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Date:   Tue, 4 Oct 2022 11:44:16 +0300
From:   Mike Rapoport <rppt@kernel.org>
To:     Kees Cook <keescook@chromium.org>
Cc:     Rick Edgecombe <rick.p.edgecombe@intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        joao.moreira@intel.com, John Allen <john.allen@amd.com>,
        kcc@google.com, eranian@google.com, jamorris@linux.microsoft.com,
        dethoma@microsoft.com, Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: Re: [OPTIONAL/RFC v2 37/39] x86/cet: Add PTRACE interface for CET
Message-ID: <YzvyYDOg8GZIBtz8@kernel.org>
References: <20220929222936.14584-1-rick.p.edgecombe@intel.com>
 <20220929222936.14584-38-rick.p.edgecombe@intel.com>
 <202210031658.EEC88324FD@keescook>
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On Mon, Oct 03, 2022 at 04:59:43PM -0700, Kees Cook wrote:
> On Thu, Sep 29, 2022 at 03:29:34PM -0700, Rick Edgecombe wrote:
> > From: Yu-cheng Yu <yu-cheng.yu@intel.com>
> > 
> > Some applications (like GDB and CRIU) would like to tweak CET state via
> 
> Eee. Does GDB really need this? Can we make this whole thing
> CONFIG-depend on CRIU?

GDB, at least its Intel fork uses this. I don't see how they can jump
between frames without an ability to modify shadow stack contents.

Last I looked they used NT_X86_CET to update SSP and ptrace(POKEDATA) to
write to the shadow stack.
 
> -- 
> Kees Cook

-- 
Sincerely yours,
Mike.