linux-kernel - Re: [PATCH v2] x86/mce: work around an erratum on fast string copy instructions.

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Message-ID: <YhAkk9/gH2ZKsRZk@zn.tnic>
Date:   Fri, 18 Feb 2022 23:58:27 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Jue Wang <juew@...gle.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v2] x86/mce: work around an erratum on fast string copy
 instructions.

On Fri, Feb 18, 2022 at 10:38:10PM +0000, Luck, Tony wrote:
> > If so, we can sandwich around it with nstrumentation_begin() and _end()...
> 
> I guess so ... this stuff is all Greek to me.

roughly speaking... noinstr simply puts code in a special section
.noinstr.text and objtool checks whether that code calls code outside of
it. And noinstr is off-limits for tracing code.

The begin/end things are for ranges of code and work in a similar way,
see include/linux/instrumentation.h

-- 
Regards/Gruss,
    Boris.

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