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