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1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ | |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2012 Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <errno.h> | |
23 | #include <stdlib.h> | |
24 | #include <sys/mman.h> | |
25 | #include <string.h> | |
26 | ||
27 | #include "hashmap.h" | |
28 | #include "list.h" | |
29 | #include "log.h" | |
30 | #include "util.h" | |
31 | #include "macro.h" | |
32 | #include "mmap-cache.h" | |
33 | ||
34 | typedef struct Window Window; | |
35 | typedef struct Context Context; | |
36 | typedef struct FileDescriptor FileDescriptor; | |
37 | ||
38 | struct Window { | |
39 | MMapCache *cache; | |
40 | ||
41 | bool keep_always; | |
42 | bool in_unused; | |
43 | ||
44 | int prot; | |
45 | void *ptr; | |
46 | uint64_t offset; | |
47 | size_t size; | |
48 | ||
49 | FileDescriptor *fd; | |
50 | ||
51 | LIST_FIELDS(Window, by_fd); | |
52 | LIST_FIELDS(Window, unused); | |
53 | ||
54 | LIST_HEAD(Context, contexts); | |
55 | }; | |
56 | ||
57 | struct Context { | |
58 | MMapCache *cache; | |
59 | unsigned id; | |
60 | Window *window; | |
61 | ||
62 | LIST_FIELDS(Context, by_window); | |
63 | }; | |
64 | ||
65 | struct FileDescriptor { | |
66 | MMapCache *cache; | |
67 | int fd; | |
68 | LIST_HEAD(Window, windows); | |
69 | }; | |
70 | ||
71 | struct MMapCache { | |
72 | int n_ref; | |
73 | unsigned n_windows; | |
74 | ||
75 | unsigned n_hit, n_missed; | |
76 | ||
77 | ||
78 | Hashmap *fds; | |
79 | Hashmap *contexts; | |
80 | ||
81 | LIST_HEAD(Window, unused); | |
82 | Window *last_unused; | |
83 | }; | |
84 | ||
85 | #define WINDOWS_MIN 64 | |
86 | ||
87 | #ifdef ENABLE_DEBUG_MMAP_CACHE | |
88 | /* Tiny windows increase mmap activity and the chance of exposing unsafe use. */ | |
89 | # define WINDOW_SIZE (page_size()) | |
90 | #else | |
91 | # define WINDOW_SIZE (8ULL*1024ULL*1024ULL) | |
92 | #endif | |
93 | ||
94 | MMapCache* mmap_cache_new(void) { | |
95 | MMapCache *m; | |
96 | ||
97 | m = new0(MMapCache, 1); | |
98 | if (!m) | |
99 | return NULL; | |
100 | ||
101 | m->n_ref = 1; | |
102 | return m; | |
103 | } | |
104 | ||
105 | MMapCache* mmap_cache_ref(MMapCache *m) { | |
106 | assert(m); | |
107 | assert(m->n_ref > 0); | |
108 | ||
109 | m->n_ref ++; | |
110 | return m; | |
111 | } | |
112 | ||
113 | static void window_unlink(Window *w) { | |
114 | Context *c; | |
115 | ||
116 | assert(w); | |
117 | ||
118 | if (w->ptr) | |
119 | munmap(w->ptr, w->size); | |
120 | ||
121 | if (w->fd) | |
122 | LIST_REMOVE(by_fd, w->fd->windows, w); | |
123 | ||
124 | if (w->in_unused) { | |
125 | if (w->cache->last_unused == w) | |
126 | w->cache->last_unused = w->unused_prev; | |
127 | ||
128 | LIST_REMOVE(unused, w->cache->unused, w); | |
129 | } | |
130 | ||
131 | LIST_FOREACH(by_window, c, w->contexts) { | |
132 | assert(c->window == w); | |
133 | c->window = NULL; | |
134 | } | |
135 | } | |
136 | ||
137 | static void window_free(Window *w) { | |
