From: Ingo Molnar <mingo@kernel.org>
To: Thomas Garnier <thgarnie@google.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
Andy Lutomirski <luto@kernel.org>,
Arjan van de Ven <arjan@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave@sr71.net>, Chen Yucong <slaoub@gmail.com>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Andrew Morton <akpm@linux-foundation.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Anna-Maria Gleixner <anna-maria@linutronix.de>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Michael Ellerman <mpe@ellerman.id.au>,
Juergen Gross <jgross@suse.com>,
Richard Weinberger <richard@nod.at>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [RFC] x86/mm/KASLR: Remap GDTs at fixed location
Date: Fri, 6 Jan 2017 07:49:00 +0100 [thread overview]
Message-ID: <20170106064900.GC28091@gmail.com> (raw)
In-Reply-To: <CAJcbSZETh-A+zABOzsx+VW3p73AXO4xnc=O_TG7iXaVbD=Zz1A@mail.gmail.com>
* Thomas Garnier <thgarnie@google.com> wrote:
> >> Not sure I fully understood and I don't want to miss an important point. Do
> >> you mean making GDT (remapping and per-cpu) read-only and switch the
> >> writeable flag only when we write to the per-cpu entry?
> >
> > What I mean is: write to the GDT through normal percpu access (or whatever the
> > normal mapping is) but load a read-only alias into the GDT register. As long
> > as nothing ever tries to write through the GDTR alias, no page faults will be
> > generated. So we just need to make sure that nothing ever writes to it
> > through GDTR. AFAIK the only reason the CPU ever writes to the address in
> > GDTR is to set an accessed bit.
>
> A write is made when we use load_TR_desc (ltr). I didn't see any other yet.
Is this write to the GDT, generated by the LTR instruction, done unconditionally
by the hardware?
Thanks,
Ingo
next prev parent reply other threads:[~2017-01-06 6:57 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 22:16 [RFC] x86/mm/KASLR: Remap GDTs at fixed location Thomas Garnier
2017-01-05 8:11 ` Ingo Molnar
2017-01-05 15:08 ` Arjan van de Ven
2017-01-05 16:40 ` Thomas Garnier
2017-01-05 18:56 ` Arjan van de Ven
2017-01-05 19:00 ` Thomas Garnier
2017-01-06 17:44 ` Borislav Petkov
2017-01-06 18:04 ` Thomas Garnier
2017-01-05 16:39 ` Thomas Garnier
2017-01-06 6:34 ` Ingo Molnar
2017-01-05 17:51 ` Andy Lutomirski
2017-01-05 17:54 ` Thomas Garnier
2017-01-05 18:01 ` Andy Lutomirski
2017-01-05 18:35 ` Thomas Garnier
2017-01-05 18:58 ` Arjan van de Ven
2017-01-05 19:03 ` Thomas Garnier
2017-01-05 20:18 ` Andy Lutomirski
2017-01-05 21:08 ` Thomas Garnier
2017-01-05 21:19 ` Andy Lutomirski
2017-01-05 21:58 ` Thomas Garnier
2017-01-06 6:49 ` Ingo Molnar [this message]
2017-01-06 18:03 ` Thomas Garnier
2017-01-06 21:59 ` Andy Lutomirski
2017-01-06 22:54 ` Thomas Garnier
2017-01-06 23:39 ` Andy Lutomirski
2017-01-07 7:45 ` Ingo Molnar
2017-01-07 15:58 ` Andy Lutomirski
2017-01-07 7:35 ` Ingo Molnar
2017-01-07 16:02 ` Andy Lutomirski
2017-01-09 22:32 ` Thomas Garnier
2017-01-10 10:27 ` Ingo Molnar
2017-01-10 17:13 ` Thomas Garnier
2017-01-05 23:05 ` Linus Torvalds
2017-01-05 23:16 ` Thomas Garnier
2017-01-06 2:34 ` Andy Lutomirski
2017-01-06 18:02 ` Thomas Garnier
2017-01-06 21:53 ` Andy Lutomirski
2017-01-07 7:46 ` Ingo Molnar
2017-01-06 6:45 ` Ingo Molnar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170106064900.GC28091@gmail.com \
--to=mingo@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=anna-maria@linutronix.de \
--cc=arjan@linux.intel.com \
--cc=bigeasy@linutronix.de \
--cc=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=dave@sr71.net \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=luto@amacapital.net \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=paul.gortmaker@windriver.com \
--cc=richard@nod.at \
--cc=slaoub@gmail.com \
--cc=tglx@linutronix.de \
--cc=thgarnie@google.com \
--cc=x86@kernel.org \
--cc=yamada.masahiro@socionext.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).