internal/uevent: optionally pass UUID during coldboot

This enables rejection of non-coldboot synthetic events.

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

internal/uevent/coldboot.go

@@ -7,6 +7,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"slices"
 )
 
 // synthAdd is prepared bytes written to uevent to cause a synthetic add event
@@ -26,6 +27,7 @@ var synthAdd = []byte(KOBJ_ADD.String())
 func Coldboot(
 	ctx context.Context,
 	pathname string,
+	uuid *UUID,
 	visited chan<- string,
 	handleWalkErr func(error) error,
 ) error {
@@ -39,6 +41,11 @@ func Coldboot(
 		}
 	}
 
+	add := synthAdd
+	if uuid != nil {
+		add = slices.Concat(add, []byte{' '}, []byte(uuid.String()))
+	}
+
 	return filepath.WalkDir(filepath.Join(pathname, "devices"), func(
 		path string,
 		d fs.DirEntry,
@@ -54,7 +61,7 @@ func Coldboot(
 		if d.IsDir() || d.Name() != "uevent" {
 			return nil
 		}
-		if err = os.WriteFile(path, synthAdd, 0); err != nil {
+		if err = os.WriteFile(path, add, 0); err != nil {
 			return handleWalkErr(err)
 		}