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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_HIGHMEM_H
 #define _LINUX_HIGHMEM_H
 
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/bug.h>
 #include <linux/cacheflush.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
 #include <linux/hardirq.h>
 
 #include "highmem-internal.h"
 
 /**
  * kmap - Map a page for long term usage
  * @page:   Pointer to the page to be mapped
  *
  * Returns: The virtual address of the mapping
  *
  * Can only be invoked from preemptible task context because on 32bit
  * systems with CONFIG_HIGHMEM enabled this function might sleep.
  *
  * For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
  * this returns the virtual address of the direct kernel mapping.
  *
  * The returned virtual address is globally visible and valid up to the
  * point where it is unmapped via kunmap(). The pointer can be handed to
  * other contexts.
  *
  * For highmem pages on 32bit systems this can be slow as the mapping space
  * is limited and protected by a global lock. In case that there is no
  * mapping slot available the function blocks until a slot is released via
  * kunmap().
  */
 static inline void *kmap(struct page *page);
 
 /**
  * kunmap - Unmap the virtual address mapped by kmap()
  * @page:   Pointer to the page which was mapped by kmap()
  *
  * Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
  * pages in the low memory area.
  */
 static inline void kunmap(struct page *page);
 
 /**
  * kmap_to_page - Get the page for a kmap'ed address
  * @addr:   The address to look up
  *
  * Returns: The page which is mapped to @addr.
  */
 static inline struct page *kmap_to_page(void *addr);
 
 /**
  * kmap_flush_unused - Flush all unused kmap mappings in order to
  *             remove stray mappings
  */
 static inline void kmap_flush_unused(void);
 
 /**
  * kmap_local_page - Map a page for temporary usage
  * @page: Pointer to the page to be mapped
  *
  * Returns: The virtual address of the mapping
  *
  * Can be invoked from any context, including interrupts.
  *
  * Requires careful handling when nesting multiple mappings because the map
  * management is stack based. The unmap has to be in the reverse order of
  * the map operation:
  *
  * addr1 = kmap_local_page(page1);
  * addr2 = kmap_local_page(page2);
  * ...
  * kunmap_local(addr2);
  * kunmap_local(addr1);
  *
  * Unmapping addr1 before addr2 is invalid and causes malfunction.
  *
  * Contrary to kmap() mappings the mapping is only valid in the context of
  * the caller and cannot be handed to other contexts.
  *
  * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
  * virtual address of the direct mapping. Only real highmem pages are
  * temporarily mapped.
  *
  * While it is significantly faster than kmap() for the higmem case it
  * comes with restrictions about the pointer validity.
  *
  * On HIGHMEM enabled systems mapping a highmem page has the side effect of
  * disabling migration in order to keep the virtual address stable across
  * preemption. No caller of kmap_local_page() can rely on this side effect.
  */
 static inline void *kmap_local_page(struct page *page);
 
 /**
  * kmap_local_folio - Map a page in this folio for temporary usage
  * @folio: The folio containing the page.
  * @offset: The byte offset within the folio which identifies the page.
  *
  * Requires careful handling when nesting multiple mappings because the map
  * management is stack based. The unmap has to be in the reverse order of
  * the map operation::
  *
  *   addr1 = kmap_local_folio(folio1, offset1);
  *   addr2 = kmap_local_folio(folio2, offset2);
  *   ...
  *   kunmap_local(addr2);
  *   kunmap_local(addr1);
  *
  * Unmapping addr1 before addr2 is invalid and causes malfunction.
  *
  * Contrary to kmap() mappings the mapping is only valid in the context of
  * the caller and cannot be handed to other contexts.
  *
  * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
  * virtual address of the direct mapping. Only real highmem pages are
  * temporarily mapped.
  *
  * While it is significantly faster than kmap() for the higmem case it
  * comes with restrictions about the pointer validity. Only use when really
  * necessary.
  *
  * On HIGHMEM enabled systems mapping a highmem page has the side effect of
  * disabling migration in order to keep the virtual address stable across
  * preemption. No caller of kmap_local_folio() can rely on this side effect.
  *
  * Context: Can be invoked from any context.
  * Return: The virtual address of @offset.
  */
 static inline void *kmap_local_folio(struct folio *folio, size_t offset);
 
