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1#ifndef _LINUX_MMU_NOTIFIER_H
2#define _LINUX_MMU_NOTIFIER_H
3
4#include <linux/list.h>
5#include <linux/spinlock.h>
6#include <linux/mm_types.h>
7#include <linux/srcu.h>
8
9struct mmu_notifier;
10struct mmu_notifier_ops;
11
12#ifdef CONFIG_MMU_NOTIFIER
13
14/*
15 * The mmu notifier_mm structure is allocated and installed in
16 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
17 * critical section and it's released only when mm_count reaches zero
18 * in mmdrop().
19 */
20struct mmu_notifier_mm {
21 /* all mmu notifiers registerd in this mm are queued in this list */
22 struct hlist_head list;
23 /* to serialize the list modifications and hlist_unhashed */
24 spinlock_t lock;
25};
26
27struct mmu_notifier_ops {
28 /*
29 * Called either by mmu_notifier_unregister or when the mm is
30 * being destroyed by exit_mmap, always before all pages are
31 * freed. This can run concurrently with other mmu notifier
32 * methods (the ones invoked outside the mm context) and it
33 * should tear down all secondary mmu mappings and freeze the
34 * secondary mmu. If this method isn't implemented you've to
35 * be sure that nothing could possibly write to the pages
36 * through the secondary mmu by the time the last thread with
37 * tsk->mm == mm exits.
38 *
39 * As side note: the pages freed after ->release returns could
40 * be immediately reallocated by the gart at an alias physical
41 * address with a different cache model, so if ->release isn't
42 * implemented because all _software_ driven memory accesses
43 * through the secondary mmu are terminated by the time the
44 * last thread of this mm quits, you've also to be sure that
45 * speculative _hardware_ operations can't allocate dirty
46 * cachelines in the cpu that could not be snooped and made
47 * coherent with the other read and write operations happening
48 * through the gart alias address, so leading to memory
49 * corruption.
50 */
51 void (*release)(struct mmu_notifier *mn,
52 struct mm_struct *mm);
53
54 /*
55 * clear_flush_young is called after the VM is
56 * test-and-clearing the young/accessed bitflag in the
57 * pte. This way the VM will provide proper aging to the
58 * accesses to the page through the secondary MMUs and not
59 * only to the ones through the Linux pte.
60 * Start-end is necessary in case the secondary MMU is mapping the page
61 * at a smaller granularity than the primary MMU.
62 */
63 int (*clear_flush_young)(struct mmu_notifier *mn,
64 struct mm_struct *mm,
65 unsigned long start,
66 unsigned long end);
67
68 /*
69 * test_young is called to check the young/accessed bitflag in
70 * the secondary pte. This is used to know if the page is
71 * frequently used without actually clearing the flag or tearing
72 * down the secondary mapping on the page.
73 */
74 int (*test_young)(struct mmu_notifier *mn,
75 struct mm_struct *mm,
76 unsigned long address);
77
78 /*
79 * change_pte is called in cases that pte mapping to page is changed:
80 * for example, when ksm remaps pte to point to a new shared page.
81 */
82 void (*change_pte)(struct mmu_notifier *mn,
83 struct mm_struct *mm,
84 unsigned long address,
85 pte_t pte);
86
87 /*
88 * Before this is invoked any secondary MMU is still ok to
89 * read/write to the page previously pointed to by the Linux
90 * pte because the page hasn't been freed yet and it won't be
91 * freed until this returns. If required set_page_dirty has to
92 * be called internally to this method.
93 */
94 void (*invalidate_page)(struct mmu_notifier *mn,
95 struct mm_struct *mm,
96 unsigned long address);
97
98 /*
99 * invalidate_range_start() and invalidate_range_end() must be
100 * paired and are called only when the mmap_sem and/or the
101 * locks protecting the reverse maps are held. The subsystem
102 * must guarantee that no additional references are taken to
103 * the pages in the range established between the call to
104 * invalidate_range_start() and the matching call to
105 * invalidate_range_end().
