include/linux/mmu_notifier.h

   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
   9 struct mmu_notifier;
  10 struct 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  */
  20 struct 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
  27 struct 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  */
 157 struct mmu_notifier {
 158         struct hlist_node hlist;
 159         const struct mmu_notifier_ops *ops;
 160 };
 161
 162 static inline int mm_has_notifiers(struct mm_struct *mm)
 163 {
 164         return unlikely(mm->mmu_notifier_mm);
 165 }
 166
 167 extern int mmu_notifier_register(struct mmu_notifier *mn,
 168                                  struct mm_struct *mm);
 169 extern int __mmu_notifier_register(struct mmu_notifier *mn,
 170                                    struct mm_struct *mm);
 171 extern void mmu_notifier_unregister(struct mmu_notifier *mn,
 172                                     struct mm_struct *mm);
 173 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
 174 extern void __mmu_notifier_release(struct mm_struct *mm);
 175 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
 176                                           unsigned long address);
 177 extern int __mmu_notifier_test_young(struct mm_struct *mm,
 178                                      unsigned long address);
 179 extern void __mmu_notifier_change_pte(struct mm_struct *mm,
 180                                       unsigned long address, pte_t pte);
 181 extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
 182                                           unsigned long address);
 183 extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 184                                   unsigned long start, unsigned long end);
 185 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 186                                   unsigned long start, unsigned long end);
 187
 188 static inline void mmu_notifier_release(struct mm_struct *mm)
 189 {
 190         if (mm_has_notifiers(mm))
 191                 __mmu_notifier_release(mm);
 192 }
 193
 194 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 195                                           unsigned long address)
 196 {
 197         if (mm_has_notifiers(mm))
 198                 return __mmu_notifier_clear_flush_young(mm, address);
 199         return 0;
 200 }
 201
 202 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 203                                           unsigned long address)
 204 {
 205         if (mm_has_notifiers(mm))
 206                 return __mmu_notifier_test_young(mm, address);
 207         return 0;
 208 }
 209
 210 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 211                                            unsigned long address, pte_t pte)
 212 {
 213         if (mm_has_notifiers(mm))
 214                 __mmu_notifier_change_pte(mm, address, pte);
 215 }
 216
 217 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 218                                           unsigned long address)
 219 {
 220         if (mm_has_notifiers(mm))
 221                 __mmu_notifier_invalidate_page(mm, address);
 222 }
 223
 224 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 225                                   unsigned long start, unsigned long end)
 226 {
 227         if (mm_has_notifiers(mm))
 228                 __mmu_notifier_invalidate_range_start(mm, start, end);
 229 }
 230
 231 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 232                                   unsigned long start, unsigned long end)
 233 {
 234         if (mm_has_notifiers(mm))
 235                 __mmu_notifier_invalidate_range_end(mm, start, end);
 236 }
 237
 238 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 239 {
 240         mm->mmu_notifier_mm = NULL;
 241 }
 242
 243 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 244 {
 245         if (mm_has_notifiers(mm))
 246                 __mmu_notifier_mm_destroy(mm);
 247 }
 248
 249 #define ptep_clear_flush_young_notify(__vma, __address, __ptep)         \
 250 ({                                                                      \
 251         int __young;                                                    \
 252         struct vm_area_struct *___vma = __vma;                          \
 253         unsigned long ___address = __address;                           \
 254         __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
 255         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 256                                                   ___address);          \
 257         __young;                                                        \
 258 })
 259
 260 #define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)         \
 261 ({                                                                      \
 262         int __young;                                                    \
 263         struct vm_area_struct *___vma = __vma;                          \
 264         unsigned long ___address = __address;                           \
 265         __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
 266         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 267                                                   ___address);          \
 268         __young;                                                        \
 269 })
 270
 271 /*
 272  * set_pte_at_notify() sets the pte _after_ running the notifier.
 273  * This is safe to start by updating the secondary MMUs, because the primary MMU
 274  * pte invalidate must have already happened with a ptep_clear_flush() before
 275  * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 276  * required when we change both the protection of the mapping from read-only to
 277  * read-write and the pfn (like during copy on write page faults). Otherwise the
 278  * old page would remain mapped readonly in the secondary MMUs after the new
 279  * page is already writable by some CPU through the primary MMU.
 280  */
 281 #define set_pte_at_notify(__mm, __address, __ptep, __pte)               \
 282 ({                                                                      \
 283         struct mm_struct *___mm = __mm;                                 \
 284         unsigned long ___address = __address;                           \
 285         pte_t ___pte = __pte;                                           \
 286                                                                         \
 287         mmu_notifier_change_pte(___mm, ___address, ___pte);             \
 288         set_pte_at(___mm, ___address, __ptep, ___pte);                  \
 289 })
 290
 291 #else /* CONFIG_MMU_NOTIFIER */
 292
 293 static inline void mmu_notifier_release(struct mm_struct *mm)
 294 {
 295 }
 296
 297 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 298                                           unsigned long address)
 299 {
 300         return 0;
 301 }
 302
 303 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 304                                           unsigned long address)
 305 {
 306         return 0;
 307 }
 308
 309 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 310                                            unsigned long address, pte_t pte)
 311 {
 312 }
 313
 314 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 315                                           unsigned long address)
 316 {
 317 }
 318
 319 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 320                                   unsigned long start, unsigned long end)
 321 {
 322 }
 323
 324 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 325                                   unsigned long start, unsigned long end)
 326 {
 327 }
 328
 329 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 330 {
 331 }
 332
 333 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 334 {
 335 }
 336
 337 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 338 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
 339 #define set_pte_at_notify set_pte_at
 340
 341 #endif /* CONFIG_MMU_NOTIFIER */
 342
 343 #endif /* _LINUX_MMU_NOTIFIER_H */