mm/highmem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * High memory handling common code and variables.
   4  *
   5  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
   6  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
   7  *
   8  *
   9  * Redesigned the x86 32-bit VM architecture to deal with
  10  * 64-bit physical space. With current x86 CPUs this
  11  * means up to 64 Gigabytes physical RAM.
  12  *
  13  * Rewrote high memory support to move the page cache into
  14  * high memory. Implemented permanent (schedulable) kmaps
  15  * based on Linus' idea.
  16  *
  17  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  18  */
  19
  20 #include <linux/mm.h>
  21 #include <linux/export.h>
  22 #include <linux/swap.h>
  23 #include <linux/bio.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/mempool.h>
  26 #include <linux/init.h>
  27 #include <linux/hash.h>
  28 #include <linux/highmem.h>
  29 #include <linux/kgdb.h>
  30 #include <asm/tlbflush.h>
  31 #include <linux/vmalloc.h>
  32
  33 #ifdef CONFIG_KMAP_LOCAL
  34 static inline int kmap_local_calc_idx(int idx)
  35 {
  36         return idx + KM_MAX_IDX * smp_processor_id();
  37 }
  38
  39 #ifndef arch_kmap_local_map_idx
  40 #define arch_kmap_local_map_idx(idx, pfn)       kmap_local_calc_idx(idx)
  41 #endif
  42 #endif /* CONFIG_KMAP_LOCAL */
  43
  44 /*
  45  * Virtual_count is not a pure "count".
  46  *  0 means that it is not mapped, and has not been mapped
  47  *    since a TLB flush - it is usable.
  48  *  1 means that there are no users, but it has been mapped
  49  *    since the last TLB flush - so we can't use it.
  50  *  n means that there are (n-1) current users of it.
  51  */
  52 #ifdef CONFIG_HIGHMEM
  53
  54 /*
  55  * Architecture with aliasing data cache may define the following family of
  56  * helper functions in its asm/highmem.h to control cache color of virtual
  57  * addresses where physical memory pages are mapped by kmap.
  58  */
  59 #ifndef get_pkmap_color
  60
  61 /*
  62  * Determine color of virtual address where the page should be mapped.
  63  */
  64 static inline unsigned int get_pkmap_color(struct page *page)
  65 {
  66         return 0;
  67 }
  68 #define get_pkmap_color get_pkmap_color
  69
  70 /*
  71  * Get next index for mapping inside PKMAP region for page with given color.
  72  */
  73 static inline unsigned int get_next_pkmap_nr(unsigned int color)
  74 {
  75         static unsigned int last_pkmap_nr;
  76
  77         last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
  78         return last_pkmap_nr;
  79 }
  80
  81 /*
  82  * Determine if page index inside PKMAP region (pkmap_nr) of given color
  83  * has wrapped around PKMAP region end. When this happens an attempt to
  84  * flush all unused PKMAP slots is made.
  85  */
  86 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
  87 {
  88         return pkmap_nr == 0;
  89 }
  90
  91 /*
  92  * Get the number of PKMAP entries of the given color. If no free slot is
  93  * found after checking that many entries, kmap will sleep waiting for
  94  * someone to call kunmap and free PKMAP slot.
  95  */
  96 static inline int get_pkmap_entries_count(unsigned int color)
  97 {
  98         return LAST_PKMAP;
  99 }
 100
 101 /*
 102  * Get head of a wait queue for PKMAP entries of the given color.
 103  * Wait queues for different mapping colors should be independent to avoid
 104  * unnecessary wakeups caused by freeing of slots of other colors.
 105  */
 106 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
 107 {
 108         static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
 109
 110         return &pkmap_map_wait;
 111 }
 112 #endif
 113
 114 atomic_long_t _totalhigh_pages __read_mostly;
 115 EXPORT_SYMBOL(_totalhigh_pages);
 116
 117 unsigned int __nr_free_highpages(void)
 118 {
 119         struct zone *zone;
 120         unsigned int pages = 0;
 121
 122         for_each_populated_zone(zone) {
 123                 if (is_highmem(zone))
 124                         pages += zone_page_state(zone, NR_FREE_PAGES);
 125         }
 126
 127         return pages;
 128 }
 129
 130 static int pkmap_count[LAST_PKMAP];
 131 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
 132
 133 pte_t *pkmap_page_table;
 134
 135 /*
 136  * Most architectures have no use for kmap_high_get(), so let's abstract
 137  * the disabling of IRQ out of the locking in that case to save on a
 138  * potential useless overhead.
