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          * Start-end is necessary in case the secondary MMU is mapping the page
  61          * at a smaller granularity than the primary MMU.
  62          */
  63         int (*clear_flush_young)(struct mmu_notifier *mn,
  64                                  struct mm_struct *mm,
  65                                  unsigned long start,
  66                                  unsigned long end);
  67
  68         /*
  69          * clear_young is a lightweight version of clear_flush_young. Like the
  70          * latter, it is supposed to test-and-clear the young/accessed bitflag
  71          * in the secondary pte, but it may omit flushing the secondary tlb.
  72          */
  73         int (*clear_young)(struct mmu_notifier *mn,
  74                            struct mm_struct *mm,
  75                            unsigned long start,
  76                            unsigned long end);
  77
  78         /*
  79          * test_young is called to check the young/accessed bitflag in
  80          * the secondary pte. This is used to know if the page is
  81          * frequently used without actually clearing the flag or tearing
  82          * down the secondary mapping on the page.
  83          */
  84         int (*test_young)(struct mmu_notifier *mn,
  85                           struct mm_struct *mm,
  86                           unsigned long address);
  87
  88         /*
  89          * change_pte is called in cases that pte mapping to page is changed:
  90          * for example, when ksm remaps pte to point to a new shared page.
  91          */
  92         void (*change_pte)(struct mmu_notifier *mn,
  93                            struct mm_struct *mm,
  94                            unsigned long address,
  95                            pte_t pte);
  96
  97         /*
  98          * Before this is invoked any secondary MMU is still ok to
  99          * read/write to the page previously pointed to by the Linux
 100          * pte because the page hasn't been freed yet and it won't be
 101          * freed until this returns. If required set_page_dirty has to
 102          * be called internally to this method.
 103          */
 104         void (*invalidate_page)(struct mmu_notifier *mn,
 105                                 struct mm_struct *mm,
 106                                 unsigned long address);
 107
 108         /*
 109          * invalidate_range_start() and invalidate_range_end() must be
 110          * paired and are called only when the mmap_sem and/or the
 111          * locks protecting the reverse maps are held. If the subsystem
 112          * can't guarantee that no additional references are taken to
 113          * the pages in the range, it has to implement the
 114          * invalidate_range() notifier to remove any references taken
 115          * after invalidate_range_start().
 116          *
 117          * Invalidation of multiple concurrent ranges may be
 118          * optionally permitted by the driver. Either way the
 119          * establishment of sptes is forbidden in the range passed to
 120          * invalidate_range_begin/end for the whole duration of the
 121          * invalidate_range_begin/end critical section.
 122          *
 123          * invalidate_range_start() is called when all pages in the
 124          * range are still mapped and have at least a refcount of one.
 125          *
 126          * invalidate_range_end() is called when all pages in the
 127          * range have been unmapped and the pages have been freed by
 128          * the VM.
 129          *
 130          * The VM will remove the page table entries and potentially
 131          * the page between invalidate_range_start() and
 132          * invalidate_range_end(). If the page must not be freed
 133          * because of pending I/O or other circumstances then the
 134          * invalidate_range_start() callback (or the initial mapping
 135          * by the driver) must make sure that the refcount is kept
 136          * elevated.
 137          *
 138          * If the driver increases the refcount when the pages are
 139          * initially mapped into an address space then either
 140          * invalidate_range_start() or invalidate_range_end() may
 141          * decrease the refcount. If the refcount is decreased on
 142          * invalidate_range_start() then the VM can free pages as page
 143          * table entries are removed.  If the refcount is only
 144          * droppped on invalidate_range_end() then the driver itself
 145          * will drop the last refcount but it must take care to flush
 146          * any secondary tlb before doing the final free on the
 147          * page. Pages will no longer be referenced by the linux
 148          * address space but may still be referenced by sptes until
 149          * the last refcount is dropped.
 150          */
 151         void (*invalidate_range_start)(struct mmu_notifier *mn,
 152                                        struct mm_struct *mm,
 153                                        unsigned long start, unsigned long end);
 154         void (*invalidate_range_end)(struct mmu_notifier *mn,
 155                                      struct mm_struct *mm,
 156                                      unsigned long start, unsigned long end);
 157
 158         /*
 159          * invalidate_range() is either called between
 160          * invalidate_range_start() and invalidate_range_end() when the
 161          * VM has to free pages that where unmapped, but before the
 162          * pages are actually freed, or outside of _start()/_end() when
 163          * a (remote) TLB is necessary.
 164          *
 165          * If invalidate_range() is used to manage a non-CPU TLB with
 166          * shared page-tables, it not necessary to implement the
 167          * invalidate_range_start()/end() notifiers, as
 168          * invalidate_range() alread catches the points in time when an
 169          * external TLB range needs to be flushed.
 170          *
 171          * The invalidate_range() function is called under the ptl
 172          * spin-lock and not allowed to sleep.
 173          *
 174          * Note that this function might be called with just a sub-range
 175          * of what was passed to invalidate_range_start()/end(), if
 176          * called between those functions.
