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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/mm.h>
9#include <linux/uaccess.h>
10#include <linux/hardirq.h>
11
12#include <asm/cacheflush.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 */
37static inline void *kmap(struct page *page);
38
39/**
40 * kunmap - Unmap the virtual address mapped by kmap()
41 * @addr: Virtual address to be unmapped
42 *
43 * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
44 * pages in the low memory area.
45 */
46static 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 */
54static 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 */
60static 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.
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 it is significantly faster than kmap() for the higmem case it
90 * comes with restrictions about the pointer validity. Only use when really
91 * necessary.
92 *
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.
96 */
97static inline void *kmap_local_page(struct page *page);
98
99/**
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.
103 *
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::
107 *
108 * addr1 = kmap_local_folio(folio1, offset1);
109 * addr2 = kmap_local_folio(folio2, offset2);
110 * ...
111 * kunmap_local(addr2);
112 * kunmap_local(addr1);
113 *
114 * Unmapping addr1 before addr2 is invalid and causes malfunction.
115 *
116 * Contrary to kmap() mappings the mapping is only valid in the context of
117 * the caller and cannot be handed to other contexts.
118 *
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.
122 *
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
125 * necessary.
126 *
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.
130 *
131 * Context: Can be invoked from any context.
132 * Return: The virtual address of @offset.
133 */
134static inline void *kmap_local_folio(struct folio *folio, size_t offset);
135
136/**
137 * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
138 * @page: Pointer to the page to be mapped
139 *
140 * Returns: The virtual address of the mapping
141 *
142 * Effectively a wrapper around kmap_local_page() which disables pagefaults
143 * and preemption.
144 *
145 * Do not use in new code. Use kmap_local_page() instead.
146 */
147static inline void *kmap_atomic(struct page *page);
148
149/**
150 * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic()
151 * @addr: Virtual address to be unmapped
152 *
153 * Counterpart to kmap_atomic().
154 *
155 * Effectively a wrapper around kunmap_local() which additionally undoes
156 * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
157 * preemption.
158 */
159
160/* Highmem related interfaces for management code */
161static inline unsigned int nr_free_highpages(void);
162static inline unsigned long totalhigh_pages(void);
163
164#ifndef ARCH_HAS_FLUSH_ANON_PAGE
165static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
166{
167}
168#endif
169
170#ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
171static inline void flush_kernel_vmap_range(void *vaddr, int size)
172{
173}
174static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
175{
176}
177#endif
178
179/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
180#ifndef clear_user_highpage
181static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
182{
183 void *addr = kmap_local_page(page);
184 clear_user_page(addr, vaddr, page);
185 kunmap_local(addr);
186}
187#endif
188
189#ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
190/**
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
194 *
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
197 *
198 * An architecture may override this function by defining
199 * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
200 * implementation.
201 */
202static inline struct page *
203alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
204 unsigned long vaddr)
205{
206 struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
207
208 if (page)
209 clear_user_highpage(page, vaddr);
210
211 return page;
212}
213#endif
214
215static inline void clear_highpage(struct page *page)
216{
217 void *kaddr = kmap_local_page(page);
218 clear_page(kaddr);
219 kunmap_local(kaddr);
220}
221
222#ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
223
224static inline void tag_clear_highpage(struct page *page)
225{
226}
227
228#endif
229
230/*
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.
233 */
234#if defined(CONFIG_HIGHMEM) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
235void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
236 unsigned start2, unsigned end2);
237#else /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
238static inline void zero_user_segments(struct page *page,
239 unsigned start1, unsigned end1,
240 unsigned start2, unsigned end2)
241{
242 void *kaddr = kmap_local_page(page);
243 unsigned int i;
244
245 BUG_ON(end1 > page_size(page) || end2 > page_size(page));
246
247 if (end1 > start1)
248 memset(kaddr + start1, 0, end1 - start1);
249
250 if (end2 > start2)
251 memset(kaddr + start2, 0, end2 - start2);
252
253 kunmap_local(kaddr);
254 for (i = 0; i < compound_nr(page); i++)
255 flush_dcache_page(page + i);
256}
257#endif /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
258
259static inline void zero_user_segment(struct page *page,
260 unsigned start, unsigned end)
261{
262 zero_user_segments(page, start, end, 0, 0);
263}
264
265static inline void zero_user(struct page *page,
266 unsigned start, unsigned size)
267{
268 zero_user_segments(page, start, start + size, 0, 0);
269}
270
271#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
272
273static inline void copy_user_highpage(struct page *to, struct page *from,
274 unsigned long vaddr, struct vm_area_struct *vma)
275{
276 char *vfrom, *vto;
277
278 vfrom = kmap_local_page(from);
279 vto = kmap_local_page(to);
280 copy_user_page(vto, vfrom, vaddr, to);
281 kunmap_local(vto);
282 kunmap_local(vfrom);
283}
284
285#endif
286
287#ifndef __HAVE_ARCH_COPY_HIGHPAGE
288
289static inline void copy_highpage(struct page *to, struct page *from)
290{
291 char *vfrom, *vto;
292
293 vfrom = kmap_local_page(from);
294 vto = kmap_local_page(to);
295 copy_page(vto, vfrom);
296 kunmap_local(vto);
297 kunmap_local(vfrom);
298}
299
300#endif
301
302static inline void memcpy_page(struct page *dst_page, size_t dst_off,
303 struct page *src_page, size_t src_off,
304 size_t len)
305{
306 char *dst = kmap_local_page(dst_page);
307 char *src = kmap_local_page(src_page);
308
309 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
310 memcpy(dst + dst_off, src + src_off, len);
311 kunmap_local(src);
312 kunmap_local(dst);
313}
314
315static inline void memmove_page(struct page *dst_page, size_t dst_off,
316 struct page *src_page, size_t src_off,
317 size_t len)
318{
319 char *dst = kmap_local_page(dst_page);
320 char *src = kmap_local_page(src_page);
321
322 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
323 memmove(dst + dst_off, src + src_off, len);
324 kunmap_local(src);
325 kunmap_local(dst);
326}
327
328static inline void memset_page(struct page *page, size_t offset, int val,
329 size_t len)
330{
331 char *addr = kmap_local_page(page);
332
333 VM_BUG_ON(offset + len > PAGE_SIZE);
334 memset(addr + offset, val, len);
335 kunmap_local(addr);
336}
337
338static inline void memcpy_from_page(char *to, struct page *page,
339 size_t offset, size_t len)
340{
341 char *from = kmap_local_page(page);
342
343 VM_BUG_ON(offset + len > PAGE_SIZE);
344 memcpy(to, from + offset, len);
345 kunmap_local(from);
346}
347
348static inline void memcpy_to_page(struct page *page, size_t offset,
349 const char *from, size_t len)
350{
351 char *to = kmap_local_page(page);
352
353 VM_BUG_ON(offset + len > PAGE_SIZE);
354 memcpy(to + offset, from, len);
355 flush_dcache_page(page);
356 kunmap_local(to);
357}
358
359static inline void memzero_page(struct page *page, size_t offset, size_t len)
360{
361 char *addr = kmap_local_page(page);
362 memset(addr + offset, 0, len);
363 flush_dcache_page(page);
364 kunmap_local(addr);
365}
366
367#endif /* _LINUX_HIGHMEM_H */