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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6C0AC56202 for ; Fri, 13 Nov 2020 20:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6485522255 for ; Fri, 13 Nov 2020 20:52:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Vja5qVPN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726112AbgKMUwg (ORCPT ); Fri, 13 Nov 2020 15:52:36 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:40926 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726003AbgKMUwg (ORCPT ); Fri, 13 Nov 2020 15:52:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605300754; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=BjbZK0zeIm65whn17k5UcYS2uZ9Kdra7izOdoHD5fpw=; b=Vja5qVPNIORDTOqSTqSA1jcAlfT/9vrn5afRTuLTV2O+YzVDYdQDkZoL37/6A1pzb93pSt eb+daRvz6lU/tMbAKzxYhO8jb90f8eR6wDYa+ixONXQWp9/6C6CtIDgp0SGNW3th3CrTwM yiZn5KPlfqSCzNaHzf+p9LDCBY+kRcM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-302-6NjMwWGtNSa0dWipx0MBdw-1; Fri, 13 Nov 2020 15:52:30 -0500 X-MC-Unique: 6NjMwWGtNSa0dWipx0MBdw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3E7A28015A8; Fri, 13 Nov 2020 20:52:28 +0000 (UTC) Received: from treble (ovpn-117-69.rdu2.redhat.com [10.10.117.69]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6296B5B4A4; Fri, 13 Nov 2020 20:52:24 +0000 (UTC) Date: Fri, 13 Nov 2020 14:52:21 -0600 From: Josh Poimboeuf To: Sami Tolvanen Cc: Peter Zijlstra , Jann Horn , the arch/x86 maintainers , Masahiro Yamada , Steven Rostedt , Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , linux-kbuild , kernel list , linux-pci@vger.kernel.org Subject: Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps Message-ID: <20201113205221.jybsu3himgjqd3tq@treble> References: <20201021085606.GZ2628@hirez.programming.kicks-ass.net> <20201023173617.GA3021099@google.com> <20201110022924.tekltjo25wtrao7z@treble> <20201110174606.mp5m33lgqksks4mt@treble> <20201113195408.atbpjizijnhuinzy@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Nov 13, 2020 at 12:24:32PM -0800, Sami Tolvanen wrote: > On Fri, Nov 13, 2020 at 11:54 AM Josh Poimboeuf wrote: > > > > On Tue, Nov 10, 2020 at 10:59:55AM -0800, Sami Tolvanen wrote: > > > On Tue, Nov 10, 2020 at 9:46 AM Josh Poimboeuf wrote: > > > > > > > > On Mon, Nov 09, 2020 at 08:29:24PM -0600, Josh Poimboeuf wrote: > > > > > On Mon, Nov 09, 2020 at 03:11:41PM -0800, Sami Tolvanen wrote: > > > > > > CONFIG_XEN > > > > > > > > > > > > __switch_to_asm()+0x0: undefined stack state > > > > > > xen_hypercall_set_trap_table()+0x0: <=== (sym) > > > > > > > > With your branch + GCC 9 I can recreate all the warnings except this > > > > one. > > > > > > In a gcc build this warning is replaced with a different one: > > > > > > vmlinux.o: warning: objtool: __startup_secondary_64()+0x7: return with > > > modified stack frame > > > > > > This just seems to depend on which function is placed right after the > > > code in xen-head.S. With gcc, the disassembly looks like this: > > > > > > 0000000000000000 : > > > 0: e8 00 00 00 00 callq 5 > > > 1: R_X86_64_PLT32 cpu_bringup_and_idle-0x4 > > > 5: e9 f6 0f 00 00 jmpq 1000 > > > > > > ... > > > 0000000000001000 : > > > ... > > > ... > > > 0000000000002000 <__startup_secondary_64>: > > > > > > With Clang+LTO, we end up with __switch_to_asm here instead of > > > __startup_secondary_64. > > > > I still don't see this warning for some reason. > > Do you have CONFIG_XEN enabled? I can reproduce this on ToT master as follows: > > $ git rev-parse HEAD > 585e5b17b92dead8a3aca4e3c9876fbca5f7e0ba > $ make defconfig && \ > ./scripts/config -e HYPERVISOR_GUEST -e PARAVIRT -e XEN && \ > make olddefconfig && \ > make -j110 > ... > $ ./tools/objtool/objtool check -arfld vmlinux.o 2>&1 | grep secondary > vmlinux.o: warning: objtool: __startup_secondary_64()+0x2: return with > modified stack frame Ok, I see it now on Linus' tree. I just didn't see it on your clang-lto branch. -- Josh