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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 A8C47C43142 for ; Mon, 30 Jul 2018 20:01:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 50AB020857 for ; Mon, 30 Jul 2018 20:01:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="I8e98gh0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 50AB020857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732010AbeG3ViA (ORCPT ); Mon, 30 Jul 2018 17:38:00 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:53562 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731904AbeG3Vh7 (ORCPT ); Mon, 30 Jul 2018 17:37:59 -0400 Received: by mail-wm0-f66.google.com with SMTP id s9-v6so630718wmh.3; Mon, 30 Jul 2018 13:01:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=aYbEuuEymCMOEvWE8VMBNTm0H1Ih87GNt+6/xIuYeDE=; b=I8e98gh0bh11qrH7I7Te2toyi8NmGGDDY9nUDIFQJEnzRFbla5JTs0XfbYWam3K8Ae nKNV/T7hXQ5F95xvLk04zM/hwoBq892HVbI9UFbziKpzFtX8xEdS6s/Wy1s/JWFDxuCz piwEErQ89p2RSPs7Fig0J3lwznWORLrwgyRiyfBJ0XvLiNd3lq1+viJr3lDLiA+dSyf+ +++PuWWRGRzclRIZSMR+tIc4M8VROqDlae2w4F5XFKGegBAQHPWom8YhLCSVTHUFSam3 /bEAiEpbHofalBmJHrIZEL8aJ4i3LCpssj3gwlCgLf9Sw6lWUvCVYH/S1Zjva+uGNKz0 +8+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=aYbEuuEymCMOEvWE8VMBNTm0H1Ih87GNt+6/xIuYeDE=; b=ZGTEB/1L1k0qziaYjhz5DZAF+LeEc6c/P/5bus7pSRhtdumPCTM5b7EymNNVW2qh/D HbpAYXiHeh2iZNR8/nDxayUgAE11A9FJFgsoPE7thaVOdgy9cRkh83bkg45vPlnPE4TZ oI3+hdq/mf0KB1GDwaQIbjlO78LMo5aKZ0VTkSPFh2z9h/e1hiLK6iSTe6BYIIs4CzSk wuNJ2aKMO20U/oSvEXmSy8Msix321L4UuQrwwZ1KEcloe9oQi/oHaOaNE9Bmjztig0F6 LRge6nFvVgfyz0G+8VEOsze5Le/7T0pMnJjQ5ZMugpLK0oRM0zXFhOVOzblLWQIy/GC6 qsCg== X-Gm-Message-State: AOUpUlH2KRGs+UeteqfJp6F/yt9McEHz5043YWKh62GzBTrlXzHzJhe1 1DyWY59B/uMHnOsht2E9ZMI= X-Google-Smtp-Source: AAOMgpfFlbicJGAZG5qAB+f+OyqC5Xg93tf55uEyqlkehutVSWirLnTQbyUpsNabDmqu7LhI3Xou5g== X-Received: by 2002:a1c:cc01:: with SMTP id h1-v6mr409791wmb.82.1532980881866; Mon, 30 Jul 2018 13:01:21 -0700 (PDT) Received: from flashbox ([2a01:4f8:10b:24a5::2]) by smtp.gmail.com with ESMTPSA id e137-v6sm699906wma.20.2018.07.30.13.01.20 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 30 Jul 2018 13:01:20 -0700 (PDT) Date: Mon, 30 Jul 2018 13:01:19 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Andrew Morton , Matthias Kaehlcke , ghackmann@android.com, Greg Hackmann , stable@vger.kernel.org, Kees Cook , Ingo Molnar , Greg KH , Josh Poimboeuf , Wei Wang , Masahiro Yamada , rdunlap@infradead.org, neilb@suse.com, LKML Subject: Re: [PATCH] kernel.h: Disable -Wreturn-stack-address for _THIS_IP_ Message-ID: <20180730200119.GA8599@flashbox> References: <20180730170622.99349-1-ndesaulniers@google.com> <20180730183943.GA9221@flashbox> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 30, 2018 at 12:48:06PM -0700, Nick Desaulniers wrote: > On Mon, Jul 30, 2018 at 11:39 AM Nathan Chancellor > wrote: > > > > On Mon, Jul 30, 2018 at 10:06:20AM -0700, Nick Desaulniers wrote: > > > Starting with Clang-7.0, _THIS_IP_ generates -Wreturn-stack-address > > > warnings for almost every translation unit. In general, I'd prefer to > > > leave this on (returning the address of a stack allocated variable is in > > > general a bad idea) and disable