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([2600:1010:b069:8a27:ddd9:92ea:d62b:8a52]) by smtp.gmail.com with ESMTPSA id j21sm4165728pji.13.2020.02.26.19.57.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Feb 2020 19:57:03 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [RFC PATCH v9 05/27] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack protection Date: Wed, 26 Feb 2020 19:57:01 -0800 Message-Id: References: Cc: Dave Hansen , Yu-cheng Yu , the arch/x86 maintainers , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , x86-patch-review@intel.com In-Reply-To: To: "H.J. Lu" X-Mailer: iPhone Mail (17D50) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Feb 26, 2020, at 6:11 PM, H.J. Lu wrote: >=20 > =EF=BB=BFOn Wed, Feb 26, 2020 at 5:16 PM Dave Hansen wrote: >>=20 >> On 2/26/20 5:02 PM, H.J. Lu wrote: >>>> That way everybody with old toolchains can still build the kernel (and >>>> run/test code with your config option on, btw...). >>> CET requires a complete new OS image from kernel, toolchain, run-time. >>> CET enabled kernel without the rest of updated OS won't give you CET >>> at all. >>=20 >> If you require a new toolchain, nobody even builds your fancy feature. >> Probably including 0day and all of the lazy maintainers with crufty old >> distros. >=20 > GCC 8 or above is needed since vDSO must be compiled with > --fcf-protection=3Dbranch. Fair enough. I don=E2=80=99t particularly want to carry a gross hack to add t= he ENDBRANCHes without compiler support.