Initial Spring 2016 commit.

kern/vfs/vfslookup.c

@@ -0,0 +1,293 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * 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. 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 UNIVERSITY 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 UNIVERSITY 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.
+ */
+
+/*
+ * VFS operations relating to pathname translation
+ */
+
+#include <types.h>
+#include <kern/errno.h>
+#include <limits.h>
+#include <lib.h>
+#include <synch.h>
+#include <vfs.h>
+#include <fs.h>
+#include <vnode.h>
+
+static struct vnode *bootfs_vnode = NULL;
+
+/*
+ * Helper function for actually changing bootfs_vnode.
+ */
+static
+void
+change_bootfs(struct vnode *newvn)
+{
+	struct vnode *oldvn;
+
+	oldvn = bootfs_vnode;
+	bootfs_vnode = newvn;
+
+	if (oldvn != NULL) {
+		VOP_DECREF(oldvn);
+	}
+}
+
+/*
+ * Set bootfs_vnode.
+ *
+ * Bootfs_vnode is the vnode used for beginning path translation of
+ * pathnames starting with /.
+ *
+ * It is also incidentally the system's first current directory.
+ */
+int
+vfs_setbootfs(const char *fsname)
+{
+	char tmp[NAME_MAX+1];
+	char *s;
+	int result;
+	struct vnode *newguy;
+
+	vfs_biglock_acquire();
+
+	snprintf(tmp, sizeof(tmp)-1, "%s", fsname);
+	s = strchr(tmp, ':');
+	if (s) {
+		/* If there's a colon, it must be at the end */
+		if (strlen(s)>0) {
+			vfs_biglock_release();
+			return EINVAL;
+		}
+	}
+	else {
+		strcat(tmp, ":");
+	}
+
+	result = vfs_chdir(tmp);
+	if (result) {
+		vfs_biglock_release();
+		return result;
+	}
+
+	result = vfs_getcurdir(&newguy);
+	if (result) {
+		vfs_biglock_release();
+		return result;
+	}
+
+	change_bootfs(newguy);
+
+	vfs_biglock_release();
+	return 0;
+}
+
+/*
+ * Clear the bootfs vnode (preparatory to system shutdown).
+ */
+void
+vfs_clearbootfs(void)
+{
+	vfs_biglock_acquire();
+	change_bootfs(NULL);
+	vfs_biglock_release();
+}
+
+
+/*
+ * Common code to pull the device name, if any, off the front of a
+ * path and choose the vnode to begin the name lookup relative to.
+ */
+
+static
+int
+getdevice(char *path, char **subpath, struct vnode **startvn)
+{
+	int slash=-1, colon=-1, i;
+	struct vnode *vn;
+	int result;
+
+	KASSERT(vfs_biglock_do_i_hold());
+
+	/*
+	 * Locate the first colon or slash.
+	 */
+
+	for (i=0; path[i]; i++) {
+		if (path[i]==':') {
+			colon = i;
+			break;
+		}
+		if (path[i]=='/') {
+			slash = i;
+			break;
+		}
+	}
+
+	if (colon < 0 && slash != 0) {
+		/*
+		 * No colon before a slash, so no device name
+		 * specified, and the slash isn't leading or is also
+		 * absent, so this is a relative path or just a bare
+		 * filename. Start from the current directory, and
+		 * use the whole thing as the subpath.
+		 */
+		*subpath = path;
+		return vfs_getcurdir(startvn);
+	}
+
+	if (colon>0) {
+		/* device:path - get root of device's filesystem */
+		path[colon]=0;
+		while (path[colon+1]=='/') {
+			/* device:/path - skip slash, treat as device:path */
+			colon++;
+		}
+		*subpath = &path[colon+1];
+
+		result = vfs_getroot(path, startvn);
+		if (result) {
+			return result;
+		}
+
+		return 0;
+	}
+
+	/*
+	 * We have either /path or :path.
+	 *
+	 * /path is a path relative to the root of the "boot filesystem".
+	 * :path is a path relative to the root of the current filesystem.
+	 */
+	KASSERT(colon==0 || slash==0);
+
+	if (path[0]=='/') {
+		if (bootfs_vnode==NULL) {
+			return ENOENT;
+		}
+		VOP_INCREF(bootfs_vnode);
+		*startvn = bootfs_vnode;
+	}
+	else {
+		KASSERT(path[0]==':');
+
+		result = vfs_getcurdir(&vn);
+		if (result) {
+			return result;
+		}
+
+		/*
+		 * The current directory may not be a device, so it
+		 * must have a fs.
+		 */
+		KASSERT(vn->vn_fs!=NULL);
+
+		result = FSOP_GETROOT(vn->vn_fs, startvn);
+
+		VOP_DECREF(vn);
+
+		if (result) {
+			return result;
+		}
+	}
+
+	while (path[1]=='/') {
+		/* ///... or :/... */
+		path++;
+	}
+
+	*subpath = path+1;
+
+	return 0;
+}
+
+/*
+ * Name-to-vnode translation.
+ * (In BSD, both of these are subsumed by namei().)
+ */
+
+int
+vfs_lookparent(char *path, struct vnode **retval,
+	       char *buf, size_t buflen)
+{
+	struct vnode *startvn;
+	int result;
+
+	vfs_biglock_acquire();
+
+	result = getdevice(path, &path, &startvn);
+	if (result) {
+		vfs_biglock_release();
+		return result;
+	}
+
+	if (strlen(path)==0) {
+		/*
+		 * It does not make sense to use just a device name in
+		 * a context where "lookparent" is the desired
+		 * operation.
+		 */
+		result = EINVAL;
+	}
+	else {
+		result = VOP_LOOKPARENT(startvn, path, retval, buf, buflen);
+	}
+
+	VOP_DECREF(startvn);
+
+	vfs_biglock_release();
+	return result;
+}
+
+int
+vfs_lookup(char *path, struct vnode **retval)
+{
+	struct vnode *startvn;
+	int result;
+
+	vfs_biglock_acquire();
+
+	result = getdevice(path, &path, &startvn);
+	if (result) {
+		vfs_biglock_release();
+		return result;
+	}
+
+	if (strlen(path)==0) {
+		*retval = startvn;
+		vfs_biglock_release();
+		return 0;
+	}
+
+	result = VOP_LOOKUP(startvn, path, retval);
+
+	VOP_DECREF(startvn);
+	vfs_biglock_release();
+	return result;
+}