Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * arch/x86_64/lib/csum-partial.c | |
3 | * | |
4 | * This file contains network checksum routines that are better done | |
5 | * in an architecture-specific manner due to speed. | |
6 | */ | |
7 | ||
8 | #include <linux/compiler.h> | |
9 | #include <linux/module.h> | |
10 | #include <asm/checksum.h> | |
11 | ||
1da177e4 LT |
12 | static inline unsigned short from32to16(unsigned a) |
13 | { | |
14 | unsigned short b = a >> 16; | |
15 | asm("addw %w2,%w0\n\t" | |
16 | "adcw $0,%w0\n" | |
17 | : "=r" (b) | |
18 | : "0" (b), "r" (a)); | |
19 | return b; | |
20 | } | |
21 | ||
22 | /* | |
23 | * Do a 64-bit checksum on an arbitrary memory area. | |
24 | * Returns a 32bit checksum. | |
25 | * | |
26 | * This isn't as time critical as it used to be because many NICs | |
27 | * do hardware checksumming these days. | |
28 | * | |
29 | * Things tried and found to not make it faster: | |
30 | * Manual Prefetching | |
31 | * Unrolling to an 128 bytes inner loop. | |
32 | * Using interleaving with more registers to break the carry chains. | |
33 | */ | |
b6bcc4bb | 34 | static unsigned do_csum(const unsigned char *buff, unsigned len) |
1da177e4 LT |
35 | { |
36 | unsigned odd, count; | |
37 | unsigned long result = 0; | |
38 | ||
39 | if (unlikely(len == 0)) | |
40 | return result; | |
41 | odd = 1 & (unsigned long) buff; | |
42 | if (unlikely(odd)) { | |
43 | result = *buff << 8; | |
44 | len--; | |
45 | buff++; | |
46 | } | |
47 | count = len >> 1; /* nr of 16-bit words.. */ | |
48 | if (count) { | |
49 | if (2 & (unsigned long) buff) { | |
50 | result += *(unsigned short *)buff; | |
51 | count--; | |
52 | len -= 2; | |
53 | buff += 2; | |
54 | } | |
55 | count >>= 1; /* nr of 32-bit words.. */ | |
56 | if (count) { | |
57 | unsigned long zero; | |
58 | unsigned count64; | |
59 | if (4 & (unsigned long) buff) { | |
60 | result += *(unsigned int *) buff; | |
61 | count--; | |
62 | len -= 4; | |
63 | buff += 4; | |
64 | } | |
65 | count >>= 1; /* nr of 64-bit words.. */ | |
66 | ||
67 | /* main loop using 64byte blocks */ | |
68 | zero = 0; | |
69 | count64 = count >> 3; | |
70 | while (count64) { | |
71 | asm("addq 0*8(%[src]),%[res]\n\t" | |
72 | "adcq 1*8(%[src]),%[res]\n\t" | |
73 | "adcq 2*8(%[src]),%[res]\n\t" | |
74 | "adcq 3*8(%[src]),%[res]\n\t" | |
75 | "adcq 4*8(%[src]),%[res]\n\t" | |
76 | "adcq 5*8(%[src]),%[res]\n\t" | |
77 | "adcq 6*8(%[src]),%[res]\n\t" | |
78 | "adcq 7*8(%[src]),%[res]\n\t" | |
79 | "adcq %[zero],%[res]" | |
80 | : [res] "=r" (result) | |
81 | : [src] "r" (buff), [zero] "r" (zero), | |
82 | "[res]" (result)); | |
83 | buff += 64; | |
84 | count64--; | |
85 | } | |
86 | ||
0d2eb44f | 87 | /* last up to 7 8byte blocks */ |
1da177e4 LT |
88 | count %= 8; |
89 | while (count) { | |
90 | asm("addq %1,%0\n\t" | |
91 | "adcq %2,%0\n" | |
92 | : "=r" (result) | |
93 | : "m" (*(unsigned long *)buff), | |
94 | "r" (zero), "0" (result)); | |
95 | --count; | |
96 | buff += 8; | |
97 | } | |
98 | result = add32_with_carry(result>>32, | |
99 | result&0xffffffff); | |
100 | ||
101 | if (len & 4) { | |
102 | result += *(unsigned int *) buff; | |
103 | buff += 4; | |
104 | } | |
105 | } | |
106 | if (len & 2) { | |
107 | result += *(unsigned short *) buff; | |
108 | buff += 2; | |
109 | } | |
110 | } | |
111 | if (len & 1) | |
112 | result += *buff; | |
113 | result = add32_with_carry(result>>32, result & 0xffffffff); | |
114 | if (unlikely(odd)) { | |
115 | result = from32to16(result); | |
116 | result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); | |
117 | } | |
118 | return result; | |
119 | } | |
120 | ||
121 | /* | |
122 | * computes the checksum of a memory block at buff, length len, | |
123 | * and adds in "sum" (32-bit) | |
124 | * | |
125 | * returns a 32-bit number suitable for feeding into itself | |
126 | * or csum_tcpudp_magic | |
127 | * | |
128 | * this function must be called with even lengths, except | |
129 | * for the last fragment, which may be odd | |
130 | * | |
131 | * it's best to have buff aligned on a 64-bit boundary | |
132 | */ | |
a4f89fb7 | 133 | __wsum csum_partial(const void *buff, int len, __wsum sum) |
1da177e4 | 134 | { |
a4f89fb7 AV |
135 | return (__force __wsum)add32_with_carry(do_csum(buff, len), |
136 | (__force u32)sum); | |
1da177e4 LT |
137 | } |
138 | ||
1da177e4 LT |
139 | /* |
140 | * this routine is used for miscellaneous IP-like checksums, mainly | |
141 | * in icmp.c | |
142 | */ | |
a4f89fb7 | 143 | __sum16 ip_compute_csum(const void *buff, int len) |
1da177e4 LT |
144 | { |
145 | return csum_fold(csum_partial(buff,len,0)); | |
146 | } | |
2ee60e17 | 147 | EXPORT_SYMBOL(ip_compute_csum); |
1da177e4 | 148 |