From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 62F48CA9EAF for ; Thu, 24 Oct 2019 14:39:17 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id AC22320679 for ; Thu, 24 Oct 2019 14:39:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nifty.com header.i=@nifty.com header.b="Wsq8rdKb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC22320679 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=socionext.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17100-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 3899 invoked by uid 550); 24 Oct 2019 14:39:08 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 3879 invoked from network); 24 Oct 2019 14:39:07 -0000 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-04.nifty.com x9OEcio6009139 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1571927925; bh=5VDOJqWr1P/8RpUKJUiUUgzqRYMuViQTbISV22/DfcM=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Wsq8rdKbjufD8xDQo9TYn/vVPfLqU8CWHsul4oOcXL2+aXPYpencUJWWwSK3e35D2 r1rM9S/WmrTYaz2BZmvK3Q++Ya6W+X/E7doaUDPGpJqtcrfyTmXmvYas9LC6dtz7c6 +Wp7bga0LwmkjxC7bnK3lfeIWZErlsOVJtEDo2V3S2VPEdRk6duBPk4lRsrsWbDSL/ STw5curdVNiU7mM8M4A4aCs4z+NHeoPxk0Ve0g/XI+teLFDGPSgtiQYnJpzl/UW1DT /q3CPziyC8B8u7V6ef2AEzLzPC2Ud+TpShsgQS4VnFZCerdl+NYBUp2z94XzY4M3Fp 7AXuq/dNyMwFA== X-Nifty-SrcIP: [209.85.217.44] X-Gm-Message-State: APjAAAVcA3XhRBSCl0Ka7wX3fuXyVuW5WXoWf2YUcR2wcr7BaObb+bI5 NEyNA6AsHp44RJTdk3OA0q/jVUbYxJKe+y/Y17Y= X-Google-Smtp-Source: APXvYqzTx9f4+sdDvCmM/G0tcS16/98SXXq+GzkLjkICnXwW7kaMiC+gdVtM0Mg1KgO8XJEVHwsWres9Ec0jaj70OCs= X-Received: by 2002:a67:e290:: with SMTP id g16mr6201871vsf.54.1571927924100; Thu, 24 Oct 2019 07:38:44 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-7-samitolvanen@google.com> <20191022162826.GC699@lakrids.cambridge.arm.com> <20191024132832.GG4300@lakrids.cambridge.arm.com> In-Reply-To: <20191024132832.GG4300@lakrids.cambridge.arm.com> From: Masahiro Yamada Date: Thu, 24 Oct 2019 23:38:07 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS) To: Mark Rutland Cc: Sami Tolvanen , Will Deacon , Catalin Marinas , Steven Rostedt , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Nick Desaulniers , clang-built-linux , Kernel Hardening , linux-arm-kernel , LKML Content-Type: text/plain; charset="UTF-8" On Thu, Oct 24, 2019 at 10:28 PM Mark Rutland wrote: > > On Tue, Oct 22, 2019 at 12:26:02PM -0700, Sami Tolvanen wrote: > > On Tue, Oct 22, 2019 at 9:28 AM Mark Rutland wrote: > > > > > +config SHADOW_CALL_STACK > > > > + bool "Clang Shadow Call Stack" > > > > + depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > > > > + depends on CC_IS_CLANG && CLANG_VERSION >= 70000 > > > > > > Is there a reason for an explicit version check rather than a > > > CC_HAS_ check? e.g. was this available but broken in prior > > > versions of clang? > > > > No, this feature was added in Clang 7. However, > > -fsanitize=shadow-call-stack might require architecture-specific > > flags, so a simple $(cc-option, -fsanitize=shadow-call-stack) in > > arch/Kconfig is not going to work. I could add something like this to > > arch/arm64/Kconfig though: > > > > select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK > > ... > > config CC_HAVE_SHADOW_CALL_STACK > > def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18) > > > > And then drop CC_IS_CLANG and version check entirely. Thoughts? > > That sounds good to me, yes! > > Thanks, > Mark. If you use cc-option, please add a comment like # supported by Clang 7 or later. I do not know the minimal supported clang version. When we bump the minimal version to clang 7, we can drop the cc-option test entirely. -- Best Regards Masahiro Yamada