lookup_dcookie(2)

1LOOKUP_DCOOKIE(2)          Linux Programmer's Manual         LOOKUP_DCOOKIE(2)
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NAME

6       lookup_dcookie - return a directory entry's path
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SYNOPSIS

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

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

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

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

52       Available  since Linux 2.5.43.  The ENAMETOOLONG error return was added
53       in 2.5.70.
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CONFORMING TO

56       lookup_dcookie() is Linux-specific.
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NOTES

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

70       This  page  is  part of release 5.13 of the Linux man-pages project.  A
71       description of the project, information about reporting bugs,  and  the
72       latest     version     of     this    page,    can    be    found    at
73       https://www.kernel.org/doc/man-pages/.
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77Linux                             2021-03-22                 LOOKUP_DCOOKIE(2)