ptl; | |
380 | ||
381 | /* | |
382 | * Initialize pte walk starting at the already pinned page where we | |
383 | * are sure that there is a pte, as it was pinned under the same | |
384 | * mmap_sem write op. | |
385 | */ | |
386 | pte = get_locked_pte(vma->vm_mm, start, &ptl); | |
387 | /* Make sure we do not cross the page table boundary */ | |
388 | end = pgd_addr_end(start, end); | |
389 | end = p4d_addr_end(start, end); | |
390 | end = pud_addr_end(start, end); | |
391 | end = pmd_addr_end(start, end); | |
392 | ||
393 | /* The page next to the pinned page is the first we will try to get */ | |
394 | start += PAGE_SIZE; | |
395 | while (start < end) { | |
396 | struct page *page = NULL; | |
397 | pte++; | |
398 | if (pte_present(*pte)) | |
399 | page = vm_normal_page(vma, start, *pte); | |
400 | /* | |
401 | * Break if page could not be obtained or the page's node+zone does not | |
402 | * match | |
403 | */ | |
404 | if (!page || page_zone(page) != zone) | |
405 | break; | |
406 | ||
407 | /* | |
408 | * Do not use pagevec for PTE-mapped THP, | |
409 | * munlock_vma_pages_range() will handle them. | |
410 | */ | |
411 | if (PageTransCompound(page)) | |
412 | break; | |
413 | ||
414 | get_page(page); | |
415 | /* | |
416 | * Increase the address that will be returned *before* the | |
417 | * eventual break due to pvec becoming full by adding the page | |
418 | */ | |
419 | start += PAGE_SIZE; | |
420 | if (pagevec_add(pvec, page) == 0) | |
421 | break; | |
422 | } | |
423 | pte_unmap_unlock(pte, ptl); | |
424 | return start; | |
425 | } | |
426 | ||
427 | /* | |
428 | * munlock_vma_pages_range() - munlock all pages in the vma range.' | |
429 | * @vma - vma containing range to be munlock()ed. | |
430 | * @start - start address in @vma of the range | |
431 | * @end - end of range in @vma. | |
432 | * | |
433 | * For mremap(), munmap() and exit(). | |
434 | * | |
435 | * Called with @vma VM_LOCKED. | |
436 | * | |
437 | * Returns with VM_LOCKED cleared. Callers must be prepared to | |
438 | * deal with this. | |
439 | * | |
440 | * We don't save and restore VM_LOCKED here because pages are | |
441 | * still on lru. In unmap path, pages might be scanned by reclaim | |
442 | * and re-mlocked by try_to_{munlock|unmap} before we unmap and | |
443 | * free them. This will result in freeing mlocked pages. | |
444 | */ | |
445 | void munlock_vma_pages_range(struct vm_area_struct *vma, | |
446 | unsigned long start, unsigned long end) | |
447 | { | |
448 | vma->vm_flags &= VM_LOCKED_CLEAR_MASK; | |
449 | ||
450 | while (start < end) { | |
451 | struct page *page; | |
452 | unsigned int page_mask = 0; | |
453 | unsigned long page_increm; | |
454 | struct pagevec pvec; | |
455 | struct zone *zone; | |
456 | ||
457 | pagevec_init(&pvec); | |
458 | /* | |
459 | * Although FOLL_DUMP is intended for get_dump_page(), | |
460 | * it just so happens that its special treatment of the | |
461 | * ZERO_PAGE (returning an error instead of doing get_page) | |
462 | * suits munlock very well (and if somehow an abnormal page | |
463 | * has sneaked into the range, we won't oops here: great). | |
464 | */ | |
465 | page = follow_page(vma, start, FOLL_GET | FOLL_DUMP); | |
466 | ||
467 | if (page && !IS_ERR(page)) { | |
468 | if (PageTransTail(page)) { | |
469 | VM_BUG_ON_PAGE(PageMlocked(page), page); | |
470 | put_page(page); /* follow_page_mask() */ | |
471 | } else if (PageTransHuge(page)) { | |
472 | lock_page(page); | |
473 | /* | |
474 | * Any THP page found by follow_page_mask() may | |
475 | * have gotten split before reaching | |
476 | * munlock_vma_page(), so we need to compute | |
477 | * the page_mask here instead. | |
478 | */ | |
479 | page_mask = munlock_vma_page(page); | |
480 | unlock_page(page); | |
481 | put_page(page); /* follow_page_mask() */ | |
482 | } else { | |
483 | /* | |
484 | * Non-huge pages are handled in batches via | |
485 | * pagevec. The pin from follow_page_mask() | |
486 | * prevents them from collapsing by THP. | |
