4 * (C) Copyright 2003, 2004 by Theodore Ts'o.
6 * Compile using the command:
8 * gcc -o spd_readdir.so -fPIC -shared spd_readdir.c -ldl
10 * Use it by setting the LD_PRELOAD environment variable:
12 * export LD_PRELOAD=/usr/local/sbin/spd_readdir.so
14 * Note that this preload is not going to work for all programs. In
15 * particular, although it does supply readdir_r(), it is *not* thread
16 * safe. So I can't recommend this as something to be dropped in
20 * This file may be redistributed under the terms of the GNU Public
26 #define ALLOC_STEPSIZE 100
32 #define DEBUG_DIR(x) {if (do_debug) { x; }}
38 #define __USE_LARGEFILE64
42 #include <sys/types.h>
51 unsigned long long d_ino;
53 unsigned short int d_reclen;
65 struct dirent ret_dir;
66 struct dirent64 ret_dir64;
69 static int (*real_closedir)(DIR *dir) = 0;
70 static DIR *(*real_opendir)(const char *name) = 0;
71 static DIR *(*real_fdopendir)(int fd) = 0;
72 static void *(*real_rewinddir)(DIR *dirp) = 0;
73 static struct dirent *(*real_readdir)(DIR *dir) = 0;
74 static int (*real_readdir_r)(DIR *dir, struct dirent *entry,
75 struct dirent **result) = 0;
76 static struct dirent64 *(*real_readdir64)(DIR *dir) = 0;
77 static off_t (*real_telldir)(DIR *dir) = 0;
78 static void (*real_seekdir)(DIR *dir, off_t offset) = 0;
79 static int (*real_dirfd)(DIR *dir) = 0;
80 static unsigned long max_dirsize = MAX_DIRSIZE;
81 static int num_open = 0;
83 static int do_debug = 0;
86 static void setup_ptr()
90 real_opendir = dlsym(RTLD_NEXT, "opendir");
91 real_fdopendir = dlsym(RTLD_NEXT, "fdopendir");
92 real_closedir = dlsym(RTLD_NEXT, "closedir");
93 real_rewinddir = dlsym(RTLD_NEXT, "rewinddir");
94 real_readdir = dlsym(RTLD_NEXT, "readdir");
95 real_readdir_r = dlsym(RTLD_NEXT, "readdir_r");
96 real_readdir64 = dlsym(RTLD_NEXT, "readdir64");
97 real_telldir = dlsym(RTLD_NEXT, "telldir");
98 real_seekdir = dlsym(RTLD_NEXT, "seekdir");
99 real_dirfd = dlsym(RTLD_NEXT, "dirfd");
100 if ((cp = getenv("SPD_READDIR_MAX_SIZE")) != NULL) {
101 max_dirsize = atol(cp);
104 if (getenv("SPD_READDIR_DEBUG")) {
105 printf("initialized!\n");
111 static void free_cached_dir(struct dir_s *dirstruct)
118 for (i=0; i < dirstruct->num; i++) {
119 free(dirstruct->dp[i].d_name);
123 dirstruct->max = dirstruct->num = 0;
126 static int ino_cmp(const void *a, const void *b)
128 const struct dirent_s *ds_a = (const struct dirent_s *) a;
129 const struct dirent_s *ds_b = (const struct dirent_s *) b;
135 if (ds_a->d_name[0] == '.') {
136 if (ds_a->d_name[1] == 0)
138 else if ((ds_a->d_name[1] == '.') && (ds_a->d_name[2] == 0))
141 if (ds_b->d_name[0] == '.') {
142 if (ds_b->d_name[1] == 0)
144 else if ((ds_b->d_name[1] == '.') && (ds_b->d_name[2] == 0))
151 struct dir_s *alloc_dirstruct(DIR *dir)
153 struct dir_s *dirstruct;
155 dirstruct = malloc(sizeof(struct dir_s));
157 memset(dirstruct, 0, sizeof(struct dir_s));
158 dirstruct->dir = dir;
162 void cache_dirstruct(struct dir_s *dirstruct)
164 struct dirent_s *ds, *dnew;
167 while ((d = (*real_readdir64)(dirstruct->dir)) != NULL) {
168 if (dirstruct->num >= dirstruct->max) {
169 dirstruct->max += ALLOC_STEPSIZE;
170 DEBUG_DIR(printf("Reallocating to size %d\n",
172 dnew = realloc(dirstruct->dp,
173 dirstruct->max * sizeof(struct dir_s));
176 dirstruct->dp = dnew;
178 ds = &dirstruct->dp[dirstruct->num++];
179 ds->d_ino = d->d_ino;
180 ds->d_off = d->d_off;
181 ds->d_reclen = d->d_reclen;
182 ds->d_type = d->d_type;
183 if ((ds->d_name = malloc(strlen(d->d_name)+1)) == NULL) {
187 strcpy(ds->d_name, d->d_name);
188 DEBUG_DIR(printf("readdir: %lu %s\n",
189 (unsigned long) d->d_ino, d->d_name));
191 qsort(dirstruct->dp, dirstruct->num, sizeof(struct dirent_s), ino_cmp);
