include/linux/secretmem.h

0001 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
0002 #ifndef _LINUX_SECRETMEM_H
0003 #define _LINUX_SECRETMEM_H
0004
0005 #ifdef CONFIG_SECRETMEM
0006
0007 extern const struct address_space_operations secretmem_aops;
0008
0009 static inline bool page_is_secretmem(struct page *page)
0010 {
0011     struct address_space *mapping;
0012
0013     /*
0014      * Using page_mapping() is quite slow because of the actual call
0015      * instruction and repeated compound_head(page) inside the
0016      * page_mapping() function.
0017      * We know that secretmem pages are not compound and LRU so we can
0018      * save a couple of cycles here.
0019      */
0020     if (PageCompound(page) || !PageLRU(page))
0021         return false;
0022
0023     mapping = (struct address_space *)
0024         ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
0025
0026     if (!mapping || mapping != page->mapping)
0027         return false;
0028
0029     return mapping->a_ops == &secretmem_aops;
0030 }
0031
0032 bool vma_is_secretmem(struct vm_area_struct *vma);
0033 bool secretmem_active(void);
0034
0035 #else
0036
0037 static inline bool vma_is_secretmem(struct vm_area_struct *vma)
0038 {
0039     return false;
0040 }
0041
0042 static inline bool page_is_secretmem(struct page *page)
0043 {
0044     return false;
0045 }
0046
0047 static inline bool secretmem_active(void)
0048 {
0049     return false;
0050 }
0051
0052 #endif /* CONFIG_SECRETMEM */
0053
0054 #endif /* _LINUX_SECRETMEM_H */