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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 B38EFC04AAC for ; Mon, 6 May 2019 07:35:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 866282082F for ; Mon, 6 May 2019 07:35:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="HfCKA2Gc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726287AbfEFHe7 (ORCPT ); Mon, 6 May 2019 03:34:59 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:39799 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725710AbfEFHe7 (ORCPT ); Mon, 6 May 2019 03:34:59 -0400 Received: by mail-lj1-f195.google.com with SMTP id q10so10175447ljc.6 for ; Mon, 06 May 2019 00:34:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=ok4FiX0qqzxFXNlfPJQBxeAS7MtYAthIHs0pXM/1gsw=; b=HfCKA2GcWuIWfyCu6q7Vb4VuU5C85rltY95cYwAzVOuNpcOxt9Vpj8t6IWJzXJpM16 uc9PlW5f9Go3h/CJ9UsWwq1rdbfbTV7+cveeHt9cUsGuK9G3I7pEgW3Zv9bOFVDQOZbH MpdHFdCp7U0R6aqGNC2FBUx6AIBp++6riZnVE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ok4FiX0qqzxFXNlfPJQBxeAS7MtYAthIHs0pXM/1gsw=; b=s8AW9AAlOAsUAda3HdLWbgN0rPSSyw5jkTt6dcHkB8VnOIQGBZB/jqPER41gJ072hh +ZwvBsc4rsHSdtJbGZ3wYZJ2hiOoNih+wjUxX1BC9VOML4hhIddSxs5gGOivGuzQOMW2 vNTn3A+6IghMx3nMDw79aW18/5FPWHwTdP9LTMHXO+zoMhIzODszyPbW2Ea4Wq+kqQiZ dPCHCUyXcJrb6B/Pg9YBb68MoCGJA8rwB6eGroh8zX03uTDNXxCFuKugtVC9jqfE0ZWI S6OjHbRjXG9PmJpXrRj/8rwBM9JcWMKQnVKxi+ne7C1oS74qC3BN7A8aqcTXoyYbVnle gX1g== X-Gm-Message-State: APjAAAVKZFTDJ9lqPcf6LmH2x90Jra0PbVGFf96s7TQVC1u0QyNAB0Zd k8FVCKAD2Kf7cRs4clMHQXTn2Q== X-Google-Smtp-Source: APXvYqyIXcDanMudqDV0cbvEgmg2JswEqVaUi3W8CZa23fGsbc0VYTSqSxQKNyi+uTC2tZHBHGapWQ== X-Received: by 2002:a2e:9f07:: with SMTP id u7mr3713010ljk.115.1557128097278; Mon, 06 May 2019 00:34:57 -0700 (PDT) Received: from [172.16.11.26] ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id y25sm2083764ljh.31.2019.05.06.00.34.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 May 2019 00:34:56 -0700 (PDT) Subject: Re: [PATCH 00/10] implement DYNAMIC_DEBUG_RELATIVE_POINTERS To: Ingo Molnar Cc: Andrew Morton , Jason Baron , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, Michael Ellerman , Will Deacon , Ingo Molnar , Arnd Bergmann , Nathan Chancellor , Nick Desaulniers , Linus Torvalds , Andy Lutomirski References: <20190409212517.7321-1-linux@rasmusvillemoes.dk> <1afb0702-3cc5-ba4f-2bdd-604d9da2b846@rasmusvillemoes.dk> <20190506070544.GA66463@gmail.com> From: Rasmus Villemoes Message-ID: <25dfde77-fdad-0b99-75ec-4ba480058970@rasmusvillemoes.dk> Date: Mon, 6 May 2019 09:34:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190506070544.GA66463@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/05/2019 09.05, Ingo Molnar wrote: > > > It's sad to see such nice data footprint savings go the way of the dodo > just because GCC 4.8 is buggy. > > The current compatibility cut-off is GCC 4.6: > > GNU C 4.6 gcc --version > > Do we know where the GCC bug was fixed, was it in GCC 4.9? Not sure. The report was from a build on CentOS with gcc 4.8.5, so I tried installing the gcc-4.8 package on my Ubuntu machine and could reproduce. Then I tried installed gcc-4.9, and after disabling CONFIG_RETPOLINE (both CentOS and Ubuntu carry backported retpoline support in their 4.8, but apparently not 4.9), I could see that the problem was gone. But whether it's gone because it no longer elides an asm volatile() on a code path it otherwise emits code for, or because it simply doesn't emit the unused static inline() at all I don't know. I thought 0day also tested a range of supported compiler versions, so I was rather surprised at getting this report at all. But I suppose the arch/config matrix is already pretty huge. Anyway, the bug certainly doesn't exist in any of the gcc versions 0day does test. I _am_ bending the C rules a bit with the "extern some_var; asm volatile(".section some_section\nsome_var: blabla");". I should probably ask on the gcc list whether this way of defining a local symbol in inline assembly and referring to it from C is supposed to work, or it just happens to work by chance. Rasmus 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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 5D4DFC04AAC for ; Mon, 6 May 2019 07:36:31 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9DC8C2082F for ; Mon, 6 May 2019 07:36:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="HfCKA2Gc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9DC8C2082F Authentication-Results: mail.kernel.org; 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Mon, 06 May 2019 00:34:57 -0700 (PDT) Received: from [172.16.11.26] ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id y25sm2083764ljh.31.2019.05.06.00.34.