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/blkdev.h> 27 #include <linux/init.h> 28 #include <linux/hash.h> 29 #include <linux/highmem.h> 30 #include <linux/kgdb.h> 31 #include <asm/tlbflush.h> 32 #include <linux/vmalloc.h> 33 34 /* 35 * Virtual_count is not a pure "count". 36 * 0 means that it is not mapped, and has not been mapped 37 * since a TLB flush - it is usable. 38 * 1 means that there are no users, but it has been mapped 39 * since the last TLB flush - so we can't use it. 40 * n means that there are (n-1) current users of it. 41 */ 42 #ifdef CONFIG_HIGHMEM 43 44 /* 45 * Architecture with aliasing data cache may define the following family of 46 * helper functions in its asm/highmem.h to control cache color of virtual 47 * addresses where physical memory pages are mapped by kmap. 48 */ 49 #ifndef get_pkmap_color 50 51 /* 52 * Determine color of virtual address where the page should be mapped. 53 */ 54 static inline unsigned int get_pkmap_color(struct page *page) 55 { 56 return 0; 57 } 58 #define get_pkmap_color get_pkmap_color 59 60 /* 61 * Get next index for mapping inside PKMAP region for page with given color. 62 */ 63 static inline unsigned int get_next_pkmap_nr(unsigned int color) 64 { 65 static unsigned int last_pkmap_nr; 66 67 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; 68 return last_pkmap_nr; 69 } 70 71 /* 72 * Determine if page index inside PKMAP region (pkmap_nr) of given color 73 * has wrapped around PKMAP region end. When this happens an attempt to 74 * flush all unused PKMAP slots is made. 75 */ 76 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color) 77 { 78 return pkmap_nr == 0; 79 } 80 81 /* 82 * Get the number of PKMAP entries of the given color. If no free slot is 83 * found after checking that many entries, kmap will sleep waiting for 84 * someone to call kunmap and free PKMAP slot. 85 */ 86 static inline int get_pkmap_entries_count(unsigned int color) 87 { 88 return LAST_PKMAP; 89 } 90 91 /* 92 * Get head of a wait queue for PKMAP entries of the given color. 93 * Wait queues for different mapping colors should be independent to avoid 94 * unnecessary wakeups caused by freeing of slots of other colors. 95 */ 96 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color) 97 { 98 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); 99 100 return &pkmap_map_wait; 101 } 102 #endif 103 104 atomic_long_t _totalhigh_pages __read_mostly; 105 EXPORT_SYMBOL(_totalhigh_pages); 106 107 unsigned int __nr_free_highpages (void) 108 { 109 struct zone *zone; 110 unsigned int pages = 0; 111 112 for_each_populated_zone(zone) { 113 if (is_highmem(zone)) 114 pages += zone_page_state(zone, NR_FREE_PAGES); 115 } 116 117 return pages; 118 } 119 120 static int pkmap_count[LAST_PKMAP]; 121 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); 122 123 pte_t * pkmap_page_table; 124 125 /* 126 * Most architectures have no use for kmap_high_get(), so let's abstract 127 * the disabling of IRQ out of the locking in that case to save on a 128 * potential useless overhead. 