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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | /* * INET An implementation of the TCP/IP protocol suite for the LINUX * operating system. INET is implemented using the BSD Socket * interface as the means of communication with the user level. * * MIPS specific IP/TCP/UDP checksumming routines * * Authors: Ralf Baechle, <ralf@waldorf-gmbh.de> * Lots of code moved from tcp.c and ip.c; see those files * for more names. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <net/checksum.h> #include <asm/string.h> /* * computes a partial checksum, e.g. for TCP/UDP fragments */ unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum) { unsigned long scratch1; unsigned long scratch2; /* * The GCC generated code for handling carry bits makes * it strongly desireable to do this in assembler! */ __asm__(" .set noreorder .set noat andi $1,%5,2 # Check alignment beqz $1,2f # Branch if ok subu $1,%4,2 # delay slot, Alignment uses up two bytes bgez $1,1f # Jump if we had at least two bytes move %4,$1 # delay slot j 4f addiu %4,2 # delay slot; len was < 2. Deal with it 1: lw %2,(%5) addiu %4,2 addu %0,%2 sltu $1,%0,%2 addu %0,$1 2: move %1,%4 srl %1,%1,5 beqz %1,2f sll %1,%1,5 # delay slot addu %1,%5 1: lw %2,0(%5) addu %5,32 addu %0,%2 sltu $1,%0,%2 lw %2,-28(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-24(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-20(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-16(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-12(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-8(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 lw %2,-4(%5) addu %0,$1 addu %0,%2 sltu $1,%0,%2 bne %5,%1,1b addu %0,$1 # delay slot 2: andi %1,%4,0x1c srl %1,%1,2 beqz %1,4f addu %1,%5 # delay slot 3: lw %2,0(%5) addu %5,4 addu %0,%2 sltu $1,%0,%2 bne %5,%1,3b addu %0,$1 # delay slot 4: andi $1,%3,2 beqz $1,5f move %2,$0 # delay slot lhu %2,(%5) addiu %5,2 5: andi $1,%3,1 beqz $1,6f sll %1,16 # delay slot lbu %1,(%5) nop # NOP ALERT (spit, gasp) 6: or %2,%1 addu %0,%2 sltu $1,%0,%2 addu %0,$1 7: .set at .set reorder" : "=r"(sum), "=r" (scratch1), "=r" (scratch2) : "0"(sum), "r"(len), "r"(buff) : "$1"); return sum; } /* * copy from fs while checksumming, otherwise like csum_partial */ unsigned int csum_partial_copy(const char *src, char *dst, int len, int sum) { /* * It's 2:30 am and I don't feel like doing it real ... * This is lots slower than the real thing (tm) */ sum = csum_partial(src, len, sum); memcpy(dst, src, len); return sum; } |