 139  */
 140 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 141 #define lock_kmap()             spin_lock_irq(&kmap_lock)
 142 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
 143 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
 144 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
 145 #else
 146 #define lock_kmap()             spin_lock(&kmap_lock)
 147 #define unlock_kmap()           spin_unlock(&kmap_lock)
 148 #define lock_kmap_any(flags)    \
 149                 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
 150 #define unlock_kmap_any(flags)  \
 151                 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
 152 #endif
 153
 154 struct page *__kmap_to_page(void *vaddr)
 155 {
 156         unsigned long base = (unsigned long) vaddr & PAGE_MASK;
 157         struct kmap_ctrl *kctrl = &current->kmap_ctrl;
 158         unsigned long addr = (unsigned long)vaddr;
 159         int i;
 160
 161         /* kmap() mappings */
 162         if (WARN_ON_ONCE(addr >= PKMAP_ADDR(0) &&
 163                          addr < PKMAP_ADDR(LAST_PKMAP)))
 164                 return pte_page(pkmap_page_table[PKMAP_NR(addr)]);
 165
 166         /* kmap_local_page() mappings */
 167         if (WARN_ON_ONCE(base >= __fix_to_virt(FIX_KMAP_END) &&
 168                          base < __fix_to_virt(FIX_KMAP_BEGIN))) {
 169                 for (i = 0; i < kctrl->idx; i++) {
 170                         unsigned long base_addr;
 171                         int idx;
 172
 173                         idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 174                         base_addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 175
 176                         if (base_addr == base)
 177                                 return pte_page(kctrl->pteval[i]);
 178                 }
 179         }
 180
 181         return virt_to_page(vaddr);
 182 }
 183 EXPORT_SYMBOL(__kmap_to_page);
 184
 185 static void flush_all_zero_pkmaps(void)
 186 {
 187         int i;
 188         int need_flush = 0;
 189
 190         flush_cache_kmaps();
 191
 192         for (i = 0; i < LAST_PKMAP; i++) {
 193                 struct page *page;
 194
 195                 /*
 196                  * zero means we don't have anything to do,
 197                  * >1 means that it is still in use. Only
 198                  * a count of 1 means that it is free but
 199                  * needs to be unmapped
 200                  */
 201                 if (pkmap_count[i] != 1)
 202                         continue;
 203                 pkmap_count[i] = 0;
 204
 205                 /* sanity check */
 206                 BUG_ON(pte_none(pkmap_page_table[i]));
 207
 208                 /*
 209                  * Don't need an atomic fetch-and-clear op here;
 210                  * no-one has the page mapped, and cannot get at
 211                  * its virtual address (and hence PTE) without first
 212                  * getting the kmap_lock (which is held here).
 213                  * So no dangers, even with speculative execution.
 214                  */
 215                 page = pte_page(pkmap_page_table[i]);
 216                 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
 217
 218                 set_page_address(page, NULL);
 219                 need_flush = 1;
 220         }
 221         if (need_flush)
 222                 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 223 }
 224
 225 void __kmap_flush_unused(void)
 226 {
 227         lock_kmap();
 228         flush_all_zero_pkmaps();
 229         unlock_kmap();
 230 }
 231
 232 static inline unsigned long map_new_virtual(struct page *page)
 233 {
 234         unsigned long vaddr;
 235         int count;
 236         unsigned int last_pkmap_nr;
 237         unsigned int color = get_pkmap_color(page);
 238
 239 start:
 240         count = get_pkmap_entries_count(color);
 241         /* Find an empty entry */
 242         for (;;) {
 243                 last_pkmap_nr = get_next_pkmap_nr(color);
 244                 if (no_more_pkmaps(last_pkmap_nr, color)) {
 245                         flush_all_zero_pkmaps();
 246                         count = get_pkmap_entries_count(color);
 247                 }
 248                 if (!pkmap_count[last_pkmap_nr])
 249                         break;  /* Found a usable entry */
 250                 if (--count)
 251                         continue;
 252
 253                 /*
 254                  * Sleep for somebody else to unmap their entries
 255                  */
 256                 {
 257                         DECLARE_WAITQUEUE(wait, current);
 258                         wait_queue_head_t *pkmap_map_wait =
 259                                 get_pkmap_wait_queue_head(color);
 260
 261                         __set_current_state(TASK_UNINTERRUPTIBLE);
 262                         add_wait_queue(pkmap_map_wait, &wait);
 263                         unlock_kmap();
 264                         schedule();
 265                         remove_wait_queue(pkmap_map_wait, &wait);
 266                         lock_kmap();
 267
 268                         /* Somebody else might have mapped it while we slept */
 269                         if (page_address(page))
 270                                 return (unsigned long)page_address(page);
 271
 272                         /* Re-start */
 273                         goto start;
 274                 }
 275         }
 276         vaddr = PKMAP_ADDR(last_pkmap_nr);
 277         set_pte_at(&init_mm, vaddr,
 278                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 279
 280         pkmap_count[last_pkmap_nr] = 1;
 281         set_page_address(page, (void *)vaddr);
 282
 283         return vaddr;
 284 }
 285
 286 /**
 287  * kmap_high - map a highmem page into memory
 288  * @page: &struct page to map
 289  *
 290  * Returns the page's virtual memory address.
