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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 0FA59C433DB for ; Thu, 14 Jan 2021 23:49:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF88423AAA for ; Thu, 14 Jan 2021 23:49:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731113AbhANXtS (ORCPT ); Thu, 14 Jan 2021 18:49:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:34692 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731085AbhANXtR (ORCPT ); Thu, 14 Jan 2021 18:49:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610668071; 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=gjwyOUiSUpCSsJCrPVANVQOkwMWYIbGT02bwnsYs1vM=; b=EV/t8AoizdCqiWsKQK2zKsrD9gjgJlHeudj2z7nszg8VFAIs1eFBz4/JMGsIXNWQaaTj+x +OYnbqh6CAreDbvyBKs5oVUTl8YoOkoiSm36vG1YF2cGB5C8lFA/h7RkAp41iunnrAw6fb f+lO49h3d8EZhcCGqOtrZEAWxNzGKEw= 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-495-nua4-psjMg-xq2q7Ki0vvQ-1; Thu, 14 Jan 2021 18:47:47 -0500 X-MC-Unique: nua4-psjMg-xq2q7Ki0vvQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1CE1015720; Thu, 14 Jan 2021 23:47:45 +0000 (UTC) Received: from treble (ovpn-120-156.rdu2.redhat.com [10.10.120.156]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 969DC5F9AC; Thu, 14 Jan 2021 23:47:42 +0000 (UTC) Date: Thu, 14 Jan 2021 17:47:37 -0600 From: Josh Poimboeuf To: Andrew Cooper Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Sami Tolvanen , Sedat Dilek , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, Miroslav Benes , "Rafael J. Wysocki" , Len Brown , Pavel Machek Subject: Re: [PATCH 17/21] x86/acpi: Convert indirect jump to retpoline Message-ID: <20210114234737.xpltgdu3vpa6spgb@treble> References: <5017a6c5-55fa-0767-b1ed-2bd9e2a5efc1@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5017a6c5-55fa-0767-b1ed-2bd9e2a5efc1@citrix.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 14, 2021 at 10:59:39PM +0000, Andrew Cooper wrote: > On 14/01/2021 19:40, Josh Poimboeuf wrote: > > It's kernel policy to not have (unannotated) indirect jumps because of > > Spectre v2. This one's probably harmless, but better safe than sorry. > > Convert it to a retpoline. > > > > Cc: "Rafael J. Wysocki" > > Cc: Len Brown > > Cc: Pavel Machek > > Signed-off-by: Josh Poimboeuf > > --- > > arch/x86/kernel/acpi/wakeup_64.S | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S > > index 5d3a0b8fd379..0b371580e620 100644 > > --- a/arch/x86/kernel/acpi/wakeup_64.S > > +++ b/arch/x86/kernel/acpi/wakeup_64.S > > @@ -7,6 +7,7 @@ > > #include > > #include > > #include > > +#include > > > > # Copyright 2003 Pavel Machek > > > @@ -39,7 +40,7 @@ SYM_FUNC_START(wakeup_long64) > > movq saved_rbp, %rbp > > > > movq saved_rip, %rax > > - jmp *%rax > > + JMP_NOSPEC rax > > SYM_FUNC_END(wakeup_long64) > > I suspect this won't work as you intend. > > wakeup_long64() still executes on the low mappings, not the high > mappings, so the `jmp __x86_indirect_thunk_rax` under this JMP_NOSPEC > will wander off into the weeds. > > This is why none of the startup "jmps from weird contexts onto the high > mappings" have been retpolined-up. D'oh. Of course it wouldn't be that easy. I suppose the other two retpoline patches (15 and 21) are bogus as well. -- Josh