1 #ifndef _ASM_WORD_AT_A_TIME_H 2 #define _ASM_WORD_AT_A_TIME_H 3 4 #include <linux/kernel.h> 5 6 /* 7 * This is largely generic for little-endian machines, but the 8 * optimal byte mask counting is probably going to be something 9 * that is architecture-specific. If you have a reliably fast 10 * bit count instruction, that might be better than the multiply 11 * and shift, for example. 12 */ 13 struct word_at_a_time { 14 const unsigned long one_bits, high_bits; 15 }; 16 17 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) } 18 19 #ifdef CONFIG_64BIT 20 21 /* 22 * Jan Achrenius on G+: microoptimized version of 23 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56" 24 * that works for the bytemasks without having to 25 * mask them first. 26 */ 27 static inline long count_masked_bytes(unsigned long mask) 28 { 29 return mask*0x0001020304050608ul >> 56; 30 } 31 32 #else /* 32-bit case */ 33 34 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */ 35 static inline long count_masked_bytes(long mask) 36 { 37 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */ 38 long a = (0x0ff0001+mask) >> 23; 39 /* Fix the 1 for 00 case */ 40 return a & mask; 41 } 42 43 #endif 44 45 /* Return nonzero if it has a zero */ 46 static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c) 47 { 48 unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits; 49 *bits = mask; 50 return mask; 51 } 52 53 static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c) 54 { 55 return bits; 56 } 57 58 static inline unsigned long create_zero_mask(unsigned long bits) 59 { 60 bits = (bits - 1) & ~bits; 61 return bits >> 7; 62 } 63 64 /* The mask we created is directly usable as a bytemask */ 65 #define zero_bytemask(mask) (mask) 66 67 static inline unsigned long find_zero(unsigned long mask) 68 { 69 return count_masked_bytes(mask); 70 } 71 72 /* 73 * Load an unaligned word from kernel space. 74 * 75 * In the (very unlikely) case of the word being a page-crosser 76 * and the next page not being mapped, take the exception and 77 * return zeroes in the non-existing part. 78 */ 79 static inline unsigned long load_unaligned_zeropad(const void *addr) 80 { 81 unsigned long ret, dummy; 82 83 asm( 84 "1:\tmov %2,%0\n" 85 "2:\n" 86 ".section .fixup,\"ax\"\n" 87 "3:\t" 88 "lea %2,%1\n\t" 89 "and %3,%1\n\t" 90 "mov (%1),%0\n\t" 91 "leal %2,%%ecx\n\t" 92 "andl %4,%%ecx\n\t" 93 "shll $3,%%ecx\n\t" 94 "shr %%cl,%0\n\t" 95 "jmp 2b\n" 96 ".previous\n" 97 _ASM_EXTABLE(1b, 3b) 98 :"=&r" (ret),"=&c" (dummy) 99 :"m" (*(unsigned long *)addr), 100 "i" (-sizeof(unsigned long)), 101 "i" (sizeof(unsigned long)-1)); 102 return ret; 103 } 104 105 #endif /* _ASM_WORD_AT_A_TIME_H */ 106