[PATCH v2 1/2] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE

[aneesh.kumar at kernel.org]

From: "Aneesh Kumar K.V (IBM)" <aneesh.kumar at kernel.org>

There used to be a dependency on _PAGE_PRIVILEGED with pte_savedwrite.
But that got dropped by
commit 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite")

With the change in this patch numa fault pte (pte_protnone()) gets mapped as regular user pte
with RWX cleared (no-access) whereas earlier it used to be mapped _PAGE_PRIVILEGED.

Hash fault handling code gets some WARN_ON added in this patch because
those functions are not expected to get called with _PAGE_READ cleared.
commit 18061c17c8ec ("powerpc/mm: Update PROTFAULT handling in the page
fault path") explains the details.

Signed-off-by: Aneesh Kumar K.V (IBM) <aneesh.kumar at kernel.org>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 10 ++--------
 arch/powerpc/mm/book3s64/hash_utils.c        |  7 +++++++
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index cb77eddca54b..927d585652bc 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -17,12 +17,6 @@
 #define _PAGE_EXEC		0x00001 /* execute permission */
 #define _PAGE_WRITE		0x00002 /* write access allowed */
 #define _PAGE_READ		0x00004	/* read access allowed */
-#define _PAGE_NA		_PAGE_PRIVILEGED
-#define _PAGE_NAX		_PAGE_EXEC
-#define _PAGE_RO		_PAGE_READ
-#define _PAGE_ROX		(_PAGE_READ | _PAGE_EXEC)
-#define _PAGE_RW		(_PAGE_READ | _PAGE_WRITE)
-#define _PAGE_RWX		(_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)
 #define _PAGE_PRIVILEGED	0x00008 /* kernel access only */
 #define _PAGE_SAO		0x00010 /* Strong access order */
 #define _PAGE_NON_IDEMPOTENT	0x00020 /* non idempotent memory */
@@ -532,8 +526,8 @@ static inline bool pte_user(pte_t pte)
 static inline bool pte_access_permitted(pte_t pte, bool write)
 {
 	/*
-	 * _PAGE_READ is needed for any access and will be
-	 * cleared for PROT_NONE
+	 * _PAGE_READ is needed for any access and will be cleared for
+	 * PROT_NONE. Execute-only mapping via PROT_EXEC also returns false.
 	 */
 	if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
 		return false;
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index ad2afa08e62e..0626a25b0d72 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -310,9 +310,16 @@ unsigned long htab_convert_pte_flags(unsigned long pteflags, unsigned long flags
 			else
 				rflags |= 0x3;
 		}
+		VM_WARN_ONCE(!(pteflags & _PAGE_RWX), "no-access mapping request");
 	} else {
 		if (pteflags & _PAGE_RWX)
 			rflags |= 0x2;
+		/*
+		 * We should never hit this in normal fault handling because
+		 * a permission check (check_pte_access()) will bubble this
+		 * to higher level linux handler even for PAGE_NONE.
+		 */
+		VM_WARN_ONCE(!(pteflags & _PAGE_RWX), "no-access mapping request");
 		if (!((pteflags & _PAGE_WRITE) && (pteflags & _PAGE_DIRTY)))
 			rflags |= 0x1;
 	}
-- 
2.43.0