include/asm-generic/pgtable.h

   1 #ifndef _ASM_GENERIC_PGTABLE_H
   2 #define _ASM_GENERIC_PGTABLE_H
   3
   4 #ifndef __ASSEMBLY__
   5 #ifdef CONFIG_MMU
   6
   7 #include <linux/mm_types.h>
   8 #include <linux/bug.h>
   9 #include <linux/errno.h>
  10
  11 #if 4 - defined(__PAGETABLE_PUD_FOLDED) - defined(__PAGETABLE_PMD_FOLDED) != \
  12         CONFIG_PGTABLE_LEVELS
  13 #error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{PUD,PMD}_FOLDED
  14 #endif
  15
  16 /*
  17  * On almost all architectures and configurations, 0 can be used as the
  18  * upper ceiling to free_pgtables(): on many architectures it has the same
  19  * effect as using TASK_SIZE.  However, there is one configuration which
  20  * must impose a more careful limit, to avoid freeing kernel pgtables.
  21  */
  22 #ifndef USER_PGTABLES_CEILING
  23 #define USER_PGTABLES_CEILING   0UL
  24 #endif
  25
  26 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
  27 extern int ptep_set_access_flags(struct vm_area_struct *vma,
  28                                  unsigned long address, pte_t *ptep,
  29                                  pte_t entry, int dirty);
  30 #endif
  31
  32 #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
  33 extern int pmdp_set_access_flags(struct vm_area_struct *vma,
  34                                  unsigned long address, pmd_t *pmdp,
  35                                  pmd_t entry, int dirty);
  36 #endif
  37
  38 #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
  39 static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
  40                                             unsigned long address,
  41                                             pte_t *ptep)
  42 {
  43         pte_t pte = *ptep;
  44         int r = 1;
  45         if (!pte_young(pte))
  46                 r = 0;
  47         else
  48                 set_pte_at(vma->vm_mm, address, ptep, pte_mkold(pte));
  49         return r;
  50 }
  51 #endif
  52
  53 #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
  54 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  55 static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  56                                             unsigned long address,
  57                                             pmd_t *pmdp)
  58 {
  59         pmd_t pmd = *pmdp;
  60         int r = 1;
  61         if (!pmd_young(pmd))
  62                 r = 0;
  63         else
  64                 set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
  65         return r;
  66 }
  67 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
  68 static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  69                                             unsigned long address,
  70                                             pmd_t *pmdp)
  71 {
  72         BUG();
  73         return 0;
  74 }
  75 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  76 #endif
  77
  78 #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
  79 int ptep_clear_flush_young(struct vm_area_struct *vma,
  80                            unsigned long address, pte_t *ptep);
  81 #endif
  82
  83 #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
  84 int pmdp_clear_flush_young(struct vm_area_struct *vma,
  85                            unsigned long address, pmd_t *pmdp);
  86 #endif
  87
  88 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
  89 static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
  90                                        unsigned long address,
  91                                        pte_t *ptep)
  92 {
  93         pte_t pte = *ptep;
  94         pte_clear(mm, address, ptep);
  95         return pte;
  96 }
  97 #endif
  98
  99 #ifndef __HAVE_ARCH_PMDP_GET_AND_CLEAR
 100 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 101 static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
 102                                        unsigned long address,
 103                                        pmd_t *pmdp)
 104 {
 105         pmd_t pmd = *pmdp;
 106         pmd_clear(pmdp);
 107         return pmd;
 108 }
 109 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 110 #endif
 111
 112 #ifndef __HAVE_ARCH_PMDP_GET_AND_CLEAR_FULL
 113 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 114 static inline pmd_t pmdp_get_and_clear_full(struct mm_struct *mm,
 115                                             unsigned long address, pmd_t *pmdp,
 116                                             int full)
 117 {
 118         return pmdp_get_and_clear(mm, address, pmdp);
 119 }
 120 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 121 #endif
 122
 123 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
 124 static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 125                                             unsigned long address, pte_t *ptep,
 126                                             int full)
 127 {
 128         pte_t pte;
 129         pte = ptep_get_and_clear(mm, address, ptep);
 130         return pte;
 131 }
 132 #endif
 133
 134 /*
 135  * Some architectures may be able to avoid expensive synchronization
 136  * primitives when modifications are made to PTE's which are already
 137  * not present, or in the process of an address space destruction.
