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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A41E7C4332F for ; Sun, 16 Oct 2022 18:20:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229951AbiJPSUt (ORCPT ); Sun, 16 Oct 2022 14:20:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229932AbiJPSUp (ORCPT ); Sun, 16 Oct 2022 14:20:45 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE5F431FB4; Sun, 16 Oct 2022 11:20:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 87F7CB80D30; Sun, 16 Oct 2022 18:20:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0E99C433D6; Sun, 16 Oct 2022 18:20:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665944441; bh=kYIbJXo/31uSnP5eLNjIeWmo0neUVyvUKN5LwSdHN1M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QqP7yXYKMCCxqQLWKrccSo84JsZ1yy7gfdJ9sBPViFC31AXIOlBZ4fcuYBzrGULoA +IlaJaWwWOXy1mVoVzQcPzHbHxMcSw/x13sGh3NEHsWiq/LrdDU6V2tRnTKGCXFFvM yrDz0yUqL8cRuZJu5SaoZiDmyPzVCDdTe0QINha4fN4NsvoZb6ar4cqUDey3bcVniM vlR7V2RwTH6klJf8vLItAgcqLid5Wk84HHV6VsBQE/MgLwtcJp4Lh784u6P0utlH7n Su32mLostVathZu2Q/NxMsvCSskG+5aWwB08KifPT+gck+dbzEOKBe58zO8adi+R9C ZFRRvgo9K5gFw== Date: Sun, 16 Oct 2022 19:20:36 +0100 From: Conor Dooley To: Sedat Dilek Cc: Masahiro Yamada , Nick Desaulniers , Nathan Chancellor , Andrew Morton , Tom Rix , Palmer Dabbelt , linux-kbuild@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, llvm@lists.linux.dev Subject: Re: [PATCH v2] lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5 Message-ID: References: <20221014204210.383380-1-nathan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 16, 2022 at 08:10:30PM +0200, Sedat Dilek wrote: > On Sun, Oct 16, 2022 at 8:04 PM Masahiro Yamada wrote: > > > > On Sat, Oct 15, 2022 at 6:52 AM Nick Desaulniers > > wrote: > > > > > > On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor wrote: > > > > > > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > > > and the GNU assembler, several instances of the following error appear: > > > > > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > > > > > > > Dumping the .s file reveals these .uleb128 directives come from > > > > .debug_loc and .debug_ranges: > > > > > > > > .Ldebug_loc0: > > > > .byte 4 # DW_LLE_offset_pair > > > > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > > > > .byte 1 # Loc expr size > > > > .byte 90 # DW_OP_reg10 > > > > .byte 0 # DW_LLE_end_of_list > > > > > > > > .Ldebug_ranges0: > > > > .byte 4 # DW_RLE_offset_pair > > > > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > > > > .byte 4 # DW_RLE_offset_pair > > > > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > > > > .byte 0 # DW_RLE_end_of_list > > > > > > > > There is an outstanding binutils issue to support a non-constant operand > > > > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > > > > be any movement on it, due to concerns over how it would work with > > > > linker relaxation. > > > > > > > > To avoid these build errors, prevent DWARF5 from being selected when > > > > using clang and an assembler that does not have support for these symbol > > > > deltas, which can be easily checked in Kconfig with as-instr plus the > > > > small test program from the dwz test suite from the binutils issue. > > > > > > > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > > > > Signed-off-by: Nathan Chancellor > > > > > > Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My > > > hope is the GNU binutils can relax their requirement for debug info > > > sections to improve support for DWARF v5. > > > > > > Reviewed-by: Nick Desaulniers > > > > > > Applied to linux-kbuild. > > Thanks. > > > > [1] says: > > "This looks good to me! Feel free to submit with a: > Tested-by: Conor Dooley " Hey Sedat, I actually didn't take a proper look at the v2 at all... I didn't realise that Nathan dropped by T-b for v2 since he'd changed the patch enough to feel that he should. I'm not too worried about the removed T-b (espcially since Linus has just merged Masahiro's PR containing this change). Thanks though! Conor. > > -sed@- > > [1] https://github.com/ClangBuiltLinux/linux/issues/1719#issuecomment-1261158627 > > > > > > > > > --- > > > > > > > > v2: > > > > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > > > > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > > > > tree. > > > > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > > > > is no point to applying this dependency to the integrated > > > > assembler because it will always pass. > > > > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > > > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > > > > aforementioned kbuild change. > > > > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > > > > configuration is now used in two places. > > > > - Drop Conor's tested by, as the patch is different enough to > > > > potentially require new testing. > > > > > > > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > > > > > > > lib/Kconfig.debug | 9 +++++++-- > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > > index db8d9271cabf..5c1c63575895 100644 > > > > --- a/lib/Kconfig.debug > > > > +++ b/lib/Kconfig.debug > > > > @@ -231,6 +231,11 @@ config DEBUG_INFO > > > > in the "Debug information" choice below, indicating that debug > > > > information will be generated for build targets. > > > > > > > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > > > > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > +config AS_HAS_NON_CONST_LEB128 > > > > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > > > > + > > > > choice > > > > prompt "Debug information" > > > > depends on DEBUG_KERNEL > > > > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > > > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > bool "Rely on the toolchain's implicit default DWARF version" > > > > select DEBUG_INFO > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > help > > > > The implicit default version of DWARF debug info produced by a > > > > toolchain changes over time. > > > > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > > > > config DEBUG_INFO_DWARF5 > > > > bool "Generate DWARF Version 5 debuginfo" > > > > select DEBUG_INFO > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > help > > > > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > > > > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > > > > > > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > > > > -- > > > > 2.38.0 > > > > > > > > > > > > > -- > > > Thanks, > > > ~Nick Desaulniers > > > > > > > > -- > > Best Regards > > Masahiro Yamada