1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_HIGHMEM_H
3 #define _LINUX_HIGHMEM_H
6 #include <linux/kernel.h>
8 #include <linux/cacheflush.h>
10 #include <linux/uaccess.h>
11 #include <linux/hardirq.h>
13 #include "highmem-internal.h"
16 * kmap - Map a page for long term usage
17 * @page: Pointer to the page to be mapped
19 * Returns: The virtual address of the mapping
21 * Can only be invoked from preemptible task context because on 32bit
22 * systems with CONFIG_HIGHMEM enabled this function might sleep.
24 * For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
25 * this returns the virtual address of the direct kernel mapping.
27 * The returned virtual address is globally visible and valid up to the
28 * point where it is unmapped via kunmap(). The pointer can be handed to
31 * For highmem pages on 32bit systems this can be slow as the mapping space
32 * is limited and protected by a global lock. In case that there is no
33 * mapping slot available the function blocks until a slot is released via
36 static inline void *kmap(struct page *page);
39 * kunmap - Unmap the virtual address mapped by kmap()
40 * @addr: Virtual address to be unmapped
42 * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
43 * pages in the low memory area.
45 static inline void kunmap(struct page *page);
48 * kmap_to_page - Get the page for a kmap'ed address
49 * @addr: The address to look up
51 * Returns: The page which is mapped to @addr.
53 static inline struct page *kmap_to_page(void *addr);
56 * kmap_flush_unused - Flush all unused kmap mappings in order to
57 * remove stray mappings
59 static inline void kmap_flush_unused(void);
62 * kmap_local_page - Map a page for temporary usage
63 * @page: Pointer to the page to be mapped
65 * Returns: The virtual address of the mapping
67 * Can be invoked from any context.
69 * Requires careful handling when nesting multiple mappings because the map
70 * management is stack based. The unmap has to be in the reverse order of
73 * addr1 = kmap_local_page(page1);
74 * addr2 = kmap_local_page(page2);
76 * kunmap_local(addr2);
77 * kunmap_local(addr1);
79 * Unmapping addr1 before addr2 is invalid and causes malfunction.
81 * Contrary to kmap() mappings the mapping is only valid in the context of
82 * the caller and cannot be handed to other contexts.
84 * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
85 * virtual address of the direct mapping. Only real highmem pages are
88 * While it is significantly faster than kmap() for the higmem case it
89 * comes with restrictions about the pointer validity. Only use when really
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.
96 static inline void *kmap_local_page(struct page *page);
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.
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::
107 * addr1 = kmap_local_folio(folio1, offset1);
108 * addr2 = kmap_local_folio(folio2, offset2);
110 * kunmap_local(addr2);
111 * kunmap_local(addr1);
113 * Unmapping addr1 before addr2 is invalid and causes malfunction.
115 * Contrary to kmap() mappings the mapping is only valid in the context of
116 * the caller and cannot be handed to other contexts.
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.
122 * While it is significantly faster than kmap() for the higmem case it
123 * comes with restrictions about the pointer validity. Only use when really
126 * On HIGHMEM enabled systems mapping a highmem page has the side effect of
127 * disabling migration in order to keep the virtual address stable across
128 * preemption. No caller of kmap_local_folio() can rely on this side effect.
130 * Context: Can be invoked from any context.
131 * Return: The virtual address of @offset.
133 static inline void *kmap_local_folio(struct folio *folio, size_t offset);
136 * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
137 * @page: Pointer to the page to be mapped
139 * Returns: The virtual address of the mapping
141 * Effectively a wrapper around kmap_local_page() which disables pagefaults
144 * Do not use in new code. Use kmap_local_page() instead.
146 static inline void *kmap_atomic(struct page *page);
149 * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic()
150 * @addr: Virtual address to be unmapped
152 * Counterpart to kmap_atomic().
154 * Effectively a wrapper around kunmap_local() which additionally undoes
155 * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
159 /* Highmem related interfaces for management code */
160 static inline unsigned int nr_free_highpages(void);
161 static inline unsigned long totalhigh_pages(void);
163 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
164 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
169 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
170 static inline void flush_kernel_vmap_range(void *vaddr, int size)
173 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
178 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
179 #ifndef clear_user_highpage
180 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
182 void *addr = kmap_local_page(page);
183 clear_user_page(addr, vaddr, page);
188 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
190 * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
191 * @vma: The VMA the page is to be allocated for
192 * @vaddr: The virtual address the page will be inserted into
194 * This function will allocate a page for a VMA that the caller knows will
195 * be able to migrate in the future using move_pages() or reclaimed
197 * An architecture may override this function by defining
198 * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
201 static inline struct page *
202 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
205 struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
208 clear_user_highpage(page, vaddr);
214 static inline void clear_highpage(struct page *page)
216 void *kaddr = kmap_local_page(page);
221 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
223 static inline void tag_clear_highpage(struct page *page)
230 * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
231 * If we pass in a head page, we can zero up to the size of the compound page.
