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cddb8a5c AA |
1 | /* |
2 | * linux/mm/mmu_notifier.c | |
3 | * | |
4 | * Copyright (C) 2008 Qumranet, Inc. | |
5 | * Copyright (C) 2008 SGI | |
6 | * Christoph Lameter <clameter@sgi.com> | |
7 | * | |
8 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
9 | * the COPYING file in the top-level directory. | |
10 | */ | |
11 | ||
12 | #include <linux/rculist.h> | |
13 | #include <linux/mmu_notifier.h> | |
b95f1b31 | 14 | #include <linux/export.h> |
cddb8a5c AA |
15 | #include <linux/mm.h> |
16 | #include <linux/err.h> | |
17 | #include <linux/rcupdate.h> | |
18 | #include <linux/sched.h> | |
5a0e3ad6 | 19 | #include <linux/slab.h> |
cddb8a5c AA |
20 | |
21 | /* | |
22 | * This function can't run concurrently against mmu_notifier_register | |
23 | * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap | |
24 | * runs with mm_users == 0. Other tasks may still invoke mmu notifiers | |
25 | * in parallel despite there being no task using this mm any more, | |
26 | * through the vmas outside of the exit_mmap context, such as with | |
27 | * vmtruncate. This serializes against mmu_notifier_unregister with | |
28 | * the mmu_notifier_mm->lock in addition to RCU and it serializes | |
29 | * against the other mmu notifiers with RCU. struct mmu_notifier_mm | |
30 | * can't go away from under us as exit_mmap holds an mm_count pin | |
31 | * itself. | |
32 | */ | |
33 | void __mmu_notifier_release(struct mm_struct *mm) | |
34 | { | |
35 | struct mmu_notifier *mn; | |
3ad3d901 XG |
36 | struct hlist_node *n; |
37 | ||
38 | /* | |
39 | * RCU here will block mmu_notifier_unregister until | |
40 | * ->release returns. | |
41 | */ | |
42 | rcu_read_lock(); | |
43 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) | |
44 | /* | |
45 | * if ->release runs before mmu_notifier_unregister it | |
46 | * must be handled as it's the only way for the driver | |
47 | * to flush all existing sptes and stop the driver | |
48 | * from establishing any more sptes before all the | |
49 | * pages in the mm are freed. | |
50 | */ | |
51 | if (mn->ops->release) | |
52 | mn->ops->release(mn, mm); | |
53 | rcu_read_unlock(); | |
cddb8a5c AA |
54 | |
55 | spin_lock(&mm->mmu_notifier_mm->lock); | |
56 | while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) { | |
57 | mn = hlist_entry(mm->mmu_notifier_mm->list.first, | |
58 | struct mmu_notifier, | |
59 | hlist); | |
60 | /* | |
61 | * We arrived before mmu_notifier_unregister so | |
62 | * mmu_notifier_unregister will do nothing other than | |
63 | * to wait ->release to finish and | |
64 | * mmu_notifier_unregister to return. | |
65 | */ | |
66 | hlist_del_init_rcu(&mn->hlist); | |
cddb8a5c AA |
67 | } |
68 | spin_unlock(&mm->mmu_notifier_mm->lock); | |
69 | ||
70 | /* | |
71 | * synchronize_rcu here prevents mmu_notifier_release to | |
72 | * return to exit_mmap (which would proceed freeing all pages | |
73 | * in the mm) until the ->release method returns, if it was | |
74 | * invoked by mmu_notifier_unregister. | |
75 | * | |
76 | * The mmu_notifier_mm can't go away from under us because one | |
77 | * mm_count is hold by exit_mmap. | |
78 | */ | |
79 | synchronize_rcu(); | |
80 | } | |
81 | ||
82 | /* | |
83 | * If no young bitflag is supported by the hardware, ->clear_flush_young can | |
84 | * unmap the address and return 1 or 0 depending if the mapping previously | |
85 | * existed or not. | |
86 | */ | |
87 | int __mmu_notifier_clear_flush_young(struct mm_struct *mm, | |
88 | unsigned long address) | |
89 | { | |
90 | struct mmu_notifier *mn; | |
91 | struct hlist_node *n; | |
92 | int young = 0; | |
93 | ||
94 | rcu_read_lock(); | |
95 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
96 | if (mn->ops->clear_flush_young) | |
97 | young |= mn->ops->clear_flush_young(mn, mm, address); | |
98 | } | |
99 | rcu_read_unlock(); | |
100 | ||
101 | return young; | |
102 | } | |
103 | ||
8ee53820 AA |
