factory: do not mount /lib/{modules,firmware} if there is a drivers tree

Do not mount /lib/{modules,firmware} in case snapd created a drivers
tree for our kernel snap, as in that case these mounts will be created
by snapd-generator from the base or from the snapd deb package for
hybrid systems. This situation is expected to happen only for 24+
systems.

factory/usr/lib/core/extra-paths

@@ -2,8 +2,21 @@
 
 set -eu
 
-cat <<EOF >>/sysroot/etc/fstab
+cat <<'EOF' >>/sysroot/etc/fstab
 /run/mnt/data /writable none bind,x-initrd.mount 0 0
+EOF
+
+# Find out kernel name / revision
+kernelPath=$(cat /sys/dev/block/"$(mountpoint --fs-devno /run/mnt/kernel)"/loop/backing_file)
+kernelFile=$(basename "$kernelPath")
+kernelName=${kernelFile%%_*}
+rev=${kernelFile#*_}
+rev=${rev%%.*}
+
+# Mount /lib/{firmware,modules} only if there is no drivers tree created by snapd
+if [ ! -d /run/mnt/data/system-data/var/lib/snapd/kernel/"$kernelName"/"$rev" ]; then
+    cat <<'EOF' >>/sysroot/etc/fstab
 /run/mnt/kernel/firmware /usr/lib/firmware none bind,x-initrd.mount 0 0
 /run/mnt/kernel/modules /usr/lib/modules none bind,x-initrd.mount 0 0
 EOF
+fi

factory/usr/lib/systemd/system-generators/kernel-snap-generator

@@ -35,6 +35,18 @@ if ! grep -q "^ID=ubuntu$" "${OS_RELEASE}"; then
     exit 0
 fi
 
+# Find out kernel name / revision
+kernelPath=$(cat /sys/dev/block/"$(mountpoint --fs-devno "$KERNEL_MNT_POINT")"/loop/backing_file)
+kernelFile=$(basename "$kernelPath")
+kernelName=${kernelFile%%_*}
+rev=${kernelFile#*_}
+rev=${rev%%.*}
+
+# Mount /lib/{firmware,modules} only if there is no drivers tree created by snapd
+if [ -d /run/mnt/data/var/lib/snapd/kernel/"$kernelName"/"$rev" ]; then
+    exit 0
+fi
+
 for entry in firmware modules; do
     what="${KERNEL_MNT_POINT}/${entry}"
     where="${sysroot}/usr/lib/${entry}"