 /**
  * kmap_atomic - Atomically map a page for temporary usage - Deprecated!
  * @page:   Pointer to the page to be mapped
  *
  * Returns: The virtual address of the mapping
  *
  * In fact a wrapper around kmap_local_page() which also disables pagefaults
  * and, depending on PREEMPT_RT configuration, also CPU migration and
  * preemption. Therefore users should not count on the latter two side effects.
  *
  * Mappings should always be released by kunmap_atomic().
  *
  * Do not use in new code. Use kmap_local_page() instead.
  *
  * It is used in atomic context when code wants to access the contents of a
  * page that might be allocated from high memory (see __GFP_HIGHMEM), for
  * example a page in the pagecache.  The API has two functions, and they
  * can be used in a manner similar to the following::
  *
  *   // Find the page of interest.
  *   struct page *page = find_get_page(mapping, offset);
  *
  *   // Gain access to the contents of that page.
  *   void *vaddr = kmap_atomic(page);
  *
  *   // Do something to the contents of that page.
  *   memset(vaddr, 0, PAGE_SIZE);
  *
  *   // Unmap that page.
  *   kunmap_atomic(vaddr);
  *
  * Note that the kunmap_atomic() call takes the result of the kmap_atomic()
  * call, not the argument.
  *
  * If you need to map two pages because you want to copy from one page to
  * another you need to keep the kmap_atomic calls strictly nested, like:
  *
  * vaddr1 = kmap_atomic(page1);
  * vaddr2 = kmap_atomic(page2);
  *
  * memcpy(vaddr1, vaddr2, PAGE_SIZE);
  *
  * kunmap_atomic(vaddr2);
  * kunmap_atomic(vaddr1);
  */
 static inline void *kmap_atomic(struct page *page);
 
 /* Highmem related interfaces for management code */
 static inline unsigned int nr_free_highpages(void);
 static inline unsigned long totalhigh_pages(void);
 
 #ifndef ARCH_HAS_FLUSH_ANON_PAGE
 static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
 {
 }
 #endif
 
 #ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
 static inline void flush_kernel_vmap_range(void *vaddr, int size)
 {
 }
 static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
 {
 }
 #endif
 
 /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
 #ifndef clear_user_highpage
 static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
 {
     void *addr = kmap_local_page(page);
     clear_user_page(addr, vaddr, page);
     kunmap_local(addr);
 }
 #endif
 
 #ifndef __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE
 /**
  * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM page for a VMA that the caller knows can move
  * @vma: The VMA the page is to be allocated for
  * @vaddr: The virtual address the page will be inserted into
  *
  * Returns: The allocated and zeroed HIGHMEM page
  *
  * This function will allocate a page for a VMA that the caller knows will
  * be able to migrate in the future using move_pages() or reclaimed
  *
  * An architecture may override this function by defining
  * __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE and providing their own
  * implementation.
  */
 static inline struct page *
 alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
                    unsigned long vaddr)
 {
     struct page *page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
 
     if (page)
         clear_user_highpage(page, vaddr);
 
     return page;
 }
 #endif
 
 static inline void clear_highpage(struct page *page)
 {
     void *kaddr = kmap_local_page(page);
     clear_page(kaddr);
     kunmap_local(kaddr);
 }
 
 static inline void clear_highpage_kasan_tagged(struct page *page)
 {
     u8 tag;
 
     tag = page_kasan_tag(page);
     page_kasan_tag_reset(page);
     clear_highpage(page);
     page_kasan_tag_set(page, tag);
 }
 
 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
 
 static inline void tag_clear_highpage(struct page *page)
 {
 }
 
 #endif
 
 /*
  * If we pass in a base or tail page, we can zero up to PAGE_SIZE.
  * If we pass in a head page, we can zero up to the size of the compound page.
  */
 #ifdef CONFIG_HIGHMEM
 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
         unsigned start2, unsigned end2);
 #else
 static inline void zero_user_segments(struct page *page,
         unsigned start1, unsigned end1,
         unsigned start2, unsigned end2)
 {
     void *kaddr = kmap_local_page(page);
     unsigned int i;
 
     BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 
     if (end1 > start1)
         memset(kaddr + start1, 0, end1 - start1);
 
     if (end2 > start2)
         memset(kaddr + start2, 0, end2 - start2);
 
     kunmap_local(kaddr);
     for (i = 0; i < compound_nr(page); i++)
         flush_dcache_page(page + i);
 }
 #endif
 
 static inline void zero_user_segment(struct page *page,
     unsigned start, unsigned end)
 {
     zero_user_segments(page, start, end, 0, 0);
 }
 
 static inline void zero_user(struct page *page,
     unsigned start, unsigned size)
 {
     zero_user_segments(page, start, start + size, 0, 0);
 }
 
 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
 
 static inline void copy_user_highpage(struct page *to, struct page *from,
     unsigned long vaddr, struct vm_area_struct *vma)
 {
     char *vfrom, *vto;
 
     vfrom = kmap_local_page(from);
     vto = kmap_local_page(to);
     copy_user_page(vto, vfrom, vaddr, to);
     kunmap_local(vto);
     kunmap_local(vfrom);
 }
 
 #endif
 
 #ifndef __HAVE_ARCH_COPY_HIGHPAGE
 
 static inline void copy_highpage(struct page *to, struct page *from)
 {
     char *vfrom, *vto;
 
     vfrom = kmap_local_page(from);
     vto = kmap_local_page(to);
     copy_page(vto, vfrom);
     kunmap_local(vto);
     kunmap_local(vfrom);
 }
 
 #endif
 
 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
                    struct page *src_page, size_t src_off,
                    size_t len)
 {
     char *dst = kmap_local_page(dst_page);
     char *src = kmap_local_page(src_page);
 
     VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
     memcpy(dst + dst_off, src + src_off, len);
     kunmap_local(src);
     kunmap_local(dst);
 }
 
 static inline void memset_page(struct page *page, size_t offset, int val,
                    size_t len)
 {
     char *addr = kmap_local_page(page);
 
     VM_BUG_ON(offset + len > PAGE_SIZE);
     memset(addr + offset, val, len);
     kunmap_local(addr);
 }
 
 static inline void memcpy_from_page(char *to, struct page *page,
                     size_t offset, size_t len)
 {
     char *from = kmap_local_page(page);
 
     VM_BUG_ON(offset + len > PAGE_SIZE);
     memcpy(to, from + offset, len);
     kunmap_local(from);
 }
 
 static inline void memcpy_to_page(struct page *page, size_t offset,
                   const char *from, size_t len)
 {
     char *to = kmap_local_page(page);
 
     VM_BUG_ON(offset + len > PAGE_SIZE);
     memcpy(to + offset, from, len);
     flush_dcache_page(page);
     kunmap_local(to);
 }
 
 static inline void memzero_page(struct page *page, size_t offset, size_t len)
 {
     char *addr = kmap_local_page(page);
 
     VM_BUG_ON(offset + len > PAGE_SIZE);
     memset(addr + offset, 0, len);
     flush_dcache_page(page);
     kunmap_local(addr);
 }
 
 /**
  * folio_zero_segments() - Zero two byte ranges in a folio.
  * @folio: The folio to write to.
  * @start1: The first byte to zero.
  * @xend1: One more than the last byte in the first range.
  * @start2: The first byte to zero in the second range.
  * @xend2: One more than the last byte in the second range.
  */
 static inline void folio_zero_segments(struct folio *folio,
         size_t start1, size_t xend1, size_t start2, size_t xend2)
 {
     zero_user_segments(&folio->page, start1, xend1, start2, xend2);
 }
 
 /**
  * folio_zero_segment() - Zero a byte range in a folio.
  * @folio: The folio to write to.
  * @start: The first byte to zero.
  * @xend: One more than the last byte to zero.
  */
 static inline void folio_zero_segment(struct folio *folio,
         size_t start, size_t xend)
 {
     zero_user_segments(&folio->page, start, xend, 0, 0);
 }
 
 /**
  * folio_zero_range() - Zero a byte range in a folio.
  * @folio: The folio to write to.
  * @start: The first byte to zero.
  * @length: The number of bytes to zero.
  */
 static inline void folio_zero_range(struct folio *folio,
         size_t start, size_t length)
 {
     zero_user_segments(&folio->page, start, start + length, 0, 0);
 }
 
 #endif /* _LINUX_HIGHMEM_H */

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