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 E7CD7C43334 for ; Wed, 13 Jul 2022 16:25:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237188AbiGMQZ4 (ORCPT ); Wed, 13 Jul 2022 12:25:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237176AbiGMQZt (ORCPT ); Wed, 13 Jul 2022 12:25:49 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F10CD2DE9 for ; Wed, 13 Jul 2022 09:25:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=832nvkZXqaW1Rdvm3esdQt5krPHyQbIa8+WuQyv+HXM=; b=dph457u6XiKxidXKO4sosmAwGu xPbibBbBM32DDiTYhs2OoY3zXXQPjdF9K6VsNUkq0Htv48uhqv9cZ8QQUGrex+vRrcTJfcl2YxNsM PHcq3fRdG22401ROx3f9N4yPVz/h2tW+uuQyU3nqaeh9UBiL3jxDvt6MxpAR2WqM921kT9adnjvYw tfFGPWo8D4PM8zZwbQM+BM0CfXMaSSeabOAMVgGh2KQtRLgt85oGDDgQrw7M+GubmMDtU7+0SRIKC 3kFApEdn7uproQKEn0RBpUN/65qsg/DtI+jNCyxXOxkjTS6VjlVD9IFyMZPnr/n6Gn4lZMX0gQrXV t2OpBEng==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oBfBG-008OTG-9T; Wed, 13 Jul 2022 16:25:42 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E40E930041D; Wed, 13 Jul 2022 18:25:41 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id CDF2220D74F04; Wed, 13 Jul 2022 18:25:41 +0200 (CEST) Date: Wed, 13 Jul 2022 18:25:41 +0200 From: Peter Zijlstra To: Nathan Chancellor Cc: Nick Desaulniers , Josh Poimboeuf , 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 09:13:29AM -0700, Nathan Chancellor wrote: > 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 As Nick said; this should be: 'jmp __x86_return_thunk', on those builds.