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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 3D703C43381 for ; Wed, 10 Mar 2021 22:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F8A964EDB for ; Wed, 10 Mar 2021 22:24:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231935AbhCJWXi (ORCPT ); Wed, 10 Mar 2021 17:23:38 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56670 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232058AbhCJWXJ (ORCPT ); Wed, 10 Mar 2021 17:23:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615414989; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZFzDXRjRCL3c0mZFRAdKQ2jZRyOr3oCuno8J4ucW1ys=; b=PNuET1DtmhDWZrYKYgtjEw/5pd/dVAusKMt/0sLYUlM9I7rVaxgC7FfN38UIerfao2H+BO do4+smpm0DxVPwkR4r+Z1oRYNi1xwnOBf37GNPH4HVCOJS09398KIJAm5Q7iMSoKA87L3A 0sRH4ZhAy64lI6fUU7EIjmv2rEBerAc= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-131-kXEKFyNJPHal2K0UVwVGuw-1; Wed, 10 Mar 2021 17:23:08 -0500 X-MC-Unique: kXEKFyNJPHal2K0UVwVGuw-1 Received: by mail-qv1-f71.google.com with SMTP id u15so13791204qvo.13 for ; Wed, 10 Mar 2021 14:23:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ZFzDXRjRCL3c0mZFRAdKQ2jZRyOr3oCuno8J4ucW1ys=; b=nACYq0QkeQXoy12fGTIIzE18UJ+IM7xsBt+4aZbHb8tj47IavUSqtOe3GkIDLsmFKk iZ90mt6sJEZL/rJAgfT/2m3YcGBwLXt86zWQ5ZzfKijXco1uSZYo/i4JTv2/nB/qeD7w tiua2gtKQxhr37RbkvrNrqNAB6RbfGvgPThIaIR26qthyWsf3LKPKMJkLcr68etiL4+j e079JwUSOIE4lSGer5A3JtxX6vTUeS6OEazTol79WUFqPAJ9vnUCYONaEWTD7RM/27Sz gesdIzd3fhxO9zzi1ZV3u5mSdH4CtO1vEff73kdhYPl8dRr/dGb7g/yds5tLw7fCk+uR ibjA== X-Gm-Message-State: AOAM532C/Ij04C0cSD36Dl2/I6BccqZfdP8MdfR2ho0Dqh4SAfYGMhOv cjL/BCCmCnaUm/g/KnrKKzskg1aAc8aeS+dl040QXjXP8auFkCLnP3GSU2kgqp9VqOXk6eIPDlC g45AjLS+YiDqYSABxzwOmTkhlDbpe7B9pA9aH6zGI99Z5N6OYTt5+c98++BfORgnxJQ82iQ== X-Received: by 2002:ac8:66d6:: with SMTP id m22mr4889769qtp.56.1615414987268; Wed, 10 Mar 2021 14:23:07 -0800 (PST) X-Google-Smtp-Source: ABdhPJx0t3Sv/WtT2KXEpJpvdRgG/DJ9qTaCC0wpr6ZtX+MfqYxr2PjwtYccR5Z4rx16/S25TA6Rzg== X-Received: by 2002:ac8:66d6:: with SMTP id m22mr4889741qtp.56.1615414986928; Wed, 10 Mar 2021 14:23:06 -0800 (PST) Received: from xz-x1.redhat.com ([142.126.89.138]) by smtp.gmail.com with ESMTPSA id e18sm451364qtr.52.2021.03.10.14.23.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Mar 2021 14:23:06 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Andrea Arcangeli , Michael Kerrisk , Axel Rasmussen , linux-kernel@vger.kernel.org, peterx@redhat.com, Linux MM Mailing List , Andrew Morton , Alejandro Colomar , Nadav Amit , Mike Rapoport Subject: [PATCH v3 4/4] ioctl_userfaultfd.2: Add write-protect mode docs Date: Wed, 10 Mar 2021 17:23:00 -0500 Message-Id: <20210310222300.200054-5-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210310222300.200054-1-peterx@redhat.com> References: <20210310222300.200054-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org Userfaultfd write-protect mode is supported starting from Linux 5.7. Signed-off-by: Peter Xu --- man2/ioctl_userfaultfd.2 | 81 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 78 insertions(+), 3 deletions(-) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index d4a8375b8..d8380896a 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -234,6 +234,11 @@ operation is supported. The .B UFFDIO_UNREGISTER operation is supported. +.TP +.B 1 << _UFFDIO_WRITEPROTECT +The +.B UFFDIO_WRITEPROTECT +operation is supported. .PP This .BR ioctl (2) @@ -322,9 +327,6 @@ Track page faults on missing pages. .B UFFDIO_REGISTER_MODE_WP Track page faults on write-protected pages. .PP -Currently, the only supported mode is -.BR UFFDIO_REGISTER_MODE_MISSING . -.PP If the operation is successful, the kernel modifies the .I ioctls bit-mask field to indicate which @@ -443,6 +445,13 @@ operation: .TP .B UFFDIO_COPY_MODE_DONTWAKE Do not wake up the thread that waits for page-fault resolution +.TP +.B UFFDIO_COPY_MODE_WP +Copy the page with read-only permission. +This allows the user to trap the next write to the page, which will block and +generate another write-protect userfault message. +This is only used in conjunction with write-protect mode when both missing and +write-protect modes are enabled. .PP The .I copy @@ -654,6 +663,72 @@ field of the structure was not a multiple of the system page size; or .I len was zero; or the specified range was otherwise invalid. +.SS UFFDIO_WRITEPROTECT (Since Linux 5.7) +Write-protect or write-unprotect an userfaultfd registered memory range +registered with mode +.BR UFFDIO_REGISTER_MODE_WP . +.PP +The +.I argp +argument is a pointer to a +.I uffdio_range +structure as shown below: +.PP +.in +4n +.EX +struct uffdio_writeprotect { + struct uffdio_range range; /* Range to change write permission */ + __u64 mode; /* Mode to change write permission */ +}; +.EE +.in +There're two mode bits that are supported in this structure: +.TP +.B UFFDIO_WRITEPROTECT_MODE_WP +When this mode bit is set, the ioctl will be a write-protect operation upon the +memory range specified by +.IR range . +Otherwise it'll be a write-unprotect operation upon the specified range, which +can be used to resolve an userfaultfd write-protect page fault. +.TP +.B UFFDIO_WRITEPROTECT_MODE_DONTWAKE +When this mode bit is set, do not wake up any thread that waits for page-fault +resolution after the operation. +This could only be specified if +.B UFFDIO_WRITEPROTECT_MODE_WP +is not specified. +.PP +This +.BR ioctl (2) +operation returns 0 on success. +On error, \-1 is returned and +.I errno +is set to indicate the error. +Possible errors include: +.TP +.B EINVAL +The +.I start +or the +.I len +field of the +.I ufdio_range +structure was not a multiple of the system page size; or +.I len +was zero; or the specified range was otherwise invalid. +.TP +.B EAGAIN +The process was interrupted and need to retry. +.TP +.B ENOENT +The range specified in +.I range +is not valid. +For example, the virtual address does not exist, or not registered with +userfaultfd write-protect mode. +.TP +.B EFAULT +Encountered a generic fault during processing. .SH RETURN VALUE See descriptions of the individual operations, above. .SH ERRORS -- 2.26.2