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

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Message-Id: <20210806224941.6e28a3f8854f595f171b717d@kernel.org>
Date:   Fri, 6 Aug 2021 22:49:41 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Andrew Halaney <ahalaney@...hat.com>
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

Hi Andrew,

On Thu, 5 Aug 2021 10:22:21 -0500
Andrew Halaney <ahalaney@...hat.com> wrote:

> 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).

But if there are other parameters which also depends on kconfig?
This actually depends on CONFIG_BOOT_CONFIG=y. I guess there are
other parameters which are also depends on kconfig.
(and usually, developers doesn't change their grub.conf when he install
 a new kernel)

> 
> 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.

Actually, if CONFIG_BOOT_CONFIG=y, "bootconfig" is handled before preparing
cmdline strings, because it will copy (append) additional cmdline args
from the bootconfig to the cmdline.
I can remove the "bootconfig" string too. But I think it is better to keep
it in the cmdline so that users can ensure what he passed to the kernel.

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>