mirror of https://github.com/mkerrisk/man-pages
104 lines
3.2 KiB
Groff
104 lines
3.2 KiB
Groff
.\" Copyright (C) 2003 John Levon <levon@movementarian.org>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" Modified 2004-06-17 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.TH LOOKUP_DCOOKIE 2 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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lookup_dcookie \- return a directory entry's path
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.SH SYNOPSIS
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.nf
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.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
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.B #include <unistd.h>
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.PP
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.BI "int syscall(SYS_lookup_dcookie, uint64_t " cookie ", char *" buffer ,
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.BI " size_t " len );
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.fi
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.PP
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.IR Note :
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glibc provides no wrapper for
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.BR lookup_dcookie (),
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necessitating the use of
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.BR syscall (2).
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.SH DESCRIPTION
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Look up the full path of the directory entry specified by the value
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.IR cookie .
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The cookie is an opaque identifier uniquely identifying a particular
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directory entry.
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The buffer given is filled in with the full path of the directory entry.
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.PP
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For
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.BR lookup_dcookie ()
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to return successfully,
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the kernel must still hold a cookie reference to the directory entry.
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.SH RETURN VALUE
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On success,
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.BR lookup_dcookie ()
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returns the length of the path string copied into the buffer.
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On error, \-1 is returned, and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EFAULT
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The buffer was not valid.
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.TP
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.B EINVAL
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The kernel has no registered cookie/directory entry mappings at the
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time of lookup, or the cookie does not refer to a valid directory entry.
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.TP
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.B ENAMETOOLONG
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The name could not fit in the buffer.
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.TP
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.B ENOMEM
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The kernel could not allocate memory for the temporary buffer holding
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the path.
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.TP
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.B EPERM
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The process does not have the capability
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.B CAP_SYS_ADMIN
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required to look up cookie values.
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.TP
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.B ERANGE
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The buffer was not large enough to hold the path of the directory entry.
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.SH VERSIONS
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Available since Linux 2.5.43.
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The
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.B ENAMETOOLONG
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error return was added in 2.5.70.
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.SH CONFORMING TO
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.BR lookup_dcookie ()
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is Linux-specific.
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.SH NOTES
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.BR lookup_dcookie ()
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is a special-purpose system call, currently used only by the
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.BR oprofile (1)
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profiler.
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It relies on a kernel driver to register cookies for directory entries.
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.PP
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The path returned may be suffixed by the string " (deleted)" if the directory
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entry has been removed.
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.SH SEE ALSO
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.BR oprofile (1)
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