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