linux-kernel - Re: [PATCH] x86: Don't allow stackprotector without TSC

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Message-ID: <20141024120323.GA30459@pd.tnic>
Date:	Fri, 24 Oct 2014 14:03:23 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Ben Harris <bjh21@...21.me.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Don't allow stackprotector without TSC

On Thu, Oct 23, 2014 at 04:43:03PM -0700, Andy Lutomirski wrote:
> Presumably the actual failure is a #GP when trying to do the rdtsc. If
> so, wouldn't a better fix be to make that rdtsc check cpuid first? Can
> we easily check cpuid that early?

I don't see why not.

The real question, though is, can we have a fallback for RDTSC on those
machines so that they don't have to disable stack protector in order to
boot.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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