RDMA/uverbs: Add a method to introspect handles in a context

Introduce a helper function gather_objects_handle() to copy object handles
under a spin lock.

Expose these objects handles via the uverbs ioctl interface.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>

include/uapi/rdma/ib_user_ioctl_cmds.h

@@ -65,6 +65,7 @@ enum {
 
 enum uverbs_methods_device {
 	UVERBS_METHOD_INVOKE_WRITE,
+	UVERBS_METHOD_INFO_HANDLES,
 };
 
 enum uverbs_attrs_invoke_write_cmd_attr_ids {
@@ -167,4 +168,10 @@ enum uverbs_methods_actions_counters_ops {
 	UVERBS_METHOD_COUNTERS_READ,
 };
 
+enum uverbs_attrs_info_handles_id {
+	UVERBS_ATTR_INFO_OBJECT_ID,
+	UVERBS_ATTR_INFO_TOTAL_HANDLES,
+	UVERBS_ATTR_INFO_HANDLES_LIST,
+};
+
 #endif