487 | */ | |
488 | pagevec_add(&pvec, page); | |
489 | zone = page_zone(page); | |
490 | ||
491 | /* | |
492 | * Try to fill the rest of pagevec using fast | |
493 | * pte walk. This will also update start to | |
494 | * the next page to process. Then munlock the | |
495 | * pagevec. | |
496 | */ | |
497 | start = __munlock_pagevec_fill(&pvec, vma, | |
498 | zone, start, end); | |
499 | __munlock_pagevec(&pvec, zone); | |
500 | goto next; | |
501 | } | |
502 | } | |
503 | page_increm = 1 + page_mask; | |
504 | start += page_increm * PAGE_SIZE; | |
505 | next: | |
506 | cond_resched(); | |
507 | } | |
508 | } | |
509 | ||
510 | /* | |
511 | * mlock_fixup - handle mlock[all]/munlock[all] requests. | |
512 | * | |
513 | * Filters out "special" vmas -- VM_LOCKED never gets set for these, and | |
514 | * munlock is a no-op. However, for some special vmas, we go ahead and | |
515 | * populate the ptes. | |
516 | * | |
517 | * For vmas that pass the filters, merge/split as appropriate. | |
518 | */ | |
519 | static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev, | |
520 | unsigned long start, unsigned long end, vm_flags_t newflags) | |
521 | { | |
522 | struct mm_struct *mm = vma->vm_mm; | |
523 | pgoff_t pgoff; | |
524 | int nr_pages; | |
525 | int ret = 0; | |
526 | int lock = !!(newflags & VM_LOCKED); | |
527 | vm_flags_t old_flags = vma->vm_flags; | |
528 | ||
529 | if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) || | |
530 | is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) || | |
531 | vma_is_dax(vma)) | |
532 | /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */ | |
533 | goto out; | |
534 | ||
535 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
536 | *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma, | |
537 | vma->vm_file, pgoff, vma_policy(vma), | |
538 | vma->vm_userfaultfd_ctx); | |
539 | if (*prev) { | |
540 | vma = *prev; | |
541 | goto success; | |
542 | } | |
543 | ||
544 | if (start != vma->vm_start) { | |
545 | ret = split_vma(mm, vma, start, 1); | |
546 | if (ret) | |
547 | goto out; | |
548 | } | |
549 | ||
550 | if (end != vma->vm_end) { | |
551 | ret = split_vma(mm, vma, end, 0); | |
552 | if (ret) | |
553 | goto out; | |
554 | } | |
555 | ||
556 | success: | |
557 | /* | |
558 | * Keep track of amount of locked VM. | |
559 | */ | |
560 | nr_pages = (end - start) >> PAGE_SHIFT; | |
561 | if (!lock) | |
562 | nr_pages = -nr_pages; | |
563 | else if (old_flags & VM_LOCKED) | |
564 | nr_pages = 0; | |
565 | mm->locked_vm += nr_pages; | |
566 | ||
567 | /* | |
568 | * vm_flags is protected by the mmap_sem held in write mode. | |
569 | * It's okay if try_to_unmap_one unmaps a page just after we | |
570 | * set VM_LOCKED, populate_vma_page_range will bring it back. | |
571 | */ | |
572 | ||
573 | if (lock) | |
574 | vma->vm_flags = newflags; | |
575 | else | |
576 | munlock_vma_pages_range(vma, start, end); | |
577 | ||
578 | out: | |
579 | *prev = vma; | |
580 | return ret; | |
581 | } | |
582 | ||
583 | static int apply_vma_lock_flags(unsigned long start, size_t len, | |
584 | vm_flags_t flags) | |
585 | { | |
586 | unsigned long nstart, end, tmp; | |
587 | struct vm_area_struct * vma, * prev; | |
588 | int error; | |
589 | ||
590 | VM_BUG_ON(offset_in_page(start)); | |
591 | VM_BUG_ON(len != PAGE_ALIGN(len)); | |
592 | end = start + len; | |
593 | if (end < start) | |
594 | return -EINVAL; | |
595 | if (end == start) | |
596 | return 0; | |
597 | vma = find_vma(current->mm, start); | |
598 | if (!vma || vma->vm_start > start) | |
599 | return -ENOMEM; | |
600 | ||
601 | prev = vma->vm_prev; | |
602 | if (start > vma->vm_start) | |
603 | prev = vma; | |
604 | ||
605 | for (nstart = start ; ; ) { | |
606 | vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK; | |
607 | ||
608 | newflags |= flags; | |
609 | ||
610 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ | |
611 | tmp = vma->vm_end; | |
612 | if (tmp > end) | |
613 | tmp = end; | |
614 | error = mlock_fixup(vma, &prev, nstart, tmp, newflags); | |
