xref: /linux/arch/alpha/lib/clear_user.S (revision c48a7c44a1d02516309015b6134c9bb982e17008) 
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)
103