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=-11.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 01920CA9EA0 for ; Fri, 18 Oct 2019 20:34:00 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 4BC6921925 for ; Fri, 18 Oct 2019 20:33:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KQhoMvQg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BC6921925 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17058-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 26374 invoked by uid 550); 18 Oct 2019 20:33:52 -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 26356 invoked from network); 18 Oct 2019 20:33:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=s5h/GhSdlUicoMowUqjyBoWS/+duNMzdyCGodDdcTtc=; b=KQhoMvQgSY1S7JFuJAFTC9HRZeQ5mdpO9TvuIKoj0v5SvnSQNuvf8amINPFUPzI8nY 7ZIM6uhg5mZL7guVvq0mSjr6gr+NtNERf4pjkYKL/atuXVKYh6ehfKZIXGRfpXFMwBUC ThYtEebG3W5YCny4jaBcl/Q0epyHh1RHZdFHsBm9kE9ybU6tBqxynDXHqthx+xaibjMa 95n/a/SX8ULgLGxFbhmjkRP3CjI5ClIpGsJpW9IT2pdvvEpsvlxPiNChvpjefs0l29Vq fQGmX4cDpEBIZ/Jt5jFZrqKpbzygKQM8pdWXq7Ks30lBud8WR8HSBUqDptTm7GHM8fiq R4uQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=s5h/GhSdlUicoMowUqjyBoWS/+duNMzdyCGodDdcTtc=; b=EC3jjvcLnJQmfpPhiy7bcwCu4UqtB24vv6veC5wtaaLlrKiEVCyEzLSeJF4YTLI/ph j+8tWETqqGvAsn0nLGIcdylXX8UzKte+aXxSdhzh0vvbSUXbsILlp0oaTtr1krhZEQ7S ntglIB14eo2+6i8nsGefgQDIq2jdtuyv1joTBMowRNNkjwVzrGBYQLNFVkDND6sQ92W0 l22JrqGn0x2MgjOMlb+PchKMEBTSlx0Cyglz3wYyHpHF7bS2jtJYncg1TwOlc0it1UNO TW9JXdi14HeDllfZL5/o4QJrsuMiECLu1DaLxSkQpwN3DOgORP4tVv1vfzCvQL1L0K40 jmUQ== X-Gm-Message-State: APjAAAXDYrlfq/44c14RznmFWkpWH+gVKYEHNdTWJ+EF8VDXuTt2RAUm SHXDSDjQcOX+f+wLotl7Q+WJ4flQ9u3QI6MwgNQZEQ== X-Google-Smtp-Source: APXvYqyNa4FKOObSpxuU4QFrkn4kv2RtplqwVoFiBNyGX9dC4x3R93/WFE745QDJwjnJLdnYdKd+pE8O7U/JRiSJhZU= X-Received: by 2002:a17:902:9b83:: with SMTP id y3mr11637082plp.179.1571430819228; Fri, 18 Oct 2019 13:33:39 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-7-samitolvanen@google.com> In-Reply-To: From: Nick Desaulniers Date: Fri, 18 Oct 2019 13:33:27 -0700 Message-ID: Subject: Re: [PATCH 06/18] add support for Clang's Shadow Call Stack (SCS) To: Miguel Ojeda Cc: Sami Tolvanen , Will Deacon , Catalin Marinas , Steven Rostedt , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , clang-built-linux , Kernel Hardening , Linux ARM , LKML Content-Type: text/plain; charset="UTF-8" On Fri, Oct 18, 2019 at 11:33 AM Miguel Ojeda wrote: > > On Fri, Oct 18, 2019 at 7:11 PM Sami Tolvanen wrote: > > > > On Fri, Oct 18, 2019 at 10:08 AM 'Nick Desaulniers' via Clang Built > > Linux wrote: > > > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > > > > index 333a6695a918..9af08391f205 100644 > > > > --- a/include/linux/compiler-clang.h > > > > +++ b/include/linux/compiler-clang.h > > > > @@ -42,3 +42,5 @@ > > > > * compilers, like ICC. > > > > */ > > > > #define barrier() __asm__ __volatile__("" : : : "memory") > > > > + > > > > +#define __noscs __attribute__((no_sanitize("shadow-call-stack"))) > > > > > > It looks like this attribute, (and thus a requirement to use this > > > feature), didn't exist until Clang 7.0: https://godbolt.org/z/p9u1we > > > (as noted above) > > > > > > I think it's better to put __noscs behind a __has_attribute guard in > > > include/linux/compiler_attributes.h. Otherwise, what will happen when > > > Clang 6.0 sees __noscs, for example? (-Wunknown-sanitizers will > > > happen). > > > > Good point, I'll fix this in v2. Thanks. > > +1, please CC whenever you send it! Sami pointed out to me off thread that __has_attribute would only check `no_sanitize`, not `shadow-call-stack`. So maybe best to keep the definition here (include/linux/compiler-clang.h), but wrapped in a `__has_feature` check so that Clang 6.0 doesn't start complaining. -- Thanks, ~Nick Desaulniers