1 /*
2  * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <errno.h>
18 #include <stdlib.h>
19 #include <stdint.h>
20 #include <string.h>
21 #include <unistd.h>
22 
23 /*
24  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
25  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
26  */
27 #define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
28 
29 /*
30  * Even though specified in POSIX, the PAGESIZE and PAGE_SIZE
31  * macros have very poor portability.  Since we only use this
32  * to avoid free() overhead for small shrinking, simply pick
33  * an arbitrary number.
34  */
35 #define getpagesize()	(1UL << 12)
36 
37 /* cheat: provide a prototype for explicit_bzero: if libc doesn't
38  * provide it, we will link to compat/explicit_bzero.c anyway. */
39 void explicit_bzero(void*, size_t);
40 
41 void *
42 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
43 {
44 	size_t oldsize, newsize;
45 	void *newptr;
46 
47 	if (ptr == NULL)
48 		return calloc(newnmemb, size);
49 
50 	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
51 	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
52 		errno = ENOMEM;
53 		return NULL;
54 	}
55 	newsize = newnmemb * size;
56 
57 	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
58 	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
59 		errno = EINVAL;
60 		return NULL;
61 	}
62 	oldsize = oldnmemb * size;
63 
64 	/*
65 	 * Don't bother too much if we're shrinking just a bit,
66 	 * we do not shrink for series of small steps, oh well.
67 	 */
68 	if (newsize <= oldsize) {
69 		size_t d = oldsize - newsize;
70 
71 		if (d < oldsize / 2 && d < getpagesize()) {
72 			memset((char *)ptr + newsize, 0, d);
73 			return ptr;
74 		}
75 	}
76 
77 	newptr = malloc(newsize);
78 	if (newptr == NULL)
79 		return NULL;
80 
81 	if (newsize > oldsize) {
82 		memcpy(newptr, ptr, oldsize);
83 		memset((char *)newptr + oldsize, 0, newsize - oldsize);
84 	} else
85 		memcpy(newptr, ptr, newsize);
86 
87 	explicit_bzero(ptr, oldsize);
88 	free(ptr);
89 
90 	return newptr;
91 }