From: Andi Kleen <andi@firstfloor.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <andi@firstfloor.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Updated version of RD/WR FS/GS BASE patchkit
Date: Mon, 21 Mar 2016 20:03:23 +0100 [thread overview]
Message-ID: <20160321190322.GZ5083@two.firstfloor.org> (raw)
In-Reply-To: <CALCETrXvREAXmjS-FkAMTDYDnTsBsrAYGKo32=fgEGJqC8k6Yg@mail.gmail.com>
On Mon, Mar 21, 2016 at 11:39:07AM -0700, Andy Lutomirski wrote:
> 4. Does the sigcontext format need to change?
I don't think it needs to be. fs/gs are global state and the
signal handlers are not likely to change it.
Also there is no default that could be restored.
>
> For maximum safely, comprehensibility, and sanity, there's an argument
> to be made that 1a and 2a should leave the state exactly as it started
> and that 1b and 2b should leave it alone unless percpu bases are in
> use. For maximum simplicity of implementation, there's an argument
> that, if the fs or gs selector is nonzero and the base doesn't match
> the in-memory descriptor, then the kernel can do whatever it wants.
>
> I propose the following semantics:
So you want to change the existing semantics. We had this discussion
before. I think it is out of scope of my patch, which just extends the
existing semantics to support the instructions.
(what happened in the system call before is now possible in ring 3)
If you want to invent some new overengineered semantics you can do it in some
followon patch.
Personally i think it is pointless. The existing semantics are fine.
> Does all this make sense? Do people agree with me?
I think you are overcomplicated something fundamentally simple.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2016-03-21 19:22 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-21 16:16 Updated version of RD/WR FS/GS BASE patchkit Andi Kleen
2016-03-21 16:16 ` [PATCH 1/9] x86: Add intrinsics/macros for new rd/wr fs/gs base instructions Andi Kleen
2016-03-21 18:14 ` Andy Lutomirski
2016-03-21 16:16 ` [PATCH 2/9] x86: Add support for rd/wr fs/gs base Andi Kleen
2016-03-21 18:13 ` Andy Lutomirski
2016-03-21 19:05 ` Andi Kleen
2016-03-21 19:22 ` Andy Lutomirski
2016-03-21 22:05 ` Andi Kleen
2016-03-21 22:08 ` Andy Lutomirski
2016-03-21 22:15 ` Andi Kleen
2016-03-22 8:36 ` Thomas Gleixner
2016-03-22 14:40 ` Brian Gerst
2016-04-15 0:06 ` Andy Lutomirski
2016-03-21 16:16 ` [PATCH 3/9] x86: Make old K8 swapgs workaround conditional Andi Kleen
2016-03-21 16:16 ` [PATCH 4/9] x86: Enumerate kernel FSGS capability in AT_HWCAP2 Andi Kleen
2016-03-21 18:49 ` Brian Gerst
2016-03-21 18:54 ` Andi Kleen
2016-03-21 19:32 ` Brian Gerst
2016-03-21 19:43 ` Andi Kleen
2016-03-21 22:10 ` Andy Lutomirski
2016-03-21 16:16 ` [PATCH 5/9] x86: Add documentation for rd/wr fs/gs base Andi Kleen
2016-03-23 19:14 ` Valdis.Kletnieks
2016-03-21 16:16 ` [PATCH 6/9] x86: Use rd/wr fs/gs base in arch_prctl Andi Kleen
2016-03-21 18:17 ` Andy Lutomirski
2016-03-21 16:16 ` [PATCH 7/9] x86: Add self test code for fsgsbase Andi Kleen
2016-03-21 16:16 ` [PATCH 8/9] x86: Support arbitrary fs/gs base in getregs Andi Kleen
2016-03-21 16:16 ` [PATCH 9/9] x86: Save FS/GS base in core dump Andi Kleen
2016-03-21 18:39 ` Updated version of RD/WR FS/GS BASE patchkit Andy Lutomirski
2016-03-21 19:03 ` Andi Kleen [this message]
2016-03-21 19:23 ` Andy Lutomirski
2016-03-21 19:40 ` Andi Kleen
2016-03-21 22:05 ` Andy Lutomirski
2016-03-21 22:11 ` Andi Kleen
2016-03-21 22:27 ` Andy Lutomirski
2016-03-21 22:41 ` Andi Kleen
2016-03-21 22:47 ` Andy Lutomirski
2016-03-21 22:52 ` Andi Kleen
2016-03-21 22:57 ` Andy Lutomirski
2016-03-21 23:02 ` Andi Kleen
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=20160321190322.GZ5083@two.firstfloor.org \
--to=andi@firstfloor.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=x86@kernel.org \
/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).