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Subject[PATCH 1/2] userfaultfd.2: Add section for UFFD_USER_MODE_ONLY
Date
Add a paragraph for UFFD_USER_MODE_ONLY flag that was introduced in
Linux 5.11.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
man2/userfaultfd.2 | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index cee7c01d2..0928a76d2 100644
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2
@@ -29,8 +29,9 @@
userfaultfd \- create a file descriptor for handling page faults in user space
.SH SYNOPSIS
.nf
-.BR "#include <fcntl.h>" " /* Definition of " O_* " constants */"
-.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
+.BR "#include <fcntl.h>" " /* Definition of " O_* " constants */"
+.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
+.BR "#include <linux/userfaultfd.h>" " /* Definition of " UFFD_* " constants */"
.B #include <unistd.h>
.PP
.BI "int syscall(SYS_userfaultfd, int " flags );
@@ -76,6 +77,15 @@ See the description of the
.BR O_NONBLOCK
flag in
.BR open (2).
+.TP
+.BR UFFD_USER_MODE_ONLY
+This is an userfaultfd specific flag that was introduced since Linux 5.11.
+When set, the userfaultfd object will only be able to handle page faults
+originated from the userspace on the registered regions.
+When a kernel originated fault was triggered on the registered range with
+this userfaultfd, a
+.BR SIGBUS
+signal will be delivered.
.PP
When the last file descriptor referring to a userfaultfd object is closed,
all memory ranges that were registered with the object are unregistered
--
2.32.0
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