1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_MMU_NOTIFIER_H
3#define _LINUX_MMU_NOTIFIER_H
4
5#include <linux/list.h>
6#include <linux/spinlock.h>
7#include <linux/mm_types.h>
8#include <linux/srcu.h>
9
10struct mmu_notifier;
11struct mmu_notifier_ops;
12
13#ifdef CONFIG_MMU_NOTIFIER
14
15/*
16 * The mmu notifier_mm structure is allocated and installed in
17 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
18 * critical section and it's released only when mm_count reaches zero
19 * in mmdrop().
20 */
21struct mmu_notifier_mm {
22 /* all mmu notifiers registerd in this mm are queued in this list */
23 struct hlist_head list;
24 /* to serialize the list modifications and hlist_unhashed */
25 spinlock_t lock;
26};
27
28struct mmu_notifier_range {
29 struct mm_struct *mm;
30 unsigned long start;
31 unsigned long end;
32 bool blockable;
33};
34
35struct mmu_notifier_ops {
36 /*
37 * Called either by mmu_notifier_unregister or when the mm is
38 * being destroyed by exit_mmap, always before all pages are
39 * freed. This can run concurrently with other mmu notifier
40 * methods (the ones invoked outside the mm context) and it
41 * should tear down all secondary mmu mappings and freeze the
42 * secondary mmu. If this method isn't implemented you've to
43 * be sure that nothing could possibly write to the pages
44 * through the secondary mmu by the time the last thread with
45 * tsk->mm == mm exits.
46 *
47 * As side note: the pages freed after ->release returns could
48 * be immediately reallocated by the gart at an alias physical
49 * address with a different cache model, so if ->release isn't
50 * implemented because all _software_ driven memory accesses
51 * through the secondary mmu are terminated by the time the
52 * last thread of this mm quits, you've also to be sure that
53 * speculative _hardware_ operations can't allocate dirty
54 * cachelines in the cpu that could not be snooped and made
55 * coherent with the other read and write operations happening
56 * through the gart alias address, so leading to memory
57 * corruption.
58 */
59 void (*release)(struct mmu_notifier *mn,
60 struct mm_struct *mm);
61
62 /*
63 * clear_flush_young is called after the VM is
64 * test-and-clearing the young/accessed bitflag in the
65 * pte. This way the VM will provide proper aging to the
66 * accesses to the page through the secondary MMUs and not
67 * only to the ones through the Linux pte.
68 * Start-end is necessary in case the secondary MMU is mapping the page
69 * at a smaller granularity than the primary MMU.
70 */
71 int (*clear_flush_young)(struct mmu_notifier *mn,
72 struct mm_struct *mm,
73 unsigned long start,
74 unsigned long end);
75
76 /*
77 * clear_young is a lightweight version of clear_flush_young. Like the
78 * latter, it is supposed to test-and-clear the young/accessed bitflag
79 * in the secondary pte, but it may omit flushing the secondary tlb.
80 */
81 int (*clear_young)(struct mmu_notifier *mn,
82 struct mm_struct *mm,
83 unsigned long start,
84 unsigned long end);
85
86 /*
87 * test_young is called to check the young/accessed bitflag in
88 * the secondary pte. This is used to know if the page is
89 * frequently used without actually clearing the flag or tearing
90 * down the secondary mapping on the page.
91 */
92 int (*test_young)(struct mmu_notifier *mn,
93 struct mm_struct *mm,
94 unsigned long address);
95
96 /*
97 * change_pte is called in cases that pte mapping to page is changed:
98 * for example, when ksm remaps pte to point to a new shared page.
99 */
100 void (*change_pte)(struct mmu_notifier *mn,
101 struct mm_struct *mm,
102 unsigned long address,
103 pte_t pte);
104
105 /*
106 * invalidate_range_start() and invalidate_range_end() must be
107 * paired and are called only when the mmap_sem and/or the
108 * locks protecting the reverse maps are held. If the subsystem
109 * can't guarantee that no additional references are taken to
110 * the pages in the range, it has to implement the
111 * invalidate_range() notifier to remove any references taken
112 * after invalidate_range_start().
