linux-kernel - Re: [PATCH] x86/setup: Add boot messages about cmdline builtins

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Date:   Fri, 24 Apr 2020 17:20:24 -0400
From:   Tony Fischetti <tony.fischetti@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, dyoung@...hat.com, dave.hansen@...ux.intel.com,
        linux@...ck-us.net, Kees Cook <keescook@...omium.org>,
        dan.j.williams@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/setup: Add boot messages about cmdline builtins

I like the idea of printing the original one, printing the information
about the cmdline manipulation, and, then, printing the final one at the
end, too.

The only problem is I don't know what to label the first printk so that it
remains clear that it's not necessarily the _final_ one, yet.

In either case, they should probably be changed to `pr_info`s, right?


On Wed, Apr 22, 2020 at 3:11 AM Baoquan He <bhe@...hat.com> wrote:
>
> On 04/22/20 at 12:20am, Tony Fischetti wrote:
> > While the ability to override or append to the boot command line has
> > been added, the boot messages contain no information as to whether the
> > cmdline was manipulated by the build-time options. This patch, for x86,
> > adds boot messages specifying whether the cmdline was manipulated and
> > waits for the potential changes to take place before printing the final
> > boot command line.
> >
> > Signed-off-by: Tony Fischetti <tony.fischetti@...il.com>
> > ---
> >  arch/x86/kernel/setup.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > index 4b3fa6cd3106..28d77f01fd0d 100644
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -828,7 +828,6 @@ void __init setup_arch(char **cmdline_p)
> >        */
> >       __flush_tlb_all();
> >  #else
> > -     printk(KERN_INFO "Command line: %s\n", boot_command_line);
> >       boot_cpu_data.x86_phys_bits = MAX_PHYSMEM_BITS;
> >  #endif
> >
> > @@ -904,10 +903,12 @@ void __init setup_arch(char **cmdline_p)
> >
> >  #ifdef CONFIG_CMDLINE_BOOL
> >  #ifdef CONFIG_CMDLINE_OVERRIDE
> > +     pr_info("Overriding command line with builtin\n");
> >       strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
> >  #else
> >       if (builtin_cmdline[0]) {
> >               /* append boot loader cmdline to builtin */
> > +             pr_info("Appending command line to builtin\n");
> >               strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
> >               strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
> >               strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
> > @@ -916,6 +917,7 @@ void __init setup_arch(char **cmdline_p)
> >  #endif
> >
> >       strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
> > +     pr_info("Command line: %s\n", command_line);
>
> Yeah, adding info to tell there's action on overriding or apending
> command line looks good to me. Maybe keep the printing of the original
> command, we can get the final command line from '/proc/cmdline' after
> system boot, or just get it from the original cmdline + CONFIG_CMDLINE.
> Or print the original cmdline and the final cmdline both.
>
> Personal opinion.
>
> >       *cmdline_p = command_line;
> >
> >       /*
> > --
> > 2.20.1
> >
>


-- 
--
Tony Fischetti
tony.fischetti@...il.com
(718) 431-4597