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

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 * arch/alpha/lib/copy_user.S

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 *

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 * Copy to/from user space, handling exceptions as we go..  This

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 * isn't exactly pretty.

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 *

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 * This is essentially the same as "memcpy()", but with a few twists.

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 * Notably, we have to make sure that $0 is always up-to-date and

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 * contains the right "bytes left to copy" value (and that it is updated

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 * only _after_ a successful copy). There is also some rather minor

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 * exception setup stuff..

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 *

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 * NOTE! This is not directly C-callable, because the calling semantics are

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 * different:

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 *

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 * Inputs:

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 *	length in $0

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 *	destination address in $6

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 *	source address in $7

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 *	return address in $28

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 *

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 * Outputs:

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 *	bytes left to copy in $0

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 *

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 * Clobbers:

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 *	$1,$2,$3,$4,$5,$6,$7

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 */

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/* Allow an exception for an insn; exit if we get one.  */

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#define EXI(x,y...)			\

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	99: x,##y;			\

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	.section __ex_table,"a";	\

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	.long 99b - .;			\

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	lda $31, $exitin-99b($31);	\

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	.previous

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#define EXO(x,y...)			\

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	99: x,##y;			\

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	.section __ex_table,"a";	\

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	.long 99b - .;			\

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	lda $31, $exitout-99b($31);	\

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	.previous

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	.set noat

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	.align 4

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	.globl __copy_user

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	.ent __copy_user

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__copy_user:

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	.prologue 0

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	and $6,7,$3

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	beq $0,$35

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	beq $3,$36

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	subq $3,8,$3

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	.align 4

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$37:

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	EXI( ldq_u $1,0($7) )

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	EXO( ldq_u $2,0($6) )

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	extbl $1,$7,$1

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	mskbl $2,$6,$2

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	insbl $1,$6,$1

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	addq $3,1,$3

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	bis $1,$2,$1

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	EXO( stq_u $1,0($6) )

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	subq $0,1,$0

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	addq $6,1,$6

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	addq $7,1,$7

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	beq $0,$41

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	bne $3,$37

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$36:

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	and $7,7,$1

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	bic $0,7,$4

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	beq $1,$43

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	beq $4,$48

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	EXI( ldq_u $3,0($7) )

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	.align 4

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$50:

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	EXI( ldq_u $2,8($7) )

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	subq $4,8,$4

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	extql $3,$7,$3

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	extqh $2,$7,$1

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	bis $3,$1,$1

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	EXO( stq $1,0($6) )

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	addq $7,8,$7

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	subq $0,8,$0

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	addq $6,8,$6

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	bis $2,$2,$3

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	bne $4,$50

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$48:

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	beq $0,$41

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	.align 4

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$57:

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	EXI( ldq_u $1,0($7) )

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	EXO( ldq_u $2,0($6) )

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	extbl $1,$7,$1

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	mskbl $2,$6,$2

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	insbl $1,$6,$1

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	bis $1,$2,$1

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	EXO( stq_u $1,0($6) )

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	subq $0,1,$0

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	addq $6,1,$6

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	addq $7,1,$7

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	bne $0,$57

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	br $31,$41

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	.align 4

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$43:

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	beq $4,$65

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	.align 4

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$66:

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	EXI( ldq $1,0($7) )

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	subq $4,8,$4

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	EXO( stq $1,0($6) )

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	addq $7,8,$7

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	subq $0,8,$0

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	addq $6,8,$6

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	bne $4,$66

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$65:

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	beq $0,$41

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	EXI( ldq $2,0($7) )

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	EXO( ldq $1,0($6) )

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	mskql $2,$0,$2

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	mskqh $1,$0,$1

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	bis $2,$1,$2

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	EXO( stq $2,0($6) )

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	bis $31,$31,$0

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$41:

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$35:

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$exitout:

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	ret $31,($28),1

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$exitin:

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	/* A stupid byte-by-byte zeroing of the rest of the output

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	   buffer.  This cures security holes by never leaving 

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	   random kernel data around to be copied elsewhere.  */

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	mov $0,$1

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$101:

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	EXO ( ldq_u $2,0($6) )

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	subq $1,1,$1

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	mskbl $2,$6,$2

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	EXO ( stq_u $2,0($6) )

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	addq $6,1,$6

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	bgt $1,$101

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	ret $31,($28),1

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	.end __copy_user

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