linux-kernel - Re: [PATCH bootconfig 2/3] fs/proc: Add boot loader arguments as comment to /proc/bootconfig

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Message-Id: <20231006175948.14df07948d8c6a4a46473c13@kernel.org>
Date:   Fri, 6 Oct 2023 17:59:48 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Arnd Bergmann <arnd@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH bootconfig 2/3] fs/proc: Add boot loader arguments as
 comment to /proc/bootconfig

On Thu,  5 Oct 2023 10:17:46 -0700
"Paul E. McKenney" <paulmck@...nel.org> 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.
> It is also useful when booting the next kernel via kexec(), in which
> case it is necessary to supply only those kernel command-line arguments
> from the boot loader, and most definitely not those that were embedded
> into the current kernel.
> 
> Therefore, add comments to /proc/bootconfig of the form:
> 
> 	# Parameters from bootloader:
> 	# root=UUID=ac0f0548-a69d-43ca-a06b-7db01bcbd5ad ro quiet ...
> 
> The second added line shows only those kernel boot parameters supplied
> by the boot loader.

Thanks for update it.

This looks good to me.

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

Thank you!

> 
> Link: https://lore.kernel.org/all/CAHk-=wjpVAW3iRq_bfKnVfs0ZtASh_aT67bQBG11b4W6niYVUw@mail.gmail.com/
> Link: https://lore.kernel.org/all/20230731233130.424913-1-paulmck@kernel.org/
> Co-developed-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> Cc: Arnd Bergmann <arnd@...nel.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Alexey Dobriyan <adobriyan@...il.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: <linux-trace-kernel@...r.kernel.org>
> Cc: <linux-fsdevel@...r.kernel.org>
> ---
>  fs/proc/bootconfig.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/proc/bootconfig.c b/fs/proc/bootconfig.c
> index 2e244ada1f97..902b326e1e56 100644
> --- a/fs/proc/bootconfig.c
> +++ b/fs/proc/bootconfig.c
> @@ -62,6 +62,12 @@ static int __init copy_xbc_key_value_list(char *dst, size_t size)
>  				break;
>  			dst += ret;
>  		}
> +		if (ret >= 0 && boot_command_line[0]) {
> +			ret = snprintf(dst, rest(dst, end), "# Parameters from bootloader:\n# %s\n",
> +				       boot_command_line);
> +			if (ret > 0)
> +				dst += ret;
> +		}
>  	}
>  out:
>  	kfree(key);
> -- 
> 2.40.1
> 


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