1 /* Malloc implementation for multiple threads without lock contention.
2 Copyright (C) 2001-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Wolfram Gloger <wg@malloc.de>, 2001.
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.
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.
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 <http://www.gnu.org/licenses/>. */
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). */
24 /* Hooks for debugging versions. The initial hooks just call the
25 initialization routine, then do the normal work. */
28 malloc_hook_ini (size_t sz
, const void *caller
)
32 return __libc_malloc (sz
);
36 realloc_hook_ini (void *ptr
, size_t sz
, const void *caller
)
39 __realloc_hook
= NULL
;
41 return __libc_realloc (ptr
, sz
);
45 memalign_hook_ini (size_t alignment
, size_t sz
, const void *caller
)
47 __memalign_hook
= NULL
;
49 return __libc_memalign (alignment
, sz
);
52 /* Whether we are using malloc checking. */
53 static int using_malloc_checking
;
55 /* Activate a standard set of debugging hooks. */
57 __malloc_check_init (void)
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
;
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. */
72 magicbyte (const void *p
)
76 magic
= (((uintptr_t) p
>> 3) ^ ((uintptr_t) p
>> 11)) & 0xFF;
77 /* Do not return 1. See the comment in mem2mem_check(). */
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
91 malloc_check_get_size (mchunkptr p
)
95 unsigned char magic
= magicbyte (p
);
97 assert (using_malloc_checking
== 1);
99 for (size
= chunksize (p
) - 1 + (chunk_is_mmapped (p
) ? 0 : SIZE_SZ
);
100 (c
= ((unsigned char *) p
)[size
]) != magic
;
103 if (c
<= 0 || size
< (c
+ 2 * SIZE_SZ
))
104 malloc_printerr ("malloc_check_get_size: memory corruption");
107 /* chunk2mem size. */
108 return size
- 2 * SIZE_SZ
;
111 /* Instrument a chunk with overrun detector byte(s) and convert it
112 into a user pointer with requested size req_sz. */
115 mem2mem_check (void *ptr
, size_t req_sz
)
118 unsigned char *m_ptr
= ptr
;
119 size_t max_sz
, block_sz
, i
;
126 magic
= magicbyte (p
);
127 max_sz
= chunksize (p
) - 2 * SIZE_SZ
;
128 if (!chunk_is_mmapped (p
))
130 for (i
= max_sz
- 1; i
> req_sz
; i
-= block_sz
)
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
)
140 m_ptr
[req_sz
] = magic
;
141 return (void *) m_ptr
;
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. */
148 mem2chunk_check (void *mem
, unsigned char **magic_p
)
151 INTERNAL_SIZE_T sz
, c
;
154 if (!aligned_OK (mem
))
159 magic
= magicbyte (p
);
160 if (!chunk_is_mmapped (p
))
162 /* Must be a chunk in conventional heap memory. */
163 int contig
= contiguous (&main_arena
);
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
)))
173 for (sz
+= SIZE_SZ
- 1; (c
= ((unsigned char *) p
)[sz
]) != magic
; sz
-= c
)
175 if (c
== 0 || sz
< (c
+ 2 * SIZE_SZ
))
181 unsigned long offset
, page_mask
= GLRO (dl_pagesize
) - 1;
183 /* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two
184 alignment relative to the beginning of a page. Check this
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 &&
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)
196 for (sz
-= 1; (c
= ((unsigned char *) p
)[sz
]) != magic
; sz
-= c
)
198 if (c
== 0 || sz
< (c
+ 2 * SIZE_SZ
))
202 ((unsigned char *) p
)[sz
] ^= 0xFF;
204 *magic_p
= (unsigned char *) p
+ sz
;
