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(ptep_get(&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                 pte_t ptent;
 195
 196                 /*
 197                  * zero means we don't have anything to do,
 198                  * >1 means that it is still in use. Only
 199                  * a count of 1 means that it is free but
 200                  * needs to be unmapped
 201                  */
 202                 if (pkmap_count[i] != 1)
 203                         continue;
 204                 pkmap_count[i] = 0;
 205
 206                 /* sanity check */
 207                 ptent = ptep_get(&pkmap_page_table[i]);
 208                 BUG_ON(pte_none(ptent));
 209
 210                 /*
 211                  * Don't need an atomic fetch-and-clear op here;
 212                  * no-one has the page mapped, and cannot get at
 213                  * its virtual address (and hence PTE) without first
 214                  * getting the kmap_lock (which is held here).
 215                  * So no dangers, even with speculative execution.
 216                  */
 217                 page = pte_page(ptent);
 218                 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
 219
 220                 set_page_address(page, NULL);
 221                 need_flush = 1;
 222         }
 223         if (need_flush)
 224                 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 225 }
 226
 227 void __kmap_flush_unused(void)
 228 {
 229         lock_kmap();
 230         flush_all_zero_pkmaps();
 231         unlock_kmap();
 232 }
 233
 234 static inline unsigned long map_new_virtual(struct page *page)
 235 {
 236         unsigned long vaddr;
 237         int count;
 238         unsigned int last_pkmap_nr;
 239         unsigned int color = get_pkmap_color(page);
 240
 241 start:
 242         count = get_pkmap_entries_count(color);
 243         /* Find an empty entry */
 244         for (;;) {
 245                 last_pkmap_nr = get_next_pkmap_nr(color);
 246                 if (no_more_pkmaps(last_pkmap_nr, color)) {
 247                         flush_all_zero_pkmaps();
 248                         count = get_pkmap_entries_count(color);
 249                 }
 250                 if (!pkmap_count[last_pkmap_nr])
 251                         break;  /* Found a usable entry */
 252                 if (--count)
 253                         continue;
 254
 255                 /*
 256                  * Sleep for somebody else to unmap their entries
 257                  */
 258                 {
 259                         DECLARE_WAITQUEUE(wait, current);
 260                         wait_queue_head_t *pkmap_map_wait =
 261                                 get_pkmap_wait_queue_head(color);
 262
 263                         __set_current_state(TASK_UNINTERRUPTIBLE);
 264                         add_wait_queue(pkmap_map_wait, &wait);
 265                         unlock_kmap();
 266                         schedule();
 267                         remove_wait_queue(pkmap_map_wait, &wait);
 268                         lock_kmap();
 269
 270                         /* Somebody else might have mapped it while we slept */
 271                         if (page_address(page))
 272                                 return (unsigned long)page_address(page);
 273
 274                         /* Re-start */
 275                         goto start;
 276                 }
 277         }
 278         vaddr = PKMAP_ADDR(last_pkmap_nr);
 279         set_pte_at(&init_mm, vaddr,
 280                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 281
 282         pkmap_count[last_pkmap_nr] = 1;
 283         set_page_address(page, (void *)vaddr);
 284
 285         return vaddr;
 286 }
 287
 288 /**
 289  * kmap_high - map a highmem page into memory
 290  * @page: &struct page to map
 291  *
 292  * Returns the page's virtual memory address.
 293  *
 294  * We cannot call this from interrupts, as it may block.
 295  */
 296 void *kmap_high(struct page *page)
 297 {
 298         unsigned long vaddr;
 299
 300         /*
 301          * For highmem pages, we can't trust "virtual" until
 302          * after we have the lock.
 303          */
 304         lock_kmap();
 305         vaddr = (unsigned long)page_address(page);
 306         if (!vaddr)
 307                 vaddr = map_new_virtual(page);
 308         pkmap_count[PKMAP_NR(vaddr)]++;
 309         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
 310         unlock_kmap();
 311         return (void *) vaddr;
 312 }
 313 EXPORT_SYMBOL(kmap_high);
 314
 315 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 316 /**
 317  * kmap_high_get - pin a highmem page into memory
 318  * @page: &struct page to pin
 319  *
 320  * Returns the page's current virtual memory address, or NULL if no mapping
 321  * exists.  If and only if a non null address is returned then a
 322  * matching call to kunmap_high() is necessary.
