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/pagewalk.h>
18#include <linux/mempolicy.h>
19#include <linux/syscalls.h>
20#include <linux/sched.h>
21#include <linux/export.h>
22#include <linux/rmap.h>
23#include <linux/mmzone.h>
24#include <linux/hugetlb.h>
25#include <linux/memcontrol.h>
26#include <linux/mm_inline.h>
27#include <linux/secretmem.h>
28
29#include "internal.h"
30
31struct mlock_fbatch {
32 local_lock_t lock;
33 struct folio_batch fbatch;
34};
35
36static DEFINE_PER_CPU(struct mlock_fbatch, mlock_fbatch) = {
37 .lock = INIT_LOCAL_LOCK(lock),
38};
39
40bool can_do_mlock(void)
41{
42 if (rlimit(RLIMIT_MEMLOCK) != 0)
43 return true;
44 if (capable(CAP_IPC_LOCK))
45 return true;
46 return false;
47}
48EXPORT_SYMBOL(can_do_mlock);
49
50/*
51 * Mlocked folios are marked with the PG_mlocked flag for efficient testing
52 * in vmscan and, possibly, the fault path; and to support semi-accurate
53 * statistics.
54 *
55 * An mlocked folio [folio_test_mlocked(folio)] is unevictable. As such, it
56 * will be ostensibly placed on the LRU "unevictable" list (actually no such
57 * list exists), rather than the [in]active lists. PG_unevictable is set to
58 * indicate the unevictable state.
59 */
60
61static struct lruvec *__mlock_folio(struct folio *folio, struct lruvec *lruvec)
62{
63 /* There is nothing more we can do while it's off LRU */
64 if (!folio_test_clear_lru(folio))
65 return lruvec;
66
67 lruvec = folio_lruvec_relock_irq(folio, locked_lruvec: lruvec);
68
69 if (unlikely(folio_evictable(folio))) {
70 /*
71 * This is a little surprising, but quite possible: PG_mlocked
72 * must have got cleared already by another CPU. Could this
73 * folio be unevictable? I'm not sure, but move it now if so.
74 */
75 if (folio_test_unevictable(folio)) {
76 lruvec_del_folio(lruvec, folio);
77 folio_clear_unevictable(folio);
78 lruvec_add_folio(lruvec, folio);
79
80 __count_vm_events(item: UNEVICTABLE_PGRESCUED,
81 delta: folio_nr_pages(folio));
82 }
83 goto out;
84 }
85
86 if (folio_test_unevictable(folio)) {
87 if (folio_test_mlocked(folio))
88 folio->mlock_count++;
89 goto out;
90 }
91
92 lruvec_del_folio(lruvec, folio);
93 folio_clear_active(folio);
94 folio_set_unevictable(folio);
95 folio->mlock_count = !!folio_test_mlocked(folio);
96 lruvec_add_folio(lruvec, folio);
97 __count_vm_events(item: UNEVICTABLE_PGCULLED, delta: folio_nr_pages(folio));
98out:
99 folio_set_lru(folio);
100 return lruvec;
101}
102
103static struct lruvec *__mlock_new_folio(struct folio *folio, struct lruvec *lruvec)
104{
105 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
106
107 lruvec = folio_lruvec_relock_irq(folio, locked_lruvec: lruvec);
108
109 /* As above, this is a little surprising, but possible */
110 if (unlikely(folio_evictable(folio)))
111 goto out;
112
113 folio_set_unevictable(folio);
114 folio->mlock_count = !!folio_test_mlocked(folio);
115 __count_vm_events(item: UNEVICTABLE_PGCULLED, delta: folio_nr_pages(folio));
116out:
117 lruvec_add_folio(lruvec, folio);
118 folio_set_lru(folio);
119 return lruvec;
120}
121
122static struct lruvec *__munlock_folio(struct folio *folio, struct lruvec *lruvec)
123{
124 int nr_pages = folio_nr_pages(folio);
125 bool isolated = false;
126
127 if (!folio_test_clear_lru(folio))
128 goto munlock;
129
130 isolated = true;
131 lruvec = folio_lruvec_relock_irq(folio, locked_lruvec: lruvec);
