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1 /*
2  * High memory handling common code and variables.
3  *
4  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6  *
7  *
8  * Redesigned the x86 32-bit VM architecture to deal with
9  * 64-bit physical space. With current x86 CPUs this
10  * means up to 64 Gigabytes physical RAM.
11  *
12  * Rewrote high memory support to move the page cache into
13  * high memory. Implemented permanent (schedulable) kmaps
14  * based on Linus' idea.
15  *
16  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17  */
18 
19 #include <linux/mm.h>
20 #include <linux/export.h>
21 #include <linux/swap.h>
22 #include <linux/bio.h>
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/blkdev.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 
32 
33 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
34 DEFINE_PER_CPU(int, __kmap_atomic_idx);
35 #endif
36 
37 /*
38  * Virtual_count is not a pure "count".
39  *  0 means that it is not mapped, and has not been mapped
40  *    since a TLB flush - it is usable.
41  *  1 means that there are no users, but it has been mapped
42  *    since the last TLB flush - so we can't use it.
43  *  n means that there are (n-1) current users of it.
44  */
45 #ifdef CONFIG_HIGHMEM
46 
47 /*
48  * Architecture with aliasing data cache may define the following family of
49  * helper functions in its asm/highmem.h to control cache color of virtual
50  * addresses where physical memory pages are mapped by kmap.
51  */
52 #ifndef get_pkmap_color
53 
54 /*
55  * Determine color of virtual address where the page should be mapped.
56  */
get_pkmap_color(struct page * page)57 static inline unsigned int get_pkmap_color(struct page *page)
58 {
59 	return 0;
60 }
61 #define get_pkmap_color get_pkmap_color
62 
63 /*
64  * Get next index for mapping inside PKMAP region for page with given color.
65  */
get_next_pkmap_nr(unsigned int color)66 static inline unsigned int get_next_pkmap_nr(unsigned int color)
67 {
68 	static unsigned int last_pkmap_nr;
69 
70 	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
71 	return last_pkmap_nr;
72 }
73 
74 /*
75  * Determine if page index inside PKMAP region (pkmap_nr) of given color
76  * has wrapped around PKMAP region end. When this happens an attempt to
77  * flush all unused PKMAP slots is made.
78  */
no_more_pkmaps(unsigned int pkmap_nr,unsigned int color)79 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
80 {
81 	return pkmap_nr == 0;
82 }
83 
84 /*
85  * Get the number of PKMAP entries of the given color. If no free slot is
86  * found after checking that many entries, kmap will sleep waiting for
87  * someone to call kunmap and free PKMAP slot.
88  */
get_pkmap_entries_count(unsigned int color)89 static inline int get_pkmap_entries_count(unsigned int color)
90 {
91 	return LAST_PKMAP;
92 }
93 
94 /*
95  * Get head of a wait queue for PKMAP entries of the given color.
96  * Wait queues for different mapping colors should be independent to avoid
97  * unnecessary wakeups caused by freeing of slots of other colors.
98  */
get_pkmap_wait_queue_head(unsigned int color)99 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
100 {
101 	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
102 
103 	return &pkmap_map_wait;
104 }
105 #endif
106 
107 unsigned long totalhigh_pages __read_mostly;
108 EXPORT_SYMBOL(totalhigh_pages);
109 
110 
111 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
112 
nr_free_highpages(void)113 unsigned int nr_free_highpages (void)
114 {
115 	pg_data_t *pgdat;
116 	unsigned int pages = 0;
117 
118 	for_each_online_pgdat(pgdat) {
119 		pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
120 			NR_FREE_PAGES);
121 		if (zone_movable_is_highmem())
122 			pages += zone_page_state(
123 					&pgdat->node_zones[ZONE_MOVABLE],
124 					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 
kmap_to_page(void * vaddr)154 struct page *kmap_to_page(void *vaddr)
155 {
156 	unsigned long addr = (unsigned long)vaddr;
157 
158 	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
159 		int i = PKMAP_NR(addr);
160 		return pte_page(pkmap_page_table[i]);
161 	}
162 
163 	return virt_to_page(addr);
164 }
165 EXPORT_SYMBOL(kmap_to_page);
166 
flush_all_zero_pkmaps(void)167 static void flush_all_zero_pkmaps(void)
168 {
169 	int i;
170 	int need_flush = 0;
171 
172 	flush_cache_kmaps();
173 
174 	for (i = 0; i < LAST_PKMAP; i++) {
175 		struct page *page;
176 
177 		/*
178 		 * zero means we don't have anything to do,
179 		 * >1 means that it is still in use. Only
180 		 * a count of 1 means that it is free but
181 		 * needs to be unmapped
182 		 */
183 		if (pkmap_count[i] != 1)
184 			continue;
185 		pkmap_count[i] = 0;
186 
187 		/* sanity check */
188 		BUG_ON(pte_none(pkmap_page_table[i]));
189 
190 		/*
191 		 * Don't need an atomic fetch-and-clear op here;
192 		 * no-one has the page mapped, and cannot get at
193 		 * its virtual address (and hence PTE) without first
194 		 * getting the kmap_lock (which is held here).
