1 /*
2 * readdir accelerator
3 *
4 * (C) Copyright 2003, 2004, 2008 by Theodore Ts'o.
5 *
6 * 2008-06-08 Modified by Ross Boylan <RossBoylan stanfordalumni org>
7 * Added support for readdir_r and readdir64_r calls. Note
8 * this has not been tested on anything other than GNU/Linux i386,
9 * and that the regular readdir wrapper will take slightly more
10 * space than Ted's original since it now includes a lock.
11 *
12 * Compile using the command:
13 *
14 * gcc -o spd_readdir.so -shared -fpic spd_readdir.c -ldl
15 *
16 * Use it by setting the LD_PRELOAD environment variable:
17 *
18 * export LD_PRELOAD=/usr/local/sbin/spd_readdir.so
19 *
20 * %Begin-Header%
21 * This file may be redistributed under the terms of the GNU Public
22 * License.
23 * %End-Header%
24 *
25 */
26
27 #define ALLOC_STEPSIZE 100
28 #define MAX_DIRSIZE 0
29
30 #define DEBUG
31 /* Util we autoconfiscate spd_readdir... */
32 #define HAVE___SECURE_GETENV 1
33 #define HAVE_PRCTL 1
34 #define HAVE_SYS_PRCTL_H 1
35
36 #ifdef DEBUG
37 #define DEBUG_DIR(x) {if (do_debug) { x; }}
38 #else
39 #define DEBUG_DIR(x)
40 #endif
41
42 #define _GNU_SOURCE
43 #define __USE_LARGEFILE64
44
45 #include <stdio.h>
46 #include <unistd.h>
47 #include <sys/types.h>
48 #include <sys/stat.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <dirent.h>
52 #include <errno.h>
53 #include <dlfcn.h>
54 #ifdef HAVE_SYS_PRCTL_H
55 #include <sys/prctl.h>
56 #else
57 #define PR_GET_DUMPABLE 3
58 #endif
59 #include <pthread.h>
60
61 struct dirent_s {
62 unsigned long long d_ino;
63 long long d_off;
64 unsigned short int d_reclen;
65 unsigned char d_type;
66 char *d_name;
67 };
68
69 struct dir_s {
70 DIR *dir;
71 pthread_mutex_t lock; /* Mutex lock for this structure. */
72 int num;
73 int max;
74 struct dirent_s *dp;
75 int pos;
76 int direct;
77 struct dirent ret_dir;
78 struct dirent64 ret_dir64;
79 };
80
81 static int (*real_closedir)(DIR *dir) = 0;
82 static DIR *(*real_opendir)(const char *name) = 0;
83 static DIR *(*real_fdopendir)(int fd) = 0;
84 static void *(*real_rewinddir)(DIR *dirp) = 0;
85 static struct dirent *(*real_readdir)(DIR *dir) = 0;
86 static int (*real_readdir_r)(DIR *dir, struct dirent *entry,
87 struct dirent **result) = 0;
88 static struct dirent64 *(*real_readdir64)(DIR *dir) = 0;
89 static int (*real_readdir64_r)(DIR *dir, struct dirent64 *entry,
90 struct dirent64 **result) = 0;
91 static off_t (*real_telldir)(DIR *dir) = 0;
92 static void (*real_seekdir)(DIR *dir, off_t offset) = 0;
93 static int (*real_dirfd)(DIR *dir) = 0;
94 static unsigned long max_dirsize = MAX_DIRSIZE;
95 static int num_open = 0;
96 #ifdef DEBUG
97 static int do_debug = 0;
98 #endif
99
safe_getenv(const char * arg)100 static char *safe_getenv(const char *arg)
101 {
102 if ((getuid() != geteuid()) || (getgid() != getegid()))
103 return NULL;
104 #if HAVE_PRCTL
105 if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
106 return NULL;
107 #else
108 #if (defined(linux) && defined(SYS_prctl))
109 if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
110 return NULL;
111 #endif
112 #endif
113
114 #if HAVE___SECURE_GETENV
115 return __secure_getenv(arg);