615 | if (error) | |
616 | break; | |
617 | nstart = tmp; | |
618 | if (nstart < prev->vm_end) | |
619 | nstart = prev->vm_end; | |
620 | if (nstart >= end) | |
621 | break; | |
622 | ||
623 | vma = prev->vm_next; | |
624 | if (!vma || vma->vm_start != nstart) { | |
625 | error = -ENOMEM; | |
626 | break; | |
627 | } | |
628 | } | |
629 | return error; | |
630 | } | |
631 | ||
632 | /* | |
633 | * Go through vma areas and sum size of mlocked | |
634 | * vma pages, as return value. | |
635 | * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT) | |
636 | * is also counted. | |
637 | * Return value: previously mlocked page counts | |
638 | */ | |
639 | static int count_mm_mlocked_page_nr(struct mm_struct *mm, | |
640 | unsigned long start, size_t len) | |
641 | { | |
642 | struct vm_area_struct *vma; | |
643 | int count = 0; | |
644 | ||
645 | if (mm == NULL) | |
646 | mm = current->mm; | |
647 | ||
648 | vma = find_vma(mm, start); | |
649 | if (vma == NULL) | |
650 | vma = mm->mmap; | |
651 | ||
652 | for (; vma ; vma = vma->vm_next) { | |
653 | if (start >= vma->vm_end) | |
654 | continue; | |
655 | if (start + len <= vma->vm_start) | |
656 | break; | |
657 | if (vma->vm_flags & VM_LOCKED) { | |
658 | if (start > vma->vm_start) | |
659 | count -= (start - vma->vm_start); | |
660 | if (start + len < vma->vm_end) { | |
661 | count += start + len - vma->vm_start; | |
662 | break; | |
663 | } | |
664 | count += vma->vm_end - vma->vm_start; | |
665 | } | |
666 | } | |
667 | ||
668 | return count >> PAGE_SHIFT; | |
669 | } | |
670 | ||
671 | static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags) | |
672 | { | |
673 | unsigned long locked; | |
674 | unsigned long lock_limit; | |
675 | int error = -ENOMEM; | |
676 | ||
677 | if (!can_do_mlock()) | |
678 | return -EPERM; | |
679 | ||
680 | len = PAGE_ALIGN(len + (offset_in_page(start))); | |
681 | start &= PAGE_MASK; | |
682 | ||
683 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
684 | lock_limit >>= PAGE_SHIFT; | |
685 | locked = len >> PAGE_SHIFT; | |
686 | ||
687 | if (down_write_killable(¤t->mm->mmap_sem)) | |
688 | return -EINTR; | |
689 | ||
690 | locked += current->mm->locked_vm; | |
691 | if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) { | |
692 | /* | |
693 | * It is possible that the regions requested intersect with | |
694 | * previously mlocked areas, that part area in "mm->locked_vm" | |
695 | * should not be counted to new mlock increment count. So check | |
696 | * and adjust locked count if necessary. | |
697 | */ | |
698 | locked -= count_mm_mlocked_page_nr(current->mm, | |
699 | start, len); | |
700 | } | |
701 | ||
702 | /* check against resource limits */ | |
703 | if ((locked <= lock_limit) || capable(CAP_IPC_LOCK)) | |
704 | error = apply_vma_lock_flags(start, len, flags); | |
705 | ||
706 | up_write(¤t->mm->mmap_sem); | |
707 | if (error) | |
708 | return error; | |
709 | ||
710 | error = __mm_populate(start, len, 0); | |
711 | if (error) | |
712 | return __mlock_posix_error_return(error); | |
713 | return 0; | |
714 | } | |
715 | ||
716 | SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len) | |
717 | { | |
718 | return do_mlock(start, len, VM_LOCKED); | |
719 | } | |
720 | ||
721 | SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags) | |
722 | { | |
723 | vm_flags_t vm_flags = VM_LOCKED; | |
724 | ||
725 | if (flags & ~MLOCK_ONFAULT) | |
726 | return -EINVAL; | |
727 | ||
728 | if (flags & MLOCK_ONFAULT) | |
729 | vm_flags |= VM_LOCKONFAULT; | |
730 | ||
731 | return do_mlock(start, len, vm_flags); | |
732 | } | |
733 | ||
734 | SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) | |
735 | { | |
736 | int ret; | |
737 | ||
738 | len = PAGE_ALIGN(len + (offset_in_page(start))); | |
739 | start &= PAGE_MASK; | |
740 | ||
741 | if (down_write_killable(¤t->mm->mmap_sem)) | |
742 | return -EINTR; | |
743 | ret = apply_vma_lock_flags(start, len, 0); | |
744 | up_write(¤t->mm->mmap_sem); | |
745 | ||
