memset2.c revision 1.1.2.3
1 /*- 2 * Copyright (c) 2009 The NetBSD Foundation, Inc. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to The NetBSD Foundation 6 * by Matt Thomas <matt (at) 3am-software.com>. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 18 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 19 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 20 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 21 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27 * POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include <sys/types.h> 31 32 #if !defined(_KERNEL) && !defined(_STANDALONE) 33 #include <assert.h> 34 #include <limits.h> 35 #include <string.h> 36 #include <inttypes.h> 37 #else 38 #include <lib/libkern/libkern.h> 39 #include <machine/limits.h> 40 #endif 41 42 #include <sys/endian.h> 43 #include <machine/types.h> 44 45 #ifdef TEST 46 #include <assert.h> 47 #define _DIAGASSERT(a) assert(a) 48 #endif 49 50 #ifdef _FORTIFY_SOURCE 51 #undef bzero 52 #undef memset 53 #endif 54 55 #if defined(LIBC_SCCS) && !defined(lint) 56 __RCSID("$NetBSD: memset2.c,v 1.1.2.3 2009/08/23 20:06:13 matt Exp $"); 57 #endif /* LIBC_SCCS and not lint */ 58 59 /* 60 * Assume uregister_t is the widest non-synthetic unsigned type. 61 */ 62 typedef uregister_t memword_t; 63 64 #ifdef BZERO 65 static inline 66 #define memset memset0 67 #endif 68 69 #ifdef TEST 70 static 71 #define memset test_memset 72 #endif 73 74 #ifdef CTASSERT 75 CTASSERT((~(memword_t)0U >> 1) != ~(memword_t)0U); 76 #endif 77 78 void * 79 memset(void *addr, int c, size_t len) 80 { 81 memword_t *dstp = addr; 82 memword_t *edstp; 83 memword_t fill; 84 #ifndef __OPTIMIZE_SIZE__ 85 memword_t keep_mask = 0; 86 #endif 87 size_t fill_count; 88 89 _DIAGASSERT(addr != 0); 90 91 if (__predict_false(len == 0)) 92 return addr; 93 94 /* 95 * Pad out the fill byte (v) across a memword_t. 96 * The conditional at the end prevents GCC from complaing about 97 * shift count >= width of type 98 */ 99 fill = c; 100 fill |= fill << 8; 101 fill |= fill << 16; 102 fill |= fill << (sizeof(c) < sizeof(fill) ? 32 : 0); 103 104 /* 105 * Get the number of unaligned bytes to fill in the first word. 106 */ 107 fill_count = -(uintptr_t)addr & (sizeof(memword_t) - 1); 108 109 if (__predict_false(fill_count != 0)) { 110 #ifndef __OPTIMIZE_SIZE__ 111 /* 112 * We want to clear <fill_count> trailing bytes in the word. 113 * On big/little endian, these are the least/most significant, 114 * bits respectively. So as we shift, the keep_mask will only 115 * have bits set for the bytes we won't be filling. 116 */ 117 #if BYTE_ORDER == BIG_ENDIAN 118 keep_mask = ~(memword_t)0U << (fill_count * 8); 119 #endif 120 #if BYTE_ORDER == LITTLE_ENDIAN 121 keep_mask = ~(memword_t)0U >> (fill_count * 8); 122 #endif 123 /* 124 * Make sure dstp is aligned to a memword_t boundary. 125 */ 126 dstp = (memword_t *)((uintptr_t)addr & -sizeof(memword_t)); 127 if (len >= fill_count) { 128 /* 129 * If we can fill the rest of this word, then we mask 130 * off the bytes we are filling and then fill in those 131 * bytes with the new fill value. 132 */ 133 *dstp = (*dstp & keep_mask) | (fill & ~keep_mask); 134 len -= fill_count; 135 if (__predict_false(len == 0)) 136 return addr; 137 /* 138 * Since we were able to fill the rest of this word, 139 * we will advance to the next word and thus have no 140 * bytes to preserve. 