+static int disable_nx __initdata = 0;
+u64 __supported_pte_mask = ~_PAGE_NX;
+
+/*
+ * noexec = on|off
+ *
+ * Control non executable mappings.
+ *
+ * on Enable
+ * off Disable
+ */
+static int __init noexec_setup(char *str)
+{
+ if (!strncmp(str, "on",2) && cpu_has_nx) {
+ __supported_pte_mask |= _PAGE_NX;
+ disable_nx = 0;
+ } else if (!strncmp(str,"off",3)) {
+ disable_nx = 1;
+ __supported_pte_mask &= ~_PAGE_NX;
+ }
+ return 1;
+}
+
+__setup("noexec=", noexec_setup);
+
+#ifdef CONFIG_X86_PAE
+int nx_enabled = 0;
+
+static void __init set_nx(void)
+{
+ unsigned int v[4], l, h;
+
+ if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
+ cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
+ if ((v[3] & (1 << 20)) && !disable_nx) {
+ rdmsr(MSR_EFER, l, h);
+ l |= EFER_NX;
+ wrmsr(MSR_EFER, l, h);
+ nx_enabled = 1;
+ __supported_pte_mask |= _PAGE_NX;
+ }
+ }
+}
+
+/*
+ * Enables/disables executability of a given kernel page and
+ * returns the previous setting.
+ */
+int __init set_kernel_exec(unsigned long vaddr, int enable)
+{
+ pte_t *pte;
+ int ret = 1;
+
+ if (!nx_enabled)
+ goto out;
+
+ pte = lookup_address(vaddr);
+ BUG_ON(!pte);
+
+ if (!pte_exec_kernel(*pte))
+ ret = 0;
+
+ if (enable)
+ pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
+ else
+ pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
+ __flush_tlb_all();
+out:
+ return ret;
+}
+
+#endif
+