132
133 if (folio_test_unevictable(folio)) {
134 /* Then mlock_count is maintained, but might undercount */
135 if (folio->mlock_count)
136 folio->mlock_count--;
137 if (folio->mlock_count)
138 goto out;
139 }
140 /* else assume that was the last mlock: reclaim will fix it if not */
141
142munlock:
143 if (folio_test_clear_mlocked(folio)) {
144 __zone_stat_mod_folio(folio, item: NR_MLOCK, nr: -nr_pages);
145 if (isolated || !folio_test_unevictable(folio))
146 __count_vm_events(item: UNEVICTABLE_PGMUNLOCKED, delta: nr_pages);
147 else
148 __count_vm_events(item: UNEVICTABLE_PGSTRANDED, delta: nr_pages);
149 }
150
151 /* folio_evictable() has to be checked *after* clearing Mlocked */
152 if (isolated && folio_test_unevictable(folio) && folio_evictable(folio)) {
153 lruvec_del_folio(lruvec, folio);
154 folio_clear_unevictable(folio);
155 lruvec_add_folio(lruvec, folio);
156 __count_vm_events(item: UNEVICTABLE_PGRESCUED, delta: nr_pages);
157 }
158out:
159 if (isolated)
160 folio_set_lru(folio);
161 return lruvec;
162}
163
164/*
165 * Flags held in the low bits of a struct folio pointer on the mlock_fbatch.
166 */
167#define LRU_FOLIO 0x1
168#define NEW_FOLIO 0x2
169static inline struct folio *mlock_lru(struct folio *folio)
170{
171 return (struct folio *)((unsigned long)folio + LRU_FOLIO);
172}
173
174static inline struct folio *mlock_new(struct folio *folio)
175{
176 return (struct folio *)((unsigned long)folio + NEW_FOLIO);
177}
178
179/*
180 * mlock_folio_batch() is derived from folio_batch_move_lru(): perhaps that can
181 * make use of such folio pointer flags in future, but for now just keep it for
182 * mlock. We could use three separate folio batches instead, but one feels
183 * better (munlocking a full folio batch does not need to drain mlocking folio
184 * batches first).
185 */
186static void mlock_folio_batch(struct folio_batch *fbatch)
187{
188 struct lruvec *lruvec = NULL;
189 unsigned long mlock;
190 struct folio *folio;
191 int i;
192
193 for (i = 0; i < folio_batch_count(fbatch); i++) {
194 folio = fbatch->folios[i];
195 mlock = (unsigned long)folio & (LRU_FOLIO | NEW_FOLIO);
196 folio = (struct folio *)((unsigned long)folio - mlock);
197 fbatch->folios[i] = folio;
198
199 if (mlock & LRU_FOLIO)
200 lruvec = __mlock_folio(folio, lruvec);
201 else if (mlock & NEW_FOLIO)
202 lruvec = __mlock_new_folio(folio, lruvec);
203 else
204 lruvec = __munlock_folio(folio, lruvec);
205 }
206
207 if (lruvec)
208 unlock_page_lruvec_irq(lruvec);
209 folios_put(folios: fbatch->folios, nr: folio_batch_count(fbatch));
210 folio_batch_reinit(fbatch);
211}
212
213void mlock_drain_local(void)
214{
215 struct folio_batch *fbatch;
216
217 local_lock(&mlock_fbatch.lock);
218 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
219 if (folio_batch_count(fbatch))
220 mlock_folio_batch(fbatch);
221 local_unlock(&mlock_fbatch.lock);
222}
223
224void mlock_drain_remote(int cpu)
225{
226 struct folio_batch *fbatch;
227
228 WARN_ON_ONCE(cpu_online(cpu));
229 fbatch = &per_cpu(mlock_fbatch.fbatch, cpu);
230 if (folio_batch_count(fbatch))
231 mlock_folio_batch(fbatch);
232}
233
234bool need_mlock_drain(int cpu)
235{
236 return folio_batch_count(fbatch: &per_cpu(mlock_fbatch.fbatch, cpu));
237}
238
239/**
240 * mlock_folio - mlock a folio already on (or temporarily off) LRU
241 * @folio: folio to be mlocked.
