linux-kernel - Re: [PATCH] x86/ucode: replace redundant string literals

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Message-ID: <20151222170714.GD3961@pd.tnic>
Date:	Tue, 22 Dec 2015 18:07:14 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/ucode: replace redundant string literals

On Tue, Dec 22, 2015 at 08:40:43AM -0700, Jan Beulich wrote:
> This doesn't just eliminate needless redundancy
> (plus avoid a possible disconnect if one string instance gets changed
> without the other(s)),

This argument is bogus. We will never ever change a user-visible command
line option. Ever.

> but also eliminates a warning some gcc versions emit ("array access
> beyond array bounds", observed with 4.3.4) in the 32-bit case.

Now that I'm interested in - how exactly do you trigger this? gcc
version, etc?

> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> ---
>  arch/x86/kernel/cpu/microcode/core.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> --- 4.4-rc6/arch/x86/kernel/cpu/microcode/core.c
> +++ 4.4-rc6-x86-ucode-early-string/arch/x86/kernel/cpu/microcode/core.c
> @@ -83,13 +83,11 @@ static bool __init check_loader_disabled
>  {
>  #ifdef CONFIG_X86_32
>  	const char *cmdline = (const char *)__pa_nodebug(boot_command_line);
> -	const char *opt	    = "dis_ucode_ldr";
> -	const char *option  = (const char *)__pa_nodebug(opt);
> +	const char *option  = (const char *)__pa_nodebug(__setup_str_disable_loader);
>  	bool *res = (bool *)__pa_nodebug(&dis_ucode_ldr);
> -
>  #else /* CONFIG_X86_64 */
>  	const char *cmdline = boot_command_line;
> -	const char *option  = "dis_ucode_ldr";
> +	const char *option  = __setup_str_disable_loader;
>  	bool *res = &dis_ucode_ldr;
>  #endif

I don't like it: it is not clear at a glance that this __setup_str*
magic gets generated from the __setup macro. In addition, this code is
as unreadable as it is now - your patch makes it even more cryptic.

I much prefer the redundancy.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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