linux-kernel - Re: [PATCH 4/4] kbuild: dwarf: use AS_VERSION instead of test_dwarf5

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Message-ID: <20210304003055.tsrqewikdekbhhax@archlinux-ax161>
Date:   Wed, 3 Mar 2021 17:30:55 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] kbuild: dwarf: use AS_VERSION instead of
 test_dwarf5_support.sh

On Thu, Mar 04, 2021 at 03:33:33AM +0900, Masahiro Yamada wrote:
> The test code in scripts/test_dwarf5_support.sh is somewhat difficult
> to understand, but after all, we want to check binutils >= 2.35.2
> 
> >From the former discussion, the requrement for generating DRAWF v5 from
> C code is as follows:
> 
>  - gcc + binutils as     -> requires gcc 5.0+ (but 7.0+ for full support)
>  - clang + binutils as   -> requires binutils 2.35.2+
>  - clang + integrated as -> OK
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
> 
>  lib/Kconfig.debug              | 3 +--
>  scripts/test_dwarf5_support.sh | 8 --------
>  2 files changed, 1 insertion(+), 10 deletions(-)
>  delete mode 100755 scripts/test_dwarf5_support.sh
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 2779c29d9981..f3337a38925d 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -284,8 +284,7 @@ config DEBUG_INFO_DWARF4
>  
>  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))
> +	depends on GCC_VERSION >= 50000 || (CC_IS_CLANG && AS_IS_GNU && AS_VERSION >= 23502) || (CC_IS_CLANG && AS_IS_LLVM)
>  	depends on !DEBUG_INFO_BTF
>  	help
>  	  Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh
> deleted file mode 100755
> index c46e2456b47a..000000000000
> --- a/scripts/test_dwarf5_support.sh
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -#!/bin/sh
> -# SPDX-License-Identifier: GPL-2.0
> -
> -# Test that the assembler doesn't need -Wa,-gdwarf-5 when presented with DWARF
> -# v5 input, such as `.file 0` and `md5 0x00`. Should be fixed in GNU binutils
> -# 2.35.2. https://sourceware.org/bugzilla/show_bug.cgi?id=25611
> -echo '.file 0 "filename" md5 0x7a0b65214090b6693bd1dc24dd248245' | \
> -  $* -gdwarf-5 -Wno-unused-command-line-argument -c -x assembler -o /dev/null -
> -- 
> 2.27.0
>