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/bitops.h>
  12 #include <linux/wordpart.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         unsigned long ret;
  39
  40 #if __LINUX_ARM_ARCH__ >= 5
  41         /* We have clz available. */
  42         ret = fls(mask) >> 3;
  43 #else
  44         /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
  45         ret = (0x0ff0001 + mask) >> 23;
  46         /* Fix the 1 for 00 case */
  47         ret &= mask;
  48 #endif
  49
  50         return ret;
  51 }
  52
  53 #define zero_bytemask(mask) (mask)
  54
  55 #else   /* __ARMEB__ */
  56 #include <asm-generic/word-at-a-time.h>
  57 #endif
  58
  59 #ifdef CONFIG_DCACHE_WORD_ACCESS
  60
  61 /*
  62  * Load an unaligned word from kernel space.
  63  *
  64  * In the (very unlikely) case of the word being a page-crosser
  65  * and the next page not being mapped, take the exception and
  66  * return zeroes in the non-existing part.
  67  */
  68 static inline unsigned long load_unaligned_zeropad(const void *addr)
  69 {
  70         unsigned long ret, offset;
  71
  72         /* Load word from unaligned pointer addr */
  73         asm(
  74         "1:     ldr     %0, [%2]\n"
  75         "2:\n"
  76         "       .pushsection .text.fixup,\"ax\"\n"
  77         "       .align 2\n"
  78         "3:     and     %1, %2, #0x3\n"
  79         "       bic     %2, %2, #0x3\n"
  80         "       ldr     %0, [%2]\n"
  81         "       lsl     %1, %1, #0x3\n"
  82 #ifndef __ARMEB__
  83         "       lsr     %0, %0, %1\n"
  84 #else
  85         "       lsl     %0, %0, %1\n"
  86 #endif
  87         "       b       2b\n"
  88         "       .popsection\n"
  89         "       .pushsection __ex_table,\"a\"\n"
  90         "       .align  3\n"
  91         "       .long   1b, 3b\n"
  92         "       .popsection"
  93         : "=&r" (ret), "=&r" (offset)
  94         : "r" (addr), "Qo" (*(unsigned long *)addr));
  95
  96         return ret;
  97 }
  98
  99 #endif  /* DCACHE_WORD_ACCESS */
 100 #endif /* __ASM_ARM_WORD_AT_A_TIME_H */