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