arch/x86/include/asm/pgtable-invert.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_PGTABLE_INVERT_H
   3 #define _ASM_PGTABLE_INVERT_H 1
   4
   5 #ifndef __ASSEMBLY__
   6
   7 static inline bool __pte_needs_invert(u64 val)
   8 {
   9         return (val & (_PAGE_PRESENT|_PAGE_PROTNONE)) == _PAGE_PROTNONE;
  10 }
  11
  12 /* Get a mask to xor with the page table entry to get the correct pfn. */
  13 static inline u64 protnone_mask(u64 val)
  14 {
  15         return __pte_needs_invert(val) ?  ~0ull : 0;
  16 }
  17
  18 static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask)
  19 {
  20         /*
  21          * When a PTE transitions from NONE to !NONE or vice-versa
  22          * invert the PFN part to stop speculation.
  23          * pte_pfn undoes this when needed.
  24          */
  25         if (__pte_needs_invert(oldval) != __pte_needs_invert(val))
  26                 val = (val & ~mask) | (~val & mask);
  27         return val;
  28 }
  29
  30 #endif /* __ASSEMBLY__ */
  31
  32 #endif