242 */
243void mlock_folio(struct folio *folio)
244{
245 struct folio_batch *fbatch;
246
247 local_lock(&mlock_fbatch.lock);
248 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
249
250 if (!folio_test_set_mlocked(folio)) {
251 int nr_pages = folio_nr_pages(folio);
252
253 zone_stat_mod_folio(folio, item: NR_MLOCK, nr: nr_pages);
254 __count_vm_events(item: UNEVICTABLE_PGMLOCKED, delta: nr_pages);
255 }
256
257 folio_get(folio);
258 if (!folio_batch_add(fbatch, folio: mlock_lru(folio)) ||
259 folio_test_large(folio) || lru_cache_disabled())
260 mlock_folio_batch(fbatch);
261 local_unlock(&mlock_fbatch.lock);
262}
263
264/**
265 * mlock_new_folio - mlock a newly allocated folio not yet on LRU
266 * @folio: folio to be mlocked, either normal or a THP head.
267 */
268void mlock_new_folio(struct folio *folio)
269{
270 struct folio_batch *fbatch;
271 int nr_pages = folio_nr_pages(folio);
272
273 local_lock(&mlock_fbatch.lock);
274 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
275 folio_set_mlocked(folio);
276
277 zone_stat_mod_folio(folio, item: NR_MLOCK, nr: nr_pages);
278 __count_vm_events(item: UNEVICTABLE_PGMLOCKED, delta: nr_pages);
279
280 folio_get(folio);
281 if (!folio_batch_add(fbatch, folio: mlock_new(folio)) ||
282 folio_test_large(folio) || lru_cache_disabled())
283 mlock_folio_batch(fbatch);
284 local_unlock(&mlock_fbatch.lock);
285}
286
287/**
288 * munlock_folio - munlock a folio
289 * @folio: folio to be munlocked, either normal or a THP head.
290 */
291void munlock_folio(struct folio *folio)
292{
293 struct folio_batch *fbatch;
294
295 local_lock(&mlock_fbatch.lock);
296 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
297 /*
298 * folio_test_clear_mlocked(folio) must be left to __munlock_folio(),
299 * which will check whether the folio is multiply mlocked.
300 */
301 folio_get(folio);
302 if (!folio_batch_add(fbatch, folio) ||
303 folio_test_large(folio) || lru_cache_disabled())
304 mlock_folio_batch(fbatch);
305 local_unlock(&mlock_fbatch.lock);
306}
307
308static inline unsigned int folio_mlock_step(struct folio *folio,
309 pte_t *pte, unsigned long addr, unsigned long end)
310{
311 unsigned int count, i, nr = folio_nr_pages(folio);
312 unsigned long pfn = folio_pfn(folio);
313 pte_t ptent = ptep_get(ptep: pte);
314
315 if (!folio_test_large(folio))
316 return 1;
317
318 count = pfn + nr - pte_pfn(pte: ptent);
319 count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
320
321 for (i = 0; i < count; i++, pte++) {
322 pte_t entry = ptep_get(ptep: pte);
323
324 if (!pte_present(a: entry))
325 break;
326 if (pte_pfn(pte: entry) - pfn >= nr)
327 break;
328 }
329
330 return i;
331}
332
333static inline bool allow_mlock_munlock(struct folio *folio,
334 struct vm_area_struct *vma, unsigned long start,
335 unsigned long end, unsigned int step)
336{
337 /*
338 * For unlock, allow munlock large folio which is partially
339 * mapped to VMA. As it's possible that large folio is
340 * mlocked and VMA is split later.