 291  *
 292  * We cannot call this from interrupts, as it may block.
 293  */
 294 void *kmap_high(struct page *page)
 295 {
 296         unsigned long vaddr;
 297
 298         /*
 299          * For highmem pages, we can't trust "virtual" until
 300          * after we have the lock.
 301          */
 302         lock_kmap();
 303         vaddr = (unsigned long)page_address(page);
 304         if (!vaddr)
 305                 vaddr = map_new_virtual(page);
 306         pkmap_count[PKMAP_NR(vaddr)]++;
 307         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
 308         unlock_kmap();
 309         return (void *) vaddr;
 310 }
 311 EXPORT_SYMBOL(kmap_high);
 312
 313 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 314 /**
 315  * kmap_high_get - pin a highmem page into memory
 316  * @page: &struct page to pin
 317  *
 318  * Returns the page's current virtual memory address, or NULL if no mapping
 319  * exists.  If and only if a non null address is returned then a
 320  * matching call to kunmap_high() is necessary.
 321  *
 322  * This can be called from any context.
 323  */
 324 void *kmap_high_get(struct page *page)
 325 {
 326         unsigned long vaddr, flags;
 327
 328         lock_kmap_any(flags);
 329         vaddr = (unsigned long)page_address(page);
 330         if (vaddr) {
 331                 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
 332                 pkmap_count[PKMAP_NR(vaddr)]++;
 333         }
 334         unlock_kmap_any(flags);
 335         return (void *) vaddr;
 336 }
 337 #endif
 338
 339 /**
 340  * kunmap_high - unmap a highmem page into memory
 341  * @page: &struct page to unmap
 342  *
 343  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
 344  * only from user context.
 345  */
 346 void kunmap_high(struct page *page)
 347 {
 348         unsigned long vaddr;
 349         unsigned long nr;
 350         unsigned long flags;
 351         int need_wakeup;
 352         unsigned int color = get_pkmap_color(page);
 353         wait_queue_head_t *pkmap_map_wait;
 354
 355         lock_kmap_any(flags);
 356         vaddr = (unsigned long)page_address(page);
 357         BUG_ON(!vaddr);
 358         nr = PKMAP_NR(vaddr);
 359
 360         /*
 361          * A count must never go down to zero
 362          * without a TLB flush!
 363          */
 364         need_wakeup = 0;
 365         switch (--pkmap_count[nr]) {
 366         case 0:
 367                 BUG();
 368         case 1:
 369                 /*
 370                  * Avoid an unnecessary wake_up() function call.
 371                  * The common case is pkmap_count[] == 1, but
 372                  * no waiters.
 373                  * The tasks queued in the wait-queue are guarded
 374                  * by both the lock in the wait-queue-head and by
 375                  * the kmap_lock.  As the kmap_lock is held here,
 376                  * no need for the wait-queue-head's lock.  Simply
 377                  * test if the queue is empty.