 138  */
 139 #ifndef __HAVE_ARCH_PTE_CLEAR_NOT_PRESENT_FULL
 140 static inline void pte_clear_not_present_full(struct mm_struct *mm,
 141                                               unsigned long address,
 142                                               pte_t *ptep,
 143                                               int full)
 144 {
 145         pte_clear(mm, address, ptep);
 146 }
 147 #endif
 148
 149 #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH
 150 extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
 151                               unsigned long address,
 152                               pte_t *ptep);
 153 #endif
 154
 155 #ifndef __HAVE_ARCH_PMDP_CLEAR_FLUSH
 156 extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma,
 157                               unsigned long address,
 158                               pmd_t *pmdp);
 159 #endif
 160
 161 #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT
 162 struct mm_struct;
 163 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep)
 164 {
 165         pte_t old_pte = *ptep;
 166         set_pte_at(mm, address, ptep, pte_wrprotect(old_pte));
 167 }
 168 #endif
 169
 170 #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
 171 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 172 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 173                                       unsigned long address, pmd_t *pmdp)
 174 {
 175         pmd_t old_pmd = *pmdp;
 176         set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
 177 }
 178 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 179 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 180                                       unsigned long address, pmd_t *pmdp)
 181 {
 182         BUG();
 183 }
 184 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 185 #endif
 186
 187 #ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
 188 extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 189                                  unsigned long address, pmd_t *pmdp);
 190 #endif
 191
 192 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
 193 extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 194                                        pgtable_t pgtable);
 195 #endif
 196
 197 #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
 198 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
 199 #endif
 200
 201 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
 202 extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 203                             pmd_t *pmdp);
 204 #endif
 205
 206 #ifndef __HAVE_ARCH_PTE_SAME
 207 static inline int pte_same(pte_t pte_a, pte_t pte_b)
 208 {
 209         return pte_val(pte_a) == pte_val(pte_b);
 210 }
 211 #endif
 212
 213 #ifndef __HAVE_ARCH_PTE_UNUSED
 214 /*
 215  * Some architectures provide facilities to virtualization guests
 216  * so that they can flag allocated pages as unused. This allows the
 217  * host to transparently reclaim unused pages. This function returns
 218  * whether the pte's page is unused.
 219  */
 220 static inline int pte_unused(pte_t pte)
 221 {
 222         return 0;
 223 }
 224 #endif
 225
 226 #ifndef __HAVE_ARCH_PMD_SAME
 227 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 228 static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 229 {
 230         return pmd_val(pmd_a) == pmd_val(pmd_b);
 231 }
 232 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 233 static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 234 {
 235         BUG();
 236         return 0;
 237 }
 238 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 239 #endif
 240
 241 #ifndef __HAVE_ARCH_PGD_OFFSET_GATE
 242 #define pgd_offset_gate(mm, addr)       pgd_offset(mm, addr)
 243 #endif
 244
 245 #ifndef __HAVE_ARCH_MOVE_PTE
 246 #define move_pte(pte, prot, old_addr, new_addr) (pte)
 247 #endif
 248
 249 #ifndef pte_accessible
 250 # define pte_accessible(mm, pte)        ((void)(pte), 1)
 251 #endif
 252
 253 #ifndef flush_tlb_fix_spurious_fault
 254 #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address)
 255 #endif
 256
 257 #ifndef pgprot_noncached
 258 #define pgprot_noncached(prot)  (prot)
 259 #endif
 260
 261 #ifndef pgprot_writecombine
 262 #define pgprot_writecombine pgprot_noncached
 263 #endif
 264
 265 #ifndef pgprot_device
 266 #define pgprot_device pgprot_noncached
 267 #endif
 268
 269 #ifndef pgprot_modify
 270 #define pgprot_modify pgprot_modify
 271 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 272 {
 273         if (pgprot_val(oldprot) == pgprot_val(pgprot_noncached(oldprot)))
 274                 newprot = pgprot_noncached(newprot);
 275         if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot)))
 276                 newprot = pgprot_writecombine(newprot);
 277         if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot)))
 278                 newprot = pgprot_device(newprot);
 279         return newprot;
 280 }
 281 #endif
 282
 283 /*
 284  * When walking page tables, get the address of the next boundary,
 285  * or the end address of the range if that comes earlier.  Although no
 286  * vma end wraps to 0, rounded up __boundary may wrap to 0 throughout.
