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 * Copyright 2024 Oxide Computer Company 27 */ 28 29 /* Copyright (c) 1988 AT&T */ 30 /* All Rights Reserved */ 31 32 #include "lint.h" 33 #include "mallint.h" 34 #include "mtlib.h" 35 #include <stdalign.h> 36 37 #define _misaligned(p) ((unsigned)(p) & 3) 38 /* 4-byte "word" alignment is considered ok in LP64 */ 39 #define _nextblk(p, size) ((TREE *)((uintptr_t)(p) + (size))) 40 41 /* 42 * memalign(align, nbytes) 43 * 44 * Description: 45 * Returns a block of specified size on a specified alignment boundary. 46 * 47 * Algorithm: 48 * Malloc enough to ensure that a block can be aligned correctly. 49 * Find the alignment point and return the fragments 50 * before and after the block. 51 * 52 * Errors: 53 * Returns NULL and sets errno as follows: 54 * [EINVAL] 55 * if nbytes = 0, 56 * or if alignment is misaligned, 57 * or if the heap has been detectably corrupted. 58 * [ENOMEM] 59 * if the requested memory could not be allocated. 60 */ 61 62 void * 63 memalign(size_t align, size_t nbytes) 64 { 65 size_t reqsize; /* Num of bytes to get from malloc() */ 66 TREE *p; /* Ptr returned from malloc() */ 67 TREE *blk; /* For addressing fragment blocks */ 68 size_t blksize; /* Current (shrinking) block size */ 69 TREE *alignedp; /* Ptr to properly aligned boundary */ 70 TREE *aligned_blk; /* The block to be returned */ 71 size_t frag_size; /* size of fragments fore and aft */ 72 size_t x; 73 74 if (!primary_link_map) { 75 errno = ENOTSUP; 76 return (NULL); 77 } 78 79 /* 80 * check for valid size and alignment parameters 81 * MAX_ALIGN check prevents overflow in later calculation. 82 */ 83 if (nbytes == 0 || _misaligned(align) || align == 0 || 84 align > MAX_ALIGN) { 85 errno = EINVAL; 86 return (NULL); 87 } 88 89 /* 90 * Malloc enough memory to guarantee that the result can be 91 * aligned correctly. The worst case is when malloc returns 92 * a block so close to the next alignment boundary that a 93 * fragment of minimum size cannot be created. In order to 94 * make sure we can handle this, we need to force the 95 * alignment to be at least as large as the minimum frag size 96 * (MINSIZE + WORDSIZE). 97 */ 98 99 /* check for size that could overflow calculations */ 100 if (nbytes > MAX_MALLOC) { 101 errno = ENOMEM; 102 return (NULL); 103 } 104 ROUND(nbytes); 105 if (nbytes < MINSIZE) 106 nbytes = MINSIZE; 107 ROUND(align); 108 while (align < MINSIZE + WORDSIZE) 109 align <<= 1; 110 reqsize = nbytes + align + (MINSIZE + WORDSIZE); 111 112 /* check for overflow */ 113 if (reqsize < nbytes) { 114 errno = ENOMEM; 115 return (NULL); 116 } 117 118 p = (TREE *)malloc(reqsize); 119 if (p == (TREE *)NULL) { 120 /* malloc sets errno */ 121 return (NULL); 122 } 123 (void) mutex_lock(&libc_malloc_lock); 124 125 /* 126 * get size of the entire block (overhead and all) 127 */ 128 blk = BLOCK(p); /* back up to get length word */ 129 blksize = SIZE(blk); 130 CLRBITS01(blksize); 131 132 /* 133 * locate the proper alignment boundary within the block. 134 */ 135 x = (size_t)p; 136 if (x % align != 0) 137 x += align - (x % align); 138 alignedp = (TREE *)x; 139 aligned_blk = BLOCK(alignedp); 140 141 /* 142 * Check out the space to the left of the alignment 143 * boundary, and split off a fragment if necessary. 144 */ 145 frag_size = (size_t)aligned_blk - (size_t)blk; 146 if (frag_size != 0) { 147 /* 148 * Create a fragment to the left of the aligned block. 149 */ 150 if (frag_size < MINSIZE + WORDSIZE) { 151 /* 152 * Not enough space. So make the split 153 * at the other end of the alignment unit. 154 * We know this yields enough space, because 155 * we forced align >= MINSIZE + WORDSIZE above. 156 */ 157 frag_size += align; 158 aligned_blk = _nextblk(aligned_blk, align); 159 } 160 blksize -= frag_size; 161 SIZE(aligned_blk) = blksize | BIT0; 162 frag_size -= WORDSIZE; 163 SIZE(blk) = frag_size | BIT0 | ISBIT1(SIZE(blk)); 164 _free_unlocked(DATA(blk)); 165 } 166 167 /* 168 * Is there a (sufficiently large) fragment to the 169 * right of the aligned block? 170 */ 171 frag_size = blksize - nbytes; 172 if (frag_size >= MINSIZE + WORDSIZE) { 173 /* 174 * split and free a fragment on the right 175 */ 176 blksize = SIZE(aligned_blk); 177 SIZE(aligned_blk) = nbytes; 178 blk = NEXT(aligned_blk); 179 SETOLD01(SIZE(aligned_blk), blksize); 180 frag_size -= WORDSIZE; 181 SIZE(blk) = frag_size | BIT0; 182 _free_unlocked(DATA(blk)); 183 } 184 (void) mutex_unlock(&libc_malloc_lock); 185 return (DATA(aligned_blk)); 186 } 187 188 /* 189 * This is the ISO/IEC C11 version of memalign. We have kept it as a separate 190 * function, but it is almost the same thing. aligned_alloc allows any alignment 191 * that is a fundamental alignment of one of the data types. However, 192 * aligned_alloc (like malloc) is required to ensure that the alignment is good 193 * for any of the base data objects. Our expectation is that memalign guarantees 194 * this. To work with memalign(), we round up any smaller alignments to the 195 * alignment of a pointer which is generally the requirement of memalign(3C). 196 * 197 * Note, aligned_alloc is implemented in terms of just calling memalign this way 198 * so that way interposing libraries can just interpose on that. 199 */ 200 void * 201 aligned_alloc(size_t align, size_t size) 202 { 203 if (align == 0 || (align & (align - 1)) != 0) { 204 errno = EINVAL; 205 return (NULL); 206 } 207 208 if (align < alignof (uintptr_t)) 209 align = alignof (uintptr_t); 210 211 return (memalign(align, size)); 212 } 213