1 /*
2 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA.
18 *
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
22 */
23
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25
26 /** @file
27 *
28 * TCP/IP checksum
29 *
30 */
31
32 #include <limits.h>
33 #include <ipxe/tcpip.h>
34
35 extern char x86_tcpip_loop_end[];
36
37 /**
38 * Calculate continued TCP/IP checkum
39 *
40 * @v partial Checksum of already-summed data, in network byte order
41 * @v data Data buffer
42 * @v len Length of data buffer
43 * @ret cksum Updated checksum, in network byte order
44 */
tcpip_continue_chksum(uint16_t partial,const void * data,size_t len)45 uint16_t tcpip_continue_chksum ( uint16_t partial, const void *data,
46 size_t len ) {
47 unsigned long sum = ( ( ~partial ) & 0xffff );
48 unsigned long initial_word_count;
49 unsigned long loop_count;
50 unsigned long loop_partial_count;
51 unsigned long final_word_count;
52 unsigned long final_byte;
53 unsigned long discard_S;
54 unsigned long discard_c;
55 unsigned long discard_a;
56 unsigned long discard_r1;
57 unsigned long discard_r2;
58
59 /* Calculate number of initial 16-bit words required to bring
60 * the main loop into alignment. (We don't care about the
61 * speed for data aligned to less than 16 bits, since this
62 * situation won't occur in practice.)
63 */
64 if ( len >= sizeof ( sum ) ) {
65 initial_word_count = ( ( -( ( intptr_t ) data ) &
66 ( sizeof ( sum ) - 1 ) ) >> 1 );
67 } else {
68 initial_word_count = 0;
69 }
70 len -= ( initial_word_count * 2 );
71
72 /* Calculate number of iterations of the main loop. This loop
73 * processes native machine words (32-bit or 64-bit), and is
74 * unrolled 16 times. We calculate an overall iteration
75 * count, and a starting point for the first iteration.
76 */
77 loop_count = ( len / ( sizeof ( sum ) * 16 ) );
78 loop_partial_count =
79 ( ( len % ( sizeof ( sum ) * 16 ) ) / sizeof ( sum ) );
80
81 /* Calculate number of 16-bit words remaining after the main
82 * loop completes.
83 */
84 final_word_count = ( ( len % sizeof ( sum ) ) / 2 );
85
86 /* Calculate whether or not a final byte remains at the end */
87 final_byte = ( len & 1 );
88
89 /* Calculate the checksum */
90 __asm__ ( /* Calculate position at which to jump into the
91 * unrolled loop.
92 */
93 "imul $( -x86_tcpip_loop_step_size ), %4\n\t"
94 "add %5, %4\n\t"
95
96 /* Clear carry flag before starting checksumming */
97 "clc\n\t"
98
99 /* Checksum initial words */
100 "jmp 2f\n\t"
101 "\n1:\n\t"
102 "lodsw\n\t"
103 "adcw %w2, %w0\n\t"
104 "\n2:\n\t"
105 "loop 1b\n\t"
106
107 /* Main "lods;adc" loop, unrolled x16 */
108 "mov %12, %3\n\t"
109 "jmp *%4\n\t"
110 "\nx86_tcpip_loop_start:\n\t"
111 "lods%z2\n\tadc %2, %0\n\t"
112 "lods%z2\n\tadc %2, %0\n\t"
113 "lods%z2\n\tadc %2, %0\n\t"
114 "lods%z2\n\tadc %2, %0\n\t"
115 "lods%z2\n\tadc %2, %0\n\t"
116 "lods%z2\n\tadc %2, %0\n\t"
117 "lods%z2\n\tadc %2, %0\n\t"
118 "lods%z2\n\tadc %2, %0\n\t"
119 "lods%z2\n\tadc %2, %0\n\t"
120 "lods%z2\n\tadc %2, %0\n\t"
121 "lods%z2\n\tadc %2, %0\n\t"
122 "lods%z2\n\tadc %2, %0\n\t"
123 "lods%z2\n\tadc %2, %0\n\t"
124 "lods%z2\n\tadc %2, %0\n\t"
125 "lods%z2\n\tadc %2, %0\n\t"
126 "lods%z2\n\tadc %2, %0\n\t"
127 "\nx86_tcpip_loop_end:\n\t"
128 "loop x86_tcpip_loop_start\n\t"
129 ".equ x86_tcpip_loop_step_size, "
130 " ( ( x86_tcpip_loop_end - x86_tcpip_loop_start ) >> 4 )\n\t"
131
132 /* Checksum remaining whole words */
133 "mov %13, %3\n\t"
134 "jmp 2f\n\t"
135 "\n1:\n\t"
136 "lodsw\n\t"
137 "adcw %w2, %w0\n\t"
138 "\n2:\n\t"
139 "loop 1b\n\t"
140
141 /* Checksum final byte if applicable */
142 "mov %14, %3\n\t"
143 "loop 1f\n\t"
144 "adcb (%1), %b0\n\t"
145 "adcb $0, %h0\n\t"
146 "\n1:\n\t"
147
148 /* Fold down to a uint16_t */
149 "push %0\n\t"
150 "popw %w0\n\t"
151 "popw %w2\n\t"
152 "adcw %w2, %w0\n\t"
153 #if ULONG_MAX > 0xffffffffUL /* 64-bit only */
154 "popw %w2\n\t"
155 "adcw %w2, %w0\n\t"
156 "popw %w2\n\t"
157 "adcw %w2, %w0\n\t"
158 #endif /* 64-bit only */
159
160 /* Consume CF */
161 "adcw $0, %w0\n\t"
162 "adcw $0, %w0\n\t"
163
164 : "=&Q" ( sum ), "=&S" ( discard_S ), "=&a" ( discard_a ),
165 "=&c" ( discard_c ), "=&r" ( discard_r1 ),
166 "=&r" ( discard_r2 )
167 : "0" ( sum ), "1" ( data ), "2" ( 0 ),
168 "3" ( initial_word_count + 1 ), "4" ( loop_partial_count ),
169 "5" ( x86_tcpip_loop_end ), "g" ( loop_count + 1 ),
170 "g" ( final_word_count + 1 ), "g" ( final_byte ) );
171
172 return ( ~sum & 0xffff );
173 }
174