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Date: Mon, 14 Aug 2017 16:53:25 +0100
From: Dave Martin <Dave.Martin@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Mark Rutland <mark.rutland@....com>, Kees Cook <keescook@...omium.org>,
Arnd Bergmann <arnd@...db.de>, Nicolas Pitre <nico@...aro.org>,
Marc Zyngier <marc.zyngier@....com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Russell King <linux@...linux.org.uk>,
Tony Lindgren <tony@...mide.com>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
Thomas Garnier <thgarnie@...gle.com>,
Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH 02/30] ARM: assembler: introduce adr_l, ldr_l and str_l
macros
On Mon, Aug 14, 2017 at 04:40:55PM +0100, Ard Biesheuvel wrote:
> On 14 August 2017 at 16:32, Dave Martin <Dave.Martin@....com> wrote:
> > On Mon, Aug 14, 2017 at 01:53:43PM +0100, Ard Biesheuvel wrote:
[...]
> >> So use the above to implement the macros mov_l, adr_l, adrm_l (using ldm
> >
> > I don't see adrm_l in this patch.
> >
>
> Oops (2)
>
> Nico already mentioned that, and I failed to fix the commit log. I
> added it at some point, but it wasn't really useful
Thought it might be something like that.
> >> to load multiple literals at once), ldr_l and str_l, all of which will
> >> use movw/movt pairs on v7 and later CPUs, and use PC-relative literals
> >> otherwise.
> >
> > Also...
> >
> > By default, I'd assume that we should port _all_ uses of :upper16:/
> > :lower16: to use these. Does this series consciously do that? Are
> > there any exceptions?
> >
>
> There aren't that many. Anything that refers to absolute symbols will
> break under CONFIG_RELOCATABLE and I haven't noticed any issues (I
> tested extensively with Thumb2)
>
> I don't mind open coded movw/movt for relative references in code that
> is tightly coupled to a platform that guarantees v7+ so I didn't do a
> full sweep. Also, I started with 50+ patches and tried to remove the
> ones that are mostly orthogonal to the KASLR stuff.
OK, that sounds reasonable.
Cheers
---Dave
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