129 */ 130 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 131 #define lock_kmap() spin_lock_irq(&kmap_lock) 132 #define unlock_kmap() spin_unlock_irq(&kmap_lock) 133 #define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags) 134 #define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags) 135 #else 136 #define lock_kmap() spin_lock(&kmap_lock) 137 #define unlock_kmap() spin_unlock(&kmap_lock) 138 #define lock_kmap_any(flags) \ 139 do { spin_lock(&kmap_lock); (void)(flags); } while (0) 140 #define unlock_kmap_any(flags) \ 141 do { spin_unlock(&kmap_lock); (void)(flags); } while (0) 142 #endif 143 144 struct page *__kmap_to_page(void *vaddr) 145 { 146 unsigned long addr = (unsigned long)vaddr; 147 148 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) { 149 int i = PKMAP_NR(addr); 150 return pte_page(pkmap_page_table[i]); 151 } 152 153 return virt_to_page(addr); 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 } 283 284 EXPORT_SYMBOL(kmap_high); 285 286 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 287 /** 288 * kmap_high_get - pin a highmem page into memory 289 * @page: &struct page to pin 290 * 291 * Returns the page's current virtual memory address, or NULL if no mapping 292 * exists. If and only if a non null address is returned then a 293 * matching call to kunmap_high() is necessary. 294 * 295 * This can be called from any context. 296 */ 297 void *kmap_high_get(struct page *page) 298 { 299 unsigned long vaddr, flags; 300 301 lock_kmap_any(flags); 302 vaddr = (unsigned long)page_address(page); 303 if (vaddr) { 304 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1); 305 pkmap_count[PKMAP_NR(vaddr)]++; 306 } 307 unlock_kmap_any(flags); 308 return (void*) vaddr; 309 } 310 #endif 311 312 /** 313 * kunmap_high - unmap a highmem page into memory 314 * @page: &struct page to unmap 315 * 316 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called 317 * only from user context. 318 */ 319 void kunmap_high(struct page *page) 320 { 321 unsigned long vaddr; 322 unsigned long nr; 323 unsigned long flags; 324 int need_wakeup; 325 unsigned int color = get_pkmap_color(page); 326 wait_queue_head_t *pkmap_map_wait; 327 328 lock_kmap_any(flags); 329 vaddr = (unsigned long)page_address(page); 330 BUG_ON(!vaddr); 331 nr = PKMAP_NR(vaddr); 332 333 /* 334 * A count must never go down to zero 335 * without a TLB flush! 336 */ 337 need_wakeup = 0; 338 switch (--pkmap_count[nr]) { 339 case 0: 340 BUG(); 341 case 1: 342 /* 343 * Avoid an unnecessary wake_up() function call. 344 * The common case is pkmap_count[] == 1, but 345 * no waiters. 346 * The tasks queued in the wait-queue are guarded 347 * by both the lock in the wait-queue-head and by 348 * the kmap_lock. As the kmap_lock is held here, 349 * no need for the wait-queue-head's lock. Simply 350 * test if the queue is empty. 351 */ 352 pkmap_map_wait = get_pkmap_wait_queue_head(color); 353 need_wakeup = waitqueue_active(pkmap_map_wait); 354 } 355 unlock_kmap_any(flags); 356 357 /* do wake-up, if needed, race-free outside of the spin lock */ 358 if (need_wakeup) 359 wake_up(pkmap_map_wait); 360 } 361 EXPORT_SYMBOL(kunmap_high); 362 363 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 364 void zero_user_segments(struct page *page, unsigned start1, unsigned end1, 365 unsigned start2, unsigned end2) 366 { 367 unsigned int i; 368 369 BUG_ON(end1 > page_size(page) || end2 > page_size(page)); 370 371 for (i = 0; i < compound_nr(page); i++) { 372 void *kaddr = NULL; 373 374 if (start1 < PAGE_SIZE || start2 < PAGE_SIZE) 375 kaddr = kmap_atomic(page + i); 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 memset(kaddr + start1, 0, this_end - start1); 385 end1 -= this_end; 386 start1 = 0; 387 } 388 389 if (start2 >= PAGE_SIZE) { 390 start2 -= PAGE_SIZE; 391 end2 -= PAGE_SIZE; 392 } else { 393 unsigned this_end = min_t(unsigned, end2, PAGE_SIZE); 394 395 if (end2 > start2) 396 memset(kaddr + start2, 0, this_end - start2); 397 end2 -= this_end; 398 start2 = 0; 399 } 400 401 if (kaddr) { 402 kunmap_atomic(kaddr); 403 flush_dcache_page(page + i); 404 } 405 406 if (!end1 && !end2) 407 break; 408 } 409 410 BUG_ON((start1 | start2 | end1 | end2) != 0); 411 } 412 EXPORT_SYMBOL(zero_user_segments); 413 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ 414 #endif /* CONFIG_HIGHMEM */ 415 416 #ifdef CONFIG_KMAP_LOCAL 417 418 #include <asm/kmap_size.h> 419 420 /* 421 * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second 422 * slot is unused which acts as a guard page 423 */ 424 #ifdef CONFIG_DEBUG_KMAP_LOCAL 425 # define KM_INCR 2 426 #else 427 # define KM_INCR 1 428 #endif 429 430 static inline int kmap_local_idx_push(void) 431 { 432 WARN_ON_ONCE(in_irq() && !irqs_disabled()); 433 current->kmap_ctrl.idx += KM_INCR; 434 BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX); 435 return current->kmap_ctrl.idx - 1; 436 } 437 438 static inline int kmap_local_idx(void) 439 { 440 return current->kmap_ctrl.idx - 1; 441 } 442 443 static inline void kmap_local_idx_pop(void) 444 { 445 current->kmap_ctrl.idx -= KM_INCR; 446 BUG_ON(current->kmap_ctrl.idx < 0); 447 } 448 449 #ifndef arch_kmap_local_post_map 450 # define arch_kmap_local_post_map(vaddr, pteval) do { } while (0) 451 #endif 452 453 #ifndef arch_kmap_local_pre_unmap 454 # define arch_kmap_local_pre_unmap(vaddr) do { } while (0) 455 #endif 456 457 #ifndef arch_kmap_local_post_unmap 458 # define arch_kmap_local_post_unmap(vaddr) do { } while (0) 459 #endif 460 461 #ifndef arch_kmap_local_map_idx 462 #define arch_kmap_local_map_idx(idx, pfn) kmap_local_calc_idx(idx) 463 #endif 464 465 #ifndef arch_kmap_local_unmap_idx 466 #define arch_kmap_local_unmap_idx(idx, vaddr) kmap_local_calc_idx(idx) 467 #endif 468 469 #ifndef arch_kmap_local_high_get 470 static inline void *arch_kmap_local_high_get(struct page *page) 471 { 472 return NULL; 473 } 474 #endif 475 476 #ifndef arch_kmap_local_set_pte 477 #define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev) \ 478 set_pte_at(mm, vaddr, ptep, ptev) 479 #endif 480 481 /* Unmap a local mapping which was obtained by kmap_high_get() */ 482 static inline bool kmap_high_unmap_local(unsigned long vaddr) 483 { 484 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 485 if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) { 486 kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)])); 487 return true; 488 } 489 #endif 490 return false; 491 } 492 493 static inline int kmap_local_calc_idx(int idx) 494 { 495 return idx + KM_MAX_IDX * smp_processor_id(); 496 } 497 498 static pte_t *__kmap_pte; 499 500 static pte_t *kmap_get_pte(void) 501 { 502 if (!__kmap_pte) 503 __kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN)); 504 return __kmap_pte; 505 } 506 507 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot) 508 { 509 pte_t pteval, *kmap_pte = kmap_get_pte(); 510 unsigned long vaddr; 511 int idx; 512 513 /* 514 * Disable migration so resulting virtual address is stable 515 * accross preemption. 516 */ 517 migrate_disable(); 518 preempt_disable(); 519 idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn); 520 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); 521 BUG_ON(!pte_none(*(kmap_pte - idx))); 522 pteval = pfn_pte(pfn, prot); 523 arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte - idx, pteval); 524 arch_kmap_local_post_map(vaddr, pteval); 525 current->kmap_ctrl.pteval[kmap_local_idx()] = pteval; 526 preempt_enable(); 527 528 return (void *)vaddr; 529 } 530 EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot); 531 532 void *__kmap_local_page_prot(struct page *page, pgprot_t prot) 533 { 534 void *kmap; 535 536 /* 537 * To broaden the usage of the actual kmap_local() machinery always map 538 * pages when debugging is enabled and the architecture has no problems 539 * with alias mappings. 