106 *
107 * Invalidation of multiple concurrent ranges may be
108 * optionally permitted by the driver. Either way the
109 * establishment of sptes is forbidden in the range passed to
110 * invalidate_range_begin/end for the whole duration of the
111 * invalidate_range_begin/end critical section.
112 *
113 * invalidate_range_start() is called when all pages in the
114 * range are still mapped and have at least a refcount of one.
115 *
116 * invalidate_range_end() is called when all pages in the
117 * range have been unmapped and the pages have been freed by
118 * the VM.
119 *
120 * The VM will remove the page table entries and potentially
121 * the page between invalidate_range_start() and
122 * invalidate_range_end(). If the page must not be freed
123 * because of pending I/O or other circumstances then the
124 * invalidate_range_start() callback (or the initial mapping
125 * by the driver) must make sure that the refcount is kept
126 * elevated.
127 *
128 * If the driver increases the refcount when the pages are
129 * initially mapped into an address space then either
130 * invalidate_range_start() or invalidate_range_end() may
131 * decrease the refcount. If the refcount is decreased on
132 * invalidate_range_start() then the VM can free pages as page
133 * table entries are removed. If the refcount is only
134 * droppped on invalidate_range_end() then the driver itself
135 * will drop the last refcount but it must take care to flush
136 * any secondary tlb before doing the final free on the
137 * page. Pages will no longer be referenced by the linux
138 * address space but may still be referenced by sptes until
139 * the last refcount is dropped.
140 */
141 void (*invalidate_range_start)(struct mmu_notifier *mn,
142 struct mm_struct *mm,
143 unsigned long start, unsigned long end);
144 void (*invalidate_range_end)(struct mmu_notifier *mn,
145 struct mm_struct *mm,
146 unsigned long start, unsigned long end);
147};
148
149/*
150 * The notifier chains are protected by mmap_sem and/or the reverse map
151 * semaphores. Notifier chains are only changed when all reverse maps and
152 * the mmap_sem locks are taken.
153 *
154 * Therefore notifier chains can only be traversed when either
155 *
156 * 1. mmap_sem is held.
157 * 2. One of the reverse map locks is held (i_mmap_mutex or anon_vma->rwsem).
158 * 3. No other concurrent thread can access the list (release)
159 */
160struct mmu_notifier {
161 struct hlist_node hlist;
162 const struct mmu_notifier_ops *ops;
163};
164
165static inline int mm_has_notifiers(struct mm_struct *mm)
166{
167 return unlikely(mm->mmu_notifier_mm);
168}
169
170extern int mmu_notifier_register(struct mmu_notifier *mn,
171 struct mm_struct *mm);
172extern int __mmu_notifier_register(struct mmu_notifier *mn,
173 struct mm_struct *mm);
174extern void mmu_notifier_unregister(struct mmu_notifier *mn,
175 struct mm_struct *mm);
176extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
177 struct mm_struct *mm);
178extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
179extern void __mmu_notifier_release(struct mm_struct *mm);
180extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
181 unsigned long start,
182 unsigned long end);
183extern int __mmu_notifier_test_young(struct mm_struct *mm,
184 unsigned long address);
185extern void __mmu_notifier_change_pte(struct mm_struct *mm,
186 unsigned long address, pte_t pte);
187extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
188 unsigned long address);
189extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
190 unsigned long start, unsigned long end);
191extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
192 unsigned long start, unsigned long end);
193
194static inline void mmu_notifier_release(struct mm_struct *mm)
195{
196 if (mm_has_notifiers(mm))
197 __mmu_notifier_release(mm);
198}
199
200static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
201 unsigned long start,
202 unsigned long end)
203{
204 if (mm_has_notifiers(mm))
205 return __mmu_notifier_clear_flush_young(mm, start, end);
206 return 0;
207}
208
209static inline int mmu_notifier_test_young(struct mm_struct *mm,
210 unsigned long address)
211{
212 if (mm_has_notifiers(mm))
