NAME

       lookup_dcookie - return a directory entry's path

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_lookup_dcookie, uint64_t cookie, char *buffer,
                   size_t len);

       Note: glibc provides no wrapper for lookup_dcookie(), necessitating the use of syscall(2).

DESCRIPTION

       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.

RETURN VALUE

       On success, lookup_dcookie() returns the length of the path string copied into the buffer.
       On error, -1 is returned, and errno is set to indicate the error.

ERRORS

       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.

       ENAMETOOLONG
              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.

STANDARDS

       Linux.

HISTORY

       Linux 2.5.43.

       The ENAMETOOLONG error was added in Linux 2.5.70.

NOTES

       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.

SEE ALSO

       oprofile(1)