341 *
342 * During memory pressure, such kind of large folio can
343 * be split. And the pages are not in VM_LOCKed VMA
344 * can be reclaimed.
345 */
346 if (!(vma->vm_flags & VM_LOCKED))
347 return true;
348
349 /* folio_within_range() cannot take KSM, but any small folio is OK */
350 if (!folio_test_large(folio))
351 return true;
352
353 /* folio not in range [start, end), skip mlock */
354 if (!folio_within_range(folio, vma, start, end))
355 return false;
356
357 /* folio is not fully mapped, skip mlock */
358 if (step != folio_nr_pages(folio))
359 return false;
360
361 return true;
362}
363
364static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
365 unsigned long end, struct mm_walk *walk)
366
367{
368 struct vm_area_struct *vma = walk->vma;
369 spinlock_t *ptl;
370 pte_t *start_pte, *pte;
371 pte_t ptent;
372 struct folio *folio;
373 unsigned int step = 1;
374 unsigned long start = addr;
375
376 ptl = pmd_trans_huge_lock(pmd, vma);
377 if (ptl) {
378 if (!pmd_present(pmd: *pmd))
379 goto out;
380 if (is_huge_zero_pmd(pmd: *pmd))
381 goto out;
382 folio = page_folio(pmd_page(*pmd));
383 if (vma->vm_flags & VM_LOCKED)
384 mlock_folio(folio);
385 else
386 munlock_folio(folio);
387 goto out;
388 }
389
390 start_pte = pte_offset_map_lock(mm: vma->vm_mm, pmd, addr, ptlp: &ptl);
391 if (!start_pte) {
392 walk->action = ACTION_AGAIN;
393 return 0;
394 }
395
396 for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
397 ptent = ptep_get(ptep: pte);
398 if (!pte_present(a: ptent))
399 continue;
400 folio = vm_normal_folio(vma, addr, pte: ptent);
401 if (!folio || folio_is_zone_device(folio))
402 continue;
403
404 step = folio_mlock_step(folio, pte, addr, end);
405 if (!allow_mlock_munlock(folio, vma, start, end, step))
406 goto next_entry;
407
408 if (vma->vm_flags & VM_LOCKED)
409 mlock_folio(folio);
410 else
411 munlock_folio(folio);
412
413next_entry:
414 pte += step - 1;
415 addr += (step - 1) << PAGE_SHIFT;
416 }
417 pte_unmap(pte: start_pte);
418out:
419 spin_unlock(lock: ptl);
420 cond_resched();
421 return 0;
422}
423
424/*
425 * mlock_vma_pages_range() - mlock any pages already in the range,
426 * or munlock all pages in the range.
427 * @vma - vma containing range to be mlock()ed or munlock()ed
428 * @start - start address in @vma of the range
429 * @end - end of range in @vma
430 * @newflags - the new set of flags for @vma.
431 *
432 * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED;
433 * called for munlock() and munlockall(), to clear VM_LOCKED from @vma.
434 */
435static void mlock_vma_pages_range(struct vm_area_struct *vma,
436 unsigned long start, unsigned long end, vm_flags_t newflags)
437{
438 static const struct mm_walk_ops mlock_walk_ops = {
439 .pmd_entry = mlock_pte_range,
440 .walk_lock = PGWALK_WRLOCK_VERIFY,
441 };
442
443 /*
444 * There is a slight chance that concurrent page migration,
445 * or page reclaim finding a page of this now-VM_LOCKED vma,
446 * will call mlock_vma_folio() and raise page's mlock_count:
447 * double counting, leaving the page unevictable indefinitely.
