xref: /openbmc/linux/arch/x86/lib/csum-partial_64.c (revision 2f09679b)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * arch/x86_64/lib/csum-partial.c
4  *
5  * This file contains network checksum routines that are better done
6  * in an architecture-specific manner due to speed.
7  */
8 
9 #include <linux/compiler.h>
10 #include <linux/export.h>
11 #include <asm/checksum.h>
12 #include <asm/word-at-a-time.h>
13 
csum_finalize_sum(u64 temp64)14 static inline __wsum csum_finalize_sum(u64 temp64)
15 {
16 	return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
17 }
18 
update_csum_40b(unsigned long sum,const unsigned long m[5])19 static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
20 {
21 	asm("addq %1,%0\n\t"
22 	     "adcq %2,%0\n\t"
23 	     "adcq %3,%0\n\t"
24 	     "adcq %4,%0\n\t"
25 	     "adcq %5,%0\n\t"
26 	     "adcq $0,%0"
27 		:"+r" (sum)
28 		:"m" (m[0]), "m" (m[1]), "m" (m[2]),
29 		 "m" (m[3]), "m" (m[4]));
30 	return sum;
31 }
32 
33 /*
34  * Do a checksum on an arbitrary memory area.
35  * Returns a 32bit checksum.
36  *
37  * This isn't as time critical as it used to be because many NICs
38  * do hardware checksumming these days.
39  *
40  * Still, with CHECKSUM_COMPLETE this is called to compute
41  * checksums on IPv6 headers (40 bytes) and other small parts.
42  * it's best to have buff aligned on a 64-bit boundary
43  */
csum_partial(const void * buff,int len,__wsum sum)44 __wsum csum_partial(const void *buff, int len, __wsum sum)
45 {
46 	u64 temp64 = (__force u64)sum;
47 
48 	/* Do two 40-byte chunks in parallel to get better ILP */
49 	if (likely(len >= 80)) {
50 		u64 temp64_2 = 0;
51 		do {
52 			temp64 = update_csum_40b(temp64, buff);
53 			temp64_2 = update_csum_40b(temp64_2, buff + 40);
54 			buff += 80;
55 			len -= 80;
56 		} while (len >= 80);
57 
58 		asm("addq %1,%0\n\t"
59 		    "adcq $0,%0"
60 		    :"+r" (temp64): "r" (temp64_2));
61 	}
62 
63 	/*
64 	 * len == 40 is the hot case due to IPv6 headers, so return
65 	 * early for that exact case without checking the tail bytes.
66 	 */
67 	if (len >= 40) {
68 		temp64 = update_csum_40b(temp64, buff);
69 		len -= 40;
70 		if (!len)
71 			return csum_finalize_sum(temp64);
72 		buff += 40;
73 	}
74 
75 	if (len & 32) {
76 		asm("addq 0*8(%[src]),%[res]\n\t"
77 		    "adcq 1*8(%[src]),%[res]\n\t"
78 		    "adcq 2*8(%[src]),%[res]\n\t"
79 		    "adcq 3*8(%[src]),%[res]\n\t"
80 		    "adcq $0,%[res]"
81 		    : [res] "+r"(temp64)
82 		    : [src] "r"(buff), "m"(*(const char(*)[32])buff));
83 		buff += 32;
84 	}
85 	if (len & 16) {
86 		asm("addq 0*8(%[src]),%[res]\n\t"
87 		    "adcq 1*8(%[src]),%[res]\n\t"
88 		    "adcq $0,%[res]"
89 		    : [res] "+r"(temp64)
90 		    : [src] "r"(buff), "m"(*(const char(*)[16])buff));
91 		buff += 16;
92 	}
93 	if (len & 8) {
94 		asm("addq 0*8(%[src]),%[res]\n\t"
95 		    "adcq $0,%[res]"
96 		    : [res] "+r"(temp64)
97 		    : [src] "r"(buff), "m"(*(const char(*)[8])buff));
98 		buff += 8;
99 	}
100 	if (len & 7) {
101 		unsigned int shift = (-len << 3) & 63;
102 		unsigned long trail;
103 
104 		trail = (load_unaligned_zeropad(buff) << shift) >> shift;
105 
106 		asm("addq %[trail],%[res]\n\t"
107 		    "adcq $0,%[res]"
108 		    : [res] "+r"(temp64)
109 		    : [trail] "r"(trail));
110 	}
111 	return csum_finalize_sum(temp64);
112 }
113 EXPORT_SYMBOL(csum_partial);
114 
115 /*
116  * this routine is used for miscellaneous IP-like checksums, mainly
117  * in icmp.c
118  */
ip_compute_csum(const void * buff,int len)119 __sum16 ip_compute_csum(const void *buff, int len)
120 {
121 	return csum_fold(csum_partial(buff, len, 0));
122 }
123 EXPORT_SYMBOL(ip_compute_csum);
124