Implement fast syscall/sysret for sytem calls

src/drivers/nulldrv/main.s

@@ -8,17 +8,17 @@ _start:
 	xor rbp, rbp	; Sentinel rbp
 
 	mov rax, 5		; GETPID syscall
-	int 0xee
+	syscall ; int 0xee
 	mov [mypid], rax
 
 	mov rax, 8		; FORK syscall
-	int 0xee
+	syscall ; int 0xee
 	mov [mychild], rax
 
 	mov r12, [mypid]
 	mov r13, [mychild]
 	mov rax, 1		; DEBUG syscall
-	int 0xee
+	syscall ; int 0xee
 
 	cmp r12, 1
 	je .dosend
@@ -32,7 +32,7 @@ _start:
 	mov rax, 1		; MESSAGE syscall
 	;mov rax, 0		; NOOP syscall
 	;syscall
-	int 0xee
+	syscall ; int 0xee
 
 	inc r11
 	cmp r11, 2
@@ -41,7 +41,7 @@ _start:
 
 	mov rax, 4		; SLEEP syscall
 	; syscall
-	int 0xee
+	syscall ; int 0xee
 
 	add rbx, 20
 
@@ -51,11 +51,11 @@ _start:
 .dosend:
 	mov rax, 6      ; SEND syscall
 	mov rdi, 2      ; target is pid 2
-	int 0xee
+	syscall ; int 0xee
 	jmp .preloop
 
 .doreceive:
 	mov rax, 7      ; RECEIVE syscall
 	mov rdi, 1      ; source is pid 2
-	int 0xee
+	syscall ; int 0xee
 	jmp .preloop