root/arch/arm64/include/asm/word-at-a-time.h

INCLUDED FROM

DEFINITIONS

1. has_zero
2. create_zero_mask
3. find_zero
4. load_unaligned_zeropad

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright (C) 2013 ARM Ltd.
   4  */
   5 #ifndef __ASM_WORD_AT_A_TIME_H
   6 #define __ASM_WORD_AT_A_TIME_H
   7 
   8 #include <linux/uaccess.h>
   9 
  10 #ifndef __AARCH64EB__
  11 
  12 #include <linux/kernel.h>
  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 static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
  21                                      const struct word_at_a_time *c)
  22 {
  23         unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  24         *bits = mask;
  25         return mask;
  26 }
  27 
  28 #define prep_zero_mask(a, bits, c) (bits)
  29 
  30 static inline unsigned long create_zero_mask(unsigned long bits)
  31 {
  32         bits = (bits - 1) & ~bits;
  33         return bits >> 7;
  34 }
  35 
  36 static inline unsigned long find_zero(unsigned long mask)
  37 {
  38         return fls64(mask) >> 3;
  39 }
  40 
  41 #define zero_bytemask(mask) (mask)
  42 
  43 #else   /* __AARCH64EB__ */
  44 #include <asm-generic/word-at-a-time.h>
  45 #endif
  46 
  47 /*
  48  * Load an unaligned word from kernel space.
  49  *
  50  * In the (very unlikely) case of the word being a page-crosser
  51  * and the next page not being mapped, take the exception and
  52  * return zeroes in the non-existing part.
  53  */
  54 static inline unsigned long load_unaligned_zeropad(const void *addr)
  55 {
  56         unsigned long ret, offset;
  57 
  58         /* Load word from unaligned pointer addr */
  59         asm(
  60         "1:     ldr     %0, %3\n"
  61         "2:\n"
  62         "       .pushsection .fixup,\"ax\"\n"
  63         "       .align 2\n"
  64         "3:     and     %1, %2, #0x7\n"
  65         "       bic     %2, %2, #0x7\n"
  66         "       ldr     %0, [%2]\n"
  67         "       lsl     %1, %1, #0x3\n"
  68 #ifndef __AARCH64EB__
  69         "       lsr     %0, %0, %1\n"
  70 #else
  71         "       lsl     %0, %0, %1\n"
  72 #endif
  73         "       b       2b\n"
  74         "       .popsection\n"
  75         _ASM_EXTABLE(1b, 3b)
  76         : "=&r" (ret), "=&r" (offset)
  77         : "r" (addr), "Q" (*(unsigned long *)addr));
  78 
  79         return ret;
  80 }
  81 
  82 #endif /* __ASM_WORD_AT_A_TIME_H */