195 		 * So no dangers, even with speculative execution.
196 		 */
197 		page = pte_page(pkmap_page_table[i]);
198 		pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
199 
200 		set_page_address(page, NULL);
201 		need_flush = 1;
202 	}
203 	if (need_flush)
204 		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
205 }
206 
207 /**
208  * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
209  */
kmap_flush_unused(void)210 void kmap_flush_unused(void)
211 {
212 	lock_kmap();
213 	flush_all_zero_pkmaps();
214 	unlock_kmap();
215 }
216 
map_new_virtual(struct page * page)217 static inline unsigned long map_new_virtual(struct page *page)
218 {
219 	unsigned long vaddr;
220 	int count;
221 	unsigned int last_pkmap_nr;
222 	unsigned int color = get_pkmap_color(page);
223 
224 start:
225 	count = get_pkmap_entries_count(color);
226 	/* Find an empty entry */
227 	for (;;) {
228 		last_pkmap_nr = get_next_pkmap_nr(color);
229 		if (no_more_pkmaps(last_pkmap_nr, color)) {
230 			flush_all_zero_pkmaps();
231 			count = get_pkmap_entries_count(color);
232 		}
233 		if (!pkmap_count[last_pkmap_nr])
234 			break;	/* Found a usable entry */
235 		if (--count)
236 			continue;
237 
238 		/*
239 		 * Sleep for somebody else to unmap their entries
240 		 */
241 		{
242 			DECLARE_WAITQUEUE(wait, current);
243 			wait_queue_head_t *pkmap_map_wait =
244 				get_pkmap_wait_queue_head(color);
245 
246 			__set_current_state(TASK_UNINTERRUPTIBLE);
247 			add_wait_queue(pkmap_map_wait, &wait);
248 			unlock_kmap();
249 			schedule();
250 			remove_wait_queue(pkmap_map_wait, &wait);
251 			lock_kmap();
252 
253 			/* Somebody else might have mapped it while we slept */
254 			if (page_address(page))
255 				return (unsigned long)page_address(page);
256 
257 			/* Re-start */
258 			goto start;
259 		}
260 	}
261 	vaddr = PKMAP_ADDR(last_pkmap_nr);
262 	set_pte_at(&init_mm, vaddr,
263 		   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
264 
265 	pkmap_count[last_pkmap_nr] = 1;
266 	set_page_address(page, (void *)vaddr);
267 
268 	return vaddr;
269 }
270 
271 /**
272  * kmap_high - map a highmem page into memory
273  * @page: &struct page to map
274  *
275  * Returns the page's virtual memory address.
276  *
277  * We cannot call this from interrupts, as it may block.
278  */
kmap_high(struct page * page)279 void *kmap_high(struct page *page)
280 {
281 	unsigned long vaddr;
282 
283 	/*
284 	 * For highmem pages, we can't trust "virtual" until
285 	 * after we have the lock.
286 	 */
287 	lock_kmap();
288 	vaddr = (unsigned long)page_address(page);
289 	if (!vaddr)
290 		vaddr = map_new_virtual(page);
291 	pkmap_count[PKMAP_NR(vaddr)]++;
292 	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
293 	unlock_kmap();
294 	return (void*) vaddr;
295 }
296 
297 EXPORT_SYMBOL(kmap_high);
298 
299 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
300 /**
301  * kmap_high_get - pin a highmem page into memory
302  * @page: &struct page to pin
303  *
304  * Returns the page's current virtual memory address, or NULL if no mapping
305  * exists.  If and only if a non null address is returned then a
306  * matching call to kunmap_high() is necessary.
307  *
308  * This can be called from any context.
309  */
kmap_high_get(struct page * page)310 void *kmap_high_get(struct page *page)
311 {
312 	unsigned long vaddr, flags;
313 
314 	lock_kmap_any(flags);
315 	vaddr = (unsigned long)page_address(page);
316 	if (vaddr) {
317 		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
318 		pkmap_count[PKMAP_NR(vaddr)]++;
319 	}
320 	unlock_kmap_any(flags);
321 	return (void*) vaddr;
322 }
323 #endif
324 
325 /**
326  * kunmap_high - unmap a highmem page into memory
327  * @page: &struct page to unmap
328  *
329  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
330  * only from user context.
