1 /* SPDX-License-Identifier: GPL-2.0-only */ !! 1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* 2 /*
3 * Copyright (C) 2021 Arm Ltd. !! 3 * arch/alpha/lib/clear_user.S
4 */ !! 4 * Contributed by Richard Henderson <rth@tamu.edu>
5 !! 5 *
6 #include <linux/linkage.h> !! 6 * Zero user space, handling exceptions as we go.
7 #include <asm/asm-uaccess.h> <<
8 <<
9 .text <<
10 <<
11 /* Prototype: int __arch_clear_user(void *addr <<
12 * Purpose : clear some user memory <<
13 * Params : addr - user memory address to cl <<
14 * : sz - number of bytes to clear <<
15 * Returns : number of bytes NOT cleared <<
16 * 7 *
17 * Alignment fixed up by hardware. !! 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.
18 */ 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
>> 36 0: 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
>> 43 1: bic $1, 3, $1 # e0 :
>> 44 beq $1, $tail # .. e1 :
>> 45
>> 46 2: 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
>> 62 1: 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 :
19 100
20 .p2align 4 !! 101 .end __clear_user
21 // Alignment is for the loop, but sinc !! 102 EXPORT_SYMBOL(__clear_user)
22 // is also 16 bytes we can keep any pa <<
23 SYM_FUNC_START(__arch_clear_user) <<
24 add x2, x0, x1 <<
25 subs x1, x1, #8 <<
26 b.mi 2f <<
27 1: <<
28 USER(9f, sttr xzr, [x0]) <<
29 add x0, x0, #8 <<
30 subs x1, x1, #8 <<
31 b.hi 1b <<
32 USER(9f, sttr xzr, [x2, #-8]) <<
33 mov x0, #0 <<
34 ret <<
35 <<
36 2: tbz x1, #2, 3f <<
37 USER(9f, sttr wzr, [x0]) <<
38 USER(8f, sttr wzr, [x2, #-4]) <<
39 mov x0, #0 <<
40 ret <<
41 <<
42 3: tbz x1, #1, 4f <<
43 USER(9f, sttrh wzr, [x0]) <<
44 4: tbz x1, #0, 5f <<
45 USER(7f, sttrb wzr, [x2, #-1]) <<
46 5: mov x0, #0 <<
47 ret <<
48 <<
49 // Exception fixups <<
50 7: sub x0, x2, #5 // Adjust for <<
51 8: add x0, x0, #4 // ...or the s <<
52 9: sub x0, x2, x0 <<
53 ret <<
54 SYM_FUNC_END(__arch_clear_user) <<
55 EXPORT_SYMBOL(__arch_clear_user) <<
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