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- /****************************************************************************
- * fs/inode/fs_inodesearch.c
- *
- * Copyright (C) 2007-2009, 2011-2012, 2016-2017 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * 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 NuttX 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 COPYRIGHT HOLDERS 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
- * COPYRIGHT OWNER 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.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <stdio.h>
- #include <string.h>
- #include <limits.h>
- #include <assert.h>
- #include <errno.h>
- #include <nuttx/fs/fs.h>
- #include "inode/inode.h"
- /****************************************************************************
- * Private Function Prototypes
- ****************************************************************************/
- static int _inode_compare(FAR const char *fname, FAR struct inode *node);
- #ifdef CONFIG_PSEUDOFS_SOFTLINKS
- static int _inode_linktarget(FAR struct inode *node,
- FAR struct inode_search_s *desc);
- #endif
- static int _inode_search(FAR struct inode_search_s *desc);
- /****************************************************************************
- * Public Data
- ****************************************************************************/
- FAR struct inode *g_root_inode = NULL;
- /****************************************************************************
- * Private Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: _inode_compare
- *
- * Description:
- * Compare two inode names
- *
- ****************************************************************************/
- static int _inode_compare(FAR const char *fname, FAR struct inode *node)
- {
- char *nname = node->i_name;
- if (!nname)
- {
- return 1;
- }
- if (!fname)
- {
- return -1;
- }
- for (; ; )
- {
- /* At the end of the node name? */
- if (!*nname)
- {
- /* Yes.. also at the end of find name? */
- if (!*fname || *fname == '/')
- {
- /* Yes.. return match */
- return 0;
- }
- else
- {
- /* No... return find name > node name */
- return 1;
- }
- }
- /* At end of the find name? */
- else if (!*fname || *fname == '/')
- {
- /* Yes... return find name < node name */
- return -1;
- }
- /* Check for non-matching characters */
- else if (*fname > *nname)
- {
- return 1;
- }
- else if (*fname < *nname)
- {
- return -1;
- }
- /* Not at the end of either string and all of the
- * characters still match. keep looking.
- */
- else
- {
- fname++;
- nname++;
- }
- }
- }
- /****************************************************************************
- * Name: _inode_linktarget
- *
- * Description:
- * If the inode is a soft link, then (1) get the name of the full path of
- * the soft link, (2) recursively look-up the inode referenced by the soft
- * link, and (3) return the inode referenced by the soft link.
- *
- * Assumptions:
- * The caller holds the g_inode_sem semaphore
- *
- ****************************************************************************/
- #ifdef CONFIG_PSEUDOFS_SOFTLINKS
- static int _inode_linktarget(FAR struct inode *node,
- FAR struct inode_search_s *desc)
- {
- unsigned int count = 0;
- bool save;
- int ret = -ENOENT;
- DEBUGASSERT(desc != NULL && node != NULL);
- /* An infinite loop is avoided only by the loop count.
- *
- * REVISIT: The ELOOP error should be reported to the application in that
- * case but there is no simple mechanism to do that.
- */
- save = desc->nofollow;
- while (INODE_IS_SOFTLINK(node))
- {
- FAR const char *link = (FAR const char *)node->u.i_link;
- /* Reset and reinitialize the search descriptor. */
- RELEASE_SEARCH(desc);
- SETUP_SEARCH(desc, link, true);
- /* Look up inode associated with the target of the symbolic link */
- ret = _inode_search(desc);
- if (ret < 0)
- {
- break;
- }
- /* Limit the number of symbolic links that we pass through */
- if (++count > SYMLOOP_MAX)
- {
- ret = -ELOOP;
- break;
- }
- /* Set up for the next time through the loop */
- node = desc->node;
- DEBUGASSERT(node != NULL);
- desc->linktgt = link;
- }
- desc->nofollow = save;
- return ret;
- }
- #endif
- /****************************************************************************
- * Name: _inode_search
- *
- * Description:
- * Find the inode associated with 'path' returning the inode references
- * and references to its companion nodes. This is the internal, common
- * implementation of inode_search().
- *
- * If a mountpoint is encountered in the search prior to encountering the
- * terminal node, the search will terminate at the mountpoint inode. That
- * inode and the relative path from the mountpoint, 'relpath' will be
- * returned.
- *
- * If a soft link is encountered that is not the terminal node in the path,
- * that link WILL be deferenced unconditionally.
