LXR linux/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
  25struct 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
  31static 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
  41static inline unsigned long create_zero_mask(unsigned long bits)
  42{
  43        bits = (bits - 1) & ~bits;
  44        return bits >> 7;
  45}
  46
  47static 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 */
  65static 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 */
  94