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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * arch/alpha/lib/clear_user.S
4 * Contributed by Richard Henderson <rth@tamu.edu>
5 *
6 * Zero user space, handling exceptions as we go.
7 *
8 * We have to make sure that $0 is always up-to-date and contains the
9 * right "bytes left to zero" value (and that it is updated only _after_
10 * a successful copy). There is also some rather minor exception setup
11 * stuff.
12 */
13#include <linux/export.h>
14
15/* Allow an exception for an insn; exit if we get one. */
16#define EX(x,y...) \
17 99: x,##y; \
18 .section __ex_table,"a"; \
19 .long 99b - .; \
20 lda $31, $exception-99b($31); \
21 .previous
22
23 .set noat
24 .set noreorder
25 .align 4
26
27 .globl __clear_user
28 .ent __clear_user
29 .frame $30, 0, $26
30 .prologue 0
31
32$loop:
33 and $1, 3, $4 # e0 :
34 beq $4, 1f # .. e1 :
35
360: EX( stq_u $31, 0($16) ) # e0 : zero one word
37 subq $0, 8, $0 # .. e1 :
38 subq $4, 1, $4 # e0 :
39 addq $16, 8, $16 # .. e1 :
40 bne $4, 0b # e1 :
41 unop # :
42
431: bic $1, 3, $1 # e0 :
44 beq $1, $tail # .. e1 :
45
462: EX( stq_u $31, 0($16) ) # e0 : zero four words
47 subq $0, 8, $0 # .. e1 :
48 EX( stq_u $31, 8($16) ) # e0 :
49 subq $0, 8, $0 # .. e1 :
50 EX( stq_u $31, 16($16) ) # e0 :
51 subq $0, 8, $0 # .. e1 :
52 EX( stq_u $31, 24($16) ) # e0 :
53 subq $0, 8, $0 # .. e1 :
54 subq $1, 4, $1 # e0 :
55 addq $16, 32, $16 # .. e1 :
56 bne $1, 2b # e1 :
57
58$tail:
59 bne $2, 1f # e1 : is there a tail to do?
60 ret $31, ($26), 1 # .. e1 :
61
621: EX( ldq_u $5, 0($16) ) # e0 :
63 clr $0 # .. e1 :
64 nop # e1 :
65 mskqh $5, $0, $5 # e0 :
66 EX( stq_u $5, 0($16) ) # e0 :
67 ret $31, ($26), 1 # .. e1 :
68
69__clear_user:
70 and $17, $17, $0
71 and $16, 7, $4 # e0 : find dest misalignment
72 beq $0, $zerolength # .. e1 :
73 addq $0, $4, $1 # e0 : bias counter
74 and $1, 7, $2 # e1 : number of bytes in tail
75 srl $1, 3, $1 # e0 :
76 beq $4, $loop # .. e1 :
77
78 EX( ldq_u $5, 0($16) ) # e0 : load dst word to mask back in
79 beq $1, $oneword # .. e1 : sub-word store?
80
81 mskql $5, $16, $5 # e0 : take care of misaligned head
82 addq $16, 8, $16 # .. e1 :
83 EX( stq_u $5, -8($16) ) # e0 :
84 addq $0, $4, $0 # .. e1 : bytes left -= 8 - misalignment
85 subq $1, 1, $1 # e0 :
86 subq $0, 8, $0 # .. e1 :
87 br $loop # e1 :
88 unop # :
89
90$oneword:
91 mskql $5, $16, $4 # e0 :
92 mskqh $5, $2, $5 # e0 :
93 or $5, $4, $5 # e1 :
94 EX( stq_u $5, 0($16) ) # e0 :
95 clr $0 # .. e1 :
96
97$zerolength:
98$exception:
99 ret $31, ($26), 1 # .. e1 :
100
101 .end __clear_user
102 EXPORT_SYMBOL(__clear_user)