1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2019 Facebook
3 #include <features.h>
4 
5 typedef unsigned int u32;
6 
rol32(u32 word,unsigned int shift)7 static __always_inline u32 rol32(u32 word, unsigned int shift)
8 {
9 	return (word << shift) | (word >> ((-shift) & 31));
10 }
11 
12 #define __jhash_mix(a, b, c)			\
13 {						\
14 	a -= c;  a ^= rol32(c, 4);  c += b;	\
15 	b -= a;  b ^= rol32(a, 6);  a += c;	\
16 	c -= b;  c ^= rol32(b, 8);  b += a;	\
17 	a -= c;  a ^= rol32(c, 16); c += b;	\
18 	b -= a;  b ^= rol32(a, 19); a += c;	\
19 	c -= b;  c ^= rol32(b, 4);  b += a;	\
20 }
21 
22 #define __jhash_final(a, b, c)			\
23 {						\
24 	c ^= b; c -= rol32(b, 14);		\
25 	a ^= c; a -= rol32(c, 11);		\
26 	b ^= a; b -= rol32(a, 25);		\
27 	c ^= b; c -= rol32(b, 16);		\
28 	a ^= c; a -= rol32(c, 4);		\
29 	b ^= a; b -= rol32(a, 14);		\
30 	c ^= b; c -= rol32(b, 24);		\
31 }
32 
33 #define JHASH_INITVAL		0xdeadbeef
34 
35 static ATTR
jhash(const void * key,u32 length,u32 initval)36 u32 jhash(const void *key, u32 length, u32 initval)
37 {
38 	u32 a, b, c;
39 	const unsigned char *k = key;
40 
41 	a = b = c = JHASH_INITVAL + length + initval;
42 
43 	while (length > 12) {
44 		a += *(volatile u32 *)(k);
45 		b += *(volatile u32 *)(k + 4);
46 		c += *(volatile u32 *)(k + 8);
47 		__jhash_mix(a, b, c);
48 		length -= 12;
49 		k += 12;
50 	}
51 	switch (length) {
52 	case 12: c += (u32)k[11]<<24;
53 	case 11: c += (u32)k[10]<<16;
54 	case 10: c += (u32)k[9]<<8;
55 	case 9:  c += k[8];
56 	case 8:  b += (u32)k[7]<<24;
57 	case 7:  b += (u32)k[6]<<16;
58 	case 6:  b += (u32)k[5]<<8;
59 	case 5:  b += k[4];
60 	case 4:  a += (u32)k[3]<<24;
61 	case 3:  a += (u32)k[2]<<16;
62 	case 2:  a += (u32)k[1]<<8;
63 	case 1:  a += k[0];
64 		 c ^= a;
65 		 __jhash_final(a, b, c);
66 	case 0: /* Nothing left to add */
67 		break;
68 	}
69 
70 	return c;
71 }
72