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
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/****************************************************************************
* mm/mm_memalign.c
*
* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 THE
* COPYRIGHT OWNER OR CONTRIBUTORS 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <assert.h>
#include "mm_environment.h"
#include "mm_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: memalign
*
* Description:
* memalign requests more than enough space from malloc, finds a region
* within that chunk that meets the alignment request and then frees any
* leading or trailing space.
*
* The alignment argument must be a power of two (not checked). 8-byte
* alignment is guaranteed by normal malloc calls.
*
****************************************************************************/
FAR void *memalign(size_t alignment, size_t size)
{
FAR struct mm_allocnode_s *node;
size_t rawchunk;
size_t alignedchunk;
size_t mask = (size_t)(alignment - 1);
size_t allocsize;
/* If this requested alignement less than or equal to the natural alignment
* of malloc, then just let malloc do the work.
*/
if (alignment <= MM_MIN_CHUNK)
{
return malloc(size);
}
/* Adjust the size to account for (1) the size of the allocated node, (2)
* to make sure that it is an even multiple of our granule size, and to
* include the alignment amount.
*
* Notice that we increase the allocation size by twice the requested
* alignment. We do this so that there will be at least two valid
* alignment points within the allocated memory.
*
* NOTE: These are sizes given to malloc and not chunk sizes. They do
* not include SIZEOF_MM_ALLOCNODE.
*/
size = MM_ALIGN_UP(size); /* Make multiples of our granule size */
allocsize = size + 2*alignment; /* Add double full alignment size */
/* Then malloc that size */
rawchunk = (size_t)malloc(allocsize);
if (rawchunk == 0)
{
return NULL;
}
/* We need to hold the MM semaphore while we muck with the chunks and
* nodelist.
*/
mm_takesemaphore();
/* Get the node associated with the allocation and the next node after
* the allocation.
*/
node = (FAR struct mm_allocnode_s*)(rawchunk - SIZEOF_MM_ALLOCNODE);
/* Find the aligned subregion */
alignedchunk = (rawchunk + mask) & ~mask;
/* Check if there is free space at the beginning of the aligned chunk */
if (alignedchunk != rawchunk)
{
FAR struct mm_allocnode_s *newnode;
FAR struct mm_allocnode_s *next;
size_t precedingsize;
/* Get the node the next node after the allocation. */
next = (FAR struct mm_allocnode_s*)((char*)node + node->size);
/* Make sure that there is space to convert the preceding mm_allocnode_s
* into an mm_freenode_s. I think that this should always be true
*/
DEBUGASSERT(alignedchunk >= rawchunk + 8);
newnode = (FAR struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
/* Preceding size is full size of the new 'node,' including
* SIZEOF_MM_ALLOCNODE
*/
precedingsize = (size_t)newnode - (size_t)node;
/* If we were unlucky, then the alignedchunk can lie in such a position
* that precedingsize < SIZEOF_NODE_FREENODE. We can't let that happen
* because we are going to cast 'node' to struct mm_freenode_s below.
* This is why we allocated memory large enough to support two
* alignment points. In this case, we will simply use the second
* alignment point.
*/
if (precedingsize < SIZEOF_MM_FREENODE)
{
alignedchunk += alignment;
newnode = (FAR struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
precedingsize = (size_t)newnode - (size_t)node;
}
/* Set up the size of the new node */
newnode->size = (size_t)next - (size_t)newnode;
newnode->preceding = precedingsize | MM_ALLOC_BIT;
/* Reduce the size of the original chunk and mark it not allocated, */
node->size = precedingsize;
node->preceding &= ~MM_ALLOC_BIT;
/* Fix the preceding size of the next node */
next->preceding = newnode->size | (next->preceding & MM_ALLOC_BIT);
/* Convert the newnode chunk size back into malloc-compatible size by
* subtracting the header size SIZEOF_MM_ALLOCNODE.
*/
allocsize = newnode->size - SIZEOF_MM_ALLOCNODE;
/* Add the original, newly freed node to the free nodelist */
mm_addfreechunk((FAR struct mm_freenode_s *)node);
/* Replace the original node with the newlay realloaced,
* aligned node
*/
node = newnode;
}
/* Check if there is free space at the end of the aligned chunk */
if (allocsize > size)
{
/* Shrink the chunk by that much -- remember, mm_shrinkchunk wants
* internal chunk sizes that include SIZEOF_MM_ALLOCNODE, and not the
* malloc-compatible sizes that we have.
*/
mm_shrinkchunk(node, size + SIZEOF_MM_ALLOCNODE);
}
mm_givesemaphore();
return (FAR void*)alignedchunk;
}
|
