Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/in_cksum.c
Version:
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1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * from tahoe: in_cksum.c 1.2 86/01/05 30 * from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 /* 37 * MPsafe: alfred 38 */ 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/mbuf.h> 42 43 #include <netinet/in.h> 44 #include <netinet/in_systm.h> 45 #include <netinet/ip.h> 46 47 #include <machine/in_cksum.h> 48 49 /* 50 * Checksum routine for Internet Protocol family headers. 51 * 52 * This routine is very heavily used in the network 53 * code and should be modified for each CPU to be as fast as possible. 54 * 55 * This implementation is 386 version. 56 */ 57 58 #undef ADDCARRY 59 #define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff 60 #if !defined(__GNUC__) || defined(__INTEL_COMPILER) 61 /* non gcc parts stolen from sys/alpha/alpha/in_cksum.c */ 62 #define REDUCE32 \ 63 { \ 64 q_util.q = sum; \ 65 sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \ 66 } 67 #define REDUCE16 \ 68 { \ 69 q_util.q = sum; \ 70 l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \ 71 sum = l_util.s[0] + l_util.s[1]; \ 72 ADDCARRY(sum); \ 73 } 74 #endif 75 #define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);} 76 77 #if !defined(__GNUC__) || defined(__INTEL_COMPILER) 78 static const u_int32_t in_masks[] = { 79 /*0 bytes*/ /*1 byte*/ /*2 bytes*/ /*3 bytes*/ 80 0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF, /* offset 0 */ 81 0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00, /* offset 1 */ 82 0x00000000, 0x00FF0000, 0xFFFF0000, 0xFFFF0000, /* offset 2 */ 83 0x00000000, 0xFF000000, 0xFF000000, 0xFF000000, /* offset 3 */ 84 }; 85 86 union l_util { 87 u_int16_t s[2]; 88 u_int32_t l; 89 }; 90 union q_util { 91 u_int16_t s[4]; 92 u_int32_t l[2]; 93 u_int64_t q; 94 }; 95 96 static u_int64_t 97 in_cksumdata(const u_int32_t *lw, int len) 98 { 99 u_int64_t sum = 0; 100 u_int64_t prefilled; 101 int offset; 102 union q_util q_util; 103 104 if ((3 & (long) lw) == 0 && len == 20) { 105 sum = (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3] + lw[4]; 106 REDUCE32; 107 return sum; 108 } 109 110 if ((offset = 3 & (long) lw) != 0) { 111 const u_int32_t *masks = in_masks + (offset << 2); 112 lw = (u_int32_t *) (((long) lw) - offset); 113 sum = *lw++ & masks[len >= 3 ? 3 : len]; 114 len -= 4 - offset; 115 if (len <= 0) { 116 REDUCE32; 117 return sum; 118 } 119 } 120 #if 0 121 /* 122 * Force to cache line boundary. 123 */ 124 offset = 32 - (0x1f & (long) lw); 125 if (offset < 32 && len > offset) { 126 len -= offset; 127 if (4 & offset) { 128 sum += (u_int64_t) lw[0]; 129 lw += 1; 130 } 131 if (8 & offset) { 132 sum += (u_int64_t) lw[0] + lw[1]; 133 lw += 2; 134 } 135 if (16 & offset) { 136 sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3]; 137 lw += 4; 138 } 139 } 140 #endif 141 /* 142 * access prefilling to start load of next cache line. 143 * then add current cache line 144 * save result of prefilling for loop iteration. 