include/linux/secretmem.h

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 #ifndef _LINUX_SECRETMEM_H
   3 #define _LINUX_SECRETMEM_H
   4
   5 #ifdef CONFIG_SECRETMEM
   6
   7 extern const struct address_space_operations secretmem_aops;
   8
   9 static inline bool page_is_secretmem(struct page *page)
  10 {
  11         struct address_space *mapping;
  12
  13         /*
  14          * Using page_mapping() is quite slow because of the actual call
  15          * instruction and repeated compound_head(page) inside the
  16          * page_mapping() function.
  17          * We know that secretmem pages are not compound and LRU so we can
  18          * save a couple of cycles here.
  19          */
  20         if (PageCompound(page) || !PageLRU(page))
  21                 return false;
  22
  23         mapping = (struct address_space *)
  24                 ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
  25
  26         if (mapping != page->mapping)
  27                 return false;
  28
  29         return mapping->a_ops == &secretmem_aops;
  30 }
  31
  32 bool vma_is_secretmem(struct vm_area_struct *vma);
  33 bool secretmem_active(void);
  34
  35 #else
  36
  37 static inline bool vma_is_secretmem(struct vm_area_struct *vma)
  38 {
  39         return false;
  40 }
  41
  42 static inline bool page_is_secretmem(struct page *page)
  43 {
  44         return false;
  45 }
  46
  47 static inline bool secretmem_active(void)
  48 {
  49         return false;
  50 }
  51
  52 #endif /* CONFIG_SECRETMEM */
  53
  54 #endif /* _LINUX_SECRETMEM_H */