runqemu: support rootfs mounted ro

Optionally allow to set QB_KERNEL_ROOT to e.g. "/dev/vda ro" to mount the
rootfs reay-only in Qemu.

(From OE-Core rev: 448eb1fd21287ba16b17e9402ce040b86ae3638c)

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 9 insertions, 1 deletions

diff --git a/meta/classes/qemuboot.bbclass b/meta/classes/qemuboot.bbclass
index bf529e9aa4..8cdb544a94 100644
--- a/meta/classes/qemuboot.bbclass
+++ b/meta/classes/qemuboot.bbclass
@@ -36,6 +36,8 @@
 #         in system mode, where system is experiencing entropy starvation
 #
 # QB_KERNEL_ROOT: kernel's root, e.g., /dev/vda
+#                 By default "/dev/vda rw" gets passed to the kernel.
+#                 To mount the rootfs read-only QB_KERNEL_ROOT can be set to e.g. "/dev/vda ro".
 #
 # QB_NETWORK_DEVICE: network device, e.g., "-device virtio-net-pci,netdev=net0,mac=@MAC@",
 #                    it needs work with QB_TAP_OPT and QB_SLIRP_OPT.
diff --git a/scripts/runqemu b/scripts/runqemu
index d4f0888f8d..efb98ab9e0 100755
--- a/scripts/runqemu
+++ b/scripts/runqemu
@@ -1266,7 +1266,13 @@ class BaseConfig(object):
                 self.rootfs_options = vm_drive
                 if not self.fstype in self.vmtypes:
                     self.rootfs_options += ' -no-reboot'
-            self.kernel_cmdline = 'root=%s rw' % (self.get('QB_KERNEL_ROOT'))
+
+            # By default, ' rw' is appended to QB_KERNEL_ROOT unless either ro or rw is explicitly passed.
+            qb_kernel_root = self.get('QB_KERNEL_ROOT')
+            qb_kernel_root_l = qb_kernel_root.split()
+            if not ('ro' in qb_kernel_root_l or 'rw' in qb_kernel_root_l):
+                qb_kernel_root += ' rw'
+            self.kernel_cmdline = 'root=%s' % qb_kernel_root
 
         if self.fstype == 'nfs':
             self.rootfs_options = ''