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/kmsan.h> 10 #include <linux/mm.h> 11 #include <linux/uaccess.h> 12 #include <linux/hardirq.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 * @page: Pointer to the page which was mapped by kmap() 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, including interrupts. 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 kmap_local_page() is significantly faster than kmap() for the highmem 90 * case it comes with restrictions about the pointer validity. 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 highmem case it 123 * comes with restrictions about the pointer validity. 124 * 125 * On HIGHMEM enabled systems mapping a highmem page has the side effect of 126 * disabling migration in order to keep the virtual address stable across 127 * preemption. No caller of kmap_local_folio() can rely on this side effect. 128 * 129 * Context: Can be invoked from any context. 130 * Return: The virtual address of @offset. 131 */ 132 static inline void *kmap_local_folio(struct folio *folio, size_t offset); 133 134 /** 135 * kmap_atomic - Atomically map a page for temporary usage - Deprecated! 136 * @page: Pointer to the page to be mapped 137 * 138 * Returns: The virtual address of the mapping 139 * 140 * In fact a wrapper around kmap_local_page() which also disables pagefaults 141 * and, depending on PREEMPT_RT configuration, also CPU migration and 142 * preemption. Therefore users should not count on the latter two side effects. 143 * 144 * Mappings should always be released by kunmap_atomic(). 145 * 146 * Do not use in new code. Use kmap_local_page() instead. 147 * 148 * It is used in atomic context when code wants to access the contents of a 149 * page that might be allocated from high memory (see __GFP_HIGHMEM), for 150 * example a page in the pagecache. The API has two functions, and they 151 * can be used in a manner similar to the following:: 152 * 153 * // Find the page of interest. 154 * struct page *page = find_get_page(mapping, offset); 155 * 156 * // Gain access to the contents of that page. 157 * void *vaddr = kmap_atomic(page); 158 * 159 * // Do something to the contents of that page. 160 * memset(vaddr, 0, PAGE_SIZE); 161 * 162 * // Unmap that page. 163 * kunmap_atomic(vaddr); 164 * 165 * Note that the kunmap_atomic() call takes the result of the kmap_atomic() 166 * call, not the argument. 167 * 168 * If you need to map two pages because you want to copy from one page to 169 * another you need to keep the kmap_atomic calls strictly nested, like: 170 * 171 * vaddr1 = kmap_atomic(page1); 172 * vaddr2 = kmap_atomic(page2); 173 * 174 * memcpy(vaddr1, vaddr2, PAGE_SIZE); 175 * 176 * kunmap_atomic(vaddr2); 177 * kunmap_atomic(vaddr1); 178 */ 179 static inline void *kmap_atomic(struct page *page); 180 181 /* Highmem related interfaces for management code */ 182 static inline unsigned int nr_free_highpages(void); 183 static inline unsigned long totalhigh_pages(void); 184 185 #ifndef ARCH_HAS_FLUSH_ANON_PAGE 186 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr) 187 { 188 } 189 #endif 190 191 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE 192 static inline void flush_kernel_vmap_range(void *vaddr, int size) 193 { 194 } 195 static inline void invalidate_kernel_vmap_range(void *vaddr, int size) 196 { 197 } 198 #endif 199 200 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */ 201 #ifndef clear_user_highpage 202 static inline void clear_user_highpage(struct page *page, unsigned long vaddr) 203 { 204 void *addr = kmap_local_page(page); 205 clear_user_page(addr, vaddr, page); 206 kunmap_local(addr); 207 } 208 #endif 209 210 #ifndef vma_alloc_zeroed_movable_folio 211 /** 212 * vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA. 213 * @vma: The VMA the page is to be allocated for. 214 * @vaddr: The virtual address the page will be inserted into. 215 * 216 * This function will allocate a page suitable for inserting into this 217 * VMA at this virtual address. It may be allocated from highmem or 218 * the movable zone. An architecture may provide its own implementation. 