From: Andy Lutomirski <luto@kernel.org>
To: "Bae, Chang Seok" <chang.seok.bae@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
Andi Kleen <ak@linux.intel.com>, "H. Peter Anvin" <hpa@zytor.com>,
"Metzger, Markus T" <markus.t.metzger@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 14/15] x86/fsgsbase/64: Support legacy behavior when FS/GS updated by ptracer
Date: Thu, 22 Mar 2018 01:40:38 +0000 [thread overview]
Message-ID: <CALCETrUxQ1XOs7V1XKOsk-iQ-qOwn41sWGYkepkVOE7PtfX24A@mail.gmail.com> (raw)
In-Reply-To: <E9221EFA-636C-4D36-AEBA-3A1EEBBF2F50@intel.com>
On Wed, Mar 21, 2018 at 3:11 PM, Bae, Chang Seok
<chang.seok.bae@intel.com> wrote:
> On 3/20/18, 17:47, "Andy Lutomirski" <luto@kernel.org> wrote:
>> If I've understood all your emails right, when you looked at existing
>> ptrace users, you found that all of them that write to gs and/or
>> gs_base do it as part of a putregs call that writes them at the same
>> time. If so, then your patch does exactly the same thing that my old
>> patches did, but your patch is much more complicated. So why did you
>> add all that complexity?
>
> What is tried to be provided is backward compatibility by emulating
> “mov gs (fs) …” when index is only changed and preserve a (given) base value
> in other cases.
mov to gs changes GSBASE even if GS was unchanged.
But it's not clear to me that you've identified any case where
emulating this behavior is useful.
next prev parent reply other threads:[~2018-03-22 1:41 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-19 17:49 [PATCH 00/15] x86: Enable FSGSBASE instructions Chang S. Bae
2018-03-19 17:49 ` [PATCH 01/15] x86/fsgsbase/64: Introduce FS/GS base helper functions Chang S. Bae
2018-03-19 17:49 ` [PATCH 02/15] x86/fsgsbase/64: Make ptrace read FS/GS base accurately Chang S. Bae
2018-03-19 17:49 ` [PATCH 03/15] x86/fsgsbase/64: Use FS/GS base helpers in core dump Chang S. Bae
2018-03-19 17:49 ` [PATCH 04/15] x86/fsgsbase/64: Factor out load FS/GS segments from __switch_to Chang S. Bae
2018-03-19 17:49 ` [PATCH 05/15] x86/ptrace: A new macro to get an offset of user_regs_struct Chang S. Bae
2018-03-19 17:49 ` [PATCH 06/15] x86/fsgsbase/64: Add putregs() to handle multiple elements' setting Chang S. Bae
2018-03-19 17:49 ` [PATCH 07/15] x86/fsgsbase/64: putregs() in a reverse order Chang S. Bae
2018-03-19 17:49 ` [PATCH 08/15] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2018-03-19 17:49 ` [PATCH 09/15] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2018-03-19 17:49 ` [PATCH 10/15] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Chang S. Bae
2018-03-19 17:49 ` [PATCH 11/15] x86/fsgsbase/64: Preserve FS/GS state in __switch_to if FSGSBASE is on Chang S. Bae
2018-03-19 17:49 ` [PATCH 12/15] x86/fsgsbase/64: When copying a thread, use FSGSBASE if enabled Chang S. Bae
2018-03-19 17:49 ` [PATCH 13/15] x86/fsgsbase/64: With FSGSBASE, compare GS bases on paranoid_entry Chang S. Bae
2018-03-19 20:05 ` Dave Hansen
2018-03-19 21:12 ` Bae, Chang Seok
2018-03-20 10:16 ` David Laight
2018-03-20 20:07 ` H. Peter Anvin
2018-03-20 20:36 ` Bae, Chang Seok
2018-03-21 0:36 ` Andy Lutomirski
2018-03-21 21:56 ` H. Peter Anvin
2018-03-20 14:58 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-20 17:03 ` Bae, Chang Seok
2018-03-21 22:03 ` H. Peter Anvin
2018-03-22 1:37 ` Andy Lutomirski
2018-03-19 17:49 ` [PATCH 14/15] x86/fsgsbase/64: Support legacy behavior when FS/GS updated by ptracer Chang S. Bae
2018-03-20 15:04 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-21 0:47 ` Andy Lutomirski
2018-03-21 7:01 ` Metzger, Markus T
2018-03-22 1:39 ` Andy Lutomirski
2018-03-21 15:11 ` Bae, Chang Seok
2018-03-22 1:40 ` Andy Lutomirski [this message]
2018-03-22 15:45 ` Bae, Chang Seok
2018-03-22 16:07 ` Andy Lutomirski
2018-03-22 16:46 ` Bae, Chang Seok
2018-03-22 16:53 ` Andy Lutomirski
2018-03-22 21:17 ` Bae, Chang Seok
2018-03-22 21:28 ` Andy Lutomirski
2018-03-19 17:49 ` [PATCH 15/15] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2018-03-20 15:05 ` [PATCH 00/15] x86: Enable FSGSBASE instructions Andy Lutomirski
2018-03-20 15:06 ` Andy Lutomirski
2018-03-20 16:33 ` Bae, Chang Seok
2018-03-21 0:40 ` Andy Lutomirski
2018-03-21 15:15 ` Bae, Chang Seok
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