1 /* Cache memory handling.
2 Copyright (C) 2004-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; version 2 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
17
18 #include <assert.h>
19 #include <errno.h>
20 #include <error.h>
21 #include <fcntl.h>
22 #include <inttypes.h>
23 #include <libintl.h>
24 #include <limits.h>
25 #include <obstack.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <unistd.h>
29 #include <sys/mman.h>
30 #include <sys/param.h>
31
32 #include "dbg_log.h"
33 #include "nscd.h"
34
35
36 static int
sort_he(const void * p1,const void * p2)37 sort_he (const void *p1, const void *p2)
38 {
39 struct hashentry *h1 = *(struct hashentry **) p1;
40 struct hashentry *h2 = *(struct hashentry **) p2;
41
42 if (h1 < h2)
43 return -1;
44 if (h1 > h2)
45 return 1;
46 return 0;
47 }
48
49
50 static int
sort_he_data(const void * p1,const void * p2)51 sort_he_data (const void *p1, const void *p2)
52 {
53 struct hashentry *h1 = *(struct hashentry **) p1;
54 struct hashentry *h2 = *(struct hashentry **) p2;
55
56 if (h1->packet < h2->packet)
57 return -1;
58 if (h1->packet > h2->packet)
59 return 1;
60 return 0;
61 }
62
63
64 /* Basic definitions for the bitmap implementation. Only BITMAP_T
65 needs to be changed to choose a different word size. */
66 #define BITMAP_T uint8_t
67 #define BITS (CHAR_BIT * sizeof (BITMAP_T))
68 #define ALLBITS ((((BITMAP_T) 1) << BITS) - 1)
69 #define HIGHBIT (((BITMAP_T) 1) << (BITS - 1))
70
71
72 static void
markrange(BITMAP_T * mark,ref_t start,size_t len)73 markrange (BITMAP_T *mark, ref_t start, size_t len)
74 {
75 /* Adjust parameters for block alignment. */
76 assert ((start & BLOCK_ALIGN_M1) == 0);
77 start /= BLOCK_ALIGN;
78 len = (len + BLOCK_ALIGN_M1) / BLOCK_ALIGN;
79
80 size_t elem = start / BITS;
81
82 if (start % BITS != 0)
83 {
84 if (start % BITS + len <= BITS)
85 {
86 /* All fits in the partial byte. */
87 mark[elem] |= (ALLBITS >> (BITS - len)) << (start % BITS);
88 return;
89 }
90
91 mark[elem++] |= ALLBITS << (start % BITS);
92 len -= BITS - (start % BITS);
93 }
94
95 while (len >= BITS)
96 {
97 mark[elem++] = ALLBITS;
98 len -= BITS;
99 }
100
101 if (len > 0)
102 mark[elem] |= ALLBITS >> (BITS - len);
103 }
104
105
106 void
gc(struct database_dyn * db)107 gc (struct database_dyn *db)
108 {
109 /* We need write access. */
110 pthread_rwlock_wrlock (&db->lock);
111
112 /* And the memory handling lock. */
113 pthread_mutex_lock (&db->memlock);
114
115 /* We need an array representing the data area. All memory
116 allocation is BLOCK_ALIGN aligned so this is the level at which
117 we have to look at the memory. We use a mark and sweep algorithm
118 where the marks are placed in this array. */
119 assert (db->head->first_free % BLOCK_ALIGN == 0);
120
121 BITMAP_T *mark;
122 bool mark_use_malloc;
123 /* In prune_cache we are also using a dynamically allocated array.
