LXR linux/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/*
   8 * A clear pte value is special, and doesn't get inverted.
   9 *
  10 * Note that even users that only pass a pgprot_t (rather
  11 * than a full pte) won't trigger the special zero case,
  12 * because even PAGE_NONE has _PAGE_PROTNONE | _PAGE_ACCESSED
  13 * set. So the all zero case really is limited to just the
  14 * cleared page table entry case.
  15 */
  16static inline bool __pte_needs_invert(u64 val)
  17{
  18        return val && !(val & _PAGE_PRESENT);
  19}
  20
  21/* Get a mask to xor with the page table entry to get the correct pfn. */
  22static inline u64 protnone_mask(u64 val)
  23{
  24        return __pte_needs_invert(val) ?  ~0ull : 0;
  25}
  26
  27static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask)
  28{
  29        /*
  30         * When a PTE transitions from NONE to !NONE or vice-versa
  31         * invert the PFN part to stop speculation.
  32         * pte_pfn undoes this when needed.
  33         */
  34        if (__pte_needs_invert(oldval) != __pte_needs_invert(val))
  35                val = (val & ~mask) | (~val & mask);
  36        return val;
  37}
  38
  39#endif /* __ASSEMBLY__ */
  40
  41#endif
  42