it only at whitelisted call sites. > > > > > > We can't do something like: > > > #pragma clang diagnostic push > > > #pragma clang diagnostic ignored "-Wreturn-stack-address" > > > > > > #pragma clang diagnostic pop > > > > > > in a GNU Statement Expression or macro, hence we use _Pragma, which is > > > its raison d'être: https://gcc.gnu.org/onlinedocs/cpp/Pragmas.html > > > > > > Cc: stable@vger.kernel.org # 4.17, 4.14, 4.9, 4.4 > > > Signed-off-by: Nick Desaulniers > > > --- > > > include/linux/kernel.h | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > > index 941dc0a5a877..5906f5727f90 100644 > > > --- a/include/linux/kernel.h > > > +++ b/include/linux/kernel.h > > > @@ -168,7 +168,15 @@ > > > > > > > > > #define _RET_IP_ (unsigned long)__builtin_return_address(0) > > > -#define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; }) > > > +#define _THIS_IP_ ( \ > > > +{ \ > > > + _Pragma("clang diagnostic push") \ > > > + _Pragma("clang diagnostic ignored \"-Wreturn-stack-address\"") \ > > > + __label__ __here; \ > > > +__here: (unsigned long)&&__here; \ > > > + _Pragma("clang diagnostic pop") \ > > > +} \ > > > +) > > > > > > #ifdef CONFIG_LBDAF > > > # include > > > -- > > > 2.18.0.233.g985f88cf7e-goog > > > > > > > This generates a ton of warnings with GCC: > > > > In file included from ./include/linux/spinlock.h:58, > > from ./include/linux/mmzone.h:8, > > from ./include/linux/gfp.h:6, > > from ./include/linux/slab.h:15, > > from ./include/linux/crypto.h:24, > > from arch/x86/kernel/asm-offsets.c:9: > > ./include/linux/bottom_half.h: In function ‘local_bh_disable’: > > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); > > > > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > ./include/linux/bottom_half.h:19: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > ./include/linux/bottom_half.h: In function ‘local_bh_enable’: > > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); > > > > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > ./include/linux/bottom_half.h:32: error: ignoring #pragma clang diagnostic [-Werror=unknown-pragmas] > > cc1: all warnings being treated as errors > > make[1]: *** [Kbuild:56: arch/x86/kernel/asm-offsets.s] Error 1 > > make: *** [Makefile:1081: prepare0] Error 2 > > Ah, good catch. I thought I had tested locally with gcc-8, but it > seems that it was likely only godbolt. I do see the errors locally > when building with gcc-8. > > > > > A proper solution is probably going to involve what was done for the > > -Wattribute-alias warnings from GCC 8 in commits 8793bb7f4a9d ("kbuild: > > add macro for controlling warnings to linux/compiler.h") and > > bee20031772a ("disable -Wattribute-alias warning for SYSCALL_DEFINEx()") > > > > I'll take a look at it in a bit unless someone beats me to it. > > I'll fix this up, triple check with gcc-8, and attribute you in the > Suggested-by tag. Thank you for verifying. > -- > Thanks, > ~Nick Desaulniers I forgot to mention there is a similar macro that will need this same fix in arch/arm64/include/asm/processor.h (current_text_addr), if you want to tackle it in v2. Do CC me on the next series so that I can test, thank you for doing this! Cheers, Nathan