summaryrefslogtreecommitdiff
path: root/include/linux/highmem.h
blob: 4cacc0e43b5139863d86c4dbcd85488b8fd9a7a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_HIGHMEM_H
#define _LINUX_HIGHMEM_H

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/cacheflush.h>
#include <linux/kmsan.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>

#include "highmem-internal.h"

/**
 * kmap - Map a page for long term usage
 * @page:	Pointer to the page to be mapped
 *
 * Returns: The virtual address of the mapping
 *
 * Can only be invoked from preemptible task context because on 32bit
 * systems with CONFIG_HIGHMEM enabled this function might sleep.
 *
 * For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
 * this returns the virtual address of the direct kernel mapping.
 *
 * The returned virtual address is globally visible and valid up to the
 * point where it is unmapped via kunmap(). The pointer can be handed to
 * other contexts.
 *
 * For highmem pages on 32bit systems this can be slow as the mapping space
 * is limited and protected by a global lock. In case that there is no
 * mapping slot available the function blocks until a slot is released via
 * kunmap().
 */
static inline void *kmap(struct page *page);

/**
 * kunmap - Unmap the virtual address mapped by kmap()
 * @page:	Pointer to the page which was mapped by kmap()
 *
 * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
 * pages in the low memory area.
 */
static inline void kunmap(struct page *page);

/**
 * kmap_to_page - Get the page for a kmap'ed address
 * @addr:	The address to look up
 *
 * Returns: The page which is mapped to @addr.
 */
static inline struct page *kmap_to_page(void *addr);

/**
 * kmap_flush_unused - Flush all unused kmap mappings in order to
 *		       remove stray mappings
 */
static inline void kmap_flush_unused(void);

/**
 * kmap_local_page - Map a page for temporary usage
 * @page: Pointer to the page to be mapped
 *
 * Returns: The virtual address of the mapping
 *
 * Can be invoked from any context, including interrupts.
 *
 * Requires careful handling when nesting multiple mappings because the map
 * management is stack based. The unmap has to be in the reverse order of
 * the map operation:
 *
 * addr1 = kmap_local_page(page1);
 * addr2 = kmap_local_page(page2);
 * ...
 * kunmap_local(addr2);
 * kunmap_local(addr1);
 *
 * Unmapping addr1 before addr2 is invalid and causes malfunction.
 *
 * Contrary to kmap() mappings the mapping is only valid in the context of
 * the caller and cannot be handed to other contexts.
 *
 * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
 * virtual address of the direct mapping. Only real highmem pages are
 * temporarily mapped.
 *
 * While kmap_local_page() is significantly faster than kmap() for the highmem
 * case it comes with restrictions about the pointer validity.
 *
 * On HIGHMEM enabled systems mapping a highmem page has the side effect of
 * disabling migration in order to keep the virtual address stable across
 * preemption. No caller of kmap_local_page() can rely on this side effect.
 */
static inline void *kmap_local_page(struct page *page);

/**
 * kmap_local_folio - Map a page in this folio for temporary usage
 * @folio: The folio containing the page.
 * @offset: The byte offset within the folio which identifies the page.
 *
 * Requires careful handling when nesting multiple mappings because the map
 * management is stack based. The unmap has to be in the reverse order of
 * the map operation::
 *
 *   addr1 = kmap_local_folio(folio1, offset1);
 *   addr2 = kmap_local_folio(folio2, offset2);
 *   ...
 *   kunmap_local(addr2);
 *   kunmap_local(addr1);
 *
 * Unmapping addr1 before addr2 is invalid and causes malfunction.
 *
 * Contrary to kmap() mappings the mapping is only valid in the context of
 * the caller and cannot be handed to other contexts.
 *
 * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
 * virtual address of the direct mapping. Only real highmem pages are
 * temporarily mapped.
 *
 * While it is significantly faster than kmap() for the highmem case it
 * comes with restrictions about the pointer validity.
 *
 * On HIGHMEM enabled systems mapping a highmem page has the side effect of
 * disabling migration in order to keep the virtual address stable across
 * preemption. No caller of kmap_local_folio() can rely on this side effect.
 *
 * Context: Can be invoked from any context.
 * Return: The virtual address of @offset.
 */
static inline void *kmap_local_folio(struct folio *folio, size_t offset);

