LXR linux/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
  23strncpy:
  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
  670:      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
  731:      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)
  84