[PATCH 18/21] userfaultfd: UFFDIO_REMAP uABI

[Andrea Arcangeli]

This implements the uABI of UFFDIO_REMAP.

Notably one mode bitflag is also forwarded (and in turn known) by the
lowlevel remap_pages method.

Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
 include/uapi/linux/userfaultfd.h | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 61251e6..db6e99a 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -19,7 +19,8 @@
 #define UFFD_API_RANGE_IOCTLS			\
 	((__u64)1 << _UFFDIO_WAKE |		\
 	 (__u64)1 << _UFFDIO_COPY |		\
-	 (__u64)1 << _UFFDIO_ZEROPAGE)
+	 (__u64)1 << _UFFDIO_ZEROPAGE |		\
+	 (__u64)1 << _UFFDIO_REMAP)
 
 /*
  * Valid ioctl command number range with this API is from 0x00 to
@@ -34,6 +35,7 @@
 #define _UFFDIO_WAKE			(0x02)
 #define _UFFDIO_COPY			(0x03)
 #define _UFFDIO_ZEROPAGE		(0x04)
+#define _UFFDIO_REMAP			(0x05)
 #define _UFFDIO_API			(0x3F)
 
 /* userfaultfd ioctl ids */
@@ -50,6 +52,8 @@
 				      struct uffdio_copy)
 #define UFFDIO_ZEROPAGE		_IOWR(UFFDIO, _UFFDIO_ZEROPAGE,	\
 				      struct uffdio_zeropage)
+#define UFFDIO_REMAP		_IOWR(UFFDIO, _UFFDIO_REMAP,	\
+				      struct uffdio_remap)
 
 /*
  * Valid bits below PAGE_SHIFT in the userfault address read through
@@ -122,4 +126,25 @@ struct uffdio_zeropage {
 	__s64 wake;
 };
 
+struct uffdio_remap {
+	__u64 dst;
+	__u64 src;
+	__u64 len;
+	/*
+	 * Especially if used to atomically remove memory from the
+	 * address space the wake on the dst range is not needed.
+	 */
+#define UFFDIO_REMAP_MODE_DONTWAKE		((__u64)1<<0)
+#define UFFDIO_REMAP_MODE_ALLOW_SRC_HOLES	((__u64)1<<1)
+	__u64 mode;
+
+	/*
+	 * "remap" and "wake" are written by the ioctl and must be at
+	 * the end: the copy_from_user will not read the last 16
+	 * bytes.
+	 */
+	__s64 remap;
+	__s64 wake;
+};
+
 #endif /* _LINUX_USERFAULTFD_H */
--
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