1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_MMU_NOTIFIER_H
3 #define _LINUX_MMU_NOTIFIER_H
4
5 #include <linux/types.h>
6 #include <linux/list.h>
7 #include <linux/spinlock.h>
8 #include <linux/mm_types.h>
9 #include <linux/srcu.h>
10
11 struct mmu_notifier;
12 struct mmu_notifier_ops;
13
14 /* mmu_notifier_ops flags */
15 #define MMU_INVALIDATE_DOES_NOT_BLOCK (0x01)
16
17 #ifdef CONFIG_MMU_NOTIFIER
18
19 /*
20 * The mmu notifier_mm structure is allocated and installed in
21 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
22 * critical section and it's released only when mm_count reaches zero
23 * in mmdrop().
24 */
25 struct mmu_notifier_mm {
26 /* all mmu notifiers registerd in this mm are queued in this list */
27 struct hlist_head list;
28 /* to serialize the list modifications and hlist_unhashed */
29 spinlock_t lock;
30 };
31
32 struct mmu_notifier_ops {
33 /*
34 * Flags to specify behavior of callbacks for this MMU notifier.
35 * Used to determine which context an operation may be called.
36 *
37 * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_range_* callbacks do not
38 * block
39 */
40 int flags;
41
42 /*
43 * Called either by mmu_notifier_unregister or when the mm is
44 * being destroyed by exit_mmap, always before all pages are
45 * freed. This can run concurrently with other mmu notifier
46 * methods (the ones invoked outside the mm context) and it
47 * should tear down all secondary mmu mappings and freeze the
48 * secondary mmu. If this method isn't implemented you've to
49 * be sure that nothing could possibly write to the pages
50 * through the secondary mmu by the time the last thread with
51 * tsk->mm == mm exits.
52 *
53 * As side note: the pages freed after ->release returns could
54 * be immediately reallocated by the gart at an alias physical
55 * address with a different cache model, so if ->release isn't
56 * implemented because all _software_ driven memory accesses
57 * through the secondary mmu are terminated by the time the
58 * last thread of this mm quits, you've also to be sure that
59 * speculative _hardware_ operations can't allocate dirty
60 * cachelines in the cpu that could not be snooped and made
61 * coherent with the other read and write operations happening
62 * through the gart alias address, so leading to memory
63 * corruption.
64 */
65 void (*release)(struct mmu_notifier *mn,
66 struct mm_struct *mm);
67
68 /*
69 * clear_flush_young is called after the VM is
70 * test-and-clearing the young/accessed bitflag in the
71 * pte. This way the VM will provide proper aging to the
72 * accesses to the page through the secondary MMUs and not
73 * only to the ones through the Linux pte.
74 * Start-end is necessary in case the secondary MMU is mapping the page
75 * at a smaller granularity than the primary MMU.
76 */
77 int (*clear_flush_young)(struct mmu_notifier *mn,
78 struct mm_struct *mm,
79 unsigned long start,
80 unsigned long end);
81
82 /*
83 * clear_young is a lightweight version of clear_flush_young. Like the
84 * latter, it is supposed to test-and-clear the young/accessed bitflag
85 * in the secondary pte, but it may omit flushing the secondary tlb.
86 */
87 int (*clear_young)(struct mmu_notifier *mn,
88 struct mm_struct *mm,
89 unsigned long start,
90 unsigned long end);
91
92 /*
93 * test_young is called to check the young/accessed bitflag in
94 * the secondary pte. This is used to know if the page is
95 * frequently used without actually clearing the flag or tearing
96 * down the secondary mapping on the page.
97 */
98 int (*test_young)(struct mmu_notifier *mn,
99 struct mm_struct *mm,
100 unsigned long address);
101
102 /*
103 * change_pte is called in cases that pte mapping to page is changed:
104 * for example, when ksm remaps pte to point to a new shared page.
