1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_HIGHMEM_H
3 #define _LINUX_HIGHMEM_H
4 
5 #include <linux/fs.h>
6 #include <linux/kernel.h>
7 #include <linux/bug.h>
8 #include <linux/cacheflush.h>
9 #include <linux/kmsan.h>
10 #include <linux/mm.h>
11 #include <linux/uaccess.h>
12 #include <linux/hardirq.h>
13 
14 #include "highmem-internal.h"
15 
16 /**
17  * kmap - Map a page for long term usage
18  * @page:	Pointer to the page to be mapped
19  *
20  * Returns: The virtual address of the mapping
21  *
22  * Can only be invoked from preemptible task context because on 32bit
23  * systems with CONFIG_HIGHMEM enabled this function might sleep.
24  *
25  * For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
26  * this returns the virtual address of the direct kernel mapping.
27  *
28  * The returned virtual address is globally visible and valid up to the
29  * point where it is unmapped via kunmap(). The pointer can be handed to
30  * other contexts.
31  *
32  * For highmem pages on 32bit systems this can be slow as the mapping space
33  * is limited and protected by a global lock. In case that there is no
34  * mapping slot available the function blocks until a slot is released via
35  * kunmap().
36  */
37 static inline void *kmap(struct page *page);
38 
39 /**
40  * kunmap - Unmap the virtual address mapped by kmap()
41  * @page:	Pointer to the page which was mapped by kmap()
42  *
43  * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
44  * pages in the low memory area.
45  */
46 static inline void kunmap(struct page *page);
47 
48 /**
49  * kmap_to_page - Get the page for a kmap'ed address
50  * @addr:	The address to look up
51  *
52  * Returns: The page which is mapped to @addr.
53  */
54 static inline struct page *kmap_to_page(void *addr);
55 
56 /**
57  * kmap_flush_unused - Flush all unused kmap mappings in order to
58  *		       remove stray mappings
59  */
60 static inline void kmap_flush_unused(void);
61 
62 /**
63  * kmap_local_page - Map a page for temporary usage
64  * @page: Pointer to the page to be mapped
65  *
66  * Returns: The virtual address of the mapping
67  *
68  * Can be invoked from any context, including interrupts.
69  *
70  * Requires careful handling when nesting multiple mappings because the map
71  * management is stack based. The unmap has to be in the reverse order of
72  * the map operation:
73  *
74  * addr1 = kmap_local_page(page1);
75  * addr2 = kmap_local_page(page2);
76  * ...
77  * kunmap_local(addr2);
78  * kunmap_local(addr1);
79  *
80  * Unmapping addr1 before addr2 is invalid and causes malfunction.
81  *
82  * Contrary to kmap() mappings the mapping is only valid in the context of
83  * the caller and cannot be handed to other contexts.
84  *
85  * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
86  * virtual address of the direct mapping. Only real highmem pages are
87  * temporarily mapped.
88  *
89  * While kmap_local_page() is significantly faster than kmap() for the highmem
90  * case it comes with restrictions about the pointer validity.
91  *
92  * On HIGHMEM enabled systems mapping a highmem page has the side effect of
93  * disabling migration in order to keep the virtual address stable across
94  * preemption. No caller of kmap_local_page() can rely on this side effect.
95  */
96 static inline void *kmap_local_page(struct page *page);
97 
98 /**
99  * kmap_local_folio - Map a page in this folio for temporary usage
100  * @folio: The folio containing the page.
101  * @offset: The byte offset within the folio which identifies the page.
102  *
103  * Requires careful handling when nesting multiple mappings because the map
104  * management is stack based. The unmap has to be in the reverse order of
105  * the map operation::
106  *
107  *   addr1 = kmap_local_folio(folio1, offset1);
108  *   addr2 = kmap_local_folio(folio2, offset2);
109  *   ...
110  *   kunmap_local(addr2);
111  *   kunmap_local(addr1);
112  *
113  * Unmapping addr1 before addr2 is invalid and causes malfunction.
114  *
115  * Contrary to kmap() mappings the mapping is only valid in the context of
116  * the caller and cannot be handed to other contexts.
117  *
118  * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
119  * virtual address of the direct mapping. Only real highmem pages are
120  * temporarily mapped.
121  *
122  * While it is significantly faster than kmap() for the highmem case it
123  * comes with restrictions about the pointer validity.
124  *
125  * On HIGHMEM enabled systems mapping a highmem page has the side effect of
126  * disabling migration in order to keep the virtual address stable across
127  * preemption. No caller of kmap_local_folio() can rely on this side effect.
