userfaultfd.2: Expand description of UFFDIO_UNREGISTER

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index 99860b35d4a103313d8441166cb3ccc1917bb722..f7dc53240ad61c942c3875d2f4a6c947f50c4a65 100644 (file)
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2
@@ -205,7 +205,36 @@ field.
 .\"
 .TP
 .BI "UFFDIO_UNREGISTER struct uffdio_register *" argp
-Unregister a memory range from userfaultfd.
+Unregister a memory address range from userfaultfd.
+The address range to unregister is specified in the
+.IR uffdio_range
+structure pointed to by
+.IR argp .
+
+This
+.BR ioctl (2)
+operation returns 0 on success.
+On error, \-1 is returned and
+.I errno
+is set to indicate the cause of the error.
+Possible errors include:
+.RS
+.TP
+.B EINVAL
+Either the
+.I start
+or the
+.I len
+field of the
+.I ufdio_range
+structure was not a multiple of the system page size.
+.TP
+.B EINVAL
+There as an incompatible mapping in the specified address range.
+.TP
+.B EINVAL
+There was no mapping in the specified address range.
+.RE
 .\"
 .SS Range ioctl(2) operations
 The range