linux-kernel - [PATCH] [3/5] CPA: Make advised protection check truly advisory

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Message-Id: <20080208132746.34FB51B41BB@basil.firstfloor.org>
Date:	Fri,  8 Feb 2008 14:27:46 +0100 (CET)
From:	Andi Kleen <ak@...e.de>
To:	mingo@...e.hu, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: [PATCH] [3/5] CPA: Make advised protection check truly advisory


Only force RO in the advisory protection checks when all pages in the 
range are RO. Previously it would trigger when any page in the range
was ro.

I believe this will make try_preserve_large_page much safer to use.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86/mm/pageattr.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux/arch/x86/mm/pageattr.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr.c
+++ linux/arch/x86/mm/pageattr.c
@@ -191,14 +191,14 @@ advised_static_prot(pgprot_t prot, unsig
 {
 #ifdef CONFIG_DEBUG_RODATA
 	/* The .rodata section needs to be read-only */
-	if (within_range(start, end, (unsigned long)__start_rodata,
-				(unsigned long)__end_rodata))
+	if (within_range((unsigned long)__start_rodata,
+				(unsigned long)__end_rodata, start, end))
 		pgprot_val(prot) &= ~_PAGE_RW;
 	/*
 	 * Do the same for the x86-64 high kernel mapping
 	 */
-	if (within_range(start, end, virt_to_highmap(__start_rodata),
-				virt_to_highmap(__end_rodata)))
+	if (within_range(virt_to_highmap(__start_rodata),
+				virt_to_highmap(__end_rodata), start, end))
 		pgprot_val(prot) &= ~_PAGE_RW;
 #endif
 	return prot;
--
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