/**************************************************************************** * fs/inode/fs_inodesearch.c * * Copyright (C) 2007-2009, 2011-2012, 2016-2017 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #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 absolute 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') { 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; }