root/arch/alpha/lib/strncpy.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * arch/alpha/lib/strncpy.S
   4  * Contributed by Richard Henderson (rth@tamu.edu)
   5  *
   6  * Copy no more than COUNT bytes of the null-terminated string from
   7  * SRC to DST.  If SRC does not cover all of COUNT, the balance is
   8  * zeroed.
   9  *
  10  * Or, rather, if the kernel cared about that weird ANSI quirk.  This
  11  * version has cropped that bit o' nastiness as well as assuming that
  12  * __stxncpy is in range of a branch.
  13  */
  14 #include <asm/export.h>
  15         .set noat
  16         .set noreorder
  17 
  18         .text
  19 
  20         .align 4
  21         .globl strncpy
  22         .ent strncpy
  23 strncpy:
  24         .frame $30, 0, $26
  25         .prologue 0
  26 
  27         mov     $16, $0         # set return value now
  28         beq     $18, $zerolen
  29         unop
  30         bsr     $23, __stxncpy  # do the work of the copy
  31 
  32         unop
  33         bne     $18, $multiword # do we have full words left?
  34         subq    $24, 1, $3      # nope
  35         subq    $27, 1, $4
  36 
  37         or      $3, $24, $3     # clear the bits between the last
  38         or      $4, $27, $4     # written byte and the last byte in COUNT
  39         andnot  $3, $4, $4
  40         zap     $1, $4, $1
  41 
  42         stq_u   $1, 0($16)
  43         ret
  44 
  45         .align  4
  46 $multiword:
  47         subq    $27, 1, $2      # clear the final bits in the prev word
  48         or      $2, $27, $2
  49         zapnot  $1, $2, $1
  50         subq    $18, 1, $18
  51 
  52         stq_u   $1, 0($16)
  53         addq    $16, 8, $16
  54         unop
  55         beq     $18, 1f
  56 
  57         nop
  58         unop
  59         nop
  60         blbc    $18, 0f
  61 
  62         stq_u   $31, 0($16)     # zero one word
  63         subq    $18, 1, $18
  64         addq    $16, 8, $16
  65         beq     $18, 1f
  66 
  67 0:      stq_u   $31, 0($16)     # zero two words
  68         subq    $18, 2, $18
  69         stq_u   $31, 8($16)
  70         addq    $16, 16, $16
  71         bne     $18, 0b
  72 
  73 1:      ldq_u   $1, 0($16)      # clear the leading bits in the final word
  74         subq    $24, 1, $2
  75         or      $2, $24, $2
  76 
  77         zap     $1, $2, $1
  78         stq_u   $1, 0($16)
  79 $zerolen:
  80         ret
  81 
  82         .end    strncpy
  83         EXPORT_SYMBOL(strncpy)