540 */ 541 if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page)) 542 return page_address(page); 543 544 /* Try kmap_high_get() if architecture has it enabled */ 545 kmap = arch_kmap_local_high_get(page); 546 if (kmap) 547 return kmap; 548 549 return __kmap_local_pfn_prot(page_to_pfn(page), prot); 550 } 551 EXPORT_SYMBOL(__kmap_local_page_prot); 552 553 void kunmap_local_indexed(void *vaddr) 554 { 555 unsigned long addr = (unsigned long) vaddr & PAGE_MASK; 556 pte_t *kmap_pte = kmap_get_pte(); 557 int idx; 558 559 if (addr < __fix_to_virt(FIX_KMAP_END) || 560 addr > __fix_to_virt(FIX_KMAP_BEGIN)) { 561 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) { 562 /* This _should_ never happen! See above. */ 563 WARN_ON_ONCE(1); 564 return; 565 } 566 /* 567 * Handle mappings which were obtained by kmap_high_get() 568 * first as the virtual address of such mappings is below 569 * PAGE_OFFSET. Warn for all other addresses which are in 570 * the user space part of the virtual address space. 571 */ 572 if (!kmap_high_unmap_local(addr)) 573 WARN_ON_ONCE(addr < PAGE_OFFSET); 574 return; 575 } 576 577 preempt_disable(); 578 idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr); 579 WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx)); 580 581 arch_kmap_local_pre_unmap(addr); 582 pte_clear(&init_mm, addr, kmap_pte - idx); 583 arch_kmap_local_post_unmap(addr); 584 current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0); 585 kmap_local_idx_pop(); 586 preempt_enable(); 587 migrate_enable(); 588 } 589 EXPORT_SYMBOL(kunmap_local_indexed); 590 591 /* 592 * Invoked before switch_to(). This is safe even when during or after 593 * clearing the maps an interrupt which needs a kmap_local happens because 594 * the task::kmap_ctrl.idx is not modified by the unmapping code so a 595 * nested kmap_local will use the next unused index and restore the index 596 * on unmap. The already cleared kmaps of the outgoing task are irrelevant 597 * because the interrupt context does not know about them. The same applies 598 * when scheduling back in for an interrupt which happens before the 599 * restore is complete. 600 */ 601 void __kmap_local_sched_out(void) 602 { 603 struct task_struct *tsk = current; 604 pte_t *kmap_pte = kmap_get_pte(); 605 int i; 606 607 /* Clear kmaps */ 608 for (i = 0; i < tsk->kmap_ctrl.idx; i++) { 609 pte_t pteval = tsk->kmap_ctrl.pteval[i]; 610 unsigned long addr; 611 int idx; 612 613 /* With debug all even slots are unmapped and act as guard */ 614 if (IS_ENABLED(CONFIG_DEBUG_HIGHMEM) && !(i & 0x01)) { 615 WARN_ON_ONCE(!pte_none(pteval)); 616 continue; 617 } 618 if (WARN_ON_ONCE(pte_none(pteval))) 619 continue; 620 621 /* 622 * This is a horrible hack for XTENSA to calculate the 623 * coloured PTE index. Uses the PFN encoded into the pteval 624 * and the map index calculation because the actual mapped 625 * virtual address is not stored in task::kmap_ctrl. 626 * For any sane architecture this is optimized out. 627 */ 628 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); 629 630 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); 631 arch_kmap_local_pre_unmap(addr); 632 pte_clear(&init_mm, addr, kmap_pte - idx); 633 arch_kmap_local_post_unmap(addr); 634 } 635 } 636 637 void __kmap_local_sched_in(void) 638 { 639 struct task_struct *tsk = current; 640 pte_t *kmap_pte = kmap_get_pte(); 641 int i; 642 643 /* Restore kmaps */ 644 for (i = 0; i < tsk->kmap_ctrl.idx; i++) { 645 pte_t pteval = tsk->kmap_ctrl.pteval[i]; 646 unsigned long addr; 647 int idx; 648 649 /* With debug all even slots are unmapped and act as guard */ 650 if (IS_ENABLED(CONFIG_DEBUG_HIGHMEM) && !