124 If the array in the caller is too large we have malloc'ed it. */
125 size_t stack_used = sizeof (bool) * db->head->module;
126 if (__glibc_unlikely (stack_used > MAX_STACK_USE))
127 stack_used = 0;
128 size_t nmark = (db->head->first_free / BLOCK_ALIGN + BITS - 1) / BITS;
129 size_t memory_needed = nmark * sizeof (BITMAP_T);
130 if (__glibc_likely (stack_used + memory_needed <= MAX_STACK_USE))
131 {
132 mark = (BITMAP_T *) alloca_account (memory_needed, stack_used);
133 mark_use_malloc = false;
134 memset (mark, '\0', memory_needed);
135 }
136 else
137 {
138 mark = (BITMAP_T *) xcalloc (1, memory_needed);
139 mark_use_malloc = true;
140 }
141
142 /* Create an array which can hold pointer to all the entries in hash
143 entries. */
144 memory_needed = 2 * db->head->nentries * sizeof (struct hashentry *);
145 struct hashentry **he;
146 struct hashentry **he_data;
147 bool he_use_malloc;
148 if (__glibc_likely (stack_used + memory_needed <= MAX_STACK_USE))
149 {
150 he = alloca_account (memory_needed, stack_used);
151 he_use_malloc = false;
152 }
153 else
154 {
155 he = xmalloc (memory_needed);
156 he_use_malloc = true;
157 }
158 he_data = &he[db->head->nentries];
159
160 size_t cnt = 0;
161 for (size_t idx = 0; idx < db->head->module; ++idx)
162 {
163 ref_t *prevp = &db->head->array[idx];
164 ref_t run = *prevp;
165
166 while (run != ENDREF)
167 {
168 assert (cnt < db->head->nentries);
169 he[cnt] = (struct hashentry *) (db->data + run);
170
171 he[cnt]->prevp = prevp;
172 prevp = &he[cnt]->next;
173
174 /* This is the hash entry itself. */
175 markrange (mark, run, sizeof (struct hashentry));
176
177 /* Add the information for the data itself. We do this
178 only for the one special entry marked with FIRST. */
179 if (he[cnt]->first)
180 {
181 struct datahead *dh
182 = (struct datahead *) (db->data + he[cnt]->packet);
183 markrange (mark, he[cnt]->packet, dh->allocsize);
184 }
185
186 run = he[cnt]->next;
187
188 ++cnt;
189 }
190 }
191 assert (cnt == db->head->nentries);
192
193 /* Sort the entries by the addresses of the referenced data. All
194 the entries pointing to the same DATAHEAD object will have the
195 same key. Stability of the sorting is unimportant. */
196 memcpy (he_data, he, cnt * sizeof (struct hashentry *));
197 qsort (he_data, cnt, sizeof (struct hashentry *), sort_he_data);
198
199 /* Sort the entries by their address. */
200 qsort (he, cnt, sizeof (struct hashentry *), sort_he);
201
202 #define obstack_chunk_alloc xmalloc
203 #define obstack_chunk_free free
204 struct obstack ob;
205 obstack_init (&ob);
206
207 /* Determine the highest used address. */
208 size_t high = nmark;
209 while (high > 0 && mark[high - 1] == 0)
210 --high;
211
212 /* No memory used. */
213 if (high == 0)
214 {
215 db->head->first_free = 0;
216 goto out;
217 }
218
219 /* Determine the highest offset. */
220 BITMAP_T mask = HIGHBIT;
221 ref_t highref = (high * BITS - 1) * BLOCK_ALIGN;
222 while ((mark[high - 1] & mask) == 0)
223 {
224 mask >>= 1;
225 highref -= BLOCK_ALIGN;
226 }
227
228 /* Now we can iterate over the MARK array and find bits which are not
229 set. These represent memory which can be recovered. */
230 size_t byte = 0;
231 /* Find the first gap. */
232 while (byte < high && mark[byte] == ALLBITS)
233 ++byte;
234
