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=-4.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 205E5C433B4 for ; Sun, 16 May 2021 07:48:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E08B86108B for ; Sun, 16 May 2021 07:48:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233935AbhEPHtk (ORCPT ); Sun, 16 May 2021 03:49:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232256AbhEPHth (ORCPT ); Sun, 16 May 2021 03:49:37 -0400 Received: from mail-ej1-x634.google.com (mail-ej1-x634.google.com [IPv6:2a00:1450:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DEDECC061573 for ; Sun, 16 May 2021 00:48:22 -0700 (PDT) Received: by mail-ej1-x634.google.com with SMTP id n2so4511760ejy.7 for ; Sun, 16 May 2021 00:48:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=h6oV9wd5kA7+2uCRYGnxwbcp91vUgplkvPfsbcp8srY=; b=Or7C8gx2e0I7UuD8b4rio9s7sssLTUmnyIR4hTR7rlLFME/0QDuq9u28n9zDVVG80h BucAclKbJ4xRH4yAS0A9qnPe4/K1X/R+RpQiZ+ho4XO2TLQCBG6TPgKms5pJIWfQzPGE 8vztCJ5FOhNNzozx3Tkh5CcgeqisvNaOLhAxsDI2LW8KnNfIwlFi5/6cFTLO0IcPAtiQ fS9XfYe3R5MX+gTCuNe0DpH8iMNK/YhucgeWRG5IFqxwx4jgiEtAOOGhvu/Pe7EyMWZo N/Y7b3u0SAdib+J/MpFq+g6FXvkH/5gApg/naZrAi/0oQ2+HpZx8AVF/JGjbEZV4UOL6 N25w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=h6oV9wd5kA7+2uCRYGnxwbcp91vUgplkvPfsbcp8srY=; b=GiSOZZR8lBu0/AD7MXMLfuvbUv0UBLlmHcK0VMSMnwSZB0SLESEU7LcKS+qRs/NIel bWEkA66baIGoejhuLGuNLycMsZvVQJm2iHtQbWabkm/c32BnnxCAYn4ZZCFLL/cyjHA5 Olmsjjbyk4/E9DEcHb+ihe2QRE7KeCgveWM8xsSgdpibou+be0fMh8nr0p4wd19xwbNZ rfGHRk1jgU97zPrVn+4J0jWlrF258sAg/RJtTDreWFAGmGmmqk9lGmOluXd5Yq4ZoVEA 3pw3eJeFqCQ4w0uMcgs5cwOiVgMugqEcQnQO4Z72geVHzF+uITvWEf1x5cEOSym96KWa gScw== X-Gm-Message-State: AOAM531umeT45ArZs0VI3zejQMTvbsRK7Zugss8RV8OqdbhuZKxDejts sXK0aESPTFm5mqH4rYq9jIQ= X-Google-Smtp-Source: ABdhPJzYvfcQ2BB+OtBAXmsE3htFgq+2Pz7DZByrbDxmyceB/bwrATlVX4914puGIliWNpu1JjUzoQ== X-Received: by 2002:a17:906:170a:: with SMTP id c10mr55285983eje.493.1621151301548; Sun, 16 May 2021 00:48:21 -0700 (PDT) Received: from gmail.com (563BBFD3.dsl.pool.telekom.hu. [86.59.191.211]) by smtp.gmail.com with ESMTPSA id a22sm8554251edu.14.2021.05.16.00.48.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 16 May 2021 00:48:21 -0700 (PDT) Sender: Ingo Molnar Date: Sun, 16 May 2021 09:48:19 +0200 From: Ingo Molnar To: "H. Peter Anvin" Cc: Ingo Molnar , Thomas Gleixner , Andy Lutomirski , Borislav Petkov , Linux Kernel Mailing List Subject: Re: [PATCH v3 1/4] x86/syscall: sign-extend system calls on entry to int Message-ID: References: <20210515011015.2707542-1-hpa@zytor.com> <20210515011015.2707542-2-hpa@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210515011015.2707542-2-hpa@zytor.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * H. Peter Anvin wrote: > This is an ABI change, but is in fact a revert to the original x86-64 > ABI. The original assembly entry code would zero-extend the system > call number; this patch uses sign extend to be explicit that this is > treated as a signed number (although in practice it makes no > difference, of course) and to avoid people getting the idea of > "optimizing" it, as has happened on at least two(!) separate > occasions. The original x86-64 ABI as documented by AMD, as we (probably) never had this in Linux, right? Sounds sensible to do this, assuming nothing relies on the weirdness. Thanks, Ingo