linux-kernel - Re: [PATCH v28 00/32] Control-flow Enforcement: Shadow Stack

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Date:   Fri, 23 Jul 2021 10:28:38 -0700
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-arch@...r.kernel.org>, <linux-api@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Eugene Syromiatnikov" <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Rick P Edgecombe <rick.p.edgecombe@...el.com>
Subject: Re: [PATCH v28 00/32] Control-flow Enforcement: Shadow Stack

On 7/22/2021 2:08 PM, Dave Hansen wrote:
> On 7/22/21 1:51 PM, Yu-cheng Yu wrote:
>> Linux distributions with CET are available now, and Intel processors with CET
>> are already on the market.  It would be nice if CET support can be accepted
>> into the kernel.
>>
>> Changes in v28:
>> - Rebase to Linus tree v5.14-rc2.
>> - Patch #1: Update Document to indicate no-user-shstk also disables IBT.
>> - Patch #23: Update shstk_setup() with wrmsrl_safe().  Update return value.
>> - Patch #25: Split out copy_thread() changes.  Add support for old clone().
>>    Add comments.
>> - Add comments for get_xsave_addr() (Patch #25, #26).
> 
> Could you characterize where this whole thing is?
> 
> Are we at the point where the feedback is slowing down?  What kind of
> feedback are you getting?  How stable is the ABI versus the last revision?
> 

The ABI has not changed since last version, except the addition of 
shadow stack support for legacy clone().  This does not de-stabilize the 
ABI.

Looking back at recent feedback:

- Boris had given lots of comments on code flow, syntax, etc.  Those are 
all addressed.

- Andy L. commented on the signal handling part, especially the 
introduction of a ucontext extension.  That is eliminated and now there 
is the UC_WAIT_ENDBR flag.

- Kirill commented a few issues on mm patches.  Those are addressed.

- Peter Z. requested splitting shadow stack and ibt.  That is done.

As for running/testing of the series, overall it is stable.

Yu-cheng