initial import of NetBSD tree

3 files changed, 359 insertions, 0 deletions

diff --git a/sbin/mount_null/Makefile b/sbin/mount_null/Makefile
new file mode 100644
index 00000000000..e2070c61474
--- /dev/null
+++ b/sbin/mount_null/Makefile
@@ -0,0 +1,12 @@
+#	$NetBSD: Makefile,v 1.5 1995/03/18 14:57:45 cgd Exp $
+#	@(#)Makefile	8.3 (Berkeley) 3/27/94
+
+PROG=	mount_null
+SRCS=	mount_null.c getmntopts.c
+MAN=	mount_null.8
+
+MOUNT=	${.CURDIR}/../mount
+CFLAGS+= -I${.CURDIR}/../../sys -I${MOUNT}
+.PATH:	${MOUNT}
+
+.include <bsd.prog.mk>
diff --git a/sbin/mount_null/mount_null.8 b/sbin/mount_null/mount_null.8
new file mode 100644
index 00000000000..7c403407378
--- /dev/null
+++ b/sbin/mount_null/mount_null.8
@@ -0,0 +1,212 @@
+.\"	$NetBSD: mount_null.8,v 1.3 1995/07/12 07:08:27 cgd Exp $
+.\"
+.\" Copyright (c) 1992, 1993, 1994
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" This code is derived from software donated to Berkeley by
+.\" John Heidemann of the UCLA Ficus project.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)mount_null.8	8.4 (Berkeley) 4/19/94
+.\"
+.Dd April 19, 1994
+.Dt MOUNT_NULL 8
+.Os BSD 4.4
+.Sh NAME
+.Nm mount_null
+.Nd demonstrate the use of a null file system layer
+.Sh SYNOPSIS
+.Nm mount_null
+.Op Fl o Ar options
+.Ar target
+.Ar mount-point
+.Sh DESCRIPTION
+The
+.Nm mount_null
+command creates a
+null layer, duplicating a sub-tree of the file system
+name space under another part of the global file system namespace.
+It is implemented using a stackable layers technique, and its
+.Do
+null-nodes
+.Dc
+stack above
+all lower-layer vnodes (not just above directory vnodes).
+.Pp
+The options are as follows:
+.Bl -tag -width indent
+.It Fl o
+Options are specified with a
+.Fl o
+flag followed by a comma separated string of options.
+See the
+.Xr mount 8
+man page for possible options and their meanings.
+.El
+.Pp
+The null layer has two purposes.
+First, it serves as a demonstration of layering by proving a layer
+which does nothing.
+Second, the null layer can serve as a prototype layer.
+Since it provides all necessary layer framework,
+new file system layers can be created very easily be starting
+with a null layer.
+.Pp
+The remainder of this man page examines the null layer as a basis
+for constructing new layers.
+.\"
+.\"
+.Sh INSTANTIATING NEW NULL LAYERS
+New null layers are created with 
+.Xr mount_null 8 .
+.Xr Mount_null 8
+takes two arguments, the pathname
+of the lower vfs (target-pn) and the pathname where the null
+layer will appear in the namespace (mount-point-pn).  After
+the null layer is put into place, the contents
+of target-pn subtree will be aliased under mount-point-pn.
+.\"
+.\"
+.Sh OPERATION OF A NULL LAYER
+The null layer is the minimum file system layer,
+simply bypassing all possible operations to the lower layer
+for processing there.  The majority of its activity centers
+on the bypass routine, though which nearly all vnode operations
+pass.
+.Pp
+The bypass routine accepts arbitrary vnode operations for
+handling by the lower layer.  It begins by examing vnode
+operation arguments and replacing any null-nodes by their
+lower-layer equivalents.  It then invokes the operation
+on the lower layer.  Finally, it replaces the null-nodes
+in the arguments and, if a vnode is returned by the operation,
+stacks a null-node on top of the returned vnode.
+.Pp
+Although bypass handles most operations, 
+.Em vop_getattr , 
+.Em vop_inactive ,
+.Em vop_reclaim ,
+and
+.Em vop_print
+are not bypassed.
+.Em Vop_getattr
+must change the fsid being returned.
+.Em Vop_inactive
+and vop_reclaim are not bypassed so that
+they can handle freeing null-layer specific data.
+.Em Vop_print
+is not bypassed to avoid excessive debugging
+information.
+.\"
+.\"
+.Sh INSTANTIATING VNODE STACKS
+Mounting associates the null layer with a lower layer,
+in effect stacking two VFSes.  Vnode stacks are instead
+created on demand as files are accessed.
+.Pp
+The initial mount creates a single vnode stack for the
+root of the new null layer.  All other vnode stacks
+are created as a result of vnode operations on
+this or other null vnode stacks.
+.Pp
+New vnode stacks come into existence as a result of
+an operation which returns a vnode.  
+The bypass routine stacks a null-node above the new
+vnode before returning it to the caller.
