cb4ed35612
The C code assumes that the carry bit is always kept from the previous operation. However, the pointer indexing requires another add operation. Thus, the carry bit from the first operation is tromped over by the "addl" operation that ends up following it, so the "adcl" that follows that has no effect because the carry bit is cleared before it. The result is checksum failure on received packets. The larger issue is that there isn't any other way of preventing the compiler inserting arbitrary instructions between different __asm statements (and that the commit message in revision 1.13 of in_cksum.h is wrong on this point). From http://developer.apple.com/documentation/DeveloperTools/gcc-3.3/gcc/Extended-Asm.html ---8<---8<---8<--- You can't expect a sequence of volatile asm instructions to remain perfectly consecutive. If you want consecutive output, use a single asm. Also, GCC will perform some optimizations across a volatile asm instruction; GCC does not "forget everything" when it encounters a volatile asm instruction the way some other compilers do. ---8<---8<---8<--- Also, this change also makes the ASM code much easier to read. PR: 69257 Submitted by: Mike Bristow <mike@urgle.com>, Qing Li <qing.li@bluecoat.com>
131 lines
4.0 KiB
C
131 lines
4.0 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from tahoe: in_cksum.c 1.2 86/01/05
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* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
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* from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
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* $FreeBSD$
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*/
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#ifndef _MACHINE_IN_CKSUM_H_
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#define _MACHINE_IN_CKSUM_H_ 1
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/*
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* MP safe (alfred)
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*/
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#include <sys/cdefs.h>
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#define in_cksum(m, len) in_cksum_skip(m, len, 0)
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/*
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* It it useful to have an Internet checksum routine which is inlineable
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* and optimized specifically for the task of computing IP header checksums
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* in the normal case (where there are no options and the header length is
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* therefore always exactly five 32-bit words.
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*/
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#if defined(__GNUC__) && !defined(__INTEL_COMPILER)
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static __inline u_int
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in_cksum_hdr(const struct ip *ip)
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{
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register u_int sum = 0;
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__asm __volatile (
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"addl %1, %0\n"
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"adcl %2, %0\n"
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"adcl %3, %0\n"
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"adcl %4, %0\n"
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"adcl %5, %0\n"
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"adcl $0, %0"
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: "+r" (sum)
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: "g" (((const u_int32_t *)ip)[0]),
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"g" (((const u_int32_t *)ip)[1]),
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"g" (((const u_int32_t *)ip)[2]),
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"g" (((const u_int32_t *)ip)[3]),
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"g" (((const u_int32_t *)ip)[4])
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);
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sum = (sum & 0xffff) + (sum >> 16);
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if (sum > 0xffff)
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sum -= 0xffff;
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return ~sum & 0xffff;
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}
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static __inline void
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in_cksum_update(struct ip *ip)
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{
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int __tmpsum;
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__tmpsum = (int)ntohs(ip->ip_sum) + 256;
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ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
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}
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static __inline u_short
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in_addword(u_short sum, u_short b)
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{
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/* __volatile is necessary because the condition codes are used. */
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__asm __volatile ("addw %1, %0" : "+r" (sum) : "r" (b));
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__asm __volatile ("adcw $0, %0" : "+r" (sum));
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return (sum);
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}
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static __inline u_short
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in_pseudo(u_int sum, u_int b, u_int c)
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{
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/* __volatile is necessary because the condition codes are used. */
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__asm __volatile ("addl %1, %0" : "+r" (sum) : "g" (b));
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__asm __volatile ("adcl %1, %0" : "+r" (sum) : "g" (c));
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__asm __volatile ("adcl $0, %0" : "+r" (sum));
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sum = (sum & 0xffff) + (sum >> 16);
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if (sum > 0xffff)
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sum -= 0xffff;
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return (sum);
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}
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#else
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#define in_cksum_update(ip) \
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do { \
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int __tmpsum; \
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__tmpsum = (int)ntohs(ip->ip_sum) + 256; \
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ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
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} while(0)
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#endif
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#ifdef _KERNEL
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#if !defined(__GNUC__) || defined(__INTEL_COMPILER)
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u_int in_cksum_hdr(const struct ip *ip);
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u_short in_addword(u_short sum, u_short b);
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u_short in_pseudo(u_int sum, u_int b, u_int c);
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#endif
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u_short in_cksum_skip(struct mbuf *m, int len, int skip);
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#endif /* _KERNEL */
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#endif /* _MACHINE_IN_CKSUM_H_ */
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