219 * 220 * Return: A folio containing one allocated and zeroed page or NULL if 221 * we are out of memory. 222 */ 223 static inline 224 struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, 225 unsigned long vaddr) 226 { 227 struct folio *folio; 228 229 folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, false); 230 if (folio) 231 clear_user_highpage(&folio->page, vaddr); 232 233 return folio; 234 } 235 #endif 236 237 static inline void clear_highpage(struct page *page) 238 { 239 void *kaddr = kmap_local_page(page); 240 clear_page(kaddr); 241 kunmap_local(kaddr); 242 } 243 244 static inline void clear_highpage_kasan_tagged(struct page *page) 245 { 246 u8 tag; 247 248 tag = page_kasan_tag(page); 249 page_kasan_tag_reset(page); 250 clear_highpage(page); 251 page_kasan_tag_set(page, tag); 252 } 253 254 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE 255 256 static inline void tag_clear_highpage(struct page *page) 257 { 258 } 259 260 #endif 261 262 /* 263 * If we pass in a base or tail page, we can zero up to PAGE_SIZE. 264 * If we pass in a head page, we can zero up to the size of the compound page. 265 */ 266 #ifdef CONFIG_HIGHMEM 267 void zero_user_segments(struct page *page, unsigned start1, unsigned end1, 268 unsigned start2, unsigned end2); 269 #else 270 static inline void zero_user_segments(struct page *page, 271 unsigned start1, unsigned end1, 272 unsigned start2, unsigned end2) 273 { 274 void *kaddr = kmap_local_page(page); 275 unsigned int i; 276 277 BUG_ON(end1 > page_size(page) || end2 > page_size(page)); 278 279 if (end1 > start1) 280 memset(kaddr + start1, 0, end1 - start1); 281 282 if (end2 > start2) 283 memset(kaddr + start2, 0, end2 - start2); 284 285 kunmap_local(kaddr); 286 for (i = 0; i < compound_nr(page); i++) 287 flush_dcache_page(page + i); 288 } 289 #endif 290 291 static inline void zero_user_segment(struct page *page, 292 unsigned start, unsigned end) 293 { 294 zero_user_segments(page, start, end, 0, 0); 295 } 296 297 static inline void zero_user(struct page *page, 298 unsigned start, unsigned size) 299 { 300 zero_user_segments(page, start, start + size, 0, 0); 301 } 302 303 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE 304 305 static inline void copy_user_highpage(struct page *to, struct page *from, 306 unsigned long vaddr, struct vm_area_struct *vma) 307 { 308 char *vfrom, *vto; 309 310 vfrom = kmap_local_page(from); 311 vto = kmap_local_page(to); 312 copy_user_page(vto, vfrom, vaddr, to); 313 kmsan_unpoison_memory(page_address(to), PAGE_SIZE); 314 kunmap_local(vto); 315 kunmap_local(vfrom); 316 } 317 318 #endif 319 320 #ifdef copy_mc_to_kernel 321 static inline int copy_mc_user_highpage(struct page *to, struct page *from, 322 unsigned long vaddr, struct vm_area_struct *vma) 323 { 324 unsigned long ret; 325 char *vfrom, *vto; 326 327 vfrom = kmap_local_page(from); 328 vto = kmap_local_page(to); 329 ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE); 330 if (!ret) 331 kmsan_unpoison_memory(page_address(to), PAGE_SIZE); 332 kunmap_local(vto); 333 kunmap_local(vfrom); 334 335 return ret; 336 } 337 #else 338 static inline int copy_mc_user_highpage(struct page *to, struct page *from, 339 unsigned long vaddr, struct vm_area_struct *vma) 340 { 341 copy_user_highpage(to, from, vaddr, vma); 342 return 0; 343 } 344 #endif 345 346 #ifndef __HAVE_ARCH_COPY_HIGHPAGE 347 348 static inline void copy_highpage(struct page *to, struct page *from) 349 { 350 char *vfrom, *vto; 351 352 vfrom = kmap_local_page(from); 353 vto = kmap_local_page(to); 354 copy_page(vto, vfrom); 355 kmsan_copy_page_meta(to, from); 356 kunmap_local(vto); 357 kunmap_local(vfrom); 358 } 359 360 #endif 361 362 static inline void memcpy_page(struct page *dst_page, size_t dst_off, 363 struct page *src_page, size_t src_off, 364 size_t len) 365 { 366 char *dst = kmap_local_page(dst_page); 367 char *src = kmap_local_page(src_page); 368 369 VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE); 370 memcpy(dst + dst_off, src + src_off, len); 371 kunmap_local(src); 372 kunmap_local(dst); 373 } 374 375 static inline void memset_page(struct page *page, size_t offset, int val, 376 size_t len) 377 { 378 char *addr = kmap_local_page(page); 379 380 VM_BUG_ON(offset + len > PAGE_SIZE); 381 memset(addr + offset, val, len); 382 kunmap_local(addr); 383 } 384 385 static inline void memcpy_from_page(char *to, struct page *page, 386 size_t offset, size_t len) 387 { 388 char *from = kmap_local_page(page); 389 390 VM_BUG_ON(offset + len > PAGE_SIZE); 391 memcpy(to, from + offset, len); 392 kunmap_local(from); 393 } 394 395 static inline void memcpy_to_page(struct page *page, size_t offset, 396 const char *from, size_t len) 397 { 398 char *to = kmap_local_page(page); 399 400 VM_BUG_ON(offset + len > PAGE_SIZE); 401 memcpy(to + offset, from, len); 402 flush_dcache_page(page); 403 kunmap_local(to); 404 } 405 406 static inline void memzero_page(struct page *page, size_t offset, size_t len) 407 { 408 char *addr = kmap_local_page(page); 409 410 VM_BUG_ON(offset + len > PAGE_SIZE); 411 memset(addr + offset, 0, len); 412 flush_dcache_page(page); 413 kunmap_local(addr); 414 } 415 416 /** 417 * memcpy_from_file_folio - Copy some bytes from a file folio. 418 * @to: The destination buffer. 419 * @folio: The folio to copy from. 420 * @pos: The position in the file. 421 * @len: The maximum number of bytes to copy. 422 * 423 * Copy up to @len bytes from this folio. This may be limited by PAGE_SIZE 424 * if the folio comes from HIGHMEM, and by the size of the folio. 425 * 426 * Return: The number of bytes copied from the folio. 427 */ 428 static inline size_t memcpy_from_file_folio(char *to, struct folio *folio, 429 loff_t pos, size_t len) 430 { 431 size_t offset = offset_in_folio(folio, pos); 432 char *from = kmap_local_folio(folio, offset); 433 434 if (folio_test_highmem(folio)) { 435 offset = offset_in_page(offset); 436 len = min_t(size_t, len, PAGE_SIZE - offset); 437 } else 438 len = min(len, folio_size(folio) - offset); 439 440 memcpy(to, from, len); 441 kunmap_local(from); 442 443 return len; 444 } 445 446 /** 447 * folio_zero_segments() - Zero two byte ranges in a folio. 448 * @folio: The folio to write to. 449 * @start1: The first byte to zero. 450 * @xend1: One more than the last byte in the first range. 451 * @start2: The first byte to zero in the second range. 452 * @xend2: One more than the last byte in the second range. 453 */ 454 static inline void folio_zero_segments(struct folio *folio, 455 size_t start1, size_t xend1, size_t start2, size_t xend2) 456 { 457 zero_user_segments(&folio->page, start1, xend1, start2, xend2); 458 } 459 460 /** 461 * folio_zero_segment() - Zero a byte range in a folio. 462 * @folio: The folio to write to. 463 * @start: The first byte to zero. 464 * @xend: One more than the last byte to zero. 465 */ 466 static inline void folio_zero_segment(struct folio *folio, 467 size_t start, size_t xend) 468 { 469 zero_user_segments(&folio->page, start, xend, 0, 0); 470 } 471 472 /** 473 * folio_zero_range() - Zero a byte range in a folio. 474 * @folio: The folio to write to. 475 * @start: The first byte to zero. 476 * @length: The number of bytes to zero. 477 */ 478 static inline void folio_zero_range(struct folio *folio, 479 size_t start, size_t length) 480 { 481 zero_user_segments(&folio->page, start, start + length, 0, 0); 482 } 483 484 static inline void put_and_unmap_page(struct page *page, void *addr) 485 { 486 kunmap_local(addr); 487 put_page(page); 488 } 489 490 #endif /* _LINUX_HIGHMEM_H */ 491