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

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