lookup_dcookie - Man Page
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)