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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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