linux-kernel - Re: [PATCH printk v1 01/18] kdb: do not assume write() callback available

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Date:   Tue, 7 Mar 2023 08:34:08 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Aaron Tomlin <atomlin@...hat.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net
Subject: Re: [PATCH printk v1 01/18] kdb: do not assume write() callback available

Hi,

On Thu, Mar 2, 2023 at 11:57 AM John Ogness <john.ogness@...utronix.de> wrote:
>
> It is allowed for consoles to provide no write() callback. For
> example ttynull does this.
>
> Check if a write() callback is available before using it.
>
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> ---
>  kernel/debug/kdb/kdb_io.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 5c7e9ba7cd6b..e9139dfc1f0a 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -576,6 +576,8 @@ static void kdb_msg_write(const char *msg, int msg_len)
>                         continue;
>                 if (c == dbg_io_ops->cons)
>                         continue;
> +               if (!c->write)
> +                       continue;

Reviewed-by: Douglas Anderson <dianders@...omium.org>