Define type for kernel error messages

Since the Go memory allocator is not available to us we need to define
our own error type.

kernel/error.go

@@ -0,0 +1,18 @@
+package kernel
+
+// Error describes a kernel kerror. All kernel errors must be defined as global
+// variables that are pointers to the Error structure. This requirement stems
+// from the fact that the Go allocator is not available to us so we cannot use
+// errors.New.
+type Error struct {
+	// The module where the error occurred.
+	Module string
+
+	// The error message
+	Message string
+}
+
+// Error implements the error interface.
+func (e *Error) Error() string {
+	return e.Message
+}

kernel/error_test.go

@@ -0,0 +1,14 @@
+package kernel
+
+import "testing"
+
+func TestKernelError(t *testing.T) {
+	err := &Error{
+		Module:  "foo",
+		Message: "error message",
+	}
+
+	if err.Error() != err.Message {
+		t.Fatalf("expected to err.Error() to return %q; got %q", err.Message, err.Error())
+	}
+}