116 #else
117 return getenv(arg);
118 #endif
119 }
120
setup_ptr()121 static void setup_ptr()
122 {
123 char *cp;
124
125 real_opendir = dlsym(RTLD_NEXT, "opendir");
126 real_fdopendir = dlsym(RTLD_NEXT, "fdopendir");
127 real_closedir = dlsym(RTLD_NEXT, "closedir");
128 real_rewinddir = dlsym(RTLD_NEXT, "rewinddir");
129 real_readdir = dlsym(RTLD_NEXT, "readdir");
130 real_readdir_r = dlsym(RTLD_NEXT, "readdir_r");
131 real_readdir64 = dlsym(RTLD_NEXT, "readdir64");
132 real_readdir64_r = dlsym(RTLD_NEXT, "readdir64_r");
133 real_telldir = dlsym(RTLD_NEXT, "telldir");
134 real_seekdir = dlsym(RTLD_NEXT, "seekdir");
135 real_dirfd = dlsym(RTLD_NEXT, "dirfd");
136 if ((cp = safe_getenv("SPD_READDIR_MAX_SIZE")) != NULL) {
137 max_dirsize = atol(cp);
138 }
139 #ifdef DEBUG
140 if (safe_getenv("SPD_READDIR_DEBUG")) {
141 printf("initialized!\n");
142 do_debug++;
143 }
144 #endif
145 }
146
free_cached_dir(struct dir_s * dirstruct)147 static void free_cached_dir(struct dir_s *dirstruct)
148 {
149 int i;
150
151 pthread_mutex_destroy(&(dirstruct->lock));
152
153 if (!dirstruct->dp)
154 return;
155
156 for (i=0; i < dirstruct->num; i++) {
157 free(dirstruct->dp[i].d_name);
158 }
159 free(dirstruct->dp);
160 dirstruct->dp = 0;
161 dirstruct->max = dirstruct->num = 0;
162 }
163
ino_cmp(const void * a,const void * b)164 static int ino_cmp(const void *a, const void *b)
165 {
166 const struct dirent_s *ds_a = (const struct dirent_s *) a;
167 const struct dirent_s *ds_b = (const struct dirent_s *) b;
168 ino_t i_a, i_b;
169
170 i_a = ds_a->d_ino;
171 i_b = ds_b->d_ino;
172
173 if (ds_a->d_name[0] == '.') {
174 if (ds_a->d_name[1] == 0)
175 i_a = 0;
176 else if ((ds_a->d_name[1] == '.') && (ds_a->d_name[2] == 0))
177 i_a = 1;
178 }
179 if (ds_b->d_name[0] == '.') {
180 if (ds_b->d_name[1] == 0)
181 i_b = 0;
182 else if ((ds_b->d_name[1] == '.') && (ds_b->d_name[2] == 0))
183 i_b = 1;
184 }
185
186 return (i_a - i_b);
187 }
188
alloc_dirstruct(DIR * dir)189 static struct dir_s *alloc_dirstruct(DIR *dir)
190 {
191 struct dir_s *dirstruct;
192 static pthread_mutexattr_t mutexattr;
193 mutexattr.__align = PTHREAD_MUTEX_RECURSIVE;
194
195 dirstruct = malloc(sizeof(struct dir_s));
196 if (dirstruct)
197 memset(dirstruct, 0, sizeof(struct dir_s));
198 dirstruct->dir = dir;
199 pthread_mutex_init(&(dirstruct->lock), &mutexattr);
200 return dirstruct;
201 }
202
cache_dirstruct(struct dir_s * dirstruct)203 static void cache_dirstruct(struct dir_s *dirstruct)
204 {
205 struct dirent_s *ds, *dnew;
206 struct dirent64 *d;
207
208 while ((d = (*real_readdir64)(dirstruct->dir)) != NULL) {
209 if (dirstruct->num >= dirstruct->max) {
210 dirstruct->max += ALLOC_STEPSIZE;
211 DEBUG_DIR(printf("Reallocating to size %d\n",
212 dirstruct->max));
213 dnew = realloc(dirstruct->dp,
214 dirstruct->max * sizeof(struct dir_s));
215 if (!dnew)
216 goto nomem;
217 dirstruct->dp = dnew;
218 }
219 ds = &dirstruct->dp[dirstruct->num++];
220 ds->d_ino = d->d_ino;
221 ds->d_off = d->d_off;
222 ds->d_reclen = d->d_reclen;
223 ds->d_type = d->d_type;
224 if ((ds->d_name = malloc(strlen(d->d_name)+1)) == NULL) {
