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cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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>
b95f1b3 @paulgortmaker mm: Map most files to use export.h instead of module.h
paulgortmaker authored Oct 16, 2011
14 #include <linux/export.h>
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
15 #include <linux/mm.h>
16 #include <linux/err.h>
17 #include <linux/rcupdate.h>
18 #include <linux/sched.h>
5a0e3ad @htejun include cleanup: Update gfp.h and slab.h includes to prepare for brea…
htejun authored Mar 24, 2010
19 #include <linux/slab.h>
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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;
3ad3d90 mm: mmu_notifier: fix freed page still mapped in secondary MMU
Xiao Guangrong authored Jul 31, 2012
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();
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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);
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
8ee5382 thp: mmu_notifier_test_young
Andrea Arcangeli authored Jan 13, 2011
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
828502d ksm: add mmu_notifier set_pte_at_notify()
Izik Eidus authored Sep 21, 2009
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
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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
288 if (!hlist_unhashed(&mn->hlist)) {
289 /*
290 * RCU here will force exit_mmap to wait ->release to finish
291 * before freeing the pages.
292 */
293 rcu_read_lock();
3ad3d90 mm: mmu_notifier: fix freed page still mapped in secondary MMU
Xiao Guangrong authored Jul 31, 2012
294
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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();
3ad3d90 mm: mmu_notifier: fix freed page still mapped in secondary MMU
Xiao Guangrong authored Jul 31, 2012
303
304 spin_lock(&mm->mmu_notifier_mm->lock);
305 hlist_del_rcu(&mn->hlist);
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
306 spin_unlock(&mm->mmu_notifier_mm->lock);
3ad3d90 mm: mmu_notifier: fix freed page still mapped in secondary MMU
Xiao Guangrong authored Jul 31, 2012
307 }
cddb8a5 mmu-notifiers: core
Andrea Arcangeli authored Jul 28, 2008
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);
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