Userfaultfd write-protect mode is supported starting from Linux 5.7.
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
man2/ioctl_userfaultfd.2 | 76 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 73 insertions(+), 3 deletions(-)
diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
index b58983fe7..7497e63c4 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 +445,11 @@ 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
+Do not set write permission when copying the page. The next write to the page
+will trigger a write fault. This can be used in conjunction with write-protect
+mode so that there will be another message generated when the page is written again.
.PP
The
.I copy
@@ -654,6 +661,69 @@ 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
