[4.2.y-ckt stable] Patch "arm64: Ensure pmd_present() returns false after pmd_mknotpresent()" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    arm64: Ensure pmd_present() returns false after pmd_mknotpresent()

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 7fdd3ab35e9460672c6d3add0761f4129cb091d9 Mon Sep 17 00:00:00 2001
From: Catalin Marinas <catalin.marinas at arm.com>
Date: Thu, 5 May 2016 10:44:02 +0100
Subject: arm64: Ensure pmd_present() returns false after pmd_mknotpresent()

commit 5bb1cc0ff9a6b68871970737e6c4c16919928d8b upstream.

Currently, pmd_present() only checks for a non-zero value, returning
true even after pmd_mknotpresent() (which only clears the type bits).
This patch converts pmd_present() to using pte_present(), similar to the
other pmd_*() checks. As a side effect, it will return true for
PROT_NONE mappings, though they are not yet used by the kernel with
transparent huge pages.

For consistency, also change pmd_mknotpresent() to only clear the
PMD_SECT_VALID bit, even though the PMD_TABLE_BIT is already 0 for block
mappings (no functional change). The unused PMD_SECT_PROT_NONE
definition is removed as transparent huge pages use the pte page prot
values.

Fixes: 9c7e535fcc17 ("arm64: mm: Route pmd thp functions through pte equivalents")
Reviewed-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm64/include/asm/pgtable-hwdef.h | 1 -
 arch/arm64/include/asm/pgtable.h       | 4 ++--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 59bfae7..d007a7b 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -77,7 +77,6 @@
  * Section
  */
 #define PMD_SECT_VALID		(_AT(pmdval_t, 1) << 0)
-#define PMD_SECT_PROT_NONE	(_AT(pmdval_t, 1) << 58)
 #define PMD_SECT_USER		(_AT(pmdval_t, 1) << 6)		/* AP[1] */
 #define PMD_SECT_RDONLY		(_AT(pmdval_t, 1) << 7)		/* AP[2] */
 #define PMD_SECT_S		(_AT(pmdval_t, 3) << 8)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 526a9cb..f1fc314 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -285,6 +285,7 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

+#define pmd_present(pmd)	pte_present(pmd_pte(pmd))
 #define pmd_dirty(pmd)		pte_dirty(pmd_pte(pmd))
 #define pmd_young(pmd)		pte_young(pmd_pte(pmd))
 #define pmd_wrprotect(pmd)	pte_pmd(pte_wrprotect(pmd_pte(pmd)))
@@ -293,7 +294,7 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
 #define pmd_mkwrite(pmd)	pte_pmd(pte_mkwrite(pmd_pte(pmd)))
 #define pmd_mkdirty(pmd)	pte_pmd(pte_mkdirty(pmd_pte(pmd)))
 #define pmd_mkyoung(pmd)	pte_pmd(pte_mkyoung(pmd_pte(pmd)))
-#define pmd_mknotpresent(pmd)	(__pmd(pmd_val(pmd) & ~PMD_TYPE_MASK))
+#define pmd_mknotpresent(pmd)	(__pmd(pmd_val(pmd) & ~PMD_SECT_VALID))

 #define __HAVE_ARCH_PMD_WRITE
 #define pmd_write(pmd)		pte_write(pmd_pte(pmd))
@@ -332,7 +333,6 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 				     unsigned long size, pgprot_t vma_prot);

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

 #define pmd_bad(pmd)		(!(pmd_val(pmd) & 2))

--
2.7.4