104 | int __mmu_notifier_test_young(struct mm_struct *mm, |
105 | unsigned long address) | |
106 | { | |
107 | struct mmu_notifier *mn; | |
108 | struct hlist_node *n; | |
109 | int young = 0; | |
110 | ||
111 | rcu_read_lock(); | |
112 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
113 | if (mn->ops->test_young) { | |
114 | young = mn->ops->test_young(mn, mm, address); | |
115 | if (young) | |
116 | break; | |
117 | } | |
118 | } | |
119 | rcu_read_unlock(); | |
120 | ||
121 | return young; | |
122 | } | |
123 | ||
828502d3 IE |
124 | void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, |
125 | pte_t pte) | |
126 | { | |
127 | struct mmu_notifier *mn; | |
128 | struct hlist_node *n; | |
129 | ||
130 | rcu_read_lock(); | |
131 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
132 | if (mn->ops->change_pte) | |
133 | mn->ops->change_pte(mn, mm, address, pte); | |
134 | /* | |
135 | * Some drivers don't have change_pte, | |
136 | * so we must call invalidate_page in that case. | |
137 | */ | |
138 | else if (mn->ops->invalidate_page) | |
139 | mn->ops->invalidate_page(mn, mm, address); | |
140 | } | |
141 | rcu_read_unlock(); | |
142 | } | |
143 | ||
cddb8a5c AA |
144 | void __mmu_notifier_invalidate_page(struct mm_struct *mm, |
145 | unsigned long address) | |
146 | { | |
147 | struct mmu_notifier *mn; | |
148 | struct hlist_node *n; | |
149 | ||
150 | rcu_read_lock(); | |
151 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
152 | if (mn->ops->invalidate_page) | |
153 | mn->ops->invalidate_page(mn, mm, address); | |
154 | } | |
155 | rcu_read_unlock(); | |
156 | } | |
157 | ||
158 | void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, | |
159 | unsigned long start, unsigned long end) | |
160 | { | |
161 | struct mmu_notifier *mn; | |
162 | struct hlist_node *n; | |
163 | ||
164 | rcu_read_lock(); | |
165 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
166 | if (mn->ops->invalidate_range_start) | |
167 | mn->ops->invalidate_range_start(mn, mm, start, end); | |
168 | } | |
169 | rcu_read_unlock(); | |
170 | } | |
171 | ||
172 | void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, | |
173 | unsigned long start, unsigned long end) | |
174 | { | |
175 | struct mmu_notifier *mn; | |
176 | struct hlist_node *n; | |
177 | ||
178 | rcu_read_lock(); | |
179 | hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { | |
180 | if (mn->ops->invalidate_range_end) | |
181 | mn->ops->invalidate_range_end(mn, mm, start, end); | |
182 | } | |
183 | rcu_read_unlock(); | |
184 | } | |
185 | ||
186 | static int do_mmu_notifier_register(struct mmu_notifier *mn, | |
187 | struct mm_struct *mm, | |
188 | int take_mmap_sem) | |
189 | { | |
190 | struct mmu_notifier_mm *mmu_notifier_mm; | |
191 | int ret; | |
192 | ||
193 | BUG_ON(atomic_read(&mm->mm_users) <= 0); | |
194 | ||
195 | ret = -ENOMEM; | |
196 | mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); | |
197 | if (unlikely(!mmu_notifier_mm)) | |
198 | goto out; | |
199 | ||
200 | if (take_mmap_sem) | |
201 | down_write(&mm->mmap_sem); | |
202 | ret = mm_take_all_locks(mm); | |
203 | if (unlikely(ret)) | |
204 | goto out_cleanup; | |
205 | ||
206 | if (!mm_has_notifiers(mm)) { | |
207 | INIT_HLIST_HEAD(&mmu_notifier_mm->list); | |
208 | spin_lock_init(&mmu_notifier_mm->lock); | |
209 | mm->mmu_notifier_mm = mmu_notifier_mm; | |
210 | mmu_notifier_mm = NULL; | |
211 | } | |
212 | atomic_inc(&mm->mm_count); | |
213 | ||
214 | /* | |
215 | * Serialize the update against mmu_notifier_unregister. A | |
216 | * side note: mmu_notifier_release can't run concurrently with | |
217 | * us because we hold the mm_users pin (either implicitly as | |
218 | * current->mm or explicitly with get_task_mm() or similar). | |
219 | * We can't race against any other mmu notifier method either | |
220 | * thanks to mm_take_all_locks(). | |
221 | */ | |
222 | spin_lock(&mm->mmu_notifier_mm->lock); | |
223 | hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list); | |