448 * Communicate this danger to mlock_vma_folio() with VM_IO,
449 * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
450 * mmap_lock is held in write mode here, so this weird
451 * combination should not be visible to other mmap_lock users;
452 * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
453 */
454 if (newflags & VM_LOCKED)
455 newflags |= VM_IO;
456 vma_start_write(vma);
457 vm_flags_reset_once(vma, flags: newflags);
458
459 lru_add_drain();
460 walk_page_range(mm: vma->vm_mm, start, end, ops: &mlock_walk_ops, NULL);
461 lru_add_drain();
462
463 if (newflags & VM_IO) {
464 newflags &= ~VM_IO;
465 vm_flags_reset_once(vma, flags: newflags);
466 }
467}
468
469/*
470 * mlock_fixup - handle mlock[all]/munlock[all] requests.
471 *
472 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
473 * munlock is a no-op. However, for some special vmas, we go ahead and
474 * populate the ptes.
475 *
476 * For vmas that pass the filters, merge/split as appropriate.
477 */
478static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
479 struct vm_area_struct **prev, unsigned long start,
480 unsigned long end, vm_flags_t newflags)
481{
482 struct mm_struct *mm = vma->vm_mm;
483 int nr_pages;
484 int ret = 0;
485 vm_flags_t oldflags = vma->vm_flags;
486
487 if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
488 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
489 vma_is_dax(vma) || vma_is_secretmem(vma))
490 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
491 goto out;
492
493 vma = vma_modify_flags(vmi, prev: *prev, vma, start, end, new_flags: newflags);
494 if (IS_ERR(ptr: vma)) {
495 ret = PTR_ERR(ptr: vma);
496 goto out;
497 }
498
499 /*
500 * Keep track of amount of locked VM.
501 */
502 nr_pages = (end - start) >> PAGE_SHIFT;
503 if (!(newflags & VM_LOCKED))
504 nr_pages = -nr_pages;
505 else if (oldflags & VM_LOCKED)
506 nr_pages = 0;
507 mm->locked_vm += nr_pages;
508
509 /*
510 * vm_flags is protected by the mmap_lock held in write mode.
511 * It's okay if try_to_unmap_one unmaps a page just after we
512 * set VM_LOCKED, populate_vma_page_range will bring it back.
513 */
514 if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
515 /* No work to do, and mlocking twice would be wrong */
516 vma_start_write(vma);
517 vm_flags_reset(vma, flags: newflags);
518 } else {
519 mlock_vma_pages_range(vma, start, end, newflags);
520 }
521out:
522 *prev = vma;
523 return ret;
524}
525
526static int apply_vma_lock_flags(unsigned long start, size_t len,
527 vm_flags_t flags)
528{
529 unsigned long nstart, end, tmp;
530 struct vm_area_struct *vma, *prev;
531 VMA_ITERATOR(vmi, current->mm, start);
532
533 VM_BUG_ON(offset_in_page(start));
534 VM_BUG_ON(len != PAGE_ALIGN(len));
535 end = start + len;
536 if (end < start)
537 return -EINVAL;
538 if (end == start)
539 return 0;
540 vma = vma_iter_load(vmi: &vmi);
541 if (!vma)
542 return -ENOMEM;
543
544 prev = vma_prev(vmi: &vmi);
545 if (start > vma->vm_start)
546 prev = vma;
547
548 nstart = start;
549 tmp = vma->vm_start;
550 for_each_vma_range(vmi, vma, end) {
551 int error;
552 vm_flags_t newflags;
553
554 if (vma->vm_start != tmp)
555 return -ENOMEM;
556
557 newflags = vma->vm_flags & ~VM_LOCKED_MASK;
558 newflags |= flags;
559 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
560 tmp = vma->vm_end;
561 if (tmp > end)
562 tmp = end;
563 error = mlock_fixup(vmi: &vmi, vma, prev: &prev, start: nstart, end: tmp, newflags);
564 if (error)
565 return error;
566 tmp = vma_iter_end(vmi: &vmi);
567 nstart = tmp;
568 }
569
570 if (tmp < end)
571 return -ENOMEM;
572
573 return 0;
574}
575
576/*
577 * Go through vma areas and sum size of mlocked
578 * vma pages, as return value.
579 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
580 * is also counted.
