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 par-
ticular 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
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
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 direc-
Available since Linux 2.5.43. The ENAMETOOLONG error return was added
lookup_dcookie() is Linux-specific.
lookup_dcookie() is a special-purpose system call, currently used only
by the oprofile 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.
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