1 | /* Malloc implementation for multiple threads without lock contention. |
2 | Copyright (C) 2001-2020 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Wolfram Gloger <wg@malloc.de>, 2001. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public License as |
8 | published by the Free Software Foundation; either version 2.1 of the |
9 | License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; see the file COPYING.LIB. If |
18 | not, see <https://www.gnu.org/licenses/>. */ |
19 | |
20 | /* What to do if the standard debugging hooks are in place and a |
21 | corrupt pointer is detected: do nothing (0), print an error message |
22 | (1), or call abort() (2). */ |
23 | |
24 | /* Hooks for debugging versions. The initial hooks just call the |
25 | initialization routine, then do the normal work. */ |
26 | |
27 | static void * |
28 | malloc_hook_ini (size_t sz, const void *caller) |
29 | { |
30 | __malloc_hook = NULL; |
31 | ptmalloc_init (); |
32 | return __libc_malloc (sz); |
33 | } |
34 | |
35 | static void * |
36 | realloc_hook_ini (void *ptr, size_t sz, const void *caller) |
37 | { |
38 | __malloc_hook = NULL; |
39 | __realloc_hook = NULL; |
40 | ptmalloc_init (); |
41 | return __libc_realloc (ptr, sz); |
42 | } |
43 | |
44 | static void * |
45 | memalign_hook_ini (size_t alignment, size_t sz, const void *caller) |
46 | { |
47 | __memalign_hook = NULL; |
48 | ptmalloc_init (); |
49 | return __libc_memalign (alignment, sz); |
50 | } |
51 | |
52 | /* Whether we are using malloc checking. */ |
53 | static int using_malloc_checking; |
54 | |
55 | /* Activate a standard set of debugging hooks. */ |
56 | void |
57 | __malloc_check_init (void) |
58 | { |
59 | using_malloc_checking = 1; |
60 | __malloc_hook = malloc_check; |
61 | __free_hook = free_check; |
62 | __realloc_hook = realloc_check; |
63 | __memalign_hook = memalign_check; |
64 | } |
65 | |
66 | /* A simple, standard set of debugging hooks. Overhead is `only' one |
67 | byte per chunk; still this will catch most cases of double frees or |
68 | overruns. The goal here is to avoid obscure crashes due to invalid |
69 | usage, unlike in the MALLOC_DEBUG code. */ |
70 | |
71 | static unsigned char |
72 | magicbyte (const void *p) |
73 | { |
74 | unsigned char magic; |
75 | |
76 | magic = (((uintptr_t) p >> 3) ^ ((uintptr_t) p >> 11)) & 0xFF; |
77 | /* Do not return 1. See the comment in mem2mem_check(). */ |
78 | if (magic == 1) |
79 | ++magic; |
80 | return magic; |
81 | } |
82 | |
83 | |
84 | /* Visualize the chunk as being partitioned into blocks of 255 bytes from the |
85 | highest address of the chunk, downwards. The end of each block tells |
86 | us the size of that block, up to the actual size of the requested |
87 | memory. Our magic byte is right at the end of the requested size, so we |
88 | must reach it with this iteration, otherwise we have witnessed a memory |
89 | corruption. */ |
90 | static size_t |
91 | malloc_check_get_size (mchunkptr p) |
92 | { |
93 | size_t size; |
94 | unsigned char c; |
95 | unsigned char magic = magicbyte (p); |
96 | |
97 | assert (using_malloc_checking == 1); |
98 | |
99 | for (size = chunksize (p) - 1 + (chunk_is_mmapped (p) ? 0 : SIZE_SZ); |
100 | (c = ((unsigned char *) p)[size]) != magic; |
101 | size -= c) |