138 | assert(w); | |
139 | ||
140 | window_unlink(w); | |
141 | w->cache->n_windows--; | |
142 | free(w); | |
143 | } | |
144 | ||
145 | _pure_ static bool window_matches(Window *w, int fd, int prot, uint64_t offset, size_t size) { | |
146 | assert(w); | |
147 | assert(fd >= 0); | |
148 | assert(size > 0); | |
149 | ||
150 | return | |
151 | w->fd && | |
152 | fd == w->fd->fd && | |
153 | prot == w->prot && | |
154 | offset >= w->offset && | |
155 | offset + size <= w->offset + w->size; | |
156 | } | |
157 | ||
158 | static Window *window_add(MMapCache *m) { | |
159 | Window *w; | |
160 | ||
161 | assert(m); | |
162 | ||
163 | if (!m->last_unused || m->n_windows <= WINDOWS_MIN) { | |
164 | ||
165 | /* Allocate a new window */ | |
166 | w = new0(Window, 1); | |
167 | if (!w) | |
168 | return NULL; | |
169 | m->n_windows++; | |
170 | } else { | |
171 | ||
172 | /* Reuse an existing one */ | |
173 | w = m->last_unused; | |
174 | window_unlink(w); | |
175 | zero(*w); | |
176 | } | |
177 | ||
178 | w->cache = m; | |
179 | return w; | |
180 | } | |
181 | ||
182 | static void context_detach_window(Context *c) { | |
183 | Window *w; | |
184 | ||
185 | assert(c); | |
186 | ||
187 | if (!c->window) | |
188 | return; | |
189 | ||
190 | w = c->window; | |
191 | c->window = NULL; | |
192 | LIST_REMOVE(by_window, w->contexts, c); | |
193 | ||
194 | if (!w->contexts && !w->keep_always) { | |
195 | /* Not used anymore? */ | |
196 | #ifdef ENABLE_DEBUG_MMAP_CACHE | |
197 | /* Unmap unused windows immediately to expose use-after-unmap | |
198 | * by SIGSEGV. */ | |
199 | window_free(w); | |
200 | #else | |
201 | LIST_PREPEND(unused, c->cache->unused, w); | |
202 | if (!c->cache->last_unused) | |
203 | c->cache->last_unused = w; | |
204 | ||
205 | w->in_unused = true; | |
206 | #endif | |
207 | } | |
208 | } | |
209 | ||
210 | static void context_attach_window(Context *c, Window *w) { | |
211 | assert(c); | |
212 | assert(w); | |
213 | ||
214 | if (c->window == w) | |
215 | return; | |
216 | ||
217 | context_detach_window(c); | |
218 | ||
219 | if (w->in_unused) { | |
220 | /* Used again? */ | |
221 | LIST_REMOVE(unused, c->cache->unused, w); | |
222 | if (c->cache->last_unused == w) | |
223 | c->cache->last_unused = w->unused_prev; | |
224 | ||
225 | w->in_unused = false; | |
226 | } | |
227 | ||
228 | c->window = w; | |
229 | LIST_PREPEND(by_window, w->contexts, c); | |
230 | } | |
231 | ||
232 | static Context *context_add(MMapCache *m, unsigned id) { | |
233 | Context *c; | |
234 | int r; | |
235 | ||
236 | assert(m); | |
237 | ||
238 | c = hashmap_get(m->contexts, UINT_TO_PTR(id + 1)); | |
239 | if (c) | |
240 | return c; | |
241 | ||
242 | r = hashmap_ensure_allocated(&m->contexts, NULL); | |
243 | if (r < 0) | |
244 | return NULL; | |
245 | ||
246 | c = new0(Context, 1); | |
247 | if (!c) | |
248 | return NULL; | |
249 | ||
250 | c->cache = m; | |
251 | c->id = id; | |
252 | ||
253 | r = hashmap_put(m->contexts, UINT_TO_PTR(id + 1), c); | |