746 | return ret; | |
747 | } | |
748 | ||
749 | /* | |
750 | * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall) | |
751 | * and translate into the appropriate modifications to mm->def_flags and/or the | |
752 | * flags for all current VMAs. | |
753 | * | |
754 | * There are a couple of subtleties with this. If mlockall() is called multiple | |
755 | * times with different flags, the values do not necessarily stack. If mlockall | |
756 | * is called once including the MCL_FUTURE flag and then a second time without | |
757 | * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags. | |
758 | */ | |
759 | static int apply_mlockall_flags(int flags) | |
760 | { | |
761 | struct vm_area_struct * vma, * prev = NULL; | |
762 | vm_flags_t to_add = 0; | |
763 | ||
764 | current->mm->def_flags &= VM_LOCKED_CLEAR_MASK; | |
765 | if (flags & MCL_FUTURE) { | |
766 | current->mm->def_flags |= VM_LOCKED; | |
767 | ||
768 | if (flags & MCL_ONFAULT) | |
769 | current->mm->def_flags |= VM_LOCKONFAULT; | |
770 | ||
771 | if (!(flags & MCL_CURRENT)) | |
772 | goto out; | |
773 | } | |
774 | ||
775 | if (flags & MCL_CURRENT) { | |
776 | to_add |= VM_LOCKED; | |
777 | if (flags & MCL_ONFAULT) | |
778 | to_add |= VM_LOCKONFAULT; | |
779 | } | |
780 | ||
781 | for (vma = current->mm->mmap; vma ; vma = prev->vm_next) { | |
782 | vm_flags_t newflags; | |
783 | ||
784 | newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK; | |
785 | newflags |= to_add; | |
786 | ||
787 | /* Ignore errors */ | |
788 | mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags); | |
789 | cond_resched(); | |
790 | } | |
791 | out: | |
792 | return 0; | |
793 | } | |
794 | ||
795 | SYSCALL_DEFINE1(mlockall, int, flags) | |
796 | { | |
797 | unsigned long lock_limit; | |
798 | int ret; | |
799 | ||
800 | if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT))) | |
801 | return -EINVAL; | |
802 | ||
803 | if (!can_do_mlock()) | |
804 | return -EPERM; | |
805 | ||
806 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
807 | lock_limit >>= PAGE_SHIFT; | |
808 | ||
809 | if (down_write_killable(¤t->mm->mmap_sem)) | |
810 | return -EINTR; | |
811 | ||
812 | ret = -ENOMEM; | |
813 | if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) || | |
814 | capable(CAP_IPC_LOCK)) | |
815 | ret = apply_mlockall_flags(flags); | |
816 | up_write(¤t->mm->mmap_sem); | |
817 | if (!ret && (flags & MCL_CURRENT)) | |
818 | mm_populate(0, TASK_SIZE); | |
819 | ||
820 | return ret; | |
821 | } | |
822 | ||
823 | SYSCALL_DEFINE0(munlockall) | |
824 | { | |
825 | int ret; | |
826 | ||
827 | if (down_write_killable(¤t->mm->mmap_sem)) | |
828 | return -EINTR; | |
829 | ret = apply_mlockall_flags(0); | |
830 | up_write(¤t->mm->mmap_sem); | |
831 | return ret; | |
832 | } | |
833 | ||
834 | /* | |
835 | * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB | |
836 | * shm segments) get accounted against the user_struct instead. | |
837 | */ | |
838 | static DEFINE_SPINLOCK(shmlock_user_lock); | |
839 | ||
840 | int user_shm_lock(size_t size, struct user_struct *user) | |
841 | { | |
842 | unsigned long lock_limit, locked; | |
843 | int allowed = 0; | |
844 | ||
845 | locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
846 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
847 | if (lock_limit == RLIM_INFINITY) | |
848 | allowed = 1; | |
849 | lock_limit >>= PAGE_SHIFT; | |
850 | spin_lock(&shmlock_user_lock); | |
851 | if (!allowed && | |
852 | locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK)) | |
853 | goto out; | |
854 | get_uid(user); | |
855 | user->locked_shm += locked; | |
856 | allowed = 1; | |
857 | out: | |
858 | spin_unlock(&shmlock_user_lock); | |
859 | return allowed; | |
860 | } | |
861 | ||
862 | void user_shm_unlock(size_t size, struct user_struct *user) | |
863 | { | |
864 | spin_lock(&shmlock_user_lock); | |
865 | user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
866 | spin_unlock(&shmlock_user_lock); | |
867 | free_uid(user); | |
868 | } |