102 | { |
103 | if (c <= 0 || size < (c + 2 * SIZE_SZ)) |
104 | malloc_printerr ("malloc_check_get_size: memory corruption" ); |
105 | } |
106 | |
107 | /* chunk2mem size. */ |
108 | return size - 2 * SIZE_SZ; |
109 | } |
110 | |
111 | /* Instrument a chunk with overrun detector byte(s) and convert it |
112 | into a user pointer with requested size req_sz. */ |
113 | |
114 | static void * |
115 | mem2mem_check (void *ptr, size_t req_sz) |
116 | { |
117 | mchunkptr p; |
118 | unsigned char *m_ptr = ptr; |
119 | size_t max_sz, block_sz, i; |
120 | unsigned char magic; |
121 | |
122 | if (!ptr) |
123 | return ptr; |
124 | |
125 | p = mem2chunk (ptr); |
126 | magic = magicbyte (p); |
127 | max_sz = chunksize (p) - 2 * SIZE_SZ; |
128 | if (!chunk_is_mmapped (p)) |
129 | max_sz += SIZE_SZ; |
130 | for (i = max_sz - 1; i > req_sz; i -= block_sz) |
131 | { |
132 | block_sz = MIN (i - req_sz, 0xff); |
133 | /* Don't allow the magic byte to appear in the chain of length bytes. |
134 | For the following to work, magicbyte cannot return 0x01. */ |
135 | if (block_sz == magic) |
136 | --block_sz; |
137 | |
138 | m_ptr[i] = block_sz; |
139 | } |
140 | m_ptr[req_sz] = magic; |
141 | return (void *) m_ptr; |
142 | } |
143 | |
144 | /* Convert a pointer to be free()d or realloc()ed to a valid chunk |
145 | pointer. If the provided pointer is not valid, return NULL. */ |
146 | |
147 | static mchunkptr |
148 | mem2chunk_check (void *mem, unsigned char **magic_p) |
149 | { |
150 | mchunkptr p; |
151 | INTERNAL_SIZE_T sz, c; |
152 | unsigned char magic; |
153 | |
154 | if (!aligned_OK (mem)) |
155 | return NULL; |
156 | |
157 | p = mem2chunk (mem); |
158 | sz = chunksize (p); |
159 | magic = magicbyte (p); |
160 | if (!chunk_is_mmapped (p)) |
161 | { |
162 | /* Must be a chunk in conventional heap memory. */ |
163 | int contig = contiguous (&main_arena); |
164 | if ((contig && |
165 | ((char *) p < mp_.sbrk_base || |
166 | ((char *) p + sz) >= (mp_.sbrk_base + main_arena.system_mem))) || |
167 | sz < MINSIZE || sz & MALLOC_ALIGN_MASK || !inuse (p) || |
168 | (!prev_inuse (p) && ((prev_size (p) & MALLOC_ALIGN_MASK) != 0 || |
169 | (contig && (char *) prev_chunk (p) < mp_.sbrk_base) || |
170 | next_chunk (prev_chunk (p)) != p))) |
171 | return NULL; |
172 | |
173 | for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) |
174 | { |
175 | if (c == 0 || sz < (c + 2 * SIZE_SZ)) |
176 | return NULL; |
177 | } |
178 | } |
179 | else |
180 | { |
181 | unsigned long offset, page_mask = GLRO (dl_pagesize) - 1; |
182 | |
183 | /* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two |
184 | alignment relative to the beginning of a page. Check this |
185 | first. */ |
186 | offset = (unsigned long) mem & page_mask; |
187 | if ((offset != MALLOC_ALIGNMENT && offset != 0 && offset != 0x10 && |
188 | offset != 0x20 && offset != 0x40 && offset != 0x80 && offset != 0x100 && |
189 | offset != 0x200 && offset != 0x400 && offset != 0x800 && offset != 0x1000 && |
190 | offset < 0x2000) || |
191 | !chunk_is_mmapped (p) || prev_inuse (p) || |
192 | ((((unsigned long) p - prev_size (p)) & page_mask) != 0) || |
193 | ((prev_size (p) + sz) & page_mask) != 0) |
194 | return NULL; |
195 | |
196 | for (sz -= 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) |
