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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/unicore32/lib/clear_user.S
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/*

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 * linux/arch/unicore32/lib/clear_user.S

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 *

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 * Code specific to PKUnity SoC and UniCore ISA

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 *

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 * Copyright (C) 2001-2010 GUAN Xue-tao

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 *

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 * This program is free software; you can redistribute it and/or modify

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 * it under the terms of the GNU General Public License version 2 as

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 * published by the Free Software Foundation.

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 */

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#include <linux/linkage.h>

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#include <asm/assembler.h>

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		.text

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/* Prototype: int __clear_user(void *addr, size_t sz)

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 * Purpose  : clear some user memory

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 * Params   : addr - user memory address to clear

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 *          : sz   - number of bytes to clear

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 * Returns  : number of bytes NOT cleared

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 */

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WEAK(__clear_user)

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		stm.w	(lr), [sp-]

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		stm.w	(r1), [sp-]

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		mov	r2, #0

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		csub.a	r1, #4

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		bsl	2f

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		and.a	ip, r0, #3

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		beq	1f

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		csub.a	ip, #2

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		strusr	r2, r0, 1

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		strusr	r2, r0, 1, el

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		strusr	r2, r0, 1, sl

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		rsub	ip, ip, #4

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		sub	r1, r1, ip		@  7  6  5  4  3  2  1

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1:		sub.a	r1, r1, #8		@ -1 -2 -3 -4 -5 -6 -7

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		strusr	r2, r0, 4, ns, rept=2

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		bns	1b

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		add.a	r1, r1, #4		@  3  2  1  0 -1 -2 -3

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		strusr	r2, r0, 4, ns

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2:		cand.a	r1, #2			@ 1x 1x 0x 0x 1x 1x 0x

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		strusr	r2, r0, 1, ne, rept=2

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		cand.a	r1, #1			@ x1 x0 x1 x0 x1 x0 x1

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		beq	3f

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USER(		stb.u	r2, [r0])

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3:		mov	r0, #0

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		ldm.w	(r1), [sp]+

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		ldm.w	(pc), [sp]+

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ENDPROC(__clear_user)

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		.pushsection .fixup,"ax"

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		.align	0

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9001:		ldm.w	(r0), [sp]+

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		ldm.w	(pc), [sp]+

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		.popsection

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