[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20170828095922.GA18012@amd>
Date: Mon, 28 Aug 2017 11:59:23 +0200
From: Pavel Machek <pavel@....cz>
To: Boris Lukashev <blukashev@...pervictus.com>
Cc: Ingo Molnar <mingo@...nel.org>, Thomas Garnier <thgarnie@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Arnd Bergmann <arnd@...db.de>,
Matthias Kaehlcke <mka@...omium.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Joerg Roedel <joro@...tes.org>,
Tom Lendacky <thomas.lendacky@....com>,
Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>,
Brian Gerst <brgerst@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
"Rafael J . Wysocki" <rjw@...ysocki.net>,
Len Brown <len.brown@...el.com>, Tejun Heo <tj@...nel.org>,
Christoph Lameter <cl@...ux.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Chris Metcalf <cmetcalf@...lanox.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
Christopher Li <sparse@...isli.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Lukas Wunner <lukas@...ner.de>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Dou Liyang <douly.fnst@...fujitsu.com>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Markus Trippelsdorf <markus@...ppelsdorf.de>,
Steven Rostedt <rostedt@...dmis.org>,
Kees Cook <keescook@...omium.org>, Rik van Riel <riel@...hat.com>,
David Howells <dhowells@...hat.com>,
Waiman Long <longman@...hat.com>, Kyle Huey <me@...ehuey.com>,
Peter Foley <pefoley2@...oley.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Catalin Marinas <catalin.marinas@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Michal Hocko <mhocko@...e.com>,
Matthew Wilcox <mawilcox@...rosoft.com>,
"H . J . Lu" <hjl.tools@...il.com>, Paul Bolle <pebolle@...cali.nl>,
Rob Landley <rob@...dley.net>, Baoquan He <bhe@...hat.com>,
Daniel Micay <danielmicay@...il.com>,
the arch/x86 maintainers <x86@...nel.org>,
Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>, xen-devel@...ts.xenproject.org,
kvm list <kvm@...r.kernel.org>,
Linux PM list <linux-pm@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
linux-sparse@...r.kernel.org,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Borislav Petkov <bp@...en8.de>
Subject: Re: Re: x86: PIE support and option to extend
KASLR randomization
Hi!
> > + The kernel and modules will generate slightly more assembly (1 to 2%
> > + increase on the .text sections). The vmlinux binary will be
> > + significantly smaller due to less relocations.
> >
> > ... but describing a 1-2% kernel text size increase as "slightly more assembly"
> > shows a gratituous disregard to kernel code generation quality! In reality that's
> > a huge size increase that in most cases will almost directly transfer to a 1-2%
> > slowdown for kernel intense workloads.
> >
> > Where does that size increase come from, if PIE is capable of using relative
> > instructins well? Does it come from the loss of a generic register and the
> > resulting increase in register pressure, stack spills, etc.?
> >
> > So I'm still unhappy about this all, and about the attitude surrounding it.
>
> Is the expectation then to have security functions also decrease size
> and operational latency? Seems a bit unrealistic if so.
> 1-2% performance hit on systems which have become at least several
> hundred % faster over recent years is not a significant performance
> regression compared to the baseline before.
We are probably willing to trade security for 2% performance impact...
if you can show that same security advantage can't be achieved without
the impact (and it is opt-in and documented and so on).
Kernel is not really a bottleneck for many people. For me, even CPUs
are not bottleneck, disk is.
But what is not okay is "hey, this is security, I can slow things
down. Merge it, because... security!".
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Download attachment "signature.asc" of type "application/pgp-signature" (182 bytes)
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