 378                  */
 379                 pkmap_map_wait = get_pkmap_wait_queue_head(color);
 380                 need_wakeup = waitqueue_active(pkmap_map_wait);
 381         }
 382         unlock_kmap_any(flags);
 383
 384         /* do wake-up, if needed, race-free outside of the spin lock */
 385         if (need_wakeup)
 386                 wake_up(pkmap_map_wait);
 387 }
 388 EXPORT_SYMBOL(kunmap_high);
 389
 390 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 391                 unsigned start2, unsigned end2)
 392 {
 393         unsigned int i;
 394
 395         BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 396
 397         if (start1 >= end1)
 398                 start1 = end1 = 0;
 399         if (start2 >= end2)
 400                 start2 = end2 = 0;
 401
 402         for (i = 0; i < compound_nr(page); i++) {
 403                 void *kaddr = NULL;
 404
 405                 if (start1 >= PAGE_SIZE) {
 406                         start1 -= PAGE_SIZE;
 407                         end1 -= PAGE_SIZE;
 408                 } else {
 409                         unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
 410
 411                         if (end1 > start1) {
 412                                 kaddr = kmap_local_page(page + i);
 413                                 memset(kaddr + start1, 0, this_end - start1);
 414                         }
 415                         end1 -= this_end;
 416                         start1 = 0;
 417                 }
 418
 419                 if (start2 >= PAGE_SIZE) {
 420                         start2 -= PAGE_SIZE;
 421                         end2 -= PAGE_SIZE;
 422                 } else {
 423                         unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
 424
 425                         if (end2 > start2) {
 426                                 if (!kaddr)
 427                                         kaddr = kmap_local_page(page + i);
 428                                 memset(kaddr + start2, 0, this_end - start2);
 429                         }
 430                         end2 -= this_end;
 431                         start2 = 0;
 432                 }
 433
 434                 if (kaddr) {
 435                         kunmap_local(kaddr);
 436                         flush_dcache_page(page + i);
 437                 }
 438
 439                 if (!end1 && !end2)
 440                         break;
 441         }
 442
 443         BUG_ON((start1 | start2 | end1 | end2) != 0);
 444 }
 445 EXPORT_SYMBOL(zero_user_segments);
 446 #endif /* CONFIG_HIGHMEM */
 447
 448 #ifdef CONFIG_KMAP_LOCAL
 449
 450 #include <asm/kmap_size.h>
 451
 452 /*
 453  * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
 454  * slot is unused which acts as a guard page
 455  */
 456 #ifdef CONFIG_DEBUG_KMAP_LOCAL
 457 # define KM_INCR        2
 458 #else
 459 # define KM_INCR        1
 460 #endif
 461
 462 static inline int kmap_local_idx_push(void)
 463 {
 464         WARN_ON_ONCE(in_hardirq() && !irqs_disabled());
 465         current->kmap_ctrl.idx += KM_INCR;
 466         BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX);
 467         return current->kmap_ctrl.idx - 1;
 468 }
 469
 470 static inline int kmap_local_idx(void)
 471 {
 472         return current->kmap_ctrl.idx - 1;
 473 }
 474
 475 static inline void kmap_local_idx_pop(void)
 476 {
 477         current->kmap_ctrl.idx -= KM_INCR;
 478         BUG_ON(current->kmap_ctrl.idx < 0);
 479 }
 480
 481 #ifndef arch_kmap_local_post_map
 482 # define arch_kmap_local_post_map(vaddr, pteval)        do { } while (0)
 483 #endif
 484
 485 #ifndef arch_kmap_local_pre_unmap
 486 # define arch_kmap_local_pre_unmap(vaddr)               do { } while (0)
 487 #endif
 488
 489 #ifndef arch_kmap_local_post_unmap
 490 # define arch_kmap_local_post_unmap(vaddr)              do { } while (0)
 491 #endif
 492
 493 #ifndef arch_kmap_local_unmap_idx
 494 #define arch_kmap_local_unmap_idx(idx, vaddr)   kmap_local_calc_idx(idx)
 495 #endif
 496
 497 #ifndef arch_kmap_local_high_get
 498 static inline void *arch_kmap_local_high_get(struct page *page)
 499 {
 500         return NULL;
 501 }
 502 #endif
 503
 504 #ifndef arch_kmap_local_set_pte
 505 #define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev)  \
 506         set_pte_at(mm, vaddr, ptep, ptev)
 507 #endif
 508
 509 /* Unmap a local mapping which was obtained by kmap_high_get() */
 510 static inline bool kmap_high_unmap_local(unsigned long vaddr)
 511 {
 512 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 513         if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
 514                 kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
 515                 return true;
 516         }
 517 #endif
 518         return false;
 519 }
 520
 521 static pte_t *__kmap_pte;
 522
 523 static pte_t *kmap_get_pte(unsigned long vaddr, int idx)
 524 {
 525         if (IS_ENABLED(CONFIG_KMAP_LOCAL_NON_LINEAR_PTE_ARRAY))
 526                 /*
 527                  * Set by the arch if __kmap_pte[-idx] does not produce
 528                  * the correct entry.
