/*- * SPDX-License-Identifier: BSD-3-Clause * * Copyright (c) 1990 The Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * from tahoe: in_cksum.c 1.2 86/01/05 */ #include <sys/param.h> #include <sys/systm.h> #include <sys/mbuf.h> #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #include <machine/in_cksum.h> /* * Checksum routine for Internet Protocol family headers. * * This routine is very heavily used in the network * code and should be modified for each CPU to be as fast as possible. * * This implementation is 386 version. */ #undef ADDCARRY #define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff #define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);} /* * These asm statements require __volatile because they pass information * via the condition codes. GCC does not currently provide a way to specify * the condition codes as an input or output operand. * * The LOAD macro below is effectively a prefetch into cache. GCC will * load the value into a register but will not use it. Since modern CPUs * reorder operations, this will generally take place in parallel with * other calculations. */ u_short in_cksum_skip(struct mbuf *m, int len, int skip) { u_short *w; unsigned sum = 0; int mlen = 0; int byte_swapped = 0; union { char c[2]; u_short s; } su; len -= skip; for (; skip && m; m = m->m_next) { if (m->m_len > skip) { mlen = m->m_len - skip; w = (u_short *)(mtod(m, u_char *) + skip); goto skip_start; } else { skip -= m->m_len; } } for (; m && len; m = m->m_next) { if (m->m_len == 0) continue; w = mtod(m, u_short *); if (mlen == -1) { /* * The first byte of this mbuf is the continuation * of a word spanning between this mbuf and the * last mbuf. */ /* su.c[0] is already saved when scanning previous * mbuf. sum was REDUCEd when we found mlen == -1 */ su.c[1] = *(u_char *)w; sum += su.s; w = (u_short *)((char *)w + 1); mlen = m->m_len - 1; len--; } else mlen = m->m_len; skip_start: if (len < mlen) mlen = len; len -= mlen; /* * Force to long boundary so we do longword aligned * memory operations */ if (3 & (int) w) { REDUCE; if ((1 & (int) w) && (mlen > 0)) { sum <<= 8; su.c[0] = *(char *)w; w = (u_short *)((char *)w + 1); mlen--; byte_swapped = 1; } if ((2 & (int) w) && (mlen >= 2)) { sum += *w++; mlen -= 2; } } /* * Advance to a 486 cache line boundary. */ if (4 & (int) w && mlen >= 4) { __asm __volatile ( "addl %1, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[0]) ); w += 2; mlen -= 4; } if (8 & (int) w && mlen >= 8) { __asm __volatile ( "addl %1, %0\n" "adcl %2, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[0]), "g" (((const u_int32_t *)w)[1]) ); w += 4; mlen -= 8; } /* * Do as much of the checksum as possible 32 bits at at time. * In fact, this loop is unrolled to make overhead from * branches &c small. */ mlen -= 1; while ((mlen -= 32) >= 0) { /* * Add with carry 16 words and fold in the last * carry by adding a 0 with carry. * * The early ADD(16) and the LOAD(32) are to load * the next 2 cache lines in advance on 486's. The * 486 has a penalty of 2 clock cycles for loading * a cache line, plus whatever time the external * memory takes to load the first word(s) addressed. * These penalties are unavoidable. Subsequent * accesses to a cache line being loaded (and to * other external memory?) are delayed until the * whole load finishes. These penalties are mostly * avoided by not accessing external memory for * 8 cycles after the ADD(16) and 12 cycles after * the LOAD(32). The loop terminates when mlen * is initially 33 (not 32) to guaranteed that * the LOAD(32) is within bounds. */ __asm __volatile ( "addl %1, %0\n" "adcl %2, %0\n" "adcl %3, %0\n" "adcl %4, %0\n" "adcl %5, %0\n" "mov %6, %%eax\n" "adcl %7, %0\n" "adcl %8, %0\n" "adcl %9, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[4]), "g" (((const u_int32_t *)w)[0]), "g" (((const u_int32_t *)w)[1]), "g" (((const u_int32_t *)w)[2]), "g" (((const u_int32_t *)w)[3]), "g" (((const u_int32_t *)w)[8]), "g" (((const u_int32_t *)w)[5]), "g" (((const u_int32_t *)w)[6]), "g" (((const u_int32_t *)w)[7]) : "eax" ); w += 16; } mlen += 32 + 1; if (mlen >= 32) { __asm __volatile ( "addl %1, %0\n" "adcl %2, %0\n" "adcl %3, %0\n" "adcl %4, %0\n" "adcl %5, %0\n" "adcl %6, %0\n" "adcl %7, %0\n" "adcl %8, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[4]), "g" (((const u_int32_t *)w)[0]), "g" (((const u_int32_t *)w)[1]), "g" (((const u_int32_t *)w)[2]), "g" (((const u_int32_t *)w)[3]), "g" (((const u_int32_t *)w)[5]), "g" (((const u_int32_t *)w)[6]), "g" (((const u_int32_t *)w)[7]) ); w += 16; mlen -= 32; } if (mlen >= 16) { __asm __volatile ( "addl %1, %0\n" "adcl %2, %0\n" "adcl %3, %0\n" "adcl %4, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[0]), "g" (((const u_int32_t *)w)[1]), "g" (((const u_int32_t *)w)[2]), "g" (((const u_int32_t *)w)[3]) ); w += 8; mlen -= 16; } if (mlen >= 8) { __asm __volatile ( "addl %1, %0\n" "adcl %2, %0\n" "adcl $0, %0" : "+r" (sum) : "g" (((const u_int32_t *)w)[0]), "g" (((const u_int32_t *)w)[1]) ); w += 4; mlen -= 8; } if (mlen == 0 && byte_swapped == 0) continue; /* worth 1% maybe ?? */ REDUCE; while ((mlen -= 2) >= 0) { sum += *w++; } if (byte_swapped) { sum <<= 8; byte_swapped = 0; if (mlen == -1) { su.c[1] = *(char *)w; sum += su.s; mlen = 0; } else mlen = -1; } else if (mlen == -1) /* * This mbuf has odd number of bytes. * There could be a word split between * this mbuf and the next mbuf. * Save the last byte (to prepend to next mbuf). */ su.c[0] = *(char *)w; } if (len) printf("%s: out of data by %d\n", __func__, len); if (mlen == -1) { /* The last mbuf has odd # of bytes. Follow the standard (the odd byte is shifted left by 8 bits) */ su.c[1] = 0; sum += su.s; } REDUCE; return (~sum & 0xffff); }
