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

[Andi Kleen]

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@xxxxxxx>

---
 arch/x86/mm/pageattr.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Index: linux/arch/x86/mm/pageattr.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr.c
+++ linux/arch/x86/mm/pageattr.c
@@ -193,14 +193,16 @@ advised_static_prot(pgprot_t prot, unsig
 	pgprot_t forbidden = __pgprot(0);
 
 	/* 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(forbidden) |= _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(forbidden) |= _PAGE_RW;
 
 	prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
--
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