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/cacheflush.h> 9 #include <linux/mm.h> 10 #include <linux/uaccess.h> 11 #include <linux/hardirq.h> 12 13 #include "highmem-internal.h" 14 15 /** 16 * kmap - Map a page for long term usage 17 * @page: Pointer to the page to be mapped 18 * 19 * Returns: The virtual address of the mapping 20 * 21 * Can only be invoked from preemptible task context because on 32bit 22 * systems with CONFIG_HIGHMEM enabled this function might sleep. 23 * 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. 26 * 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 29 * other contexts. 30 * 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 34 * kunmap(). 35 */ 36 static inline void *kmap(struct page *page); 37 38 /** 39 * kunmap - Unmap the virtual address mapped by kmap() 40 * @addr: Virtual address to be unmapped 41 * 42 * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of 43 * pages in the low memory area. 44 */ 45 static inline void kunmap(struct page *page); 46 47 /** 48 * kmap_to_page - Get the page for a kmap'ed address 49 * @addr: The address to look up 50 * 51 * Returns: The page which is mapped to @addr. 52 */ 53 static inline struct page *kmap_to_page(void *addr); 54 55 /** 56 * kmap_flush_unused - Flush all unused kmap mappings in order to 57 * remove stray mappings 58 */ 59 static inline void kmap_flush_unused(void); 60 61 /** 62 * kmap_local_page - Map a page for temporary usage 63 * @page: Pointer to the page to be mapped 64 * 65 * Returns: The virtual address of the mapping 66 * 67 * Can be invoked from any context. 68 * 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 71 * the map operation: 72 * 73 * addr1 = kmap_local_page(page1); 74 * addr2 = kmap_local_page(page2); 75 * ... 76 * kunmap_local(addr2); 77 * kunmap_local(addr1); 78 * 79 * Unmapping addr1 before addr2 is invalid and causes malfunction. 80 * 81 * Contrary to kmap() mappings the mapping is only valid in the context of 82 * the caller and cannot be handed to other contexts. 83 * 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 86 * temporarily mapped. 87 * 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 90 * necessary. 91 * 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. 95 */ 96 static inline void *kmap_local_page(struct page *page); 97 98 /** 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. 102 * 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:: 106 * 107 * addr1 = kmap_local_folio(folio1, offset1); 108 * addr2 = kmap_local_folio(folio2, offset2); 109 * ... 110 * kunmap_local(addr2); 111 * kunmap_local(addr1); 112 * 113 * Unmapping addr1 before addr2 is invalid and causes malfunction. 114 * 115 * Contrary to kmap() mappings the mapping is only valid in the context of 116 * the caller and cannot be handed to other contexts. 117 * 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. 121 * 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 124 * necessary. 125 * 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. 129 * 130 * Context: Can be invoked from any context. 131 * Return: The virtual address of @offset. 132 */ 133 static inline void *kmap_local_folio(struct folio *folio, size_t offset); 134 135 /** 136 * kmap_atomic - Atomically map a page for temporary usage - Deprecated! 137 * @page: Pointer to the page to be mapped 138 * 139 * Returns: The virtual address of the mapping 140 * 141 * Effectively a wrapper around kmap_local_page() which disables pagefaults 142 * and preemption. 143 * 144 * Do not use in new code. Use kmap_local_page() instead. 145 */ 146 static inline void *kmap_atomic(struct page *page); 147 148 /** 149 * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic() 150 * @addr: Virtual address to be unmapped 151 * 152 * Counterpart to kmap_atomic(). 153 * 154 * Effectively a wrapper around kunmap_local() which additionally undoes 155 * the side effects of kmap_atomic(), i.e. reenabling pagefaults and 156 * preemption. 157 */ 158 159 /* Highmem related interfaces for management code */ 160 static inline unsigned int nr_free_highpages(void); 161 static inline unsigned long totalhigh_pages(void); 162 163 #ifndef ARCH_HAS_FLUSH_ANON_PAGE 164 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr) 165 { 166 } 167 #endif 168 169 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE 170 static inline void flush_kernel_vmap_range(void *vaddr, int size) 171 { 172 } 173 static inline void invalidate_kernel_vmap_range(void *vaddr, int size) 174 { 175 } 176 #endif 177 178 /* 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) 181 { 182 void *addr = kmap_local_page(page); 183 clear_user_page(addr, vaddr, page); 184 kunmap_local(addr); 185 } 186 #endif 187 188 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE 189 /** 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 193 * 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 196 * 197 * An architecture may override this function by defining 198 * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own 199 * implementation. 