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 <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Venkatesh Pallipadi <[email protected]>
Cc: Suresh Siddha <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Tim Starling <[email protected]>
Cc: Hannes Eder <[email protected]>
LKML-Reference: <[email protected]>
Acked-by: Kees Cook <[email protected]>

Author: H. Peter Anvin

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);
 }
 

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);