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copy_user.S
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copy_user.S
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/*
* arch/alpha/lib/copy_user.S
*
* Copy to/from user space, handling exceptions as we go.. This
* isn't exactly pretty.
*
* This is essentially the same as "memcpy()", but with a few twists.
* Notably, we have to make sure that $0 is always up-to-date and
* contains the right "bytes left to copy" value (and that it is updated
* only _after_ a successful copy). There is also some rather minor
* exception setup stuff..
*
* NOTE! This is not directly C-callable, because the calling semantics are
* different:
*
* Inputs:
* length in $0
* destination address in $6
* source address in $7
* return address in $28
*
* Outputs:
* bytes left to copy in $0
*
* Clobbers:
* $1,$2,$3,$4,$5,$6,$7
*/
/* Allow an exception for an insn; exit if we get one. */
#define EXI(x,y...) \
99: x,##y; \
.section __ex_table,"a"; \
.long 99b - .; \
lda $31, $exitin-99b($31); \
.previous
#define EXO(x,y...) \
99: x,##y; \
.section __ex_table,"a"; \
.long 99b - .; \
lda $31, $exitout-99b($31); \
.previous
.set noat
.align 4
.globl __copy_user
.ent __copy_user
__copy_user:
.prologue 0
and $6,7,$3
beq $0,$35
beq $3,$36
subq $3,8,$3
.align 4
$37:
EXI( ldq_u $1,0($7) )
EXO( ldq_u $2,0($6) )
extbl $1,$7,$1
mskbl $2,$6,$2
insbl $1,$6,$1
addq $3,1,$3
bis $1,$2,$1
EXO( stq_u $1,0($6) )
subq $0,1,$0
addq $6,1,$6
addq $7,1,$7
beq $0,$41
bne $3,$37
$36:
and $7,7,$1
bic $0,7,$4
beq $1,$43
beq $4,$48
EXI( ldq_u $3,0($7) )
.align 4
$50:
EXI( ldq_u $2,8($7) )
subq $4,8,$4
extql $3,$7,$3
extqh $2,$7,$1
bis $3,$1,$1
EXO( stq $1,0($6) )
addq $7,8,$7
subq $0,8,$0
addq $6,8,$6
bis $2,$2,$3
bne $4,$50
$48:
beq $0,$41
.align 4
$57:
EXI( ldq_u $1,0($7) )
EXO( ldq_u $2,0($6) )
extbl $1,$7,$1
mskbl $2,$6,$2
insbl $1,$6,$1
bis $1,$2,$1
EXO( stq_u $1,0($6) )
subq $0,1,$0
addq $6,1,$6
addq $7,1,$7
bne $0,$57
br $31,$41
.align 4
$43:
beq $4,$65
.align 4
$66:
EXI( ldq $1,0($7) )
subq $4,8,$4
EXO( stq $1,0($6) )
addq $7,8,$7
subq $0,8,$0
addq $6,8,$6
bne $4,$66
$65:
beq $0,$41
EXI( ldq $2,0($7) )
EXO( ldq $1,0($6) )
mskql $2,$0,$2
mskqh $1,$0,$1
bis $2,$1,$2
EXO( stq $2,0($6) )
bis $31,$31,$0
$41:
$35:
$exitout:
ret $31,($28),1
$exitin:
/* A stupid byte-by-byte zeroing of the rest of the output
buffer. This cures security holes by never leaving
random kernel data around to be copied elsewhere. */
mov $0,$1
$101:
EXO ( ldq_u $2,0($6) )
subq $1,1,$1
mskbl $2,$6,$2
EXO ( stq_u $2,0($6) )
addq $6,1,$6
bgt $1,$101
ret $31,($28),1
.end __copy_user