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/*
* Copyright (C) 2015 Colin Walters <walters@verbum.org>.
*
* SPDX-License-Identifier: LGPL-2.0+
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "config.h"
#include <dirent.h>
#include <stdio.h>
#include <unistd.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <glib.h>
/* Glibc uses readdir64 when _FILE_OFFSET_BITS == 64 as set by
* AC_SYS_LARGEFILE on 32 bit systems.
*/
#if defined(_FILE_OFFSET_BITS) && (_FILE_OFFSET_BITS == 64)
# define READDIR "readdir64"
# define READDIR_R "readdir64_r"
#else
# define READDIR "readdir"
# define READDIR_R "readdir_r"
#endif
static GHashTable *direntcache;
static GMutex direntcache_lock;
static gsize initialized;
typedef struct {
GPtrArray *entries;
guint offset;
} DirEntries;
static void
dir_entries_free (gpointer data)
{
DirEntries *d = data;
g_ptr_array_unref (d->entries);
g_free (d);
}
static DirEntries *
dir_entries_new (void)
{
DirEntries *d = g_new0 (DirEntries, 1);
d->entries = g_ptr_array_new_with_free_func (g_free);
return d;
}
static void
ensure_initialized (void)
{
if (g_once_init_enter (&initialized))
{
direntcache = g_hash_table_new_full (NULL, NULL, NULL, dir_entries_free);
g_mutex_init (&direntcache_lock);
g_once_init_leave (&initialized, 1);
}
}
struct dirent *
readdir (DIR *dirp)
{
struct dirent *(*real_readdir)(DIR *dirp) = dlsym (RTLD_NEXT, READDIR);
struct dirent *ret;
gboolean cache_another = TRUE;
ensure_initialized ();
/* The core idea here is that each time through the loop, we read a
* directory entry. If there is one, we choose whether to cache it
* or to return it. Because multiple entries can be cached,
* ordering is randomized. Statistically, the order will still be
* *weighted* towards the ordering returned from the
* kernel/filesystem, but the goal here is just to provide some
* randomness in order to trigger bugs, not to be perfectly random.
*/
while (cache_another)
{
DirEntries *de;
errno = 0;
ret = real_readdir (dirp);
if (ret == NULL && errno != 0)
goto out;
g_mutex_lock (&direntcache_lock);
de = g_hash_table_lookup (direntcache, dirp);
if (ret)
{
if (g_random_boolean ())
{
struct dirent *copy;
if (!de)
{
de = dir_entries_new ();
g_hash_table_insert (direntcache, dirp, de);
}
copy = g_memdup (ret, sizeof (struct dirent));
g_ptr_array_add (de->entries, copy);
}
else
{
cache_another = FALSE;
}
}
else
{
if (de && de->offset < de->entries->len)
{
ret = de->entries->pdata[de->offset];
de->offset++;
}
cache_another = FALSE;
}
g_mutex_unlock (&direntcache_lock);
}
out:
return ret;
}
int
closedir (DIR *dirp)
{
int (*real_closedir)(DIR *dirp) = dlsym (RTLD_NEXT, "closedir");
ensure_initialized ();
g_mutex_lock (&direntcache_lock);
g_hash_table_remove (direntcache, dirp);
g_mutex_unlock (&direntcache_lock);
return real_closedir (dirp);
}
static void
assert_no_cached_entries (DIR *dirp)
{
DirEntries *de;
g_mutex_lock (&direntcache_lock);
de = g_hash_table_lookup (direntcache, dirp);
g_assert (!de || de->entries->len == 0);
g_mutex_unlock (&direntcache_lock);
}
void
seekdir (DIR *dirp, long loc)
{
void (*real_seekdir)(DIR *dirp, long loc) = dlsym (RTLD_NEXT, "seekdir");
ensure_initialized ();
/* For now, crash if seekdir is called when we have cached entries.
* If some app wants to use this and seekdir() we can implement it.
*/
assert_no_cached_entries (dirp);
real_seekdir (dirp, loc);
}
void
rewinddir (DIR *dirp)
{
void (*real_rewinddir)(DIR *dirp) = dlsym (RTLD_NEXT, "rewinddir");
ensure_initialized ();
/* Blow away the cache */
g_mutex_lock (&direntcache_lock);
g_hash_table_remove (direntcache, dirp);
g_mutex_unlock (&direntcache_lock);
real_rewinddir (dirp);
}
int
readdir_r (DIR *dirp, struct dirent *entry, struct dirent **result)
{
int (*real_readdir_r)(DIR *dirp, struct dirent *entry, struct dirent **result) = dlsym (RTLD_NEXT, READDIR_R);
ensure_initialized ();
/* For now, assert that no one is mixing readdir_r() with readdir().
* It'd be broken to do so, and very few programs use readdir_r()
* anyways. */
assert_no_cached_entries (dirp);
return real_readdir_r (dirp, entry, result);
}
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