200 */ 201 static inline struct page * 202 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma, 203 unsigned long vaddr) 204 { 205 struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); 206 207 if (page) 208 clear_user_highpage(page, vaddr); 209 210 return page; 211 } 212 #endif 213 214 static inline void clear_highpage(struct page *page) 215 { 216 void *kaddr = kmap_local_page(page); 217 clear_page(kaddr); 218 kunmap_local(kaddr); 219 } 220 221 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE 222 223 static inline void tag_clear_highpage(struct page *page) 224 { 225 } 226 227 #endif 228 229 /* 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. 232 */ 233 #ifdef CONFIG_HIGHMEM 234 void zero_user_segments(struct page *page, unsigned start1, unsigned end1, 235 unsigned start2, unsigned end2); 236 #else 237 static inline void zero_user_segments(struct page *page, 238 unsigned start1, unsigned end1, 239 unsigned start2, unsigned end2) 240 { 241 void *kaddr = kmap_local_page(page); 242 unsigned int i; 243 244 BUG_ON(end1 > page_size(page) || end2 > page_size(page)); 245 246 if (end1 > start1) 247 memset(kaddr + start1, 0, end1 - start1); 248 249 if (end2 > start2) 250 memset(kaddr + start2, 0, end2 - start2); 251 252 kunmap_local(kaddr); 253 for (i = 0; i < compound_nr(page); i++) 254 flush_dcache_page(page + i); 255 } 256 #endif 257 258 static inline void zero_user_segment(struct page *page, 259 unsigned start, unsigned end) 260 { 261 zero_user_segments(page, start, end, 0, 0); 262 } 263 264 static inline void zero_user(struct page *page, 265 unsigned start, unsigned size) 266 { 267 zero_user_segments(page, start, start + size, 0, 0); 268 } 269 270 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE 271 272 static inline void copy_user_highpage(struct page *to, struct page *from, 273 unsigned long vaddr, struct vm_area_struct *vma) 274 { 275 char *vfrom, *vto; 276 277 vfrom = kmap_local_page(from); 278 vto = kmap_local_page(to); 279 copy_user_page(vto, vfrom, vaddr, to); 280 kunmap_local(vto); 281 kunmap_local(vfrom); 282 } 283 284 #endif 285 286 #ifndef __HAVE_ARCH_COPY_HIGHPAGE 287 288 static inline void copy_highpage(struct page *to, struct page *from) 289 { 290 char *vfrom, *vto; 291 292 vfrom = kmap_local_page(from); 293 vto = kmap_local_page(to); 294 copy_page(vto, vfrom); 295 kunmap_local(vto); 296 kunmap_local(vfrom); 297 } 298 299 #endif 300 301 static inline void memcpy_page(struct page *dst_page, size_t dst_off, 302 struct page *src_page, size_t src_off, 303 size_t len) 304 { 305 char *dst = kmap_local_page(dst_page); 306 char *src = kmap_local_page(src_page); 307 308 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); 309 memcpy(dst + dst_off, src + src_off, len); 310 kunmap_local(src); 311 kunmap_local(dst); 312 } 313 314 static inline void memmove_page(struct page *dst_page, size_t dst_off, 315 struct page *src_page, size_t src_off, 316 size_t len) 317 { 318 char *dst = kmap_local_page(dst_page); 319 char *src = kmap_local_page(src_page); 320 321 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); 322 memmove(dst + dst_off, src + src_off, len); 323 kunmap_local(src); 324 kunmap_local(dst); 325 } 326 327 static inline void memset_page(struct page *page, size_t offset, int val, 328 size_t len) 329 { 330 char *addr = kmap_local_page(page); 331 332 VM_BUG_ON(offset + len > PAGE_SIZE); 333 memset(addr + offset, val, len); 334 kunmap_local(addr); 335 } 336 337 static inline void memcpy_from_page(char *to, struct page *page, 338 size_t offset, size_t len) 339 { 340 char *from = kmap_local_page(page); 341 342 VM_BUG_ON(offset + len > PAGE_SIZE); 343 memcpy(to, from + offset, len); 344 kunmap_local(from); 345 } 346 347 static inline void memcpy_to_page(struct page *page, size_t offset, 348 const char *from, size_t len) 349 { 350 char *to = kmap_local_page(page); 351 352 VM_BUG_ON(offset + len > PAGE_SIZE); 353 memcpy(to + offset, from, len); 354 flush_dcache_page(page); 355 kunmap_local(to); 356 } 357 358 static inline void memzero_page(struct page *page, size_t offset, size_t len) 359 { 360 char *addr = kmap_local_page(page); 361 memset(addr + offset, 0, len); 362 flush_dcache_page(page); 363 kunmap_local(addr); 364 } 365 366 /** 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. 373 */ 374 static inline void folio_zero_segments(struct folio *folio, 375 size_t start1, size_t xend1, size_t start2, size_t xend2) 376 { 377 zero_user_segments(&folio->page, start1, xend1, start2, xend2); 378 } 379 380 /** 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. 385 */ 386 static inline void folio_zero_segment(struct folio *folio, 387 size_t start, size_t xend) 388 { 389 zero_user_segments(&folio->page, start, xend, 0, 0); 390 } 391 392 /** 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. 397 */ 398 static inline void folio_zero_range(struct folio *folio, 399 size_t start, size_t length) 400 { 401 zero_user_segments(&folio->page, start, start + length, 0, 0); 402 } 403 404 #endif /* _LINUX_HIGHMEM_H */ 405