linux-kernel - [PATCH 07/26] x86, pkeys: new page fault error code bit: PF

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Date:	Wed, 16 Sep 2015 10:49:05 -0700
From:	Dave Hansen <dave@...1.net>
To:	dave@...1.net
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 07/26] x86, pkeys: new page fault error code bit: PF_PK


Note: "PK" is how the Intel SDM refers to this bit, so we also
use that nomenclature.

This only defines the bit, it does not plumb it anywhere to be
handled.

---

 b/arch/x86/mm/fault.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff -puN arch/x86/mm/fault.c~pkeys-05-pfec arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~pkeys-05-pfec	2015-09-16 10:48:14.219099976 -0700
+++ b/arch/x86/mm/fault.c	2015-09-16 10:48:14.222100112 -0700
@@ -33,6 +33,7 @@
  *   bit 2 ==	 0: kernel-mode access	1: user-mode access
  *   bit 3 ==				1: use of reserved bit detected
  *   bit 4 ==				1: fault was an instruction fetch
+ *   bit 5 ==				1: protection keys block access
  */
 enum x86_pf_error_code {
 
@@ -41,6 +42,7 @@ enum x86_pf_error_code {
 	PF_USER		=		1 << 2,
 	PF_RSVD		=		1 << 3,
 	PF_INSTR	=		1 << 4,
+	PF_PK		=		1 << 5,
 };
 
 /*
@@ -916,7 +918,10 @@ static int spurious_fault_check(unsigned
 
 	if ((error_code & PF_INSTR) && !pte_exec(*pte))
 		return 0;
-
+	/*
+	 * Note: We do not do lazy flushing on protection key
+	 * changes, so no spurious fault will ever set PF_PK.
+	 */
 	return 1;
 }
 
_
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