support IA-32e's "execute disable bit"

arch/x86/kernel/cpu.c

@@ -311,9 +311,45 @@ static void enable_page_protection_fault(void)
 	return;
 }
 
+static int no_execute_available = 0;
+
+static void enable_no_execute(void)
+{
+	unsigned long efer;
+
+	if (!no_execute_available) {
+		return;
+	}
+
+	efer = rdmsr(MSR_EFER);
+#define	IA32_EFER_NXE	(1UL << 11)
+	efer |= IA32_EFER_NXE;
+	wrmsr(MSR_EFER, efer);
+
+	return;
+}
+
+static void check_no_execute(void)
+{
+	uint32_t edx;
+	extern void enable_ptattr_no_execute(void);
+
+	/* check Execute Disable Bit available bit */
+	asm ("cpuid" : "=d" (edx) : "a" (0x80000001) : "%rbx", "%rcx");
+	no_execute_available = (edx & (1 << 20))? 1: 0;
+	kprintf("no_execute_available: %d\n", no_execute_available);
+
+	if (no_execute_available) {
+		enable_ptattr_no_execute();
+	}
+
+	return;
+}
+
 void init_cpu(void)
 {
 	enable_page_protection_fault();
+	enable_no_execute();
 	init_fpu();
 	init_lapic();
 	init_syscall();
@@ -330,6 +366,8 @@ void setup_x86(void)
 
 	init_page_table();
 
+	check_no_execute();
+
 	init_cpu();
 
 	kprintf("setup_x86 done.\n");