cmd/earlyinit: mount system device

This currently relies on a trusted bootloader to determine the boot device.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/earlyinit/uevent_test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"testing"
+	"testing/synctest"
+	"time"
+)
+
+func TestRejectColdboot(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		nextColdboot := newRejectColdboot()
+		want := func(want bool) {
+			if got := nextColdboot(); got != want {
+				t.Fatalf("nextColdboot: %v, want %v", got, want)
+			}
+		}
+
+		synctest.Wait()
+		want(true)
+		time.Sleep(time.Hour)
+		synctest.Wait()
+		want(true)
+		want(true)
+		time.Sleep(5 * time.Minute)
+		synctest.Wait()
+		want(true)
+		want(false)
+		time.Sleep(time.Hour)
+		synctest.Wait()
+		want(false)
+		want(false)
+	})
+}