lguest: map switcher with executable page table entries

Map switcher with executable page table entries.
(This bug didn't matter before PAE and hence NX support -- RR)
Signed-off-by: Matias Zabaljauregui <zabaljauregui@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/core.c

@@ -95,7 +95,7 @@ static __init int map_switcher(void)
 	 * array of struct pages.  It increments that pointer, but we don't
 	 * care. */
 	pagep = switcher_page;
-	err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
+	err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep);
 	if (err) {
 		printk("lguest: map_vm_area failed: %i\n", err);
 		goto free_vma;

drivers/lguest/page_tables.c

@@ -714,7 +714,7 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
 
 	/* Make the last PGD entry for this Guest point to the Switcher's PTE
 	 * page for this CPU (with appropriate flags). */
-	switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL);
+	switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC);
 
 	cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;