diff options
Diffstat (limited to 'arch/alpha/lib/clear_user.S')
| -rw-r--r-- | arch/alpha/lib/clear_user.S | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/arch/alpha/lib/clear_user.S b/arch/alpha/lib/clear_user.S new file mode 100644 index 00000000000..8860316c195 --- /dev/null +++ b/arch/alpha/lib/clear_user.S @@ -0,0 +1,113 @@ +/* + * 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 |