/**
 * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
 * @page:	Pointer to the page to be mapped
 *
 * Returns: The virtual address of the mapping
 *
 * In fact a wrapper around kmap_local_page() which also disables pagefaults
 * and, depending on PREEMPT_RT configuration, also CPU migration and
 * preemption. Therefore users should not count on the latter two side effects.
 *
 * Mappings should always be released by kunmap_atomic().
 *
 * Do not use in new code. Use kmap_local_page() instead.
 *
 * It is used in atomic context when code wants to access the contents of a
 * page that might be allocated from high memory (see __GFP_HIGHMEM), for
 * example a page in the pagecache.  The API has two functions, and they
 * can be used in a manner similar to the following::
 *
 *   // Find the page of interest.
 *   struct page *page = find_get_page(mapping, offset);
 *
 *   // Gain access to the contents of that page.
 *   void *vaddr = kmap_atomic(page);
 *
 *   // Do something to the contents of that page.
 *   memset(vaddr, 0, PAGE_SIZE);
 *
 *   // Unmap that page.
 *   kunmap_atomic(vaddr);
 *
 * Note that the kunmap_atomic() call takes the result of the kmap_atomic()
 * call, not the argument.
 *
 * If you need to map two pages because you want to copy from one page to
 * another you need to keep the kmap_atomic calls strictly nested, like:
 *
 * vaddr1 = kmap_atomic(page1);
 * vaddr2 = kmap_atomic(page2);
 *
 * memcpy(vaddr1, vaddr2, PAGE_SIZE);
 *
 * kunmap_atomic(vaddr2);
 * kunmap_atomic(vaddr1);
 */
static inline void *kmap_atomic(struct page *page);

/* Highmem related interfaces for management code */
static inline unsigned int nr_free_highpages(void);
static inline unsigned long totalhigh_pages(void);

#ifndef ARCH_HAS_FLUSH_ANON_PAGE
static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
{
}
#endif

#ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
static inline void flush_kernel_vmap_range(void *vaddr, int size)
{
}
static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
{
}
#endif

/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
{
	void *addr = kmap_local_page(page);
	clear_user_page(addr, vaddr, page);
	kunmap_local(addr);
}
#endif

#ifndef vma_alloc_zeroed_movable_folio
/**
 * vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA.
 * @vma: The VMA the page is to be allocated for.
 * @vaddr: The virtual address the page will be inserted into.
 *
 * This function will allocate a page suitable for inserting into this
 * VMA at this virtual address.  It may be allocated from highmem or
 * the movable zone.  An architecture may provide its own implementation.
 *
 * Return: A folio containing one allocated and zeroed page or NULL if
 * we are out of memory.
 */
static inline
struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,
				   unsigned long vaddr)
{
	struct folio *folio;

	folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, false);
	if (folio)
		clear_user_highpage(&folio->page, vaddr);

	return folio;
}
#endif

static inline void clear_highpage(struct page *page)
{
	void *kaddr = kmap_local_page(page);
	clear_page(kaddr);
	kunmap_local(kaddr);
}

static inline void clear_highpage_kasan_tagged(struct page *page)
{
	void *kaddr = kmap_local_page(page);

	clear_page(kasan_reset_tag(kaddr));
	kunmap_local(kaddr);
}

#ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE

static inline void tag_clear_highpage(struct page *page)
{
}

#endif

/*
 * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
 * If we pass in a head page, we can zero up to the size of the compound page.
 */
#ifdef CONFIG_HIGHMEM
void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
		unsigned start2, unsigned end2);
#else
static inline void zero_user_segments(struct page *page,
		unsigned start1, unsigned end1,
		unsigned start2, unsigned end2)
{
	void *kaddr = kmap_local_page(page);
	unsigned int i;