 177          */
 178         void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
 179                                  unsigned long start, unsigned long end);
 180 };
 181
 182 /*
 183  * The notifier chains are protected by mmap_sem and/or the reverse map
 184  * semaphores. Notifier chains are only changed when all reverse maps and
 185  * the mmap_sem locks are taken.
 186  *
 187  * Therefore notifier chains can only be traversed when either
 188  *
 189  * 1. mmap_sem is held.
 190  * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
 191  * 3. No other concurrent thread can access the list (release)
 192  */
 193 struct mmu_notifier {
 194         struct hlist_node hlist;
 195         const struct mmu_notifier_ops *ops;
 196 };
 197
 198 static inline int mm_has_notifiers(struct mm_struct *mm)
 199 {
 200         return unlikely(mm->mmu_notifier_mm);
 201 }
 202
 203 extern int mmu_notifier_register(struct mmu_notifier *mn,
 204                                  struct mm_struct *mm);
 205 extern int __mmu_notifier_register(struct mmu_notifier *mn,
 206                                    struct mm_struct *mm);
 207 extern void mmu_notifier_unregister(struct mmu_notifier *mn,
 208                                     struct mm_struct *mm);
 209 extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
 210                                                struct mm_struct *mm);
 211 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
 212 extern void __mmu_notifier_release(struct mm_struct *mm);
 213 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
 214                                           unsigned long start,
 215                                           unsigned long end);
 216 extern int __mmu_notifier_clear_young(struct mm_struct *mm,
 217                                       unsigned long start,
 218                                       unsigned long end);
 219 extern int __mmu_notifier_test_young(struct mm_struct *mm,
 220                                      unsigned long address);
 221 extern void __mmu_notifier_change_pte(struct mm_struct *mm,
 222                                       unsigned long address, pte_t pte);
 223 extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
 224                                           unsigned long address);
 225 extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 226                                   unsigned long start, unsigned long end);
 227 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 228                                   unsigned long start, unsigned long end);
 229 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 230                                   unsigned long start, unsigned long end);
 231
 232 static inline void mmu_notifier_release(struct mm_struct *mm)
 233 {
 234         if (mm_has_notifiers(mm))
 235                 __mmu_notifier_release(mm);
 236 }
 237
 238 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 239                                           unsigned long start,
 240                                           unsigned long end)
 241 {
 242         if (mm_has_notifiers(mm))
 243                 return __mmu_notifier_clear_flush_young(mm, start, end);
 244         return 0;
 245 }
 246
 247 static inline int mmu_notifier_clear_young(struct mm_struct *mm,
 248                                            unsigned long start,
 249                                            unsigned long end)
 250 {
 251         if (mm_has_notifiers(mm))
 252                 return __mmu_notifier_clear_young(mm, start, end);
 253         return 0;
 254 }
 255
 256 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 257                                           unsigned long address)
 258 {
 259         if (mm_has_notifiers(mm))
 260                 return __mmu_notifier_test_young(mm, address);
 261         return 0;
 262 }
 263
 264 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 265                                            unsigned long address, pte_t pte)
 266 {
 267         if (mm_has_notifiers(mm))
 268                 __mmu_notifier_change_pte(mm, address, pte);
 269 }
 270
 271 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 272                                           unsigned long address)
 273 {
 274         if (mm_has_notifiers(mm))
 275                 __mmu_notifier_invalidate_page(mm, address);
 276 }
 277
 278 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 279                                   unsigned long start, unsigned long end)
 280 {
 281         if (mm_has_notifiers(mm))
 282                 __mmu_notifier_invalidate_range_start(mm, start, end);
 283 }
 284
 285 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 286                                   unsigned long start, unsigned long end)
 287 {
 288         if (mm_has_notifiers(mm))
 289                 __mmu_notifier_invalidate_range_end(mm, start, end);
 290 }
 291
 292 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 293                                   unsigned long start, unsigned long end)
 294 {
 295         if (mm_has_notifiers(mm))
 296                 __mmu_notifier_invalidate_range(mm, start, end);
 297 }
 298
 299 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 300 {
 301         mm->mmu_notifier_mm = NULL;
 302 }
 303
 304 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 305 {
 306         if (mm_has_notifiers(mm))
 307                 __mmu_notifier_mm_destroy(mm);
 308 }
 309
 310 #define ptep_clear_flush_young_notify(__vma, __address, __ptep)         \
 311 ({                                                                      \
 312         int __young;                                                    \
 313         struct vm_area_struct *___vma = __vma;                          \
 314         unsigned long ___address = __address;                           \
 315         __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
 316         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 317                                                   ___address,           \
 318                                                   ___address +          \
 319                                                         PAGE_SIZE);     \
 320         __young;                                                        \
 321 })
 322
 323 #define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)         \
 324 ({                                                                      \
 325         int __young;                                                    \
 326         struct vm_area_struct *___vma = __vma;                          \
 327         unsigned long ___address = __address;                           \
 328         __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
 329         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 330                                                   ___address,           \
 331                                                   ___address +          \
 332                                                         PMD_SIZE);      \
 333         __young;                                                        \
 334 })
 335
 336 #define ptep_clear_young_notify(__vma, __address, __ptep)               \
 337 ({                                                                      \
