linux-kernel - Re: [PATCH RFC bootconfig] Allow forcing unconditional bootconfig processing

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Message-Id: <20230227081632.da70c54f3eede048549fb7af@kernel.org>
Date:   Mon, 27 Feb 2023 08:16:32 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     paulmck@...nel.org
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        corbet@....net, akpm@...ux-foundation.org, ndesaulniers@...gle.com,
        vbabka@...e.cz, hannes@...xchg.org, joel@...lfernandes.org,
        quic_neeraju@...cinc.com, urezki@...il.com
Subject: Re: [PATCH RFC bootconfig] Allow forcing unconditional bootconfig
 processing

On Fri, 24 Feb 2023 17:19:10 -0800
"Paul E. McKenney" <paulmck@...nel.org> wrote:

> On Sat, Feb 25, 2023 at 09:58:11AM +0900, Masami Hiramatsu wrote:
> > On Fri, 24 Feb 2023 08:33:07 -0800
> > "Paul E. McKenney" <paulmck@...nel.org> wrote:
> > 
> > > On Sat, Feb 25, 2023 at 01:13:06AM +0900, Masami Hiramatsu wrote:
> > > > Hi Geert,
> > > > 
> > > > On Fri, 24 Feb 2023 09:31:50 +0100
> > > > Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > 
> > > > > Hi Paul,
> > > > > 
> > > > > On Sat, Jan 7, 2023 at 5:33 PM Paul E. McKenney <paulmck@...nel.org> wrote:
> > > > > > On Sun, Jan 08, 2023 at 12:22:15AM +0900, Masami Hiramatsu wrote:
> > > > > > > BTW, maybe CONFIG_BOOT_CONFIG_EMBED is better to select this.
> > > > > > > (or at least recommend to enable this)
> > > > > >
> > > > > > Like this?
> > > > > >
> > > > > >                                                         Thanx, Paul
> > > > > >
> > > > > > ------------------------------------------------------------------------
> > > > > >
> > > > > > commit d09a1505c51a70da38b34ac38062977299aef742
> > > > > > Author: Paul E. McKenney <paulmck@...nel.org>
> > > > > > Date:   Sat Jan 7 08:09:22 2023 -0800
> > > > > >
> > > > > >     bootconfig: Default BOOT_CONFIG_FORCE to y if BOOT_CONFIG_EMBED
> > > > > >
> > > > > >     When a kernel is built with CONFIG_BOOT_CONFIG_EMBED=y, the intention
> > > > > >     will normally be to unconditionally provide the specified kernel-boot
> > > > > >     arguments to the kernel, as opposed to requiring a separately provided
> > > > > >     bootconfig parameter.  Therefore, make the BOOT_CONFIG_FORCE Kconfig
> > > > > >     option default to y in kernels built with CONFIG_BOOT_CONFIG_EMBED=y.
> > > > > >
> > > > > >     The old semantics may be obtained by manually overriding this default.
> > > > > >
> > > > > >     Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > > > >     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > > > > >
> > > > > > diff --git a/init/Kconfig b/init/Kconfig
> > > > > > index 0fb19fa0edba9..97a0f14d9020d 100644
> > > > > > --- a/init/Kconfig
> > > > > > +++ b/init/Kconfig
> > > > > > @@ -1379,6 +1379,7 @@ config BOOT_CONFIG
> > > > > >  config BOOT_CONFIG_FORCE
> > > > > >         bool "Force unconditional bootconfig processing"
> > > > > >         depends on BOOT_CONFIG
> > > > > > +       default y if BOOT_CONFIG_EMBED
> > > > > >         help
> > > > > >           With this Kconfig option set, BOOT_CONFIG processing is carried
> > > > > >           out even when the "bootconfig" kernel-boot parameter is omitted.
> > > > > 
> > > > > Thanks for your patch, which is now commit 6ded8a28ed80e4cc
> > > > > ("bootconfig: Default BOOT_CONFIG_FORCE to y if BOOT_CONFIG_EMBED").
> > > > > 
> > > > > After this change, an all{mod,yes}config kernel has:
> > > > > 
> > > > >     CONFIG_BOOT_CONFIG_FORCE=y
