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Date: Thu, 21 May 2020 14:42:56 -0700
From: Kristen Carlson Accardi <kristen@...ux.intel.com>
To: Kees Cook <keescook@...omium.org>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, Jonathan Corbet
<corbet@....net>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
arjan@...ux.intel.com, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com, rick.p.edgecombe@...el.com, Tony Luck
<tony.luck@...el.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 7/9] x86: Add support for function granular KASLR
Hi Kees,
Thanks for your review - I will incorporate what I can into v3, or
explain why not once I give it a try :).
On Thu, 2020-05-21 at 14:08 -0700, Kees Cook wrote:
> >
<snip>
> On Thu, May 21, 2020 at 09:56:38AM -0700, Kristen Carlson Accardi
> wrote:
> > + /*
> > + * sometimes we are updating a relative offset that would
> > + * normally be relative to the next instruction (such as a
> > call).
> > + * In this case to calculate the target, you need to add 32bits
> > to
> > + * the pc to get the next instruction value. However, sometimes
> > + * targets are just data that was stored in a table such as
> > ksymtab
> > + * or cpu alternatives. In this case our target is not relative
> > to
> > + * the next instruction.
> > + */
>
> Excellent and scary comment. ;) Was this found by trial and error?
> That
> sounds "fun" to debug. :P
This did suck to debug. Thank goodness for debugging with gdb in a VM.
As you know, I had previously had a patch to use a prand to be able to
retain the same layout across boots, and that came in handy here. While
we decided to not submit this functionality with this initial merge
attempt, I will add it on in the future as it does make debugging much
easier when you can reliably duplicate failure modes.
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