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114 lines
2.6 KiB
114 lines
2.6 KiB
20 years ago
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/*
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* arch/alpha/lib/clear_user.S
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* Contributed by Richard Henderson <rth@tamu.edu>
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*
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* Zero user space, handling exceptions as we go.
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*
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* We have to make sure that $0 is always up-to-date and contains the
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* right "bytes left to zero" value (and that it is updated only _after_
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* a successful copy). There is also some rather minor exception setup
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* stuff.
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*
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* NOTE! This is not directly C-callable, because the calling semantics
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* are 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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* exception pointer in $7
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* return address in $28 (exceptions expect it there)
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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
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*/
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/* Allow an exception for an insn; exit if we get one. */
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#define EX(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, $exception-99b($31); \
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.previous
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.set noat
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.set noreorder
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.align 4
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.globl __do_clear_user
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.ent __do_clear_user
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.frame $30, 0, $28
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.prologue 0
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$loop:
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and $1, 3, $4 # e0 :
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beq $4, 1f # .. e1 :
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0: EX( stq_u $31, 0($6) ) # e0 : zero one word
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subq $0, 8, $0 # .. e1 :
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subq $4, 1, $4 # e0 :
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addq $6, 8, $6 # .. e1 :
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bne $4, 0b # e1 :
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unop # :
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1: bic $1, 3, $1 # e0 :
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beq $1, $tail # .. e1 :
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2: EX( stq_u $31, 0($6) ) # e0 : zero four words
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subq $0, 8, $0 # .. e1 :
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EX( stq_u $31, 8($6) ) # e0 :
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subq $0, 8, $0 # .. e1 :
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EX( stq_u $31, 16($6) ) # e0 :
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subq $0, 8, $0 # .. e1 :
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EX( stq_u $31, 24($6) ) # e0 :
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subq $0, 8, $0 # .. e1 :
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subq $1, 4, $1 # e0 :
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addq $6, 32, $6 # .. e1 :
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bne $1, 2b # e1 :
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$tail:
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bne $2, 1f # e1 : is there a tail to do?
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ret $31, ($28), 1 # .. e1 :
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1: EX( ldq_u $5, 0($6) ) # e0 :
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clr $0 # .. e1 :
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nop # e1 :
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mskqh $5, $0, $5 # e0 :
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EX( stq_u $5, 0($6) ) # e0 :
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ret $31, ($28), 1 # .. e1 :
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__do_clear_user:
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and $6, 7, $4 # e0 : find dest misalignment
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beq $0, $zerolength # .. e1 :
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addq $0, $4, $1 # e0 : bias counter
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and $1, 7, $2 # e1 : number of bytes in tail
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srl $1, 3, $1 # e0 :
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beq $4, $loop # .. e1 :
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EX( ldq_u $5, 0($6) ) # e0 : load dst word to mask back in
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beq $1, $oneword # .. e1 : sub-word store?
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mskql $5, $6, $5 # e0 : take care of misaligned head
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addq $6, 8, $6 # .. e1 :
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EX( stq_u $5, -8($6) ) # e0 :
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addq $0, $4, $0 # .. e1 : bytes left -= 8 - misalignment
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subq $1, 1, $1 # e0 :
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subq $0, 8, $0 # .. e1 :
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br $loop # e1 :
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unop # :
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$oneword:
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mskql $5, $6, $4 # e0 :
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mskqh $5, $2, $5 # e0 :
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or $5, $4, $5 # e1 :
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EX( stq_u $5, 0($6) ) # e0 :
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clr $0 # .. e1 :
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$zerolength:
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$exception:
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ret $31, ($28), 1 # .. e1 :
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.end __do_clear_user
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