lookup_dcookie(2) — Linux manual page


LOOKUP_DCOOKIE(2)       Linux Programmer's Manual      LOOKUP_DCOOKIE(2)

NAME         top

       lookup_dcookie - return a directory entry's path

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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.

VERSIONS         top

       Available since Linux 2.5.43.  The ENAMETOOLONG error return was
       added in 2.5.70.

CONFORMING TO         top

       lookup_dcookie() is Linux-specific.

NOTES         top

       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         top


COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

Linux                          2021-03-22              LOOKUP_DCOOKIE(2)

Pages that refer to this page: syscalls(2)capabilities(7)