lookup_dcookie(2)

1lookup_dcookie(2)             System Calls Manual            lookup_dcookie(2)
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NAME

6       lookup_dcookie - return a directory entry's path
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <sys/syscall.h>      /* Definition of SYS_* constants */
13       #include <unistd.h>
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15       int syscall(SYS_lookup_dcookie, uint64_t cookie, char *buffer,
16                   size_t len);
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18       Note: glibc provides no wrapper for lookup_dcookie(), necessitating the
19       use of syscall(2).
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DESCRIPTION

22       Look up the full path of the directory entry  specified  by  the  value
23       cookie.  The cookie is an opaque identifier uniquely identifying a par‐
24       ticular directory entry.  The buffer given is filled in with  the  full
25       path of the directory entry.
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27       For lookup_dcookie() to return successfully, the kernel must still hold
28       a cookie reference to the directory entry.
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RETURN VALUE

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

36       EFAULT The buffer was not valid.
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38       EINVAL The kernel has no registered cookie/directory entry mappings  at
39              the  time of lookup, or the cookie does not refer to a valid di‐
40              rectory entry.
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42       ENAMETOOLONG
43              The name could not fit in the buffer.
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45       ENOMEM The kernel could not allocate memory for  the  temporary  buffer
46              holding the path.
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48       EPERM  The  process does not have the capability CAP_SYS_ADMIN required
49              to look up cookie values.
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51       ERANGE The buffer was not large enough to hold the path of  the  direc‐
52              tory entry.
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STANDARDS

55       Linux.
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HISTORY

58       Linux 2.5.43.
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60       The ENAMETOOLONG error was added in Linux 2.5.70.
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NOTES

63       lookup_dcookie()  is a special-purpose system call, currently used only
64       by the oprofile(1) profiler.  It relies on a kernel driver to  register
65       cookies for directory entries.
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67       The path returned may be suffixed by the string " (deleted)" if the di‐
68       rectory entry has been removed.
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