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