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
33
34 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
35 DEFINE_PER_CPU(int, __kmap_atomic_idx);
36 #endif
37
38 /*
39 * Virtual_count is not a pure "count".
40 * 0 means that it is not mapped, and has not been mapped
41 * since a TLB flush - it is usable.
42 * 1 means that there are no users, but it has been mapped
43 * since the last TLB flush - so we can't use it.
44 * n means that there are (n-1) current users of it.
45 */
46 #ifdef CONFIG_HIGHMEM
47
48 /*
49 * Architecture with aliasing data cache may define the following family of
50 * helper functions in its asm/highmem.h to control cache color of virtual
51 * addresses where physical memory pages are mapped by kmap.
52 */
53 #ifndef get_pkmap_color
54
55 /*
56 * Determine color of virtual address where the page should be mapped.
57 */
get_pkmap_color(struct page * page)58 static inline unsigned int get_pkmap_color(struct page *page)
59 {
60 return 0;
61 }
62 #define get_pkmap_color get_pkmap_color
63
64 /*
65 * Get next index for mapping inside PKMAP region for page with given color.
66 */
get_next_pkmap_nr(unsigned int color)67 static inline unsigned int get_next_pkmap_nr(unsigned int color)
68 {
69 static unsigned int last_pkmap_nr;
70
71 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
72 return last_pkmap_nr;
73 }
74
75 /*
76 * Determine if page index inside PKMAP region (pkmap_nr) of given color
77 * has wrapped around PKMAP region end. When this happens an attempt to
78 * flush all unused PKMAP slots is made.
79 */
no_more_pkmaps(unsigned int pkmap_nr,unsigned int color)80 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
81 {
82 return pkmap_nr == 0;
83 }
84
85 /*
86 * Get the number of PKMAP entries of the given color. If no free slot is
87 * found after checking that many entries, kmap will sleep waiting for
88 * someone to call kunmap and free PKMAP slot.
89 */
get_pkmap_entries_count(unsigned int color)90 static inline int get_pkmap_entries_count(unsigned int color)
91 {
92 return LAST_PKMAP;
93 }
94
95 /*
96 * Get head of a wait queue for PKMAP entries of the given color.
97 * Wait queues for different mapping colors should be independent to avoid
98 * unnecessary wakeups caused by freeing of slots of other colors.
99 */
get_pkmap_wait_queue_head(unsigned int color)100 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
101 {
102 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
103
104 return &pkmap_map_wait;
105 }
106 #endif
107
108 unsigned long totalhigh_pages __read_mostly;
109 EXPORT_SYMBOL(totalhigh_pages);
110
111
112 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
113
nr_free_highpages(void)114 unsigned int nr_free_highpages (void)
115 {
116 struct zone *zone;
117 unsigned int pages = 0;
118
119 for_each_populated_zone(zone) {
120 if (is_highmem(zone))
121 pages += zone_page_state(zone, NR_FREE_PAGES);
122 }
123
124 return pages;
125 }
126
127 static int pkmap_count[LAST_PKMAP];
128 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
129
130 pte_t * pkmap_page_table;
131
132 /*
133 * Most architectures have no use for kmap_high_get(), so let's abstract
134 * the disabling of IRQ out of the locking in that case to save on a
135 * potential useless overhead.
136 */
137 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
138 #define lock_kmap() spin_lock_irq(&kmap_lock)
139 #define unlock_kmap() spin_unlock_irq(&kmap_lock)
140 #define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
141 #define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
142 #else
143 #define lock_kmap() spin_lock(&kmap_lock)
144 #define unlock_kmap() spin_unlock(&kmap_lock)
145 #define lock_kmap_any(flags) \
146 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
147 #define unlock_kmap_any(flags) \
148 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
149 #endif
150
kmap_to_page(void * vaddr)151 struct page *kmap_to_page(void *vaddr)
152 {
153 unsigned long addr = (unsigned long)vaddr;
154
155 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
156 int i = PKMAP_NR(addr);
157 return pte_page(pkmap_page_table[i]);
158 }
159
160 return virt_to_page(addr);
161 }
162 EXPORT_SYMBOL(kmap_to_page);
163
flush_all_zero_pkmaps(void)164 static void flush_all_zero_pkmaps(void)
165 {
166 int i;
167 int need_flush = 0;
168
169 flush_cache_kmaps();
170
171 for (i = 0; i < LAST_PKMAP; i++) {
172 struct page *page;
173
174 /*
175 * zero means we don't have anything to do,
176 * >1 means that it is still in use. Only
177 * a count of 1 means that it is free but
178 * needs to be unmapped
179 */
180 if (pkmap_count[i] != 1)
181 continue;
182 pkmap_count[i] = 0;
183
184 /* sanity check */
185 BUG_ON(pte_none(pkmap_page_table[i]));
186
187 /*
188 * Don't need an atomic fetch-and-clear op here;
189 * no-one has the page mapped, and cannot get at
190 * its virtual address (and hence PTE) without first
191 * getting the kmap_lock (which is held here).
