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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3915C41513 for ; Mon, 31 Jul 2023 19:20:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230139AbjGaTUg (ORCPT ); Mon, 31 Jul 2023 15:20:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230093AbjGaTUf (ORCPT ); Mon, 31 Jul 2023 15:20:35 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9EE561713; Mon, 31 Jul 2023 12:20:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=7kEonDGMduTbFsCil+eszqrNrb5nrnY+6n0LGU5HhHA=; b=Wz6DDGLEoUvHSzKosfdPLNuAx6 pXzK5fDBMLzFxdrzFewsUb1Lr3/dW14cR14Wa3XBkxzL+dYZGrYJ7gWZhgWVr7Q5I5Tl6WWpv/w+7 45Zrya0kQ+Bi7L5Pe2IpLcc6aUA+qJYMpb+nBBo/j+Sj2OS9zTqo3Jo2zk4AdNTiIBj//QH61/SvS 7sNEHNYkvPMNtO67KQNvk54Nq9kcR140qlDdm1ebt67M/ZqM6voGTbaa61kZ9iE/MCYWR61O5smiT S0kZfVowlGQpc9n4WuK3UsLH7XkISpISXB5SUfVdmKjJmcKJRrguPeCEYo74GlgveOrKsdlTeUixB DQclJDog==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qQYRB-003LT8-T5; Mon, 31 Jul 2023 19:20:14 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 3951A3002CE; Mon, 31 Jul 2023 21:20:13 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 07A8E203C783E; Mon, 31 Jul 2023 21:20:13 +0200 (CEST) Date: Mon, 31 Jul 2023 21:20:12 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com, Andrew Morton , urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com, Arnd Bergmann , linux-api@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, malteskarupke@web.de Subject: Re: [PATCH v1 02/14] futex: Extend the FUTEX2 flags Message-ID: <20230731192012.GA11704@hirez.programming.kicks-ass.net> References: <20230721102237.268073801@infradead.org> <20230721105743.819362688@infradead.org> <87edkonjrk.ffs@tglx> <87mszcm0zw.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87mszcm0zw.ffs@tglx> Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, Jul 31, 2023 at 07:42:11PM +0200, Thomas Gleixner wrote: > Aargh. This is really nasty to make FUTEX2_64 0x3 and abuse it to test > the flags for validity. Intuitive and obvious is something else. Like so then? --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -57,6 +57,8 @@ /* 0x40 */ #define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG +#define FUTEX2_SIZE_MASK 0x03 + /* do not use */ #define FUTEX_32 FUTEX2_32 /* historical accident :-( */ --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -183,7 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); } -#define FUTEX2_MASK (FUTEX2_64 | FUTEX2_PRIVATE) +#define FUTEX2_MASK (FUTEX2_SIZE_MASK | FUTEX2_PRIVATE) /** * futex_parse_waitv - Parse a waitv array from userspace @@ -208,11 +208,11 @@ static int futex_parse_waitv(struct fute return -EINVAL; if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) { - if ((aux.flags & FUTEX2_64) == FUTEX2_64) + if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_64) return -EINVAL; } - if ((aux.flags & FUTEX2_64) != FUTEX2_32) + if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_32) return -EINVAL; futexv[i].w.flags = aux.flags;