 287  */
 288
 289 #define pgd_addr_end(addr, end)                                         \
 290 ({      unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK;  \
 291         (__boundary - 1 < (end) - 1)? __boundary: (end);                \
 292 })
 293
 294 #ifndef pud_addr_end
 295 #define pud_addr_end(addr, end)                                         \
 296 ({      unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK;      \
 297         (__boundary - 1 < (end) - 1)? __boundary: (end);                \
 298 })
 299 #endif
 300
 301 #ifndef pmd_addr_end
 302 #define pmd_addr_end(addr, end)                                         \
 303 ({      unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK;      \
 304         (__boundary - 1 < (end) - 1)? __boundary: (end);                \
 305 })
 306 #endif
 307
 308 /*
 309  * When walking page tables, we usually want to skip any p?d_none entries;
 310  * and any p?d_bad entries - reporting the error before resetting to none.
 311  * Do the tests inline, but report and clear the bad entry in mm/memory.c.
 312  */
 313 void pgd_clear_bad(pgd_t *);
 314 void pud_clear_bad(pud_t *);
 315 void pmd_clear_bad(pmd_t *);
 316
 317 static inline int pgd_none_or_clear_bad(pgd_t *pgd)
 318 {
 319         if (pgd_none(*pgd))
 320                 return 1;
 321         if (unlikely(pgd_bad(*pgd))) {
 322                 pgd_clear_bad(pgd);
 323                 return 1;
 324         }
 325         return 0;
 326 }
 327
 328 static inline int pud_none_or_clear_bad(pud_t *pud)
 329 {
 330         if (pud_none(*pud))
 331                 return 1;
 332         if (unlikely(pud_bad(*pud))) {
 333                 pud_clear_bad(pud);
 334                 return 1;
 335         }
 336         return 0;
 337 }
 338
 339 static inline int pmd_none_or_clear_bad(pmd_t *pmd)
 340 {
 341         if (pmd_none(*pmd))
 342                 return 1;
 343         if (unlikely(pmd_bad(*pmd))) {
 344                 pmd_clear_bad(pmd);
 345                 return 1;
 346         }
 347         return 0;
 348 }
 349
 350 static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm,
 351                                              unsigned long addr,
 352                                              pte_t *ptep)
 353 {
 354         /*
 355          * Get the current pte state, but zero it out to make it
 356          * non-present, preventing the hardware from asynchronously
 357          * updating it.
 358          */
 359         return ptep_get_and_clear(mm, addr, ptep);
 360 }
 361
 362 static inline void __ptep_modify_prot_commit(struct mm_struct *mm,
 363                                              unsigned long addr,
 364                                              pte_t *ptep, pte_t pte)
 365 {
 366         /*
 367          * The pte is non-present, so there's no hardware state to
 368          * preserve.
 369          */
 370         set_pte_at(mm, addr, ptep, pte);
 371 }
 372
 373 #ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
 374 /*
 375  * Start a pte protection read-modify-write transaction, which
 376  * protects against asynchronous hardware modifications to the pte.
 377  * The intention is not to prevent the hardware from making pte
 378  * updates, but to prevent any updates it may make from being lost.
 379  *
 380  * This does not protect against other software modifications of the
 381  * pte; the appropriate pte lock must be held over the transation.
 382  *
 383  * Note that this interface is intended to be batchable, meaning that
 384  * ptep_modify_prot_commit may not actually update the pte, but merely
 385  * queue the update to be done at some later time.  The update must be
 386  * actually committed before the pte lock is released, however.