 323  *
 324  * This can be called from any context.
 325  */
 326 void *kmap_high_get(struct page *page)
 327 {
 328         unsigned long vaddr, flags;
 329
 330         lock_kmap_any(flags);
 331         vaddr = (unsigned long)page_address(page);
 332         if (vaddr) {
 333                 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
 334                 pkmap_count[PKMAP_NR(vaddr)]++;
 335         }
 336         unlock_kmap_any(flags);
 337         return (void *) vaddr;
 338 }
 339 #endif
 340
 341 /**
 342  * kunmap_high - unmap a highmem page into memory
 343  * @page: &struct page to unmap
 344  *
 345  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
 346  * only from user context.
 347  */
 348 void kunmap_high(struct page *page)
 349 {
 350         unsigned long vaddr;
 351         unsigned long nr;
 352         unsigned long flags;
 353         int need_wakeup;
 354         unsigned int color = get_pkmap_color(page);
 355         wait_queue_head_t *pkmap_map_wait;
 356
 357         lock_kmap_any(flags);
 358         vaddr = (unsigned long)page_address(page);
 359         BUG_ON(!vaddr);
 360         nr = PKMAP_NR(vaddr);
 361
 362         /*
 363          * A count must never go down to zero
 364          * without a TLB flush!
 365          */
 366         need_wakeup = 0;
 367         switch (--pkmap_count[nr]) {
 368         case 0:
 369                 BUG();
 370         case 1:
 371                 /*
 372                  * Avoid an unnecessary wake_up() function call.
 373                  * The common case is pkmap_count[] == 1, but
 374                  * no waiters.
 375                  * The tasks queued in the wait-queue are guarded
 376                  * by both the lock in the wait-queue-head and by
 377                  * the kmap_lock.  As the kmap_lock is held here,
 378                  * no need for the wait-queue-head's lock.  Simply
 379                  * test if the queue is empty.
 380                  */
 381                 pkmap_map_wait = get_pkmap_wait_queue_head(color);
 382                 need_wakeup = waitqueue_active(pkmap_map_wait);
 383         }
 384         unlock_kmap_any(flags);
 385
 386         /* do wake-up, if needed, race-free outside of the spin lock */
 387         if (need_wakeup)
 388                 wake_up(pkmap_map_wait);
 389 }
 390 EXPORT_SYMBOL(kunmap_high);
 391
 392 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 393                 unsigned start2, unsigned end2)
 394 {
 395         unsigned int i;
 396
 397         BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 398
 399         if (start1 >= end1)
 400                 start1 = end1 = 0;
 401         if (start2 >= end2)
 402                 start2 = end2 = 0;
 403
 404         for (i = 0; i < compound_nr(page); i++) {
 405                 void *kaddr = NULL;
 406
 407                 if (start1 >= PAGE_SIZE) {
 408                         start1 -= PAGE_SIZE;
 409                         end1 -= PAGE_SIZE;
 410                 } else {
 411                         unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
 412
 413                         if (end1 > start1) {
 414                                 kaddr = kmap_local_page(page + i);
 415                                 memset(kaddr + start1, 0, this_end - start1);
 416                         }
 417                         end1 -= this_end;
 418                         start1 = 0;
 419                 }
 420
 421                 if (start2 >= PAGE_SIZE) {
 422                         start2 -= PAGE_SIZE;
 423                         end2 -= PAGE_SIZE;
 424                 } else {
 425                         unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
 426
 427                         if (end2 > start2) {
 428                                 if (!kaddr)
 429                                         kaddr = kmap_local_page(page + i);
 430                                 memset(kaddr + start2, 0, this_end - start2);
 431                         }
 432                         end2 -= this_end;
 433                         start2 = 0;
 434                 }
 435
 436                 if (kaddr) {
 437                         kunmap_local(kaddr);
 438                         flush_dcache_page(page + i);
 439                 }
 440