128  *
129  * Context: Can be invoked from any context.
130  * Return: The virtual address of @offset.
131  */
132 static inline void *kmap_local_folio(struct folio *folio, size_t offset);
133 
134 /**
135  * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
136  * @page:	Pointer to the page to be mapped
137  *
138  * Returns: The virtual address of the mapping
139  *
140  * In fact a wrapper around kmap_local_page() which also disables pagefaults
141  * and, depending on PREEMPT_RT configuration, also CPU migration and
142  * preemption. Therefore users should not count on the latter two side effects.
143  *
144  * Mappings should always be released by kunmap_atomic().
145  *
146  * Do not use in new code. Use kmap_local_page() instead.
147  *
148  * It is used in atomic context when code wants to access the contents of a
149  * page that might be allocated from high memory (see __GFP_HIGHMEM), for
150  * example a page in the pagecache.  The API has two functions, and they
151  * can be used in a manner similar to the following::
152  *
153  *   // Find the page of interest.
154  *   struct page *page = find_get_page(mapping, offset);
155  *
156  *   // Gain access to the contents of that page.
157  *   void *vaddr = kmap_atomic(page);
158  *
159  *   // Do something to the contents of that page.
160  *   memset(vaddr, 0, PAGE_SIZE);
161  *
162  *   // Unmap that page.
163  *   kunmap_atomic(vaddr);
164  *
165  * Note that the kunmap_atomic() call takes the result of the kmap_atomic()
166  * call, not the argument.
167  *
168  * If you need to map two pages because you want to copy from one page to
169  * another you need to keep the kmap_atomic calls strictly nested, like:
170  *
171  * vaddr1 = kmap_atomic(page1);
172  * vaddr2 = kmap_atomic(page2);
173  *
174  * memcpy(vaddr1, vaddr2, PAGE_SIZE);
175  *
176  * kunmap_atomic(vaddr2);
177  * kunmap_atomic(vaddr1);
178  */
179 static inline void *kmap_atomic(struct page *page);
180 
181 /* Highmem related interfaces for management code */
182 static inline unsigned int nr_free_highpages(void);
183 static inline unsigned long totalhigh_pages(void);
184 
185 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
flush_anon_page(struct vm_area_struct * vma,struct page * page,unsigned long vmaddr)186 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
187 {
188 }
189 #endif
190 
191 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
flush_kernel_vmap_range(void * vaddr,int size)192 static inline void flush_kernel_vmap_range(void *vaddr, int size)
193 {
194 }
invalidate_kernel_vmap_range(void * vaddr,int size)195 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
196 {
197 }
198 #endif
199 
200 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
201 #ifndef clear_user_highpage
clear_user_highpage(struct page * page,unsigned long vaddr)202 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
203 {
204 	void *addr = kmap_local_page(page);
205 	clear_user_page(addr, vaddr, page);
206 	kunmap_local(addr);
207 }
208 #endif
209 
210 #ifndef vma_alloc_zeroed_movable_folio
211 /**
212  * vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA.
213  * @vma: The VMA the page is to be allocated for.
214  * @vaddr: The virtual address the page will be inserted into.
215  *
216  * This function will allocate a page suitable for inserting into this
217  * VMA at this virtual address.  It may be allocated from highmem or
218  * the movable zone.  An architecture may provide its own implementation.
219  *
220  * Return: A folio containing one allocated and zeroed page or NULL if
221  * we are out of memory.
222  */
223 static inline
vma_alloc_zeroed_movable_folio(struct vm_area_struct * vma,unsigned long vaddr)224 struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,
225 				   unsigned long vaddr)
226 {
227 	struct folio *folio;
228 
229 	folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, false);
230 	if (folio)
231 		clear_user_highpage(&folio->page, vaddr);
232 
233 	return folio;
234 }
235 #endif
236 
clear_highpage(struct page * page)237 static inline void clear_highpage(struct page *page)
238 {
239 	void *kaddr = kmap_local_page(page);
240 	clear_page(kaddr);
241 	kunmap_local(kaddr);
242 }
243 
clear_highpage_kasan_tagged(struct page * page)244 static inline void clear_highpage_kasan_tagged(struct page *page)
245 {
246 	u8 tag;
247 
248 	tag = page_kasan_tag(page);
249 	page_kasan_tag_reset(page);
250 	clear_highpage(page);
251 	page_kasan_tag_set(page, tag);
252 }
253 
254 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
255 
tag_clear_highpage(struct page * page)256 static inline void tag_clear_highpage(struct page *page)
257 {
258 }
259 
260 #endif
261 
262 /*
263  * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
264  * If we pass in a head page, we can zero up to the size of the compound page.