225 dirstruct->num--;
226 goto nomem;
227 }
228 strcpy(ds->d_name, d->d_name);
229 DEBUG_DIR(printf("readdir: %lu %s\n",
230 (unsigned long) d->d_ino, d->d_name));
231 }
232 qsort(dirstruct->dp, dirstruct->num, sizeof(struct dirent_s), ino_cmp);
233 return;
234 nomem:
235 DEBUG_DIR(printf("No memory, backing off to direct readdir\n"));
236 free_cached_dir(dirstruct);
237 dirstruct->direct = 1;
238 }
239
opendir(const char * name)240 DIR *opendir(const char *name)
241 {
242 DIR *dir;
243 struct dir_s *dirstruct;
244 struct stat st;
245
246 if (!real_opendir)
247 setup_ptr();
248
249 DEBUG_DIR(printf("Opendir(%s) (%d open)\n", name, num_open++));
250 dir = (*real_opendir)(name);
251 if (!dir)
252 return NULL;
253
254 dirstruct = alloc_dirstruct(dir);
255 if (!dirstruct) {
256 (*real_closedir)(dir);
257 errno = -ENOMEM;
258 return NULL;
259 }
260
261 if (max_dirsize && (stat(name, &st) == 0) &&
262 (st.st_size > max_dirsize)) {
263 DEBUG_DIR(printf("Directory size %ld, using direct readdir\n",
264 st.st_size));
265 dirstruct->direct = 1;
266 return (DIR *) dirstruct;
267 }
268
269 cache_dirstruct(dirstruct);
270 return ((DIR *) dirstruct);
271 }
272
fdopendir(int fd)273 DIR *fdopendir(int fd)
274 {
275 DIR *dir;
276 struct dir_s *dirstruct;
277 struct stat st;
278
279 if (!real_fdopendir)
280 setup_ptr();
281
282 DEBUG_DIR(printf("fdopendir(%d) (%d open)\n", fd, num_open++));
283 dir = (*real_fdopendir)(fd);
284 if (!dir)
285 return NULL;
286
287 dirstruct = alloc_dirstruct(dir);
288 if (!dirstruct) {
289 (*real_closedir)(dir);
290 errno = -ENOMEM;
291 return NULL;
292 }
293
294 if (max_dirsize && (fstat(fd, &st) == 0) &&
295 (st.st_size > max_dirsize)) {
296 DEBUG_DIR(printf("Directory size %ld, using direct readdir\n",
297 st.st_size));
298 dirstruct->dir = dir;
299 dirstruct->direct = 1;
300 return (DIR *) dirstruct;
301 }
302
303 cache_dirstruct(dirstruct);
304 return ((DIR *) dirstruct);
305 }
306
closedir(DIR * dir)307 int closedir(DIR *dir)
308 {
309 struct dir_s *dirstruct = (struct dir_s *) dir;
310
311 DEBUG_DIR(printf("Closedir (%d open)\n", --num_open));
312 if (dirstruct->dir)
313 (*real_closedir)(dirstruct->dir);
314
315 free_cached_dir(dirstruct);
316 free(dirstruct);
317 return 0;
318 }
319
readdir(DIR * dir)320 struct dirent *readdir(DIR *dir)
321 {
322 struct dir_s *dirstruct = (struct dir_s *) dir;
323 struct dirent_s *ds;
324
325 if (dirstruct->direct)
326 return (*real_readdir)(dirstruct->dir);
327
328 if (dirstruct->pos >= dirstruct->num)
329 return NULL;
330
331 ds = &dirstruct->dp[dirstruct->pos++];
332 dirstruct->ret_dir.d_ino = ds->d_ino;
333 dirstruct->ret_dir.d_off = ds->d_off;
334 dirstruct->ret_dir.d_reclen = ds->d_reclen;
335 dirstruct->ret_dir.d_type = ds->d_type;
336 strncpy(dirstruct->ret_dir.d_name, ds->d_name,
337 sizeof(dirstruct->ret_dir.d_name));
338
339 return (&dirstruct->ret_dir);
340 }
341
readdir_r(DIR * dir,struct dirent * entry,struct dirent ** result)342 int readdir_r(DIR *dir, struct dirent *entry, struct dirent **result)
343 {
344 struct dir_s *dirstruct = (struct dir_s *) dir;
345 struct dirent_s *ds;
346
347 if (dirstruct->direct)