 387  */
 388 static inline pte_t ptep_modify_prot_start(struct mm_struct *mm,
 389                                            unsigned long addr,
 390                                            pte_t *ptep)
 391 {
 392         return __ptep_modify_prot_start(mm, addr, ptep);
 393 }
 394
 395 /*
 396  * Commit an update to a pte, leaving any hardware-controlled bits in
 397  * the PTE unmodified.
 398  */
 399 static inline void ptep_modify_prot_commit(struct mm_struct *mm,
 400                                            unsigned long addr,
 401                                            pte_t *ptep, pte_t pte)
 402 {
 403         __ptep_modify_prot_commit(mm, addr, ptep, pte);
 404 }
 405 #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
 406 #endif /* CONFIG_MMU */
 407
 408 /*
 409  * A facility to provide lazy MMU batching.  This allows PTE updates and
 410  * page invalidations to be delayed until a call to leave lazy MMU mode
 411  * is issued.  Some architectures may benefit from doing this, and it is
 412  * beneficial for both shadow and direct mode hypervisors, which may batch
 413  * the PTE updates which happen during this window.  Note that using this
 414  * interface requires that read hazards be removed from the code.  A read
 415  * hazard could result in the direct mode hypervisor case, since the actual
 416  * write to the page tables may not yet have taken place, so reads though
 417  * a raw PTE pointer after it has been modified are not guaranteed to be
 418  * up to date.  This mode can only be entered and left under the protection of
 419  * the page table locks for all page tables which may be modified.  In the UP
 420  * case, this is required so that preemption is disabled, and in the SMP case,
 421  * it must synchronize the delayed page table writes properly on other CPUs.
 422  */
 423 #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 424 #define arch_enter_lazy_mmu_mode()      do {} while (0)
 425 #define arch_leave_lazy_mmu_mode()      do {} while (0)
 426 #define arch_flush_lazy_mmu_mode()      do {} while (0)
 427 #endif
 428
 429 /*
 430  * A facility to provide batching of the reload of page tables and
 431  * other process state with the actual context switch code for
 432  * paravirtualized guests.  By convention, only one of the batched
 433  * update (lazy) modes (CPU, MMU) should be active at any given time,
 434  * entry should never be nested, and entry and exits should always be
 435  * paired.  This is for sanity of maintaining and reasoning about the
 436  * kernel code.  In this case, the exit (end of the context switch) is
 437  * in architecture-specific code, and so doesn't need a generic
 438  * definition.
 439  */
 440 #ifndef __HAVE_ARCH_START_CONTEXT_SWITCH
 441 #define arch_start_context_switch(prev) do {} while (0)
 442 #endif
 443
 444 #ifndef CONFIG_HAVE_ARCH_SOFT_DIRTY
 445 static inline int pte_soft_dirty(pte_t pte)
 446 {
 447         return 0;
 448 }
 449
 450 static inline int pmd_soft_dirty(pmd_t pmd)
 451 {
 452         return 0;
 453 }
 454
 455 static inline pte_t pte_mksoft_dirty(pte_t pte)
 456 {
 457         return pte;
 458 }
 459
 460 static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
 461 {
 462         return pmd;
 463 }
 464
 465 static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
 466 {
 467         return pte;
 468 }
 469
 470 static inline int pte_swp_soft_dirty(pte_t pte)
 471 {
 472         return 0;
 473 }
 474
 475 static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 476 {
 477         return pte;
 478 }
 479 #endif
 480
 481 #ifndef __HAVE_PFNMAP_TRACKING
 482 /*
 483  * Interfaces that can be used by architecture code to keep track of
 484  * memory type of pfn mappings specified by the remap_pfn_range,
 485  * vm_insert_pfn.
 486  */
 487
 488 /*
 489  * track_pfn_remap is called when a _new_ pfn mapping is being established
 490  * by remap_pfn_range() for physical range indicated by pfn and size.
 491  */
 492 static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 493                                   unsigned long pfn, unsigned long addr,
 494                                   unsigned long size)
 495 {
 496         return 0;
 497 }
 498
 499 /*
 500  * track_pfn_insert is called when a _new_ single pfn is established
 501  * by vm_insert_pfn().
