x86-64, init: Do not set NX bits on non-NX capable hardware

During early init, we would incorrectly set the NX bit even if the NX
feature was not supported.  Instead, only set this bit if NX is
actually available and enabled.  We already do very early detection of
the NX bit to enable it in EFER, this simply extends this detection to
the early page table mask.

Reported-by: Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1367476850.5660.2.camel@nexus
Cc: <stable@vger.kernel.org> v3.9

2 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 101ac1a9263e..dab95a85f7f8 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -34,6 +34,7 @@
 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
 extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
 static unsigned int __initdata next_early_pgt = 2;
+pmdval_t __initdata early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 /* Wipe all early page tables except for the kernel symbol map */
 static void __init reset_early_page_tables(void)
@@ -99,7 +100,7 @@ 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) + early_pmd_flags;
         pmd_p[pmd_index(address)] = pmd;
 
         return 0;
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 6859e9626442..08f7e8039099 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -200,6 +200,7 @@ ENTRY(secondary_startup_64)
         btl     $20,%edi                /* No Execute supported? */
         jnc     1f
         btsl    $_EFER_NX, %eax
+        btsq    $_PAGE_BIT_NX,early_pmd_flags(%rip)
 1:      wrmsr                           /* Make changes effective */
 
         /* Setup cr0 */