197 | { |
198 | if (c == 0 || sz < (c + 2 * SIZE_SZ)) |
199 | return NULL; |
200 | } |
201 | } |
202 | ((unsigned char *) p)[sz] ^= 0xFF; |
203 | if (magic_p) |
204 | *magic_p = (unsigned char *) p + sz; |
205 | return p; |
206 | } |
207 | |
208 | /* Check for corruption of the top chunk. */ |
209 | static void |
210 | top_check (void) |
211 | { |
212 | mchunkptr t = top (&main_arena); |
213 | |
214 | if (t == initial_top (&main_arena) || |
215 | (!chunk_is_mmapped (t) && |
216 | chunksize (t) >= MINSIZE && |
217 | prev_inuse (t) && |
218 | (!contiguous (&main_arena) || |
219 | (char *) t + chunksize (t) == mp_.sbrk_base + main_arena.system_mem))) |
220 | return; |
221 | |
222 | malloc_printerr ("malloc: top chunk is corrupt" ); |
223 | } |
224 | |
225 | static void * |
226 | malloc_check (size_t sz, const void *caller) |
227 | { |
228 | void *victim; |
229 | size_t nb; |
230 | |
231 | if (__builtin_add_overflow (sz, 1, &nb)) |
232 | { |
233 | __set_errno (ENOMEM); |
234 | return NULL; |
235 | } |
236 | |
237 | __libc_lock_lock (main_arena.mutex); |
238 | top_check (); |
239 | victim = _int_malloc (&main_arena, nb); |
240 | __libc_lock_unlock (main_arena.mutex); |
241 | return mem2mem_check (victim, sz); |
242 | } |
243 | |
244 | static void |
245 | free_check (void *mem, const void *caller) |
246 | { |
247 | mchunkptr p; |
248 | |
249 | if (!mem) |
250 | return; |
251 | |
252 | __libc_lock_lock (main_arena.mutex); |
253 | p = mem2chunk_check (mem, NULL); |
254 | if (!p) |
255 | malloc_printerr ("free(): invalid pointer" ); |
256 | if (chunk_is_mmapped (p)) |
257 | { |
258 | __libc_lock_unlock (main_arena.mutex); |
259 | munmap_chunk (p); |
260 | return; |
261 | } |
262 | _int_free (&main_arena, p, 1); |
263 | __libc_lock_unlock (main_arena.mutex); |
264 | } |
265 | |
266 | static void * |
267 | realloc_check (void *oldmem, size_t bytes, const void *caller) |
268 | { |
269 | INTERNAL_SIZE_T nb; |
270 | void *newmem = 0; |
271 | unsigned char *magic_p; |
272 | size_t rb; |
273 | |
274 | if (__builtin_add_overflow (bytes, 1, &rb)) |
275 | { |
276 | __set_errno (ENOMEM); |
277 | return NULL; |
278 | } |
279 | if (oldmem == 0) |
280 | return malloc_check (bytes, NULL); |
281 | |
282 | if (bytes == 0) |
283 | { |
284 | free_check (oldmem, NULL); |
285 | return NULL; |
286 | } |
287 | __libc_lock_lock (main_arena.mutex); |
288 | const mchunkptr oldp = mem2chunk_check (oldmem, &magic_p); |
289 | __libc_lock_unlock (main_arena.mutex); |
290 | if (!oldp) |
291 | malloc_printerr ("realloc(): invalid pointer" ); |
292 | const INTERNAL_SIZE_T oldsize = chunksize (oldp); |
293 | |
294 | if (!checked_request2size (rb, &nb)) |
295 | goto invert; |
296 | |
297 | __libc_lock_lock (main_arena.mutex); |
298 | |
299 | if (chunk_is_mmapped (oldp)) |
300 | { |
301 | #if HAVE_MREMAP |
302 | mchunkptr newp = mremap_chunk (oldp, nb); |
303 | if (newp) |
304 | newmem = chunk2mem (newp); |
305 | else |
306 | #endif |
307 | { |
308 | /* Note the extra SIZE_SZ overhead. */ |
309 | if (oldsize - SIZE_SZ >= nb) |
310 | newmem = oldmem; /* do nothing */ |
311 | else |
312 | { |
313 | /* Must alloc, copy, free. */ |
314 | top_check (); |
315 | newmem = _int_malloc (&main_arena, rb); |
316 | if (newmem) |
317 | { |
318 | memcpy (newmem, oldmem, oldsize - 2 * SIZE_SZ); |
