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 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT 81 82 static inline unsigned long load_unaligned_zeropad(const void *addr) 83 { 84 unsigned long offset, data; 85 unsigned long ret; 86 87 asm_volatile_goto( 88 "1: mov %[mem], %[ret]\n" 89 90 _ASM_EXTABLE(1b, %l[do_exception]) 91 92 : [ret] "=r" (ret) 93 : [mem] "m" (*(unsigned long *)addr) 94 : : do_exception); 95 96 return ret; 97 98 do_exception: 99 offset = (unsigned long)addr & (sizeof(long) - 1); 100 addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1)); 101 data = *(unsigned long *)addr; 102 ret = data >> offset * 8; 103 104 return ret; 105 } 106 107 #else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ 108 109 static inline unsigned long load_unaligned_zeropad(const void *addr) 110 { 111 unsigned long offset, data; 112 unsigned long ret, err = 0; 113 114 asm( "1: mov %[mem], %[ret]\n" 115 "2:\n" 116 117 _ASM_EXTABLE_FAULT(1b, 2b) 118 119 : [ret] "=&r" (ret), "+a" (err) 120 : [mem] "m" (*(unsigned long *)addr)); 121 122 if (unlikely(err)) { 123 offset = (unsigned long)addr & (sizeof(long) - 1); 124 addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1)); 125 data = *(unsigned long *)addr; 126 ret = data >> offset * 8; 127 } 128 129 return ret; 130 } 131 132 #endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ 133 134 #endif /* _ASM_WORD_AT_A_TIME_H */ 135