- *
- * Assumptions:
- * The caller holds the g_inode_sem semaphore
- *
- ****************************************************************************/
- static int _inode_search(FAR struct inode_search_s *desc)
- {
- FAR const char *name;
- FAR struct inode *node = g_root_inode;
- FAR struct inode *left = NULL;
- FAR struct inode *above = NULL;
- FAR const char *relpath = NULL;
- int ret = -ENOENT;
- /* Get the search path, skipping over the leading '/'. The leading '/' is
- * mandatory because only absolte paths are expected in this context.
- */
- DEBUGASSERT(desc != NULL && desc->path != NULL);
- name = desc->path;
- if (*name != '/')
- {
- return -EINVAL;
- }
- /* Skip over the leading '/' */
- while (*name == '/')
- {
- name++;
- }
- /* Special case the root directory. There is no root inode and there is
- * no name for the root.
- */
- if (*name == '\0')
- {
- /* This is a bug. I don't know how to handle this case yet. */
- return -ENOSYS;
- }
- /* Traverse the pseudo file system node tree until either (1) all nodes
- * have been examined without finding the matching node, or (2) the
- * matching node is found.
- */
- while (node != NULL)
- {
- int result = _inode_compare(name, node);
- /* Case 1: The name is less than the name of the node.
- * Since the names are ordered, these means that there
- * is no peer node with this name and that there can be
- * no match in the filesystem.
- */
- if (result < 0)
- {
- node = NULL;
- break;
- }
- /* Case 2: the name is greater than the name of the node.
- * In this case, the name may still be in the list to the
- * "right"
- */
- else if (result > 0)
- {
- /* Continue looking to the "right" of this inode. */
- left = node;
- node = node->i_peer;
- }
- /* The names match */
- else
- {
- /* Now there are three remaining possibilities:
- * (1) This is the node that we are looking for.
- * (2) The node we are looking for is "below" this one.
- * (3) This node is a mountpoint and will absorb all requests
- * below this one
- */
- name = inode_nextname(name);
- if (*name == '\0' || INODE_IS_MOUNTPT(node))
- {
- /* Either (1) we are at the end of the path, so this must be
- * the node we are looking for or else (2) this node is a
- * mountpoint and will handle the remaining part of the
- * pathname
- */
- relpath = name;
- ret = OK;
- break;
- }
- else
- {
- /* More nodes to be examined in the path "below" this one. */
- #ifdef CONFIG_PSEUDOFS_SOFTLINKS
- /* Was the node a soft link? If so, then we need need to
- * continue below the target of the link, not the link itself.
- */
- if (INODE_IS_SOFTLINK(node))
- {
- int status;
- /* If this intermediate inode in the is a soft link, then
- * (1) get the name of the full path of the soft link, (2)
- * recursively look-up the inode referenced by the soft
- * link, and (3) continue searching with that inode instead.
- */
- status = _inode_linktarget(node, desc);
- if (status < 0)
- {
- /* Probably means that the target of the symbolic link
- * does not exist.
- */
- ret = status;
- break;
- }
- else
- {
- FAR struct inode *newnode = desc->node;
- if (newnode != node)
- {
- /* The node was a valid symbolic link and we have
- * jumped to a different, spot in the pseudo file
- * system tree.
- */
- /* Check if this took us to a mountpoint. */
- if (INODE_IS_MOUNTPT(newnode))
- {
- /* Return the mountpoint information.
- * NOTE that the last path to the link target
- * was already set by _inode_linktarget().
- */
- node = newnode;
- above = NULL;
- left = NULL;
- relpath = name;
- ret = OK;
- break;
- }
- /* Continue from this new inode. */
- node = newnode;
- }
- }
- }
- #endif
- /* Keep looking at the next level "down" */
- above = node;
- left = NULL;
- node = node->i_child;
- }
- }
- }
- /* The node may or may not be null as per one of the following four cases
- * cases:
- *
- * With node = NULL
- *
- * (1) We went left past the final peer: The new node name is larger
- * than any existing node name at that level.
- * (2) We broke out in the middle of the list of peers because the name
- * was not found in the ordered list.
- * (3) We went down past the final parent: The new node name is
- * "deeper" than anything that we currently have in the tree.
- *
- * With node != NULL
- *
- * (4) When the node matching the full path is found
- */
- desc->path = name;
- desc->node = node;
- desc->peer = left;
- desc->parent = above;
- desc->relpath = relpath;
- return ret;
- }
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: inode_search
- *
- * Description:
- * Find the inode associated with 'path' returning the inode references
- * and references to its companion nodes.
