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=-7.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS autolearn=ham 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 6B78BC070C3 for ; Mon, 15 Oct 2018 03:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1916F2086A for ; Mon, 15 Oct 2018 03:43:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0BIArQ4c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1916F2086A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726566AbeJOL0x (ORCPT ); Mon, 15 Oct 2018 07:26:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:49116 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726262AbeJOL0w (ORCPT ); Mon, 15 Oct 2018 07:26:52 -0400 Received: from mail-wm1-f51.google.com (mail-wm1-f51.google.com [209.85.128.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 476B320895 for ; Mon, 15 Oct 2018 03:43:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539575011; bh=eXlhtT/0yW/EpHseOYQMo5PoWvMH6BDErrGmYMeqKKA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=0BIArQ4ccTwJRjHQCGOWdIKWxT2gX3B330dbRrVyIBvNEsKK5gVmp4hKt/ppwGwe8 MDpqrSM/u04FkOP5Wpfx2jpEsKoI9UpKlTp93zJ8NSb5C9aMXi0km+/kmUWvTjAj5o 7E43YbF0+a1MBbexbsS2grNu9yg9DoHV82mmcvnc= Received: by mail-wm1-f51.google.com with SMTP id 193-v6so18005457wme.3 for ; Sun, 14 Oct 2018 20:43:31 -0700 (PDT) X-Gm-Message-State: ABuFfohe0KFVyyAWD0ZQplwbiwHsyB7B/9J6AWUVf+udyo9Fs26z1Zzh oOHVgom3k7B6QvRggpD5v71XFQT+Klp5Q85pv24Vvg== X-Google-Smtp-Source: ACcGV62hlwQGoI87QIbKTMs47KI1pZUyzT5iCb1ffhg8L8URKoFvkTcsOxnTCEEO4EDBHhuvYiutgrh5s7uTvmNv2qI= X-Received: by 2002:a1c:f312:: with SMTP id q18-v6mr11544011wmq.14.1539575009617; Sun, 14 Oct 2018 20:43:29 -0700 (PDT) MIME-Version: 1.0 References: <20181015003726.29103-1-nick.desaulniers@gmail.com> In-Reply-To: <20181015003726.29103-1-nick.desaulniers@gmail.com> From: Andy Lutomirski Date: Sun, 14 Oct 2018 20:43:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] x86/mm: annotate no_context with UNWIND_HINTS To: nick.desaulniers@gmail.com, Josh Poimboeuf Cc: Dave Hansen , Andrew Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , natechancellor@gmail.com, X86 ML , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 14, 2018 at 5:37 PM Nick Desaulniers wrote: > > Fixes the objtool warning: > arch/x86/mm/fault.o: warning: objtool: no_context()+0x220: unreachable > instruction > > Link: https://github.com/ClangBuiltLinux/linux/issues/204 > Signed-off-by: Nick Desaulniers > --- > arch/x86/mm/fault.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index 47bebfe6efa7..057d2178fa19 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -760,9 +760,11 @@ no_context(struct pt_regs *regs, unsigned long error_code, > * and then double-fault, though, because we're likely to > * break the console driver and lose most of the stack dump. > */ > - asm volatile ("movq %[stack], %%rsp\n\t" > + asm volatile (UNWIND_HINT_SAVE > + "movq %[stack], %%rsp\n\t" > "call handle_stack_overflow\n\t" > - "1: jmp 1b" > + "1: jmp 1b\n\t" > + UNWIND_HINT_RESTORE > : ASM_CALL_CONSTRAINT > : "D" ("kernel stack overflow (page fault)"), > "S" (regs), "d" (address), NAK. Just below this snippet is unreachable(); Can you reply with objtool -dr output on a problematic fault.o? Josh, it *looks* like annotate_unreachable() should be doing the right thing, but something is clearly busted. Also, shouldn't compiler-clang.h contain a reasonable definition of unreachable()? --Andy