265  */
266 #ifdef CONFIG_HIGHMEM
267 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
268 		unsigned start2, unsigned end2);
269 #else
zero_user_segments(struct page * page,unsigned start1,unsigned end1,unsigned start2,unsigned end2)270 static inline void zero_user_segments(struct page *page,
271 		unsigned start1, unsigned end1,
272 		unsigned start2, unsigned end2)
273 {
274 	void *kaddr = kmap_local_page(page);
275 	unsigned int i;
276 
277 	BUG_ON(end1 > page_size(page) || end2 > page_size(page));
278 
279 	if (end1 > start1)
280 		memset(kaddr + start1, 0, end1 - start1);
281 
282 	if (end2 > start2)
283 		memset(kaddr + start2, 0, end2 - start2);
284 
285 	kunmap_local(kaddr);
286 	for (i = 0; i < compound_nr(page); i++)
287 		flush_dcache_page(page + i);
288 }
289 #endif
290 
zero_user_segment(struct page * page,unsigned start,unsigned end)291 static inline void zero_user_segment(struct page *page,
292 	unsigned start, unsigned end)
293 {
294 	zero_user_segments(page, start, end, 0, 0);
295 }
296 
zero_user(struct page * page,unsigned start,unsigned size)297 static inline void zero_user(struct page *page,
298 	unsigned start, unsigned size)
299 {
300 	zero_user_segments(page, start, start + size, 0, 0);
301 }
302 
303 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
304 
copy_user_highpage(struct page * to,struct page * from,unsigned long vaddr,struct vm_area_struct * vma)305 static inline void copy_user_highpage(struct page *to, struct page *from,
306 	unsigned long vaddr, struct vm_area_struct *vma)
307 {
308 	char *vfrom, *vto;
309 
310 	vfrom = kmap_local_page(from);
311 	vto = kmap_local_page(to);
312 	copy_user_page(vto, vfrom, vaddr, to);
313 	kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
314 	kunmap_local(vto);
315 	kunmap_local(vfrom);
316 }
317 
318 #endif
319 
320 #ifdef copy_mc_to_kernel
copy_mc_user_highpage(struct page * to,struct page * from,unsigned long vaddr,struct vm_area_struct * vma)321 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
322 					unsigned long vaddr, struct vm_area_struct *vma)
323 {
324 	unsigned long ret;
325 	char *vfrom, *vto;
326 
327 	vfrom = kmap_local_page(from);
328 	vto = kmap_local_page(to);
329 	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
330 	if (!ret)
331 		kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
332 	kunmap_local(vto);
333 	kunmap_local(vfrom);
334 
335 	return ret;
336 }
337 #else
copy_mc_user_highpage(struct page * to,struct page * from,unsigned long vaddr,struct vm_area_struct * vma)338 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
339 					unsigned long vaddr, struct vm_area_struct *vma)
340 {
341 	copy_user_highpage(to, from, vaddr, vma);
342 	return 0;
343 }
344 #endif
345 
346 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
347 
copy_highpage(struct page * to,struct page * from)348 static inline void copy_highpage(struct page *to, struct page *from)
349 {
350 	char *vfrom, *vto;
351 
352 	vfrom = kmap_local_page(from);
353 	vto = kmap_local_page(to);
354 	copy_page(vto, vfrom);
355 	kmsan_copy_page_meta(to, from);
356 	kunmap_local(vto);
357 	kunmap_local(vfrom);
358 }
359 
360 #endif
361 
memcpy_page(struct page * dst_page,size_t dst_off,struct page * src_page,size_t src_off,size_t len)362 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
363 			       struct page *src_page, size_t src_off,
364 			       size_t len)
365 {
366 	char *dst = kmap_local_page(dst_page);
367 	char *src = kmap_local_page(src_page);
368 
369 	VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
370 	memcpy(dst + dst_off, src + src_off, len);
371 	kunmap_local(src);
372 	kunmap_local(dst);
373 }
374 
memset_page(struct page * page,size_t offset,int val,size_t len)375 static inline void memset_page(struct page *page, size_t offset, int val,
376 			       size_t len)
377 {
378 	char *addr = kmap_local_page(page);
379 
380 	VM_BUG_ON(offset + len > PAGE_SIZE);