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 May 2019 00:34:56 -0700 (PDT) Subject: Re: [PATCH 00/10] implement DYNAMIC_DEBUG_RELATIVE_POINTERS To: Ingo Molnar References: <20190409212517.7321-1-linux@rasmusvillemoes.dk> <1afb0702-3cc5-ba4f-2bdd-604d9da2b846@rasmusvillemoes.dk> <20190506070544.GA66463@gmail.com> From: Rasmus Villemoes Message-ID: <25dfde77-fdad-0b99-75ec-4ba480058970@rasmusvillemoes.dk> Date: Mon, 6 May 2019 09:34:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190506070544.GA66463@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nick Desaulniers , Arnd Bergmann , x86@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, Linus Torvalds , Jason Baron , Ingo Molnar , Andy Lutomirski , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Nathan Chancellor , linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 06/05/2019 09.05, Ingo Molnar wrote: > > > It's sad to see such nice data footprint savings go the way of the dodo > just because GCC 4.8 is buggy. > > The current compatibility cut-off is GCC 4.6: > > GNU C 4.6 gcc --version > > Do we know where the GCC bug was fixed, was it in GCC 4.9? Not sure. The report was from a build on CentOS with gcc 4.8.5, so I tried installing the gcc-4.8 package on my Ubuntu machine and could reproduce. Then I tried installed gcc-4.9, and after disabling CONFIG_RETPOLINE (both CentOS and Ubuntu carry backported retpoline support in their 4.8, but apparently not 4.9), I could see that the problem was gone. But whether it's gone because it no longer elides an asm volatile() on a code path it otherwise emits code for, or because it simply doesn't emit the unused static inline() at all I don't know. I thought 0day also tested a range of supported compiler versions, so I was rather surprised at getting this report at all. But I suppose the arch/config matrix is already pretty huge. Anyway, the bug certainly doesn't exist in any of the gcc versions 0day does test. I _am_ bending the C rules a bit with the "extern some_var; asm volatile(".section some_section\nsome_var: blabla");". I should probably ask on the gcc list whether this way of defining a local symbol in inline assembly and referring to it from C is supposed to work, or it just happens to work by chance. 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Mon, 06 May 2019 00:34:56 -0700 (PDT) Subject: Re: [PATCH 00/10] implement DYNAMIC_DEBUG_RELATIVE_POINTERS To: Ingo Molnar References: <20190409212517.7321-1-linux@rasmusvillemoes.dk> <1afb0702-3cc5-ba4f-2bdd-604d9da2b846@rasmusvillemoes.dk> <20190506070544.GA66463@gmail.com> From: Rasmus Villemoes Message-ID: <25dfde77-fdad-0b99-75ec-4ba480058970@rasmusvillemoes.dk> Date: Mon, 6 May 2019 09:34:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190506070544.GA66463@gmail.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190506_003459_580747_120397FF X-CRM114-Status: GOOD ( 19.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nick Desaulniers , Arnd Bergmann , Michael Ellerman , x86@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, Linus Torvalds , Jason Baron , Ingo Molnar , Andy Lutomirski , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Nathan Chancellor , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 06/05/2019 09.05, Ingo Molnar wrote: > > > It's sad to see such nice data footprint savings go the way of the dodo > just because GCC 4.8 is buggy. > > The current compatibility cut-off is GCC 4.6: > > GNU C 4.6 gcc --version > > Do we know where the GCC bug was fixed, was it in GCC 4.9? Not sure. The report was from a build on CentOS with gcc 4.8.5, so I tried installing the gcc-4.8 package on my Ubuntu machine and could reproduce. Then I tried installed gcc-4.9, and after disabling CONFIG_RETPOLINE (both CentOS and Ubuntu carry backported retpoline support in their 4.8, but apparently not 4.9), I could see that the problem was gone. But whether it's gone because it no longer elides an asm volatile() on a code path it otherwise emits code for, or because it simply doesn't emit the unused static inline() at all I don't know. I thought 0day also tested a range of supported compiler versions, so I was rather surprised at getting this report at all. But I suppose the arch/config matrix is already pretty huge. Anyway, the bug certainly doesn't exist in any of the gcc versions 0day does test. I _am_ bending the C rules a bit with the "extern some_var; asm volatile(".section some_section\nsome_var: blabla");". I should probably ask on the gcc list whether this way of defining a local symbol in inline assembly and referring to it from C is supposed to work, or it just happens to work by chance. Rasmus _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel