1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 * Copyright 2016 Joyent, Inc.
26 */
27
28 /* Copyright (c) 1988 AT&T */
29 /* All Rights Reserved */
30
31 #include "lint.h"
32 #include "mallint.h"
33 #include "mtlib.h"
34
35 #define _misaligned(p) ((unsigned)(p) & 3)
36 /* 4-byte "word" alignment is considered ok in LP64 */
37 #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size)))
38
39 /*
40 * memalign(align, nbytes)
41 *
42 * Description:
43 * Returns a block of specified size on a specified alignment boundary.
44 *
45 * Algorithm:
46 * Malloc enough to ensure that a block can be aligned correctly.
47 * Find the alignment point and return the fragments
48 * before and after the block.
49 *
50 * Errors:
51 * Returns NULL and sets errno as follows:
52 * [EINVAL]
53 * if nbytes = 0,
54 * or if alignment is misaligned,
55 * or if the heap has been detectably corrupted.
56 * [ENOMEM]
57 * if the requested memory could not be allocated.
58 */
59
60 void *
memalign(size_t align,size_t nbytes)61 memalign(size_t align, size_t nbytes)
62 {
63 size_t reqsize; /* Num of bytes to get from malloc() */
64 TREE *p; /* Ptr returned from malloc() */
65 TREE *blk; /* For addressing fragment blocks */
66 size_t blksize; /* Current (shrinking) block size */
67 TREE *alignedp; /* Ptr to properly aligned boundary */
68 TREE *aligned_blk; /* The block to be returned */
69 size_t frag_size; /* size of fragments fore and aft */
70 size_t x;
71
72 if (!primary_link_map) {
73 errno = ENOTSUP;
74 return (NULL);
75 }
76
77 /*
78 * check for valid size and alignment parameters
79 * MAX_ALIGN check prevents overflow in later calculation.
80 */
81 if (nbytes == 0 || _misaligned(align) || align == 0 ||
82 align > MAX_ALIGN) {
83 errno = EINVAL;
84 return (NULL);
85 }
86
87 /*
88 * Malloc enough memory to guarantee that the result can be
89 * aligned correctly. The worst case is when malloc returns
90 * a block so close to the next alignment boundary that a
91 * fragment of minimum size cannot be created. In order to
92 * make sure we can handle this, we need to force the
93 * alignment to be at least as large as the minimum frag size
94 * (MINSIZE + WORDSIZE).
95 */
96
97 /* check for size that could overflow calculations */
98 if (nbytes > MAX_MALLOC) {
99 errno = ENOMEM;
100 return (NULL);
101 }
102 ROUND(nbytes);
103 if (nbytes < MINSIZE)
104 nbytes = MINSIZE;
105 ROUND(align);
106 while (align < MINSIZE + WORDSIZE)
107 align <<= 1;
108 reqsize = nbytes + align + (MINSIZE + WORDSIZE);
109
110 /* check for overflow */
111 if (reqsize < nbytes) {
112 errno = ENOMEM;
113 return (NULL);
114 }
115
116 p = (TREE *)malloc(reqsize);
117 if (p == (TREE *)NULL) {
118 /* malloc sets errno */
119 return (NULL);
120 }
121 (void) mutex_lock(&libc_malloc_lock);
122
123 /*
124 * get size of the entire block (overhead and all)
125 */
126 blk = BLOCK(p); /* back up to get length word */
127 blksize = SIZE(blk);
128 CLRBITS01(blksize);
129
130 /*
131 * locate the proper alignment boundary within the block.
132 */
133 x = (size_t)p;
134 if (x % align != 0)
135 x += align - (x % align);
136 alignedp = (TREE *)x;
137 aligned_blk = BLOCK(alignedp);
138
139 /*
140 * Check out the space to the left of the alignment
141 * boundary, and split off a fragment if necessary.
142 */
143 frag_size = (size_t)aligned_blk - (size_t)blk;
144 if (frag_size != 0) {
145 /*
146 * Create a fragment to the left of the aligned block.
147 */
148 if (frag_size < MINSIZE + WORDSIZE) {
149 /*
150 * Not enough space. So make the split
151 * at the other end of the alignment unit.
152 * We know this yields enough space, because
153 * we forced align >= MINSIZE + WORDSIZE above.
154 */
155 frag_size += align;
156 aligned_blk = _nextblk(aligned_blk, align);
157 }
158 blksize -= frag_size;
159 SIZE(aligned_blk) = blksize | BIT0;
160 frag_size -= WORDSIZE;
161 SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk));
162 _free_unlocked(DATA(blk));
163 }
164
165 /*
166 * Is there a (sufficiently large) fragment to the
167 * right of the aligned block?
168 */
169 frag_size = blksize - nbytes;
170 if (frag_size >= MINSIZE + WORDSIZE) {
171 /*
172 * split and free a fragment on the right
173 */
174 blksize = SIZE(aligned_blk);
175 SIZE(aligned_blk) = nbytes;
176 blk = NEXT(aligned_blk);
177 SETOLD01(SIZE(aligned_blk), blksize);
178 frag_size -= WORDSIZE;
179 SIZE(blk) = frag_size | BIT0;
180 _free_unlocked(DATA(blk));
181 }
182 (void) mutex_unlock(&libc_malloc_lock);
183 return (DATA(aligned_blk));
184 }
185
186 /*
187 * This is the ISO/IEC C11 version of memalign. We have kept it as a separate
188 * function, but it is basically the same thing. Note that this is implemented
189 * this way to make life easier to libraries which already interpose on
190 * memalign.
191 */
192 void *
aligned_alloc(size_t align,size_t size)193 aligned_alloc(size_t align, size_t size)
194 {
195 return (memalign(align, size));
196 }
197