FreeBSD-5.3/sys/i386/i386/in_cksum.c
/*-
* 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.
* 4. 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
* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/i386/i386/in_cksum.c,v 1.27 2004/04/07 20:46:04 imp Exp $");
/*
* MPsafe: alfred
*/
#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
#if !defined(__GNUC__) || defined(__INTEL_COMPILER)
/* non gcc parts stolen from sys/alpha/alpha/in_cksum.c */
#define REDUCE32 \
{ \
q_util.q = sum; \
sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
}
#define REDUCE16 \
{ \
q_util.q = sum; \
l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
sum = l_util.s[0] + l_util.s[1]; \
ADDCARRY(sum); \
}
#endif
#define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
#if !defined(__GNUC__) || defined(__INTEL_COMPILER)
static const u_int32_t in_masks[] = {
/*0 bytes*/ /*1 byte*/ /*2 bytes*/ /*3 bytes*/
0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF, /* offset 0 */
0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00, /* offset 1 */
0x00000000, 0x00FF0000, 0xFFFF0000, 0xFFFF0000, /* offset 2 */
0x00000000, 0xFF000000, 0xFF000000, 0xFF000000, /* offset 3 */
};
union l_util {
u_int16_t s[2];
u_int32_t l;
};
union q_util {
u_int16_t s[4];
u_int32_t l[2];
u_int64_t q;
};
static u_int64_t
in_cksumdata(const u_int32_t *lw, int len)
{
u_int64_t sum = 0;
u_int64_t prefilled;
int offset;
union q_util q_util;
if ((3 & (long) lw) == 0 && len == 20) {
sum = (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3] + lw[4];
REDUCE32;
return sum;
}
if ((offset = 3 & (long) lw) != 0) {
const u_int32_t *masks = in_masks + (offset << 2);
lw = (u_int32_t *) (((long) lw) - offset);
sum = *lw++ & masks[len >= 3 ? 3 : len];
len -= 4 - offset;
if (len <= 0) {
REDUCE32;
return sum;
}
}
#if 0
/*
* Force to cache line boundary.
*/
offset = 32 - (0x1f & (long) lw);
if (offset < 32 && len > offset) {
len -= offset;
if (4 & offset) {
sum += (u_int64_t) lw[0];
lw += 1;
}
if (8 & offset) {
sum += (u_int64_t) lw[0] + lw[1];
lw += 2;
}
if (16 & offset) {
sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
lw += 4;
}
}
#endif
/*
* access prefilling to start load of next cache line.
* then add current cache line
* save result of prefilling for loop iteration.
*/
prefilled = lw[0];
while ((len -= 32) >= 4) {
u_int64_t prefilling = lw[8];
sum += prefilled + lw[1] + lw[2] + lw[3]
+ lw[4] + lw[5] + lw[6] + lw[7];
lw += 8;
prefilled = prefilling;
}
if (len >= 0) {
sum += prefilled + lw[1] + lw[2] + lw[3]
+ lw[4] + lw[5] + lw[6] + lw[7];
lw += 8;
} else {
len += 32;
}
while ((len -= 16) >= 0) {
sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
lw += 4;
}
len += 16;
while ((len -= 4) >= 0) {
sum += (u_int64_t) *lw++;
}
len += 4;
if (len > 0)
sum += (u_int64_t) (in_masks[len] & *lw);
REDUCE32;
return sum;
}
u_short
in_addword(u_short a, u_short b)
{
u_int64_t sum = a + b;
ADDCARRY(sum);
return (sum);
}
u_short
in_pseudo(u_int32_t a, u_int32_t b, u_int32_t c)
{
u_int64_t sum;
union q_util q_util;
union l_util l_util;
sum = (u_int64_t) a + b + c;
REDUCE16;
return (sum);
}
u_short
in_cksum_skip(struct mbuf *m, int len, int skip)
{
u_int64_t sum = 0;
int mlen = 0;
int clen = 0;
caddr_t addr;
union q_util q_util;
union l_util l_util;
len -= skip;
for (; skip && m; m = m->m_next) {
if (m->m_len > skip) {
mlen = m->m_len - skip;
addr = mtod(m, caddr_t) + skip;
goto skip_start;
} else {
skip -= m->m_len;
}
}
for (; m && len; m = m->m_next) {
if (m->m_len == 0)
continue;
mlen = m->m_len;
addr = mtod(m, caddr_t);
skip_start:
if (len < mlen)
mlen = len;
if ((clen ^ (long) addr) & 1)
sum += in_cksumdata((const u_int32_t *)addr, mlen) << 8;
else
sum += in_cksumdata((const u_int32_t *)addr, mlen);
clen += mlen;
len -= mlen;
}
REDUCE16;
return (~sum & 0xffff);
}
u_int in_cksum_hdr(const struct ip *ip)
{
u_int64_t sum = in_cksumdata((const u_int32_t *)ip, sizeof(struct ip));
union q_util q_util;
union l_util l_util;
REDUCE16;
return (~sum & 0xffff);
}
#else
/*
* 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.
*/
#define ADD(n) __asm __volatile \
("addl %1, %0" : "+r" (sum) : \
"g" (((const u_int32_t *)w)[n / 4]))
#define ADDC(n) __asm __volatile \
("adcl %1, %0" : "+r" (sum) : \
"g" (((const u_int32_t *)w)[n / 4]))
#define LOAD(n) __asm __volatile \
("" : : "r" (((const u_int32_t *)w)[n / 4]))
#define MOP __asm __volatile \
("adcl $0, %0" : "+r" (sum))
u_short
in_cksum_skip(m, len, skip)
struct mbuf *m;
int len;
int skip;
{
register u_short *w;
register unsigned sum = 0;
register 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) {
ADD(0);
MOP;
w += 2;
mlen -= 4;
}
if (8 & (int) w && mlen >= 8) {
ADD(0);
ADDC(4);
MOP;
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.
*/
ADD(16);
ADDC(0);
ADDC(4);
ADDC(8);
ADDC(12);
LOAD(32);
ADDC(20);
ADDC(24);
ADDC(28);
MOP;
w += 16;
}
mlen += 32 + 1;
if (mlen >= 32) {
ADD(16);
ADDC(0);
ADDC(4);
ADDC(8);
ADDC(12);
ADDC(20);
ADDC(24);
ADDC(28);
MOP;
w += 16;
mlen -= 32;
}
if (mlen >= 16) {
ADD(0);
ADDC(4);
ADDC(8);
ADDC(12);
MOP;
w += 8;
mlen -= 16;
}
if (mlen >= 8) {
ADD(0);
ADDC(4);
MOP;
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 betwen
* 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);
}
#endif