linux-kernel - Re: [PATCH 03/25] xen: Add nosegneg capability to the vsyscall page notes

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: <462DA159.2030600@goop.org>
Date:	Mon, 23 Apr 2007 23:19:05 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Roland McGrath <roland@...hat.com>
CC:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: [PATCH 03/25] xen: Add nosegneg capability to the vsyscall page
 notes

Roland McGrath wrote:
>> I have to admit I still don't really understand all this.  Is it
>> documented somewhere?
>>     
>
> I have explained it in public more than once, but I don't know off hand
> anywhere that was helpfully recorded.
>   

Thanks very much.  I'd been poking about, but the closest I came to an
actual description was various patches fixing bugs, so it was a little
incomplete.

> For example, a Xen-enabled kernel can use a single vDSO image (or a single
> pair of int80/sysenter images), containing the "nosegneg" hwcap note.  When
> there is no need for it (native or hvm or 64-bit hv or whatever), it just
> clears the mask word.  If you actually do this, you'll want to modify the
> NOTE_KERNELCAP_BEGIN macro to define a global label you can use with VDSO_SYM.
>   

Thanks for the pointer.  I'd been getting a bit of heat for enabling the
nonegseg flag unconditionally.  If I can make Xen-specific then that
will be one less source of complaints.

    J
-
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/