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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.
*/
#include <asm/export.h>
/* 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 __clear_user
.ent __clear_user
.frame $30, 0, $26
.prologue 0
$loop:
and $1, 3, $4 # e0 :
beq $4, 1f # .. e1 :
0: EX( stq_u $31, 0($16) ) # e0 : zero one word
subq $0, 8, $0 # .. e1 :
subq $4, 1, $4 # e0 :
addq $16, 8, $16 # .. e1 :
bne $4, 0b # e1 :
unop # :
1: bic $1, 3, $1 # e0 :
beq $1, $tail # .. e1 :
2: EX( stq_u $31, 0($16) ) # e0 : zero four words
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 8($16) ) # e0 :
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 16($16) ) # e0 :
subq $0, 8, $0 # .. e1 :
EX( stq_u $31, 24($16) ) # e0 :
subq $0, 8, $0 # .. e1 :
subq $1, 4, $1 # e0 :
addq $16, 32, $16 # .. e1 :
bne $1, 2b # e1 :
$tail:
bne $2, 1f # e1 : is there a tail to do?
ret $31, ($26), 1 # .. e1 :
1: EX( ldq_u $5, 0($16) ) # e0 :
clr $0 # .. e1 :
nop # e1 :
mskqh $5, $0, $5 # e0 :
EX( stq_u $5, 0($16) ) # e0 :
ret $31, ($26), 1 # .. e1 :
__clear_user:
and $17, $17, $0
and $16, 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($16) ) # e0 : load dst word to mask back in
beq $1, $oneword # .. e1 : sub-word store?
mskql $5, $16, $5 # e0 : take care of misaligned head
addq $16, 8, $16 # .. e1 :
EX( stq_u $5, -8($16) ) # 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, $16, $4 # e0 :
mskqh $5, $2, $5 # e0 :
or $5, $4, $5 # e1 :
EX( stq_u $5, 0($16) ) # e0 :
clr $0 # .. e1 :
$zerolength:
$exception:
ret $31, ($26), 1 # .. e1 :
.end __clear_user
EXPORT_SYMBOL(__clear_user)
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