xref: /openbmc/linux/arch/alpha/lib/clear_user.S (revision 4da722ca) 
1/*
2 * arch/alpha/lib/clear_user.S
3 * Contributed by Richard Henderson <rth@tamu.edu>
4 *
5 * Zero user space, handling exceptions as we go.
6 *
7 * We have to make sure that $0 is always up-to-date and contains the
8 * right "bytes left to zero" value (and that it is updated only _after_
9 * a successful copy).  There is also some rather minor exception setup
10 * stuff.
11 */
12#include <asm/export.h>
13
14/* Allow an exception for an insn; exit if we get one.  */
15#define EX(x,y...)			\
16	99: x,##y;			\
17	.section __ex_table,"a";	\
18	.long 99b - .;			\
19	lda $31, $exception-99b($31); 	\
20	.previous
21
22	.set noat
23	.set noreorder
24	.align 4
25
26	.globl __clear_user
27	.ent __clear_user
28	.frame	$30, 0, $26
29	.prologue 0
30
31$loop:
32	and	$1, 3, $4	# e0    :
33	beq	$4, 1f		# .. e1 :
34
350:	EX( stq_u $31, 0($16) )	# e0    : zero one word
36	subq	$0, 8, $0	# .. e1 :
37	subq	$4, 1, $4	# e0    :
38	addq	$16, 8, $16	# .. e1 :
39	bne	$4, 0b		# e1    :
40	unop			#       :
41
421:	bic	$1, 3, $1	# e0    :
43	beq	$1, $tail	# .. e1 :
44
452:	EX( stq_u $31, 0($16) )	# e0    : zero four words
46	subq	$0, 8, $0	# .. e1 :
47	EX( stq_u $31, 8($16) )	# e0    :
48	subq	$0, 8, $0	# .. e1 :
49	EX( stq_u $31, 16($16) )	# e0    :
50	subq	$0, 8, $0	# .. e1 :
51	EX( stq_u $31, 24($16) )	# e0    :
52	subq	$0, 8, $0	# .. e1 :
53	subq	$1, 4, $1	# e0    :
54	addq	$16, 32, $16	# .. e1 :
55	bne	$1, 2b		# e1    :
56
57$tail:
58	bne	$2, 1f		# e1    : is there a tail to do?
59	ret	$31, ($26), 1	# .. e1 :
60
611:	EX( ldq_u $5, 0($16) )	# e0    :
62	clr	$0		# .. e1 :
63	nop			# e1    :
64	mskqh	$5, $0, $5	# e0    :
65	EX( stq_u $5, 0($16) )	# e0    :
66	ret	$31, ($26), 1	# .. e1 :
67
68__clear_user:
69	and	$17, $17, $0
70	and	$16, 7, $4	# e0    : find dest misalignment
71	beq	$0, $zerolength # .. e1 :
72	addq	$0, $4, $1	# e0    : bias counter
73	and	$1, 7, $2	# e1    : number of bytes in tail
74	srl	$1, 3, $1	# e0    :
75	beq	$4, $loop	# .. e1 :
76
77	EX( ldq_u $5, 0($16) )	# e0    : load dst word to mask back in
78	beq	$1, $oneword	# .. e1 : sub-word store?
79
80	mskql	$5, $16, $5	# e0    : take care of misaligned head
81	addq	$16, 8, $16	# .. e1 :
82	EX( stq_u $5, -8($16) )	# e0    :
83	addq	$0, $4, $0	# .. e1 : bytes left -= 8 - misalignment
84	subq	$1, 1, $1	# e0    :
85	subq	$0, 8, $0	# .. e1 :
86	br	$loop		# e1    :
87	unop			#       :
88
89$oneword:
90	mskql	$5, $16, $4	# e0    :
91	mskqh	$5, $2, $5	# e0    :
92	or	$5, $4, $5	# e1    :
93	EX( stq_u $5, 0($16) )	# e0    :
94	clr	$0		# .. e1 :
95
96$zerolength:
97$exception:
98	ret	$31, ($26), 1	# .. e1 :
99
100	.end __clear_user
101	EXPORT_SYMBOL(__clear_user)
102