1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
/*
* Copyright (c) 2012, 2013 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the company may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#define _GNU_SOURCE
#include "local-malloc.h"
/*
* Allocate memory block aligned at specific boundary.
* align: required alignment. Must be power of 2. Return NULL
* if not power of 2. Undefined behavior is bigger than
* pointer value range.
* s: required size.
* Return: allocated memory pointer aligned to align
* Algorithm: Malloc a big enough block, padding pointer to aligned
* address, then truncate and free the tail if too big.
* Record the offset of align pointer and original pointer
* in the padding area.
*/
void *
memalign(size_t align, size_t s)
{
chunk_t *chunk_p;
size_t offset, size_with_padding;
char *allocated, *aligned_p;
/* Return NULL if align isn't power of 2 */
if ((align & (align - 1)) != 0) {
errno = EINVAL;
return NULL;
}
align = MAX(align, MALLOC_MINSIZE);
if (s > MALLOC_MAXSIZE - align) {
errno = ENOMEM;
return NULL;
}
s = __align_up(MAX(s, 1), MALLOC_CHUNK_ALIGN);
/* Make sure there's space to align the allocation and split
* off chunk_t from the front
*/
size_with_padding = s + align + MALLOC_MINSIZE;
allocated = __malloc_malloc(size_with_padding);
if (allocated == NULL)
return NULL;
chunk_p = ptr_to_chunk(allocated);
aligned_p = __align_up(allocated, align);
offset = (size_t)(aligned_p - allocated);
/* Split off the front piece if necessary */
if (offset) {
if (offset < MALLOC_MINSIZE) {
aligned_p += align;
offset += align;
}
chunk_t *new_chunk_p = ptr_to_chunk(aligned_p);
_set_size(new_chunk_p, _size(chunk_p) - offset);
make_free_chunk(chunk_p, offset);
chunk_p = new_chunk_p;
}
offset = _size(chunk_p) - chunk_size(s);
/* Split off the back piece if large enough */
if (offset >= MALLOC_MINSIZE) {
*_size_ref(chunk_p) -= offset;
make_free_chunk(chunk_after(chunk_p), offset);
}
return aligned_p;
}
#ifdef __strong_reference
__strong_reference(memalign, aligned_alloc);
#endif
|
