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/*
* arch/alpha/lib/clear_user.S
* Contributed by Richard Henderson <rth@tamu.edu>
*
* Zero user space, handling exceptions as we go.
*
* We have to make sure that $0 is always up-to-date and contains the
* right "bytes left to zero" 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
* exception pointer in $7
* return address in $28 (exceptions expect it there)
*
* Outputs:
* bytes left to copy in $0
*
* Clobbers:
* $1,$2,$3,$4,$5,$6
*/
/* Allow an exception for an insn; exit if we get one. */
#define EX(x,y...) \
99: x,##y; \
.section __ex_table,"a"; \
.long 99b - .; \
lda $31, $exception-99b($31); \
.previous
.set noat
.set noreorder
.align 4
.globl __do_clear_user
.ent __do_clear_user
.frame $30, 0, $28
.prologue 0
$loop:
and $1, 3, $4 # e0 :
beq $4, 1f # .. e1 :
0: EX( stq_u $31, 0($6) ) # e0 : zero one word
subq $0, 8, $0 # .. e1 :
subq $4, 1, $4 # e0 :
addq $6, 8, $6 # .. e1 :
bne $4, 0b # e1 :
unop # :
1: bic $1, 3, $1 # e0 :
beq $1, $tail # .. e1 :
2: EX( stq_u $31, 0($6) ) # e0 : zero four words
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 8($6) ) # e0 :
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 16($6) ) # e0 :
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 24($6) ) # e0 :
subq $0, 8, $0 # .. e1 :
subq $1, 4, $1 # e0 :
addq $6, 32, $6 # .. e1 :
bne $1, 2b # e1 :
$tail:
bne $2, 1f # e1 : is there a tail to do?
ret $31, ($28), 1 # .. e1 :
1: EX( ldq_u $5, 0($6) ) # e0 :
clr $0 # .. e1 :
nop # e1 :
mskqh $5, $0, $5 # e0 :
EX( stq_u $5, 0($6) ) # e0 :
ret $31, ($28), 1 # .. e1 :
__do_clear_user:
and $6, 7, $4 # e0 : find dest misalignment
beq $0, $zerolength # .. e1 :
addq $0, $4, $1 # e0 : bias counter
and $1, 7, $2 # e1 : number of bytes in tail
srl $1, 3, $1 # e0 :
beq $4, $loop # .. e1 :
EX( ldq_u $5, 0($6) ) # e0 : load dst word to mask back in
beq $1, $oneword # .. e1 : sub-word store?
mskql $5, $6, $5 # e0 : take care of misaligned head
addq $6, 8, $6 # .. e1 :
EX( stq_u $5, -8($6) ) # e0 :
addq $0, $4, $0 # .. e1 : bytes left -= 8 - misalignment
subq $1, 1, $1 # e0 :
subq $0, 8, $0 # .. e1 :
br $loop # e1 :
unop # :
$oneword:
mskql $5, $6, $4 # e0 :
mskqh $5, $2, $5 # e0 :
or $5, $4, $5 # e1 :
EX( stq_u $5, 0($6) ) # e0 :
clr $0 # .. e1 :
$zerolength:
$exception:
ret $31, ($28), 1 # .. e1 :
.end __do_clear_user
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