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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 */
61 int (*clear_flush_young)(struct mmu_notifier *mn,
62 struct mm_struct *mm,
63 unsigned long address);
64
65 /*
66 * test_young is called to check the young/accessed bitflag in
67 * the secondary pte. This is used to know if the page is
68 * frequently used without actually clearing the flag or tearing
69 * down the secondary mapping on the page.
70 */
71 int (*test_young)(struct mmu_notifier *mn,
72 struct mm_struct *mm,
73 unsigned long address);
74
75 /*
76 * change_pte is called in cases that pte mapping to page is changed:
77 * for example, when ksm remaps pte to point to a new shared page.
78 */
79 void (*change_pte)(struct mmu_notifier *mn,
80 struct mm_struct *mm,
81 unsigned long address,
82 pte_t pte);
83
84 /*
85 * Before this is invoked any secondary MMU is still ok to
86 * read/write to the page previously pointed to by the Linux
87 * pte because the page hasn't been freed yet and it won't be
88 * freed until this returns. If required set_page_dirty has to
89 * be called internally to this method.
90 */
91 void (*invalidate_page)(struct mmu_notifier *mn,
92 struct mm_struct *mm,
93 unsigned long address);
94
95 /*
96 * invalidate_range_start() and invalidate_range_end() must be
97 * paired and are called only when the mmap_sem and/or the
98 * locks protecting the reverse maps are held. The subsystem
99 * must guarantee that no additional references are taken to
100 * the pages in the range established between the call to
101 * invalidate_range_start() and the matching call to
102 * invalidate_range_end().
103 *
104 * Invalidation of multiple concurrent ranges may be
105 * optionally permitted by the driver. Either way the
106 * establishment of sptes is forbidden in the range passed to
107 * invalidate_range_begin/end for the whole duration of the
108 * invalidate_range_begin/end critical section.
109 *
110 * invalidate_range_start() is called when all pages in the
111 * range are still mapped and have at least a refcount of one.
112 *
113 * invalidate_range_end() is called when all pages in the
114 * range have been unmapped and the pages have been freed by
115 * the VM.
116 *
117 * The VM will remove the page table entries and potentially
118 * the page between invalidate_range_start() and
119 * invalidate_range_end(). If the page must not be freed
120 * because of pending I/O or other circumstances then the
121 * invalidate_range_start() callback (or the initial mapping
122 * by the driver) must make sure that the refcount is kept
123 * elevated.
124 *
125 * If the driver increases the refcount when the pages are
126 * initially mapped into an address space then either
127 * invalidate_range_start() or invalidate_range_end() may
128 * decrease the refcount. If the refcount is decreased on
129 * invalidate_range_start() then the VM can free pages as page
130 * table entries are removed. If the refcount is only
131 * droppped on invalidate_range_end() then the driver itself
132 * will drop the last refcount but it must take care to flush
133 * any secondary tlb before doing the final free on the
134 * page. Pages will no longer be referenced by the linux
135 * address space but may still be referenced by sptes until
136 * the last refcount is dropped.
137 */
138 void (*invalidate_range_start)(struct mmu_notifier *mn,
139 struct mm_struct *mm,
140 unsigned long start, unsigned long end);
141 void (*invalidate_range_end)(struct mmu_notifier *mn,
142 struct mm_struct *mm,
143 unsigned long start, unsigned long end);
144};
145
146/*
147 * The notifier chains are protected by mmap_sem and/or the reverse map
148 * semaphores. Notifier chains are only changed when all reverse maps and
149 * the mmap_sem locks are taken.
150 *
151 * Therefore notifier chains can only be traversed when either
152 *
153 * 1. mmap_sem is held.
154 * 2. One of the reverse map locks is held (i_mmap_mutex or anon_vma->rwsem).
