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From: Peter Xu <peterx@redhat.com>
To: linux-man@vger.kernel.org
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	linux-kernel@vger.kernel.org,
	Linux MM Mailing List <linux-mm@kvack.org>,
	peterx@redhat.com, Axel Rasmussen <axelrasmussen@google.com>,
	Alejandro Colomar <alx.manpages@gmail.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michael Kerrisk <mtk.manpages@gmail.com>
Subject: [PATCH 4/4] ioctl_userfaultfd.2: Add write-protect mode docs
Date: Wed,  3 Mar 2021 20:59:47 -0500	[thread overview]
Message-ID: <20210304015947.517713-5-peterx@redhat.com> (raw)
In-Reply-To: <20210304015947.517713-1-peterx@redhat.com>

Userfaultfd write-protect mode is supported starting from Linux 5.7.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 man2/ioctl_userfaultfd.2 | 74 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
index 1965d1932..3feb888a8 100644
--- a/man2/ioctl_userfaultfd.2
+++ b/man2/ioctl_userfaultfd.2
@@ -208,10 +208,11 @@ signal will be sent to the faulting process.
 Applications using this
 feature will not require the use of a userfaultfd monitor for processing
 memory accesses to the regions registered with userfaultfd.
+.TP
 .BR UFFD_FEATURE_THREAD_ID " (since Linux 4.14)"
 If this feature bit is set,
 .I uffd_msg.pagefault.feat.ptid
-Will be set
+will be set to the faulted thread ID for each page fault message.
 .PP
 The returned
 .I ioctls
@@ -233,6 +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)
@@ -321,9 +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
@@ -653,6 +656,69 @@ 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) Do write-protect or write-unprotect for an userfaultfd
+registered memory range 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 modes 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.
+.TP
+.B UFFDIO_WRITEPROTECT_MODE_DONTWAKE
+Do not wake up the thread that waits for page-fault resolution after the
+operation.  This could only be specified if
+.B UFFDIO_WRITEPROTECT_MODE_WP
+is not specified (in a resolving stage, not protecting stage).
+.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.  E.g., 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


  parent reply	other threads:[~2021-03-04  2:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04  1:59 [PATCH 0/4] man2: udpate mm/userfaultfd manpages to latest Peter Xu
2021-03-04  1:59 ` [PATCH 1/4] userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Peter Xu
2021-03-04  6:38   ` Mike Rapoport
2021-03-04 15:53     ` Peter Xu
2021-03-04  9:22   ` Alejandro Colomar (man-pages)
2021-03-04 15:50     ` Peter Xu
2021-03-04 18:13       ` Alejandro Colomar (man-pages)
2021-03-04  1:59 ` [PATCH 2/4] userfaultfd.2: Add write-protect mode Peter Xu
2021-03-04  6:46   ` Mike Rapoport
2021-03-04 16:02     ` Peter Xu
2021-03-04  1:59 ` [PATCH 3/4] ioctl_userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Peter Xu
2021-03-04  1:59 ` Peter Xu [this message]
2021-03-04 16:12   ` [PATCH 4/4] ioctl_userfaultfd.2: Add write-protect mode docs Peter Xu

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