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=-13.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 0A283C3A59F for ; Thu, 29 Aug 2019 19:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C3DC82189D for ; Thu, 29 Aug 2019 19:34:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="om9rfD3r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728158AbfH2Teh (ORCPT ); Thu, 29 Aug 2019 15:34:37 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:41158 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726512AbfH2Teh (ORCPT ); Thu, 29 Aug 2019 15:34:37 -0400 Received: by mail-wr1-f66.google.com with SMTP id j16so4592120wrr.8 for ; Thu, 29 Aug 2019 12:34:35 -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:in-reply-to:user-agent; bh=wITCcu1aUHRsjm7ofKS0hPTgotk+bgOxAXtcBSapAng=; b=om9rfD3r3tWjux8nXOwoZHcvldgVv/88BLWEtjKKzNKRH0tOOMfrrvA1v/uSesZqAu F7xX0euXGljeMqlw8nAb87SdY/wz+KlGjAGstx1Cuqawl7/7sq7xH+/aKl4IulH2TYZl SZRq839nEKBvwW+Hy2x+q93UiBGv3oCw7wAYKPtqIFzrQkz3jOtwmtk+7CTPsHl+c3pD e7LBTdEZn/u5wHLMtVvJ+rGnjH3T0s5DFj2WTmk3UK2yKgaR0r9tMr1GeJzJ/kXzMbhF vqCqisP/AY91nhTO7uYN2DG8DSJ5v+qlaYmIDocQZtGuG+lYs+VNS5phXDxwA1Ug/OyA sACA== 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:in-reply-to:user-agent; bh=wITCcu1aUHRsjm7ofKS0hPTgotk+bgOxAXtcBSapAng=; b=mfvddlpnI8ze2BP8Uudap2Mjj2iUCGVp1Pa6ZRhJyVKLf7VnBTUvIMqbrdVt2sB5Aj Y2XlgZUg+gibBuEpSN4Hq6acSeT6RLEpPX/Rs5i+YruIFYi26ru0DBDeHrrINUKzPll2 ru1P5AbvAb0p2XgEVI2N+kC5zjoOPUW43r5OuM8B2naPKRwds+0vNMrCzirbKUPxWfTU 4N2rf0AoubywEio2TYGrgTOIivzkaIzesCs4S/i526IKr9qAH7Oyv24kzvzHM1NTK5iq RJdvyzZ1AoVBr+1EbC6T6y9D9WannFwWQQU6ZqbMpUOrXM/Ai/QMAKPu2fg9h+UWAFEi 60qA== X-Gm-Message-State: APjAAAXfREKHnvjBY+xJ7YgEgqt2hzX922O2EozhV8zWnoC77xKpSNZF uWdWNUy2cs92sSRypH0eQtw= X-Google-Smtp-Source: APXvYqwfC0hwHaNvtKcJP+AMQFx3UwJll3qWxANro4klHhx9Oo9LuQbO5ZMREVBc1sxJESACW/y4cg== X-Received: by 2002:adf:e7c4:: with SMTP id e4mr10775791wrn.62.1567107274840; Thu, 29 Aug 2019 12:34:34 -0700 (PDT) Received: from archlinux-threadripper ([2a01:4f8:222:2f1b::2]) by smtp.gmail.com with ESMTPSA id c201sm7320983wmd.33.2019.08.29.12.34.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2019 12:34:34 -0700 (PDT) Date: Thu, 29 Aug 2019 12:34:32 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Russell King , Arnd Bergmann , Stefan Agner , Matthias Kaehlcke , Linux ARM , LKML , clang-built-linux Subject: Re: [PATCH] ARM: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer Message-ID: <20190829193432.GA10138@archlinux-threadripper> References: <20190829062635.45609-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 29, 2019 at 10:55:28AM -0700, Nick Desaulniers wrote: > On Wed, Aug 28, 2019 at 11:27 PM Nathan Chancellor > wrote: > > > > Currently, multi_v7_defconfig + CONFIG_FUNCTION_TRACER fails to build > > with clang: > > > > arm-linux-gnueabi-ld: kernel/softirq.o: in function `_local_bh_enable': > > softirq.c:(.text+0x504): undefined reference to `mcount' > > arm-linux-gnueabi-ld: kernel/softirq.o: in function `__local_bh_enable_ip': > > softirq.c:(.text+0x58c): undefined reference to `mcount' > > arm-linux-gnueabi-ld: kernel/softirq.o: in function `do_softirq': > > softirq.c:(.text+0x6c8): undefined reference to `mcount' > > arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_enter': > > softirq.c:(.text+0x75c): undefined reference to `mcount' > > arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_exit': > > softirq.c:(.text+0x840): undefined reference to `mcount' > > arm-linux-gnueabi-ld: kernel/softirq.o:softirq.c:(.text+0xa50): more undefined references to `mcount' follow > > > > clang can emit a working mcount symbol, __gnu_mcount_nc, when > > '-meabi gnu' is passed to it. Until r369147 in LLVM, this was > > broken and caused the kernel not to boot because the calling > > convention was not correct. Now that it is fixed, add this to > > the command line when clang is 10.0.0 or newer so everything > > works properly. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/35 > > Link: https://bugs.llvm.org/show_bug.cgi?id=33845 > > Link: https://github.com/llvm/llvm-project/commit/16fa8b09702378bacfa3d07081afe6b353b99e60 > > Signed-off-by: Nathan Chancellor > > --- > > arch/arm/Makefile | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > > index c3624ca6c0bc..7b5a26a866fc 100644 > > --- a/arch/arm/Makefile > > +++ b/arch/arm/Makefile > > @@ -112,6 +112,12 @@ ifeq ($(CONFIG_ARM_UNWIND),y) > > CFLAGS_ABI +=-funwind-tables > > endif > > > > +ifeq ($(CONFIG_CC_IS_CLANG),y) > > +ifeq ($(shell test $(CONFIG_CLANG_VERSION) -ge 100000; echo $$?),0) > > +CFLAGS_ABI +=-meabi gnu > > +endif > > +endif > > + > > Thanks for the patch! I think this is one of the final issues w/ 32b > ARM configs when building w/ Clang. > > I'm not super enthused about the version check. The flag is indeed > not recognized by GCC, but I think it would actually be more concise > with $(cc-option) and no compiler or version check. > > Further, I think that the working __gnu_mcount_nc in Clang would > better be represented as marking the arch/arm/KConfig option for > CONFIG_FUNCTION_TRACER for dependent on a version of Clang greater > than or equal to Clang 10, not conditionally adding this flag. (We > should always add the flag when supported, IMO. __gnu_mcount_nc's > calling convention being broken is orthogonal to the choice of > __gnu_mcount_nc vs mcount, and it's the former's that should be > checked, not the latter as in this patch. I will test with or without CONFIG_AEABI like Matthias asked and I will implement your Kconfig suggestion if it passes all of my tests. The reason that I did it this way is because I didn't want a user to end up with a non-booting kernel since -meabi gnu works with older versions of clang at build time, the issue happens at boot time but the Kconfig suggestion + cc-option should fix that. I should have a v2 out this evening. Cheers, Nathan