208 /* Check for corruption of the top chunk. */
212 mchunkptr t
= top (&main_arena
);
214 if (t
== initial_top (&main_arena
) ||
215 (!chunk_is_mmapped (t
) &&
216 chunksize (t
) >= MINSIZE
&&
218 (!contiguous (&main_arena
) ||
219 (char *) t
+ chunksize (t
) == mp_
.sbrk_base
+ main_arena
.system_mem
)))
222 malloc_printerr ("malloc: top chunk is corrupt");
226 malloc_check (size_t sz
, const void *caller
)
232 __set_errno (ENOMEM
);
236 __libc_lock_lock (main_arena
.mutex
);
238 victim
= _int_malloc (&main_arena
, sz
+ 1);
239 __libc_lock_unlock (main_arena
.mutex
);
240 return mem2mem_check (victim
, sz
);
244 free_check (void *mem
, const void *caller
)
251 __libc_lock_lock (main_arena
.mutex
);
252 p
= mem2chunk_check (mem
, NULL
);
254 malloc_printerr ("free(): invalid pointer");
255 if (chunk_is_mmapped (p
))
257 __libc_lock_unlock (main_arena
.mutex
);
261 _int_free (&main_arena
, p
, 1);
262 __libc_lock_unlock (main_arena
.mutex
);
266 realloc_check (void *oldmem
, size_t bytes
, const void *caller
)
270 unsigned char *magic_p
;
274 __set_errno (ENOMEM
);
278 return malloc_check (bytes
, NULL
);
282 free_check (oldmem
, NULL
);
285 __libc_lock_lock (main_arena
.mutex
);
286 const mchunkptr oldp
= mem2chunk_check (oldmem
, &magic_p
);
287 __libc_lock_unlock (main_arena
.mutex
);
289 malloc_printerr ("realloc(): invalid pointer");
290 const INTERNAL_SIZE_T oldsize
= chunksize (oldp
);
292 checked_request2size (bytes
+ 1, nb
);
293 __libc_lock_lock (main_arena
.mutex
);
295 if (chunk_is_mmapped (oldp
))
298 mchunkptr newp
= mremap_chunk (oldp
, nb
);
300 newmem
= chunk2mem (newp
);
304 /* Note the extra SIZE_SZ overhead. */
305 if (oldsize
- SIZE_SZ
>= nb
)
306 newmem
= oldmem
; /* do nothing */
309 /* Must alloc, copy, free. */
311 newmem
= _int_malloc (&main_arena
, bytes
+ 1);
314 memcpy (newmem
, oldmem
, oldsize
- 2 * SIZE_SZ
);
324 checked_request2size (bytes
+ 1, nb
);
325 newmem
= _int_realloc (&main_arena
, oldp
, oldsize
, nb
);
328 DIAG_PUSH_NEEDS_COMMENT
;
329 #if __GNUC_PREREQ (7, 0)
330 /* GCC 7 warns about magic_p may be used uninitialized. But we never
331 reach here if magic_p is uninitialized. */
332 DIAG_IGNORE_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
334 /* mem2chunk_check changed the magic byte in the old chunk.
335 If newmem is NULL, then the old chunk will still be used though,
336 so we need to invert that change here. */
339 DIAG_POP_NEEDS_COMMENT
;
341 __libc_lock_unlock (main_arena
.mutex
);
343 return mem2mem_check (newmem
, bytes
);
347 memalign_check (size_t alignment
, size_t bytes
, const void *caller
)
351 if (alignment
<= MALLOC_ALIGNMENT
)
352 return malloc_check (bytes
, NULL
);
354 if (alignment
< MINSIZE
)
357 /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
358 power of 2 and will cause overflow in the check below. */
359 if (alignment
> SIZE_MAX
/ 2 + 1)
361 __set_errno (EINVAL
);
365 /* Check for overflow. */
366 if (bytes
> SIZE_MAX
- alignment
- MINSIZE
)
368 __set_errno (ENOMEM
);
372 /* Make sure alignment is power of 2. */
373 if (!powerof2 (alignment
))
375 size_t a
= MALLOC_ALIGNMENT
* 2;
376 while (a
< alignment
)
381 __libc_lock_lock (main_arena
.mutex
);
383 mem
= _int_memalign (&main_arena
, alignment
, bytes
+ 1);
384 __libc_lock_unlock (main_arena
.mutex
);
385 return mem2mem_check (mem
, bytes
);
388 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_25)