235 if (byte == high
236 || (byte == high - 1 && (mark[byte] & ~(mask | (mask - 1))) == 0))
237 /* No gap. */
238 goto out;
239
240 mask = 1;
241 cnt = 0;
242 while ((mark[byte] & mask) != 0)
243 {
244 ++cnt;
245 mask <<= 1;
246 }
247 ref_t off_free = (byte * BITS + cnt) * BLOCK_ALIGN;
248 assert (off_free <= db->head->first_free);
249
250 struct hashentry **next_hash = he;
251 struct hashentry **next_data = he_data;
252
253 /* Skip over the hash entries in the first block which does not get
254 moved. */
255 while (next_hash < &he[db->head->nentries]
256 && *next_hash < (struct hashentry *) (db->data + off_free))
257 ++next_hash;
258
259 while (next_data < &he_data[db->head->nentries]
260 && (*next_data)->packet < off_free)
261 ++next_data;
262
263
264 /* Now we start modifying the data. Make sure all readers of the
265 data are aware of this and temporarily don't use the data. */
266 atomic_fetch_add_relaxed (&db->head->gc_cycle, 1);
267 assert ((db->head->gc_cycle & 1) == 1);
268
269
270 /* We do not perform the move operations right away since the
271 he_data array is not sorted by the address of the data. */
272 struct moveinfo
273 {
274 void *from;
275 void *to;
276 size_t size;
277 struct moveinfo *next;
278 } *moves = NULL;
279
280 while (byte < high)
281 {
282 /* Search for the next filled block. BYTE is the index of the
283 entry in MARK, MASK is the bit, and CNT is the bit number.
284 OFF_FILLED is the corresponding offset. */
285 if ((mark[byte] & ~(mask - 1)) == 0)
286 {
287 /* No other bit set in the same element of MARK. Search in the
288 following memory. */
289 do
290 ++byte;
291 while (byte < high && mark[byte] == 0);
292
293 if (byte == high)
294 /* That was it. */
295 break;
296
297 mask = 1;
298 cnt = 0;
299 }
300 /* Find the exact bit. */
301 while ((mark[byte] & mask) == 0)
302 {
303 ++cnt;
304 mask <<= 1;
305 }
306
307 ref_t off_alloc = (byte * BITS + cnt) * BLOCK_ALIGN;
308 assert (off_alloc <= db->head->first_free);
309
310 /* Find the end of the used area. */
311 if ((mark[byte] & ~(mask - 1)) == (BITMAP_T) ~(mask - 1))
312 {
313 /* All other bits set. Search the next bytes in MARK. */
314 do
315 ++byte;
316 while (byte < high && mark[byte] == ALLBITS);
317
318 mask = 1;
319 cnt = 0;
320 }
321 if (byte < high)
322 {
323 /* Find the exact bit. */
324 while ((mark[byte] & mask) != 0)
325 {
326 ++cnt;
327 mask <<= 1;
328 }
329 }
330
331 ref_t off_allocend = (byte * BITS + cnt) * BLOCK_ALIGN;
332 assert (off_allocend <= db->head->first_free);
333 /* Now we know that we can copy the area from OFF_ALLOC to
334 OFF_ALLOCEND (not included) to the memory starting at
335 OFF_FREE. First fix up all the entries for the
336 displacement. */
337 ref_t disp = off_alloc - off_free;
338
339 struct moveinfo *new_move;
340 if (__builtin_expect (stack_used + sizeof (*new_move) <= MAX_STACK_USE,
341 1))
342 new_move = alloca_account (sizeof (*new_move), stack_used);
343 else
344 new_move = obstack_alloc (&ob, sizeof (*new_move));
345 new_move->from = db->data + off_alloc;
346 new_move->to = db->data + off_free;
347 new_move->size = off_allocend - off_alloc;
348 /* Create a circular list to be always able to append at the end. */
349 if (moves == NULL)
350 moves = new_move->next = new_move;
351 else
352 {
353 new_move->next = moves->next;
