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 2006 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 #pragma weak memalign = _memalign 33 34 #include "synonyms.h" 35 #include "mallint.h" 36 #include "mtlib.h" 37 38 #define _misaligned(p) ((unsigned)(p) & 3) 39 /* 4-byte "word" alignment is considered ok in LP64 */ 40 #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size))) 41 42 /* 43 * memalign(align, nbytes) 44 * 45 * Description: 46 * Returns a block of specified size on a specified alignment boundary. 47 * 48 * Algorithm: 49 * Malloc enough to ensure that a block can be aligned correctly. 50 * Find the alignment point and return the fragments 51 * before and after the block. 52 * 53 * Errors: 54 * Returns NULL and sets errno as follows: 55 * [EINVAL] 56 * if nbytes = 0, 57 * or if alignment is misaligned, 58 * or if the heap has been detectably corrupted. 59 * [ENOMEM] 60 * if the requested memory could not be allocated. 61 */ 62 63 void * 64 memalign(size_t align, size_t nbytes) 65 { 66 size_t reqsize; /* Num of bytes to get from malloc() */ 67 TREE *p; /* Ptr returned from malloc() */ 68 TREE *blk; /* For addressing fragment blocks */ 69 size_t blksize; /* Current (shrinking) block size */ 70 TREE *alignedp; /* Ptr to properly aligned boundary */ 71 TREE *aligned_blk; /* The block to be returned */ 72 size_t frag_size; /* size of fragments fore and aft */ 73 size_t x; 74 75 /* 76 * check for valid size and alignment parameters 77 * MAX_ALIGN check prevents overflow in later calculation. 78 */ 79 if (nbytes == 0 || _misaligned(align) || align == 0 || 80 align > MAX_ALIGN) { 81 errno = EINVAL; 82 return (NULL); 83 } 84 85 /* 86 * Malloc enough memory to guarantee that the result can be 87 * aligned correctly. The worst case is when malloc returns 88 * a block so close to the next alignment boundary that a 89 * fragment of minimum size cannot be created. In order to 90 * make sure we can handle this, we need to force the 91 * alignment to be at least as large as the minimum frag size 92 * (MINSIZE + WORDSIZE). 93 */ 94 95 /* check for size that could overflow calculations */ 96 if (nbytes > MAX_MALLOC) { 97 errno = ENOMEM; 98 return (NULL); 99 } 100 ROUND(nbytes); 101 if (nbytes < MINSIZE) 102 nbytes = MINSIZE; 103 ROUND(align); 104 while (align < MINSIZE + WORDSIZE) 105 align <<= 1; 106 reqsize = nbytes + align + (MINSIZE + WORDSIZE); 107 108 /* check for overflow */ 109 if (reqsize < nbytes) { 110 errno = ENOMEM; 111 return (NULL); 112 } 113 114 p = (TREE *)malloc(reqsize); 115 if (p == (TREE *)NULL) { 116 /* malloc sets errno */ 117 return (NULL); 118 } 119 (void) _private_mutex_lock(&libc_malloc_lock); 120 121 /* 122 * get size of the entire block (overhead and all) 123 */ 124 blk = BLOCK(p); /* back up to get length word */ 125 blksize = SIZE(blk); 126 CLRBITS01(blksize); 127 128 /* 129 * locate the proper alignment boundary within the block. 130 */ 131 x = (size_t)p; 132 if (x % align != 0) 133 x += align - (x % align); 134 alignedp = (TREE *)x; 135 aligned_blk = BLOCK(alignedp); 136 137 /* 138 * Check out the space to the left of the alignment 139 * boundary, and split off a fragment if necessary. 140 */ 141 frag_size = (size_t)aligned_blk - (size_t)blk; 142 if (frag_size != 0) { 143 /* 144 * Create a fragment to the left of the aligned block. 145 */ 146 if (frag_size < MINSIZE + WORDSIZE) { 147 /* 148 * Not enough space. So make the split 149 * at the other end of the alignment unit. 150 * We know this yields enough space, because 151 * we forced align >= MINSIZE + WORDSIZE above. 152 */ 153 frag_size += align; 154 aligned_blk = _nextblk(aligned_blk, align); 155 } 156 blksize -= frag_size; 157 SIZE(aligned_blk) = blksize | BIT0; 158 frag_size -= WORDSIZE; 159 SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk)); 160 _free_unlocked(DATA(blk)); 161 } 162 163 /* 164 * Is there a (sufficiently large) fragment to the 165 * right of the aligned block? 166 */ 167 frag_size = blksize - nbytes; 168 if (frag_size >= MINSIZE + WORDSIZE) { 169 /* 170 * split and free a fragment on the right 171 */ 172 blksize = SIZE(aligned_blk); 173 SIZE(aligned_blk) = nbytes; 174 blk = NEXT(aligned_blk); 175 SETOLD01(SIZE(aligned_blk), blksize); 176 frag_size -= WORDSIZE; 177 SIZE(blk) = frag_size | BIT0; 178 _free_unlocked(DATA(blk)); 179 } 180 (void) _private_mutex_unlock(&libc_malloc_lock); 181 return (DATA(aligned_blk)); 182 } 183