1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * from tahoe: in_cksum.c 1.2 86/01/05
32 */
33
34 #include <sys/param.h>
35 #include <sys/systm.h>
36 #include <sys/mbuf.h>
37
38 #include <netinet/in.h>
39 #include <netinet/in_systm.h>
40 #include <netinet/ip.h>
41
42 #include <machine/in_cksum.h>
43
44 /*
45 * Checksum routine for Internet Protocol family headers.
46 *
47 * This routine is very heavily used in the network
48 * code and should be modified for each CPU to be as fast as possible.
49 *
50 * This implementation is 386 version.
51 */
52
53 #undef ADDCARRY
54 #define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff
55 #define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
56
57 /*
58 * These asm statements require __volatile because they pass information
59 * via the condition codes. GCC does not currently provide a way to specify
60 * the condition codes as an input or output operand.
61 *
62 * The LOAD macro below is effectively a prefetch into cache. GCC will
63 * load the value into a register but will not use it. Since modern CPUs
64 * reorder operations, this will generally take place in parallel with
65 * other calculations.
66 */
67 u_short
in_cksum_skip(struct mbuf * m,int len,int skip)68 in_cksum_skip(struct mbuf *m, int len, int skip)
69 {
70 u_short *w;
71 unsigned sum = 0;
72 int mlen = 0;
73 int byte_swapped = 0;
74 union { char c[2]; u_short s; } su;
75
76 len -= skip;
77 for (; skip && m; m = m->m_next) {
78 if (m->m_len > skip) {
79 mlen = m->m_len - skip;
80 w = (u_short *)(mtod(m, u_char *) + skip);
81 goto skip_start;
82 } else {
83 skip -= m->m_len;
84 }
85 }
86
87 for (;m && len; m = m->m_next) {
88 if (m->m_len == 0)
89 continue;
90 w = mtod(m, u_short *);
91 if (mlen == -1) {
92 /*
93 * The first byte of this mbuf is the continuation
94 * of a word spanning between this mbuf and the
95 * last mbuf.
96 */
97
98 /* su.c[0] is already saved when scanning previous
99 * mbuf. sum was REDUCEd when we found mlen == -1
100 */
101 su.c[1] = *(u_char *)w;
102 sum += su.s;
103 w = (u_short *)((char *)w + 1);
104 mlen = m->m_len - 1;
105 len--;
106 } else
107 mlen = m->m_len;
108 skip_start:
109 if (len < mlen)
110 mlen = len;
111 len -= mlen;
112 /*
113 * Force to long boundary so we do longword aligned
114 * memory operations
115 */
116 if (3 & (int) w) {
117 REDUCE;
118 if ((1 & (int) w) && (mlen > 0)) {
119 sum <<= 8;
120 su.c[0] = *(char *)w;
121 w = (u_short *)((char *)w + 1);
122 mlen--;
123 byte_swapped = 1;
124 }
125 if ((2 & (int) w) && (mlen >= 2)) {
126 sum += *w++;
127 mlen -= 2;
128 }
129 }
130 /*
131 * Advance to a 486 cache line boundary.
132 */
133 if (4 & (int) w && mlen >= 4) {
134 __asm __volatile (
135 "addl %1, %0\n"
136 "adcl $0, %0"
137 : "+r" (sum)
138 : "g" (((const u_int32_t *)w)[0])
139 );
140 w += 2;
141 mlen -= 4;
142 }
143 if (8 & (int) w && mlen >= 8) {
144 __asm __volatile (
145 "addl %1, %0\n"
146 "adcl %2, %0\n"
147 "adcl $0, %0"
148 : "+r" (sum)
149 : "g" (((const u_int32_t *)w)[0]),
150 "g" (((const u_int32_t *)w)[1])
151 );
152 w += 4;
153 mlen -= 8;
154 }
155 /*
156 * Do as much of the checksum as possible 32 bits at at time.
157 * In fact, this loop is unrolled to make overhead from
158 * branches &c small.
159 */
160 mlen -= 1;
161 while ((mlen -= 32) >= 0) {
162 /*
163 * Add with carry 16 words and fold in the last
164 * carry by adding a 0 with carry.
165 *
166 * The early ADD(16) and the LOAD(32) are to load
167 * the next 2 cache lines in advance on 486's. The
168 * 486 has a penalty of 2 clock cycles for loading
169 * a cache line, plus whatever time the external
170 * memory takes to load the first word(s) addressed.
171 * These penalties are unavoidable. Subsequent
172 * accesses to a cache line being loaded (and to
173 * other external memory?) are delayed until the
174 * whole load finishes. These penalties are mostly
175 * avoided by not accessing external memory for
176 * 8 cycles after the ADD(16) and 12 cycles after
177 * the LOAD(32). The loop terminates when mlen
178 * is initially 33 (not 32) to guaranteed that
179 * the LOAD(32) is within bounds.
180 */
181 __asm __volatile (
182 "addl %1, %0\n"
183 "adcl %2, %0\n"
184 "adcl %3, %0\n"
185 "adcl %4, %0\n"
186 "adcl %5, %0\n"
187 "mov %6, %%eax\n"
188 "adcl %7, %0\n"
189 "adcl %8, %0\n"
190 "adcl %9, %0\n"
191 "adcl $0, %0"
192 : "+r" (sum)
193 : "g" (((const u_int32_t *)w)[4]),
194 "g" (((const u_int32_t *)w)[0]),
195 "g" (((const u_int32_t *)w)[1]),
196 "g" (((const u_int32_t *)w)[2]),
197 "g" (((const u_int32_t *)w)[3]),
198 "g" (((const u_int32_t *)w)[8]),
199 "g" (((const u_int32_t *)w)[5]),
200 "g" (((const u_int32_t *)w)[6]),
201 "g" (((const u_int32_t *)w)[7])
202 : "eax"
203 );
204 w += 16;
205 }
206 mlen += 32 + 1;
207 if (mlen >= 32) {
208 __asm __volatile (
209 "addl %1, %0\n"
210 "adcl %2, %0\n"
211 "adcl %3, %0\n"
212 "adcl %4, %0\n"
213 "adcl %5, %0\n"
214 "adcl %6, %0\n"
215 "adcl %7, %0\n"
216 "adcl %8, %0\n"
217 "adcl $0, %0"
218 : "+r" (sum)
219 : "g" (((const u_int32_t *)w)[4]),
220 "g" (((const u_int32_t *)w)[0]),
221 "g" (((const u_int32_t *)w)[1]),
222 "g" (((const u_int32_t *)w)[2]),
223 "g" (((const u_int32_t *)w)[3]),
224 "g" (((const u_int32_t *)w)[5]),
225 "g" (((const u_int32_t *)w)[6]),
226 "g" (((const u_int32_t *)w)[7])
227 );
228 w += 16;
229 mlen -= 32;
230 }
231 if (mlen >= 16) {
232 __asm __volatile (
233 "addl %1, %0\n"
234 "adcl %2, %0\n"
235 "adcl %3, %0\n"
236 "adcl %4, %0\n"
237 "adcl $0, %0"
238 : "+r" (sum)
239 : "g" (((const u_int32_t *)w)[0]),
240 "g" (((const u_int32_t *)w)[1]),
241 "g" (((const u_int32_t *)w)[2]),
242 "g" (((const u_int32_t *)w)[3])
243 );
244 w += 8;
245 mlen -= 16;
246 }
247 if (mlen >= 8) {
248 __asm __volatile (
249 "addl %1, %0\n"
250 "adcl %2, %0\n"
251 "adcl $0, %0"
252 : "+r" (sum)
253 : "g" (((const u_int32_t *)w)[0]),
254 "g" (((const u_int32_t *)w)[1])
255 );
256 w += 4;
257 mlen -= 8;
258 }
259 if (mlen == 0 && byte_swapped == 0)
260 continue; /* worth 1% maybe ?? */
261 REDUCE;
262 while ((mlen -= 2) >= 0) {
263 sum += *w++;
264 }
265 if (byte_swapped) {
266 sum <<= 8;
267 byte_swapped = 0;
268 if (mlen == -1) {
269 su.c[1] = *(char *)w;
270 sum += su.s;
271 mlen = 0;
272 } else
273 mlen = -1;
274 } else if (mlen == -1)
275 /*
276 * This mbuf has odd number of bytes.
277 * There could be a word split between
278 * this mbuf and the next mbuf.
279 * Save the last byte (to prepend to next mbuf).
280 */
281 su.c[0] = *(char *)w;
282 }
283
284 if (len)
285 printf("%s: out of data by %d\n", __func__, len);
286 if (mlen == -1) {
287 /* The last mbuf has odd # of bytes. Follow the
288 standard (the odd byte is shifted left by 8 bits) */
289 su.c[1] = 0;
290 sum += su.s;
291 }
292 REDUCE;
293 return (~sum & 0xffff);
294 }
295