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