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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id g76-v6sm24702360wmd.25.2018.11.01.07.34.23 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 01 Nov 2018 07:34:24 -0700 (PDT) Date: Thu, 1 Nov 2018 15:34:21 +0100 From: Ingo Molnar To: Thomas Gleixner Cc: "Woodhouse, David" , "zhenzhong.duan@oracle.com" , "linux-kernel@vger.kernel.org" , "daniel@iogearbox.net" , "peterz@infradead.org" , "bp@suse.de" , "srinivas.eeda@oracle.com" , "konrad.wilk@oracle.com" , "michal.lkml@markovi.net" , "hpa@zytor.com" , "mingo@redhat.com" , "yamada.masahiro@socionext.com" , "luto@kernel.org" Subject: Re: [PATCH v2 1/2] retpolines: Only enable retpoline support when compiler support it Message-ID: <20181101143421.GA81370@gmail.com> References: <991cbe9b-1e31-4b12-b572-91fde5c79699@default> <20181101095002.GA118944@gmail.com> <90a9eed724b28d5af57a71694a95b4cd92728ccc.camel@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner wrote: > On Thu, 1 Nov 2018, Woodhouse, David wrote: > > On Thu, 2018-11-01 at 10:50 +0100, Ingo Molnar wrote: > > > * Zhenzhong Duan wrote: > > > > > > > Since retpoline capable compilers are widely available, make > > > > CONFIG_RETPOLINE hard depend on it. > > > > > > > > The check of RETPOLINE is changed to CONFIG_RETPOLINE. > > > > > > > > This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016 > > > > > > > > Signed-off-by: Zhenzhong Duan > > > > Cc: Thomas Gleixner > > > > Cc: Peter Zijlstra > > > > > > Please turn such 'based on suggestions' into proper tags as well, i.e. > > > something like: > > > > > > Suggested-by: David Woodhouse > > > > I think the suggestion came from PeterZ; I just acked it. > > > > Although on furthe reflection, I think I'd prefer a build break if > > retpoline is enabled in the kernel config and the compiler doesn't > > support it. This patch would make it silently fail to be secure. > > Agreed. Yeah, I agree that that's the best policy: if someone wants retpoline support it shouldn't silently turn off just because the wrong toolchain was used to build the kernel ... Thanks, Ingo