Section 2 · System calls

lookup_dcookie.2

Package: man-pages

lookup_dcookie

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
STANDARDS
HISTORY
NOTES
SEE ALSO

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.