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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 8FB46C43441 for ; Thu, 29 Nov 2018 17:15:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B3D420863 for ; Thu, 29 Nov 2018 17:15:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="u0IBPrpW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4B3D420863 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.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 S1728827AbeK3EV4 (ORCPT ); Thu, 29 Nov 2018 23:21:56 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48584 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbeK3EVz (ORCPT ); Thu, 29 Nov 2018 23:21:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=sB2Zet845/zGK7oJTdtP+TsAkhn57TmKCUffL2h0Sc0=; b=u0IBPrpWtFDGh9ujm0ItLunO8g XBgECgPX46eZ489TB5rmlEu8gspBu98h8c10FupxhcgnfESgCweim8DNtzY2Fb2iHGeaW0pb4yh+g fsXEpuvMyjJfLOP5x49TidpFOc2kS/X5XL/E3x6iCzwnPPvPfvPoGSzFc3wR5nRC61oGSz0MRrzvI pBLD24NaA4bbperdjO6j0vr5ctvFt6SHunNqpVxHabQjKgE5/aXp/dBtVJ3N9WfCBEB46tOCvTY5H tdVezgwkje3iYNXiQgEfnrOrKnIabW2vVaXmvioL1AebloxGMUNkvYtr/JrijUltZo9a5KzMGlzcN gfyzPzMw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gSPuf-0001WK-EC; Thu, 29 Nov 2018 17:15:41 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E1ABC2029FD58; Thu, 29 Nov 2018 18:15:39 +0100 (CET) Date: Thu, 29 Nov 2018 18:15:39 +0100 From: Peter Zijlstra To: Andy Lutomirski Cc: Josh Poimboeuf , Andy Lutomirski , X86 ML , LKML , Ard Biesheuvel , Steven Rostedt , Ingo Molnar , Thomas Gleixner , Linus Torvalds , Masami Hiramatsu , Jason Baron , Jiri Kosina , David Laight , Borislav Petkov , julia@ni.com, jeyu@kernel.org, "H. Peter Anvin" Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64 Message-ID: <20181129171539.GD9027@hirez.programming.kicks-ass.net> References: <20181126200801.GW2113@hirez.programming.kicks-ass.net> <20181126212628.4apztfazichxnt7r@treble> <20181127084330.GX2113@hirez.programming.kicks-ass.net> <20181129094210.GC2131@hirez.programming.kicks-ass.net> <20181129143853.GO2131@hirez.programming.kicks-ass.net> <20181129163342.tp5wlfcyiazwwyoh@treble> <20181129164914.GA9027@hirez.programming.kicks-ass.net> <0FDA053D-7ADC-4F42-AEA5-99DA155FCED0@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0FDA053D-7ADC-4F42-AEA5-99DA155FCED0@amacapital.net> 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 Thu, Nov 29, 2018 at 08:59:31AM -0800, Andy Lutomirski wrote: > If you make it conditional on CPL, do it for 32-bit as well, add > comments, > and convince yourself that there isn’t a better solution > (like pointing IP at a stub that retpolines to the target by reading > the function pointer, a la the unoptimizable version), then okay, I > guess, with only a small amount of grumbling. Right; so we _could_ grow the trampoline with a retpoline indirect call and ret. It just makes the trampoline a whole lot bigger, but it could work.