linux-kernel - Re: [PATCH] init: Suppress wrong warning for bootconfig cmdline parameter

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Message-ID: <20210805152221.33ssjh6qvgbj2pt5@halaneylaptop>
Date:   Thu, 5 Aug 2021 10:22:21 -0500
From:   Andrew Halaney <ahalaney@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] init: Suppress wrong warning for bootconfig cmdline
 parameter

On Thu, Aug 05, 2021 at 11:10:51AM +0900, Masami Hiramatsu wrote:
> Since the 'bootconfig' command line parameter is handled before
> parsing the command line, it doesn't use early_param(). But in
> this case, kernel shows a wrong warning message about it.
> 
> [    0.013714] Kernel command line: ro console=ttyS0  bootconfig console=tty0
> [    0.013741] Unknown command line parameters: bootconfig
> 
> To suppress this message, add a dummy handler for 'bootconfig'.
> 
> Fixes: 86d1919a4fb0 ("init: print out unknown kernel parameters")
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  init/main.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/init/main.c b/init/main.c
> index f5b8246e8aa1..8d97aba78c3a 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -397,6 +397,12 @@ static int __init bootconfig_params(char *param, char *val,
>  	return 0;
>  }
>  
> +static int __init warn_bootconfig(char *str)
> +{
> +	/* The 'bootconfig' has been handled by bootconfig_params(). */
> +	return 0;
> +}
> +
>  static void __init setup_boot_config(void)
>  {
>  	static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
> @@ -475,9 +481,8 @@ static int __init warn_bootconfig(char *str)
>  	pr_warn("WARNING: 'bootconfig' found on the kernel command line but CONFIG_BOOT_CONFIG is not set.\n");
>  	return 0;
>  }
> -early_param("bootconfig", warn_bootconfig);
> -
>  #endif
> +early_param("bootconfig", warn_bootconfig);
>  
>  /* Change NUL term back to "=", to make "param" the whole string. */
>  static void __init repair_env_string(char *param, char *val)
> 

Reviewed-by: Andrew Halaney <ahalaney@...hat.com>

Thanks Masami, this is one of the corner case command line parameters
that I was trying to highlight when I made the original commit (but I
didn't catch this one).

I _think_ the only other one is dyndbg based on some grepping. I'm
debating if it makes sense to do something similar there or to actually
use a callback to do some of the work it needs in stealing from the CLI.

For this case though I don't see how you could do anything other than
what you've done here -- you can't modify the params once we've started
processing, and that's what bootconfig needs to do.

Thanks,
Andrew