proc: dont trigger mount error with invalid options on old kernels
As of commit 4e39995371738b04d98d27b0d34ea8fe09ec9fab ("core: introduce
ProtectProc= and ProcSubset= to expose hidepid= and subset= procfs
mount options") kernels older than v5.8 generate multple warnings at
boot, as seen in this Yocto build from today:
qemux86-64 login: root
[ 65.829009] proc: Bad value for 'hidepid'
root@qemux86-64:~# dmesg|grep proc:
[ 16.990706] proc: Bad value for 'hidepid'
[ 28.060178] proc: Bad value for 'hidepid'
[ 28.874229] proc: Bad value for 'hidepid'
[ 32.685107] proc: Bad value for 'hidepid'
[ 65.829009] proc: Bad value for 'hidepid'
root@qemux86-64:~#
We see reports of the issue as in general its hard to someone to tell
the difference between an error in dmesg which they should worry about and
one that is harmless. This adds support burden to developers so Yocto
Project has added this patch.
The commit that triggers this is systemd v247-rc1~378^2~3 -- so any
systemd 247 and above plus kernel v5.7 or older will need this.
As noted in https://github.com/systemd/systemd/issues/16896
it is possible changes could be backported to different kernel versions
so the test isn't 100% foolproof but does give better results than a
continual stream of bug reports.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>