linux-kernel - Re: [PATCH] lkdtm: Prevent the compiler from optimising lkdtm_CORRUPT

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Message-ID: <20161115182704.GA29239@kroah.com>
Date:   Tue, 15 Nov 2016 19:27:04 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH] lkdtm: Prevent the compiler from optimising
 lkdtm_CORRUPT_STACK()

On Tue, Nov 15, 2016 at 09:27:47AM -0800, Kees Cook wrote:
> On Mon, Nov 14, 2016 at 11:02 PM, Michael Ellerman <mpe@...erman.id.au> wrote:
> > At least on powerpc with GCC 6, the compiler is smart enough to optimise
> > lkdtm_CORRUPT_STACK() into an empty function that just returns.
> 
> Sneaky. Thanks!
> 
> > If we print the buffer after we've written to it that prevents the
> > compiler from optimising away data and the memset().
> >
> > Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> 
> Acked-by: Kees Cook <keescook@...omium.org>
> 
> Greg, can you add this to the drivers/misc?

Now added, thanks.

greg k-h