linux-kernel - Re: Question Regarding ERMS memcpy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170305095424.odptnh7vcesv442y@pd.tnic>
Date:   Sun, 5 Mar 2017 10:54:24 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     hpa@...or.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Question Regarding ERMS memcpy

On Sat, Mar 04, 2017 at 09:58:14PM -0700, Logan Gunthorpe wrote:
> So, I've found that my kernel config had the OPTIMIZE_FOR_SIZE selected
> instead of OPTIMIZE_FOR_PERFORMANCE. I'm not sure why that is but
> switching to the latter option fixes my problem. A memcpy call is used
> instead of the poor inline solution. (I'm not really sure how the inline
> solution even makes any sense as it almost certainly makes things larger
> in the grand scheme of things.)

Probably some gcc heuristics don't work as expected...

In any case, I have

# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set

here and it still generates REP; MOVSL in dmi_scan_machine().

-- 
Regards/Gruss,
    Boris.

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