x86, pageattr: Make set_memory_(x|nx) aware of NX support

Make set_memory_x/set_memory_nx directly aware of if NX is supported
in the system or not, rather than requiring that every caller assesses
that support independently.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tim Starling <tstarling@wikimedia.org>
Cc: Hannes Eder <hannes@hanneseder.net>
LKML-Reference: <1258154897-6770-4-git-send-email-hpa@zytor.com>
Acked-by: Kees Cook <kees.cook@canonical.com>

2 files changed, 8 insertions, 4 deletions

diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index c1c429d00130..03657e784fd8 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -157,8 +157,7 @@ int machine_kexec_prepare(struct kimage *image)
 {
         int error;
 
-        if (nx_enabled)
-                set_pages_x(image->control_code_page, 1);
+        set_pages_x(image->control_code_page, 1);
         error = machine_kexec_alloc_page_tables(image);
         if (error)
                 return error;
@@ -172,8 +171,7 @@ int machine_kexec_prepare(struct kimage *image)
  */
 void machine_kexec_cleanup(struct kimage *image)
 {
-        if (nx_enabled)
-                set_pages_nx(image->control_code_page, 1);
+        set_pages_nx(image->control_code_page, 1);
         machine_kexec_free_page_tables(image);
 }
 
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 09a140ca7be8..1d4eb93d333c 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1085,12 +1085,18 @@ EXPORT_SYMBOL(set_memory_array_wb);
 
 int set_memory_x(unsigned long addr, int numpages)
 {
+        if (!(__supported_pte_mask & _PAGE_NX))
+                return 0;
+
         return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_x);
 
 int set_memory_nx(unsigned long addr, int numpages)
 {
+        if (!(__supported_pte_mask & _PAGE_NX))
+                return 0;
+
         return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_nx);