linux-kernel - Re: [PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init

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Message-ID: <alpine.DEB.2.20.1711021345550.2090@nanos>
Date:   Thu, 2 Nov 2017 13:56:38 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...capital.net>
cc:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        moritz.lipp@...k.tugraz.at,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        michael.schwarz@...k.tugraz.at, Kees Cook <keescook@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm
 page tables

On Thu, 2 Nov 2017, Andy Lutomirski wrote:
> > On Nov 2, 2017, at 12:33 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > Fair enough. I enabled function tracing with emulate_vsyscall as the filter
> > on a couple of machines and so far I have no hit at all. Though I found a
> > VM with a real old user space (~2005) and that actually used it.
> > 
> > So for the problem at hand, I'd suggest we disable the vsyscall stuff if
> > CONFIG_KAISER=y and be done with it.
> 
> I think that time() on not-so-old glibc uses it.

Sigh.

> Even more recent versions of Go use it. :(

Groan. VDSO is there since 2007 and the first usable version of Go was
released in 2012.....

Thanks,

	tglx