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, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 /* Copyright (c) 1988 AT&T */ 30 /* All Rights Reserved */ 31 32 33 #pragma weak memalign = _memalign 34 35 #include "synonyms.h" 36 #include "mallint.h" 37 #include "mtlib.h" 38 39 #define _misaligned(p) ((unsigned)(p) & 3) 40 /* 4-byte "word" alignment is considered ok in LP64 */ 41 #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size))) 42 43 /* 44 * memalign(align, nbytes) 45 * 46 * Description: 47 * Returns a block of specified size on a specified alignment boundary. 48 * 49 * Algorithm: 50 * Malloc enough to ensure that a block can be aligned correctly. 51 * Find the alignment point and return the fragments 52 * before and after the block. 53 * 54 * Errors: 55 * Returns NULL and sets errno as follows: 56 * [EINVAL] 57 * if nbytes = 0, 58 * or if alignment is misaligned, 59 * or if the heap has been detectably corrupted. 60 * [ENOMEM] 61 * if the requested memory could not be allocated. 62 */ 63 64 void * 65 memalign(size_t align, size_t nbytes) 66 { 67 size_t reqsize; /* Num of bytes to get from malloc() */ 68 TREE *p; /* Ptr returned from malloc() */ 69 TREE *blk; /* For addressing fragment blocks */ 70 size_t blksize; /* Current (shrinking) block size */ 71 TREE *alignedp; /* Ptr to properly aligned boundary */ 72 TREE *aligned_blk; /* The block to be returned */ 73 size_t frag_size; /* size of fragments fore and aft */ 74 size_t x; 75 76 /* 77 * check for valid size and alignment parameters 78 * MAX_ALIGN check prevents overflow in later calculation. 79 */ 80 if (nbytes == 0 || _misaligned(align) || align == 0 || 81 align > MAX_ALIGN) { 82 errno = EINVAL; 83 return (NULL); 84 } 85 86 /* 87 * Malloc enough memory to guarantee that the result can be 88 * aligned correctly. The worst case is when malloc returns 89 * a block so close to the next alignment boundary that a 90 * fragment of minimum size cannot be created. In order to 91 * make sure we can handle this, we need to force the 92 * alignment to be at least as large as the minimum frag size 93 * (MINSIZE + WORDSIZE). 94 */ 95 96 /* check for size that could overflow calculations */ 97 if (nbytes > MAX_MALLOC) { 98 errno = ENOMEM; 99 return (NULL); 100 } 101 ROUND(nbytes); 102 if (nbytes < MINSIZE) 103 nbytes = MINSIZE; 104 ROUND(align); 105 while (align < MINSIZE + WORDSIZE) 106 align <<= 1; 107 reqsize = nbytes + align + (MINSIZE + WORDSIZE); 108 109 /* check for overflow */ 110 if (reqsize < nbytes) { 111 errno = ENOMEM; 112 return (NULL); 113 } 114 115 p = (TREE *)malloc(reqsize); 116 if (p == (TREE *)NULL) { 117 /* malloc sets errno */ 118 return (NULL); 119 } 120 lmutex_lock(&libc_malloc_lock); 121 122 /* 123 * get size of the entire block (overhead and all) 124 */ 125 blk = BLOCK(p); /* back up to get length word */ 126 blksize = SIZE(blk); 127 CLRBITS01(blksize); 128 129 /* 130 * locate the proper alignment boundary within the block. 131 */ 132 x = (size_t)p; 133 if (x % align != 0) 134 x += align - (x % align); 135 alignedp = (TREE *)x; 136 aligned_blk = BLOCK(alignedp); 137 138 /* 139 * Check out the space to the left of the alignment 140 * boundary, and split off a fragment if necessary. 141 */ 142 frag_size = (size_t)aligned_blk - (size_t)blk; 143 if (frag_size != 0) { 144 /* 145 * Create a fragment to the left of the aligned block. 146 */ 147 if (frag_size < MINSIZE + WORDSIZE) { 148 /* 149 * Not enough space. So make the split 150 * at the other end of the alignment unit. 151 * We know this yields enough space, because 152 * we forced align >= MINSIZE + WORDSIZE above. 153 */ 154 frag_size += align; 155 aligned_blk = _nextblk(aligned_blk, align); 156 } 157 blksize -= frag_size; 158 SIZE(aligned_blk) = blksize | BIT0; 159 frag_size -= WORDSIZE; 160 SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk)); 161 _free_unlocked(DATA(blk)); 162 } 163 164 /* 165 * Is there a (sufficiently large) fragment to the 166 * right of the aligned block? 167 */ 168 frag_size = blksize - nbytes; 169 if (frag_size >= MINSIZE + WORDSIZE) { 170 /* 171 * split and free a fragment on the right 172 */ 173 blksize = SIZE(aligned_blk); 174 SIZE(aligned_blk) = nbytes; 175 blk = NEXT(aligned_blk); 176 SETOLD01(SIZE(aligned_blk), blksize); 177 frag_size -= WORDSIZE; 178 SIZE(blk) = frag_size | BIT0; 179 _free_unlocked(DATA(blk)); 180 } 181 lmutex_unlock(&libc_malloc_lock); 182 return (DATA(aligned_blk)); 183 } 184