From patchwork Fri Dec 4 01:11:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 11950283 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=-26.2 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, URIBL_BLOCKED,USER_AGENT_GIT,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 5F9E0C0018C for ; Fri, 4 Dec 2020 01:12:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A877224B8 for ; Fri, 4 Dec 2020 01:12:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728537AbgLDBM0 (ORCPT ); Thu, 3 Dec 2020 20:12:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbgLDBM0 (ORCPT ); Thu, 3 Dec 2020 20:12:26 -0500 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60314C061A54 for ; Thu, 3 Dec 2020 17:11:40 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id e11so3256793qvu.18 for ; Thu, 03 Dec 2020 17:11:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=pLRRzZdi/63YiDhRi+XJakRixQ1i8h1osfRwCQB8g5M=; b=VFGPrKi4ZBMvJ55xiMOEv09Xxz31ymosmHZRUn+Lpe1qlDPzSVpQ4Zf1nATfA6tPHk AeU2a1QCciqvolP55/LozsV/Xg9NQmHCvyYw3VVBh20xn82dwtNWIDBB2MfBWO6MrPIf WTgXvxZsTgv4BRElBsxbvlepXaUJMd+ff03353yWV2ReImCnaAwnTSeR9YS6DBV2jJwz /MEcOmIt/Hm6NYg87KjRcuGjhszCfqJyFG459lK6G5rSg4gZVQ2YJC5ULlExKBXSiNNS y1tnakTyZY+swmB5pjVBARPf5Hjsh4dwD4/7X/97+8FsrHM86ARgl48fCXiNTDyxUAWc Siwg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=pLRRzZdi/63YiDhRi+XJakRixQ1i8h1osfRwCQB8g5M=; b=QFem/XUHqjc+NTwxdR/f5eM/NISz17wMF54IzqIOZ0RulMjK+5FitXesVzCk683lQH fn/7/Ldv/gtnO/k/emOZU9bxaSe7kLnWWTh23/ep17QaoWJjq69VpLm+W5R8uuW4duD3 LNEnCJ8/D2IEzpAY/hocJ0AsHPhpmaYvEAk9stJJKP4D0DGh4QQF725qg7NPgARlnQFk gXMm/c+IT6sQCeGK7H28z70ZILhV1rM4iRgv4DkVcNSJG8CXBzTXEi+L8hldz9RAQNpO bD1KRHrfUQKrQA+cnGzB1HcQSycrCL9Vxjr8rCEg+WaTdJKARwWXvYlf63R3UEysX7sQ wP8A== X-Gm-Message-State: AOAM530rWK3XxMdqEd2TWXdU8CZ3xNPH1efmweM2uWj2iji7Y7MyKTEg ai9drK4kH1z9lHiytpnpN4+b/+cpHDRNGRuzETg= X-Google-Smtp-Source: ABdhPJyM0adl50ylGky8nCiNz//0uLGCwaPLuzxWr1v4ZsqecKm4FANzDm31yrpU+GcG9OM7gZ4oNhbHY8qfwByvDrU= Sender: "ndesaulniers via sendgmr" X-Received: from ndesaulniers1.mtv.corp.google.com ([2620:15c:211:202:f693:9fff:fef4:4d25]) (user=ndesaulniers job=sendgmr) by 2002:ad4:5106:: with SMTP id g6mr2373201qvp.1.1607044299523; Thu, 03 Dec 2020 17:11:39 -0800 (PST) Date: Thu, 3 Dec 2020 17:11:27 -0800 In-Reply-To: <20201204011129.2493105-1-ndesaulniers@google.com> Message-Id: <20201204011129.2493105-2-ndesaulniers@google.com> Mime-Version: 1.0 References: <20201204011129.2493105-1-ndesaulniers@google.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH v3 2/2] Kbuild: implement support for DWARF v5 From: Nick Desaulniers To: Masahiro Yamada Cc: Arvind Sankar , Jakub Jelinek , Fangrui Song , Caroline Tice , clang-built-linux@googlegroups.com, Nick Clifton , Nick Desaulniers , Michal Marek , Arnd Bergmann , Nathan Chancellor , Andrew Morton , Randy Dunlap , Changbin Du , "peterz@infradead.org" , Thomas Gleixner , Krzysztof Kozlowski , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org DWARF v5 is the latest standard of the DWARF debug info format. Feature detection of DWARF5 is onerous, especially given that we've removed $(AS), so we must query $(CC) for DWARF5 assembler directive support. GNU `as` only recently gained support for specifying -gdwarf-5. The DWARF version of a binary can be validated with: $ llvm-dwarfdump vmlinux | head -n 4 | grep version or $ readelf --debug-dump=info vmlinux 2>/dev/null | grep Version DWARF5 wins significantly in terms of size when mixed with compression (CONFIG_DEBUG_INFO_COMPRESSED). 