linux-kernel - Re: [RFC PATCH v9 18/27] x86/cet/shstk: Introduce WRUSS instruction

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Date:   Thu, 05 Mar 2020 10:39:08 -0800
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     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>,
        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>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>, x86-patch-review@...el.com
Subject: Re: [RFC PATCH v9 18/27] x86/cet/shstk: Introduce WRUSS instruction

On Tue, 2020-02-25 at 13:10 -0800, Kees Cook wrote:
> On Wed, Feb 05, 2020 at 10:19:26AM -0800, Yu-cheng Yu wrote:
> > WRUSS is a new kernel-mode instruction but writes directly to user Shadow
> > Stack (SHSTK) memory.  This is used to construct a return address on SHSTK
> > for the signal handler.
> > 
> > This instruction can fault if the user SHSTK is not valid SHSTK memory.
> > In that case, the kernel does a fixup.
> 
> Since these functions aren't used in this patch, should this get merged
> with patch 19?

Yes, I can do that.

Yu-cheng