381 	memset(addr + offset, val, len);
382 	kunmap_local(addr);
383 }
384 
memcpy_from_page(char * to,struct page * page,size_t offset,size_t len)385 static inline void memcpy_from_page(char *to, struct page *page,
386 				    size_t offset, size_t len)
387 {
388 	char *from = kmap_local_page(page);
389 
390 	VM_BUG_ON(offset + len > PAGE_SIZE);
391 	memcpy(to, from + offset, len);
392 	kunmap_local(from);
393 }
394 
memcpy_to_page(struct page * page,size_t offset,const char * from,size_t len)395 static inline void memcpy_to_page(struct page *page, size_t offset,
396 				  const char *from, size_t len)
397 {
398 	char *to = kmap_local_page(page);
399 
400 	VM_BUG_ON(offset + len > PAGE_SIZE);
401 	memcpy(to + offset, from, len);
402 	flush_dcache_page(page);
403 	kunmap_local(to);
404 }
405 
memzero_page(struct page * page,size_t offset,size_t len)406 static inline void memzero_page(struct page *page, size_t offset, size_t len)
407 {
408 	char *addr = kmap_local_page(page);
409 
410 	VM_BUG_ON(offset + len > PAGE_SIZE);
411 	memset(addr + offset, 0, len);
412 	flush_dcache_page(page);
413 	kunmap_local(addr);
414 }
415 
416 /**
417  * memcpy_from_file_folio - Copy some bytes from a file folio.
418  * @to: The destination buffer.
419  * @folio: The folio to copy from.
420  * @pos: The position in the file.
421  * @len: The maximum number of bytes to copy.
422  *
423  * Copy up to @len bytes from this folio.  This may be limited by PAGE_SIZE
424  * if the folio comes from HIGHMEM, and by the size of the folio.
425  *
426  * Return: The number of bytes copied from the folio.
427  */
memcpy_from_file_folio(char * to,struct folio * folio,loff_t pos,size_t len)428 static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
429 		loff_t pos, size_t len)
430 {
431 	size_t offset = offset_in_folio(folio, pos);
432 	char *from = kmap_local_folio(folio, offset);
433 
434 	if (folio_test_highmem(folio)) {
435 		offset = offset_in_page(offset);
436 		len = min_t(size_t, len, PAGE_SIZE - offset);
437 	} else
438 		len = min(len, folio_size(folio) - offset);
439 
440 	memcpy(to, from, len);
441 	kunmap_local(from);
442 
443 	return len;
444 }
445 
446 /**
447  * folio_zero_segments() - Zero two byte ranges in a folio.
448  * @folio: The folio to write to.
449  * @start1: The first byte to zero.
450  * @xend1: One more than the last byte in the first range.
451  * @start2: The first byte to zero in the second range.
452  * @xend2: One more than the last byte in the second range.
453  */
folio_zero_segments(struct folio * folio,size_t start1,size_t xend1,size_t start2,size_t xend2)454 static inline void folio_zero_segments(struct folio *folio,
455 		size_t start1, size_t xend1, size_t start2, size_t xend2)
456 {
457 	zero_user_segments(&folio->page, start1, xend1, start2, xend2);
458 }
459 
460 /**
461  * folio_zero_segment() - Zero a byte range in a folio.
462  * @folio: The folio to write to.
463  * @start: The first byte to zero.
464  * @xend: One more than the last byte to zero.
465  */
folio_zero_segment(struct folio * folio,size_t start,size_t xend)466 static inline void folio_zero_segment(struct folio *folio,
467 		size_t start, size_t xend)
468 {
469 	zero_user_segments(&folio->page, start, xend, 0, 0);
470 }
471 
472 /**
473  * folio_zero_range() - Zero a byte range in a folio.
474  * @folio: The folio to write to.
475  * @start: The first byte to zero.
476  * @length: The number of bytes to zero.
477  */
folio_zero_range(struct folio * folio,size_t start,size_t length)478 static inline void folio_zero_range(struct folio *folio,
479 		size_t start, size_t length)
480 {
481 	zero_user_segments(&folio->page, start, start + length, 0, 0);
482 }
483 
put_and_unmap_page(struct page * page,void * addr)484 static inline void put_and_unmap_page(struct page *page, void *addr)
485 {
486 	kunmap_local(addr);
487 	put_page(page);
488 }
489 
490 #endif /* _LINUX_HIGHMEM_H */
491