fuse: implement ioctl support

Generic ioctl support is tricky to implement because only the ioctl
implementation itself knows which memory regions need to be read
and/or written.  To support this, fuse client can request retry of
ioctl specifying memory regions to read and write.  Deep copying
(nested pointers) can be implemented by retrying multiple times
resolving one depth of dereference at a time.

For security and cleanliness considerations, ioctl implementation has
restricted mode where the kernel determines data transfer directions
and sizes using the _IOC_*() macros on the ioctl command.  In this
mode, retry is not allowed.

For all FUSE servers, restricted mode is enforced.  Unrestricted ioctl
will be used by CUSE.

Plese read the comment on top of fs/fuse/file.c::fuse_file_do_ioctl()
for more information.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 32 insertions, 0 deletions

diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 7caa473..608e300 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -148,6 +148,21 @@ struct fuse_file_lock {
  */
 #define FUSE_READ_LOCKOWNER	(1 << 1)
 
+/**
+ * Ioctl flags
+ *
+ * FUSE_IOCTL_COMPAT: 32bit compat ioctl on 64bit machine
+ * FUSE_IOCTL_UNRESTRICTED: not restricted to well-formed ioctls, retry allowed
+ * FUSE_IOCTL_RETRY: retry with new iovecs
+ *
+ * FUSE_IOCTL_MAX_IOV: maximum of in_iovecs + out_iovecs
+ */
+#define FUSE_IOCTL_COMPAT	(1 << 0)
+#define FUSE_IOCTL_UNRESTRICTED	(1 << 1)
+#define FUSE_IOCTL_RETRY	(1 << 2)
+
+#define FUSE_IOCTL_MAX_IOV	256
+
 enum fuse_opcode {
 	FUSE_LOOKUP	   = 1,
 	FUSE_FORGET	   = 2,  /* no reply */
@@ -185,6 +200,7 @@ enum fuse_opcode {
 	FUSE_INTERRUPT     = 36,
 	FUSE_BMAP          = 37,
 	FUSE_DESTROY       = 38,
+	FUSE_IOCTL         = 39,
 };
 
 /* The read buffer is required to be at least 8k, but may be much larger */
@@ -385,6 +401,22 @@ struct fuse_bmap_out {
 	__u64	block;
 };
 
+struct fuse_ioctl_in {
+	__u64	fh;
+	__u32	flags;
+	__u32	cmd;
+	__u64	arg;
+	__u32	in_size;
+	__u32	out_size;
+};
+
+struct fuse_ioctl_out {
+	__s32	result;
+	__u32	flags;
+	__u32	in_iovs;
+	__u32	out_iovs;
+};
+
 struct fuse_in_header {
 	__u32	len;
 	__u32	opcode;