254 | if (r < 0) { | |
255 | free(c); | |
256 | return NULL; | |
257 | } | |
258 | ||
259 | return c; | |
260 | } | |
261 | ||
262 | static void context_free(Context *c) { | |
263 | assert(c); | |
264 | ||
265 | context_detach_window(c); | |
266 | ||
267 | if (c->cache) | |
268 | assert_se(hashmap_remove(c->cache->contexts, UINT_TO_PTR(c->id + 1))); | |
269 | ||
270 | free(c); | |
271 | } | |
272 | ||
273 | static void fd_free(FileDescriptor *f) { | |
274 | assert(f); | |
275 | ||
276 | while (f->windows) | |
277 | window_free(f->windows); | |
278 | ||
279 | if (f->cache) | |
280 | assert_se(hashmap_remove(f->cache->fds, INT_TO_PTR(f->fd + 1))); | |
281 | ||
282 | free(f); | |
283 | } | |
284 | ||
285 | static FileDescriptor* fd_add(MMapCache *m, int fd) { | |
286 | FileDescriptor *f; | |
287 | int r; | |
288 | ||
289 | assert(m); | |
290 | assert(fd >= 0); | |
291 | ||
292 | f = hashmap_get(m->fds, INT_TO_PTR(fd + 1)); | |
293 | if (f) | |
294 | return f; | |
295 | ||
296 | r = hashmap_ensure_allocated(&m->fds, NULL); | |
297 | if (r < 0) | |
298 | return NULL; | |
299 | ||
300 | f = new0(FileDescriptor, 1); | |
301 | if (!f) | |
302 | return NULL; | |
303 | ||
304 | f->cache = m; | |
305 | f->fd = fd; | |
306 | ||
307 | r = hashmap_put(m->fds, UINT_TO_PTR(fd + 1), f); | |
308 | if (r < 0) { | |
309 | free(f); | |
310 | return NULL; | |
311 | } | |
312 | ||
313 | return f; | |
314 | } | |
315 | ||
316 | static void mmap_cache_free(MMapCache *m) { | |
317 | Context *c; | |
318 | FileDescriptor *f; | |
319 | ||
320 | assert(m); | |
321 | ||
322 | while ((c = hashmap_first(m->contexts))) | |
323 | context_free(c); | |
324 | ||
325 | hashmap_free(m->contexts); | |
326 | ||
327 | while ((f = hashmap_first(m->fds))) | |
328 | fd_free(f); | |
329 | ||
330 | hashmap_free(m->fds); | |
331 | ||
332 | while (m->unused) | |
333 | window_free(m->unused); | |
334 | ||
335 | free(m); | |
336 | } | |
337 | ||
338 | MMapCache* mmap_cache_unref(MMapCache *m) { | |
339 | assert(m); | |
340 | assert(m->n_ref > 0); | |
341 | ||
342 | m->n_ref --; | |
343 | if (m->n_ref == 0) | |
344 | mmap_cache_free(m); | |
345 | ||
346 | return NULL; | |
347 | } | |
348 | ||
349 | static int make_room(MMapCache *m) { | |
350 | assert(m); | |
351 | ||
352 | if (!m->last_unused) | |
353 | return 0; | |
354 | ||
355 | window_free(m->last_unused); | |
356 | return 1; | |
357 | } | |
358 | ||
359 | static int try_context( | |
360 | MMapCache *m, | |
361 | int fd, | |
362 | int prot, | |
363 | unsigned context, | |
364 | bool keep_always, | |
365 | uint64_t offset, | |
366 | size_t size, | |
367 | void **ret) { | |
368 | ||
369 | Context *c; | |
370 | ||
371 | assert(m); | |
372 | assert(m->n_ref > 0); | |
373 | assert(fd >= 0); | |
374 | assert(size > 0); | |
375 | assert(ret); | |
376 | ||
377 | c = hashmap_get(m->contexts, UINT_TO_PTR(context+1)); | |
378 | if (!c) | |
379 | return 0; | |
380 | ||
381 | assert(c->id == context); | |
382 | ||
383 | if (!c->window) | |
384 | return 0; | |
385 | ||
386 | if (!window_matches(c->window, fd, prot, offset, size)) { | |
387 | ||
388 | /* Drop the reference to the window, since it's unnecessary now */ | |
389 | context_detach_window(c); | |
390 | return 0; | |
391 | } | |
392 | ||
393 | c->window->keep_always |= keep_always; | |
394 | ||
395 | *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset); | |
396 | return 1; | |
397 | } | |
398 | ||
399 | static int find_mmap( | |
400 | MMapCache *m, | |
401 | int fd, | |
402 | int prot, | |
403 | unsigned context, | |
404 | bool keep_always, | |
405 | uint64_t offset, | |
406 | size_t size, | |
407 | void **ret) { | |
408 | ||
409 | FileDescriptor *f; | |
410 | Window *w; | |
411 | Context *c; | |
412 | ||
413 | assert(m); | |
414 | assert(m->n_ref > 0); | |
415 | assert(fd >= 0); | |
416 | assert(size > 0); | |
417 | ||
418 | f = hashmap_get(m->fds, INT_TO_PTR(fd + 1)); | |
419 | if (!f) | |
420 | return 0; | |
421 | ||
422 | assert(f->fd == fd); | |
423 | ||
424 | LIST_FOREACH(by_fd, w, f->windows) | |
425 | if (window_matches(w, fd, prot, offset, size)) | |
426 | break; | |
427 | ||
428 | if (!w) | |
429 | return 0; | |
430 | ||
431 | c = context_add(m, context); | |
432 | if (!c) | |
433 | return -ENOMEM; | |
434 | ||
435 | context_attach_window(c, w); | |
436 | w->keep_always += keep_always; | |
437 | ||
438 | *ret = (uint8_t*) w->ptr + (offset - w->offset); | |
439 | return 1; | |
440 | } | |
441 | ||
442 | static int add_mmap( | |
443 | MMapCache *m, | |
444 | int fd, | |
445 | int prot, | |
446 | unsigned context, | |
447 | bool keep_always, | |
448 | uint64_t offset, | |
449 | size_t size, | |
450 | struct stat *st, | |
451 | void **ret) { | |
452 | ||
453 | uint64_t woffset, wsize; | |
454 | Context *c; | |
455 | FileDescriptor *f; | |
456 | Window *w; | |
457 | void *d; | |
458 | int r; | |
459 | ||
460 | assert(m); | |
461 | assert(m->n_ref > 0); | |
462 | assert(fd >= 0); | |
463 | assert(size > 0); | |
464 | assert(ret); | |
465 | ||
466 | woffset = offset & ~((uint64_t) page_size() - 1ULL); | |
467 | wsize = size + (offset - woffset); | |
468 | wsize = PAGE_ALIGN(wsize); | |
469 | ||
470 | if (wsize < WINDOW_SIZE) { | |
471 | uint64_t delta; | |
472 | ||
473 | delta = PAGE_ALIGN((WINDOW_SIZE - wsize) / 2); | |
474 | ||
475 | if (delta > offset) | |
476 | woffset = 0; | |
477 | else | |
478 | woffset -= delta; | |
479 | ||
480 | wsize = WINDOW_SIZE; | |
481 | } | |
482 | ||
483 | if (st) { | |
484 | /* Memory maps that are larger then the files | |
485 | underneath have undefined behavior. Hence, clamp | |
486 | things to the file size if we know it */ | |
487 | ||
488 | if (woffset >= (uint64_t) st->st_size) | |
489 | return -EADDRNOTAVAIL; | |
490 | ||
491 | if (woffset + wsize > (uint64_t) st->st_size) | |
492 | wsize = PAGE_ALIGN(st->st_size - woffset); | |
493 | } | |
494 | ||
495 | for (;;) { | |
496 | d = mmap(NULL, wsize, prot, MAP_SHARED, fd, woffset); | |
