[PATCH] x86, 64bit: do not assume CPU is NX capable when settingearly page tables

[Fernando Luis Vázquez Cao]

The kernel sets the NX bit in the early page tables without checking whether
the CPU actually supports this feature. If it doesn't the first attempt to use
them will cause a kernel hang. Since these are temporary page tables marked as
initdata this fix takes the approach of not bothering with the NX bit at all.

Noticed when my AMD machine that happened to have the NX feature disabled by
the BIOS failed to boot after the update to 3.9.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---

diff -urNp linux-3.9/arch/x86/kernel/head64.c linux-3.9-fix/arch/x86/kernel/head64.c
--- linux-3.9/arch/x86/kernel/head64.c	2013-04-29 09:36:01.000000000 +0900
+++ linux-3.9-fix/arch/x86/kernel/head64.c	2013-05-02 14:38:52.589276092 +0900
@@ -99,7 +99,7 @@ again:
 			pmd_p[i] = 0;
 		*pud_p = (pudval_t)pmd_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
 	}
-	pmd = (physaddr & PMD_MASK) + (__PAGE_KERNEL_LARGE & ~_PAGE_GLOBAL);
+	pmd = (physaddr & PMD_MASK) + (__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL);
 	pmd_p[pmd_index(address)] = pmd;
 
 	return 0;


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