1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * MIPS specific IP/TCP/UDP checksumming routines
8 *
9 * Authors: Ralf Baechle, <ralf@waldorf-gmbh.de>
10 * Lots of code moved from tcp.c and ip.c; see those files
11 * for more names.
12 */
13 #include <linux/module.h>
14 #include <linux/types.h>
15
16 #include <net/checksum.h>
17 #include <asm/byteorder.h>
18 #include <asm/string.h>
19 #include <linux/uaccess.h>
20
21 #define addc(_t,_r) \
22 __asm__ __volatile__ ( \
23 " add %0, %1, %0\n" \
24 " addc %0, %%r0, %0\n" \
25 : "=r"(_t) \
26 : "r"(_r), ""(_t));
27
28 static inline unsigned short from32to16(unsigned int x)
29 {
30 /* 32 bits --> 16 bits + carry */
31 x = (x & 0xffff) + (x >> 16);
32 /* 16 bits + carry --> 16 bits including carry */
33 x = (x & 0xffff) + (x >> 16);
34 return (unsigned short)x;
35 }
36
37 static inline unsigned int do_csum(const unsigned char * buff, int len)
38 {
39 int odd, count;
40 unsigned int result = 0;
41
42 if (len <= 0)
43 goto out;
44 odd = 1 & (unsigned long) buff;
45 if (odd) {
46 result = be16_to_cpu(*buff);
47 len--;
48 buff++;
49 }
50 count = len >> 1; /* nr of 16-bit words.. */
51 if (count) {
52 if (2 & (unsigned long) buff) {
53 result += *(unsigned short *) buff;
54 count--;
55 len -= 2;
56 buff += 2;
57 }
58 count >>= 1; /* nr of 32-bit words.. */
59 if (count) {
60 while (count >= 4) {
61 unsigned int r1, r2, r3, r4;
62 r1 = *(unsigned int *)(buff + 0);
63 r2 = *(unsigned int *)(buff + 4);
64 r3 = *(unsigned int *)(buff + 8);
65 r4 = *(unsigned int *)(buff + 12);
66 addc(result, r1);
67 addc(result, r2);
68 addc(result, r3);
69 addc(result, r4);
70 count -= 4;
71 buff += 16;
72 }
73 while (count) {
74 unsigned int w = *(unsigned int *) buff;
75 count--;
76 buff += 4;
77 addc(result, w);
78 }
79 result = (result & 0xffff) + (result >> 16);
80 }
81 if (len & 2) {
82 result += *(unsigned short *) buff;
83 buff += 2;
84 }
85 }
86 if (len & 1)
87 result += le16_to_cpu(*buff);
88 result = from32to16(result);
89 if (odd)
90 result = swab16(result);
91 out:
92 return result;
93 }
94
95 /*
96 * computes a partial checksum, e.g. for TCP/UDP fragments
97 */
98 /*
99 * why bother folding?
100 */
101 __wsum csum_partial(const void *buff, int len, __wsum sum)
102 {
103 unsigned int result = do_csum(buff, len);
104 addc(result, sum);
105 return (__force __wsum)from32to16(result);
106 }
107
108 EXPORT_SYMBOL(csum_partial);
109
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