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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";        \
        .gprel32 99b;                   \
        lda $31, $exitin-99b($31);      \
        .previous

#define EXO(x,y...)                     \
        99: x,##y;                      \
        .section __ex_table,"a";        \
        .gprel32 99b;                   \
        lda $31, $exitout-99b($31);     \
        .previous

        .set noat
        .align 3
        .globl __copy_user
        .ent __copy_user
__copy_user:
        ldgp $29,0($27)                 # we do exceptions -- we need the gp.
        .prologue 1
        and $6,7,$3
        beq $0,$35
        beq $3,$36
        subq $3,8,$3
        .align 5
$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 5
$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 5
$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 5
$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