1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_WORD_AT_A_TIME_H 3 #define _ASM_WORD_AT_A_TIME_H 4 5 #include <linux/kernel.h> 6 7 /* 8 * This is largely generic for little-endian machines, but the 9 * optimal byte mask counting is probably going to be something 10 * that is architecture-specific. If you have a reliably fast 11 * bit count instruction, that might be better than the multiply 12 * and shift, for example. 13 */ 14 struct word_at_a_time { 15 const unsigned long one_bits, high_bits; 16 }; 17 18 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) } 19 20 #ifdef CONFIG_64BIT 21 22 /* 23 * Jan Achrenius on G+: microoptimized version of 24 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56" 25 * that works for the bytemasks without having to 26 * mask them first. 27 */ 28 static inline long count_masked_bytes(unsigned long mask) 29 { 30 return mask*0x0001020304050608ul >> 56; 31 } 32 33 #else /* 32-bit case */ 34 35 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */ 36 static inline long count_masked_bytes(long mask) 37 { 38 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */ 39 long a = (0x0ff0001+mask) >> 23; 40 /* Fix the 1 for 00 case */ 41 return a & mask; 42 } 43 44 #endif 45 46 /* Return nonzero if it has a zero */ 47 static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c) 48 { 49 unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits; 50 *bits = mask; 51 return mask; 52 } 53 54 static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c) 55 { 56 return bits; 57 } 58 59 static inline unsigned long create_zero_mask(unsigned long bits) 60 { 61 bits = (bits - 1) & ~bits; 62 return bits >> 7; 63 } 64 65 /* The mask we created is directly usable as a bytemask */ 66 #define zero_bytemask(mask) (mask) 67 68 static inline unsigned long find_zero(unsigned long mask) 69 { 70 return count_masked_bytes(mask); 71 } 72 73 /* 74 * Load an unaligned word from kernel space. 75 * 76 * In the (very unlikely) case of the word being a page-crosser 77 * and the next page not being mapped, take the exception and 78 * return zeroes in the non-existing part. 79 */ 80 static inline unsigned long load_unaligned_zeropad(const void *addr) 81 { 82 unsigned long ret, dummy; 83 84 asm( 85 "1:\tmov %2,%0\n" 86 "2:\n" 87 ".section .fixup,\"ax\"\n" 88 "3:\t" 89 "lea %2,%1\n\t" 90 "and %3,%1\n\t" 91 "mov (%1),%0\n\t" 92 "leal %2,%%ecx\n\t" 93 "andl %4,%%ecx\n\t" 94 "shll $3,%%ecx\n\t" 95 "shr %%cl,%0\n\t" 96 "jmp 2b\n" 97 ".previous\n" 98 _ASM_EXTABLE(1b, 3b) 99 :"=&r" (ret),"=&c" (dummy) 100 :"m" (*(unsigned long *)addr), 101 "i" (-sizeof(unsigned long)), 102 "i" (sizeof(unsigned long)-1)); 103 return ret; 104 } 105 106 #endif /* _ASM_WORD_AT_A_TIME_H */ 107