lookup_dcookie(2)             System Calls Manual            lookup_dcookie(2)

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)

Linux man-pages 6.7               2023-10-31                 lookup_dcookie(2)