105 */
106 void (*change_pte)(struct mmu_notifier *mn,
107 struct mm_struct *mm,
108 unsigned long address,
109 pte_t pte);
110
111 /*
112 * invalidate_range_start() and invalidate_range_end() must be
113 * paired and are called only when the mmap_sem and/or the
114 * locks protecting the reverse maps are held. If the subsystem
115 * can't guarantee that no additional references are taken to
116 * the pages in the range, it has to implement the
117 * invalidate_range() notifier to remove any references taken
118 * after invalidate_range_start().
119 *
120 * Invalidation of multiple concurrent ranges may be
121 * optionally permitted by the driver. Either way the
122 * establishment of sptes is forbidden in the range passed to
123 * invalidate_range_begin/end for the whole duration of the
124 * invalidate_range_begin/end critical section.
125 *
126 * invalidate_range_start() is called when all pages in the
127 * range are still mapped and have at least a refcount of one.
128 *
129 * invalidate_range_end() is called when all pages in the
130 * range have been unmapped and the pages have been freed by
131 * the VM.
132 *
133 * The VM will remove the page table entries and potentially
134 * the page between invalidate_range_start() and
135 * invalidate_range_end(). If the page must not be freed
136 * because of pending I/O or other circumstances then the
137 * invalidate_range_start() callback (or the initial mapping
138 * by the driver) must make sure that the refcount is kept
139 * elevated.
140 *
141 * If the driver increases the refcount when the pages are
142 * initially mapped into an address space then either
143 * invalidate_range_start() or invalidate_range_end() may
144 * decrease the refcount. If the refcount is decreased on
145 * invalidate_range_start() then the VM can free pages as page
146 * table entries are removed. If the refcount is only
147 * droppped on invalidate_range_end() then the driver itself
148 * will drop the last refcount but it must take care to flush
149 * any secondary tlb before doing the final free on the
150 * page. Pages will no longer be referenced by the linux
151 * address space but may still be referenced by sptes until
152 * the last refcount is dropped.
153 *
154 * If blockable argument is set to false then the callback cannot
155 * sleep and has to return with -EAGAIN. 0 should be returned
156 * otherwise.
157 *
158 */
159 int (*invalidate_range_start)(struct mmu_notifier *mn,
160 struct mm_struct *mm,
161 unsigned long start, unsigned long end,
162 bool blockable);
163 void (*invalidate_range_end)(struct mmu_notifier *mn,
164 struct mm_struct *mm,
165 unsigned long start, unsigned long end);
166
167 /*
168 * invalidate_range() is either called between
169 * invalidate_range_start() and invalidate_range_end() when the
170 * VM has to free pages that where unmapped, but before the
171 * pages are actually freed, or outside of _start()/_end() when
172 * a (remote) TLB is necessary.
173 *
174 * If invalidate_range() is used to manage a non-CPU TLB with
175 * shared page-tables, it not necessary to implement the
176 * invalidate_range_start()/end() notifiers, as
177 * invalidate_range() alread catches the points in time when an
178 * external TLB range needs to be flushed. For more in depth
179 * discussion on this see Documentation/vm/mmu_notifier.rst
180 *
181 * Note that this function might be called with just a sub-range
182 * of what was passed to invalidate_range_start()/end(), if
183 * called between those functions.
184 *
185 * If this callback cannot block, and invalidate_range_{start,end}
186 * cannot block, mmu_notifier_ops.flags should have
187 * MMU_INVALIDATE_DOES_NOT_BLOCK set.
188 */
189 void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
190 unsigned long start, unsigned long end);
191 };
192
193 /*
194 * The notifier chains are protected by mmap_sem and/or the reverse map
195 * semaphores. Notifier chains are only changed when all reverse maps and
196 * the mmap_sem locks are taken.
197 *
198 * Therefore notifier chains can only be traversed when either
199 *
200 * 1. mmap_sem is held.
