Turn on EFER NXE bit to allow no-execute pages

src/hulk/cpu.d

@@ -5,7 +5,20 @@ module hulk.cpu;
 
 import ldc.llvmasm;
 
+/** MSR register numbers. @{ */
 enum uint MSR_EFER = 0xC000_0080u;
+/** @} */
+
+/** EFER flags. @{ */
+enum uint EFER_SCE = 0x1u;
+enum uint EFER_LME = 0x100u;
+enum uint EFER_LMA = 0x400u;
+enum uint EFER_NXE = 0x800u;
+enum uint EFER_SVME = 0x1000u;
+enum uint EFER_LMSLE = 0x2000u;
+enum uint EFER_FFXSR = 0x4000u;
+enum uint EFER_TCE = 0x8000u;
+/** @} */
 
 void cli()
 {
@@ -55,6 +68,11 @@ ulong rdmsr(uint msr)
             or %rdx, %rax`, "={rax},{ecx},~{rdx}", msr);
 }
 
+void wrmsr(uint msr, ulong value)
+{
+    __asm(`wrmsr`, "{ecx},{edx},{eax}", msr, value >> 32u, value);
+}
+
 ubyte in8(ushort ioaddr)
 {
     return __asm!ubyte("inb %dx, %al", "={al},{dx}", ioaddr);