113 *
114 * Invalidation of multiple concurrent ranges may be
115 * optionally permitted by the driver. Either way the
116 * establishment of sptes is forbidden in the range passed to
117 * invalidate_range_begin/end for the whole duration of the
118 * invalidate_range_begin/end critical section.
119 *
120 * invalidate_range_start() is called when all pages in the
121 * range are still mapped and have at least a refcount of one.
122 *
123 * invalidate_range_end() is called when all pages in the
124 * range have been unmapped and the pages have been freed by
125 * the VM.
126 *
127 * The VM will remove the page table entries and potentially
128 * the page between invalidate_range_start() and
129 * invalidate_range_end(). If the page must not be freed
130 * because of pending I/O or other circumstances then the
131 * invalidate_range_start() callback (or the initial mapping
132 * by the driver) must make sure that the refcount is kept
133 * elevated.
134 *
135 * If the driver increases the refcount when the pages are
136 * initially mapped into an address space then either
137 * invalidate_range_start() or invalidate_range_end() may
138 * decrease the refcount. If the refcount is decreased on
139 * invalidate_range_start() then the VM can free pages as page
140 * table entries are removed. If the refcount is only
141 * droppped on invalidate_range_end() then the driver itself
142 * will drop the last refcount but it must take care to flush
143 * any secondary tlb before doing the final free on the
144 * page. Pages will no longer be referenced by the linux
145 * address space but may still be referenced by sptes until
146 * the last refcount is dropped.
147 *
148 * If blockable argument is set to false then the callback cannot
149 * sleep and has to return with -EAGAIN. 0 should be returned
150 * otherwise. Please note that if invalidate_range_start approves
151 * a non-blocking behavior then the same applies to
152 * invalidate_range_end.
153 *
154 */
155 int (*invalidate_range_start)(struct mmu_notifier *mn,
156 const struct mmu_notifier_range *range);
157 void (*invalidate_range_end)(struct mmu_notifier *mn,
158 const struct mmu_notifier_range *range);
159
160 /*
161 * invalidate_range() is either called between
162 * invalidate_range_start() and invalidate_range_end() when the
163 * VM has to free pages that where unmapped, but before the
164 * pages are actually freed, or outside of _start()/_end() when
165 * a (remote) TLB is necessary.
166 *
167 * If invalidate_range() is used to manage a non-CPU TLB with
168 * shared page-tables, it not necessary to implement the
169 * invalidate_range_start()/end() notifiers, as
170 * invalidate_range() alread catches the points in time when an
171 * external TLB range needs to be flushed. For more in depth
172 * discussion on this see Documentation/vm/mmu_notifier.rst
173 *
174 * Note that this function might be called with just a sub-range
175 * of what was passed to invalidate_range_start()/end(), if
176 * called between those functions.
177 */
178 void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
179 unsigned long start, unsigned long end);
180};
181
182/*
183 * The notifier chains are protected by mmap_sem and/or the reverse map
184 * semaphores. Notifier chains are only changed when all reverse maps and
185 * the mmap_sem locks are taken.
186 *
187 * Therefore notifier chains can only be traversed when either
188 *
189 * 1. mmap_sem is held.