224 | spin_unlock(&mm->mmu_notifier_mm->lock); | |
225 | ||
226 | mm_drop_all_locks(mm); | |
227 | out_cleanup: | |
228 | if (take_mmap_sem) | |
229 | up_write(&mm->mmap_sem); | |
230 | /* kfree() does nothing if mmu_notifier_mm is NULL */ | |
231 | kfree(mmu_notifier_mm); | |
232 | out: | |
233 | BUG_ON(atomic_read(&mm->mm_users) <= 0); | |
234 | return ret; | |
235 | } | |
236 | ||
237 | /* | |
238 | * Must not hold mmap_sem nor any other VM related lock when calling | |
239 | * this registration function. Must also ensure mm_users can't go down | |
240 | * to zero while this runs to avoid races with mmu_notifier_release, | |
241 | * so mm has to be current->mm or the mm should be pinned safely such | |
242 | * as with get_task_mm(). If the mm is not current->mm, the mm_users | |
243 | * pin should be released by calling mmput after mmu_notifier_register | |
244 | * returns. mmu_notifier_unregister must be always called to | |
245 | * unregister the notifier. mm_count is automatically pinned to allow | |
246 | * mmu_notifier_unregister to safely run at any time later, before or | |
247 | * after exit_mmap. ->release will always be called before exit_mmap | |
248 | * frees the pages. | |
249 | */ | |
250 | int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) | |
251 | { | |
252 | return do_mmu_notifier_register(mn, mm, 1); | |
253 | } | |
254 | EXPORT_SYMBOL_GPL(mmu_notifier_register); | |
255 | ||
256 | /* | |
257 | * Same as mmu_notifier_register but here the caller must hold the | |
258 | * mmap_sem in write mode. | |
259 | */ | |
260 | int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) | |
261 | { | |
262 | return do_mmu_notifier_register(mn, mm, 0); | |
263 | } | |
264 | EXPORT_SYMBOL_GPL(__mmu_notifier_register); | |
265 | ||
266 | /* this is called after the last mmu_notifier_unregister() returned */ | |
267 | void __mmu_notifier_mm_destroy(struct mm_struct *mm) | |
268 | { | |
269 | BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list)); | |
270 | kfree(mm->mmu_notifier_mm); | |
271 | mm->mmu_notifier_mm = LIST_POISON1; /* debug */ | |
272 | } | |
273 | ||
274 | /* | |
275 | * This releases the mm_count pin automatically and frees the mm | |
276 | * structure if it was the last user of it. It serializes against | |
277 | * running mmu notifiers with RCU and against mmu_notifier_unregister | |
278 | * with the unregister lock + RCU. All sptes must be dropped before | |
279 | * calling mmu_notifier_unregister. ->release or any other notifier | |
280 | * method may be invoked concurrently with mmu_notifier_unregister, | |
281 | * and only after mmu_notifier_unregister returned we're guaranteed | |
282 | * that ->release or any other method can't run anymore. | |
283 | */ | |
284 | void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm) | |
285 | { | |
286 | BUG_ON(atomic_read(&mm->mm_count) <= 0); | |
287 | ||
cddb8a5c | 288 | if (!hlist_unhashed(&mn->hlist)) { |
cddb8a5c AA |
289 | /* |
290 | * RCU here will force exit_mmap to wait ->release to finish | |
291 | * before freeing the pages. | |
292 | */ | |
293 | rcu_read_lock(); | |
3ad3d901 | 294 | |
cddb8a5c AA |
295 | /* |
296 | * exit_mmap will block in mmu_notifier_release to | |
297 | * guarantee ->release is called before freeing the | |
298 | * pages. | |
299 | */ | |
300 | if (mn->ops->release) | |
301 | mn->ops->release(mn, mm); | |
302 | rcu_read_unlock(); | |
3ad3d901 XG |
303 | |
304 | spin_lock(&mm->mmu_notifier_mm->lock); | |
305 | hlist_del_rcu(&mn->hlist); | |
cddb8a5c | 306 | spin_unlock(&mm->mmu_notifier_mm->lock); |
3ad3d901 | 307 | } |
cddb8a5c AA |
308 | |
309 | /* | |
310 | * Wait any running method to finish, of course including | |
311 | * ->release if it was run by mmu_notifier_relase instead of us. | |
312 | */ | |
313 | synchronize_rcu(); | |
314 | ||
315 | BUG_ON(atomic_read(&mm->mm_count) <= 0); | |
316 | ||
317 | mmdrop(mm); | |
318 | } | |
319 | EXPORT_SYMBOL_GPL(mmu_notifier_unregister); |