> > > > >     CONFIG_BOOT_CONFIG_EMBED=y
> > > > >     CONFIG_BOOT_CONFIG_EMBED_FILE=""
> > > > > 
> > > > > Will this actually work? I haven't tried booting such a kernel yet.
> > > > 
> > > > Yeah, good question. It is same as when you boot the kernel with 'bootconfig'
> > > > but do not add the bootconfig file to initrd. You may see below message
> > > > on boot log, but kernel boots normally. :)
> > > > 
> > > >  'bootconfig' found on command line, but no bootconfig found
> > > > 
> > > > (Maybe it is better to fix the message, because if BOOT_CONFIG_FORCE=y, this
> > > > will be shown without 'bootconfig' on command line.)
> > > 
> > > I just tried it again, and for me it just silently ignores the bootconfig
> > > setup.  Which is what I recall happening when I tried it when creating
> > > the patch.
> > > 
> > > Here is the .config file pieces of interest:
> > > 
> > > CONFIG_BOOT_CONFIG=y
> > > CONFIG_BOOT_CONFIG_FORCE=y
> > > CONFIG_BOOT_CONFIG_EMBED=y
> > > CONFIG_BOOT_CONFIG_EMBED_FILE=""
> > > 
> > > Anyone else seeing something different?
> > 
> > Hmm, from the code, I think you'll see that message in early console log.
> > 
> > In init/main.c:
> > 
> > ----
> > #ifdef CONFIG_BOOT_CONFIG
> > /* Is bootconfig on command line? */
> > static bool bootconfig_found = IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE);
> > static size_t initargs_offs;
> > #else
> > ----
> > And
> > ----
> > static void __init setup_boot_config(void)
> > {
> > ...
> >         strscpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
> >         err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
> >                          bootconfig_params);
> > 
> >         if (IS_ERR(err) || !bootconfig_found)
> >                 return;
> > 
> >         /* parse_args() stops at the next param of '--' and returns an address */
> >         if (err)
> >                 initargs_offs = err - tmp_cmdline;
> > 
> >         if (!data) {
> >                 pr_err("'bootconfig' found on command line, but no bootconfig found\n");
> >                 return;
> >         }
> > ----
> > 
> > Thus, if CONFIG_BOOT_CONFIG_FORCE=y, the process passes the below check
> > 
> >         if (IS_ERR(err) || !bootconfig_found)
> >                 return;
> > 
> > But since we have an empty 'data', the error should be printed.
> 
> And you are quite right, the runs without data files did get me this:
> 
> 'bootconfig' found on command line, but no bootconfig found
> 
> Please accept my apologies for my confusion.

No problem :), so should we skip this message if CONFIG_BOOT_CONFIG_FORCE=y,
because user may not pass 'bootconfig'?

Or, may be we can make it;

 "Skip bootconfig, because no bootconfig data found."

so that user can notice they forget to set up bootconfig data?

Thank you,


> 
> 							Thanx, Paul
> 
> > Thank you,
> > 
> > > 
> > > 							Thanx, Paul
> > > 
> > > > Thank you!
> > > > 
> > > > > 
> > > > > Gr{oetje,eeting}s,
> > > > > 
> > > > >                         Geert
> > > > > 
> > > > > -- 
> > > > > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> > > > > 
> > > > > In personal conversations with technical people, I call myself a hacker. But
> > > > > when I'm talking to journalists I just say "programmer" or something like that.
> > > > >                                 -- Linus Torvalds
> > > > 
> > > > 
> > > > -- 
> > > > Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > 
> > -- 
> > Masami Hiramatsu (Google) <mhiramat@...nel.org>


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>