linux-kernel - Re: [PATCH] printk: fix return value of printk.devkmsg _

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Message-ID: <87sfs17rsu.fsf@jogness.linutronix.de>
Date:   Tue, 01 Mar 2022 14:04:41 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Igor Zhbanov <i.zhbanov@...russia.ru>,
        Borislav Petkov <bp@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] printk: fix return value of printk.devkmsg __setup handler

On 2022-02-28, Randy Dunlap <rdunlap@...radead.org> wrote:
> If an invalid option value is used with "printk.devkmsg=<value>",
> it is silently ignored.
> If a valid option value is used, it is honored but the wrong return
> value (0) is used, indicating that the command line option had an
> error and was not handled. This string is not added to init's
> environment strings due to init/main.c::unknown_bootoption()
> checking for a '.' in the boot option string and then considering
> that string to be an "Unused module parameter".
>
> Print a warning message if a bad option string is used.
> Always return 1 from the __setup handler to indicate that the command
> line option has been handled.
>
> Fixes: 750afe7babd1 ("printk: add kernel parameter to control writes to /dev/kmsg")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: Igor Zhbanov <i.zhbanov@...russia.ru>

Reviewed-by: John Ogness <john.ogness@...utronix.de>

> Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@...russia.ru

The message at this link is very helpful in explaining the state of
declaring kernel parameters. Hopefully someday someone will document
and/or comment this stuff.

John Ogness