lookup_dcookie - return a directory entry’s path
int lookup_dcookie(u64 cookie, char *buffer, size_t len);
Look up the full path of the directory entry specified by the value cookie. The cookie is an opaque identifier uniquely identifying a particular directory entry. The buffer given is filled in with the full path of the directory entry.
For lookup_dcookie() to return successfully, the kernel must still hold a cookie reference to the directory entry.
On success, lookup_dcookie() returns the length of the path string copied into the buffer. On error, -1 is returned, and errno is set appropriately.
|EFAULT||The buffer was not valid.|
|EINVAL||The kernel has no registered cookie/directory entry mappings at the time of lookup, or the cookie does not refer to a valid directory entry.|
|The name could not fit in the buffer.|
|ENOMEM||The kernel could not allocate memory for the temporary buffer holding the path.|
|EPERM||The process does not have the capability CAP_SYS_ADMIN required to look up cookie values.|
|ERANGE||The buffer was not large enough to hold the path of the directory entry.|
Available since Linux 2.5.43. The ENAMETOOLONG error return was added in 2.5.70.
lookup_dcookie() is Linux-specific.
lookup_dcookie() is a special-purpose system call, currently used only by the oprofile(1) profiler. It relies on a kernel driver to register cookies for directory entries.
The path returned may be suffixed by the string " (deleted)" if the directory entry has been removed.