354 moves = moves->next = new_move;
355 }
356
357 /* The following loop will prepare to move this much data. */
358 off_free += off_allocend - off_alloc;
359
360 while (off_alloc < off_allocend)
361 {
362 /* Determine whether the next entry is for a hash entry or
363 the data. */
364 if ((struct hashentry *) (db->data + off_alloc) == *next_hash)
365 {
366 /* Just correct the forward reference. */
367 *(*next_hash++)->prevp -= disp;
368
369 off_alloc += ((sizeof (struct hashentry) + BLOCK_ALIGN_M1)
370 & ~BLOCK_ALIGN_M1);
371 }
372 else
373 {
374 assert (next_data < &he_data[db->head->nentries]);
375 assert ((*next_data)->packet == off_alloc);
376
377 struct datahead *dh = (struct datahead *) (db->data + off_alloc);
378 do
379 {
380 assert ((*next_data)->key >= (*next_data)->packet);
381 assert ((*next_data)->key + (*next_data)->len
382 <= (*next_data)->packet + dh->allocsize);
383
384 (*next_data)->packet -= disp;
385 (*next_data)->key -= disp;
386 ++next_data;
387 }
388 while (next_data < &he_data[db->head->nentries]
389 && (*next_data)->packet == off_alloc);
390
391 off_alloc += (dh->allocsize + BLOCK_ALIGN_M1) & ~BLOCK_ALIGN_M1;
392 }
393 }
394 assert (off_alloc == off_allocend);
395
396 assert (off_alloc <= db->head->first_free);
397 if (off_alloc == db->head->first_free)
398 /* We are done, that was the last block. */
399 break;
400 }
401 assert (next_hash == &he[db->head->nentries]);
402 assert (next_data == &he_data[db->head->nentries]);
403
404 /* Now perform the actual moves. */
405 if (moves != NULL)
406 {
407 struct moveinfo *runp = moves->next;
408 do
409 {
410 assert ((char *) runp->to >= db->data);
411 assert ((char *) runp->to + runp->size
412 <= db->data + db->head->first_free);
413 assert ((char *) runp->from >= db->data);
414 assert ((char *) runp->from + runp->size
415 <= db->data + db->head->first_free);
416
417 /* The regions may overlap. */
418 memmove (runp->to, runp->from, runp->size);
419 runp = runp->next;
420 }
421 while (runp != moves->next);
422
423 if (__glibc_unlikely (debug_level >= 3))
424 dbg_log (_("freed %zu bytes in %s cache"),
425 (size_t) (db->head->first_free
426 - ((char *) moves->to + moves->size - db->data)),
427 dbnames[db - dbs]);
428
429 /* The byte past the end of the last copied block is the next
430 available byte. */
431 db->head->first_free = (char *) moves->to + moves->size - db->data;
432
433 /* Consistency check. */
434 if (__glibc_unlikely (debug_level >= 3))
435 {
436 for (size_t idx = 0; idx < db->head->module; ++idx)
437 {
438 ref_t run = db->head->array[idx];
439 size_t cnt = 0;
440
441 while (run != ENDREF)
442 {
443 if (run + sizeof (struct hashentry) > db->head->first_free)
444 {
445 dbg_log ("entry %zu in hash bucket %zu out of bounds: "
446 "%" PRIu32 "+%zu > %zu\n",
447 cnt, idx, run, sizeof (struct hashentry),
448 (size_t) db->head->first_free);
449 break;
450 }
451
452 struct hashentry *he = (struct hashentry *) (db->data + run);
453
454 if (he->key + he->len > db->head->first_free)
455 dbg_log ("key of entry %zu in hash bucket %zu out of "
456 "bounds: %" PRIu32 "+%zu > %zu\n",
457 cnt, idx, he->key, (size_t) he->len,
458 (size_t) db->head->first_free);
459
460 if (he->packet + sizeof (struct datahead)
461 > db->head->first_free)
