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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 81AABC28CF8 for ; Mon, 15 Oct 2018 05:17:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32E202087D for ; Mon, 15 Oct 2018 05:17:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LOXbYdqo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 32E202087D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 S1726708AbeJONAr (ORCPT ); Mon, 15 Oct 2018 09:00:47 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:44532 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726424AbeJONAr (ORCPT ); Mon, 15 Oct 2018 09:00:47 -0400 Received: by mail-wr1-f66.google.com with SMTP id 63-v6so19614483wra.11 for ; Sun, 14 Oct 2018 22:17:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=G7scxTHofyfLz6cHewgOfbzH3drfg6Biu7YDoFSBCC4=; b=LOXbYdqol7i71SR7DI/E/mJiBgen6/5OLeSNeEmtfgOB1+MwEtMZnzH9aRHNlE0QyO ua1ZbjYXuk4ApPs/Co1FXBrZSiVE2tJjI0HYM64C/xnalzWvs+tyZHD/yxpjL9nuzMGQ QjcoM7lEcs19xXoUpJa5P7bbcQiWJ0+niIcNoL9fXSZBInMK8PvLNhmI1cfpoI0snKGy i7pzbKC6zWCpQ4NVStdgnSTAc7rzAze3/RxnHvMGz1f05Zo0SbJMxGTWp6dbzk4p557G QQ74ZtR9X9v31ZKB8b+cHZ3faNEOr8Brd0I21O6617ZHIiZcIauW6Zkb8f6y52vctsiQ dlqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=G7scxTHofyfLz6cHewgOfbzH3drfg6Biu7YDoFSBCC4=; b=b2AY54yTe92Ah8MrGVN7dbIz7JrWHfP63jmxtc40G+/1Oggrb6KlGnVOYPeJxMo/gI mq1MGeZjc3rIAMYLlHfVFeYLOvJxljxNwcLfymXD070W0RQAtE3jrXqgco99p01hEqHG cE3Ig2WmS+NoDS4ivr+KSkbjX5hTLndmclCevUSkMJJwbBKnInmhSBNU3EsMW6P7pVwH PN0sSwBjsa/oc+gr0uNs4sZwNKhAgSJkribN/N6AN2rQsu0g2trB8xCtKqb3jLf9IJgn 7iPOozaG3q/Dfn9lkKIYSNLVW7VxdsgIqldGz7jZI7VQH7qyidGKOvRzMnvcSbKo4b7A rSeQ== X-Gm-Message-State: ABuFfoi4DXizDfpA6QPnCl9t6KTbAUMBi3HI86L4QlQ6q+qtC70QYvpU hYUtqpC+lN5J8Q+xFA6fSuc8DqFJjnY= X-Google-Smtp-Source: ACcGV61fpqtcFEgMk6HLSEQURr9P6KJLgin/isRx9ba0C9Wx5fupd3XEQqeToJTV54PUCaNRqeCRHg== X-Received: by 2002:adf:8523:: with SMTP id 32-v6mr13565294wrh.72.1539580627986; Sun, 14 Oct 2018 22:17:07 -0700 (PDT) Received: from flashbox ([2a01:4f8:10b:24a5::2]) by smtp.gmail.com with ESMTPSA id t82-v6sm7864692wme.30.2018.10.14.22.17.06 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 14 Oct 2018 22:17:07 -0700 (PDT) Date: Sun, 14 Oct 2018 22:17:05 -0700 From: Nathan Chancellor To: Andy Lutomirski Cc: nick.desaulniers@gmail.com, Josh Poimboeuf , Dave Hansen , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , X86 ML , LKML Subject: Re: [PATCH] x86/mm: annotate no_context with UNWIND_HINTS Message-ID: <20181015051705.GA20687@flashbox> References: <20181015003726.29103-1-nick.desaulniers@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 08:43:18PM -0700, Andy Lutomirski wrote: > 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 Hi Andy, Did you mean 'objdump -dr'? If so, here you go (rather long, sorry if I should have pasted it here instead): https://gist.github.com/nathanchance/f038bb0a6653b975bb8a4e64fcd5503e Nathan