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 <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Link: http://lkml.kernel.org/r/1367476850.5660.2.camel@nexus
Cc: <[email protected]> v3.9

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 101ac1a9263ef755508dcc74a73818ed048376ca..dab95a85f7f8590d240790e981830ea91f729cdd 100644 (file)
--- 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 6859e962644216747de33f8f6fec331f67e24f7f..08f7e8039099dc6b8787bbad4797553d7da6ac3f 100644 (file)
--- 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 */