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
  13 struct 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
  19 static 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
  29 static inline unsigned long create_zero_mask(unsigned long bits)
  30 {
  31         bits = (bits - 1) & ~bits;
  32         return bits >> 7;
  33 }
  34
  35 static 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  */
  67 static 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 */