201 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
202 * 3. No other concurrent thread can access the list (release)
203 */
204 struct mmu_notifier {
205 struct hlist_node hlist;
206 const struct mmu_notifier_ops *ops;
207 };
208
mm_has_notifiers(struct mm_struct * mm)209 static inline int mm_has_notifiers(struct mm_struct *mm)
210 {
211 return unlikely(mm->mmu_notifier_mm);
212 }
213
214 extern int mmu_notifier_register(struct mmu_notifier *mn,
215 struct mm_struct *mm);
216 extern int __mmu_notifier_register(struct mmu_notifier *mn,
217 struct mm_struct *mm);
218 extern void mmu_notifier_unregister(struct mmu_notifier *mn,
219 struct mm_struct *mm);
220 extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
221 struct mm_struct *mm);
222 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
223 extern void __mmu_notifier_release(struct mm_struct *mm);
224 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
225 unsigned long start,
226 unsigned long end);
227 extern int __mmu_notifier_clear_young(struct mm_struct *mm,
228 unsigned long start,
229 unsigned long end);
230 extern int __mmu_notifier_test_young(struct mm_struct *mm,
231 unsigned long address);
232 extern void __mmu_notifier_change_pte(struct mm_struct *mm,
233 unsigned long address, pte_t pte);
234 extern int __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
235 unsigned long start, unsigned long end,
236 bool blockable);
237 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
238 unsigned long start, unsigned long end,
239 bool only_end);
240 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
241 unsigned long start, unsigned long end);
242 extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm);
243
mmu_notifier_release(struct mm_struct * mm)244 static inline void mmu_notifier_release(struct mm_struct *mm)
245 {
246 if (mm_has_notifiers(mm))
247 __mmu_notifier_release(mm);
248 }
249
mmu_notifier_clear_flush_young(struct mm_struct * mm,unsigned long start,unsigned long end)250 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
251 unsigned long start,
252 unsigned long end)
253 {
254 if (mm_has_notifiers(mm))
255 return __mmu_notifier_clear_flush_young(mm, start, end);
256 return 0;
257 }
258
mmu_notifier_clear_young(struct mm_struct * mm,unsigned long start,unsigned long end)259 static inline int mmu_notifier_clear_young(struct mm_struct *mm,
260 unsigned long start,
261 unsigned long end)
262 {
263 if (mm_has_notifiers(mm))
264 return __mmu_notifier_clear_young(mm, start, end);
265 return 0;
266 }
267
mmu_notifier_test_young(struct mm_struct * mm,unsigned long address)268 static inline int mmu_notifier_test_young(struct mm_struct *mm,
269 unsigned long address)
270 {
271 if (mm_has_notifiers(mm))
272 return __mmu_notifier_test_young(mm, address);
273 return 0;
274 }
275
mmu_notifier_change_pte(struct mm_struct * mm,unsigned long address,pte_t pte)276 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
277 unsigned long address, pte_t pte)
278 {
279 if (mm_has_notifiers(mm))
280 __mmu_notifier_change_pte(mm, address, pte);
281 }
282
mmu_notifier_invalidate_range_start(struct mm_struct * mm,unsigned long start,unsigned long end)283 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
284 unsigned long start, unsigned long end)
285 {
286 if (mm_has_notifiers(mm))
287 __mmu_notifier_invalidate_range_start(mm, start, end, true);
288 }
289
mmu_notifier_invalidate_range_start_nonblock(struct mm_struct * mm,unsigned long start,unsigned long end)290 static inline int mmu_notifier_invalidate_range_start_nonblock(struct mm_struct *mm,
291 unsigned long start, unsigned long end)
292 {
293 if (mm_has_notifiers(mm))
294 return __mmu_notifier_invalidate_range_start(mm, start, end, false);
295 return 0;
296 }
297
mmu_notifier_invalidate_range_end(struct mm_struct * mm,unsigned long start,unsigned long end)298 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
299 unsigned long start, unsigned long end)
300 {
301 if (mm_has_notifiers(mm))
302 __mmu_notifier_invalidate_range_end(mm, start, end, false);
303 }
304
