userfaultfd-sys: expose USERFAULTFD_IOC ioctl number

Expose the USERFAULTFD_IOC ioctl number for `/dev/userfaultfd` device.
This device is only present on kernels >= 6.1, but we expose it
unconditionally so that userfaultfd-sys has the same exports for all
kernels.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

userfaultfd-sys/src/consts.c

@@ -69,3 +69,7 @@ const __u32 _const_UFFDIO_ZEROPAGE = UFFDIO_ZEROPAGE;
 #ifdef UFFDIO_WRITEPROTECT
 const __u32 _const_UFFDIO_WRITEPROTECT = UFFDIO_WRITEPROTECT;
 #endif
+
+#ifdef USERFAULTFD_IOC
+const __u32 _const_USERFAULTFD_IOC = USERFAULTFD_IOC;
+#endif

userfaultfd-sys/wrapper.h

@@ -4,3 +4,9 @@
 // userfaultfd-sys has the same exports on all kernels
 #define UFFD_USER_MODE_ONLY 1
 #endif
+
+
+#ifndef USERFAULTFD_IOC
+// Similarly, the ioctl() for `/dev/userfaultfd` is introduced with Linux 6.1.
+#define USERFAULTFD_IOC 0xAA
+#endif