/* SPDX-License-Identifier: GPL-2.0 */
/*
 * arch/alpha/lib/strncpy.S
 * Contributed by Richard Henderson (rth@tamu.edu)
 *
 * Copy no more than COUNT bytes of the null-terminated string from
 * SRC to DST.  If SRC does not cover all of COUNT, the balance is
 * zeroed.
 *
 * Or, rather, if the kernel cared about that weird ANSI quirk.  This
 * version has cropped that bit o' nastiness as well as assuming that
 * __stxncpy is in range of a branch.
 */
#include <linux/export.h>
        .set noat
        .set noreorder

        .text

        .align 4
        .globl strncpy
        .ent strncpy
strncpy:
        .frame $30, 0, $26
        .prologue 0

        mov     $16, $0         # set return value now
        beq     $18, $zerolen
        unop
        bsr     $23, __stxncpy  # do the work of the copy

        unop
        bne     $18, $multiword # do we have full words left?
        subq    $24, 1, $3      # nope
        subq    $27, 1, $4

        or      $3, $24, $3     # clear the bits between the last
        or      $4, $27, $4     # written byte and the last byte in COUNT
        andnot  $3, $4, $4
        zap     $1, $4, $1

        stq_u   $1, 0($16)
        ret

        .align  4
$multiword:
        subq    $27, 1, $2      # clear the final bits in the prev word
        or      $2, $27, $2
        zapnot  $1, $2, $1
        subq    $18, 1, $18

        stq_u   $1, 0($16)
        addq    $16, 8, $16
        unop
        beq     $18, 1f

        nop
        unop
        nop
        blbc    $18, 0f

        stq_u   $31, 0($16)     # zero one word
        subq    $18, 1, $18
        addq    $16, 8, $16
        beq     $18, 1f

0:      stq_u   $31, 0($16)     # zero two words
        subq    $18, 2, $18
        stq_u   $31, 8($16)
        addq    $16, 16, $16
        bne     $18, 0b

1:      ldq_u   $1, 0($16)      # clear the leading bits in the final word
        subq    $24, 1, $2
        or      $2, $24, $2

        zap     $1, $2, $1
        stq_u   $1, 0($16)
$zerolen:
        ret

        .end    strncpy
        EXPORT_SYMBOL(strncpy)