root/arch/nds32/lib/clear_user.S

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2005-2017 Andes Technology Corporation
   3 
   4 #include <linux/linkage.h>
   5 #include <asm/assembler.h>
   6 #include <asm/errno.h>
   7 
   8 /* Prototype: int __arch_clear_user(void *addr, size_t sz)
   9  * Purpose  : clear some user memory
  10  * Params   : addr - user memory address to clear
  11  *          : sz   - number of bytes to clear
  12  * Returns  : number of bytes NOT cleared
  13  */
  14         .text
  15         .align  5
  16 ENTRY(__arch_clear_user)
  17         add     $r5, $r0, $r1
  18         beqz    $r1, clear_exit
  19         xor     $p1, $p1, $p1           ! Use $p1=0 to clear mem
  20         srli    $p0, $r1, #2            ! $p0 = number of word to clear
  21         andi    $r1, $r1, #3            ! Bytes less than a word to copy
  22         beqz    $p0, byte_clear         ! Only less than a word to clear
  23 word_clear:
  24 USER(   smw.bim,$p1, [$r0], $p1)        ! Clear the word
  25         addi    $p0, $p0, #-1           ! Decrease word count
  26         bnez    $p0, word_clear         ! Continue looping to clear all words
  27         beqz    $r1, clear_exit         ! No left bytes to copy
  28 byte_clear:
  29 USER(   sbi.bi, $p1, [$r0], #1)         ! Clear the byte
  30         addi    $r1, $r1, #-1           ! Decrease byte count
  31         bnez    $r1, byte_clear         ! Continue looping to clear all left bytes
  32 clear_exit:
  33         move    $r0, $r1                ! Set return value
  34         ret
  35 
  36         .section .fixup,"ax"
  37         .align  0
  38 9001:
  39         sub     $r0, $r5, $r0           ! Bytes left to copy
  40         ret
  41         .previous
  42 ENDPROC(__arch_clear_user)