linux-kernel - Re: [RFC] x86: xsave/xrstor support, ucontext

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

Message-ID: <18485.61551.199984.949174@harpo.it.uu.se>
Date:	Fri, 23 May 2008 00:15:11 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mikael Pettersson <mikpe@...uu.se>,
	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	tglx@...utronix.de, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, roland@...hat.com, drepper@...hat.com,
	Hongjiu.lu@...el.com, linux-kernel@...r.kernel.org,
	arjan@...ux.intel.com, rmk+lkml@....linux.org.uk, dan@...ian.org,
	asit.k.mallick@...el.com
Subject: Re: [RFC] x86: xsave/xrstor support, ucontext_t extensions

Chris Wright writes:
 > * H. Peter Anvin (hpa@...or.com) wrote:
 > > Suresh Siddha wrote:
 > >>
 > >> hpa, What is the virtualization problem? Are you referring to perf problem?
 > >> As you noted, regular non-rt signal handlers won't need this cpuid check. It's
 > >> needed only for those who manually look at non-rt signal frames and interpret it.
 > >> And also, they can do this check only once and not everytime.
 > >>
 > >
 > > No, relying on CPUID and vdso both have implications for virtualization.
 > 
 > hmm, what implications?  cpuid is dealt with already.

By whom?

Case in point: only a few weeks ago, we (as in LKML hackers) tried
to debug a user's bug report. Something very strange seemed to be
going on. It turned out the user was actually using a virtualisation
engine (qemu, not the latest) which presented highly inconsistent
cpuid data to the kernel, causing major confusion.

So I agree with hpa. The kernel has decided to use a particular
sigframe layout. It should communicate this to user-space in a robust
manner that is independent of how the kernel arrived at this decision.
--
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/