192 * So no dangers, even with speculative execution.
193 */
194 page = pte_page(pkmap_page_table[i]);
195 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
196
197 set_page_address(page, NULL);
198 need_flush = 1;
199 }
200 if (need_flush)
201 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
202 }
203
204 /**
205 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
206 */
kmap_flush_unused(void)207 void kmap_flush_unused(void)
208 {
209 lock_kmap();
210 flush_all_zero_pkmaps();
211 unlock_kmap();
212 }
213
map_new_virtual(struct page * page)214 static inline unsigned long map_new_virtual(struct page *page)
215 {
216 unsigned long vaddr;
217 int count;
218 unsigned int last_pkmap_nr;
219 unsigned int color = get_pkmap_color(page);
220
221 start:
222 count = get_pkmap_entries_count(color);
223 /* Find an empty entry */
224 for (;;) {
225 last_pkmap_nr = get_next_pkmap_nr(color);
226 if (no_more_pkmaps(last_pkmap_nr, color)) {
227 flush_all_zero_pkmaps();
228 count = get_pkmap_entries_count(color);
229 }
230 if (!pkmap_count[last_pkmap_nr])
231 break; /* Found a usable entry */
232 if (--count)
233 continue;
234
235 /*
236 * Sleep for somebody else to unmap their entries
237 */
238 {
239 DECLARE_WAITQUEUE(wait, current);
240 wait_queue_head_t *pkmap_map_wait =
241 get_pkmap_wait_queue_head(color);
242
243 __set_current_state(TASK_UNINTERRUPTIBLE);
244 add_wait_queue(pkmap_map_wait, &wait);
245 unlock_kmap();
246 schedule();
247 remove_wait_queue(pkmap_map_wait, &wait);
248 lock_kmap();
249
250 /* Somebody else might have mapped it while we slept */
251 if (page_address(page))
252 return (unsigned long)page_address(page);
253
254 /* Re-start */
255 goto start;
256 }
257 }
258 vaddr = PKMAP_ADDR(last_pkmap_nr);
259 set_pte_at(&init_mm, vaddr,
260 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
261
262 pkmap_count[last_pkmap_nr] = 1;
263 set_page_address(page, (void *)vaddr);
264
265 return vaddr;
266 }
267
268 /**
269 * kmap_high - map a highmem page into memory
270 * @page: &struct page to map
271 *
272 * Returns the page's virtual memory address.
273 *
274 * We cannot call this from interrupts, as it may block.
275 */
kmap_high(struct page * page)276 void *kmap_high(struct page *page)
277 {
278 unsigned long vaddr;
279
280 /*
281 * For highmem pages, we can't trust "virtual" until
282 * after we have the lock.
283 */
284 lock_kmap();
285 vaddr = (unsigned long)page_address(page);
286 if (!vaddr)
287 vaddr = map_new_virtual(page);
288 pkmap_count[PKMAP_NR(vaddr)]++;
289 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
290 unlock_kmap();
291 return (void*) vaddr;
292 }
293
294 EXPORT_SYMBOL(kmap_high);
295
296 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
297 /**
298 * kmap_high_get - pin a highmem page into memory
299 * @page: &struct page to pin
300 *
301 * Returns the page's current virtual memory address, or NULL if no mapping
302 * exists. If and only if a non null address is returned then a
303 * matching call to kunmap_high() is necessary.
304 *
305 * This can be called from any context.
306 */
kmap_high_get(struct page * page)307 void *kmap_high_get(struct page *page)
308 {
309 unsigned long vaddr, flags;
310
311 lock_kmap_any(flags);
312 vaddr = (unsigned long)page_address(page);
313 if (vaddr) {
314 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
315 pkmap_count[PKMAP_NR(vaddr)]++;
316 }
317 unlock_kmap_any(flags);
318 return (void*) vaddr;
319 }
320 #endif
321
322 /**
323 * kunmap_high - unmap a highmem page into memory
324 * @page: &struct page to unmap
325 *
326 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
327 * only from user context.