497 | if (d != MAP_FAILED) | |
498 | break; | |
499 | if (errno != ENOMEM) | |
500 | return -errno; | |
501 | ||
502 | r = make_room(m); | |
503 | if (r < 0) | |
504 | return r; | |
505 | if (r == 0) | |
506 | return -ENOMEM; | |
507 | } | |
508 | ||
509 | c = context_add(m, context); | |
510 | if (!c) | |
511 | goto outofmem; | |
512 | ||
513 | f = fd_add(m, fd); | |
514 | if (!f) | |
515 | goto outofmem; | |
516 | ||
517 | w = window_add(m); | |
518 | if (!w) | |
519 | goto outofmem; | |
520 | ||
521 | w->keep_always = keep_always; | |
522 | w->ptr = d; | |
523 | w->offset = woffset; | |
524 | w->prot = prot; | |
525 | w->size = wsize; | |
526 | w->fd = f; | |
527 | ||
528 | LIST_PREPEND(by_fd, f->windows, w); | |
529 | ||
530 | context_detach_window(c); | |
531 | c->window = w; | |
532 | LIST_PREPEND(by_window, w->contexts, c); | |
533 | ||
534 | *ret = (uint8_t*) w->ptr + (offset - w->offset); | |
535 | return 1; | |
536 | ||
537 | outofmem: | |
538 | munmap(d, wsize); | |
539 | return -ENOMEM; | |
540 | } | |
541 | ||
542 | int mmap_cache_get( | |
543 | MMapCache *m, | |
544 | int fd, | |
545 | int prot, | |
546 | unsigned context, | |
547 | bool keep_always, | |
548 | uint64_t offset, | |
549 | size_t size, | |
550 | struct stat *st, | |
551 | void **ret) { | |
552 | ||
553 | int r; | |
554 | ||
555 | assert(m); | |
556 | assert(m->n_ref > 0); | |
557 | assert(fd >= 0); | |
558 | assert(size > 0); | |
559 | assert(ret); | |
560 | ||
561 | /* Check whether the current context is the right one already */ | |
562 | r = try_context(m, fd, prot, context, keep_always, offset, size, ret); | |
563 | if (r != 0) { | |
564 | m->n_hit ++; | |
565 | return r; | |
566 | } | |
567 | ||
568 | /* Search for a matching mmap */ | |
569 | r = find_mmap(m, fd, prot, context, keep_always, offset, size, ret); | |
570 | if (r != 0) { | |
571 | m->n_hit ++; | |
572 | return r; | |
573 | } | |
574 | ||
575 | m->n_missed++; | |
576 | ||
577 | /* Create a new mmap */ | |
578 | return add_mmap(m, fd, prot, context, keep_always, offset, size, st, ret); | |
579 | } | |
580 | ||
581 | void mmap_cache_close_fd(MMapCache *m, int fd) { | |
582 | FileDescriptor *f; | |
583 | ||
584 | assert(m); | |
585 | assert(fd >= 0); | |
586 | ||
587 | f = hashmap_get(m->fds, INT_TO_PTR(fd + 1)); | |
588 | if (!f) | |
589 | return; | |
590 | ||
591 | fd_free(f); | |
592 | } | |
593 | ||
594 | void mmap_cache_close_context(MMapCache *m, unsigned context) { | |
595 | Context *c; | |
596 | ||
597 | assert(m); | |
598 | ||
599 | c = hashmap_get(m->contexts, UINT_TO_PTR(context + 1)); | |
600 | if (!c) | |
601 | return; | |
602 | ||
603 | context_free(c); | |
604 | } | |
605 | ||
606 | unsigned mmap_cache_get_hit(MMapCache *m) { | |
607 | assert(m); | |
608 | ||
609 | return m->n_hit; | |
610 | } | |
611 | ||
612 | unsigned mmap_cache_get_missed(MMapCache *m) { | |
613 | assert(m); | |
614 | ||
615 | return m->n_missed; | |
616 | } |