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 */ 26 27 /* Copyright (c) 1988 AT&T */ 28 /* All Rights Reserved */ 29 30 #pragma ident "%Z%%M% %I% %E% SMI" 31 32 #include "lint.h" 33 #include "mallint.h" 34 #include "mtlib.h" 35 36 #define _misaligned(p) ((unsigned)(p) & 3) 37 /* 4-byte "word" alignment is considered ok in LP64 */ 38 #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size))) 39 40 /* 41 * memalign(align, nbytes) 42 * 43 * Description: 44 * Returns a block of specified size on a specified alignment boundary. 45 * 46 * Algorithm: 47 * Malloc enough to ensure that a block can be aligned correctly. 48 * Find the alignment point and return the fragments 49 * before and after the block. 50 * 51 * Errors: 52 * Returns NULL and sets errno as follows: 53 * [EINVAL] 54 * if nbytes = 0, 55 * or if alignment is misaligned, 56 * or if the heap has been detectably corrupted. 57 * [ENOMEM] 58 * if the requested memory could not be allocated. 59 */ 60 61 void * 62 memalign(size_t align, size_t nbytes) 63 { 64 size_t reqsize; /* Num of bytes to get from malloc() */ 65 TREE *p; /* Ptr returned from malloc() */ 66 TREE *blk; /* For addressing fragment blocks */ 67 size_t blksize; /* Current (shrinking) block size */ 68 TREE *alignedp; /* Ptr to properly aligned boundary */ 69 TREE *aligned_blk; /* The block to be returned */ 70 size_t frag_size; /* size of fragments fore and aft */ 71 size_t x; 72 73 if (!primary_link_map) { 74 errno = ENOTSUP; 75 return (NULL); 76 } 77 78 /* 79 * check for valid size and alignment parameters 80 * MAX_ALIGN check prevents overflow in later calculation. 81 */ 82 if (nbytes == 0 || _misaligned(align) || align == 0 || 83 align > MAX_ALIGN) { 84 errno = EINVAL; 85 return (NULL); 86 } 87 88 /* 89 * Malloc enough memory to guarantee that the result can be 90 * aligned correctly. The worst case is when malloc returns 91 * a block so close to the next alignment boundary that a 92 * fragment of minimum size cannot be created. In order to 93 * make sure we can handle this, we need to force the 94 * alignment to be at least as large as the minimum frag size 95 * (MINSIZE + WORDSIZE). 96 */ 97 98 /* check for size that could overflow calculations */ 99 if (nbytes > MAX_MALLOC) { 100 errno = ENOMEM; 101 return (NULL); 102 } 103 ROUND(nbytes); 104 if (nbytes < MINSIZE) 105 nbytes = MINSIZE; 106 ROUND(align); 107 while (align < MINSIZE + WORDSIZE) 108 align <<= 1; 109 reqsize = nbytes + align + (MINSIZE + WORDSIZE); 110 111 /* check for overflow */ 112 if (reqsize < nbytes) { 113 errno = ENOMEM; 114 return (NULL); 115 } 116 117 p = (TREE *)malloc(reqsize); 118 if (p == (TREE *)NULL) { 119 /* malloc sets errno */ 120 return (NULL); 121 } 122 (void) mutex_lock(&libc_malloc_lock); 123 124 /* 125 * get size of the entire block (overhead and all) 126 */ 127 blk = BLOCK(p); /* back up to get length word */ 128 blksize = SIZE(blk); 129 CLRBITS01(blksize); 130 131 /* 132 * locate the proper alignment boundary within the block. 133 */ 134 x = (size_t)p; 135 if (x % align != 0) 136 x += align - (x % align); 137 alignedp = (TREE *)x; 138 aligned_blk = BLOCK(alignedp); 139 140 /* 141 * Check out the space to the left of the alignment 142 * boundary, and split off a fragment if necessary. 143 */ 144 frag_size = (size_t)aligned_blk - (size_t)blk; 145 if (frag_size != 0) { 146 /* 147 * Create a fragment to the left of the aligned block. 148 */ 149 if (frag_size < MINSIZE + WORDSIZE) { 150 /* 151 * Not enough space. So make the split 152 * at the other end of the alignment unit. 153 * We know this yields enough space, because 154 * we forced align >= MINSIZE + WORDSIZE above. 155 */ 156 frag_size += align; 157 aligned_blk = _nextblk(aligned_blk, align); 158 } 159 blksize -= frag_size; 160 SIZE(aligned_blk) = blksize | BIT0; 161 frag_size -= WORDSIZE; 162 SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk)); 163 _free_unlocked(DATA(blk)); 164 } 165 166 /* 167 * Is there a (sufficiently large) fragment to the 168 * right of the aligned block? 169 */ 170 frag_size = blksize - nbytes; 171 if (frag_size >= MINSIZE + WORDSIZE) { 172 /* 173 * split and free a fragment on the right 174 */ 175 blksize = SIZE(aligned_blk); 176 SIZE(aligned_blk) = nbytes; 177 blk = NEXT(aligned_blk); 178 SETOLD01(SIZE(aligned_blk), blksize); 179 frag_size -= WORDSIZE; 180 SIZE(blk) = frag_size | BIT0; 181 _free_unlocked(DATA(blk)); 182 } 183 (void) mutex_unlock(&libc_malloc_lock); 184 return (DATA(aligned_blk)); 185 } 186