Re: [PATCH] sysvinit-inittab: support non-busybox-getty on serial consoles

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Fri, 2019-02-08 at 12:02 +0000, André Draszik wrote:
> From: André Draszik <andre.draszik@jci.com>
> 
> Busybox' getty has code to try to make itself a session leader,
> whereas util-linux' agetty doesn't. It expects this to happen
> from outside.
> When getty is not a session leader, many things don't work on
> the serial console, e.g. setting the terminal process group,
> job control doesn't work, etc.
> 
> Executing image tests also fails with AssertionErrors, because
>     Feb  5 16:12:55 qemuarm getty[590]: /dev/ttyAMA1: cannot get
> controlling tty: Operation not permitted
>     Feb  5 16:12:55 qemuarm getty[590]: /dev/ttyAMA1: cannot set
> process group: Inappropriate ioctl for device
> 
> Update the start_getty script to invoke getty via the setsid
> utility if needed, i.e. if /sbin/getty is not busybox getty.
> 
> [YOCTO #13058]
> 
> Signed-off-by: André Draszik <andre.draszik@jci.com>
> ---
>  meta/recipes-core/sysvinit/sysvinit-inittab/start_getty | 9
> ++++++++-
>  meta/recipes-core/sysvinit/sysvinit-inittab_2.88dsf.bb  | 1 +
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/meta/recipes-core/sysvinit/sysvinit-inittab/start_getty
> b/meta/recipes-core/sysvinit/sysvinit-inittab/start_getty
> index e15ae35f90..ae613f1e54 100644
> --- a/meta/recipes-core/sysvinit/sysvinit-inittab/start_getty
> +++ b/meta/recipes-core/sysvinit/sysvinit-inittab/start_getty
> @@ -13,6 +13,13 @@ active_serial=$(grep "serial" /proc/tty/drivers |
> cut -d/ -f1 | sed "s/ *$//")
>  # Rephrase input parameter from ttyS target index (ttyS1, ttyS2,
> ttyAMA0, etc).
>  runtime_tty=$(echo $2 | grep -oh '[0-9]')
>  
> +# busybox' getty does this itself, util-linux' getty needs extra
> help
> +getty="/sbin/getty"
> +if ! basename $(readlink -f "${getty}") | grep -q busybox \
> +    && [ -x "/usr/bin/setsid" ] ; then
> +    getty="/usr/bin/setsid ${getty}"
> +fi

The reason I'm reluctant to take changes like this is you just added 3
fork calls above. This does have a significant effect on boot time on
slower devices.

Is there a way we can do a shell string comparison rather than using
grep? case statement maybe?

Cheers,

Richard