support 'syscall' instruction by handling invalid opcode exception

kernel/src/arch/x86_64/interrupt/handler.rs

@@ -96,7 +96,8 @@ pub extern fn rust_trap(tf: &mut TrapFrame) {
         SwitchToUser => to_user(tf),
         Syscall => syscall(tf),
         Syscall32 => syscall32(tf),
-        DivideError | GeneralProtectionFault | InvalidOpcode => error(tf),
+        InvalidOpcode => invalid_opcode(tf),
+        DivideError | GeneralProtectionFault => error(tf),
         _ => panic!("Unhandled interrupt {:x}", tf.trap_num),
     }
 }
@@ -172,6 +173,18 @@ fn syscall32(tf: &mut TrapFrame) {
     tf.rax = ret as usize;
 }
 
+/// Support `syscall` instruction
+fn invalid_opcode(tf: &mut TrapFrame) {
+    let opcode = unsafe { (tf.rip as *mut u16).read() };
+    const SYSCALL_OPCODE: u16 = 0x05_0f;
+    if opcode == SYSCALL_OPCODE {
+        syscall(tf);
+        tf.rip += 2;
+    } else {
+        crate::trap::error(tf);
+    }
+}
+
 fn error(tf: &TrapFrame) {
     crate::trap::error(tf);
 }