194 DEBUG_DIR(printf("No memory, backing off to direct readdir\n"));
195 free_cached_dir(dirstruct);
196 dirstruct->direct = 1;
199 DIR *opendir(const char *name)
202 struct dir_s *dirstruct;
208 DEBUG_DIR(printf("Opendir(%s) (%d open)\n", name, num_open++));
209 dir = (*real_opendir)(name);
213 dirstruct = alloc_dirstruct(dir);
215 (*real_closedir)(dir);
220 if (max_dirsize && (stat(name, &st) == 0) &&
221 (st.st_size > max_dirsize)) {
222 DEBUG_DIR(printf("Directory size %ld, using direct readdir\n",
224 dirstruct->direct = 1;
225 return (DIR *) dirstruct;
228 cache_dirstruct(dirstruct);
229 return ((DIR *) dirstruct);
232 DIR *fdopendir(int fd)
235 struct dir_s *dirstruct;
241 DEBUG_DIR(printf("fdpendir(%d) (%d open)\n", fd, num_open++));
242 dir = (*real_fdopendir)(fd);
246 dirstruct = alloc_dirstruct(dir);
248 (*real_closedir)(dir);
253 if (max_dirsize && (fstat(fd, &st) == 0) &&
254 (st.st_size > max_dirsize)) {
255 DEBUG_DIR(printf("Directory size %ld, using direct readdir\n",
257 dirstruct->dir = dir;
258 dirstruct->direct = 1;
259 return (DIR *) dirstruct;
262 cache_dirstruct(dirstruct);
263 return ((DIR *) dirstruct);
266 int closedir(DIR *dir)
268 struct dir_s *dirstruct = (struct dir_s *) dir;
270 DEBUG_DIR(printf("Closedir (%d open)\n", --num_open));
272 (*real_closedir)(dirstruct->dir);
274 free_cached_dir(dirstruct);
279 struct dirent *readdir(DIR *dir)
281 struct dir_s *dirstruct = (struct dir_s *) dir;
284 if (dirstruct->direct)
285 return (*real_readdir)(dirstruct->dir);
287 if (dirstruct->pos >= dirstruct->num)
290 ds = &dirstruct->dp[dirstruct->pos++];
291 dirstruct->ret_dir.d_ino = ds->d_ino;
292 dirstruct->ret_dir.d_off = ds->d_off;
293 dirstruct->ret_dir.d_reclen = ds->d_reclen;
294 dirstruct->ret_dir.d_type = ds->d_type;
295 strncpy(dirstruct->ret_dir.d_name, ds->d_name,
296 sizeof(dirstruct->ret_dir.d_name));
298 return (&dirstruct->ret_dir);
301 int readdir_r(DIR *dir, struct dirent *entry, struct dirent **result)
303 struct dir_s *dirstruct = (struct dir_s *) dir;
306 if (dirstruct->direct)
307 return (*real_readdir_r)(dirstruct->dir, entry, result);
309 if (dirstruct->pos >= dirstruct->num) {
314 ds = &dirstruct->dp[dirstruct->pos++];
315 entry->d_ino = ds->d_ino;
316 entry->d_off = ds->d_off;
317 entry->d_reclen = ds->d_reclen;
318 entry->d_type = ds->d_type;
319 strncpy(entry->d_name, ds->d_name, sizeof(entry->d_name));
325 struct dirent64 *readdir64(DIR *dir)
327 struct dir_s *dirstruct = (struct dir_s *) dir;
330 if (dirstruct->direct)
331 return (*real_readdir64)(dirstruct->dir);
333 if (dirstruct->pos >= dirstruct->num)
336 ds = &dirstruct->dp[dirstruct->pos++];
337 dirstruct->ret_dir64.d_ino = ds->d_ino;
338 dirstruct->ret_dir64.d_off = ds->d_off;
339 dirstruct->ret_dir64.d_reclen = ds->d_reclen;
340 dirstruct->ret_dir64.d_type = ds->d_type;
341 strncpy(dirstruct->ret_dir64.d_name, ds->d_name,
342 sizeof(dirstruct->ret_dir64.d_name));
344 return (&dirstruct->ret_dir64);
347 off_t telldir(DIR *dir)
349 struct dir_s *dirstruct = (struct dir_s *) dir;
351 if (dirstruct->direct)
352 return (*real_telldir)(dirstruct->dir);
354 return ((off_t) dirstruct->pos);
357 void seekdir(DIR *dir, off_t offset)
359 struct dir_s *dirstruct = (struct dir_s *) dir;
361 if (dirstruct->direct) {
362 (*real_seekdir)(dirstruct->dir, offset);
366 dirstruct->pos = offset;
369 void rewinddir(DIR *dir)
371 struct dir_s *dirstruct = (struct dir_s *) dir;
373 (*real_rewinddir)(dirstruct->dir);
374 if (dirstruct->direct)
378 free_cached_dir(dirstruct);
379 cache_dirstruct(dirstruct);
384 struct dir_s *dirstruct = (struct dir_s *) dir;
385 int fd = (*real_dirfd)(dirstruct->dir);
387 DEBUG_DIR(printf("dirfd %d, %p\n", fd, real_dirfd));