- *
- * If a mountpoint is encountered in the search prior to encountering the
- * terminal node, the search will terminate at the mountpoint inode. That
- * inode and the relative path from the mountpoint, 'relpath' will be
- * returned.
- *
- * inode_search will follow soft links in path leading up to the terminal
- * node. Whether or no inode_search() will deference that terminal node
- * depends on the 'nofollow' input.
- *
- * If a soft link is encountered that is not the terminal node in the path,
- * that link WILL be deferenced unconditionally.
- *
- * Assumptions:
- * The caller holds the g_inode_sem semaphore
- *
- ****************************************************************************/
- int inode_search(FAR struct inode_search_s *desc)
- {
- int ret;
- /* Perform the common _inode_search() logic. This does everything except
- * operations special operations that must be performed on the terminal
- * node if node is a symbolic link.
- */
- DEBUGASSERT(desc != NULL);
- #ifdef CONFIG_PSEUDOFS_SOFTLINKS
- desc->linktgt = NULL;
- #endif
- ret = _inode_search(desc);
- #ifdef CONFIG_PSEUDOFS_SOFTLINKS
- if (ret >= 0)
- {
- FAR struct inode *node;
- /* Search completed successfully */
- node = desc->node;
- DEBUGASSERT(node != NULL);
- /* Is the terminal node a softlink? Should we follow it? */
- if (!desc->nofollow && INODE_IS_SOFTLINK(node))
- {
- /* Save some things we need that will be clobbered by the call to
- * _inode_linktgt().
- */
- FAR const char *relpath = desc->relpath; /* Will always be "" here */
- /* The terminating inode is a valid soft link: Return the inode,
- * corresponding to link target. _inode_linktarget() will follow
- * a link (or a series of links to links) and will return the
- * link target of the final symbolic link in the series.
- */
- ret = _inode_linktarget(node, desc);
- if (ret < 0)
- {
- /* The most likely cause for failure is that the target of the
- * symbolic link does not exist.
- */
- return ret;
- }
- /* The dereferenced node might be a mountpoint */
- node = desc->node;
- DEBUGASSERT(node != NULL && desc->linktgt != NULL);
- if (INODE_IS_MOUNTPT(node))
- {
- /* Yes... set up for the MOUNTPOINT logic below. */
- desc->relpath = relpath;
- }
- }
- /* Handle a special case. This special occurs with either (1)
- * inode_search() terminates early because it encountered a MOUNTPOINT
- * at an intermediate node in the path, or (2) inode_search()
- * terminates because it reached the terminal node and 'nofollow' is
- * false and the above logic converted the symbolic link to a
- * MOUNTPOINT.
- *
- * We can detect the special cases because desc->linktgt will be
- * non-NULL.
- */
- if (desc->linktgt != NULL && INODE_IS_MOUNTPT(node))
- {
- FAR char *buffer;
- /* There would be no problem in this case if the link was to
- * either to the root directory of the MOUNTPOINT or to a
- * regular file within the mounted volume. However, there
- * is a problem if the symbolic link is to a directory within
- * the mounted volume. In that case, the 'relpath' will be
- * relative to the symbolic link and not to the MOUNTPOINT.
- *
- * We will handle the worst case by creating the full path
- * excluding the symbolic link and performing the look-up
- * again.
- */
- if (desc->relpath != NULL && *desc->relpath != '\0')
- {
- (void)asprintf(&buffer, "%s/%s",
- desc->linktgt, desc->relpath);
- }
- else
- {
- buffer = strdup(desc->linktgt);
- }
- if (buffer == NULL)
- {
- ret = -ENOMEM;
- }
- else
- {
- /* Reset the search description and perform the search again. */
- RELEASE_SEARCH(desc);
- SETUP_SEARCH(desc, buffer, false);
- desc->buffer = buffer;
- ret = _inode_search(desc);
- }
- }
- }
- #endif
- return ret;
- }
- /****************************************************************************
- * Name: inode_nextname
- *
- * Description:
- * Given a path with node names separated by '/', return the next path
- * segment name.
- *
- ****************************************************************************/
- FAR const char *inode_nextname(FAR const char *name)
- {
- /* Search for the '/' delimiter or the NUL terminator at the end of the
- * path segment.
- */
- while (*name != '\0' && *name != '/')
- {
- name++;
- }
- /* If we found the '/' delimiter, then the path segment we want begins at
- * the next character (which might also be the NUL terminator).
- */
- while (*name == '/')
- {
- name++;
- }
- return name;
- }
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