1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_HIGHMEM_H
3 #define _LINUX_HIGHMEM_H
6 #include <linux/kernel.h>
9 #include <linux/uaccess.h>
10 #include <linux/hardirq.h>
12 #include <asm/cacheflush.h>
14 #include "highmem-internal.h"
17 * kmap - Map a page for long term usage
18 * @page: Pointer to the page to be mapped
20 * Returns: The virtual address of the mapping
22 * Can only be invoked from preemptible task context because on 32bit
23 * systems with CONFIG_HIGHMEM enabled this function might sleep.
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.
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
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
37 static inline void *kmap(struct page *page);
40 * kunmap - Unmap the virtual address mapped by kmap()
41 * @addr: Virtual address to be unmapped
43 * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
44 * pages in the low memory area.
46 static inline void kunmap(struct page *page);
49 * kmap_to_page - Get the page for a kmap'ed address
50 * @addr: The address to look up
52 * Returns: The page which is mapped to @addr.
54 static inline struct page *kmap_to_page(void *addr);
57 * kmap_flush_unused - Flush all unused kmap mappings in order to
58 * remove stray mappings
60 static inline void kmap_flush_unused(void);
63 * kmap_local_page - Map a page for temporary usage
64 * @page: Pointer to the page to be mapped
66 * Returns: The virtual address of the mapping
68 * Can be invoked from any context.
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
74 * addr1 = kmap_local_page(page1);
75 * addr2 = kmap_local_page(page2);
77 * kunmap_local(addr2);
78 * kunmap_local(addr1);
80 * Unmapping addr1 before addr2 is invalid and causes malfunction.
82 * Contrary to kmap() mappings the mapping is only valid in the context of
83 * the caller and cannot be handed to other contexts.
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
89 * While it is significantly faster than kmap() for the higmem case it
90 * comes with restrictions about the pointer validity. Only use when really
93 * On HIGHMEM enabled systems mapping a highmem page has the side effect of
94 * disabling migration in order to keep the virtual address stable across
95 * preemption. No caller of kmap_local_page() can rely on this side effect.
97 static inline void *kmap_local_page(struct page *page);
100 * kmap_local_folio - Map a page in this folio for temporary usage
101 * @folio: The folio containing the page.
102 * @offset: The byte offset within the folio which identifies the page.
104 * Requires careful handling when nesting multiple mappings because the map
105 * management is stack based. The unmap has to be in the reverse order of
106 * the map operation::
108 * addr1 = kmap_local_folio(folio1, offset1);
109 * addr2 = kmap_local_folio(folio2, offset2);
111 * kunmap_local(addr2);
112 * kunmap_local(addr1);
114 * Unmapping addr1 before addr2 is invalid and causes malfunction.
116 * Contrary to kmap() mappings the mapping is only valid in the context of
117 * the caller and cannot be handed to other contexts.
119 * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
120 * virtual address of the direct mapping. Only real highmem pages are
121 * temporarily mapped.
123 * While it is significantly faster than kmap() for the higmem case it
124 * comes with restrictions about the pointer validity. Only use when really
127 * On HIGHMEM enabled systems mapping a highmem page has the side effect of
128 * disabling migration in order to keep the virtual address stable across
129 * preemption. No caller of kmap_local_folio() can rely on this side effect.
131 * Context: Can be invoked from any context.
132 * Return: The virtual address of @offset.
134 static inline void *kmap_local_folio(struct folio *folio, size_t offset);
137 * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
138 * @page: Pointer to the page to be mapped
140 * Returns: The virtual address of the mapping
142 * Effectively a wrapper around kmap_local_page() which disables pagefaults
145 * Do not use in new code. Use kmap_local_page() instead.
147 static inline void *kmap_atomic(struct page *page);
150 * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic()
151 * @addr: Virtual address to be unmapped
153 * Counterpart to kmap_atomic().
