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Lu" Date: Wed, 26 Feb 2020 18:11:17 -0800 Message-ID: Subject: Re: [RFC PATCH v9 05/27] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack protection To: Dave Hansen Cc: 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 Content-Type: text/plain; charset="UTF-8" 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 Wed, Feb 26, 2020 at 5:16 PM Dave Hansen wrote: > > 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. > > 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. GCC 8 or above is needed since vDSO must be compiled with --fcf-protection=branch. > The point isn't to actually run CET at all. The point is to get as many > people as possible testing as much of it as possible. Testing includes > compile testing, static analysis and bloat watching. It also includes > functional and performance testing when you've got the feature compiled > in but unavailable at runtime. Did this hurt anything even when I'm not > using it? > I will leave the CET toolchain issue to Yu-cheng. -- H.J.