enable syscall instructions

src/arch/x86_64/cpu.c

@@ -0,0 +1,38 @@
+#include <arch/cpu.h>
+#include <arch/msr.h>
+#include <cpuid.h>
+#include <arch/cls.h>
+#include <stdio.h>
+
+// initialises things like 
+// syscall, sse, etc
+// for the current cpu
+
+void cpu_state_init(){
+	
+	// syscall
+
+	// does it exist
+	
+	int eax,ebx,ecx,edx;
+
+	__get_cpuid(0x80000001, &eax, &ebx, &ecx, &edx);
+
+	if(edx & (1 << 11)){ // check for the syscall bit
+		uint64_t efer = rdmsr(MSR_EFER);
+		efer |= 1; // set syscall enable bit
+		wrmsr(MSR_EFER, efer);
+		
+		uint64_t star = 0;
+		star |= (uint64_t)0x28 << 48;
+		star |= (uint64_t)0x28 << 32;
+		
+		wrmsr(MSR_STAR, star);
+		wrmsr(MSR_LSTAR, 0xDEADBEEF); // FIXME add 64 bit handler here
+		wrmsr(MSR_CSTAR, 0); // no compat mode syscall handler
+		wrmsr(MSR_FMASK, 0x200); // disable interrupts on syscall
+	}
+	// undefined opcode exception will handle system calls then
+	else printf("CPU%lu: syscall instruction not supported\n", arch_getcls()->lapicid);
+
+}