363M vmlinux.clang12.dwarf5.compressed 434M vmlinux.clang12.dwarf4.compressed 439M vmlinux.clang12.dwarf2.compressed 457M vmlinux.clang12.dwarf5 536M vmlinux.clang12.dwarf4 548M vmlinux.clang12.dwarf2 515M vmlinux.gcc10.2.dwarf5.compressed 599M vmlinux.gcc10.2.dwarf4.compressed 624M vmlinux.gcc10.2.dwarf2.compressed 630M vmlinux.gcc10.2.dwarf5 765M vmlinux.gcc10.2.dwarf4 809M vmlinux.gcc10.2.dwarf2 Though the quality of debug info is harder to quantify; size is not a proxy for quality. Jakub notes: All [GCC] 5.1 - 6.x did was start accepting -gdwarf-5 as experimental option that enabled some small DWARF subset (initially only a few DW_LANG_* codes newly added to DWARF5 drafts). Only GCC 7 (released after DWARF 5 has been finalized) started emitting DWARF5 section headers and got most of the DWARF5 changes in... Version check GCC so that we don't need to worry about the difference in command line args between GNU readelf and llvm-readelf/llvm-dwarfdump to validate the DWARF Version in the assembler feature detection script. Link: http://www.dwarfstd.org/doc/DWARF5.pdf Suggested-by: Arvind Sankar Suggested-by: Jakub Jelinek Suggested-by: Masahiro Yamada Suggested-by: Fangrui Song Suggested-by: Caroline Tice Signed-off-by: Nick Desaulniers Reviewed-by: Nathan Chancellor --- Makefile | 1 + include/asm-generic/vmlinux.lds.h | 6 +++++- lib/Kconfig.debug | 14 ++++++++++++++ scripts/test_dwarf5_support.sh | 9 +++++++++ 4 files changed, 29 insertions(+), 1 deletion(-) create mode 100755 scripts/test_dwarf5_support.sh diff --git a/Makefile b/Makefile index 2430e1ee7c44..45231f6c1935 100644 --- a/Makefile +++ b/Makefile @@ -828,6 +828,7 @@ endif dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2 dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5 DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) ifneq ($(dwarf-version-y)$(LLVM_IAS),21) # Binutils 2.35+ required for -gdwarf-4+ support. diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index b2b3d81b1535..76ce62c77029 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -829,7 +829,11 @@ .debug_types 0 : { *(.debug_types) } \ /* DWARF 5 */ \ .debug_macro 0 : { *(.debug_macro) } \ - .debug_addr 0 : { *(.debug_addr) } + .debug_addr 0 : { *(.debug_addr) } \ + .debug_line_str 0 : { *(.debug_line_str) } \ + .debug_loclists 0 : { *(.debug_loclists) } \ + .debug_rnglists 0 : { *(.debug_rnglists) } \ + .debug_str_offsets 0 : { *(.debug_str_offsets) } /* Stabs debugging sections. */ #define STABS_DEBUG \ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 04719294a7a3..987815771ad6 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -274,6 +274,20 @@ config DEBUG_INFO_DWARF4 It makes the debug information larger, but it significantly improves the success of resolving variables in gdb on optimized code. +config DEBUG_INFO_DWARF5 + bool "Generate DWARF Version 5 debuginfo" + depends on GCC_VERSION >= 70000 || CC_IS_CLANG + depends on $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS)) + help + Generate DWARF v5 debug info. Requires binutils 2.35, gcc 7.0+, and + gdb 8.0+. Changes to the structure of debug info in Version 5 allow + for around 15-18% savings in resulting image and debug info section sizes + as compared to DWARF Version 4. DWARF Version 5 standardizes previous + extensions such as accelerators for symbol indexing and the format for + fission (.dwo/.dwp) files. Users may not want to select this config if + they rely on tooling that has not yet been updated to support + DWARF Version 5. + endchoice # "DWARF version" config DEBUG_INFO_BTF diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh new file mode 100755 index 000000000000..156ad5ec4274 --- /dev/null +++ b/scripts/test_dwarf5_support.sh @@ -0,0 +1,9 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +# Test that assembler accepts -gdwarf-5 and .file 0 directives, which were bugs +# in binutils < 2.35. +# https://sourceware.org/bugzilla/show_bug.cgi?id=25612 +# https://sourceware.org/bugzilla/show_bug.cgi?id=25614 +set -e +echo '.file 0 "filename"' | $* -Wa,-gdwarf-5 -c -x assembler -o /dev/null -