1.\" $NetBSD: pathbuf.9,v 1.2 2010/11/30 10:32:46 dholland Exp $ 2.\" 3.\" Copyright (c) 2010 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by David A. Holland. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd November 30, 2010 31.Dt PATHBUF 9 32.Os 33.Sh NAME 34.Nm pathbuf , 35.Nm pathbuf_create , 36.Nm pathbuf_assimilate , 37.Nm pathbuf_copyin , 38.Nm pathbuf_destroy 39.Nd path buffer abstraction 40.Sh SYNOPSIS 41.In sys/namei.h 42.Ft struct pathbuf * 43.Fn pathbuf_create "const char *path" 44.Ft struct pathbuf * 45.Fn pathbuf_assimilate "char *pnbuf" 46.Ft int 47.Fn pathbuf_copyin "const char *userpath" "struct pathbuf **ret" 48.Ft void 49.Fn pathbuf_destroy "struct pathbuf *path" 50.Sh DESCRIPTION 51The 52.Nm 53interface is used to carry around pathnames. 54This helps simplify the 55.Xr namei 9 56interface. 57A pathbuf should be thought of as a path name string combined with 58whatever flags and metadata are needed to interpret it correctly. 59It is an abstract type; the internals are hidden within the 60.Xr namei 9 61implementation. 62.Pp 63The 64.Fn pathbuf_create 65function allocates and initializes a new pathbuf containing a copy of 66the path string 67.Fa path , 68which should be a kernel pointer. 69The return value should be checked for being 70.Dv NULL 71in case the system is out of memory. 72Passing a path name larger than 73.Dv PATH_MAX 74will cause an assertion failure. 75.Pp 76The 77.Fn pathbuf_copyin 78function allocates and initializes a new pathbuf containing a path 79string copied from user space with 80.Xr copyinstr 9 . 81It returns an error code. 82.Pp 83The 84.Fn pathbuf_assimilate 85function creates a pathbuf using the string buffer provided as 86.Fa pnbuf . 87This buffer must be of size 88.Dv PATH_MAX 89and must have been allocated with 90.Fn PNBUF_GET . 91The buffer is 92.Dq taken over 93by the returned pathbuf and will be released when the pathbuf is 94destroyed. 95Note: to avoid confusion and pointer bugs, 96.Fn pathbuf_assimilate 97should only be used where absolutely necessary; e.g. the NFS server 98code uses it to generate pathbufs from strings fetched from mbufs. 99.Pp 100The 101.Fn pathbuf_destroy 102function deallocates a pathbuf. 103Caution: because calling 104.Xr namei 9 105loads pointers to memory belonging to the pathbuf into the nameidata 106structure, a pathbuf should only be destroyed by the 107.Fn namei 108caller once all manipulations of the nameidata are complete. 109.Pp 110Also note that calling 111.Fn namei 112destroys the contents of the pathbuf. 113Do not reuse a pathbuf for a second call to 114.Fn namei . 115.Sh CODE REFERENCES 116The 117.Nm 118code is part of the name lookup code in 119.Pa sys/kern/vfs_lookup.c . 120.Sh SEE ALSO 121.Xr namei 9 122.Sh BUGS 123There are cases where it is necessary to get the path string left 124behind after 125.Fn namei 126has run. 127This produces an effect similar to 128.Xr realpath 3 . 129The interface for doing this is, for the time being, intentionally 130undocumented and subject to change. 131