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 70C83C433EF for ; Wed, 13 Jul 2022 16:13:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236946AbiGMQNj (ORCPT ); Wed, 13 Jul 2022 12:13:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236481AbiGMQNd (ORCPT ); Wed, 13 Jul 2022 12:13:33 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56FD6C67 for ; Wed, 13 Jul 2022 09:13:32 -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 dfw.source.kernel.org (Postfix) with ESMTPS id EAAB461AAD for ; Wed, 13 Jul 2022 16:13:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3510C34114; Wed, 13 Jul 2022 16:13:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657728811; bh=nOM4PVCC020ledRm9uERtcgcfEe1oMeE0QVyxwM6nLU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ahgE4NZa37YIUA6qhBVA8Sqm9HrocDWU4eE/EQKrsdV5EvNxgkqoSo2sVLZQBPaC+ wuqOgDt+8f896BEMELWAtTT3TJoskus6uNR2Np8YuItzHuvy1S1sfGveAJXSdDJU6R 0I5JAiht7C2vjFFqHOs8iaGzQrB5N3K1RburnW09+nwdHbu64vzyo3n7B86Fut6Wt2 +3o4v1pc47JHB362Zze7rWHaeBH6sjG5QwpQGVyV5BL5ALyE4wm8yx96eS6WmvFeKE eL5vsowMmfsd4HEXXVPhXcGK2FLm9tH1OvLTmvef8gZcPHMvsWjyksMGrLIh0JXJRR CJc+IP8urYG+A== Date: Wed, 13 Jul 2022 09:13:29 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Josh Poimboeuf , Peter Zijlstra , linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: objtool "'naked' return found in RETHUNK build" with clang + CONFIG_K{A,C}SAN=y Message-ID: References: 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 Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote: > On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor wrote: > > > > Hi Josh and Peter, > > > > After commit 9bb2ec608a20 ("objtool: Update Retpoline validation") and > > commit f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs"), I > > see a spew of objtool warnings when building certain configurations with > > clang. Examples below, they appear to trigger in every single file. > > > > With x86_64_defconfig + CONFIG_KASAN=y: > > > > arch/x86/ia32/audit.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build > > arch/x86/ia32/audit.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build > > init/version.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build > > init/version.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build > > arch/x86/kernel/cpu/rdrand.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build > > arch/x86/kernel/cpu/rdrand.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build > > arch/x86/kernel/fpu/bugs.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build > > arch/x86/kernel/fpu/bugs.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build > > arch/x86/kernel/platform-quirks.o: warning: objtool: asan.module_ctor+0x0: 'naked' return found in RETHUNK build > > init/calibrate.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build > > init/calibrate.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build > > > > With x86_64_defconfig + CONFIG_KCSAN=y: > > > > arch/x86/ia32/audit.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > init/calibrate.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > init/version.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > arch/x86/kernel/fpu/bugs.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > arch/x86/kernel/cpu/rdrand.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > arch/x86/events/probe.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > arch/x86/kernel/apic/ipi.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build > > Thanks for the report. I wonder if this might be a compiler bug; it > seems like the {a|t}san.module_{c|d}tor functions are being emitted > with ret instructions? > > If you have one of these builds lying around still, can you provide: > > $ llvm-objdump -dr --disassemble-symbols=tsan.module_ctor > arch/x86/kernel/fpu/bugs.o Sure thing. With KASAN: $ llvm-objdump -r --disassemble-symbols=asan.module_ctor,asan.module_dtor build/arch/x86/kernel/fpu/bugs.o build/arch/x86/kernel/fpu/bugs.o: file format elf64-x86-64 Disassembly of section .text.asan.module_ctor: 0000000000000000 : 0: be 01 00 00 00 movl $1, %esi 5: 48 c7 c7 00 00 00 00 movq $0, %rdi 0000000000000008: R_X86_64_32S .data c: e8 00 00 00 00 callq 0x11 000000000000000d: R_X86_64_PLT32 __asan_register_globals-0x4 11: c3 retq Disassembly of section .text.asan.module_dtor: 0000000000000000 : 0: be 01 00 00 00 movl $1, %esi 5: 48 c7 c7 00 00 00 00 movq $0, %rdi 0000000000000008: R_X86_64_32S .data c: e8 00 00 00 00 callq 0x11 000000000000000d: R_X86_64_PLT32 __asan_unregister_globals-0x4 11: c3 retq With KCSAN: $ llvm-objdump -r --disassemble-symbols=tsan.module_ctor build/arch/x86/kernel/fpu/bugs.o build/arch/x86/kernel/fpu/bugs.o: file format elf64-x86-64 Disassembly of section .text.tsan.module_ctor: 0000000000000000 : 0: e8 00 00 00 00 callq 0x5 0000000000000001: R_X86_64_PLT32 __tsan_init-0x4 5: c3 retq Cheers, Nathan