 441                 if (!end1 && !end2)
 442                         break;
 443         }
 444
 445         BUG_ON((start1 | start2 | end1 | end2) != 0);
 446 }
 447 EXPORT_SYMBOL(zero_user_segments);
 448 #endif /* CONFIG_HIGHMEM */
 449
 450 #ifdef CONFIG_KMAP_LOCAL
 451
 452 #include <asm/kmap_size.h>
 453
 454 /*
 455  * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
 456  * slot is unused which acts as a guard page
 457  */
 458 #ifdef CONFIG_DEBUG_KMAP_LOCAL
 459 # define KM_INCR        2
 460 #else
 461 # define KM_INCR        1
 462 #endif
 463
 464 static inline int kmap_local_idx_push(void)
 465 {
 466         WARN_ON_ONCE(in_hardirq() && !irqs_disabled());
 467         current->kmap_ctrl.idx += KM_INCR;
 468         BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX);
 469         return current->kmap_ctrl.idx - 1;
 470 }
 471
 472 static inline int kmap_local_idx(void)
 473 {
 474         return current->kmap_ctrl.idx - 1;
 475 }
 476
 477 static inline void kmap_local_idx_pop(void)
 478 {
 479         current->kmap_ctrl.idx -= KM_INCR;
 480         BUG_ON(current->kmap_ctrl.idx < 0);
 481 }
 482
 483 #ifndef arch_kmap_local_post_map
 484 # define arch_kmap_local_post_map(vaddr, pteval)        do { } while (0)
 485 #endif
 486
 487 #ifndef arch_kmap_local_pre_unmap
 488 # define arch_kmap_local_pre_unmap(vaddr)               do { } while (0)
 489 #endif
 490
 491 #ifndef arch_kmap_local_post_unmap
 492 # define arch_kmap_local_post_unmap(vaddr)              do { } while (0)
 493 #endif
 494
 495 #ifndef arch_kmap_local_unmap_idx
 496 #define arch_kmap_local_unmap_idx(idx, vaddr)   kmap_local_calc_idx(idx)
 497 #endif
 498
 499 #ifndef arch_kmap_local_high_get
 500 static inline void *arch_kmap_local_high_get(struct page *page)
 501 {
 502         return NULL;
 503 }
 504 #endif
 505
 506 #ifndef arch_kmap_local_set_pte
 507 #define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev)  \
 508         set_pte_at(mm, vaddr, ptep, ptev)
 509 #endif
 510
 511 /* Unmap a local mapping which was obtained by kmap_high_get() */
 512 static inline bool kmap_high_unmap_local(unsigned long vaddr)
 513 {
 514 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 515         if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
 516                 kunmap_high(pte_page(ptep_get(&pkmap_page_table[PKMAP_NR(vaddr)])));
 517                 return true;
 518         }
 519 #endif
 520         return false;
 521 }
 522
 523 static pte_t *__kmap_pte;
 524
 525 static pte_t *kmap_get_pte(unsigned long vaddr, int idx)
 526 {
 527         if (IS_ENABLED(CONFIG_KMAP_LOCAL_NON_LINEAR_PTE_ARRAY))
 528                 /*
 529                  * Set by the arch if __kmap_pte[-idx] does not produce
 530                  * the correct entry.
 531                  */
 532                 return virt_to_kpte(vaddr);
 533         if (!__kmap_pte)
 534                 __kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 535         return &__kmap_pte[-idx];
 536 }
 537
 538 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 539 {
 540         pte_t pteval, *kmap_pte;
 541         unsigned long vaddr;
 542         int idx;
 543
 544         /*
 545          * Disable migration so resulting virtual address is stable
 546          * across preemption.
 547          */
 548         migrate_disable();
 549         preempt_disable();
 550         idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
 551         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 552         kmap_pte = kmap_get_pte(vaddr, idx);
 553         BUG_ON(!pte_none(ptep_get(kmap_pte)));
 554         pteval = pfn_pte(pfn, prot);
 555         arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte, pteval);
 556         arch_kmap_local_post_map(vaddr, pteval);
 557         current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
 558         preempt_enable();
 559
 560         return (void *)vaddr;
 561 }
 562 EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
 563
 564 void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
 565 {
 566         void *kmap;
 567
 568         /*
 569          * To broaden the usage of the actual kmap_local() machinery always map
 570          * pages when debugging is enabled and the architecture has no problems
 571          * with alias mappings.
