linux-kernel - Re: [PATCH] x86: Parse CONFIG

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Date:   Wed, 4 May 2022 10:59:12 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Baskov Evgeniy <baskov@...ras.ru>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Parse CONFIG_CMDLINE in compressed kernel

On Thu, Apr 07, 2022 at 05:40:14AM +0300, Baskov Evgeniy wrote:
> CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE was ignored
> during options lookup in compressed kernel, including
> earlyprintk option, so it was impossible to get earlyprintk
> messages from that stage of boot process via command line
> provided at compile time. Being able to enable earlyprintk
> via compile-time option might be desirable for booting
> on systems with broken UEFI command line arguments via EFISTUB.
> 
> Parse CONFIG_CMDLINE-related options correctly in compressed
> kernel code.
> 
> Signed-off-by: Baskov Evgeniy <baskov@...ras.ru>
> 
> diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c
> index f1add5d85da9..dd8cbbe61dff 100644
> --- a/arch/x86/boot/compressed/cmdline.c
> +++ b/arch/x86/boot/compressed/cmdline.c
> @@ -22,9 +22,49 @@ unsigned long get_cmd_line_ptr(void)
>  }
>  int cmdline_find_option(const char *option, char *buffer, int bufsize)
>  {
> -	return __cmdline_find_option(get_cmd_line_ptr(), option, buffer, bufsize);
> +	int len = -1;
> +	unsigned long cmdline_ptr;
> +
> +	/*
> +	 * First try command line string provided by user,
> +	 * then try command line string configured at comple time.
> +	 * Skip first step if CONFIG_CMDLINE_OVERRIDE is enabled
> +	 * and parse only compile time command line.
> +	 */
> +
> +	if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
> +		cmdline_ptr = get_cmd_line_ptr();
> +		len = __cmdline_find_option(cmdline_ptr, option,
> +					    buffer, bufsize);
> +	}
> +
> +#ifdef CONFIG_CMDLINE_BOOL
> +	if (len < 0) {
> +		cmdline_ptr = (unsigned long)CONFIG_CMDLINE;
> +		len = __cmdline_find_option(cmdline_ptr, option,
> +					    buffer, bufsize);
> +	}
> +#endif

Do I see it correctly that all this logic boils down to returning the
proper cmdline ptr and so you can do that once in get_cmd_line_ptr()
instead of duplicating the ifdeffery?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette