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Date:   Fri, 4 Aug 2023 20:23:20 +0300
From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     "Paul E. McKenney" <paulmck@kernel.org>
Cc:     akpm@linux-foundation.org, mhiramat@kernel.org, arnd@kernel.org,
        ndesaulniers@google.com, sfr@canb.auug.org.au,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@meta.com
Subject: Re: [PATCH RFC bootconfig] 1/2] fs/proc: Add /proc/cmdline_load for
 boot loader arguments
Message-ID: <db2617d2-589d-47c1-a0cc-e8aeca58710a@p183>
References: <197cba95-3989-4d2f-a9f1-8b192ad08c49@paulmck-laptop>
 <20230728033701.817094-1-paulmck@kernel.org>
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On Thu, Jul 27, 2023 at 08:37:00PM -0700, Paul E. McKenney wrote:
> In kernels built with CONFIG_BOOT_CONFIG_FORCE=y, /proc/cmdline will
> show all kernel boot parameters, both those supplied by the boot loader
> and those embedded in the kernel image.  This works well for those who
> just want to see all of the kernel boot parameters, but is not helpful to
> those who need to see only those parameters supplied by the boot loader.
> This is especially important when these parameters are presented to the
> boot loader by automation that might gather them from diverse sources.
> 
> Therefore, provide a /proc/cmdline_load file that shows only those kernel
> boot parameters supplied by the boot loader.

> +static int cmdline_load_proc_show(struct seq_file *m, void *v)
> +{
> +	seq_puts(m, boot_command_line);
> +	seq_putc(m, '\n');
> +	return 0;
> +}
> +
>  static int __init proc_cmdline_init(void)
>  {
>  	struct proc_dir_entry *pde;
> @@ -19,6 +27,11 @@ static int __init proc_cmdline_init(void)
>  	pde = proc_create_single("cmdline", 0, NULL, cmdline_proc_show);
>  	pde_make_permanent(pde);
>  	pde->size = saved_command_line_len + 1;
> +	if (IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE)) {
> +		pde = proc_create_single("cmdline_load", 0, NULL, cmdline_load_proc_show);
> +		pde_make_permanent(pde);
> +		pde->size = strnlen(boot_command_line, COMMAND_LINE_SIZE) + 1;
> +	}

Please add it as separate fs/proc/cmdline_load.c file so that name of
the file matches name of the /proc file.

The name "cmdline_load" is kind of non-descriptive. Mentioning "bootloader"
somewhere should improve things.