331  */
kunmap_high(struct page * page)332 void kunmap_high(struct page *page)
333 {
334 	unsigned long vaddr;
335 	unsigned long nr;
336 	unsigned long flags;
337 	int need_wakeup;
338 	unsigned int color = get_pkmap_color(page);
339 	wait_queue_head_t *pkmap_map_wait;
340 
341 	lock_kmap_any(flags);
342 	vaddr = (unsigned long)page_address(page);
343 	BUG_ON(!vaddr);
344 	nr = PKMAP_NR(vaddr);
345 
346 	/*
347 	 * A count must never go down to zero
348 	 * without a TLB flush!
349 	 */
350 	need_wakeup = 0;
351 	switch (--pkmap_count[nr]) {
352 	case 0:
353 		BUG();
354 	case 1:
355 		/*
356 		 * Avoid an unnecessary wake_up() function call.
357 		 * The common case is pkmap_count[] == 1, but
358 		 * no waiters.
359 		 * The tasks queued in the wait-queue are guarded
360 		 * by both the lock in the wait-queue-head and by
361 		 * the kmap_lock.  As the kmap_lock is held here,
362 		 * no need for the wait-queue-head's lock.  Simply
363 		 * test if the queue is empty.
364 		 */
365 		pkmap_map_wait = get_pkmap_wait_queue_head(color);
366 		need_wakeup = waitqueue_active(pkmap_map_wait);
367 	}
368 	unlock_kmap_any(flags);
369 
370 	/* do wake-up, if needed, race-free outside of the spin lock */
371 	if (need_wakeup)
372 		wake_up(pkmap_map_wait);
373 }
374 
375 EXPORT_SYMBOL(kunmap_high);
376 #endif
377 
378 #if defined(HASHED_PAGE_VIRTUAL)
379 
380 #define PA_HASH_ORDER	7
381 
382 /*
383  * Describes one page->virtual association
384  */
385 struct page_address_map {
386 	struct page *page;
387 	void *virtual;
388 	struct list_head list;
389 };
390 
391 static struct page_address_map page_address_maps[LAST_PKMAP];
392 
393 /*
394  * Hash table bucket
395  */
396 static struct page_address_slot {
397 	struct list_head lh;			/* List of page_address_maps */
398 	spinlock_t lock;			/* Protect this bucket's list */
399 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
400 
page_slot(const struct page * page)401 static struct page_address_slot *page_slot(const struct page *page)
402 {
403 	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
404 }
405 
406 /**
407  * page_address - get the mapped virtual address of a page
408  * @page: &struct page to get the virtual address of
409  *
410  * Returns the page's virtual address.
411  */
page_address(const struct page * page)412 void *page_address(const struct page *page)
413 {
414 	unsigned long flags;
415 	void *ret;
416 	struct page_address_slot *pas;
417 
418 	if (!PageHighMem(page))
419 		return lowmem_page_address(page);
420 
421 	pas = page_slot(page);
422 	ret = NULL;
423 	spin_lock_irqsave(&pas->lock, flags);
424 	if (!list_empty(&pas->lh)) {
425 		struct page_address_map *pam;
426 
427 		list_for_each_entry(pam, &pas->lh, list) {
428 			if (pam->page == page) {
429 				ret = pam->virtual;
430 				goto done;
431 			}
432 		}
433 	}
434 done:
435 	spin_unlock_irqrestore(&pas->lock, flags);
436 	return ret;
437 }
438 
439 EXPORT_SYMBOL(page_address);
440 
441 /**
442  * set_page_address - set a page's virtual address
443  * @page: &struct page to set
444  * @virtual: virtual address to use
445  */
set_page_address(struct page * page,void * virtual)446 void set_page_address(struct page *page, void *virtual)
447 {
448 	unsigned long flags;
449 	struct page_address_slot *pas;
450 	struct page_address_map *pam;
451 
452 	BUG_ON(!PageHighMem(page));
453 
454 	pas = page_slot(page);
455 	if (virtual) {		/* Add */
456 		pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
457 		pam->page = page;
458 		pam->virtual = virtual;
459 
460 		spin_lock_irqsave(&pas->lock, flags);
461 		list_add_tail(&pam->list, &pas->lh);
462 		spin_unlock_irqrestore(&pas->lock, flags);
463 	} else {		/* Remove */
464 		spin_lock_irqsave(&pas->lock, flags);
465 		list_for_each_entry(pam, &pas->lh, list) {
466 			if (pam->page == page) {
467 				list_del(&pam->list);
468 				spin_unlock_irqrestore(&pas->lock, flags);
469 				goto done;
470 			}
471 		}
472 		spin_unlock_irqrestore(&pas->lock, flags);
473 	}
474 done:
475 	return;
476 }
477 
page_address_init(void)478 void __init page_address_init(void)
479 {
480 	int i;
481 
482 	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
483 		INIT_LIST_HEAD(&page_address_htable[i].lh);
484 		spin_lock_init(&page_address_htable[i].lock);
485 	}
486 }
487 
488 #endif	/* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
489