 502  */
 503 static inline int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 504                                    unsigned long pfn)
 505 {
 506         return 0;
 507 }
 508
 509 /*
 510  * track_pfn_copy is called when vma that is covering the pfnmap gets
 511  * copied through copy_page_range().
 512  */
 513 static inline int track_pfn_copy(struct vm_area_struct *vma)
 514 {
 515         return 0;
 516 }
 517
 518 /*
 519  * untrack_pfn_vma is called while unmapping a pfnmap for a region.
 520  * untrack can be called for a specific region indicated by pfn and size or
 521  * can be for the entire vma (in which case pfn, size are zero).
 522  */
 523 static inline void untrack_pfn(struct vm_area_struct *vma,
 524                                unsigned long pfn, unsigned long size)
 525 {
 526 }
 527 #else
 528 extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 529                            unsigned long pfn, unsigned long addr,
 530                            unsigned long size);
 531 extern int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 532                             unsigned long pfn);
 533 extern int track_pfn_copy(struct vm_area_struct *vma);
 534 extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 535                         unsigned long size);
 536 #endif
 537
 538 #ifdef __HAVE_COLOR_ZERO_PAGE
 539 static inline int is_zero_pfn(unsigned long pfn)
 540 {
 541         extern unsigned long zero_pfn;
 542         unsigned long offset_from_zero_pfn = pfn - zero_pfn;
 543         return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
 544 }
 545
 546 #define my_zero_pfn(addr)       page_to_pfn(ZERO_PAGE(addr))
 547
 548 #else
 549 static inline int is_zero_pfn(unsigned long pfn)
 550 {
 551         extern unsigned long zero_pfn;
 552         return pfn == zero_pfn;
 553 }
 554
 555 static inline unsigned long my_zero_pfn(unsigned long addr)
 556 {
 557         extern unsigned long zero_pfn;
 558         return zero_pfn;
 559 }
 560 #endif
 561
 562 #ifdef CONFIG_MMU
 563
 564 #ifndef CONFIG_TRANSPARENT_HUGEPAGE
 565 static inline int pmd_trans_huge(pmd_t pmd)
 566 {
 567         return 0;
 568 }
 569 static inline int pmd_trans_splitting(pmd_t pmd)
 570 {
 571         return 0;
 572 }
 573 #ifndef __HAVE_ARCH_PMD_WRITE
 574 static inline int pmd_write(pmd_t pmd)
 575 {
 576         BUG();
 577         return 0;
 578 }
 579 #endif /* __HAVE_ARCH_PMD_WRITE */
 580 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 581
 582 #ifndef pmd_read_atomic
 583 static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
 584 {
 585         /*
 586          * Depend on compiler for an atomic pmd read. NOTE: this is
 587          * only going to work, if the pmdval_t isn't larger than
 588          * an unsigned long.
 589          */
 590         return *pmdp;
 591 }
 592 #endif
 593
 594 #ifndef pmd_move_must_withdraw
 595 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
 596                                          spinlock_t *old_pmd_ptl)
 597 {
 598         /*
 599          * With split pmd lock we also need to move preallocated
 600          * PTE page table if new_pmd is on different PMD page table.
 601          */
 602         return new_pmd_ptl != old_pmd_ptl;
 603 }
 604 #endif
 605
 606 /*
 607  * This function is meant to be used by sites walking pagetables with
 608  * the mmap_sem hold in read mode to protect against MADV_DONTNEED and
 609  * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd
 610  * into a null pmd and the transhuge page fault can convert a null pmd
 611  * into an hugepmd or into a regular pmd (if the hugepage allocation
 612  * fails). While holding the mmap_sem in read mode the pmd becomes
 613  * stable and stops changing under us only if it's not null and not a
 614  * transhuge pmd. When those races occurs and this function makes a
 615  * difference vs the standard pmd_none_or_clear_bad, the result is
 616  * undefined so behaving like if the pmd was none is safe (because it
 617  * can return none anyway). The compiler level barrier() is critically
 618  * important to compute the two checks atomically on the same pmdval.
