The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/devfs/devfs_dir.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2010 Jaakko Heinonen <jh@FreeBSD.org>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  *
   28  * $FreeBSD: releng/12.0/sys/fs/devfs/devfs_dir.c 326395 2017-11-30 14:06:54Z manu $
   29  */
   30 
   31 #include <sys/param.h>
   32 #include <sys/conf.h>
   33 #include <sys/types.h>
   34 #include <sys/kernel.h>
   35 #include <sys/libkern.h>
   36 #include <sys/lock.h>
   37 #include <sys/malloc.h>
   38 #include <sys/mutex.h>
   39 #include <sys/queue.h>
   40 #include <sys/systm.h>
   41 #include <sys/sx.h>
   42 
   43 #include <fs/devfs/devfs.h>
   44 #include <fs/devfs/devfs_int.h>
   45 
   46 struct dirlistent {
   47         char                    *dir;
   48         int                     refcnt;
   49         LIST_ENTRY(dirlistent)  link;
   50 };
   51 
   52 static LIST_HEAD(, dirlistent) devfs_dirlist =
   53     LIST_HEAD_INITIALIZER(devfs_dirlist);
   54 
   55 static MALLOC_DEFINE(M_DEVFS4, "DEVFS4", "DEVFS directory list");
   56 
   57 static struct mtx dirlist_mtx;
   58 MTX_SYSINIT(dirlist_mtx, &dirlist_mtx, "devfs dirlist lock", MTX_DEF);
   59 
   60 /* Returns 1 if the path is in the directory list. */
   61 int
   62 devfs_dir_find(const char *path)
   63 {
   64         struct dirlistent *dle;
   65 
   66         mtx_lock(&dirlist_mtx);
   67         LIST_FOREACH(dle, &devfs_dirlist, link) {
   68                 if (devfs_pathpath(dle->dir, path) != 0) {
   69                         mtx_unlock(&dirlist_mtx);
   70                         return (1);
   71                 }
   72         }
   73         mtx_unlock(&dirlist_mtx);
   74 
   75         return (0);
   76 }
   77 
   78 static struct dirlistent *
   79 devfs_dir_findent_locked(const char *dir)
   80 {
   81         struct dirlistent *dle;
   82 
   83         mtx_assert(&dirlist_mtx, MA_OWNED);
   84 
   85         LIST_FOREACH(dle, &devfs_dirlist, link) {
   86                 if (strcmp(dir, dle->dir) == 0)
   87                         return (dle);
   88         }
   89 
   90         return (NULL);
   91 }
   92 
   93 static void
   94 devfs_dir_ref(const char *dir)
   95 {
   96         struct dirlistent *dle, *dle_new;
   97 
   98         if (*dir == '\0')
   99                 return;
  100 
  101         dle_new = malloc(sizeof(*dle), M_DEVFS4, M_WAITOK);
  102         dle_new->dir = strdup(dir, M_DEVFS4);
  103         dle_new->refcnt = 1;
  104 
  105         mtx_lock(&dirlist_mtx);
  106         dle = devfs_dir_findent_locked(dir);
  107         if (dle != NULL) {
  108                 dle->refcnt++;
  109                 mtx_unlock(&dirlist_mtx);
  110                 free(dle_new->dir, M_DEVFS4);
  111                 free(dle_new, M_DEVFS4);
  112                 return;
  113         }
  114         LIST_INSERT_HEAD(&devfs_dirlist, dle_new, link);
  115         mtx_unlock(&dirlist_mtx);
  116 }
  117 
  118 void
  119 devfs_dir_ref_de(struct devfs_mount *dm, struct devfs_dirent *de)
  120 {
  121         char dirname[SPECNAMELEN + 1], *namep;
  122 
  123         namep = devfs_fqpn(dirname, dm, de, NULL);
  124         KASSERT(namep != NULL, ("devfs_ref_dir_de: NULL namep"));
  125 
  126         devfs_dir_ref(namep);
  127 }
  128 
  129 static void
  130 devfs_dir_unref(const char *dir)
  131 {
  132         struct dirlistent *dle;
  133 
  134         if (*dir == '\0')
  135                 return;
  136 
  137         mtx_lock(&dirlist_mtx);
  138         dle = devfs_dir_findent_locked(dir);
  139         KASSERT(dle != NULL, ("devfs_dir_unref: dir %s not referenced", dir));
  140         dle->refcnt--;
  141         KASSERT(dle->refcnt >= 0, ("devfs_dir_unref: negative refcnt"));
  142         if (dle->refcnt == 0) {
  143                 LIST_REMOVE(dle, link);
  144                 mtx_unlock(&dirlist_mtx);
  145                 free(dle->dir, M_DEVFS4);
  146                 free(dle, M_DEVFS4);
  147         } else
  148                 mtx_unlock(&dirlist_mtx);
  149 }
  150 
  151 void
  152 devfs_dir_unref_de(struct devfs_mount *dm, struct devfs_dirent *de)
  153 {
  154         char dirname[SPECNAMELEN + 1], *namep;
  155 
  156         namep = devfs_fqpn(dirname, dm, de, NULL);
  157         KASSERT(namep != NULL, ("devfs_unref_dir_de: NULL namep"));
  158 
  159         devfs_dir_unref(namep);
  160 }
  161 
  162 /* Returns 1 if the path p1 contains the path p2. */
  163 int
  164 devfs_pathpath(const char *p1, const char *p2)
  165 {
  166 
  167         for (;;p1++, p2++) {
  168                 if (*p1 != *p2) {
  169                         if (*p1 == '/' && *p2 == '\0')
  170                                 return (1);
  171                         else
  172                                 return (0);
  173                 } else if (*p1 == '\0')
  174                         return (1);
  175         }
  176         /* NOTREACHED */
  177 }

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