disk: add new GenImageKernelOptions helper

This creates the needed kernel options for an image, if any,
based on the partition table.

Co-Authored-By: Achilleas Koutsou <achilleas@koutsou.net>

internal/osbuild2/disk.go

@@ -63,3 +63,19 @@ func GenImagePrepareStages(pt *disk.PartitionTable, filename string) []*Stage {
 func GenImageFinishStages(pt *disk.PartitionTable, filename string) []*Stage {
 	return GenDeviceFinishStages(pt, filename)
 }
+
+func GenImageKernelOptions(pt *disk.PartitionTable) []string {
+	cmdline := make([]string, 0)
+
+	genOptions := func(e disk.Entity, path []disk.Entity) error {
+		switch ent := e.(type) {
+		case *disk.LUKSContainer:
+			karg := "luks.uuid=" + ent.UUID
+			cmdline = append(cmdline, karg)
+		}
+		return nil
+	}
+
+	_ = pt.ForEachEntity(genOptions)
+	return cmdline
+}

internal/osbuild2/disk_test.go

@@ -0,0 +1,40 @@
+package osbuild2
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/osbuild/osbuild-composer/internal/blueprint"
+	"github.com/osbuild/osbuild-composer/internal/disk"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGenImageKernelOptions(t *testing.T) {
+	assert := assert.New(t)
+
+	// math/rand is good enough in this case
+	/* #nosec G404 */
+	rng := rand.New(rand.NewSource(13))
+
+	luks_lvm := testPartitionTables["luks+lvm"]
+
+	pt, err := disk.NewPartitionTable(&luks_lvm, []blueprint.FilesystemCustomization{}, 0, rng)
+	assert.NoError(err)
+
+	var uuid string
+
+	findLuksUUID := func(e disk.Entity, path []disk.Entity) error {
+		switch ent := e.(type) {
+		case *disk.LUKSContainer:
+			uuid = ent.UUID
+		}
+
+		return nil
+	}
+	_ = pt.ForEachEntity(findLuksUUID)
+
+	assert.NotEmpty(uuid, "Could not find LUKS container")
+	cmdline := GenImageKernelOptions(pt)
+
+	assert.Subset(cmdline, []string{"luks.uuid=" + uuid})
+}