From nobody Tue May 21 15:23:10 2024 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 8691EC433FE for ; Fri, 14 Oct 2022 20:48:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231573AbiJNUsW (ORCPT ); Fri, 14 Oct 2022 16:48:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231526AbiJNUsS (ORCPT ); Fri, 14 Oct 2022 16:48:18 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E39481ACABB; Fri, 14 Oct 2022 13:48:15 -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 74554B82421; Fri, 14 Oct 2022 20:48:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60012C433D7; Fri, 14 Oct 2022 20:48:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665780493; bh=C3fOH2Mc8DRWmLYpWhPGyuj4dAcW5kYVpSBvOUxOFQc=; h=From:To:Cc:Subject:Date:From; b=pJdQ+TDxYwMeWzyEJyOKQ5BBV7ferow6GiaZchv9FWLdvRFrEENkmGWbNI5VhI9bZ QLEBqI3IDlO1DXZiVCzavpUqsRVOpOUJ4xN7SYmSBjY2vKx1N6wRTFZpeCKCpt3QWM MS9lRqcCaFCLrPizqRwI/wM+FNAJM+G8tpYP0AB4V8roJSuVicX095kjfB1qLmYIrM f0VMKqzxb90LlGeTyyckFIwNSqUSNrizHWqiJAve0tygFODyI0vZGfzgRUvaxeqDla lk/i63GdyfprtGwB8flJkDu7+uKY/v3bMn3c3jpHZFiLZ44xURS2ryrya4R2kpvhiP OgjlJzPY9Sp+Q== From: Nathan Chancellor To: Andrew Morton , Masahiro Yamada Cc: Nick Desaulniers , Tom Rix , Palmer Dabbelt , Conor Dooley , linux-kbuild@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, llvm@lists.linux.dev, Nathan Chancellor Subject: [PATCH v2] lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5 Date: Fri, 14 Oct 2022 13:42:11 -0700 Message-Id: <20221014204210.383380-1-nathan@kernel.org> X-Mailer: git-send-email 2.38.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 sup= ported 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=3D27215 Link: https://github.com/ClangBuiltLinux/linux/issues/1719 Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Tested-by: Conor Dooley " --- 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. =20 +# 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.c= gi?id=3D27215 +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 >=3D 23502) + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS= _GNU && AS_VERSION >=3D 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 >=3D 23= 502) + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >=3D 23= 502 && 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 --=20 2.38.0