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

   1 /*
   2  * Copyright (C) 2013 ARM Ltd.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15  */
  16 #ifndef __ASM_WORD_AT_A_TIME_H
  17 #define __ASM_WORD_AT_A_TIME_H
  18
  19 #include <linux/uaccess.h>
  20
  21 #ifndef __AARCH64EB__
  22
  23 #include <linux/kernel.h>
  24
  25 struct word_at_a_time {
  26         const unsigned long one_bits, high_bits;
  27 };
  28
  29 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
  30
  31 static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
  32                                      const struct word_at_a_time *c)
  33 {
  34         unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  35         *bits = mask;
  36         return mask;
  37 }
  38
  39 #define prep_zero_mask(a, bits, c) (bits)
  40
  41 static inline unsigned long create_zero_mask(unsigned long bits)
  42 {
  43         bits = (bits - 1) & ~bits;
  44         return bits >> 7;
  45 }
  46
  47 static inline unsigned long find_zero(unsigned long mask)
  48 {
  49         return fls64(mask) >> 3;
  50 }
  51
  52 #define zero_bytemask(mask) (mask)
  53
  54 #else   /* __AARCH64EB__ */
  55 #include <asm-generic/word-at-a-time.h>
  56 #endif
  57
  58 /*
  59  * Load an unaligned word from kernel space.
  60  *
  61  * In the (very unlikely) case of the word being a page-crosser
  62  * and the next page not being mapped, take the exception and
  63  * return zeroes in the non-existing part.
  64  */
  65 static inline unsigned long load_unaligned_zeropad(const void *addr)
  66 {
  67         unsigned long ret, offset;
  68
  69         /* Load word from unaligned pointer addr */
  70         asm(
  71         "1:     ldr     %0, %3\n"
  72         "2:\n"
  73         "       .pushsection .fixup,\"ax\"\n"
  74         "       .align 2\n"
  75         "3:     and     %1, %2, #0x7\n"
  76         "       bic     %2, %2, #0x7\n"
  77         "       ldr     %0, [%2]\n"
  78         "       lsl     %1, %1, #0x3\n"
  79 #ifndef __AARCH64EB__
  80         "       lsr     %0, %0, %1\n"
  81 #else
  82         "       lsl     %0, %0, %1\n"
  83 #endif
  84         "       b       2b\n"
  85         "       .popsection\n"
  86         _ASM_EXTABLE(1b, 3b)
  87         : "=&r" (ret), "=&r" (offset)
  88         : "r" (addr), "Q" (*(unsigned long *)addr));
  89
  90         return ret;
  91 }
  92
  93 #endif /* __ASM_WORD_AT_A_TIME_H */