linux-kernel - Re: [PATCH v7 2/5] x86: Add cmdline

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Date:   Wed, 9 Nov 2022 23:54:06 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Evgeniy Baskov <baskov@...ras.ru>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: Re: [PATCH v7 2/5] x86: Add cmdline_prepare() helper

On Tue, Oct 04, 2022 at 03:48:21PM +0300, Evgeniy Baskov wrote:
> +static inline void cmdline_prepare(char *command_line,
> +				   const char *boot_command_line)
> +{
> +	if (!IS_ENABLED(CONFIG_CMDLINE_BOOL)) {
> +		strscpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
> +	} else if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
> +		/* Append boot loader cmdline to builtin one. */
> +		strlcat(command_line, " ", COMMAND_LINE_SIZE);
> +		strlcat(command_line, boot_command_line, COMMAND_LINE_SIZE);
> +	}

Why can't we make this plain and simple and understandable at a quick
glance instead of putting parts of the string in some variable and then
still doing copying outside of the function?

IOW, simply put everything in a single function:

static inline void cmdline_prepare(char *dst,
                                   const char *builtin_cmdline,
                                   const char *boot_command_line)
{                                  
        /* Depends on CONFIG_CMDLINE_BOOL, overwrite with builtin cmdline */
        if (IS_ENABLED(CONFIG_CMDLINE_OVERRIDE))
                strscpy(dst, builtin_cmdline, COMMAND_LINE_SIZE);
        else if (IS_ENABLED(CONFIG_CMDLINE_BOOL)) {
                if (builtin_cmdline[0]) {
                        /* append boot loader cmdline to builtin */
                        srtlcat(dst, builtin_cmdline, COMMAND_LINE_SIZE)
                        strlcat(dst, " ", COMMAND_LINE_SIZE);
                        strlcat(dst, boot_command_line, COMMAND_LINE_SIZE);
                } else {
                        strscpy(dst, boot_command_line, COMMAND_LINE_SIZE);
                }
        }
}

which is then called like this:

	cmdline_prepare(command_line, builtin_cmdline, boot_command_line);

and when it returns command_line is ready. And before it, command_line
is the empty string:

static char __initdata command_line[COMMAND_LINE_SIZE];

And all the complexity is in one single function and that single
function does each case in an obvious manner and you don't have to go
look outside of the function body to understand what it does.

Hmmm?

-- 
Regards/Gruss,
    Boris.

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