145 */ 146 prefilled = lw[0]; 147 while ((len -= 32) >= 4) { 148 u_int64_t prefilling = lw[8]; 149 sum += prefilled + lw[1] + lw[2] + lw[3] 150 + lw[4] + lw[5] + lw[6] + lw[7]; 151 lw += 8; 152 prefilled = prefilling; 153 } 154 if (len >= 0) { 155 sum += prefilled + lw[1] + lw[2] + lw[3] 156 + lw[4] + lw[5] + lw[6] + lw[7]; 157 lw += 8; 158 } else { 159 len += 32; 160 } 161 while ((len -= 16) >= 0) { 162 sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3]; 163 lw += 4; 164 } 165 len += 16; 166 while ((len -= 4) >= 0) { 167 sum += (u_int64_t) *lw++; 168 } 169 len += 4; 170 if (len > 0) 171 sum += (u_int64_t) (in_masks[len] & *lw); 172 REDUCE32; 173 return sum; 174 } 175 176 u_short 177 in_addword(u_short a, u_short b) 178 { 179 u_int64_t sum = a + b; 180 181 ADDCARRY(sum); 182 return (sum); 183 } 184 185 u_short 186 in_pseudo(u_int32_t a, u_int32_t b, u_int32_t c) 187 { 188 u_int64_t sum; 189 union q_util q_util; 190 union l_util l_util; 191 192 sum = (u_int64_t) a + b + c; 193 REDUCE16; 194 return (sum); 195 } 196 197 u_short 198 in_cksum_skip(struct mbuf *m, int len, int skip) 199 { 200 u_int64_t sum = 0; 201 int mlen = 0; 202 int clen = 0; 203 caddr_t addr; 204 union q_util q_util; 205 union l_util l_util; 206 207 len -= skip; 208 for (; skip && m; m = m->m_next) { 209 if (m->m_len > skip) { 210 mlen = m->m_len - skip; 211 addr = mtod(m, caddr_t) + skip; 212 goto skip_start; 213 } else { 214 skip -= m->m_len; 215 } 216 } 217 218 for (; m && len; m = m->m_next) { 219 if (m->m_len == 0) 220 continue; 221 mlen = m->m_len; 222 addr = mtod(m, caddr_t); 223 skip_start: 224 if (len < mlen) 225 mlen = len; 226 if ((clen ^ (long) addr) & 1) 227 sum += in_cksumdata((const u_int32_t *)addr, mlen) << 8; 228 else 229 sum += in_cksumdata((const u_int32_t *)addr, mlen); 230 231 clen += mlen; 232 len -= mlen; 233 } 234 REDUCE16; 235 return (~sum & 0xffff); 236 } 237 238 u_int in_cksum_hdr(const struct ip *ip) 239 { 240 u_int64_t sum = in_cksumdata((const u_int32_t *)ip, sizeof(struct ip)); 241 union q_util q_util; 242 union l_util l_util; 243 244 REDUCE16; 245 return (~sum & 0xffff); 246 } 247 #else 248 249 /* 250 * These asm statements require __volatile because they pass information 251 * via the condition codes. GCC does not currently provide a way to specify 252 * the condition codes as an input or output operand. 253 * 254 * The LOAD macro below is effectively a prefetch into cache. GCC will 255 * load the value into a register but will not use it. Since modern CPUs 256 * reorder operations, this will generally take place in parallel with 257 * other calculations. 258 */ 259 #define ADD(n) __asm __volatile \ 260 ("addl %1, %0" : "+r" (sum) : \ 261 "g" (((const u_int32_t *)w)[n / 4])) 262 #define ADDC(n) __asm __volatile \ 263 ("adcl %1, %0" : "+r" (sum) : \ 264 "g" (((const u_int32_t *)w)[n / 4])) 265 #define LOAD(n) __asm __volatile \ 266 ("" : : "r" (((const u_int32_t *)w)[n / 4])) 267 #define MOP __asm __volatile \ 268 ("adcl $0, %0" : "+r" (sum)) 269 270 u_short 271 in_cksum_skip(m, len, skip) 272 struct mbuf *m; 273 int len; 274 int skip; 275 { 276 register u_short *w; 277 register unsigned sum = 0; 278 register int mlen = 0; 279 int byte_swapped = 0; 280 union { char c[2]; u_short s; } su; 281 282 len -= skip; 283 for (; skip && m; m = m->m_next) { 284 if (m->m_len > skip) { 285 mlen = m->m_len - skip; 286 w = (u_short *)(mtod(m, u_char *) + skip); 287 goto skip_start; 288 } else { 289 skip -= m->m_len; 290 } 291 } 292 293 for (;m && len; m = m->m_next) { 294 if (m->m_len == 0) 295 continue; 296 w = mtod(m, u_short *); 297 if (mlen == -1) { 298 /* 299 * The first byte of this mbuf is the continuation 300 * of a word spanning between this mbuf and the 301 * last mbuf. 302 */ 303 304 /* su.c[0] is