155 * 3. No other concurrent thread can access the list (release)
156 */
157struct mmu_notifier {
158 struct hlist_node hlist;
159 const struct mmu_notifier_ops *ops;
160};
161
162static inline int mm_has_notifiers(struct mm_struct *mm)
163{
164 return unlikely(mm->mmu_notifier_mm);
165}
166
167extern int mmu_notifier_register(struct mmu_notifier *mn,
168 struct mm_struct *mm);
169extern int __mmu_notifier_register(struct mmu_notifier *mn,
170 struct mm_struct *mm);
171extern void mmu_notifier_unregister(struct mmu_notifier *mn,
172 struct mm_struct *mm);
173extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
174 struct mm_struct *mm);
175extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
176extern void __mmu_notifier_release(struct mm_struct *mm);
177extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
178 unsigned long address);
179extern int __mmu_notifier_test_young(struct mm_struct *mm,
180 unsigned long address);
181extern void __mmu_notifier_change_pte(struct mm_struct *mm,
182 unsigned long address, pte_t pte);
183extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
184 unsigned long address);
185extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
186 unsigned long start, unsigned long end);
187extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
188 unsigned long start, unsigned long end);
189
190static inline void mmu_notifier_release(struct mm_struct *mm)
191{
192 if (mm_has_notifiers(mm))
193 __mmu_notifier_release(mm);
194}
195
196static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
197 unsigned long address)
198{
199 if (mm_has_notifiers(mm))
200 return __mmu_notifier_clear_flush_young(mm, address);
201 return 0;
202}
203
204static inline int mmu_notifier_test_young(struct mm_struct *mm,
205 unsigned long address)
206{
207 if (mm_has_notifiers(mm))
208 return __mmu_notifier_test_young(mm, address);
209 return 0;
210}
211
212static inline void mmu_notifier_change_pte(struct mm_struct *mm,
213 unsigned long address, pte_t pte)
214{
215 if (mm_has_notifiers(mm))
216 __mmu_notifier_change_pte(mm, address, pte);
217}
218
219static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
220 unsigned long address)
221{
222 if (mm_has_notifiers(mm))
223 __mmu_notifier_invalidate_page(mm, address);
224}
225
226static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
227 unsigned long start, unsigned long end)
228{
229 if (mm_has_notifiers(mm))
230 __mmu_notifier_invalidate_range_start(mm, start, end);
231}
232
233static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
234 unsigned long start, unsigned long end)
235{
236 if (mm_has_notifiers(mm))
237 __mmu_notifier_invalidate_range_end(mm, start, end);
238}
239
240static inline void mmu_notifier_mm_init(struct mm_struct *mm)
241{
242 mm->mmu_notifier_mm = NULL;
243}
244
245static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
246{
247 if (mm_has_notifiers(mm))
248 __mmu_notifier_mm_destroy(mm);
249}
250
251#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \
252({ \
253 int __young; \
254 struct vm_area_struct *___vma = __vma; \
255 unsigned long ___address = __address; \
256 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \
257 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
258 ___address); \
259 __young; \
260})
261
262#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \
263({ \
264 int __young; \
265 struct vm_area_struct *___vma = __vma; \
266 unsigned long ___address = __address; \
267 __young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \
268 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \
269 ___address); \
270 __young; \
271})
272
273/*
274 * set_pte_at_notify() sets the pte _after_ running the notifier.
275 * This is safe to start by updating the secondary MMUs, because the primary MMU
276 * pte invalidate must have already happened with a ptep_clear_flush() before
277 * set_pte_at_notify() has been invoked. Updating the secondary MMUs first is
278 * required when we change both the protection of the mapping from read-only to
279 * read-write and the pfn (like during copy on write page faults). Otherwise the
280 * old page would remain mapped readonly in the secondary MMUs after the new
281 * page is already writable by some CPU through the primary MMU.
282 */
283#define set_pte_at_notify(__mm, __address, __ptep, __pte) \
284({ \
285 struct mm_struct *___mm = __mm; \
286 unsigned long ___address = __address; \
287 pte_t ___pte = __pte; \
288 \
289 mmu_notifier_change_pte(___mm, ___address, ___pte); \
290 set_pte_at(___mm, ___address, __ptep, ___pte); \
291})
292
293extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
294 void (*func)(struct rcu_head *rcu));
295extern void mmu_notifier_synchronize(void);
296
297#else /* CONFIG_MMU_NOTIFIER */
298
299static inline void mmu_notifier_release(struct mm_struct *mm)
300{
301}
302
303static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
304 unsigned long address)
305{
306 return 0;
307}
308
309static inline int mmu_notifier_test_young(struct mm_struct *mm,
310 unsigned long address)
311{
312 return 0;
313}
314
315static inline void mmu_notifier_change_pte(struct mm_struct *mm,
316 unsigned long address, pte_t pte)
317{
318}
319
320static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
321 unsigned long address)
322{
323}
324
325static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
326 unsigned long start, unsigned long end)
327{
328}
329
330static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
331 unsigned long start, unsigned long end)
332{
333}
334
335static inline void mmu_notifier_mm_init(struct mm_struct *mm)
336{
337}
338
339static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
340{
341}
342
343#define ptep_clear_flush_young_notify ptep_clear_flush_young
344#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
345#define set_pte_at_notify set_pte_at
346
347#endif /* CONFIG_MMU_NOTIFIER */
348
349#endif /* _LINUX_MMU_NOTIFIER_H */