diff options
| -rw-r--r-- | arch/arm64/include/asm/pgtable.h | 12 | ||||
| -rw-r--r-- | arch/x86/include/asm/pgtable.h | 12 | ||||
| -rw-r--r-- | include/linux/pgtable.h | 25 |
3 files changed, 49 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 4dfa42b7d053..984f0502c9d0 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1830,6 +1830,18 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, return __ptep_get_and_clear(mm, addr, ptep); } +/* + * Note: strictly-zero compare is narrower than pte_none(), but the gap is + * harmless: a fresh kernel PTE has no software bits set. + */ +static inline bool ptep_try_set(pte_t *ptep, pte_t new_pte) +{ + pteval_t old = 0; + + return try_cmpxchg(&pte_val(*ptep), &old, pte_val(new_pte)); +} +#define ptep_try_set ptep_try_set + #define test_and_clear_young_ptes test_and_clear_young_ptes static inline bool test_and_clear_young_ptes(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, unsigned int nr) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 2187e9cfcefa..ac295ca6c92f 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1284,6 +1284,18 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, } while (!try_cmpxchg((long *)&ptep->pte, (long *)&old_pte, *(long *)&new_pte)); } +/* + * Note: strictly-zero compare is narrower than pte_none(), but the gap is + * harmless: _PAGE_DIRTY and _PAGE_ACCESSED aren't set on untouched kernel PTEs. + */ +static inline bool ptep_try_set(pte_t *ptep, pte_t new_pte) +{ + pte_t old_pte = __pte(0); + + return try_cmpxchg((long *)&ptep->pte, (long *)&old_pte, *(long *)&new_pte); +} +#define ptep_try_set ptep_try_set + #define flush_tlb_fix_spurious_fault(vma, address, ptep) do { } while (0) #define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index cdd68ed3ae1a..b5739bb99fc1 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1036,6 +1036,31 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres } #endif +#ifndef ptep_try_set +/** + * ptep_try_set - atomically set an empty kernel PTE + * @ptep: page table entry + * @new_pte: value to install + * + * Atomically set *@ptep to @new_pte iff *@ptep is pte_none(). Return true on + * success, false if the slot was already populated or the arch has no + * implementation. + * + * For special kernel page tables only - never user page tables. The caller must + * prevent concurrent teardown of @ptep and must accept that other writers may + * race. Concurrent clearers must use ptep_get_and_clear() so racing accesses + * agree on the outcome. + * + * Architectures opt in by providing a cmpxchg-based override and defining + * ptep_try_set as an identity macro. The generic stub returns false, which is + * correct for callers that fall through to oops on failure. + */ +static inline bool ptep_try_set(pte_t *ptep, pte_t new_pte) +{ + return false; +} +#endif + #ifndef wrprotect_ptes /** * wrprotect_ptes - Write-protect PTEs that map consecutive pages of the same |