linux-kernel - Re: [PATCH v2 1/8] bootconfig: Set CONFIG_BOOT

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Message-ID: <20200227100538.58127eeb@gandalf.local.home>
Date:   Thu, 27 Feb 2020 10:05:38 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 1/8] bootconfig: Set CONFIG_BOOT_CONFIG=n by default

On Thu, 27 Feb 2020 15:47:45 +0100
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Steven,
> 
> On Thu, Feb 27, 2020 at 3:27 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> > On Thu, 27 Feb 2020 10:22:00 +0100
> > Geert Uytterhoeven <geert@...ux-m68k.org> wrote:  
> > > > +static int __init warn_bootconfig(char *str)
> > > > +{
> > > > +       pr_warn("WARNING: 'bootconfig' found on the kernel command line but CONFIG_BOOTCONFIG is not set.\n");
> > > > +       return 0;
> > > > +}
> > > > +early_param("bootconfig", warn_bootconfig);  
> > >
> > > Yeah, let's increases kernel size for the people who don't want to jump
> > > on the bootconfig wagon :-(
> > >
> > > Is this really needed?  
> >
> > Yes, because if someone adds bootconfig to the command line they would be
> > expecting their bootconfig to be read. If not, we should not fail silently.  
> 
> If someone adds "ip=on" to the command line, they expect DHCP to work.
> Woops, you need CONFIG_IP_PNP for that.
> If someone adds "nfsroot=..." to the command line, they expect the NFS
> root fielsystem to be mounted.
> Guess how many options need to be enabled for that?

This isn't the same. It's more like having "ip=on" and ip configured, but
nothing happening because the command line isn't being read.

> 
> Perhaps we need CONFIG_COMMAND_NOT_FOUND?
> 
>     Kernel panic - not syncing: option "inspecial" not found.
>     Did you mean:
> 
>         option "imspecial" from section "mine"
>         option "urspecial" from section "yours"
> 
>     Try enabling it with "make xconfig".
> 
> > Are you really concerned about a tiny __init function that gets freed after
> > boot up?  
> 
> It's still part of the initial kernel image, and thus subject to boot loader and
> platform limitations.

And still in the noise of other aspects of the kernel. For little instances
like this, there should be a CONFIG_TINY (I thought we had that?),
otherwise it's going to be annoying. (Remember, I was fighting for not
having a config option at all to disable CONFIG_BOOTCONFIG).

-- Steve