In order to produce useful profiles, we need to be able to associate a particular PC value sample with an actual ELF binary on the disk. This leaves us with the problem of how to export this information to user-space. We create unique IDs that identify a particular directory entry (dentry), and write those IDs into the event buffer. Later on, the user-space daemon can call the lookup_dcookie system call, which looks up the ID and fills in the full path of the binary image in the buffer user-space passes in. These IDs are maintained by the code in fs/dcookies.c; the cache lasts for as long as the daemon has the event buffer open.