 572          */
 573         if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
 574                 return page_address(page);
 575
 576         /* Try kmap_high_get() if architecture has it enabled */
 577         kmap = arch_kmap_local_high_get(page);
 578         if (kmap)
 579                 return kmap;
 580
 581         return __kmap_local_pfn_prot(page_to_pfn(page), prot);
 582 }
 583 EXPORT_SYMBOL(__kmap_local_page_prot);
 584
 585 void kunmap_local_indexed(const void *vaddr)
 586 {
 587         unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
 588         pte_t *kmap_pte;
 589         int idx;
 590
 591         if (addr < __fix_to_virt(FIX_KMAP_END) ||
 592             addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
 593                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
 594                         /* This _should_ never happen! See above. */
 595                         WARN_ON_ONCE(1);
 596                         return;
 597                 }
 598                 /*
 599                  * Handle mappings which were obtained by kmap_high_get()
 600                  * first as the virtual address of such mappings is below
 601                  * PAGE_OFFSET. Warn for all other addresses which are in
 602                  * the user space part of the virtual address space.
 603                  */
 604                 if (!kmap_high_unmap_local(addr))
 605                         WARN_ON_ONCE(addr < PAGE_OFFSET);
 606                 return;
 607         }
 608
 609         preempt_disable();
 610         idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
 611         WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 612
 613         kmap_pte = kmap_get_pte(addr, idx);
 614         arch_kmap_local_pre_unmap(addr);
 615         pte_clear(&init_mm, addr, kmap_pte);
 616         arch_kmap_local_post_unmap(addr);
 617         current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
 618         kmap_local_idx_pop();
 619         preempt_enable();
 620         migrate_enable();
 621 }
 622 EXPORT_SYMBOL(kunmap_local_indexed);
 623
 624 /*
 625  * Invoked before switch_to(). This is safe even when during or after
 626  * clearing the maps an interrupt which needs a kmap_local happens because
 627  * the task::kmap_ctrl.idx is not modified by the unmapping code so a
 628  * nested kmap_local will use the next unused index and restore the index
 629  * on unmap. The already cleared kmaps of the outgoing task are irrelevant
 630  * because the interrupt context does not know about them. The same applies
 631  * when scheduling back in for an interrupt which happens before the
 632  * restore is complete.
 633  */
 634 void __kmap_local_sched_out(void)
 635 {
 636         struct task_struct *tsk = current;
 637         pte_t *kmap_pte;
 638         int i;
 639
 640         /* Clear kmaps */
 641         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 642                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 643                 unsigned long addr;
 644                 int idx;
 645
 646                 /* With debug all even slots are unmapped and act as guard */
 647                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 648                         WARN_ON_ONCE(pte_val(pteval) != 0);
 649                         continue;
 650                 }
 651                 if (WARN_ON_ONCE(pte_none(pteval)))
 652                         continue;
 653
 654                 /*
 655                  * This is a horrible hack for XTENSA to calculate the
 656                  * coloured PTE index. Uses the PFN encoded into the pteval
 657                  * and the map index calculation because the actual mapped
 658                  * virtual address is not stored in task::kmap_ctrl.
 659                  * For any sane architecture this is optimized out.
