1/* 2 * arch/alpha/lib/copy_user.S 3 * 4 * Copy to/from user space, handling exceptions as we go.. This 5 * isn't exactly pretty. 6 * 7 * This is essentially the same as "memcpy()", but with a few twists. 8 * Notably, we have to make sure that $0 is always up-to-date and 9 * contains the right "bytes left to copy" value (and that it is updated 10 * only _after_ a successful copy). There is also some rather minor 11 * exception setup stuff.. 12 * 13 * NOTE! This is not directly C-callable, because the calling semantics are 14 * different: 15 * 16 * Inputs: 17 * length in $0 18 * destination address in $6 19 * source address in $7 20 * return address in $28 21 * 22 * Outputs: 23 * bytes left to copy in $0 24 * 25 * Clobbers: 26 * $1,$2,$3,$4,$5,$6,$7 27 */ 28 29/* Allow an exception for an insn; exit if we get one. */ 30#define EXI(x,y...) \ 31 99: x,##y; \ 32 .section __ex_table,"a"; \ 33 .long 99b - .; \ 34 lda $31, $exitin-99b($31); \ 35 .previous 36 37#define EXO(x,y...) \ 38 99: x,##y; \ 39 .section __ex_table,"a"; \ 40 .long 99b - .; \ 41 lda $31, $exitout-99b($31); \ 42 .previous 43 44 .set noat 45 .align 4 46 .globl __copy_user 47 .ent __copy_user 48__copy_user: 49 .prologue 0 50 and $6,7,$3 51 beq $0,$35 52 beq $3,$36 53 subq $3,8,$3 54 .align 4 55$37: 56 EXI( ldq_u $1,0($7) ) 57 EXO( ldq_u $2,0($6) ) 58 extbl $1,$7,$1 59 mskbl $2,$6,$2 60 insbl $1,$6,$1 61 addq $3,1,$3 62 bis $1,$2,$1 63 EXO( stq_u $1,0($6) ) 64 subq $0,1,$0 65 addq $6,1,$6 66 addq $7,1,$7 67 beq $0,$41 68 bne $3,$37 69$36: 70 and $7,7,$1 71 bic $0,7,$4 72 beq $1,$43 73 beq $4,$48 74 EXI( ldq_u $3,0($7) ) 75 .align 4 76$50: 77 EXI( ldq_u $2,8($7) ) 78 subq $4,8,$4 79 extql $3,$7,$3 80 extqh $2,$7,$1 81 bis $3,$1,$1 82 EXO( stq $1,0($6) ) 83 addq $7,8,$7 84 subq $0,8,$0 85 addq $6,8,$6 86 bis $2,$2,$3 87 bne $4,$50 88$48: 89 beq $0,$41 90 .align 4 91$57: 92 EXI( ldq_u $1,0($7) ) 93 EXO( ldq_u $2,0($6) ) 94 extbl $1,$7,$1 95 mskbl $2,$6,$2 96 insbl $1,$6,$1 97 bis $1,$2,$1 98 EXO( stq_u $1,0($6) ) 99 subq $0,1,$0 100 addq $6,1,$6 101 addq $7,1,$7 102 bne $0,$57 103 br $31,$41 104 .align 4 105$43: 106 beq $4,$65 107 .align 4 108$66: 109 EXI( ldq $1,0($7) ) 110 subq $4,8,$4 111 EXO( stq $1,0($6) ) 112 addq $7,8,$7 113 subq $0,8,$0 114 addq $6,8,$6 115 bne $4,$66 116$65: 117 beq $0,$41 118 EXI( ldq $2,0($7) ) 119 EXO( ldq $1,0($6) ) 120 mskql $2,$0,$2 121 mskqh $1,$0,$1 122 bis $2,$1,$2 123 EXO( stq $2,0($6) ) 124 bis $31,$31,$0 125$41: 126$35: 127$exitout: 128 ret $31,($28),1 129 130$exitin: 131 /* A stupid byte-by-byte zeroing of the rest of the output 132 buffer. This cures security holes by never leaving 133 random kernel data around to be copied elsewhere. */ 134 135 mov $0,$1 136$101: 137 EXO ( ldq_u $2,0($6) ) 138 subq $1,1,$1 139 mskbl $2,$6,$2 140 EXO ( stq_u $2,0($6) ) 141 addq $6,1,$6 142 bgt $1,$101 143 ret $31,($28),1 144 145 .end __copy_user 146