131 lines
4.1 KiB
Groff
131 lines
4.1 KiB
Groff
.\" $NetBSD: pathbuf.9,v 1.2 2010/11/30 10:32:46 dholland Exp $
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.\"
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.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by David A. Holland.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd November 30, 2010
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.Dt PATHBUF 9
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.Os
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.Sh NAME
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.Nm pathbuf ,
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.Nm pathbuf_create ,
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.Nm pathbuf_assimilate ,
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.Nm pathbuf_copyin ,
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.Nm pathbuf_destroy
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.Nd path buffer abstraction
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.Sh SYNOPSIS
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.In sys/namei.h
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.Ft struct pathbuf *
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.Fn pathbuf_create "const char *path"
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.Ft struct pathbuf *
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.Fn pathbuf_assimilate "char *pnbuf"
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.Ft int
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.Fn pathbuf_copyin "const char *userpath" "struct pathbuf **ret"
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.Ft void
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.Fn pathbuf_destroy "struct pathbuf *path"
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.Sh DESCRIPTION
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The
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.Nm
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interface is used to carry around pathnames.
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This helps simplify the
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.Xr namei 9
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interface.
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A pathbuf should be thought of as a path name string combined with
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whatever flags and metadata are needed to interpret it correctly.
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It is an abstract type; the internals are hidden within the
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.Xr namei 9
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implementation.
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.Pp
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The
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.Fn pathbuf_create
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function allocates and initializes a new pathbuf containing a copy of
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the path string
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.Fa path ,
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which should be a kernel pointer.
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The return value should be checked for being
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.Dv NULL
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in case the system is out of memory.
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Passing a path name larger than
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.Dv PATH_MAX
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will cause an assertion failure.
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.Pp
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The
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.Fn pathbuf_copyin
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function allocates and initializes a new pathbuf containing a path
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string copied from user space with
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.Xr copyinstr 9 .
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It returns an error code.
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.Pp
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The
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.Fn pathbuf_assimilate
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function creates a pathbuf using the string buffer provided as
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.Fa pnbuf .
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This buffer must be of size
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.Dv PATH_MAX
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and must have been allocated with
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.Fn PNBUF_GET .
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The buffer is
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.Dq taken over
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by the returned pathbuf and will be released when the pathbuf is
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destroyed.
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Note: to avoid confusion and pointer bugs,
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.Fn pathbuf_assimilate
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should only be used where absolutely necessary; e.g. the NFS server
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code uses it to generate pathbufs from strings fetched from mbufs.
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.Pp
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The
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.Fn pathbuf_destroy
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function deallocates a pathbuf.
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Caution: because calling
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.Xr namei 9
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loads pointers to memory belonging to the pathbuf into the nameidata
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structure, a pathbuf should only be destroyed by the
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.Fn namei
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caller once all manipulations of the nameidata are complete.
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.Pp
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Also note that calling
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.Fn namei
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destroys the contents of the pathbuf.
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Do not reuse a pathbuf for a second call to
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.Fn namei .
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.Sh CODE REFERENCES
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The
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.Nm
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code is part of the name lookup code in
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.Pa sys/kern/vfs_lookup.c .
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.Sh SEE ALSO
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.Xr namei 9
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.Sh BUGS
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There are cases where it is necessary to get the path string left
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behind after
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.Fn namei
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has run.
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This produces an effect similar to
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.Xr realpath 3 .
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The interface for doing this is, for the time being, intentionally
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undocumented and subject to change.
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