linux-kernel - Re: [PATCH 1/7] arm: use generic fixmap.h

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1407432194.599.13.camel@deneb.redhat.com>
Date:	Thu, 07 Aug 2014 13:23:14 -0400
From:	Mark Salter <msalter@...hat.com>
To:	Max Filippov <jcmvbkbc@...il.com>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Liu hua <sdu.liu@...wei.com>, Rabin Vincent <rabin@....in>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Doug Anderson <dianders@...gle.com>,
	Will Deacon <will.deacon@....com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/7] arm: use generic fixmap.h

On Thu, 2014-08-07 at 19:42 +0400, Max Filippov wrote:
> On Thu, Aug 7, 2014 at 7:32 PM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> > On Thu, 7 Aug 2014, Rob Herring wrote:
> >
> >> On Thu, Aug 7, 2014 at 10:15 AM, Max Filippov <jcmvbkbc@...il.com> wrote:
> >> > Hi,
> >> >
> >> > On Wed, Aug 6, 2014 at 11:32 PM, Kees Cook <keescook@...omium.org> wrote:
> >> >> ARM is different from other architectures in that fixmap pages are indexed
> >> >> with a positive offset from FIXADDR_START.  Other architectures index with
> >> >> a negative offset from FIXADDR_TOP.  In order to use the generic fixmap.h
> >> >
> >> > Does anybody know if there's any reason why generic fixmap.h uses negative
> >> > offsets? It complicates things with no obvious benefit if you e.g. try to align
> >> > virtual address in the fixmap region with physical page color (that's why I've
> >> > switched xtensa to positive fixmap addressing in v3.17).
> >>
> >> No, but each arch doing it differently is even more annoying.
> >
> > Why not switching everybody to positive offsets then?
> 
> I can cook a patch if people agree that that'd be good.
> 

I think that would be fine. I think x86 was first and used a negative
negative offset. Others that followed just copied that. When I did the
generic fixmap patch, using a negative offset was the natural thing to
do. Arm was only arch doing it differently.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/