From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753086AbdJGCww (ORCPT ); Fri, 6 Oct 2017 22:52:52 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:41719 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751485AbdJGCwu (ORCPT ); Fri, 6 Oct 2017 22:52:50 -0400 From: Prakash Sangappa To: mtk.manpages@gmail.com Cc: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, arcange@redhat.com, rppt@linux.vnet.ibm.com, mhocko@suse.com, prakash.sangappa@oracle.com Subject: [PATCH] Userfaultfd: Add description for UFFD_FEATURE_SIGBUS Date: Fri, 6 Oct 2017 19:52:20 -0700 Message-Id: <1507344740-21993-1-git-send-email-prakash.sangappa@oracle.com> X-Mailer: git-send-email 2.7.4 X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Userfaultfd feature UFFD_FEATURE_SIGBUS was merged recently and should be available in Linux 4.14 release. This patch is for the manpage changes documenting this API. Documents the following commit: commit 2d6d6f5a09a96cc1fec7ed992b825e05f64cb50e Author: Prakash Sangappa Date: Wed Sep 6 16:23:39 2017 -0700 mm: userfaultfd: add feature to request for a signal delivery Signed-off-by: Prakash Sangappa --- man2/ioctl_userfaultfd.2 | 9 +++++++++ man2/userfaultfd.2 | 17 +++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index 60fd29b..cfc65ae 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -196,6 +196,15 @@ with the flag set, .BR memfd_create (2), and so on. +.TP +.B UFFD_FEATURE_SIGBUS +Since Linux 4.14, If this feature bit is set, no page-fault events( +.B UFFD_EVENT_PAGEFAULT +) will be delivered, instead a +.B SIGBUS +signal will be sent to the faulting process. Applications using this +feature will not require the use of a userfaultfd monitor for handling +page-fault events. .IP The returned .I ioctls diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index 1741ee3..a033742 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -172,6 +172,23 @@ or .BR ioctl (2) operations to resolve the page fault. .PP +Starting from Linux 4.14, if application sets +.B UFFD_FEATURE_SIGBUS +feature bit using +.B UFFDIO_API +.BR ioctl (2) +, no page fault notification will be forwarded to +the user-space, instead a +.B SIGBUS +signal is delivered to the faulting process. With this feature, +userfaultfd can be used for robustness purpose to simply catch +any access to areas within the registered address range that do not +have pages allocated, without having to deal with page-fault events. +No userfaultd monitor will be required for handling page faults. For +example, this feature can be useful for applications that want to +prevent the kernel from automatically allocating pages and filling +holes in sparse files when the hole is accessed thru mapped address. +.PP Details of the various .BR ioctl (2) operations can be found in -- 2.7.4