rootfs-postcommands.bbclass: ensure that rootfs gets mounted ro

When read-only-rootfs is active, we need to ensure that the rootfs
does not get mounted read/write by the kernel or initramfs. Adding
"ro" to the boot parameters achieves that.

(From OE-Core rev: 2b9a670fabf3aefa93dc12be8b2fd3d6226be12a)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
(cherry picked from commit cfc09de06ecc12bb42181004689e881c75072665)
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/meta/classes/rootfs-postcommands.bbclass b/meta/classes/rootfs-postcommands.bbclass
index 5391e7a8e3..a4e627fef8 100644
--- a/meta/classes/rootfs-postcommands.bbclass
+++ b/meta/classes/rootfs-postcommands.bbclass
@@ -14,6 +14,14 @@ ROOTFS_POSTPROCESS_COMMAND += "rootfs_update_timestamp ; "
 # Tweak the mount options for rootfs in /etc/fstab if read-only-rootfs is enabled
 ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs", "read_only_rootfs_hook; ", "",d)}'
 
+# We also need to do the same for the kernel boot parameters,
+# otherwise kernel or initramfs end up mounting the rootfs read/write
+# (the default) if supported by the underlying storage.
+#
+# We do this with _append because the default value might get set later with ?=
+# and we don't want to disable such a default that by setting a value here.
+APPEND_append = '${@bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs", " ro", "", d)}'
+
 # Generates test data file with data store variables expanded in json format
 ROOTFS_POSTPROCESS_COMMAND += "write_image_test_data ; "