190 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
191 * 3. No other concurrent thread can access the list (release)
192 */
193struct mmu_notifier {
194 struct hlist_node hlist;
195 const struct mmu_notifier_ops *ops;
196};
197
198static inline int mm_has_notifiers(struct mm_struct *mm)
199{
200 return unlikely(mm->mmu_notifier_mm);
201}
202
203extern int mmu_notifier_register(struct mmu_notifier *mn,
204 struct mm_struct *mm);
205extern int __mmu_notifier_register(struct mmu_notifier *mn,
206 struct mm_struct *mm);
207extern void mmu_notifier_unregister(struct mmu_notifier *mn,
208 struct mm_struct *mm);
209extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
210 struct mm_struct *mm);
211extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
212extern void __mmu_notifier_release(struct mm_struct *mm);
213extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
214 unsigned long start,
215 unsigned long end);
216extern int __mmu_notifier_clear_young(struct mm_struct *mm,
217 unsigned long start,
218 unsigned long end);
219extern int __mmu_notifier_test_young(struct mm_struct *mm,
220 unsigned long address);
221extern void __mmu_notifier_change_pte(struct mm_struct *mm,
222 unsigned long address, pte_t pte);
223extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);
224extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r,
225 bool only_end);
226extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
227 unsigned long start, unsigned long end);
228
229static inline void mmu_notifier_release(struct mm_struct *mm)
230{
231 if (mm_has_notifiers(mm))
232 __mmu_notifier_release(mm);
233}
234
235static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
236 unsigned long start,
237 unsigned long end)
238{
239 if (mm_has_notifiers(mm))
240 return __mmu_notifier_clear_flush_young(mm, start, end);
241 return 0;
242}
243
244static inline int mmu_notifier_clear_young(struct mm_struct *mm,
245 unsigned long start,
246 unsigned long end)
247{
248 if (mm_has_notifiers(mm))
249 return __mmu_notifier_clear_young(mm, start, end);
250 return 0;
251}
252
253static inline int mmu_notifier_test_young(struct mm_struct *mm,
254 unsigned long address)
255{
256 if (mm_has_notifiers(mm))
257 return __mmu_notifier_test_young(mm, address);
258 return 0;
259}
260
261static inline void mmu_notifier_change_pte(struct mm_struct *mm,
262 unsigned long address, pte_t pte)
263{
264 if (mm_has_notifiers(mm))
265 __mmu_notifier_change_pte(mm, address, pte);
266}
267
268static inline void
269mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
270{
271 if (mm_has_notifiers(range->mm)) {
272 range->blockable = true;
273 __mmu_notifier_invalidate_range_start(range);
274 }
275}
276
277static inline int
278mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
279{
280 if (mm_has_notifiers(range->mm)) {
281 range->blockable = false;
282 return __mmu_notifier_invalidate_range_start(range);
283 }
284 return 0;
285}
286
287static inline void
288mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
289{
290 if (mm_has_notifiers(range->mm))
291 __mmu_notifier_invalidate_range_end(range, false);
292}
293
294static inline void
295mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
296{
297 if (mm_has_notifiers(range->mm))
298 __mmu_notifier_invalidate_range_end(range, true);
299}
300
301static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
302 unsigned long start, unsigned long end)
303{
304 if (mm_has_notifiers(mm))
305 __mmu_notifier_invalidate_range(mm, start, end);
306}
307
308static inline void mmu_notifier_mm_init(struct mm_struct *mm)
309{
310 mm->mmu_notifier_mm = NULL;
311}
312
313static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
314{
315 if (mm_has_notifiers(mm))
316 __mmu_notifier_mm_destroy(mm);
317}
318
319
320static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,
321 struct mm_struct *mm,
322 unsigned long start,
323 unsigned long end)
324{
325 range->mm = mm;
326 range->start = start;
327 range->end = end;
328}
329
330#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \
331({ \
332 int __young; \
333 struct vm_area_struct *___vma = __vma; \
334 unsigned long ___address = __address; \
335 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \
336 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
337 ___address, \
338 ___address + \
339 PAGE_SIZE); \
340 __young; \
341})
342
343#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \
344({ \
345 int __young; \
346 struct vm_area_struct *___vma = __vma; \
347 unsigned long ___address = __address; \
348 __young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \
349 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
350 ___address, \
351 ___address + \
352 PMD_SIZE); \
353 __young; \
354})
355
356#define ptep_clear_young_notify(__vma, __address, __ptep) \
357({ \
358 int __young; \
359 struct vm_area_struct *___vma = __vma; \
360 unsigned long ___address = __address; \
361 __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\
362 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \
363 ___address + PAGE_SIZE); \
364 __young; \
365})
366
367#define pmdp_clear_young_notify(__vma, __address, __pmdp) \
368({ \
369 int __young; \
370 struct vm_area_struct *___vma = __vma; \
371 unsigned long ___address = __address; \
372 __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\
373 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \
374 ___address + PMD_SIZE); \
375 __young; \
376})
377
378#define ptep_clear_flush_notify(__vma, __address, __ptep) \
379({ \
380 unsigned long ___addr = __address & PAGE_MASK; \
381 struct mm_struct *___mm = (__vma)->vm_mm; \
382 pte_t ___pte; \
383 \
384 ___pte = ptep_clear_flush(__vma, __address, __ptep); \
385 mmu_notifier_invalidate_range(___mm, ___addr, \
386 ___addr + PAGE_SIZE); \
387 \
388 ___pte; \
389})
390
391#define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd) \
392({ \
393 unsigned long ___haddr = __haddr & HPAGE_PMD_MASK; \
394 struct mm_struct *___mm = (__vma)->vm_mm; \
395 pmd_t ___pmd; \
396 \
397 ___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd); \
398 mmu_notifier_invalidate_range(___mm, ___haddr, \
399 ___haddr + HPAGE_PMD_SIZE); \
400 \
401 ___pmd; \
402})
403
404#define pudp_huge_clear_flush_notify(__vma, __haddr, __pud) \
405({ \
406 unsigned long ___haddr = __haddr & HPAGE_PUD_MASK; \
407 struct mm_struct *___mm = (__vma)->vm_mm; \
408 pud_t ___pud; \
409 \
410 ___pud = pudp_huge_clear_flush(__vma, __haddr, __pud); \
411 mmu_notifier_invalidate_range(___mm, ___haddr, \
412 ___haddr + HPAGE_PUD_SIZE); \
413 \
414 ___pud; \
415})
416
417/*
418 * set_pte_at_notify() sets the pte _after_ running the notifier.
