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>
9 #include <linux/kmsan.h>
11 #include <linux/uaccess.h>
12 #include <linux/hardirq.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 * @page: Pointer to the page which was mapped by kmap()
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, including interrupts.
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.
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 * In fact a wrapper around kmap_local_page() which also disables pagefaults
142 * and, depending on PREEMPT_RT configuration, also CPU migration and
143 * preemption. Therefore users should not count on the latter two side effects.
145 * Mappings should always be released by kunmap_atomic().
147 * Do not use in new code. Use kmap_local_page() instead.
149 * It is used in atomic context when code wants to access the contents of a
150 * page that might be allocated from high memory (see __GFP_HIGHMEM), for
151 * example a page in the pagecache. The API has two functions, and they
152 * can be used in a manner similar to the following::
154 * // Find the page of interest.
155 * struct page *page = find_get_page(mapping, offset);
157 * // Gain access to the contents of that page.
158 * void *vaddr = kmap_atomic(page);
160 * // Do something to the contents of that page.
161 * memset(vaddr, 0, PAGE_SIZE);
163 * // Unmap that page.
164 * kunmap_atomic(vaddr);
166 * Note that the kunmap_atomic() call takes the result of the kmap_atomic()
167 * call, not the argument.
169 * If you need to map two pages because you want to copy from one page to
170 * another you need to keep the kmap_atomic calls strictly nested, like:
172 * vaddr1 = kmap_atomic(page1);
173 * vaddr2 = kmap_atomic(page2);
175 * memcpy(vaddr1, vaddr2, PAGE_SIZE);
177 * kunmap_atomic(vaddr2);
178 * kunmap_atomic(vaddr1);
180 static inline void *kmap_atomic(struct page *page);
182 /* Highmem related interfaces for management code */
183 static inline unsigned int nr_free_highpages(void);
184 static inline unsigned long totalhigh_pages(void);
186 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
187 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
192 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
193 static inline void flush_kernel_vmap_range(void *vaddr, int size)
196 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
201 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
202 #ifndef clear_user_highpage
203 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
205 void *addr = kmap_local_page(page);
206 clear_user_page(addr, vaddr, page);
211 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
213 * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
214 * @vma: The VMA the page is to be allocated for
215 * @vaddr: The virtual address the page will be inserted into
217 * Returns: The allocated and zeroed HIGHMEM page
219 * This function will allocate a page for a VMA that the caller knows will
220 * be able to migrate in the future using move_pages() or reclaimed
222 * An architecture may override this function by defining
223 * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
226 static inline struct page *
227 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
230 struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
233 clear_user_highpage(page, vaddr);
239 static inline void clear_highpage(struct page *page)
241 void *kaddr = kmap_local_page(page);
246 static inline void clear_highpage_kasan_tagged(struct page *page)
250 tag = page_kasan_tag(page);
251 page_kasan_tag_reset(page);
252 clear_highpage(page);
253 page_kasan_tag_set(page, tag);
256 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
258 static inline void tag_clear_highpage(struct page *page)
265 * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
266 * If we pass in a head page, we can zero up to the size of the compound page.
268 #ifdef CONFIG_HIGHMEM
269 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
270 unsigned start2, unsigned end2);
272 static inline void zero_user_segments(struct page *page,
273 unsigned start1, unsigned end1,
274 unsigned start2, unsigned end2)
276 void *kaddr = kmap_local_page(page);
279 BUG_ON(end1 > page_size(page) || end2 > page_size(page));
282 memset(kaddr + start1, 0, end1 - start1);
285 memset(kaddr + start2, 0, end2 - start2);
288 for (i = 0; i < compound_nr(page); i++)
289 flush_dcache_page(page + i);
293 static inline void zero_user_segment(struct page *page,
294 unsigned start, unsigned end)
296 zero_user_segments(page, start, end, 0, 0);
299 static inline void zero_user(struct page *page,
300 unsigned start, unsigned size)
302 zero_user_segments(page, start, start + size, 0, 0);
305 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
307 static inline void copy_user_highpage(struct page *to, struct page *from,
308 unsigned long vaddr, struct vm_area_struct *vma)
312 vfrom = kmap_local_page(from);
313 vto = kmap_local_page(to);
314 copy_user_page(vto, vfrom, vaddr, to);
315 kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
322 #ifdef copy_mc_to_kernel
323 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
324 unsigned long vaddr, struct vm_area_struct *vma)
329 vfrom = kmap_local_page(from);
330 vto = kmap_local_page(to);
331 ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
333 kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
340 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
341 unsigned long vaddr, struct vm_area_struct *vma)
343 copy_user_highpage(to, from, vaddr, vma);
348 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
350 static inline void copy_highpage(struct page *to, struct page *from)
354 vfrom = kmap_local_page(from);
355 vto = kmap_local_page(to);
356 copy_page(vto, vfrom);
357 kmsan_copy_page_meta(to, from);
364 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
365 struct page *src_page, size_t src_off,
368 char *dst = kmap_local_page(dst_page);
369 char *src = kmap_local_page(src_page);
371 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
372 memcpy(dst + dst_off, src + src_off, len);
377 static inline void memset_page(struct page *page, size_t offset, int val,
380 char *addr = kmap_local_page(page);
382 VM_BUG_ON(offset + len > PAGE_SIZE);
383 memset(addr + offset, val, len);
387 static inline void memcpy_from_page(char *to, struct page *page,
388 size_t offset, size_t len)
390 char *from = kmap_local_page(page);
392 VM_BUG_ON(offset + len > PAGE_SIZE);
393 memcpy(to, from + offset, len);
397 static inline void memcpy_to_page(struct page *page, size_t offset,
398 const char *from, size_t len)
400 char *to = kmap_local_page(page);
402 VM_BUG_ON(offset + len > PAGE_SIZE);
403 memcpy(to + offset, from, len);
404 flush_dcache_page(page);
408 static inline void memzero_page(struct page *page, size_t offset, size_t len)
410 char *addr = kmap_local_page(page);
412 VM_BUG_ON(offset + len > PAGE_SIZE);
413 memset(addr + offset, 0, len);
414 flush_dcache_page(page);
419 * folio_zero_segments() - Zero two byte ranges in a folio.
420 * @folio: The folio to write to.
421 * @start1: The first byte to zero.
422 * @xend1: One more than the last byte in the first range.
423 * @start2: The first byte to zero in the second range.
424 * @xend2: One more than the last byte in the second range.
426 static inline void folio_zero_segments(struct folio *folio,
427 size_t start1, size_t xend1, size_t start2, size_t xend2)
429 zero_user_segments(&folio->page, start1, xend1, start2, xend2);
433 * folio_zero_segment() - Zero a byte range in a folio.
434 * @folio: The folio to write to.
435 * @start: The first byte to zero.
436 * @xend: One more than the last byte to zero.
438 static inline void folio_zero_segment(struct folio *folio,
439 size_t start, size_t xend)
441 zero_user_segments(&folio->page, start, xend, 0, 0);
445 * folio_zero_range() - Zero a byte range in a folio.
446 * @folio: The folio to write to.
447 * @start: The first byte to zero.
448 * @length: The number of bytes to zero.
450 static inline void folio_zero_range(struct folio *folio,
451 size_t start, size_t length)
453 zero_user_segments(&folio->page, start, start + length, 0, 0);
456 #endif /* _LINUX_HIGHMEM_H */