 338         int __young;                                                    \
 339         struct vm_area_struct *___vma = __vma;                          \
 340         unsigned long ___address = __address;                           \
 341         __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\
 342         __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
 343                                             ___address + PAGE_SIZE);    \
 344         __young;                                                        \
 345 })
 346
 347 #define pmdp_clear_young_notify(__vma, __address, __pmdp)               \
 348 ({                                                                      \
 349         int __young;                                                    \
 350         struct vm_area_struct *___vma = __vma;                          \
 351         unsigned long ___address = __address;                           \
 352         __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\
 353         __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
 354                                             ___address + PMD_SIZE);     \
 355         __young;                                                        \
 356 })
 357
 358 #define ptep_clear_flush_notify(__vma, __address, __ptep)               \
 359 ({                                                                      \
 360         unsigned long ___addr = __address & PAGE_MASK;                  \
 361         struct mm_struct *___mm = (__vma)->vm_mm;                       \
 362         pte_t ___pte;                                                   \
 363                                                                         \
 364         ___pte = ptep_clear_flush(__vma, __address, __ptep);            \
 365         mmu_notifier_invalidate_range(___mm, ___addr,                   \
 366                                         ___addr + PAGE_SIZE);           \
 367                                                                         \
 368         ___pte;                                                         \
 369 })
 370
 371 #define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd)             \
 372 ({                                                                      \
 373         unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;              \
 374         struct mm_struct *___mm = (__vma)->vm_mm;                       \
 375         pmd_t ___pmd;                                                   \
 376                                                                         \
 377         ___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd);          \
 378         mmu_notifier_invalidate_range(___mm, ___haddr,                  \
 379                                       ___haddr + HPAGE_PMD_SIZE);       \
 380                                                                         \
 381         ___pmd;                                                         \
 382 })
 383
 384 #define pmdp_huge_get_and_clear_notify(__mm, __haddr, __pmd)            \
 385 ({                                                                      \
 386         unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;              \
 387         pmd_t ___pmd;                                                   \
 388                                                                         \
 389         ___pmd = pmdp_huge_get_and_clear(__mm, __haddr, __pmd);         \
 390         mmu_notifier_invalidate_range(__mm, ___haddr,                   \
 391                                       ___haddr + HPAGE_PMD_SIZE);       \
 392                                                                         \
 393         ___pmd;                                                         \
 394 })
 395
 396 /*
 397  * set_pte_at_notify() sets the pte _after_ running the notifier.
 398  * This is safe to start by updating the secondary MMUs, because the primary MMU
 399  * pte invalidate must have already happened with a ptep_clear_flush() before
 400  * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 401  * required when we change both the protection of the mapping from read-only to
 402  * read-write and the pfn (like during copy on write page faults). Otherwise the
 403  * old page would remain mapped readonly in the secondary MMUs after the new
 404  * page is already writable by some CPU through the primary MMU.
 405  */
 406 #define set_pte_at_notify(__mm, __address, __ptep, __pte)               \
 407 ({                                                                      \
 408         struct mm_struct *___mm = __mm;                                 \
 409         unsigned long ___address = __address;                           \
 410         pte_t ___pte = __pte;                                           \
 411                                                                         \
 412         mmu_notifier_change_pte(___mm, ___address, ___pte);             \
 413         set_pte_at(___mm, ___address, __ptep, ___pte);                  \
 414 })
 415
 416 extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
 417                                    void (*func)(struct rcu_head *rcu));
 418 extern void mmu_notifier_synchronize(void);
 419
 420 #else /* CONFIG_MMU_NOTIFIER */
 421
 422 static inline void mmu_notifier_release(struct mm_struct *mm)
 423 {
 424 }
 425
 426 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 427                                           unsigned long start,
 428                                           unsigned long end)
 429 {
 430         return 0;
 431 }
 432
 433 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 434                                           unsigned long address)
 435 {
 436         return 0;
 437 }
 438
 439 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 440                                            unsigned long address, pte_t pte)
 441 {
 442 }
 443
 444 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 445                                           unsigned long address)
 446 {
 447 }
 448
 449 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 450                                   unsigned long start, unsigned long end)
 451 {
 452 }
 453
 454 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 455                                   unsigned long start, unsigned long end)
 456 {
 457 }
 458
 459 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 460                                   unsigned long start, unsigned long end)
 461 {
 462 }
 463
 464 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 465 {
 466 }
 467
 468 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 469 {
 470 }
 471
 472 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 473 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
 474 #define ptep_clear_young_notify ptep_test_and_clear_young
 475 #define pmdp_clear_young_notify pmdp_test_and_clear_young
 476 #define ptep_clear_flush_notify ptep_clear_flush
 477 #define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
 478 #define pmdp_huge_get_and_clear_notify pmdp_huge_get_and_clear
 479 #define set_pte_at_notify set_pte_at
 480
 481 #endif /* CONFIG_MMU_NOTIFIER */
 482
 483 #endif /* _LINUX_MMU_NOTIFIER_H */