+.Pp
+For example, imagine mounting a null layer with
+.Bd -literal -offset indent
+mount_null /usr/include /dev/layer/null
+.Ed
+Changing directory to 
+.Pa /dev/layer/null
+will assign
+the root null-node (which was created when the null layer was mounted).
+Now consider opening 
+.Pa sys .
+A vop_lookup would be
+done on the root null-node.  This operation would bypass through
+to the lower layer which would return a vnode representing 
+the UFS 
+.Pa sys .
+Null_bypass then builds a null-node
+aliasing the UFS 
+.Pa sys
+and returns this to the caller.
+Later operations on the null-node 
+.Pa sys
+will repeat this 
+process when constructing other vnode stacks.
+.\"
+.\"
+.Sh CREATING OTHER FILE SYSTEM LAYERS
+One of the easiest ways to construct new file system layers is to make
+a copy of the null layer, rename all files and variables, and
+then begin modifyng the copy.  Sed can be used to easily rename
+all variables.
+.Pp
+The umap layer is an example of a layer descended from the 
+null layer.
+.\"
+.\"
+.Sh INVOKING OPERATIONS ON LOWER LAYERS
+There are two techniques to invoke operations on a lower layer 
+when the operation cannot be completely bypassed.  Each method
+is appropriate in different situations.  In both cases,
+it is the responsibility of the aliasing layer to make
+the operation arguments "correct" for the lower layer
+by mapping an vnode arguments to the lower layer.
+.Pp
+The first approach is to call the aliasing layer's bypass routine.
+This method is most suitable when you wish to invoke the operation
+currently being handled on the lower layer.  It has the advantage
+the the bypass routine already must do argument mapping.
+An example of this is 
+.Em null_getattrs
+in the null layer.
+.Pp
+A second approach is to directly invoked vnode operations on
+the lower layer with the
+.Em VOP_OPERATIONNAME
+interface.
+The advantage of this method is that it is easy to invoke
+arbitrary operations on the lower layer.  The disadvantage
+is that vnodes arguments must be manually mapped.
+.\"
+.\"
+.Sh SEE ALSO
+.Xr mount 8
+.sp
+UCLA Technical Report CSD-910056,
+.Em "Stackable Layers: an Architecture for File System Development" .
+.Sh HISTORY
+The
+.Nm mount_null
+utility first appeared in 4.4BSD.
diff --git a/sbin/mount_null/mount_null.c b/sbin/mount_null/mount_null.c
new file mode 100644
index 00000000000..12f4ed8706d
--- /dev/null
+++ b/sbin/mount_null/mount_null.c
@@ -0,0 +1,135 @@
+/*	$NetBSD: mount_null.c,v 1.2 1995/03/18 14:57:48 cgd Exp $	*/
+
+/*
+ * Copyright (c) 1992, 1993, 1994
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software donated to Berkeley by
+ * Jan-Simon Pendry.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef lint
+char copyright[] =
+"@(#) Copyright (c) 1992, 1993, 1994\n\
+	The Regents of the University of California.  All rights reserved.\n";
+#endif /* not lint */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)mount_null.c	8.5 (Berkeley) 3/27/94";
+#else
+static char rcsid[] = "$NetBSD: mount_null.c,v 1.2 1995/03/18 14:57:48 cgd Exp $";
+#endif
+#endif /* not lint */
+
+#include <sys/param.h>
+#include <sys/mount.h>
+#include <miscfs/nullfs/null.h>
+
+#include <err.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "mntopts.h"
+
+struct mntopt mopts[] = {
+	MOPT_STDOPTS,
+	{ NULL }
+};
+
+int	subdir __P((const char *, const char *));
+void	usage __P((void));
+
+int
+main(argc, argv)
+	int argc;
+	char *argv[];
+{
+	struct null_args args;
+	int ch, mntflags;
+	char target[MAXPATHLEN];
+
+	mntflags = 0;
+	while ((ch = getopt(argc, argv, "o:")) != EOF)
+		switch(ch) {
+		case 'o':
+			getmntopts(optarg, mopts, &mntflags);
+			break;
+		case '?':
+		default:
+			usage();
+		}
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 2)
+		usage();
+
+	if (realpath(argv[0], target) == 0)
+		err(1, "%s", target);
+
+	if (subdir(target, argv[1]) || subdir(argv[1], target))
+		errx(1, "%s (%s) and %s are not distinct paths",
+		    argv[0], target, argv[1]);
+
+	args.target = target;
+
+	if (mount(MOUNT_NULL, argv[1], mntflags, &args))
+		err(1, NULL);
+	exit(0);
+}
+
+int
+subdir(p, dir)
+	const char *p;
+	const char *dir;
+{
+	int l;
+
+	l = strlen(dir);
+	if (l <= 1)
+		return (1);
+
+	if ((strncmp(p, dir, l) == 0) && (p[l] == '/' || p[l] == '\0'))
+		return (1);
+
+	return (0);
+}
+
+void
+usage()
+{
+	(void)fprintf(stderr,
+		"usage: mount_null [-o options] target_fs mount_point\n");
+	exit(1);
+}