Re: [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode

From: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: "Martin Schwidefsky"
	<schwidefsky-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
	"Heiko Carstens"
	<heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
	"Dave Hansen"
	<dave.hansen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	"Arnd Bergmann" <arnd-r2nGTMty4D4@public.gmane.org>,
	"David Howells"
	<dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"René Nyffenegger"
	<mail-gLCNRsNSrVdVZEhyV+6z5nIPMjoJpjVV@public.gmane.org>,
	"Andrew Morton"
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	"Paul E . McKenney"
	<paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
	"Eric W . Biederman"
	<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
	"Thomas Gleixner" <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	"Oleg Nesterov" <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"Pavel Tikhomirov"
	<ptikhomirov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>,
	"Ingo Molnar" <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"H . Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
	"Andy Lutomirski" <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	"Paolo Bonzini"
	<pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"Kees Cook" <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	"Rik van Riel" <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"Josh Poimboeuf" <jpoimboe@redhat.c>
Subject: Re: [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode
Date: Fri, 28 Apr 2017 08:33:23 +0200	[thread overview]
Message-ID: <20170428063323.ntnc4tk7do2dor76@gmail.com> (raw)
In-Reply-To: <CAJcbSZENjCgn3TNDGzCBBSOXMvbTX8mBO7Trugdb5VRzhxwmHg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

* Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:

> > BTW., a further simplification would be:
> >
> > #ifndef ADDR_LIMIT_CHECK_PRE
> > # define ADDR_LIMIT_CHECK_PRE ...
> > #endif
> >
> > This way architectures could override this generic functionality simply by
> > defining the helpers. Architectures that don't do that get the generic version.
> 
> I don't think architectures need to do that. The optimizations are
> embedding the checks on their architecture-specific code to make it
> faster and remove the size impact. The pre/post is fine for the rest.

Indeed, only the generic code needs to turn off that code - architectures will 
place these callbacks elsewhere.

Thanks,

	Ingo