[PATCH] NX protection for kernel data : fix xen boot

[matthieu castet <castet.matthieu@free.fr>]

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I think it should be applied before 2.6.38 release, because without
this patch xen doesn't boot on x86_32 with CONFIG_DEBUG_RODATA.


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>From 08f54ec4007ab0df231d81ed436632aa7f605feb Mon Sep 17 00:00:00 2001
From: Matthieu CASTET <castet.matthieu@free.fr>
Date: Thu, 20 Jan 2011 21:11:45 +0100
Subject: [PATCH] NX protection for kernel data : fix xen boot

Xen want page table pages read only.

But the initial page table (from head_*.S) live in .data or .bss.

That was broken by 64edc8ed5ffae999d8d413ba006850e9e34166cb.
Revert the problematic part as it is only a protection and
not really needed.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/mm/pageattr.c |    8 --------
 1 files changed, 0 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 2ad6c48..951eb4a 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -256,7 +256,6 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
 				   unsigned long pfn)
 {
 	pgprot_t forbidden = __pgprot(0);
-	pgprot_t required = __pgprot(0);
 
 	/*
 	 * The BIOS area between 640k and 1Mb needs to be executable for
@@ -286,12 +285,6 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
 	if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
 		   __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
 		pgprot_val(forbidden) |= _PAGE_RW;
-	/*
-	 * .data and .bss should always be writable.
-	 */
-	if (within(address, (unsigned long)_sdata, (unsigned long)_edata) ||
-	    within(address, (unsigned long)__bss_start, (unsigned long)__bss_stop))
-		pgprot_val(required) |= _PAGE_RW;
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
 	/*
@@ -331,7 +324,6 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
 #endif
 
 	prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
-	prot = __pgprot(pgprot_val(prot) | pgprot_val(required));
 
 	return prot;
 }
-- 
1.7.2.3