linux-kernel - [PATCH 04/12] x86, pkeys: PTE bits

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Message-Id: <20150507174134.427EFE5F@viggo.jf.intel.com>
Date:	Thu, 07 May 2015 10:41:34 -0700
From:	Dave Hansen <dave@...1.net>
To:	dave@...1.net
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH 04/12] x86, pkeys: PTE bits


Previous documentation has referred to these 4 bits as "ignored".
That means that software could have made use of them.  But, as
far as I know, the kernel never used them.

They are still ignored when protection keys is not enabled, so
they could theoretically still get used for software purposes.

---

 b/arch/x86/include/asm/pgtable_types.h |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/pgtable_types.h~pkeys-3-ptebits arch/x86/include/asm/pgtable_types.h
--- a/arch/x86/include/asm/pgtable_types.h~pkeys-3-ptebits	2015-05-07 10:31:42.194223812 -0700
+++ b/arch/x86/include/asm/pgtable_types.h	2015-05-07 10:31:42.198223992 -0700
@@ -25,7 +25,11 @@
 #define _PAGE_BIT_SPLITTING	_PAGE_BIT_SOFTW2 /* only valid on a PSE pmd */
 #define _PAGE_BIT_HIDDEN	_PAGE_BIT_SOFTW3 /* hidden by kmemcheck */
 #define _PAGE_BIT_SOFT_DIRTY	_PAGE_BIT_SOFTW3 /* software dirty tracking */
-#define _PAGE_BIT_NX           63       /* No execute: only valid after cpuid check */
+#define _PAGE_BIT_PKEY_BIT0	59       /* Protection Keys, bit 1/4 */
+#define _PAGE_BIT_PKEY_BIT1	60       /* Protection Keys, bit 2/4 */
+#define _PAGE_BIT_PKEY_BIT2	61       /* Protection Keys, bit 3/4 */
+#define _PAGE_BIT_PKEY_BIT3	62       /* Protection Keys, bit 4/4 */
+#define _PAGE_BIT_NX		63       /* No execute: only valid after cpuid check */
 
 /* If _PAGE_BIT_PRESENT is clear, we use these: */
 /* - if the user mapped it with PROT_NONE; pte_present gives true */
@@ -47,6 +51,10 @@
 #define _PAGE_SPECIAL	(_AT(pteval_t, 1) << _PAGE_BIT_SPECIAL)
 #define _PAGE_CPA_TEST	(_AT(pteval_t, 1) << _PAGE_BIT_CPA_TEST)
 #define _PAGE_SPLITTING	(_AT(pteval_t, 1) << _PAGE_BIT_SPLITTING)
+#define _PAGE_PKEY_BIT0	(_AT(pteval_t, 1) << _PAGE_BIT_PKEY_BIT0)
+#define _PAGE_PKEY_BIT1	(_AT(pteval_t, 1) << _PAGE_BIT_PKEY_BIT1)
+#define _PAGE_PKEY_BIT2	(_AT(pteval_t, 1) << _PAGE_BIT_PKEY_BIT2)
+#define _PAGE_PKEY_BIT3	(_AT(pteval_t, 1) << _PAGE_BIT_PKEY_BIT3)
 #define __HAVE_ARCH_PTE_SPECIAL
 
 #ifdef CONFIG_KMEMCHECK
_
--
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