233 #ifdef CONFIG_HIGHMEM
234 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
235 unsigned start2, unsigned end2);
237 static inline void zero_user_segments(struct page *page,
238 unsigned start1, unsigned end1,
239 unsigned start2, unsigned end2)
241 void *kaddr = kmap_local_page(page);
244 BUG_ON(end1 > page_size(page) || end2 > page_size(page));
247 memset(kaddr + start1, 0, end1 - start1);
250 memset(kaddr + start2, 0, end2 - start2);
253 for (i = 0; i < compound_nr(page); i++)
254 flush_dcache_page(page + i);
258 static inline void zero_user_segment(struct page *page,
259 unsigned start, unsigned end)
261 zero_user_segments(page, start, end, 0, 0);
264 static inline void zero_user(struct page *page,
265 unsigned start, unsigned size)
267 zero_user_segments(page, start, start + size, 0, 0);
270 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
272 static inline void copy_user_highpage(struct page *to, struct page *from,
273 unsigned long vaddr, struct vm_area_struct *vma)
277 vfrom = kmap_local_page(from);
278 vto = kmap_local_page(to);
279 copy_user_page(vto, vfrom, vaddr, to);
286 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
288 static inline void copy_highpage(struct page *to, struct page *from)
292 vfrom = kmap_local_page(from);
293 vto = kmap_local_page(to);
294 copy_page(vto, vfrom);
301 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
302 struct page *src_page, size_t src_off,
305 char *dst = kmap_local_page(dst_page);
306 char *src = kmap_local_page(src_page);
308 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
309 memcpy(dst + dst_off, src + src_off, len);
314 static inline void memmove_page(struct page *dst_page, size_t dst_off,
315 struct page *src_page, size_t src_off,
318 char *dst = kmap_local_page(dst_page);
319 char *src = kmap_local_page(src_page);
321 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
322 memmove(dst + dst_off, src + src_off, len);
327 static inline void memset_page(struct page *page, size_t offset, int val,
330 char *addr = kmap_local_page(page);
332 VM_BUG_ON(offset + len > PAGE_SIZE);
333 memset(addr + offset, val, len);
337 static inline void memcpy_from_page(char *to, struct page *page,
338 size_t offset, size_t len)
340 char *from = kmap_local_page(page);
342 VM_BUG_ON(offset + len > PAGE_SIZE);
343 memcpy(to, from + offset, len);
347 static inline void memcpy_to_page(struct page *page, size_t offset,
348 const char *from, size_t len)
350 char *to = kmap_local_page(page);
352 VM_BUG_ON(offset + len > PAGE_SIZE);
353 memcpy(to + offset, from, len);
354 flush_dcache_page(page);
358 static inline void memzero_page(struct page *page, size_t offset, size_t len)
360 char *addr = kmap_local_page(page);
361 memset(addr + offset, 0, len);
362 flush_dcache_page(page);
367 * folio_zero_segments() - Zero two byte ranges in a folio.
368 * @folio: The folio to write to.
369 * @start1: The first byte to zero.
370 * @xend1: One more than the last byte in the first range.
371 * @start2: The first byte to zero in the second range.
372 * @xend2: One more than the last byte in the second range.
374 static inline void folio_zero_segments(struct folio *folio,
375 size_t start1, size_t xend1, size_t start2, size_t xend2)
377 zero_user_segments(&folio->page, start1, xend1, start2, xend2);
381 * folio_zero_segment() - Zero a byte range in a folio.
382 * @folio: The folio to write to.
383 * @start: The first byte to zero.
384 * @xend: One more than the last byte to zero.
386 static inline void folio_zero_segment(struct folio *folio,
387 size_t start, size_t xend)
389 zero_user_segments(&folio->page, start, xend, 0, 0);
393 * folio_zero_range() - Zero a byte range in a folio.
394 * @folio: The folio to write to.
395 * @start: The first byte to zero.
396 * @length: The number of bytes to zero.
398 static inline void folio_zero_range(struct folio *folio,
399 size_t start, size_t length)
401 zero_user_segments(&folio->page, start, start + length, 0, 0);
404 #endif /* _LINUX_HIGHMEM_H */