328 */
kunmap_high(struct page * page)329 void kunmap_high(struct page *page)
330 {
331 unsigned long vaddr;
332 unsigned long nr;
333 unsigned long flags;
334 int need_wakeup;
335 unsigned int color = get_pkmap_color(page);
336 wait_queue_head_t *pkmap_map_wait;
337
338 lock_kmap_any(flags);
339 vaddr = (unsigned long)page_address(page);
340 BUG_ON(!vaddr);
341 nr = PKMAP_NR(vaddr);
342
343 /*
344 * A count must never go down to zero
345 * without a TLB flush!
346 */
347 need_wakeup = 0;
348 switch (--pkmap_count[nr]) {
349 case 0:
350 BUG();
351 case 1:
352 /*
353 * Avoid an unnecessary wake_up() function call.
354 * The common case is pkmap_count[] == 1, but
355 * no waiters.
356 * The tasks queued in the wait-queue are guarded
357 * by both the lock in the wait-queue-head and by
358 * the kmap_lock. As the kmap_lock is held here,
359 * no need for the wait-queue-head's lock. Simply
360 * test if the queue is empty.
361 */
362 pkmap_map_wait = get_pkmap_wait_queue_head(color);
363 need_wakeup = waitqueue_active(pkmap_map_wait);
364 }
365 unlock_kmap_any(flags);
366
367 /* do wake-up, if needed, race-free outside of the spin lock */
368 if (need_wakeup)
369 wake_up(pkmap_map_wait);
370 }
371
372 EXPORT_SYMBOL(kunmap_high);
373 #endif
374
375 #if defined(HASHED_PAGE_VIRTUAL)
376
377 #define PA_HASH_ORDER 7
378
379 /*
380 * Describes one page->virtual association
381 */
382 struct page_address_map {
383 struct page *page;
384 void *virtual;
385 struct list_head list;
386 };
387
388 static struct page_address_map page_address_maps[LAST_PKMAP];
389
390 /*
391 * Hash table bucket
392 */
393 static struct page_address_slot {
394 struct list_head lh; /* List of page_address_maps */
395 spinlock_t lock; /* Protect this bucket's list */
396 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
397
page_slot(const struct page * page)398 static struct page_address_slot *page_slot(const struct page *page)
399 {
400 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
401 }
402
403 /**
404 * page_address - get the mapped virtual address of a page
405 * @page: &struct page to get the virtual address of
406 *
407 * Returns the page's virtual address.
408 */
page_address(const struct page * page)409 void *page_address(const struct page *page)
410 {
411 unsigned long flags;
412 void *ret;
413 struct page_address_slot *pas;
414
415 if (!PageHighMem(page))
416 return lowmem_page_address(page);
417
418 pas = page_slot(page);
419 ret = NULL;
420 spin_lock_irqsave(&pas->lock, flags);
421 if (!list_empty(&pas->lh)) {
422 struct page_address_map *pam;
423
424 list_for_each_entry(pam, &pas->lh, list) {
425 if (pam->page == page) {
426 ret = pam->virtual;
427 goto done;
428 }
429 }
430 }
431 done:
432 spin_unlock_irqrestore(&pas->lock, flags);
433 return ret;
434 }
435
436 EXPORT_SYMBOL(page_address);
437
438 /**
439 * set_page_address - set a page's virtual address
440 * @page: &struct page to set
441 * @virtual: virtual address to use
442 */
set_page_address(struct page * page,void * virtual)443 void set_page_address(struct page *page, void *virtual)
444 {
445 unsigned long flags;
446 struct page_address_slot *pas;
447 struct page_address_map *pam;
448
449 BUG_ON(!PageHighMem(page));
450
451 pas = page_slot(page);
452 if (virtual) { /* Add */
453 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
454 pam->page = page;
455 pam->virtual = virtual;
456
457 spin_lock_irqsave(&pas->lock, flags);
458 list_add_tail(&pam->list, &pas->lh);
459 spin_unlock_irqrestore(&pas->lock, flags);
460 } else { /* Remove */
461 spin_lock_irqsave(&pas->lock, flags);
462 list_for_each_entry(pam, &pas->lh, list) {
463 if (pam->page == page) {
464 list_del(&pam->list);
465 spin_unlock_irqrestore(&pas->lock, flags);
466 goto done;
467 }
468 }
469 spin_unlock_irqrestore(&pas->lock, flags);
470 }
471 done:
472 return;
473 }
474
page_address_init(void)475 void __init page_address_init(void)
476 {
477 int i;
478
479 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
480 INIT_LIST_HEAD(&page_address_htable[i].lh);
481 spin_lock_init(&page_address_htable[i].lock);
482 }
483 }
484
485 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
486
