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 10D70C001DC for ; Fri, 21 Jul 2023 11:01:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231422AbjGULBM (ORCPT ); Fri, 21 Jul 2023 07:01:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231407AbjGUK7n (ORCPT ); Fri, 21 Jul 2023 06:59:43 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 669C630E8; Fri, 21 Jul 2023 03:59:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=+GPeC+b0X/r2JxaFmk2Vd0m0Q7Mcvnivdsn9xJjP8Rw=; b=UhkHzgo2Hvp0CRLk+p6vRsrvw7 YgKgzf/XCyoOSRLPIKtpnbjTY6nadJlG2LCSkDKGPR7qb8qcgzOyFbOuaRcYAAaKiLE+s/2Wch+VQ egzMeJsCik0LwJptN4u7633AsD1TZrbo6CKJXqjOeIy8/4hE26m1ZmKYamWi7UZxxexcUsslTRml/ 1v13/bZNfkaqUAEObRAD9RWkVA6+HiuEfzeNV118iLAl2qc4vpbNNPPXVPHhKO4TLaLeVwUrWOCmP stLfJlSL/fiD3SQ7WN7OuuSX53eIVavOdM2+oaaizUSGHhfpaZS+fWd+w4ZeXu0qnqvhUCB930wgL hhHazrSg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qMnqL-0000LF-0i; Fri, 21 Jul 2023 10:58:41 +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 404B3301C81; Fri, 21 Jul 2023 12:58:39 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 287DF3157E620; Fri, 21 Jul 2023 12:58:38 +0200 (CEST) Message-ID: <20230721105744.571094000@infradead.org> User-Agent: quilt/0.66 Date: Fri, 21 Jul 2023 12:22:50 +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 v1 13/14] futex: Enable FUTEX2_{8,16} References: <20230721102237.268073801@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org When futexes are no longer u32 aligned, the lower offset bits are no longer available to put type info in. However, since offset is the offset within a page, there are plenty bits available on the top end. After that, pass flags into futex_get_value_locked() for WAIT and disallow FUTEX2_64 instead of mandating FUTEX2_32. Signed-off-by: Peter Zijlstra (Intel) --- include/linux/futex.h | 11 ++++++----- kernel/futex/core.c | 9 +++++++++ kernel/futex/futex.h | 4 ++-- kernel/futex/waitwake.c | 5 +++-- 4 files changed, 20 insertions(+), 9 deletions(-) --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -16,18 +16,19 @@ struct task_struct; * The key type depends on whether it's a shared or private mapping. * Don't rearrange members without looking at hash_futex(). * - * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. - * We use the two low order bits of offset to tell what is the kind of key : + * offset is the position within a page and is in the range [0, PAGE_SIZE). + * The high bits of the offset indicate what kind of key this is: * 00 : Private process futex (PTHREAD_PROCESS_PRIVATE) * (no reference on an inode or mm) * 01 : Shared futex (PTHREAD_PROCESS_SHARED) * mapped on a file (reference on the underlying inode) * 10 : Shared futex (PTHREAD_PROCESS_SHARED) * (but private mapping on an mm, and reference taken on it) -*/ + */ -#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */ -#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */ +#define FUT_OFF_INODE (PAGE_SIZE << 0) +#define FUT_OFF_MMSHARED (PAGE_SIZE << 1) +#define FUT_OFF_SIZE (PAGE_SIZE << 2) union futex_key { struct { --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -308,6 +308,15 @@ int get_futex_key(void __user *uaddr, un } /* + * Encode the futex size in the offset. This makes cross-size + * wake-wait fail -- see futex_match(). + * + * NOTE that cross-size wake-wait is fundamentally broken wrt + * FLAGS_NUMA but could possibly work for !NUMA. + */ + key->both.offset |= FUT_OFF_SIZE * (flags & FLAGS_SIZE_MASK); + + /* * PROCESS_PRIVATE futexes are fast. * As the mm cannot disappear under us and the 'key' only needs * virtual address, we dont even have to find the underlying vma. --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -79,8 +79,8 @@ static inline bool futex_flags_valid(uns return false; } - /* Only 32bit futexes are implemented -- for now */ - if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32) + /* 64bit futexes aren't implemented -- yet */ + if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64) return false; /* --- a/kernel/futex/waitwake.c +++ b/kernel/futex/waitwake.c @@ -434,11 +434,12 @@ static int futex_wait_multiple_setup(str for (i = 0; i < count; i++) { u32 __user *uaddr = (u32 __user *)(unsigned long)vs[i].w.uaddr; + unsigned int flags = vs[i].w.flags; struct futex_q *q = &vs[i].q; u32 val = vs[i].w.val; hb = futex_q_lock(q); - ret = futex_get_value_locked(&uval, uaddr, FLAGS_SIZE_32); + ret = futex_get_value_locked(&uval, uaddr, flags); if (!ret && uval == val) { /* @@ -606,7 +607,7 @@ int futex_wait_setup(u32 __user *uaddr, retry_private: *hb = futex_q_lock(q); - ret = futex_get_value_locked(&uval, uaddr, FLAGS_SIZE_32); + ret = futex_get_value_locked(&uval, uaddr, flags); if (ret) { futex_q_unlock(*hb);