1 #ifndef _ASM_WORD_AT_A_TIME_H
2 #define _ASM_WORD_AT_A_TIME_H
3 
4 /*
5  * This is largely generic for little-endian machines, but the
6  * optimal byte mask counting is probably going to be something
7  * that is architecture-specific. If you have a reliably fast
8  * bit count instruction, that might be better than the multiply
9  * and shift, for example.
10  */
11 
12 #ifdef CONFIG_64BIT
13 
14 /*
15  * Jan Achrenius on G+: microoptimized version of
16  * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
17  * that works for the bytemasks without having to
18  * mask them first.
19  */
20 static inline long count_masked_bytes(unsigned long mask)
21 {
22 	return mask*0x0001020304050608ul >> 56;
23 }
24 
25 #else	/* 32-bit case */
26 
27 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
28 static inline long count_masked_bytes(long mask)
29 {
30 	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
31 	long a = (0x0ff0001+mask) >> 23;
32 	/* Fix the 1 for 00 case */
33 	return a & mask;
34 }
35 
36 #endif
37 
38 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))
39 
40 /* Return the high bit set in the first byte that is a zero */
41 static inline unsigned long has_zero(unsigned long a)
42 {
43 	return ((a - REPEAT_BYTE(0x01)) & ~a) & REPEAT_BYTE(0x80);
44 }
45 
46 /*
47  * Load an unaligned word from kernel space.
48  *
49  * In the (very unlikely) case of the word being a page-crosser
50  * and the next page not being mapped, take the exception and
51  * return zeroes in the non-existing part.
52  */
53 static inline unsigned long load_unaligned_zeropad(const void *addr)
54 {
55 	unsigned long ret, dummy;
56 
57 	asm(
58 		"1:\tmov %2,%0\n"
59 		"2:\n"
60 		".section .fixup,\"ax\"\n"
61 		"3:\t"
62 		"lea %2,%1\n\t"
63 		"and %3,%1\n\t"
64 		"mov (%1),%0\n\t"
65 		"leal %2,%%ecx\n\t"
66 		"andl %4,%%ecx\n\t"
67 		"shll $3,%%ecx\n\t"
68 		"shr %%cl,%0\n\t"
69 		"jmp 2b\n"
70 		".previous\n"
71 		_ASM_EXTABLE(1b, 3b)
72 		:"=&r" (ret),"=&c" (dummy)
73 		:"m" (*(unsigned long *)addr),
74 		 "i" (-sizeof(unsigned long)),
75 		 "i" (sizeof(unsigned long)-1));
76 	return ret;
77 }
78 
79 #endif /* _ASM_WORD_AT_A_TIME_H */
80