[RFC 4/4] arm64/mm: Enable ARCH_SUPPORTS_LAZY_EXEC

[Anshuman Khandual <anshuman.khandual@arm.com>]

Make arm64 subscribe to ARCH_SUPPORTS_LAZY_EXEC framework and provided all
required helpers for this purpose. This moves away execution cost from the
migration path to exec fault path as expected.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/Kconfig               |  1 +
 arch/arm64/include/asm/pgtable.h | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a4168d3..3cdb3e4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -59,6 +59,7 @@ config ARM64
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
+	select ARCH_SUPPORTS_LAZY_EXEC
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index de70c1e..f2a5716 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -217,6 +217,18 @@ static inline pmd_t pmd_mkcont(pmd_t pmd)
 	return __pmd(pmd_val(pmd) | PMD_SECT_CONT);
 }
 
+#ifdef CONFIG_ARCH_SUPPORTS_LAZY_EXEC
+static inline pte_t pte_mkexec(pte_t pte)
+{
+	return clear_pte_bit(pte, __pgprot(PTE_UXN));
+}
+
+static inline pte_t pte_mklazyexec(pte_t pte)
+{
+	return set_pte_bit(pte, __pgprot(PTE_UXN));
+}
+#endif
+
 static inline void set_pte(pte_t *ptep, pte_t pte)
 {
 	WRITE_ONCE(*ptep, pte);
@@ -355,6 +367,11 @@ static inline int pmd_protnone(pmd_t pmd)
 }
 #endif
 
+#ifdef CONFIG_ARCH_SUPPORTS_LAZY_EXEC
+#define pmd_mkexec(pmd)		pte_pmd(pte_mkexec(pmd_pte(pmd)))
+#define pmd_mklazyexec(pmd)	pte_pmd(pte_mklazyexec(pmd_pte(pmd)))
+#endif
+
 /*
  * THP definitions.
  */
-- 
2.7.4