 529                  */
 530                 return virt_to_kpte(vaddr);
 531         if (!__kmap_pte)
 532                 __kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 533         return &__kmap_pte[-idx];
 534 }
 535
 536 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 537 {
 538         pte_t pteval, *kmap_pte;
 539         unsigned long vaddr;
 540         int idx;
 541
 542         /*
 543          * Disable migration so resulting virtual address is stable
 544          * across preemption.
 545          */
 546         migrate_disable();
 547         preempt_disable();
 548         idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
 549         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 550         kmap_pte = kmap_get_pte(vaddr, idx);
 551         BUG_ON(!pte_none(*kmap_pte));
 552         pteval = pfn_pte(pfn, prot);
 553         arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte, pteval);
 554         arch_kmap_local_post_map(vaddr, pteval);
 555         current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
 556         preempt_enable();
 557
 558         return (void *)vaddr;
 559 }
 560 EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
 561
 562 void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
 563 {
 564         void *kmap;
 565
 566         /*
 567          * To broaden the usage of the actual kmap_local() machinery always map
 568          * pages when debugging is enabled and the architecture has no problems
 569          * with alias mappings.
 570          */
 571         if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
 572                 return page_address(page);
 573
 574         /* Try kmap_high_get() if architecture has it enabled */
 575         kmap = arch_kmap_local_high_get(page);
 576         if (kmap)
 577                 return kmap;
 578
 579         return __kmap_local_pfn_prot(page_to_pfn(page), prot);
 580 }
 581 EXPORT_SYMBOL(__kmap_local_page_prot);
 582
 583 void kunmap_local_indexed(const void *vaddr)
 584 {
 585         unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
 586         pte_t *kmap_pte;
 587         int idx;
 588
 589         if (addr < __fix_to_virt(FIX_KMAP_END) ||
 590             addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
 591                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
 592                         /* This _should_ never happen! See above. */
 593                         WARN_ON_ONCE(1);
 594                         return;
 595                 }
 596                 /*
 597                  * Handle mappings which were obtained by kmap_high_get()
 598                  * first as the virtual address of such mappings is below
 599                  * PAGE_OFFSET. Warn for all other addresses which are in
 600                  * the user space part of the virtual address space.
 601                  */
 602                 if (!kmap_high_unmap_local(addr))
 603                         WARN_ON_ONCE(addr < PAGE_OFFSET);
 604                 return;
 605         }
 606
 607         preempt_disable();
 608         idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
 609         WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 610
 611         kmap_pte = kmap_get_pte(addr, idx);
 612         arch_kmap_local_pre_unmap(addr);
 613         pte_clear(&init_mm, addr, kmap_pte);
 614         arch_kmap_local_post_unmap(addr);
 615         current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
 616         kmap_local_idx_pop();
 617         preempt_enable();
 618         migrate_enable();
 619 }
 620 EXPORT_SYMBOL(kunmap_local_indexed);
 621
 622 /*
 623  * Invoked before switch_to(). This is safe even when during or after
 624  * clearing the maps an interrupt which needs a kmap_local happens because
 625  * the task::kmap_ctrl.idx is not modified by the unmapping code so a
 626  * nested kmap_local will use the next unused index and restore the index
 627  * on unmap. The already cleared kmaps of the outgoing task are irrelevant
 628  * because the interrupt context does not know about them. The same applies
 629  * when scheduling back in for an interrupt which happens before the
 630  * restore is complete.
 631  */
 632 void __kmap_local_sched_out(void)
 633 {
 634         struct task_struct *tsk = current;
 635         pte_t *kmap_pte;
 636         int i;
 637
 638         /* Clear kmaps */
 639         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 640                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 641                 unsigned long addr;
 642                 int idx;
 643
 644                 /* With debug all even slots are unmapped and act as guard */
 645                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 646                         WARN_ON_ONCE(pte_val(pteval) != 0);
 647                         continue;
 648                 }
 649                 if (WARN_ON_ONCE(pte_none(pteval)))
 650                         continue;
 651
 652                 /*
 653                  * This is a horrible hack for XTENSA to calculate the
 654                  * coloured PTE index. Uses the PFN encoded into the pteval
 655                  * and the map index calculation because the actual mapped
 656                  * virtual address is not stored in task::kmap_ctrl.
 657                  * For any sane architecture this is optimized out.
