linux-kernel - Re: [kernel-hardening] Re: [PATCH 4/4] refcount: Report failures through CHECK_DATA

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Message-ID: <20170207150737.GM25813@worktop.programming.kicks-ass.net>
Date:   Tue, 7 Feb 2017 16:07:37 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Will Deacon <will.deacon@....com>,
        David Windsor <dwindsor@...il.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Howells <dhowells@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [kernel-hardening] Re: [PATCH 4/4] refcount: Report failures
 through CHECK_DATA_CORRUPTION

On Tue, Feb 07, 2017 at 01:50:20PM +0000, Mark Rutland wrote:
> > Right something along those lines. (a) will need GCC help, and (b) would
> > be kernel-arch specific. So this isn't something we can quickly do.
> 
> I agree this isn't something that can be hacked together quickly, and
> certainly shouldn't block these patches.
> 
> However, I don't think we need anything new from GCC, and I think we
> already have a generic API for (b).
> 
> For (a) we don't need new GCC help if we do something like we did in
> commit 72c5839515260dce to do the mangling. Prepend a prefix to the
> register, e.g. changing 'x0' to '__pt_regs_offset_x0', which we arrange
> to hold the correct value.

I'm not sure I can decipher that commit and therefore have no idea if
something similar can be done for other architectures.