419 * This is safe to start by updating the secondary MMUs, because the primary MMU
420 * pte invalidate must have already happened with a ptep_clear_flush() before
421 * set_pte_at_notify() has been invoked. Updating the secondary MMUs first is
422 * required when we change both the protection of the mapping from read-only to
423 * read-write and the pfn (like during copy on write page faults). Otherwise the
424 * old page would remain mapped readonly in the secondary MMUs after the new
425 * page is already writable by some CPU through the primary MMU.
426 */
427#define set_pte_at_notify(__mm, __address, __ptep, __pte) \
428({ \
429 struct mm_struct *___mm = __mm; \
430 unsigned long ___address = __address; \
431 pte_t ___pte = __pte; \
432 \
433 mmu_notifier_change_pte(___mm, ___address, ___pte); \
434 set_pte_at(___mm, ___address, __ptep, ___pte); \
435})
436
437extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
438 void (*func)(struct rcu_head *rcu));
439
440#else /* CONFIG_MMU_NOTIFIER */
441
442struct mmu_notifier_range {
443 unsigned long start;
444 unsigned long end;
445};
446
447static inline void _mmu_notifier_range_init(struct mmu_notifier_range *range,
448 unsigned long start,
449 unsigned long end)
450{
451 range->start = start;
452 range->end = end;
453}
454
455#define mmu_notifier_range_init(range, mm, start, end) \
456 _mmu_notifier_range_init(range, start, end)
457
458
459static inline int mm_has_notifiers(struct mm_struct *mm)
460{
461 return 0;
462}
463
464static inline void mmu_notifier_release(struct mm_struct *mm)
465{
466}
467
468static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
469 unsigned long start,
470 unsigned long end)
471{
472 return 0;
473}
474
475static inline int mmu_notifier_test_young(struct mm_struct *mm,
476 unsigned long address)
477{
478 return 0;
479}
480
481static inline void mmu_notifier_change_pte(struct mm_struct *mm,
482 unsigned long address, pte_t pte)
483{
484}
485
486static inline void
487mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
488{
489}
490
491static inline int
492mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
493{
494 return 0;
495}
496
497static inline
498void mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
499{
500}
501
502static inline void
503mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
504{
505}
506
507static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
508 unsigned long start, unsigned long end)
509{
510}
511
512static inline void mmu_notifier_mm_init(struct mm_struct *mm)
513{
514}
515
516static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
517{
518}
519
520#define ptep_clear_flush_young_notify ptep_clear_flush_young
521#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
522#define ptep_clear_young_notify ptep_test_and_clear_young
523#define pmdp_clear_young_notify pmdp_test_and_clear_young
524#define ptep_clear_flush_notify ptep_clear_flush
525#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
526#define pudp_huge_clear_flush_notify pudp_huge_clear_flush
527#define set_pte_at_notify set_pte_at
528
529#endif /* CONFIG_MMU_NOTIFIER */
530
531#endif /* _LINUX_MMU_NOTIFIER_H */
532