diff --git a/scripts/tags.sh b/scripts/tags.sh
index d23dcbf17457..086341e10aa8 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -37,6 +37,13 @@ find_all_archs()
 	done
 }
 
+# gtags(1) refuses to index any file outside of its current working dir.
+# If gtags indexing is requested and the build output directory is not
+# the kernel source tree, index all files in absolute-path form.
+if [[ "$1" == "gtags" && -n "${tree}" ]]; then
+	tree=$(realpath "$tree")/
+fi
+
 # Detect if ALLSOURCE_ARCHS is set. If not, we assume SRCARCH
 if [ "${ALLSOURCE_ARCHS}" = "" ]; then
 	ALLSOURCE_ARCHS=${SRCARCH}
@@ -145,7 +152,7 @@ docscope()
 
 dogtags()
 {
-	all_target_sources | gtags -i -f -
+	all_target_sources | gtags -i -C "${tree:-.}" -f - "$PWD"
 }
 
 # Basic regular expressions with an optional /kind-spec/ for ctags and