linux-kernel - Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init

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Date:	Mon, 18 Jan 2016 19:14:57 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Brian Gerst <brgerst@...il.com>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after
 init

On Mon, Jan 18, 2016 at 11:52:34AM -0500, Brian Gerst wrote:
> It is due to page alignment padding.  It was not enough to lose a
> whole page from .text in your case.

So nothing more got freed.

> The size command includes any section that is marked executable in the
> text count, including init text.  If you use readelf -S vmlinux.o
> instead you will notice that .text is the same size or smaller, and
> .static_cpu_has (which is freed after boot) is the difference.

So we're talking about less than a page here?

  [19] .static_cpu_has   PROGBITS         ffffffff81d335d3  011335d3
       00000000000002df  0000000000000000  AX       0     0     1

That's 479 bytes. Meh, it doesn't look like it is worth the trouble.

Maybe I should build an allyesconfig.

-- 
Regards/Gruss,
    Boris.

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