319 | munmap_chunk (oldp); |
320 | } |
321 | } |
322 | } |
323 | } |
324 | else |
325 | { |
326 | top_check (); |
327 | newmem = _int_realloc (&main_arena, oldp, oldsize, nb); |
328 | } |
329 | |
330 | DIAG_PUSH_NEEDS_COMMENT; |
331 | #if __GNUC_PREREQ (7, 0) |
332 | /* GCC 7 warns about magic_p may be used uninitialized. But we never |
333 | reach here if magic_p is uninitialized. */ |
334 | DIAG_IGNORE_NEEDS_COMMENT (7, "-Wmaybe-uninitialized" ); |
335 | #endif |
336 | /* mem2chunk_check changed the magic byte in the old chunk. |
337 | If newmem is NULL, then the old chunk will still be used though, |
338 | so we need to invert that change here. */ |
339 | invert: |
340 | if (newmem == NULL) |
341 | *magic_p ^= 0xFF; |
342 | DIAG_POP_NEEDS_COMMENT; |
343 | |
344 | __libc_lock_unlock (main_arena.mutex); |
345 | |
346 | return mem2mem_check (newmem, bytes); |
347 | } |
348 | |
349 | static void * |
350 | memalign_check (size_t alignment, size_t bytes, const void *caller) |
351 | { |
352 | void *mem; |
353 | |
354 | if (alignment <= MALLOC_ALIGNMENT) |
355 | return malloc_check (bytes, NULL); |
356 | |
357 | if (alignment < MINSIZE) |
358 | alignment = MINSIZE; |
359 | |
360 | /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a |
361 | power of 2 and will cause overflow in the check below. */ |
362 | if (alignment > SIZE_MAX / 2 + 1) |
363 | { |
364 | __set_errno (EINVAL); |
365 | return 0; |
366 | } |
367 | |
368 | /* Check for overflow. */ |
369 | if (bytes > SIZE_MAX - alignment - MINSIZE) |
370 | { |
371 | __set_errno (ENOMEM); |
372 | return 0; |
373 | } |
374 | |
375 | /* Make sure alignment is power of 2. */ |
376 | if (!powerof2 (alignment)) |
377 | { |
378 | size_t a = MALLOC_ALIGNMENT * 2; |
379 | while (a < alignment) |
380 | a <<= 1; |
381 | alignment = a; |
382 | } |
383 | |
384 | __libc_lock_lock (main_arena.mutex); |
385 | top_check (); |
386 | mem = _int_memalign (&main_arena, alignment, bytes + 1); |
387 | __libc_lock_unlock (main_arena.mutex); |
388 | return mem2mem_check (mem, bytes); |
389 | } |
390 | |
391 | #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_25) |
392 | |
393 | /* Support for restoring dumped heaps contained in historic Emacs |
394 | executables. The heap saving feature (malloc_get_state) is no |
395 | longer implemented in this version of glibc, but we have a heap |
396 | rewriter in malloc_set_state which transforms the heap into a |
397 | version compatible with current malloc. */ |
398 | |
399 | #define MALLOC_STATE_MAGIC 0x444c4541l |
400 | #define MALLOC_STATE_VERSION (0 * 0x100l + 5l) /* major*0x100 + minor */ |
401 | |
402 | struct malloc_save_state |
403 | { |
404 | long magic; |
405 | long version; |
406 | mbinptr av[NBINS * 2 + 2]; |
407 | char *sbrk_base; |
408 | int sbrked_mem_bytes; |
409 | unsigned long trim_threshold; |
410 | unsigned long top_pad; |
411 | unsigned int n_mmaps_max; |
412 | unsigned long mmap_threshold; |
413 | int check_action; |
414 | unsigned long max_sbrked_mem; |
415 | unsigned long max_total_mem; /* Always 0, for backwards compatibility. */ |
416 | unsigned int n_mmaps; |
417 | unsigned int max_n_mmaps; |
418 | unsigned long mmapped_mem; |
419 | unsigned long max_mmapped_mem; |
420 | int using_malloc_checking; |
