x86, mm: Clean up and simplify NX enablement

The 32- and 64-bit code used very different mechanisms for enabling
NX, but even the 32-bit code was enabling NX in head_32.S if it is
available.  Furthermore, we had a bewildering collection of tests for
the available of NX.

This patch:

a) merges the 32-bit set_nx() and the 64-bit check_efer() function
   into a single x86_configure_nx() function.  EFER control is left
   to the head code.

b) eliminates the nx_enabled variable entirely.  Things that need to
   test for NX enablement can verify __supported_pte_mask directly,
   and cpu_has_nx gives the supported status of NX.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Vegard Nossum <vegardno@ifi.uio.no>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Chris Wright <chrisw@sous-sol.org>
LKML-Reference: <1258154897-6770-5-git-send-email-hpa@zytor.com>
Acked-by: Kees Cook <kees.cook@canonical.com>

1 files changed, 2 insertions, 6 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0a6e94ab8339..23b7f46bf843 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -787,21 +787,17 @@ void __init setup_arch(char **cmdline_p)
         strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
         *cmdline_p = command_line;
 
-#ifdef CONFIG_X86_64
         /*
          * Must call this twice: Once just to detect whether hardware doesn't
          * support NX (so that the early EHCI debug console setup can safely
          * call set_fixmap(), and then again after parsing early parameters to
          * honor the respective command line option.
          */
-        check_efer();
-#endif
+        x86_configure_nx();
 
         parse_early_param();
 
-#ifdef CONFIG_X86_64
-        check_efer();
-#endif
+        x86_configure_nx();
 
         /* Must be before kernel pagetables are setup */
         vmi_activate();