141 * 142 * If we don't have enough to fill the rest of this 143 * word, we will fall through the following loop 144 * (since there are no full words to fill). Then we 145 * use the keep_mask above to preserve the leading 146 * bytes of word. 147 */ 148 dstp++; 149 keep_mask = 0; 150 } else { 151 len += (uintptr_t)addr & (sizeof(memword_t) - 1); 152 } 153 #else /* __OPTIMIZE_SIZE__ */ 154 uint8_t *dp, *ep; 155 if (len < fill_count) 156 fill_count = len; 157 for (dp = (uint8_t *)dstp, ep = dp + fill_count; 158 dp != ep; dp++) 159 *dp = fill; 160 if ((len -= fill_count) == 0) 161 return addr; 162 dstp = (memword_t *)ep; 163 #endif /* __OPTIMIZE_SIZE__ */ 164 } 165 166 /* 167 * Simply fill memory one word at time (for as many full words we have 168 * to write). 169 */ 170 for (edstp = dstp + len / sizeof(memword_t); dstp != edstp; dstp++) 171 *dstp = fill; 172 173 /* 174 * We didn't subtract out the full words we just filled since we know 175 * by the time we get here we will have less than a words worth to 176 * write. So we can concern ourselves with only the subword len bits. 177 */ 178 len &= sizeof(memword_t)-1; 179 if (len > 0) { 180 #ifndef __OPTIMIZE_SIZE__ 181 /* 182 * We want to clear <len> leading bytes in the word. 183 * On big/little endian, these are the most/least significant 184 * bits, respectively, But as we want the mask of the bytes to 185 * keep, we have to complement the mask. So after we shift, 186 * the keep_mask will only have bits set for the bytes we won't 187 * be filling. 188 * 189 * But the keep_mask could already have bytes to preserve 190 * if the amount to fill was less than the amount of traiing 191 * space in the first word. 192 */ 193 #if BYTE_ORDER == BIG_ENDIAN 194 keep_mask |= ~(memword_t)0U >> (len * 8); 195 #endif 196 #if BYTE_ORDER == LITTLE_ENDIAN 197 keep_mask |= ~(memword_t)0U << (len * 8); 198 #endif 199 /* 200 * Now we mask off the bytes we are filling and then fill in 201 * those bytes with the new fill value. 202 */ 203 *dstp = (*dstp & keep_mask) | (fill & ~keep_mask); 204 #else /* __OPTIMIZE_SIZE__ */ 205 uint8_t *dp, *ep; 206 for (dp = (uint8_t *)dstp, ep = dp + len; 207 dp != ep; dp++) 208 *dp = fill; 209 #endif /* __OPTIMIZE_SIZE__ */ 210 } 211 212 /* 213 * Return the initial addr 214 */ 215 return addr; 216 } 217 218 #ifdef BZERO 219 /* 220 * For bzero, simply inline memset and let the compiler optimize things away. 221 */ 222 void 223 bzero(void *addr, size_t len) 224 { 225 memset(addr, 0, len); 226 } 227 #endif 228 229 #ifdef TEST 230 #include <stdbool.h> 231 #include <stdio.h> 232 233 #undef memset 234 235 static union { 236 uint8_t bytes[sizeof(memword_t) * 4]; 237 memword_t words[4]; 238 } testmem; 239 240 int 241 main(int argc, char **argv) 242 { 243 size_t start; 244 size_t len; 245 bool failed = false; 246 247 for (start = 1; start < sizeof(testmem) - 1; start++) { 248 for (len = 1; start + len < sizeof(testmem) - 1; len++) { 249 bool ok = true; 250 size_t i; 251 uint8_t check_value; 252 memset(testmem.bytes, 0xff, sizeof(testmem)); 253 test_memset(testmem.bytes + start, 0x00, len); 254 for (i = 0; i < sizeof(testmem); i++) { 255 if (i == 0 || i == start + len) 256 check_value = 0xff; 257 else if (i == start) 258 check_value = 0x00; 259 if (testmem.bytes[i] != check_value) { 260 if (ok) 261 printf("pass @ %zu .. %zu failed", 262 start, start + len - 1); 263 ok = false; 264 printf(" [%zu]=0x%02x(!0x%02x)", 265 i, testmem.bytes[i], check_value); 266 } 267 } 268 if (!ok) { 269 printf("\n"); 270 failed = 1; 271 } 272 } 273 } 274 275 return failed ? 1 : 0; 276 } 277 #endif /* TEST */ 278
Indexes created Sun Sep 21 16:09:51 GMT 2025