include/linux/highmem.h

   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  */
  37 static 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  */
  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.
  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  */
  97 static inline void *kmap_local_page(struct page *page);
  98
  99 /**
 100  * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
 101  * @page:       Pointer to the page to be mapped
 102  *
 103  * Returns: The virtual address of the mapping
 104  *
 105  * Effectively a wrapper around kmap_local_page() which disables pagefaults
 106  * and preemption.
 107  *
 108  * Do not use in new code. Use kmap_local_page() instead.
 109  */
 110 static inline void *kmap_atomic(struct page *page);
 111
 112 /**
 113  * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic()
 114  * @addr:       Virtual address to be unmapped
 115  *
 116  * Counterpart to kmap_atomic().
 117  *
 118  * Effectively a wrapper around kunmap_local() which additionally undoes
 119  * the side effects of kmap_atomic(), i.e. reenabling pagefaults and
 120  * preemption.
 121  */
 122
 123 /* Highmem related interfaces for management code */
 124 static inline unsigned int nr_free_highpages(void);
 125 static inline unsigned long totalhigh_pages(void);
 126
 127 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
 128 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
 129 {
 130 }
 131 #endif
 132
 133 #ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
 134 static inline void flush_kernel_dcache_page(struct page *page)
 135 {
 136 }
 137 static inline void flush_kernel_vmap_range(void *vaddr, int size)
 138 {
 139 }
 140 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
 141 {
 142 }
 143 #endif
 144
 145 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
 146 #ifndef clear_user_highpage
 147 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
 148 {
 149         void *addr = kmap_atomic(page);
 150         clear_user_page(addr, vaddr, page);
 151         kunmap_atomic(addr);
 152 }
 153 #endif
 154
 155 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE
 156 /**
 157  * __alloc_zeroed_user_highpage - Allocate a zeroed HIGHMEM page for a VMA with caller-specified movable GFP flags
 158  * @movableflags: The GFP flags related to the pages future ability to move like __GFP_MOVABLE
 159  * @vma: The VMA the page is to be allocated for
 160  * @vaddr: The virtual address the page will be inserted into
 161  *
 162  * This function will allocate a page for a VMA but the caller is expected
 163  * to specify via movableflags whether the page will be movable in the
 164  * future or not
 165  *
 166  * An architecture may override this function by defining
 167  * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE and providing their own
 168  * implementation.
 169  */
 170 static inline struct page *
 171 __alloc_zeroed_user_highpage(gfp_t movableflags,
 172                         struct vm_area_struct *vma,
 173                         unsigned long vaddr)
 174 {
 175         struct page *page = alloc_page_vma(GFP_HIGHUSER | movableflags,
 176                         vma, vaddr);
 177
 178         if (page)
 179                 clear_user_highpage(page, vaddr);
 180
 181         return page;
 182 }
 183 #endif
 184
 185 /**
 186  * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
 187  * @vma: The VMA the page is to be allocated for
 188  * @vaddr: The virtual address the page will be inserted into
 189  *
 190  * This function will allocate a page for a VMA that the caller knows will
 191  * be able to migrate in the future using move_pages() or reclaimed
 192  */
 193 static inline struct page *
 194 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
 195                                         unsigned long vaddr)
 196 {
 197         return __alloc_zeroed_user_highpage(__GFP_MOVABLE, vma, vaddr);
 198 }
 199
 200 static inline void clear_highpage(struct page *page)
 201 {
 202         void *kaddr = kmap_atomic(page);
 203         clear_page(kaddr);
 204         kunmap_atomic(kaddr);
 205 }
 206
 207 /*
 208  * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
 209  * If we pass in a head page, we can zero up to the size of the compound page.
