From nobody Thu Sep 11 22:42:59 2025 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 9F47EC04FE1 for ; Mon, 7 Aug 2023 12:37:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233607AbjHGMhU (ORCPT ); Mon, 7 Aug 2023 08:37:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229562AbjHGMhS (ORCPT ); Mon, 7 Aug 2023 08:37:18 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E685810F2; Mon, 7 Aug 2023 05:37:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=53jHvCThY56ekVsZwPC+RAqN66FMg8fPTI36UoUqaKU=; b=eqmLvazGl7vBH7qJgPl+mV8Rn1 Db9gNWnIQZ6A9f+8x4iCTa3tOp45OF1tMlCfJCzFVwpufed2L7Syzuc7UOY9iih9D4mimwCVtlcDQ 5FAN+SfFoNcoZgnC0ba/iDFxh6N7opePHRF2GS1XFSgF6jwb1TdsPczXS237JH48Uo2hQM6B4//4N 5GuRLi7XiTPgNCyPEcQw5aln/fT+PUo0QdWUVkjjAyoUG6MzYF3TqTPqdrdvCZsTN9LYGFKD0FGFf TQK0/YtXVD4x9hkj8ivhhhRiVCQ2Rx4zxOsKNOlw0CNxd3aDi11330mX1Q9ng36kvGJP2ha83Y9ht EjcAsWdA==; 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 1qSzTk-00AxFz-Rv; Mon, 07 Aug 2023 12:36:57 +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)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D39913005A2; Mon, 7 Aug 2023 14:36:54 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 8A81C2021C3D4; Mon, 7 Aug 2023 14:36:54 +0200 (CEST) Message-ID: <20230807123322.814039156@infradead.org> User-Agent: quilt/0.66 Date: Mon, 07 Aug 2023 14:18:44 +0200 From: Peter Zijlstra To: tglx@linutronix.de, axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, peterz@infradead.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: [PATCH v2 01/14] futex: Clarify FUTEX2 flags References: <20230807121843.710612856@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" sys_futex_waitv() is part of the futex2 series (the first and only so far) of syscalls and has a flags field per futex (as opposed to flags being encoded in the futex op). This new flags field has a new namespace, which unfortunately isn't super explicit. Notably it currently takes FUTEX_32 and FUTEX_PRIVATE_FLAG. Introduce the FUTEX2 namespace to clarify this Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Andr=C3=A9 Almeida --- include/uapi/linux/futex.h | 16 +++++++++++++--- kernel/futex/syscalls.c | 7 +++---- 2 files changed, 16 insertions(+), 7 deletions(-) --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -44,10 +44,20 @@ FUTEX_PRIVATE_FLAG) =20 /* - * Flags to specify the bit length of the futex word for futex2 syscalls. - * Currently, only 32 is supported. + * Flags for futex2 syscalls. */ -#define FUTEX_32 2 + /* 0x00 */ + /* 0x01 */ +#define FUTEX2_SIZE_U32 0x02 + /* 0x04 */ + /* 0x08 */ + /* 0x10 */ + /* 0x20 */ + /* 0x40 */ +#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG + +/* do not use */ +#define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */ =20 /* * Max numbers of elements in a futex_waitv array --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -183,8 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); } =20 -/* Mask of available flags for each futex in futex_waitv list */ -#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG) +#define FUTEX2_VALID_MASK (FUTEX2_SIZE_U32 | FUTEX2_PRIVATE) =20 /** * futex_parse_waitv - Parse a waitv array from userspace @@ -205,10 +204,10 @@ static int futex_parse_waitv(struct fute if (copy_from_user(&aux, &uwaitv[i], sizeof(aux))) return -EFAULT; =20 - if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved) + if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved) return -EINVAL; =20 - if (!(aux.flags & FUTEX_32)) + if (!(aux.flags & FUTEX2_SIZE_U32)) return -EINVAL; =20 futexv[i].w.flags =3D aux.flags;