462 dbg_log ("packet of entry %zu in hash bucket %zu out of "
463 "bounds: %" PRIu32 "+%zu > %zu\n",
464 cnt, idx, he->packet, sizeof (struct datahead),
465 (size_t) db->head->first_free);
466 else
467 {
468 struct datahead *dh = (struct datahead *) (db->data
469 + he->packet);
470 if (he->packet + dh->allocsize
471 > db->head->first_free)
472 dbg_log ("full key of entry %zu in hash bucket %zu "
473 "out of bounds: %" PRIu32 "+%zu > %zu",
474 cnt, idx, he->packet, (size_t) dh->allocsize,
475 (size_t) db->head->first_free);
476 }
477
478 run = he->next;
479 ++cnt;
480 }
481 }
482 }
483 }
484
485 /* Make sure the data on disk is updated. */
486 if (db->persistent)
487 msync (db->head, db->data + db->head->first_free - (char *) db->head,
488 MS_ASYNC);
489
490
491 /* Now we are done modifying the data. */
492 atomic_fetch_add_relaxed (&db->head->gc_cycle, 1);
493 assert ((db->head->gc_cycle & 1) == 0);
494
495 /* We are done. */
496 out:
497 pthread_mutex_unlock (&db->memlock);
498 pthread_rwlock_unlock (&db->lock);
499
500 if (he_use_malloc)
501 free (he);
502 if (mark_use_malloc)
503 free (mark);
504
505 obstack_free (&ob, NULL);
506 }
507
508
509 void *
mempool_alloc(struct database_dyn * db,size_t len,int data_alloc)510 mempool_alloc (struct database_dyn *db, size_t len, int data_alloc)
511 {
512 /* Make sure LEN is a multiple of our maximum alignment so we can
513 keep track of used memory is multiples of this alignment value. */
514 if ((len & BLOCK_ALIGN_M1) != 0)
515 len += BLOCK_ALIGN - (len & BLOCK_ALIGN_M1);
516
517 if (data_alloc)
518 pthread_rwlock_rdlock (&db->lock);
519
520 pthread_mutex_lock (&db->memlock);
521
522 assert ((db->head->first_free & BLOCK_ALIGN_M1) == 0);
523
524 bool tried_resize = false;
525 void *res;
526 retry:
527 res = db->data + db->head->first_free;
528
529 if (__glibc_unlikely (db->head->first_free + len > db->head->data_size))
530 {
531 if (! tried_resize)
532 {
533 /* Try to resize the database. Grow size of 1/8th. */
534 size_t oldtotal = (sizeof (struct database_pers_head)
535 + roundup (db->head->module * sizeof (ref_t),
536 ALIGN)
537 + db->head->data_size);
538 size_t new_data_size = (db->head->data_size
539 + MAX (2 * len, db->head->data_size / 8));
540 size_t newtotal = (sizeof (struct database_pers_head)
541 + roundup (db->head->module * sizeof (ref_t), ALIGN)
542 + new_data_size);
543 if (newtotal > db->max_db_size)
544 {
545 new_data_size -= newtotal - db->max_db_size;
546 newtotal = db->max_db_size;
547 }
548
549 if (db->mmap_used && newtotal > oldtotal
550 /* We only have to adjust the file size. The new pages
551 become magically available. */
552 && TEMP_FAILURE_RETRY_VAL (posix_fallocate (db->wr_fd, oldtotal,
553 newtotal
554 - oldtotal)) == 0)
555 {
556 db->head->data_size = new_data_size;
557 tried_resize = true;
558 goto retry;
559 }
560 }
561
562 if (data_alloc)
563 pthread_rwlock_unlock (&db->lock);
564
565 if (! db->last_alloc_failed)
566 {
567 dbg_log (_("no more memory for database '%s'"), dbnames[db - dbs]);
568
569 db->last_alloc_failed = true;
570 }
571
572 ++db->head->addfailed;
573
574 /* No luck. */
575 res = NULL;
576 }
577 else
578 {
579 db->head->first_free += len;
580
581 db->last_alloc_failed = false;
582
583 }
584
585 pthread_mutex_unlock (&db->memlock);
586
587 return res;
588 }
589