 658                  */
 659                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 660
 661                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 662                 kmap_pte = kmap_get_pte(addr, idx);
 663                 arch_kmap_local_pre_unmap(addr);
 664                 pte_clear(&init_mm, addr, kmap_pte);
 665                 arch_kmap_local_post_unmap(addr);
 666         }
 667 }
 668
 669 void __kmap_local_sched_in(void)
 670 {
 671         struct task_struct *tsk = current;
 672         pte_t *kmap_pte;
 673         int i;
 674
 675         /* Restore kmaps */
 676         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 677                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 678                 unsigned long addr;
 679                 int idx;
 680
 681                 /* With debug all even slots are unmapped and act as guard */
 682                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 683                         WARN_ON_ONCE(pte_val(pteval) != 0);
 684                         continue;
 685                 }
 686                 if (WARN_ON_ONCE(pte_none(pteval)))
 687                         continue;
 688
 689                 /* See comment in __kmap_local_sched_out() */
 690                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 691                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 692                 kmap_pte = kmap_get_pte(addr, idx);
 693                 set_pte_at(&init_mm, addr, kmap_pte, pteval);
 694                 arch_kmap_local_post_map(addr, pteval);
 695         }
 696 }
 697
 698 void kmap_local_fork(struct task_struct *tsk)
 699 {
 700         if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
 701                 memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
 702 }
 703
 704 #endif
 705
 706 #if defined(HASHED_PAGE_VIRTUAL)
 707
 708 #define PA_HASH_ORDER   7
 709
 710 /*
 711  * Describes one page->virtual association
 712  */
 713 struct page_address_map {
 714         struct page *page;
 715         void *virtual;
 716         struct list_head list;
 717 };
 718
 719 static struct page_address_map page_address_maps[LAST_PKMAP];
 720
 721 /*
 722  * Hash table bucket
 723  */
 724 static struct page_address_slot {
 725         struct list_head lh;                    /* List of page_address_maps */
 726         spinlock_t lock;                        /* Protect this bucket's list */
 727 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 728
 729 static struct page_address_slot *page_slot(const struct page *page)
 730 {
 731         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 732 }
 733
 734 /**
 735  * page_address - get the mapped virtual address of a page
 736  * @page: &struct page to get the virtual address of
 737  *
 738  * Returns the page's virtual address.
 739  */
 740 void *page_address(const struct page *page)
 741 {
 742         unsigned long flags;
 743         void *ret;
 744         struct page_address_slot *pas;
 745
 746         if (!PageHighMem(page))
 747                 return lowmem_page_address(page);
 748
 749         pas = page_slot(page);
 750         ret = NULL;
 751         spin_lock_irqsave(&pas->lock, flags);
 752         if (!list_empty(&pas->lh)) {
 753                 struct page_address_map *pam;
 754
 755                 list_for_each_entry(pam, &pas->lh, list) {
 756                         if (pam->page == page) {
 757                                 ret = pam->virtual;
 758                                 break;
 759                         }
 760                 }
 761         }
 762
 763         spin_unlock_irqrestore(&pas->lock, flags);
 764         return ret;
 765 }
 766 EXPORT_SYMBOL(page_address);
 767
 768 /**
 769  * set_page_address - set a page's virtual address
 770  * @page: &struct page to set
 771  * @virtual: virtual address to use
 772  */
 773 void set_page_address(struct page *page, void *virtual)
 774 {
 775         unsigned long flags;
 776         struct page_address_slot *pas;
 777         struct page_address_map *pam;
 778
 779         BUG_ON(!PageHighMem(page));
 780
 781         pas = page_slot(page);
 782         if (virtual) {          /* Add */
 783                 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
 784                 pam->page = page;
 785                 pam->virtual = virtual;
 786
 787                 spin_lock_irqsave(&pas->lock, flags);
 788                 list_add_tail(&pam->list, &pas->lh);
 789                 spin_unlock_irqrestore(&pas->lock, flags);
 790         } else {                /* Remove */
 791                 spin_lock_irqsave(&pas->lock, flags);
 792                 list_for_each_entry(pam, &pas->lh, list) {
 793                         if (pam->page == page) {
 794                                 list_del(&pam->list);
 795                                 break;
 796                         }
 797                 }
 798                 spin_unlock_irqrestore(&pas->lock, flags);
 799         }
 800
 801         return;
 802 }
 803
 804 void __init page_address_init(void)
 805 {
 806         int i;
 807
 808         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 809                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 810                 spin_lock_init(&page_address_htable[i].lock);
 811         }
 812 }
 813
 814 #endif  /* defined(HASHED_PAGE_VIRTUAL) */