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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 14BA9C433DF for ; Wed, 10 Jun 2020 17:42:29 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D9B572072E for ; Wed, 10 Jun 2020 17:42:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Ekjs2l0R" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9B572072E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=VOiDR14Djh7HzOy0VlpZ4Sdoix13ZkCoPokuAoegugk=; b=Ekjs2l0RIIPwqd BCqo7YVlRMQ+FZ+/2xvueiEJnr5GhETpBOEXGAAFS90W7A8eIbgzjhHN42mtctvxCjg+VHUjFjrxB b5K8ZcYMD7VDExQGEz3xI6hIk6/7fZGEVfP8m82uOAgfwd1zBAlxofzzg1DxGiG5w4iPqVoWqM8dN +7NtS+jkiYs0mEnDjrOFmKTzQKo4BGHdSXKFHuIb4zZYzPUo2rNKAeu3rXCn7H3DX5K96QhJe7xA3 YYMDGbzsCGbVFyxqTHXdQAlCcVLZeplx+AjJHoQ0dZU+G5E8uoqZCaJTWDeTY65nfa0HK0NPJSMII g2kiFy9FxLURiNILpoLA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jj4k0-0007KQ-F3; Wed, 10 Jun 2020 17:42:20 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jj4jx-0007JP-8W for linux-arm-kernel@lists.infradead.org; Wed, 10 Jun 2020 17:42:18 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 008B91FB; Wed, 10 Jun 2020 10:42:14 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E487E3F6CF; Wed, 10 Jun 2020 10:42:12 -0700 (PDT) Date: Wed, 10 Jun 2020 18:42:05 +0100 From: Catalin Marinas To: Dave Martin Subject: Re: [RFC PATCH v2 6/6] prctl.2: Add tagged address ABI control prctls (arm64) Message-ID: <20200610174205.GL26099@gaia> References: <1590614258-24728-1-git-send-email-Dave.Martin@arm.com> <1590614258-24728-7-git-send-email-Dave.Martin@arm.com> <20200609172232.GA63286@C02TF0J2HF1T.local> <20200610100641.GF25945@arm.com> <20200610152634.GJ26099@gaia> <20200610164209.GH25945@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200610164209.GH25945@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200610_104217_342599_559206B4 X-CRM114-Status: GOOD ( 15.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-man@vger.kernel.org, Michael Kerrisk , Vincenzo Frascino , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 10, 2020 at 05:42:09PM +0100, Dave P Martin wrote: > On Wed, Jun 10, 2020 at 04:26:34PM +0100, Catalin Marinas wrote: > > On Wed, Jun 10, 2020 at 11:06:42AM +0100, Dave P Martin wrote: > > > On Tue, Jun 09, 2020 at 06:22:32PM +0100, Catalin Marinas wrote: > > > > On Wed, May 27, 2020 at 10:17:38PM +0100, Dave P Martin wrote: > > > > > +.IP > > > > > +The level of support is selected by > > > > > +.IR "(unsigned int) arg2" , > > > > > > > > We use (unsigned long) for arg2. > > > > > > Hmmm, not quite sure how I came up with unsigned int here. I'll just > > > drop this: the type in the prctl() prototype is unsigned long anyway. > > > > > > The type is actually moot in this case, since the valid values all fit > > > in an unsigned int. > > > > Passing an int doesn't require that the top 32-bit of the long are > > zeroed (in case anyone writes the low-level SVC by hand). > > Fair point, I was forgetting that wrinkle. Anyway, the convention in > this page seems to be that if the type is unsigned long, we don't > mention it, because the prctl() prototype says that already. > > Question: the glibc prototype for prctl is variadic, so surely any > calls that don't explicitly cast the args to unsigned long are already > theoretically broken? The #defines (and 0) are all implicitly int. > This probably affects lots of prctls. > > We may get away with it because the compiler is almost certainly going > to favour a mov over a ldr for getting small integers into regs, and mov > fortunately zeroes the top bits for us anyway. So does LDR Wd. Anyway, I think glibc (or my reading of it) has something like like: register long _x1 asm ("x1") = _x1tmp; before invoking the SVC. I assume this would do the right conversion to long. I can't tell about other libraries but I'd say it's their responsibility to convert the args to long before calling the kernel's prctl(). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel