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=-14.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 DED3DC56202 for ; Fri, 13 Nov 2020 20:24:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 828E220825 for ; Fri, 13 Nov 2020 20:24:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SBgav/T3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726112AbgKMUYq (ORCPT ); Fri, 13 Nov 2020 15:24:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725981AbgKMUYp (ORCPT ); Fri, 13 Nov 2020 15:24:45 -0500 Received: from mail-ua1-x941.google.com (mail-ua1-x941.google.com [IPv6:2607:f8b0:4864:20::941]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 940BFC0613D1 for ; Fri, 13 Nov 2020 12:24:45 -0800 (PST) Received: by mail-ua1-x941.google.com with SMTP id w3so3413007uau.2 for ; Fri, 13 Nov 2020 12:24:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mU6UeGOfRQMRJwnHmGX5EKrd3fAZtibGBHai3RFBnJQ=; b=SBgav/T3VzzEtf+XcGk0y2urSrYRSMZdZ/BSprOQYF07imi1ADQ6+bP8NVgkFIS13j c29etEZPIosU9Ccq+aDvjNmW4gtV+RXjaLR5/iYKTteik7fkjmDnPZ3rLCzlNv2EYSEP /f9Rq5iUQR0o7S1G9L2SZCAv7mAGSkXEUI5hN3rLrtsdHgPlxnpAG0v3MFSAKPbkQrae WLoVYBLPEP79v4Y7OA8gXbcs08GtIihODPoDAmO+6mtoQqiccreuY2GcpYzaDeYkNLlF n1WMuVFyGng50eB9Mmqa/6aQz5eygw2tOZp8M/jD01KJFVb5k1ymIpwXFEcj8xVZxzyy nZxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mU6UeGOfRQMRJwnHmGX5EKrd3fAZtibGBHai3RFBnJQ=; b=Em9/J5Sfvv+w8OAO+vLLwPzJM1EbdGYAediww/ZR7soqCRIZ72itdyEGoWcRqIYz0q DECBxkn6sz9L8CpmdjIIL8WWR9YwJ1OIUhc0SoLn4U5fexJ8bfY4fLfUJVLJUhKm02RZ AB+TyQEejdzXUS+RT3RSCBJ4LYO0MhG7+jImZnQIVDLkJmsFd2rDpVZ2Md+ACjWOnt5j GFIGVOCq2s0OgQlsEMHe/cxh6Oje4dxbKu7qwUReF8PiUtXLBvrwy4LD91VZT4HTEDie 9zXWjKSI2lhidVFHPAUGuI4D1V1olBb7O6vxMIlp3LiHLJGPPBftGVQwr+DhfAA5yqMg LbpA== X-Gm-Message-State: AOAM533c22J4EVXRaH276niveL4vF3oHDH7XXwoQetS+3N0BSeVfjN+G XbCvIichE3WYhOER0PDJ4vuNKPYOcQsODTA9b6AocA== X-Google-Smtp-Source: ABdhPJxQo6DF9jUnA2YJFoBq8ll7fJYetoimM/TRDoFpxZhBeNyAnbeYafJONZ4hmtReCz/v9xa11p0ayWmu2zwdpXo= X-Received: by 2002:ab0:6156:: with SMTP id w22mr2653091uan.122.1605299084290; Fri, 13 Nov 2020 12:24:44 -0800 (PST) MIME-Version: 1.0 References: <20201020185217.ilg6w5l7ujau2246@treble> <20201021085606.GZ2628@hirez.programming.kicks-ass.net> <20201023173617.GA3021099@google.com> <20201110022924.tekltjo25wtrao7z@treble> <20201110174606.mp5m33lgqksks4mt@treble> <20201113195408.atbpjizijnhuinzy@treble> In-Reply-To: <20201113195408.atbpjizijnhuinzy@treble> From: Sami Tolvanen Date: Fri, 13 Nov 2020 12:24:32 -0800 Message-ID: Subject: Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps To: Josh Poimboeuf 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org 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 > Is it fixed by adding cpu_bringup_and_idle() to global_noreturns[] in > tools/objtool/check.c? No, that didn't fix the warning. Here's what I tested: diff --git a/tools/objtool/check.c b/tools/objtool/check.c index c6ab44543c92..f1f65f5688cf 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -156,6 +156,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "machine_real_restart", "rewind_stack_do_exit", "kunit_try_catch_throw", + "cpu_bringup_and_idle", }; if (!func) Sami