 210  */
 211 #if defined(CONFIG_HIGHMEM) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 212 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 213                 unsigned start2, unsigned end2);
 214 #else /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
 215 static inline void zero_user_segments(struct page *page,
 216                 unsigned start1, unsigned end1,
 217                 unsigned start2, unsigned end2)
 218 {
 219         void *kaddr = kmap_atomic(page);
 220         unsigned int i;
 221
 222         BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 223
 224         if (end1 > start1)
 225                 memset(kaddr + start1, 0, end1 - start1);
 226
 227         if (end2 > start2)
 228                 memset(kaddr + start2, 0, end2 - start2);
 229
 230         kunmap_atomic(kaddr);
 231         for (i = 0; i < compound_nr(page); i++)
 232                 flush_dcache_page(page + i);
 233 }
 234 #endif /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */
 235
 236 static inline void zero_user_segment(struct page *page,
 237         unsigned start, unsigned end)
 238 {
 239         zero_user_segments(page, start, end, 0, 0);
 240 }
 241
 242 static inline void zero_user(struct page *page,
 243         unsigned start, unsigned size)
 244 {
 245         zero_user_segments(page, start, start + size, 0, 0);
 246 }
 247
 248 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
 249
 250 static inline void copy_user_highpage(struct page *to, struct page *from,
 251         unsigned long vaddr, struct vm_area_struct *vma)
 252 {
 253         char *vfrom, *vto;
 254
 255         vfrom = kmap_atomic(from);
 256         vto = kmap_atomic(to);
 257         copy_user_page(vto, vfrom, vaddr, to);
 258         kunmap_atomic(vto);
 259         kunmap_atomic(vfrom);
 260 }
 261
 262 #endif
 263
 264 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
 265
 266 static inline void copy_highpage(struct page *to, struct page *from)
 267 {
 268         char *vfrom, *vto;
 269
 270         vfrom = kmap_atomic(from);
 271         vto = kmap_atomic(to);
 272         copy_page(vto, vfrom);
 273         kunmap_atomic(vto);
 274         kunmap_atomic(vfrom);
 275 }
 276
 277 #endif
 278
 279 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
 280                                struct page *src_page, size_t src_off,
 281                                size_t len)
 282 {
 283         char *dst = kmap_local_page(dst_page);
 284         char *src = kmap_local_page(src_page);
 285
 286         VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
 287         memcpy(dst + dst_off, src + src_off, len);
 288         kunmap_local(src);
 289         kunmap_local(dst);
 290 }
 291
 292 static inline void memmove_page(struct page *dst_page, size_t dst_off,
 293                                struct page *src_page, size_t src_off,
 294                                size_t len)
 295 {
 296         char *dst = kmap_local_page(dst_page);
 297         char *src = kmap_local_page(src_page);
 298
 299         VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
 300         memmove(dst + dst_off, src + src_off, len);
 301         kunmap_local(src);
 302         kunmap_local(dst);
 303 }
 304
 305 static inline void memset_page(struct page *page, size_t offset, int val,
 306                                size_t len)
 307 {
 308         char *addr = kmap_local_page(page);
 309
 310         VM_BUG_ON(offset + len > PAGE_SIZE);
 311         memset(addr + offset, val, len);
 312         kunmap_local(addr);
 313 }
 314
 315 static inline void memcpy_from_page(char *to, struct page *page,
 316                                     size_t offset, size_t len)
 317 {
 318         char *from = kmap_local_page(page);
 319
 320         VM_BUG_ON(offset + len > PAGE_SIZE);
 321         memcpy(to, from + offset, len);
 322         kunmap_local(from);
 323 }
 324
 325 static inline void memcpy_to_page(struct page *page, size_t offset,
 326                                   const char *from, size_t len)
 327 {
 328         char *to = kmap_local_page(page);
 329
 330         VM_BUG_ON(offset + len > PAGE_SIZE);
 331         memcpy(to + offset, from, len);
 332         kunmap_local(to);
 333 }
 334
 335 static inline void memzero_page(struct page *page, size_t offset, size_t len)
 336 {
 337         char *addr = kmap_atomic(page);
 338         memset(addr + offset, 0, len);
 339         kunmap_atomic(addr);
 340 }
 341
 342 #endif /* _LINUX_HIGHMEM_H */