 619  *
 620  * For 32bit kernels with a 64bit large pmd_t this automatically takes
 621  * care of reading the pmd atomically to avoid SMP race conditions
 622  * against pmd_populate() when the mmap_sem is hold for reading by the
 623  * caller (a special atomic read not done by "gcc" as in the generic
 624  * version above, is also needed when THP is disabled because the page
 625  * fault can populate the pmd from under us).
 626  */
 627 static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
 628 {
 629         pmd_t pmdval = pmd_read_atomic(pmd);
 630         /*
 631          * The barrier will stabilize the pmdval in a register or on
 632          * the stack so that it will stop changing under the code.
 633          *
 634          * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE,
 635          * pmd_read_atomic is allowed to return a not atomic pmdval
 636          * (for example pointing to an hugepage that has never been
 637          * mapped in the pmd). The below checks will only care about
 638          * the low part of the pmd with 32bit PAE x86 anyway, with the
 639          * exception of pmd_none(). So the important thing is that if
 640          * the low part of the pmd is found null, the high part will
 641          * be also null or the pmd_none() check below would be
 642          * confused.
 643          */
 644 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 645         barrier();
 646 #endif
 647         if (pmd_none(pmdval) || pmd_trans_huge(pmdval))
 648                 return 1;
 649         if (unlikely(pmd_bad(pmdval))) {
 650                 pmd_clear_bad(pmd);
 651                 return 1;
 652         }
 653         return 0;
 654 }
 655
 656 /*
 657  * This is a noop if Transparent Hugepage Support is not built into
 658  * the kernel. Otherwise it is equivalent to
 659  * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in
 660  * places that already verified the pmd is not none and they want to
 661  * walk ptes while holding the mmap sem in read mode (write mode don't
 662  * need this). If THP is not enabled, the pmd can't go away under the
 663  * code even if MADV_DONTNEED runs, but if THP is enabled we need to
 664  * run a pmd_trans_unstable before walking the ptes after
 665  * split_huge_page_pmd returns (because it may have run when the pmd
 666  * become null, but then a page fault can map in a THP and not a
 667  * regular page).
 668  */
 669 static inline int pmd_trans_unstable(pmd_t *pmd)
 670 {
 671 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 672         return pmd_none_or_trans_huge_or_clear_bad(pmd);
 673 #else
 674         return 0;
 675 #endif
 676 }
 677
 678 #ifndef CONFIG_NUMA_BALANCING
 679 /*
 680  * Technically a PTE can be PROTNONE even when not doing NUMA balancing but
 681  * the only case the kernel cares is for NUMA balancing and is only ever set
 682  * when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked
 683  * _PAGE_PROTNONE so by by default, implement the helper as "always no". It
 684  * is the responsibility of the caller to distinguish between PROT_NONE
 685  * protections and NUMA hinting fault protections.
 686  */
 687 static inline int pte_protnone(pte_t pte)
 688 {
 689         return 0;
 690 }
 691
 692 static inline int pmd_protnone(pmd_t pmd)
 693 {
 694         return 0;
 695 }
 696 #endif /* CONFIG_NUMA_BALANCING */
 697
 698 #endif /* CONFIG_MMU */
 699
 700 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
 701 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
 702 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
 703 int pud_clear_huge(pud_t *pud);
 704 int pmd_clear_huge(pmd_t *pmd);
 705 #else   /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
 706 static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 707 {
 708         return 0;
 709 }
 710 static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 711 {
 712         return 0;
 713 }
 714 static inline int pud_clear_huge(pud_t *pud)
 715 {
 716         return 0;
 717 }
 718 static inline int pmd_clear_huge(pmd_t *pmd)
 719 {
 720         return 0;
 721 }
 722 #endif  /* CONFIG_HAVE_ARCH_HUGE_VMAP */
 723
 724 #endif /* !__ASSEMBLY__ */
 725
 726 #ifndef io_remap_pfn_range
 727 #define io_remap_pfn_range remap_pfn_range
 728 #endif
 729
 730 #endif /* _ASM_GENERIC_PGTABLE_H */