390 /* Support for restoring dumped heaps contained in historic Emacs
391 executables. The heap saving feature (malloc_get_state) is no
392 longer implemented in this version of glibc, but we have a heap
393 rewriter in malloc_set_state which transforms the heap into a
394 version compatible with current malloc. */
396 #define MALLOC_STATE_MAGIC 0x444c4541l
397 #define MALLOC_STATE_VERSION (0 * 0x100l + 5l) /* major*0x100 + minor */
399 struct malloc_save_state
403 mbinptr av
[NBINS
* 2 + 2];
405 int sbrked_mem_bytes
;
406 unsigned long trim_threshold
;
407 unsigned long top_pad
;
408 unsigned int n_mmaps_max
;
409 unsigned long mmap_threshold
;
411 unsigned long max_sbrked_mem
;
412 unsigned long max_total_mem
; /* Always 0, for backwards compatibility. */
413 unsigned int n_mmaps
;
414 unsigned int max_n_mmaps
;
415 unsigned long mmapped_mem
;
416 unsigned long max_mmapped_mem
;
417 int using_malloc_checking
;
418 unsigned long max_fast
;
419 unsigned long arena_test
;
420 unsigned long arena_max
;
421 unsigned long narenas
;
424 /* Dummy implementation which always fails. We need to provide this
425 symbol so that existing Emacs binaries continue to work with
428 attribute_compat_text_section
429 malloc_get_state (void)
431 __set_errno (ENOSYS
);
434 compat_symbol (libc
, malloc_get_state
, malloc_get_state
, GLIBC_2_0
);
437 attribute_compat_text_section
438 malloc_set_state (void *msptr
)
440 struct malloc_save_state
*ms
= (struct malloc_save_state
*) msptr
;
442 if (ms
->magic
!= MALLOC_STATE_MAGIC
)
445 /* Must fail if the major version is too high. */
446 if ((ms
->version
& ~0xffl
) > (MALLOC_STATE_VERSION
& ~0xffl
))
449 /* We do not need to perform locking here because malloc_set_state
450 must be called before the first call into the malloc subsytem
451 (usually via __malloc_initialize_hook). pthread_create always
452 calls calloc and thus must be called only afterwards, so there
453 cannot be more than one thread when we reach this point. */
455 /* Disable the malloc hooks (and malloc checking). */
456 __malloc_hook
= NULL
;
457 __realloc_hook
= NULL
;
459 __memalign_hook
= NULL
;
460 using_malloc_checking
= 0;
462 /* Patch the dumped heap. We no longer try to integrate into the
463 existing heap. Instead, we mark the existing chunks as mmapped.
464 Together with the update to dumped_main_arena_start and
465 dumped_main_arena_end, realloc and free will recognize these
466 chunks as dumped fake mmapped chunks and never free them. */
468 /* Find the chunk with the lowest address with the heap. */
469 mchunkptr chunk
= NULL
;
471 size_t *candidate
= (size_t *) ms
->sbrk_base
;
472 size_t *end
= (size_t *) (ms
->sbrk_base
+ ms
->sbrked_mem_bytes
);
473 while (candidate
< end
)
476 chunk
= mem2chunk ((void *) (candidate
+ 1));
485 /* Iterate over the dumped heap and patch the chunks so that they
486 are treated as fake mmapped chunks. */
487 mchunkptr top
= ms
->av
[2];
492 /* Mark chunk as mmapped, to trigger the fallback path. */
493 size_t size
= chunksize (chunk
);
494 set_head (chunk
, size
| IS_MMAPPED
);
496 chunk
= next_chunk (chunk
);
499 /* The dumped fake mmapped chunks all lie in this address range. */
500 dumped_main_arena_start
= (mchunkptr
) ms
->sbrk_base
;
501 dumped_main_arena_end
= top
;
505 compat_symbol (libc
, malloc_set_state
, malloc_set_state
, GLIBC_2_0
);
507 #endif /* SHLIB_COMPAT */