Fix pointer-is-uint64_t-sized assumption in the ioctl path

This shows up when compiling freebsd-head on amd64 using gcc-6.4.
The lib32 compat build ends up tripping over this assumption.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: adrian chadd <[email protected]>
Closes openzfs#11068
Closes openzfs#11069

Author: Adrian Chadd

lib/libzutil/os/freebsd/zutil_compat.c

@@ -55,7 +55,7 @@ zcmd_ioctl_compat(int fd, int request, zfs_cmd_t *zc, const int cflag)
 	switch (cflag) {
 	case ZFS_CMD_COMPAT_NONE:
 		ncmd = _IOWR('Z', request, zfs_iocparm_t);
-		zp.zfs_cmd = (uint64_t)zc;
+		zp.zfs_cmd = (uint64_t)(uintptr_t)zc;
 		zp.zfs_cmd_size = sizeof (zfs_cmd_t);
 		zp.zfs_ioctl_version = ZFS_IOCVER_OZFS;
 		break;
@@ -64,7 +64,7 @@ zcmd_ioctl_compat(int fd, int request, zfs_cmd_t *zc, const int cflag)
 		ncmd = _IOWR('Z', newrequest, zfs_iocparm_t);
 		zc_c = malloc(sizeof (zfs_cmd_legacy_t));
 		zfs_cmd_ozfs_to_legacy(zc, zc_c);
-		zp.zfs_cmd = (uint64_t)zc_c;
+		zp.zfs_cmd = (uint64_t)(uintptr_t)zc_c;
 		zp.zfs_cmd_size = sizeof (zfs_cmd_legacy_t);
 		zp.zfs_ioctl_version = ZFS_IOCVER_LEGACY;
 		break;