 660                  */
 661                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 662
 663                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 664                 kmap_pte = kmap_get_pte(addr, idx);
 665                 arch_kmap_local_pre_unmap(addr);
 666                 pte_clear(&init_mm, addr, kmap_pte);
 667                 arch_kmap_local_post_unmap(addr);
 668         }
 669 }
 670
 671 void __kmap_local_sched_in(void)
 672 {
 673         struct task_struct *tsk = current;
 674         pte_t *kmap_pte;
 675         int i;
 676
 677         /* Restore kmaps */
 678         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 679                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 680                 unsigned long addr;
 681                 int idx;
 682
 683                 /* With debug all even slots are unmapped and act as guard */
 684                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 685                         WARN_ON_ONCE(pte_val(pteval) != 0);
 686                         continue;
 687                 }
 688                 if (WARN_ON_ONCE(pte_none(pteval)))
 689                         continue;
 690
 691                 /* See comment in __kmap_local_sched_out() */
 692                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 693                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 694                 kmap_pte = kmap_get_pte(addr, idx);
 695                 set_pte_at(&init_mm, addr, kmap_pte, pteval);
 696                 arch_kmap_local_post_map(addr, pteval);
 697         }
 698 }
 699
 700 void kmap_local_fork(struct task_struct *tsk)
 701 {
 702         if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
 703                 memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
 704 }
 705
 706 #endif
 707
 708 #if defined(HASHED_PAGE_VIRTUAL)
 709
 710 #define PA_HASH_ORDER   7
 711
 712 /*
 713  * Describes one page->virtual association
 714  */
 715 struct page_address_map {
 716         struct page *page;
 717         void *virtual;
 718         struct list_head list;
 719 };
 720
 721 static struct page_address_map page_address_maps[LAST_PKMAP];
 722
 723 /*
 724  * Hash table bucket
 725  */
 726 static struct page_address_slot {
 727         struct list_head lh;                    /* List of page_address_maps */
 728         spinlock_t lock;                        /* Protect this bucket's list */
 729 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 730
 731 static struct page_address_slot *page_slot(const struct page *page)
 732 {
 733         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 734 }
 735
 736 /**
 737  * page_address - get the mapped virtual address of a page
 738  * @page: &struct page to get the virtual address of
 739  *
 740  * Returns the page's virtual address.
 741  */
 742 void *page_address(const struct page *page)
 743 {
 744         unsigned long flags;
 745         void *ret;
 746         struct page_address_slot *pas;
 747
 748         if (!PageHighMem(page))
 749                 return lowmem_page_address(page);
 750
 751         pas = page_slot(page);
 752         ret = NULL;
 753         spin_lock_irqsave(&pas->lock, flags);
 754         if (!list_empty(&pas->lh)) {
 755                 struct page_address_map *pam;
 756
 757                 list_for_each_entry(pam, &pas->lh, list) {
 758                         if (pam->page == page) {
 759                                 ret = pam->virtual;
 760                                 break;
 761                         }
 762                 }
 763         }
 764
 765         spin_unlock_irqrestore(&pas->lock, flags);
 766         return ret;
 767 }
 768 EXPORT_SYMBOL(page_address);
 769
 770 /**
 771  * set_page_address - set a page's virtual address
 772  * @page: &struct page to set
 773  * @virtual: virtual address to use
 774  */
 775 void set_page_address(struct page *page, void *virtual)
 776 {
 777         unsigned long flags;
 778         struct page_address_slot *pas;
 779         struct page_address_map *pam;
 780
 781         BUG_ON(!PageHighMem(page));
 782
 783         pas = page_slot(page);
 784         if (virtual) {          /* Add */
 785                 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
 786                 pam->page = page;
 787                 pam->virtual = virtual;
 788
 789                 spin_lock_irqsave(&pas->lock, flags);
 790                 list_add_tail(&pam->list, &pas->lh);
 791                 spin_unlock_irqrestore(&pas->lock, flags);
 792         } else {                /* Remove */
 793                 spin_lock_irqsave(&pas->lock, flags);
 794                 list_for_each_entry(pam, &pas->lh, list) {
 795                         if (pam->page == page) {
 796                                 list_del(&pam->list);
 797                                 break;
 798                         }
 799                 }
 800                 spin_unlock_irqrestore(&pas->lock, flags);
 801         }
 802
 803         return;
 804 }
 805
 806 void __init page_address_init(void)
 807 {
 808         int i;
 809
 810         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 811                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 812                 spin_lock_init(&page_address_htable[i].lock);
 813         }
 814 }
 815
 816 #endif  /* defined(HASHED_PAGE_VIRTUAL) */