348 return (*real_readdir_r)(dirstruct->dir, entry, result);
349
350 pthread_mutex_lock(&(dirstruct->lock));
351 if (dirstruct->pos >= dirstruct->num) {
352 *result = NULL;
353 } else {
354 ds = &dirstruct->dp[dirstruct->pos++];
355 entry->d_ino = ds->d_ino;
356 entry->d_off = ds->d_off;
357 entry->d_reclen = ds->d_reclen;
358 entry->d_type = ds->d_type;
359 strncpy(entry->d_name, ds->d_name, sizeof(entry->d_name));
360 *result = entry;
361 }
362 pthread_mutex_unlock(&(dirstruct->lock));
363 return 0;
364 }
365
readdir64(DIR * dir)366 struct dirent64 *readdir64(DIR *dir)
367 {
368 struct dir_s *dirstruct = (struct dir_s *) dir;
369 struct dirent_s *ds;
370
371 if (dirstruct->direct)
372 return (*real_readdir64)(dirstruct->dir);
373
374 if (dirstruct->pos >= dirstruct->num)
375 return NULL;
376
377 ds = &dirstruct->dp[dirstruct->pos++];
378 dirstruct->ret_dir64.d_ino = ds->d_ino;
379 dirstruct->ret_dir64.d_off = ds->d_off;
380 dirstruct->ret_dir64.d_reclen = ds->d_reclen;
381 dirstruct->ret_dir64.d_type = ds->d_type;
382 strncpy(dirstruct->ret_dir64.d_name, ds->d_name,
383 sizeof(dirstruct->ret_dir64.d_name));
384
385 return (&dirstruct->ret_dir64);
386 }
387
readdir64_r(DIR * __restrict dir,struct dirent64 * __restrict entry,struct dirent64 ** __restrict result)388 int readdir64_r (DIR *__restrict dir,
389 struct dirent64 *__restrict entry,
390 struct dirent64 **__restrict result)
391 {
392 struct dir_s *dirstruct = (struct dir_s *) dir;
393 struct dirent_s *ds;
394
395 if (dirstruct->direct)
396 return (*real_readdir64_r)(dir, entry, result);
397 pthread_mutex_lock(&(dirstruct->lock));
398 if (dirstruct->pos >= dirstruct->num) {
399 *result = NULL;
400 } else {
401 ds = &dirstruct->dp[dirstruct->pos++];
402 entry->d_ino = ds->d_ino;
403 entry->d_off = ds->d_off;
404 entry->d_reclen = ds->d_reclen;
405 entry->d_type = ds->d_type;
406 strncpy(entry->d_name, ds->d_name,
407 sizeof(entry->d_name));
408 *result = entry;
409 }
410 pthread_mutex_unlock(&(dirstruct->lock));
411 return 0;
412 }
413
telldir(DIR * dir)414 off_t telldir(DIR *dir)
415 {
416 struct dir_s *dirstruct = (struct dir_s *) dir;
417
418 if (dirstruct->direct)
419 return (*real_telldir)(dirstruct->dir);
420
421 return ((off_t) dirstruct->pos);
422 }
423
seekdir(DIR * dir,off_t offset)424 void seekdir(DIR *dir, off_t offset)
425 {
426 struct dir_s *dirstruct = (struct dir_s *) dir;
427
428 if (dirstruct->direct) {
429 (*real_seekdir)(dirstruct->dir, offset);
430 return;
431 }
432
433 dirstruct->pos = offset;
434 }
435
rewinddir(DIR * dir)436 void rewinddir(DIR *dir)
437 {
438 struct dir_s *dirstruct = (struct dir_s *) dir;
439
440 (*real_rewinddir)(dirstruct->dir);
441 if (dirstruct->direct)
442 return;
443
444 pthread_mutex_lock(&(dirstruct->lock));
445 dirstruct->pos = 0;
446 free_cached_dir(dirstruct);
447 cache_dirstruct(dirstruct);
448 pthread_mutex_unlock(&(dirstruct->lock));
449 }
450
dirfd(DIR * dir)451 int dirfd(DIR *dir)
452 {
453 struct dir_s *dirstruct = (struct dir_s *) dir;
454 int fd = (*real_dirfd)(dirstruct->dir);
455
456 DEBUG_DIR(printf("dirfd %d, %p\n", fd, real_dirfd));
457 return fd;
458 }
459