155 * Effectively a wrapper around kunmap_local() which additionally undoes
156 * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
160 /* Highmem related interfaces for management code */
161 static inline unsigned int nr_free_highpages(void);
162 static inline unsigned long totalhigh_pages(void);
164 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
165 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
170 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
171 static inline void flush_kernel_vmap_range(void *vaddr, int size)
174 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
179 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
180 #ifndef clear_user_highpage
181 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
183 void *addr = kmap_local_page(page);
184 clear_user_page(addr, vaddr, page);
189 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
191 * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
192 * @vma: The VMA the page is to be allocated for
193 * @vaddr: The virtual address the page will be inserted into
195 * This function will allocate a page for a VMA that the caller knows will
196 * be able to migrate in the future using move_pages() or reclaimed
198 * An architecture may override this function by defining
199 * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
202 static inline struct page *
203 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
206 struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
209 clear_user_highpage(page, vaddr);
215 static inline void clear_highpage(struct page *page)
217 void *kaddr = kmap_local_page(page);
222 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
224 static inline void tag_clear_highpage(struct page *page)
231 * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
232 * If we pass in a head page, we can zero up to the size of the compound page.
234 #if defined(CONFIG_HIGHMEM) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
235 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
236 unsigned start2, unsigned end2);
237 #else /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
238 static inline void zero_user_segments(struct page *page,
239 unsigned start1, unsigned end1,
240 unsigned start2, unsigned end2)
242 void *kaddr = kmap_local_page(page);
245 BUG_ON(end1 > page_size(page) || end2 > page_size(page));
248 memset(kaddr + start1, 0, end1 - start1);
251 memset(kaddr + start2, 0, end2 - start2);
254 for (i = 0; i < compound_nr(page); i++)
255 flush_dcache_page(page + i);
257 #endif /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
259 static inline void zero_user_segment(struct page *page,
260 unsigned start, unsigned end)
262 zero_user_segments(page, start, end, 0, 0);
265 static inline void zero_user(struct page *page,
266 unsigned start, unsigned size)
268 zero_user_segments(page, start, start + size, 0, 0);
271 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
273 static inline void copy_user_highpage(struct page *to, struct page *from,
274 unsigned long vaddr, struct vm_area_struct *vma)
278 vfrom = kmap_local_page(from);
279 vto = kmap_local_page(to);
280 copy_user_page(vto, vfrom, vaddr, to);
287 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
289 static inline void copy_highpage(struct page *to, struct page *from)
293 vfrom = kmap_local_page(from);
294 vto = kmap_local_page(to);
295 copy_page(vto, vfrom);
302 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
303 struct page *src_page, size_t src_off,
306 char *dst = kmap_local_page(dst_page);
307 char *src = kmap_local_page(src_page);
309 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
310 memcpy(dst + dst_off, src + src_off, len);
315 static inline void memmove_page(struct page *dst_page, size_t dst_off,
316 struct page *src_page, size_t src_off,
319 char *dst = kmap_local_page(dst_page);
320 char *src = kmap_local_page(src_page);
322 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
323 memmove(dst + dst_off, src + src_off, len);
328 static inline void memset_page(struct page *page, size_t offset, int val,
331 char *addr = kmap_local_page(page);
333 VM_BUG_ON(offset + len > PAGE_SIZE);
334 memset(addr + offset, val, len);
338 static inline void memcpy_from_page(char *to, struct page *page,
339 size_t offset, size_t len)
341 char *from = kmap_local_page(page);
343 VM_BUG_ON(offset + len > PAGE_SIZE);
344 memcpy(to, from + offset, len);
348 static inline void memcpy_to_page(struct page *page, size_t offset,
349 const char *from, size_t len)
351 char *to = kmap_local_page(page);
353 VM_BUG_ON(offset + len > PAGE_SIZE);
354 memcpy(to + offset, from, len);
355 flush_dcache_page(page);
359 static inline void memzero_page(struct page *page, size_t offset, size_t len)
361 char *addr = kmap_local_page(page);
362 memset(addr + offset, 0, len);
363 flush_dcache_page(page);
367 #endif /* _LINUX_HIGHMEM_H */