From patchwork Wed Jan 13 00:32:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 12015517 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=-26.3 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, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 413F3C4332D for ; Wed, 13 Jan 2021 00:50:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E6682333C for ; Wed, 13 Jan 2021 00:50:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392403AbhAMAnC (ORCPT ); Tue, 12 Jan 2021 19:43:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392440AbhAMAeJ (ORCPT ); Tue, 12 Jan 2021 19:34:09 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E85B8C0617A7 for ; Tue, 12 Jan 2021 16:32:53 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id e137so565925ybf.16 for ; Tue, 12 Jan 2021 16:32:53 -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=zQ4L+JyR4fS6Zw/UsbG4Lq16kk6cB+cu31P+ux/3yCo=; b=ql7lCCLN0Vi4dQcb6GQ6Qrp5gTZNlhpyTebxqOI9UPcv53OutigfkcnE+PEXkZXn5t xhUjovlh1+RY36gsZTtiFOolMjGJwV7ckXkY62kXNdpn59bgDYtNAiC6U1EDkJo2dLc7 1xWLksinunOBKoChx2szDVln2wIdtYG51o+9WXW2cCg6y2IjKMjI0Vj99zjNEXYliMa2 vUEzOukvGHC4qCaRlZ20gw8JmY9WaY8I2/fhZXxviUj+dBzj2484i5x6R3FvAGrXAPYt SM0trZBcHZq9yeF/SsFdPJy5D2t3bW5b+GUdbHS/7/Un9y8x89LyY6qsoWuIJjIIsWPK xg4Q== 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=zQ4L+JyR4fS6Zw/UsbG4Lq16kk6cB+cu31P+ux/3yCo=; b=YOkwE0JgwOMK36Z8/P8SvUJC5RB8e4WV57PCWH9L6mpaZp3HTgXYhpJ+vMJX4bUsC0 /x82UFx1tiYbwy263eAakgYfRoQ+nr2qnFRR0bJ4Z8b8qMb/lVxrmoGXItJmtFOK7tjr kQve897ykV+6XfEJ2DVMfBHQ72r7jMijP7xh7Pjw4R1mWq0syFXoM66FOi+kuaVqzscG wfdjVFJ9Se6rHLQqs6YzG5MQ72wJE1DTCUdX7b6bXPVKKJDi34EFjDBZBLGUwAZfdxRR vBtVjfT7kkyCKCHeJvnpOsfPoEGaVAmhkm/vLfTNsFzxxkXvlkslzPHgStqO7ykrnqfn covA== X-Gm-Message-State: AOAM533EDsnplgcArw1xUXYNF8nlNeFmhl/T/qD1CWhn7lmjS/8Csopt ukIWFM22W0bKNpEKnNyxgxrtS1gtrEzRMaTgmI0= X-Google-Smtp-Source: ABdhPJzoumFmS+f0N4/EEA9rkIp1PJMKNYQ3GTLb8hXE1dg30o5aG4Xe6GonfUs5Mq4O//EAy0Rrxc4Fw5WMimqEUMA= 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:a05:6902:6b1:: with SMTP id j17mr3137592ybt.438.1610497973189; Tue, 12 Jan 2021 16:32:53 -0800 (PST) Date: Tue, 12 Jan 2021 16:32:35 -0800 In-Reply-To: <20210113003235.716547-1-ndesaulniers@google.com> Message-Id: <20210113003235.716547-4-ndesaulniers@google.com> Mime-Version: 1.0 References: <20210113003235.716547-1-ndesaulniers@google.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH v4 3/3] Kbuild: implement support for DWARF v5 From: Nick Desaulniers To: Masahiro Yamada Cc: Nathan Chancellor , Andrew Morton , Sedat Dilek , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org, Jakub Jelinek , Fangrui Song , Caroline Tice , Nick Clifton , Nick Desaulniers , Arvind Sankar 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 | 17 +++++++++++++++++ scripts/test_dwarf5_support.sh | 9 +++++++++ 4 files changed, 32 insertions(+), 1 deletion(-) create mode 100755 scripts/test_dwarf5_support.sh diff --git a/Makefile b/Makefile index 656fff17b331..1067cfd98249 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 49944f00d2b3..37dc4110875e 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -843,7 +843,11 @@ .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 e80770fac4f0..60a4f5e27ada 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -273,6 +273,23 @@ 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 >= 50000 || CC_IS_CLANG + depends on CC_IS_GCC || $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS)) + help + Generate DWARF v5 debug info. Requires binutils 2.35, gcc 5.0+ (gcc + 5.0+ accepts the -gdwarf-5 flag but only had partial support for some + draft features until 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..142a1b5c7fa2 --- /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"' | $* -gdwarf-5 -Wa,-gdwarf-5 -c -x assembler -o /dev/null -