581 * Return value: previously mlocked page counts
582 */
583static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
584 unsigned long start, size_t len)
585{
586 struct vm_area_struct *vma;
587 unsigned long count = 0;
588 unsigned long end;
589 VMA_ITERATOR(vmi, mm, start);
590
591 /* Don't overflow past ULONG_MAX */
592 if (unlikely(ULONG_MAX - len < start))
593 end = ULONG_MAX;
594 else
595 end = start + len;
596
597 for_each_vma_range(vmi, vma, end) {
598 if (vma->vm_flags & VM_LOCKED) {
599 if (start > vma->vm_start)
600 count -= (start - vma->vm_start);
601 if (end < vma->vm_end) {
602 count += end - vma->vm_start;
603 break;
604 }
605 count += vma->vm_end - vma->vm_start;
606 }
607 }
608
609 return count >> PAGE_SHIFT;
610}
611
612/*
613 * convert get_user_pages() return value to posix mlock() error
614 */
615static int __mlock_posix_error_return(long retval)
616{
617 if (retval == -EFAULT)
618 retval = -ENOMEM;
619 else if (retval == -ENOMEM)
620 retval = -EAGAIN;
621 return retval;
622}
623
624static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
625{
626 unsigned long locked;
627 unsigned long lock_limit;
628 int error = -ENOMEM;
629
630 start = untagged_addr(start);
631
632 if (!can_do_mlock())
633 return -EPERM;
634
635 len = PAGE_ALIGN(len + (offset_in_page(start)));
636 start &= PAGE_MASK;
637
638 lock_limit = rlimit(RLIMIT_MEMLOCK);
639 lock_limit >>= PAGE_SHIFT;
640 locked = len >> PAGE_SHIFT;
641
642 if (mmap_write_lock_killable(current->mm))
643 return -EINTR;
644
645 locked += current->mm->locked_vm;
646 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
647 /*
648 * It is possible that the regions requested intersect with
649 * previously mlocked areas, that part area in "mm->locked_vm"
650 * should not be counted to new mlock increment count. So check
651 * and adjust locked count if necessary.
652 */
653 locked -= count_mm_mlocked_page_nr(current->mm,
654 start, len);
655 }
656
657 /* check against resource limits */
658 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
659 error = apply_vma_lock_flags(start, len, flags);
660
661 mmap_write_unlock(current->mm);
662 if (error)
663 return error;
664
665 error = __mm_populate(addr: start, len, ignore_errors: 0);
666 if (error)
667 return __mlock_posix_error_return(retval: error);
668 return 0;
669}
670
671SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
672{
673 return do_mlock(start, len, VM_LOCKED);
674}
675
676SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
677{
678 vm_flags_t vm_flags = VM_LOCKED;
679
680 if (flags & ~MLOCK_ONFAULT)
681 return -EINVAL;
682
683 if (flags & MLOCK_ONFAULT)
684 vm_flags |= VM_LOCKONFAULT;
685
686 return do_mlock(start, len, flags: vm_flags);
687}
688
689SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
690{
691 int ret;
692
693 start = untagged_addr(start);
694
695 len = PAGE_ALIGN(len + (offset_in_page(start)));
696 start &= PAGE_MASK;
697
698 if (mmap_write_lock_killable(current->mm))
699 return -EINTR;
700 ret = apply_vma_lock_flags(start, len, flags: 0);
701 mmap_write_unlock(current->mm);
702
703 return ret;
704}
705
706/*
707 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
708 * and translate into the appropriate modifications to mm->def_flags and/or the
709 * flags for all current VMAs.
