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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 87455C4361B for ; Fri, 4 Dec 2020 01:19:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B164224D3 for ; Fri, 4 Dec 2020 01:19:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730185AbgLDBTa (ORCPT ); Thu, 3 Dec 2020 20:19:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729951AbgLDBTa (ORCPT ); Thu, 3 Dec 2020 20:19:30 -0500 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35233C061A52 for ; Thu, 3 Dec 2020 17:18:50 -0800 (PST) Received: by mail-pj1-x1043.google.com with SMTP id f14so2124010pju.4 for ; Thu, 03 Dec 2020 17:18:50 -0800 (PST) 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=yQuebzesxwMf25Xr/dPzPPrev+UQ6caZgGfIyyfOgUQ=; b=AdkoRN88dIF1YoC+j+aM1MY8e4XAHgHr6Qm5ePGGxeJct5eWZOVDW4q1D9C3LLa8zH RxD3jXqbRv5xVOt4NKZl2X85VY5mDaNFE137cL5vRPDT2YIwl3XP02aPJnOzuMiEfFCJ O2TNDBVmha6FCUh+WQdrQlptKhjeZpCVpH73ZXoybiTe/PlYuwNJCwp2VrH53850FJH2 515PbH93kp5tcNbwWioEzPCr6SkI3K2AM3MZJNXulV6TKLA75OeqUeP/IdZHXyGpg2cN mECH8bNGs2Ccbo/RE7qyO/wLu3aIg5949CJ/5j5iRyVF3VvBW8JViOTw7u21du6GrAF3 +3hw== 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=yQuebzesxwMf25Xr/dPzPPrev+UQ6caZgGfIyyfOgUQ=; b=ryZvJAFy3pZcdVUCym/vsoJOMHWvh1hnebIrS4mYDq2XKkbCfqQCFfhM9VbEdMclhv EvoluV0foh9PYSWjCf6vLw1DqgHkc+s1/fS4JTmALh02KxjgCUbtT326o2RDsU/fk+50 jImyfJFgNX3Q5PtTduVRjaPCjzlIa4mvKyhJn8d0D9YMoU4IrTOezpJjep/QvIm/2prd RRjyz7pFwCM73H37jhltbZW+tIw0ebvfGwkrQS6+pCgV4L4PEWPAEhpM/w1MRJpZ1O+5 +PpJWy2AJ95pA6FT3AlJvW4yvWsnX69hoiSOwnHYCaQVPmMjbYYjPf65P1AB1xvSrUqk XDwg== X-Gm-Message-State: AOAM531GShiKS8Co1busYL0aLxZH8Pc+/0Fq961SoaeqVGSQ9SsW+HZY K8ckYId89ZD8qTtiIl1wvWDjACDv5dwDLyU5CmGqmQ== X-Google-Smtp-Source: ABdhPJxAPcbI+OagIFgVil1xtoTesXiqZ4HHblGMTwSpODVAZ4Hx3JK5B4cAfBjOSJNFeeL+sVqWNXjR9yrFBsLuFe8= X-Received: by 2002:a17:90a:6fa1:: with SMTP id e30mr1854582pjk.32.1607044729507; Thu, 03 Dec 2020 17:18:49 -0800 (PST) MIME-Version: 1.0 References: <20201204011129.2493105-1-ndesaulniers@google.com> In-Reply-To: <20201204011129.2493105-1-ndesaulniers@google.com> From: Nick Desaulniers Date: Thu, 3 Dec 2020 17:18:37 -0800 Message-ID: Subject: Re: [PATCH v3 1/2] Kbuild: make DWARF version a choice To: Masahiro Yamada Cc: Arvind Sankar , Jakub Jelinek , Fangrui Song , Caroline Tice , clang-built-linux , Nick Clifton , Michal Marek , Andrew Morton , Randy Dunlap , "peterz@infradead.org" , Thomas Gleixner , Krzysztof Kozlowski , Linux Kbuild mailing list , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (minus Chengbin due to bounces) On Thu, Dec 3, 2020 at 5:11 PM Nick Desaulniers wrote: > > Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an > explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a > way that's forward compatible with existing configs, and makes adding > future versions more straightforward. > > Suggested-by: Fangrui Song > Suggested-by: Masahiro Yamada > Signed-off-by: Nick Desaulniers > --- > Makefile | 14 ++++++++------ > lib/Kconfig.debug | 21 ++++++++++++++++----- > 2 files changed, 24 insertions(+), 11 deletions(-) > > diff --git a/Makefile b/Makefile > index a2ded5029084..2430e1ee7c44 100644 > --- a/Makefile > +++ b/Makefile > @@ -826,12 +826,14 @@ else > DEBUG_CFLAGS += -g > endif > > -ifneq ($(LLVM_IAS),1) > -KBUILD_AFLAGS += -Wa,-gdwarf-2 > -endif > - > -ifdef CONFIG_DEBUG_INFO_DWARF4 > -DEBUG_CFLAGS += -gdwarf-4 > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2 > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 > +DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) > +ifneq ($(dwarf-version-y)$(LLVM_IAS),21) > +# Binutils 2.35+ required for -gdwarf-4+ support. > +dwarf-aflag := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y)) > +DEBUG_CFLAGS += $(dwarf-aflag) > +KBUILD_AFLAGS += $(dwarf-aflag) > endif > > ifdef CONFIG_DEBUG_INFO_REDUCED > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 0c7380e36370..04719294a7a3 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -256,14 +256,25 @@ config DEBUG_INFO_SPLIT > to know about the .dwo files and include them. > Incompatible with older versions of ccache. > > +choice > + prompt "DWARF version" > + help > + Which version of DWARF debug info to emit. > + > +config DEBUG_INFO_DWARF2 > + bool "Generate DWARF Version 2 debuginfo" > + help > + Generate DWARF v2 debug info. > + > config DEBUG_INFO_DWARF4 > - bool "Generate dwarf4 debuginfo" > + bool "Generate DWARF Version 4 debuginfo" > depends on $(cc-option,-gdwarf-4) > help > - Generate dwarf4 debug info. This requires recent versions > - of gcc and gdb. It makes the debug information larger. > - But it significantly improves the success of resolving > - variables in gdb on optimized code. > + Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+. > + It makes the debug information larger, but it significantly > + improves the success of resolving variables in gdb on optimized code. ^ I kept the previous help text, but while this may have been the case when DWARF v4 support was first introduced in GCC, by my (lone) measure of x86_64 defconfig with gcc 10.2, this doesn't or no longer seems to be the case. See patch 2 for measurements: https://lore.kernel.org/lkml/20201204011129.2493105-2-ndesaulniers@google.com/. (also, missed the cover letter, here it is: https://lore.kernel.org/lkml/CAKwvOdkZEiHK01OD420USb0j=F0LcrnRbauv9Yw26tu-GRbYkg@mail.gmail.com/) > + > +endchoice # "DWARF version" > > config DEBUG_INFO_BTF > bool "Generate BTF typeinfo" > -- > 2.29.2.576.ga3fc446d84-goog > -- Thanks, ~Nick Desaulniers