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/*
* Based on arch/arm/lib/clear_user.S
*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 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, see <http://www.gnu.org/licenses/>.
*/
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
.text
/* Prototype: int __clear_user(void *addr, size_t sz)
* Purpose : clear some user memory
* Params : addr - user memory address to clear
* : sz - number of bytes to clear
* Returns : number of bytes NOT cleared
*
* Alignment fixed up by hardware.
*/
ENTRY(__clear_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN)
mov x2, x1 // save the size for fixup return
subs x1, x1, #8
b.mi 2f
1:
USER(9f, str xzr, [x0], #8 )
subs x1, x1, #8
b.pl 1b
2: adds x1, x1, #4
b.mi 3f
USER(9f, str wzr, [x0], #4 )
sub x1, x1, #4
3: adds x1, x1, #2
b.mi 4f
USER(9f, strh wzr, [x0], #2 )
sub x1, x1, #2
4: adds x1, x1, #1
b.mi 5f
USER(9f, strb wzr, [x0] )
5: mov x0, #0
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN)
ret
ENDPROC(__clear_user)
.section .fixup,"ax"
.align 2
9: mov x0, x2 // return the original size
ret
.previous
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