	BUG_ON(end1 > page_size(page) || end2 > page_size(page));

	if (end1 > start1)
		memset(kaddr + start1, 0, end1 - start1);

	if (end2 > start2)
		memset(kaddr + start2, 0, end2 - start2);

	kunmap_local(kaddr);
	for (i = 0; i < compound_nr(page); i++)
		flush_dcache_page(page + i);
}
#endif

static inline void zero_user_segment(struct page *page,
	unsigned start, unsigned end)
{
	zero_user_segments(page, start, end, 0, 0);
}

static inline void zero_user(struct page *page,
	unsigned start, unsigned size)
{
	zero_user_segments(page, start, start + size, 0, 0);
}

#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE

static inline void copy_user_highpage(struct page *to, struct page *from,
	unsigned long vaddr, struct vm_area_struct *vma)
{
	char *vfrom, *vto;

	vfrom = kmap_local_page(from);
	vto = kmap_local_page(to);
	copy_user_page(vto, vfrom, vaddr, to);
	kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
	kunmap_local(vto);
	kunmap_local(vfrom);
}

#endif

#ifndef __HAVE_ARCH_COPY_HIGHPAGE

static inline void copy_highpage(struct page *to, struct page *from)
{
	char *vfrom, *vto;

	vfrom = kmap_local_page(from);
	vto = kmap_local_page(to);
	copy_page(vto, vfrom);
	kmsan_copy_page_meta(to, from);
	kunmap_local(vto);
	kunmap_local(vfrom);
}

#endif

#ifdef copy_mc_to_kernel
/*
 * If architecture supports machine check exception handling, define the
 * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
 * page with #MC in source page (@from) handled, and return the number
 * of bytes not copied if there was a #MC, otherwise 0 for success.
 */
static inline int copy_mc_user_highpage(struct page *to, struct page *from,
					unsigned long vaddr, struct vm_area_struct *vma)
{
	unsigned long ret;
	char *vfrom, *vto;

	vfrom = kmap_local_page(from);
	vto = kmap_local_page(to);
	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
	if (!ret)
		kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
	kunmap_local(vto);
	kunmap_local(vfrom);

	return ret;
}

static inline int copy_mc_highpage(struct page *to, struct page *from)
{
	unsigned long ret;
	char *vfrom, *vto;

	vfrom = kmap_local_page(from);
	vto = kmap_local_page(to);
	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
	if (!ret)
		kmsan_copy_page_meta(to, from);
	kunmap_local(vto);
	kunmap_local(vfrom);

	return ret;
}
#else
static inline int copy_mc_user_highpage(struct page *to, struct page *from,
					unsigned long vaddr, struct vm_area_struct *vma)
{
	copy_user_highpage(to, from, vaddr, vma);
	return 0;
}

static inline int copy_mc_highpage(struct page *to, struct page *from)
{
	copy_highpage(to, from);
	return 0;
}
#endif

static inline void memcpy_page(struct page *dst_page, size_t dst_off,
			       struct page *src_page, size_t src_off,
			       size_t len)
{
	char *dst = kmap_local_page(dst_page);
	char *src = kmap_local_page(src_page);

	VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
	memcpy(dst + dst_off, src + src_off, len);
	kunmap_local(src);
	kunmap_local(dst);
}

static inline void memset_page(struct page *page, size_t offset, int val,
			       size_t len)
{
	char *addr = kmap_local_page(page);

	VM_BUG_ON(offset + len > PAGE_SIZE);
	memset(addr + offset, val, len);
	kunmap_local(addr);
}

static inline void memcpy_from_page(char *to, struct page *page,
				    size_t offset, size_t len)
{
	char *from = kmap_local_page(page);

	VM_BUG_ON(offset + len > PAGE_SIZE);
	memcpy(to, from + offset, len);
	kunmap_local(from);
}

static inline void memcpy_to_page(struct page *page, size_t offset,
				  const char *from, size_t len)
{
	char *to = kmap_local_page(page);

	VM_BUG_ON(offset + len > PAGE_SIZE);
	memcpy(to + offset, from, len);
	flush_dcache_page(page);
	kunmap_local(to);
}

static inline void memzero_page(struct page *page, size_t offset, size_t len)
{
	char *addr = kmap_local_page(page);