710 *
711 * There are a couple of subtleties with this. If mlockall() is called multiple
712 * times with different flags, the values do not necessarily stack. If mlockall
713 * is called once including the MCL_FUTURE flag and then a second time without
714 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
715 */
716static int apply_mlockall_flags(int flags)
717{
718 VMA_ITERATOR(vmi, current->mm, 0);
719 struct vm_area_struct *vma, *prev = NULL;
720 vm_flags_t to_add = 0;
721
722 current->mm->def_flags &= ~VM_LOCKED_MASK;
723 if (flags & MCL_FUTURE) {
724 current->mm->def_flags |= VM_LOCKED;
725
726 if (flags & MCL_ONFAULT)
727 current->mm->def_flags |= VM_LOCKONFAULT;
728
729 if (!(flags & MCL_CURRENT))
730 goto out;
731 }
732
733 if (flags & MCL_CURRENT) {
734 to_add |= VM_LOCKED;
735 if (flags & MCL_ONFAULT)
736 to_add |= VM_LOCKONFAULT;
737 }
738
739 for_each_vma(vmi, vma) {
740 vm_flags_t newflags;
741
742 newflags = vma->vm_flags & ~VM_LOCKED_MASK;
743 newflags |= to_add;
744
745 /* Ignore errors */
746 mlock_fixup(vmi: &vmi, vma, prev: &prev, start: vma->vm_start, end: vma->vm_end,
747 newflags);
748 cond_resched();
749 }
750out:
751 return 0;
752}
753
754SYSCALL_DEFINE1(mlockall, int, flags)
755{
756 unsigned long lock_limit;
757 int ret;
758
759 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
760 flags == MCL_ONFAULT)
761 return -EINVAL;
762
763 if (!can_do_mlock())
764 return -EPERM;
765
766 lock_limit = rlimit(RLIMIT_MEMLOCK);
767 lock_limit >>= PAGE_SHIFT;
768
769 if (mmap_write_lock_killable(current->mm))
770 return -EINTR;
771
772 ret = -ENOMEM;
773 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
774 capable(CAP_IPC_LOCK))
775 ret = apply_mlockall_flags(flags);
776 mmap_write_unlock(current->mm);
777 if (!ret && (flags & MCL_CURRENT))
778 mm_populate(addr: 0, TASK_SIZE);
779
780 return ret;
781}
782
783SYSCALL_DEFINE0(munlockall)
784{
785 int ret;
786
787 if (mmap_write_lock_killable(current->mm))
788 return -EINTR;
789 ret = apply_mlockall_flags(flags: 0);
790 mmap_write_unlock(current->mm);
791 return ret;
792}
793
794/*
795 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
796 * shm segments) get accounted against the user_struct instead.
797 */
798static DEFINE_SPINLOCK(shmlock_user_lock);
799
800int user_shm_lock(size_t size, struct ucounts *ucounts)
801{
802 unsigned long lock_limit, locked;
803 long memlock;
804 int allowed = 0;
805
806 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
807 lock_limit = rlimit(RLIMIT_MEMLOCK);
808 if (lock_limit != RLIM_INFINITY)
809 lock_limit >>= PAGE_SHIFT;
810 spin_lock(lock: &shmlock_user_lock);
811 memlock = inc_rlimit_ucounts(ucounts, type: UCOUNT_RLIMIT_MEMLOCK, v: locked);
812
813 if ((memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) {
814 dec_rlimit_ucounts(ucounts, type: UCOUNT_RLIMIT_MEMLOCK, v: locked);
815 goto out;
816 }
817 if (!get_ucounts(ucounts)) {
818 dec_rlimit_ucounts(ucounts, type: UCOUNT_RLIMIT_MEMLOCK, v: locked);
819 allowed = 0;
820 goto out;
821 }
822 allowed = 1;
823out:
824 spin_unlock(lock: &shmlock_user_lock);
825 return allowed;
826}
827
828void user_shm_unlock(size_t size, struct ucounts *ucounts)
829{
830 spin_lock(lock: &shmlock_user_lock);
831 dec_rlimit_ucounts(ucounts, type: UCOUNT_RLIMIT_MEMLOCK, v: (size + PAGE_SIZE - 1) >> PAGE_SHIFT);
832 spin_unlock(lock: &shmlock_user_lock);
833 put_ucounts(ucounts);
834}
835

source code of linux/mm/mlock.c