init: allow force loading of extra modules via the kernel command-line

[Anatol]: change parameter name to `rd.modules_force_load'; add integration test

Fixes #186

docs/manpage.md

@@ -117,6 +117,7 @@ Some parts of booster boot functionality can be modified with kernel boot parame
  * `rd.luks.key=$UUID=$PATH` absolute path to a keyfile in the initrd/initramfs which can be unsed to unlock the device identified by UUID, if this file does not exist or fails to unlock it will fall back to a password request.
  * `rd.luks.options=opt1,opt2` a comma-separated list of LUKS flags. Supported options are `discard`, `same-cpu-crypt`, `submit-from-crypt-cpus`, `no-read-workqueue`, `no-write-workqueue`.
     Note that booster also supports LUKS v2 persistent flags stored with the partition metadata. Any command-line options are added on top of the persistent flags.
+ * `rd.modules_force_load` a comma-separated list of extra kernel modules which should be force loaded.
  * `resume=$deviceref` device reference to suspend-to-disk device.
  * `zfs=$pool/$dataset` specifies what ZFS dataset needs to be used for root partition. This option is only used if ZFS config option is enabled. If ZFS filesystem is enabled then `root=` boot param is ignored.
  * `booster.log` configures booster init logging. It accepts a comma separated list of following values:

init/cmdline.go

@@ -192,7 +192,13 @@ func parseParams(params string) error {
 			if err != nil {
 				return fmt.Errorf("root=%s: %v", value, err)
 			}
+		case "rd.modules_force_load":
+			if value == "" {
+				break
+			}
 
+			modules := strings.Split(value, ",")
+			config.ModulesForceLoad = append(config.ModulesForceLoad, modules...)
 		case "resume":
 			var err error
 			cmdResume, err = parseDeviceRef(value)

tests/integration_test.go

@@ -224,3 +224,16 @@ func TestUsb(t *testing.T) {
 
 	require.NoError(t, vm.ConsoleExpect("Hello, booster!"))
 }
+
+func TestLoadExtraModules(t *testing.T) {
+	vm, err := buildVmInstance(t, Opts{
+		disk:       "assets/ext4.img",
+		kernelArgs: []string{"root=LABEL=atestlabel12", "rd.modules_force_load=foo,xfs"},
+	})
+	require.NoError(t, err)
+	defer vm.Shutdown()
+
+	require.NoError(t, vm.ConsoleExpect("booster: finit(foo): open /usr/lib/modules/foo.ko: no such file or directory"))
+	require.NoError(t, vm.ConsoleExpect("booster: loading module xfs"))
+	require.NoError(t, vm.ConsoleExpect("Hello, booster!"))
+}