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 * 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 * 193 aligned_alloc(size_t align, size_t size) 194 { 195 return (memalign(align, size)); 196 } 197