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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2012
*
* Author: Anton Blanchard <anton@au.ibm.com>
*/
#include <asm/ppc_asm.h>
/**
* __clear_user: - Zero a block of memory in user space, with less checking.
* @to: Destination address, in user space.
* @n: Number of bytes to zero.
*
* Zero a block of memory in user space. Caller must check
* the specified block with access_ok() before calling this function.
*
* Returns number of bytes that could not be cleared.
* On success, this will be zero.
*/
.macro err1
100:
.section __ex_table,"a"
.align 3
.llong 100b,.Ldo_err1
.previous
.endm
.macro err2
200:
.section __ex_table,"a"
.align 3
.llong 200b,.Ldo_err2
.previous
.endm
.macro err3
300:
.section __ex_table,"a"
.align 3
.llong 300b,.Ldo_err3
.previous
.endm
.Ldo_err1:
mr r3,r8
.Ldo_err2:
mtctr r4
1:
err3; stb r0,0(r3)
addi r3,r3,1
addi r4,r4,-1
bdnz 1b
.Ldo_err3:
mr r3,r4
blr
_GLOBAL(__clear_user)
cmpdi r4,32
neg r6,r3
li r0,0
blt .Lshort_clear
mr r8,r3
mtocrf 0x01,r6
clrldi r6,r6,(64-3)
/* Get the destination 8 byte aligned */
bf cr7*4+3,1f
err1; stb r0,0(r3)
addi r3,r3,1
1: bf cr7*4+2,2f
err1; sth r0,0(r3)
addi r3,r3,2
2: bf cr7*4+1,3f
err1; stw r0,0(r3)
addi r3,r3,4
3: sub r4,r4,r6
srdi r6,r4,5
cmpdi r4,32
blt .Lshort_clear
mtctr r6
/* Do 32 byte chunks */
4:
err2; std r0,0(r3)
err2; std r0,8(r3)
err2; std r0,16(r3)
err2; std r0,24(r3)
addi r3,r3,32
addi r4,r4,-32
bdnz 4b
.Lshort_clear:
/* up to 31 bytes to go */
cmpdi r4,16
blt 6f
err2; std r0,0(r3)
err2; std r0,8(r3)
addi r3,r3,16
addi r4,r4,-16
/* Up to 15 bytes to go */
6: mr r8,r3
clrldi r4,r4,(64-4)
mtocrf 0x01,r4
bf cr7*4+0,7f
err1; std r0,0(r3)
addi r3,r3,8
7: bf cr7*4+1,8f
err1; stw r0,0(r3)
addi r3,r3,4
8: bf cr7*4+2,9f
err1; sth r0,0(r3)
addi r3,r3,2
9: bf cr7*4+3,10f
err1; stb r0,0(r3)
10: li r3,0
blr
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