[PATCH 3.16 181/305] ARM: 8578/1: mm: ensure pmd_present only checks the valid bit

Ben Hutchings
2016-08-14T17:59:01Z

From: Will Deacon <will.deacon@arm.com>

commit 624531886987f0f1b5d01fb598034d039198e090 upstream.

In a subsequent patch, pmd_mknotpresent will clear the valid bit of the
pmd entry, resulting in a not-present entry from the hardware's
perspective. Unfortunately, pmd_present simply checks for a non-zero pmd
value and will therefore continue to return true even after a
pmd_mknotpresent operation. Since pmd_mknotpresent is only used for
managing huge entries, this is only an issue for the 3-level case.

This patch fixes the 3-level pmd_present implementation to take into
account the valid bit. For bisectability, the change is made before the
fix to pmd_mknotpresent.

[catalin.marinas@arm.com: comment update regarding pmd_mknotpresent patch]

Fixes: 8d9625070073 ("ARM: mm: Transparent huge page support for LPAE systems.")
Cc: Russell King <linux@armlinux.org.uk>
Cc: Steve Capper <Steve.Capper@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/arm/include/asm/pgtable-2level.h | 1 +
arch/arm/include/asm/pgtable-3level.h | 1 +
arch/arm/include/asm/pgtable.h | 1 -
3 files changed, 2 insertions(+), 1 deletion(-)

--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/arch/arm/include/asm/pgtable-2level.h
@@ -163,6 +163,7 @@ static inline pmd_t *pmd_offset(pud_t *p

#define pmd_large(pmd) (pmd_val(pmd) & 2)
#define pmd_bad(pmd) (pmd_val(pmd) & 2)
+#define pmd_present(pmd) (pmd_val(pmd))

#define copy_pmd(pmdpd,pmdps) \
do { \
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -212,6 +212,7 @@ static inline pmd_t *pmd_offset(pud_t *p
: !!(pmd_val(pmd) & (val)))
#define pmd_isclear(pmd, val) (!(pmd_val(pmd) & (val)))

+#define pmd_present(pmd) (pmd_isset((pmd), L_PMD_SECT_VALID))
#define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF))

#define __HAVE_ARCH_PMD_WRITE
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -182,7 +182,6 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD
#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)

#define pmd_none(pmd) (!pmd_val(pmd))
-#define pmd_present(pmd) (pmd_val(pmd))

static inline pte_t *pmd_page_vaddr(pmd_t pmd)
{