421 | unsigned long max_fast; |
422 | unsigned long arena_test; |
423 | unsigned long arena_max; |
424 | unsigned long narenas; |
425 | }; |
426 | |
427 | /* Dummy implementation which always fails. We need to provide this |
428 | symbol so that existing Emacs binaries continue to work with |
429 | BIND_NOW. */ |
430 | void * |
431 | attribute_compat_text_section |
432 | malloc_get_state (void) |
433 | { |
434 | __set_errno (ENOSYS); |
435 | return NULL; |
436 | } |
437 | compat_symbol (libc, malloc_get_state, malloc_get_state, GLIBC_2_0); |
438 | |
439 | int |
440 | attribute_compat_text_section |
441 | malloc_set_state (void *msptr) |
442 | { |
443 | struct malloc_save_state *ms = (struct malloc_save_state *) msptr; |
444 | |
445 | if (ms->magic != MALLOC_STATE_MAGIC) |
446 | return -1; |
447 | |
448 | /* Must fail if the major version is too high. */ |
449 | if ((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) |
450 | return -2; |
451 | |
452 | /* We do not need to perform locking here because malloc_set_state |
453 | must be called before the first call into the malloc subsytem |
454 | (usually via __malloc_initialize_hook). pthread_create always |
455 | calls calloc and thus must be called only afterwards, so there |
456 | cannot be more than one thread when we reach this point. */ |
457 | |
458 | /* Disable the malloc hooks (and malloc checking). */ |
459 | __malloc_hook = NULL; |
460 | __realloc_hook = NULL; |
461 | __free_hook = NULL; |
462 | __memalign_hook = NULL; |
463 | using_malloc_checking = 0; |
464 | |
465 | /* Patch the dumped heap. We no longer try to integrate into the |
466 | existing heap. Instead, we mark the existing chunks as mmapped. |
467 | Together with the update to dumped_main_arena_start and |
468 | dumped_main_arena_end, realloc and free will recognize these |
469 | chunks as dumped fake mmapped chunks and never free them. */ |
470 | |
471 | /* Find the chunk with the lowest address with the heap. */ |
472 | mchunkptr chunk = NULL; |
473 | { |
474 | size_t *candidate = (size_t *) ms->sbrk_base; |
475 | size_t *end = (size_t *) (ms->sbrk_base + ms->sbrked_mem_bytes); |
476 | while (candidate < end) |
477 | if (*candidate != 0) |
478 | { |
479 | chunk = mem2chunk ((void *) (candidate + 1)); |
480 | break; |
481 | } |
482 | else |
483 | ++candidate; |
484 | } |
485 | if (chunk == NULL) |
486 | return 0; |
487 | |
488 | /* Iterate over the dumped heap and patch the chunks so that they |
489 | are treated as fake mmapped chunks. */ |
490 | mchunkptr top = ms->av[2]; |
491 | while (chunk < top) |
492 | { |
493 | if (inuse (chunk)) |
494 | { |
495 | /* Mark chunk as mmapped, to trigger the fallback path. */ |
496 | size_t size = chunksize (chunk); |
497 | set_head (chunk, size | IS_MMAPPED); |
498 | } |
499 | chunk = next_chunk (chunk); |
500 | } |
501 | |
502 | /* The dumped fake mmapped chunks all lie in this address range. */ |
503 | dumped_main_arena_start = (mchunkptr) ms->sbrk_base; |
504 | dumped_main_arena_end = top; |
505 | |
506 | return 0; |
507 | } |
508 | compat_symbol (libc, malloc_set_state, malloc_set_state, GLIBC_2_0); |
509 | |
510 | #endif /* SHLIB_COMPAT */ |
511 | |
512 | /* |
513 | * Local variables: |
514 | * c-basic-offset: 2 |
515 | * End: |
516 | */ |
517 | |