213 return __mmu_notifier_test_young(mm, address);
214 return 0;
215}
216
217static inline void mmu_notifier_change_pte(struct mm_struct *mm,
218 unsigned long address, pte_t pte)
219{
220 if (mm_has_notifiers(mm))
221 __mmu_notifier_change_pte(mm, address, pte);
222}
223
224static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
225 unsigned long address)
226{
227 if (mm_has_notifiers(mm))
228 __mmu_notifier_invalidate_page(mm, address);
229}
230
231static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
232 unsigned long start, unsigned long end)
233{
234 if (mm_has_notifiers(mm))
235 __mmu_notifier_invalidate_range_start(mm, start, end);
236}
237
238static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
239 unsigned long start, unsigned long end)
240{
241 if (mm_has_notifiers(mm))
242 __mmu_notifier_invalidate_range_end(mm, start, end);
243}
244
245static inline void mmu_notifier_mm_init(struct mm_struct *mm)
246{
247 mm->mmu_notifier_mm = NULL;
248}
249
250static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
251{
252 if (mm_has_notifiers(mm))
253 __mmu_notifier_mm_destroy(mm);
254}
255
256#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \
257({ \
258 int __young; \
259 struct vm_area_struct *___vma = __vma; \
260 unsigned long ___address = __address; \
261 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \
262 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
263 ___address, \
264 ___address + \
265 PAGE_SIZE); \
266 __young; \
267})
268
269#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \
270({ \
271 int __young; \
272 struct vm_area_struct *___vma = __vma; \
273 unsigned long ___address = __address; \
274 __young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \
275 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
276 ___address, \
277 ___address + \
278 PMD_SIZE); \
279 __young; \
280})
281
282/*
283 * set_pte_at_notify() sets the pte _after_ running the notifier.
284 * This is safe to start by updating the secondary MMUs, because the primary MMU
285 * pte invalidate must have already happened with a ptep_clear_flush() before
286 * set_pte_at_notify() has been invoked. Updating the secondary MMUs first is
287 * required when we change both the protection of the mapping from read-only to
288 * read-write and the pfn (like during copy on write page faults). Otherwise the
289 * old page would remain mapped readonly in the secondary MMUs after the new
290 * page is already writable by some CPU through the primary MMU.
291 */
292#define set_pte_at_notify(__mm, __address, __ptep, __pte) \
293({ \
294 struct mm_struct *___mm = __mm; \
295 unsigned long ___address = __address; \
296 pte_t ___pte = __pte; \
297 \
298 mmu_notifier_change_pte(___mm, ___address, ___pte); \
299 set_pte_at(___mm, ___address, __ptep, ___pte); \
300})
301
302extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
303 void (*func)(struct rcu_head *rcu));
304extern void mmu_notifier_synchronize(void);
305
306#else /* CONFIG_MMU_NOTIFIER */
307
308static inline void mmu_notifier_release(struct mm_struct *mm)
309{
310}
311
312static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
313 unsigned long start,
314 unsigned long end)
315{
316 return 0;
317}
318
319static inline int mmu_notifier_test_young(struct mm_struct *mm,
320 unsigned long address)
321{
322 return 0;
323}
324
325static inline void mmu_notifier_change_pte(struct mm_struct *mm,
326 unsigned long address, pte_t pte)
327{
328}
329
330static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
331 unsigned long address)
332{
333}
334
335static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
336 unsigned long start, unsigned long end)
337{
338}
339
340static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
341 unsigned long start, unsigned long end)
342{
343}
344
345static inline void mmu_notifier_mm_init(struct mm_struct *mm)
346{
347}
348
349static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
350{
351}
352
353#define ptep_clear_flush_young_notify ptep_clear_flush_young
354#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
355#define set_pte_at_notify set_pte_at
356
357#endif /* CONFIG_MMU_NOTIFIER */
358
359#endif /* _LINUX_MMU_NOTIFIER_H */