[PATCH 14/24] alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support

[Matt Turner]

Add the page table check helpers needed for CONFIG_PAGE_TABLE_CHECK
and select ARCH_SUPPORTS_PAGE_TABLE_CHECK in Kconfig.

Alpha does not support huge pages, so pmd_user_accessible_page() and
pud_user_accessible_page() always return false. pte_user_accessible_page()
checks for present PTEs with user read access (_PAGE_URE).

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>
---
 arch/alpha/Kconfig               |  1 +
 arch/alpha/include/asm/pgtable.h | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 4c38405cd6cd..d7e2859aaedb 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -17,6 +17,7 @@ config ALPHA
 	select ARCH_NO_SG_CHAIN
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
+	select ARCH_SUPPORTS_PAGE_TABLE_CHECK
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
diff --git ./arch/alpha/include/asm/pgtable.h ./arch/alpha/include/asm/pgtable.h
index bdff33b505bc..310361920a1f 100644
--- ./arch/alpha/include/asm/pgtable.h
+++ ./arch/alpha/include/asm/pgtable.h
@@ -232,6 +232,22 @@ extern inline void pud_clear(pud_t * pudp)	{ pud_val(*pudp) = 0; }
 extern inline int pte_write(pte_t pte)		{ return !(pte_val(pte) & _PAGE_FOW); }
 extern inline int pte_dirty(pte_t pte)		{ return pte_val(pte) & _PAGE_DIRTY; }
 extern inline int pte_young(pte_t pte)		{ return pte_val(pte) & _PAGE_ACCESSED; }
+extern inline int pte_user(pte_t pte)		{ return pte_val(pte) & _PAGE_URE; }
+
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && pte_user(pte);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd, unsigned long addr)
+{
+	return false;
+}
+
+static inline bool pud_user_accessible_page(pud_t pud, unsigned long addr)
+{
+	return false;
+}
 
 extern inline pte_t pte_wrprotect(pte_t pte)	{ pte_val(pte) |= _PAGE_FOW; return pte; }
 extern inline pte_t pte_mkclean(pte_t pte)	{ pte_val(pte) &= ~(__DIRTY_BITS); return pte; }
-- 
2.54.0