mmu_notifier_invalidate_range_only_end(struct mm_struct * mm,unsigned long start,unsigned long end)305 static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,
306 unsigned long start, unsigned long end)
307 {
308 if (mm_has_notifiers(mm))
309 __mmu_notifier_invalidate_range_end(mm, start, end, true);
310 }
311
mmu_notifier_invalidate_range(struct mm_struct * mm,unsigned long start,unsigned long end)312 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
313 unsigned long start, unsigned long end)
314 {
315 if (mm_has_notifiers(mm))
316 __mmu_notifier_invalidate_range(mm, start, end);
317 }
318
mmu_notifier_mm_init(struct mm_struct * mm)319 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
320 {
321 mm->mmu_notifier_mm = NULL;
322 }
323
mmu_notifier_mm_destroy(struct mm_struct * mm)324 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
325 {
326 if (mm_has_notifiers(mm))
327 __mmu_notifier_mm_destroy(mm);
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
437 extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
438 void (*func)(struct rcu_head *rcu));
439 extern void mmu_notifier_synchronize(void);
440
441 #else /* CONFIG_MMU_NOTIFIER */
442
mm_has_notifiers(struct mm_struct * mm)443 static inline int mm_has_notifiers(struct mm_struct *mm)
444 {
445 return 0;
446 }
447
mmu_notifier_release(struct mm_struct * mm)448 static inline void mmu_notifier_release(struct mm_struct *mm)
449 {
450 }
451
mmu_notifier_clear_flush_young(struct mm_struct * mm,unsigned long start,unsigned long end)452 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
453 unsigned long start,
454 unsigned long end)
455 {
456 return 0;
457 }
458
mmu_notifier_test_young(struct mm_struct * mm,unsigned long address)459 static inline int mmu_notifier_test_young(struct mm_struct *mm,
460 unsigned long address)
461 {
462 return 0;
463 }
464
mmu_notifier_change_pte(struct mm_struct * mm,unsigned long address,pte_t pte)465 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
466 unsigned long address, pte_t pte)
467 {
468 }
469
mmu_notifier_invalidate_range_start(struct mm_struct * mm,unsigned long start,unsigned long end)470 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
471 unsigned long start, unsigned long end)
472 {
473 }
474
mmu_notifier_invalidate_range_start_nonblock(struct mm_struct * mm,unsigned long start,unsigned long end)475 static inline int mmu_notifier_invalidate_range_start_nonblock(struct mm_struct *mm,
476 unsigned long start, unsigned long end)
477 {
478 return 0;
479 }
480
mmu_notifier_invalidate_range_end(struct mm_struct * mm,unsigned long start,unsigned long end)481 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
482 unsigned long start, unsigned long end)
483 {
484 }
485
mmu_notifier_invalidate_range_only_end(struct mm_struct * mm,unsigned long start,unsigned long end)486 static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,
487 unsigned long start, unsigned long end)
488 {
489 }
490
mmu_notifier_invalidate_range(struct mm_struct * mm,unsigned long start,unsigned long end)491 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
492 unsigned long start, unsigned long end)
493 {
494 }
495
mm_has_blockable_invalidate_notifiers(struct mm_struct * mm)496 static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
497 {
498 return false;
499 }
500
mmu_notifier_mm_init(struct mm_struct * mm)501 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
502 {
503 }
504
mmu_notifier_mm_destroy(struct mm_struct * mm)505 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
506 {
507 }
508
509 #define ptep_clear_flush_young_notify ptep_clear_flush_young
510 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
511 #define ptep_clear_young_notify ptep_test_and_clear_young
512 #define pmdp_clear_young_notify pmdp_test_and_clear_young
513 #define ptep_clear_flush_notify ptep_clear_flush
514 #define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
515 #define pudp_huge_clear_flush_notify pudp_huge_clear_flush
516 #define set_pte_at_notify set_pte_at
517
518 #endif /* CONFIG_MMU_NOTIFIER */
519
520 #endif /* _LINUX_MMU_NOTIFIER_H */
521