	VM_BUG_ON(offset + len > PAGE_SIZE);
	memset(addr + offset, 0, len);
	flush_dcache_page(page);
	kunmap_local(addr);
}

static inline void memcpy_from_folio(char *to, struct folio *folio,
		size_t offset, size_t len)
{
	VM_BUG_ON(offset + len > folio_size(folio));

	do {
		const char *from = kmap_local_folio(folio, offset);
		size_t chunk = len;

		if (folio_test_highmem(folio) &&
		    chunk > PAGE_SIZE - offset_in_page(offset))
			chunk = PAGE_SIZE - offset_in_page(offset);
		memcpy(to, from, chunk);
		kunmap_local(from);

		from += chunk;
		offset += chunk;
		len -= chunk;
	} while (len > 0);
}

static inline void memcpy_to_folio(struct folio *folio, size_t offset,
		const char *from, size_t len)
{
	VM_BUG_ON(offset + len > folio_size(folio));

	do {
		char *to = kmap_local_folio(folio, offset);
		size_t chunk = len;

		if (folio_test_highmem(folio) &&
		    chunk > PAGE_SIZE - offset_in_page(offset))
			chunk = PAGE_SIZE - offset_in_page(offset);
		memcpy(to, from, chunk);
		kunmap_local(to);

		from += chunk;
		offset += chunk;
		len -= chunk;
	} while (len > 0);

	flush_dcache_folio(folio);
}

/**
 * memcpy_from_file_folio - Copy some bytes from a file folio.
 * @to: The destination buffer.
 * @folio: The folio to copy from.
 * @pos: The position in the file.
 * @len: The maximum number of bytes to copy.
 *
 * Copy up to @len bytes from this folio.  This may be limited by PAGE_SIZE
 * if the folio comes from HIGHMEM, and by the size of the folio.
 *
 * Return: The number of bytes copied from the folio.
 */
static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
		loff_t pos, size_t len)
{
	size_t offset = offset_in_folio(folio, pos);
	char *from = kmap_local_folio(folio, offset);

	if (folio_test_highmem(folio)) {
		offset = offset_in_page(offset);
		len = min_t(size_t, len, PAGE_SIZE - offset);
	} else
		len = min(len, folio_size(folio) - offset);

	memcpy(to, from, len);
	kunmap_local(from);

	return len;
}

/**
 * folio_zero_segments() - Zero two byte ranges in a folio.
 * @folio: The folio to write to.
 * @start1: The first byte to zero.
 * @xend1: One more than the last byte in the first range.
 * @start2: The first byte to zero in the second range.
 * @xend2: One more than the last byte in the second range.
 */
static inline void folio_zero_segments(struct folio *folio,
		size_t start1, size_t xend1, size_t start2, size_t xend2)
{
	zero_user_segments(&folio->page, start1, xend1, start2, xend2);
}

/**
 * folio_zero_segment() - Zero a byte range in a folio.
 * @folio: The folio to write to.
 * @start: The first byte to zero.
 * @xend: One more than the last byte to zero.
 */
static inline void folio_zero_segment(struct folio *folio,
		size_t start, size_t xend)
{
	zero_user_segments(&folio->page, start, xend, 0, 0);
}

/**
 * folio_zero_range() - Zero a byte range in a folio.
 * @folio: The folio to write to.
 * @start: The first byte to zero.
 * @length: The number of bytes to zero.
 */
static inline void folio_zero_range(struct folio *folio,
		size_t start, size_t length)
{
	zero_user_segments(&folio->page, start, start + length, 0, 0);
}

/**
 * folio_release_kmap - Unmap a folio and drop a refcount.
 * @folio: The folio to release.
 * @addr: The address previously returned by a call to kmap_local_folio().
 *
 * It is common, eg in directory handling to kmap a folio.  This function
 * unmaps the folio and drops the refcount that was being held to keep the
 * folio alive while we accessed it.
 */
static inline void folio_release_kmap(struct folio *folio, void *addr)
{
	kunmap_local(addr);
	folio_put(folio);
}

static inline void unmap_and_put_page(struct page *page, void *addr)
{
	folio_release_kmap(page_folio(page), addr);
}

#endif /* _LINUX_HIGHMEM_H */