(i & 0x01)) { 651 WARN_ON_ONCE(!pte_none(pteval)); 652 continue; 653 } 654 if (WARN_ON_ONCE(pte_none(pteval))) 655 continue; 656 657 /* See comment in __kmap_local_sched_out() */ 658 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); 659 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); 660 set_pte_at(&init_mm, addr, kmap_pte - idx, pteval); 661 arch_kmap_local_post_map(addr, pteval); 662 } 663 } 664 665 void kmap_local_fork(struct task_struct *tsk) 666 { 667 if (WARN_ON_ONCE(tsk->kmap_ctrl.idx)) 668 memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl)); 669 } 670 671 #endif 672 673 #if defined(HASHED_PAGE_VIRTUAL) 674 675 #define PA_HASH_ORDER 7 676 677 /* 678 * Describes one page->virtual association 679 */ 680 struct page_address_map { 681 struct page *page; 682 void *virtual; 683 struct list_head list; 684 }; 685 686 static struct page_address_map page_address_maps[LAST_PKMAP]; 687 688 /* 689 * Hash table bucket 690 */ 691 static struct page_address_slot { 692 struct list_head lh; /* List of page_address_maps */ 693 spinlock_t lock; /* Protect this bucket's list */ 694 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER]; 695 696 static struct page_address_slot *page_slot(const struct page *page) 697 { 698 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; 699 } 700 701 /** 702 * page_address - get the mapped virtual address of a page 703 * @page: &struct page to get the virtual address of 704 * 705 * Returns the page's virtual address. 706 */ 707 void *page_address(const struct page *page) 708 { 709 unsigned long flags; 710 void *ret; 711 struct page_address_slot *pas; 712 713 if (!PageHighMem(page)) 714 return lowmem_page_address(page); 715 716 pas = page_slot(page); 717 ret = NULL; 718 spin_lock_irqsave(&pas->lock, flags); 719 if (!list_empty(&pas->lh)) { 720 struct page_address_map *pam; 721 722 list_for_each_entry(pam, &pas->lh, list) { 723 if (pam->page == page) { 724 ret = pam->virtual; 725 goto done; 726 } 727 } 728 } 729 done: 730 spin_unlock_irqrestore(&pas->lock, flags); 731 return ret; 732 } 733 734 EXPORT_SYMBOL(page_address); 735 736 /** 737 * set_page_address - set a page's virtual address 738 * @page: &struct page to set 739 * @virtual: virtual address to use 740 */ 741 void set_page_address(struct page *page, void *virtual) 742 { 743 unsigned long flags; 744 struct page_address_slot *pas; 745 struct page_address_map *pam; 746 747 BUG_ON(!PageHighMem(page)); 748 749 pas = page_slot(page); 750 if (virtual) { /* Add */ 751 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)]; 752 pam->page = page; 753 pam->virtual = virtual; 754 755 spin_lock_irqsave(&pas->lock, flags); 756 list_add_tail(&pam->list, &pas->lh); 757 spin_unlock_irqrestore(&pas->lock, flags); 758 } else { /* Remove */ 759 spin_lock_irqsave(&pas->lock, flags); 760 list_for_each_entry(pam, &pas->lh, list) { 761 if (pam->page == page) { 762 list_del(&pam->list); 763 spin_unlock_irqrestore(&pas->lock, flags); 764 goto done; 765 } 766 } 767 spin_unlock_irqrestore(&pas->lock, flags); 768 } 769 done: 770 return; 771 } 772 773 void __init page_address_init(void) 774 { 775 int i; 776 777 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) { 778 INIT_LIST_HEAD(&page_address_htable[i].lh); 779 spin_lock_init(&page_address_htable[i].lock); 780 } 781 } 782 783 #endif /* defined(HASHED_PAGE_VIRTUAL) */ 784