LXR linux/arch/arm/include/asm/word-at-a-time.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef __ASM_ARM_WORD_AT_A_TIME_H
   3#define __ASM_ARM_WORD_AT_A_TIME_H
   4
   5#ifndef __ARMEB__
   6
   7/*
   8 * Little-endian word-at-a-time zero byte handling.
   9 * Heavily based on the x86 algorithm.
  10 */
  11#include <linux/kernel.h>
  12
  13struct word_at_a_time {
  14        const unsigned long one_bits, high_bits;
  15};
  16
  17#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
  18
  19static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
  20                                     const struct word_at_a_time *c)
  21{
  22        unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  23        *bits = mask;
  24        return mask;
  25}
  26
  27#define prep_zero_mask(a, bits, c) (bits)
  28
  29static inline unsigned long create_zero_mask(unsigned long bits)
  30{
  31        bits = (bits - 1) & ~bits;
  32        return bits >> 7;
  33}
  34
  35static inline unsigned long find_zero(unsigned long mask)
  36{
  37        unsigned long ret;
  38
  39#if __LINUX_ARM_ARCH__ >= 5
  40        /* We have clz available. */
  41        ret = fls(mask) >> 3;
  42#else
  43        /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
  44        ret = (0x0ff0001 + mask) >> 23;
  45        /* Fix the 1 for 00 case */
  46        ret &= mask;
  47#endif
  48
  49        return ret;
  50}
  51
  52#define zero_bytemask(mask) (mask)
  53
  54#else   /* __ARMEB__ */
  55#include <asm-generic/word-at-a-time.h>
  56#endif
  57
  58#ifdef CONFIG_DCACHE_WORD_ACCESS
  59
  60/*
  61 * Load an unaligned word from kernel space.
  62 *
  63 * In the (very unlikely) case of the word being a page-crosser
  64 * and the next page not being mapped, take the exception and
  65 * return zeroes in the non-existing part.
  66 */
  67static inline unsigned long load_unaligned_zeropad(const void *addr)
  68{
  69        unsigned long ret, offset;
  70
  71        /* Load word from unaligned pointer addr */
  72        asm(
  73        "1:     ldr     %0, [%2]\n"
  74        "2:\n"
  75        "       .pushsection .text.fixup,\"ax\"\n"
  76        "       .align 2\n"
  77        "3:     and     %1, %2, #0x3\n"
  78        "       bic     %2, %2, #0x3\n"
  79        "       ldr     %0, [%2]\n"
  80        "       lsl     %1, %1, #0x3\n"
  81#ifndef __ARMEB__
  82        "       lsr     %0, %0, %1\n"
  83#else
  84        "       lsl     %0, %0, %1\n"
  85#endif
  86        "       b       2b\n"
  87        "       .popsection\n"
  88        "       .pushsection __ex_table,\"a\"\n"
  89        "       .align  3\n"
  90        "       .long   1b, 3b\n"
  91        "       .popsection"
  92        : "=&r" (ret), "=&r" (offset)
  93        : "r" (addr), "Qo" (*(unsigned long *)addr));
  94
  95        return ret;
  96}
  97
  98#endif  /* DCACHE_WORD_ACCESS */
  99#endif /* __ASM_ARM_WORD_AT_A_TIME_H */
 100