already saved when scanning previous 305 * mbuf. sum was REDUCEd when we found mlen == -1 306 */ 307 su.c[1] = *(u_char *)w; 308 sum += su.s; 309 w = (u_short *)((char *)w + 1); 310 mlen = m->m_len - 1; 311 len--; 312 } else 313 mlen = m->m_len; 314 skip_start: 315 if (len < mlen) 316 mlen = len; 317 len -= mlen; 318 /* 319 * Force to long boundary so we do longword aligned 320 * memory operations 321 */ 322 if (3 & (int) w) { 323 REDUCE; 324 if ((1 & (int) w) && (mlen > 0)) { 325 sum <<= 8; 326 su.c[0] = *(char *)w; 327 w = (u_short *)((char *)w + 1); 328 mlen--; 329 byte_swapped = 1; 330 } 331 if ((2 & (int) w) && (mlen >= 2)) { 332 sum += *w++; 333 mlen -= 2; 334 } 335 } 336 /* 337 * Advance to a 486 cache line boundary. 338 */ 339 if (4 & (int) w && mlen >= 4) { 340 ADD(0); 341 MOP; 342 w += 2; 343 mlen -= 4; 344 } 345 if (8 & (int) w && mlen >= 8) { 346 ADD(0); 347 ADDC(4); 348 MOP; 349 w += 4; 350 mlen -= 8; 351 } 352 /* 353 * Do as much of the checksum as possible 32 bits at at time. 354 * In fact, this loop is unrolled to make overhead from 355 * branches &c small. 356 */ 357 mlen -= 1; 358 while ((mlen -= 32) >= 0) { 359 /* 360 * Add with carry 16 words and fold in the last 361 * carry by adding a 0 with carry. 362 * 363 * The early ADD(16) and the LOAD(32) are to load 364 * the next 2 cache lines in advance on 486's. The 365 * 486 has a penalty of 2 clock cycles for loading 366 * a cache line, plus whatever time the external 367 * memory takes to load the first word(s) addressed. 368 * These penalties are unavoidable. Subsequent 369 * accesses to a cache line being loaded (and to 370 * other external memory?) are delayed until the 371 * whole load finishes. These penalties are mostly 372 * avoided by not accessing external memory for 373 * 8 cycles after the ADD(16) and 12 cycles after 374 * the LOAD(32). The loop terminates when mlen 375 * is initially 33 (not 32) to guaranteed that 376 * the LOAD(32) is within bounds. 377 */ 378 ADD(16); 379 ADDC(0); 380 ADDC(4); 381 ADDC(8); 382 ADDC(12); 383 LOAD(32); 384 ADDC(20); 385 ADDC(24); 386 ADDC(28); 387 MOP; 388 w += 16; 389 } 390 mlen += 32 + 1; 391 if (mlen >= 32) { 392 ADD(16); 393 ADDC(0); 394 ADDC(4); 395 ADDC(8); 396 ADDC(12); 397 ADDC(20); 398 ADDC(24); 399 ADDC(28); 400 MOP; 401 w += 16; 402 mlen -= 32; 403 } 404 if (mlen >= 16) { 405 ADD(0); 406 ADDC(4); 407 ADDC(8); 408 ADDC(12); 409 MOP; 410 w += 8; 411 mlen -= 16; 412 } 413 if (mlen >= 8) { 414 ADD(0); 415 ADDC(4); 416 MOP; 417 w += 4; 418 mlen -= 8; 419 } 420 if (mlen == 0 && byte_swapped == 0) 421 continue; /* worth 1% maybe ?? */ 422 REDUCE; 423 while ((mlen -= 2) >= 0) { 424 sum += *w++; 425 } 426 if (byte_swapped) { 427 sum <<= 8; 428 byte_swapped = 0; 429 if (mlen == -1) { 430 su.c[1] = *(char *)w; 431 sum += su.s; 432 mlen = 0; 433 } else 434 mlen = -1; 435 } else if (mlen == -1) 436 /* 437 * This mbuf has odd number of bytes. 438 * There could be a word split betwen 439 * this mbuf and the next mbuf. 440 * Save the last byte (to prepend to next mbuf). 441 */ 442 su.c[0] = *(char *)w; 443 } 444 445 if (len) 446 printf("%s: out of data by %d\n", __func__, len); 447 if (mlen == -1) { 448 /* The last mbuf has odd # of bytes. Follow the 449 standard (the odd byte is shifted left by 8 bits) */ 450 su.c[1] = 0; 451 sum += su.s; 452 } 453 REDUCE; 454 return (~sum & 0xffff); 455 } 456 #endif
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