aboutsummaryrefslogtreecommitdiff
path: root/arch/arm/lib/csumpartial.S
blob: 87c9471be8b65aa527c5805369430b2e49cee961 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/lib/csumpartial.S
 *
 *  Copyright (C) 1995-1998 Russell King
 */
#include <linux/linkage.h>
#include <asm/assembler.h>

		.text

/*
 * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
 * Params  : r0 = buffer, r1 = len, r2 = checksum
 * Returns : r0 = new checksum
 */

buf	.req	r0
len	.req	r1
sum	.req	r2
td0	.req	r3
td1	.req	r4	@ save before use
td2	.req	r5	@ save before use
td3	.req	lr

.Lzero:		mov	r0, sum
		add	sp, sp, #4
		ldr	pc, [sp], #4

		/*
		 * Handle 0 to 7 bytes, with any alignment of source and
		 * destination pointers.  Note that when we get here, C = 0
		 */
.Lless8:		teq	len, #0			@ check for zero count
		beq	.Lzero

		/* we must have at least one byte. */
		tst	buf, #1			@ odd address?
		movne	sum, sum, ror #8
		ldrbne	td0, [buf], #1
		subne	len, len, #1
		adcsne	sum, sum, td0, put_byte_1

.Lless4:		tst	len, #6
		beq	.Lless8_byte

		/* we are now half-word aligned */

.Lless8_wordlp:
#if __LINUX_ARM_ARCH__ >= 4
		ldrh	td0, [buf], #2
		sub	len, len, #2
#else
		ldrb	td0, [buf], #1
		ldrb	td3, [buf], #1
		sub	len, len, #2
#ifndef __ARMEB__
		orr	td0, td0, td3, lsl #8
#else
		orr	td0, td3, td0, lsl #8
#endif
#endif
		adcs	sum, sum, td0
		tst	len, #6
		bne	.Lless8_wordlp

.Lless8_byte:	tst	len, #1			@ odd number of bytes
		ldrbne	td0, [buf], #1		@ include last byte
		adcsne	sum, sum, td0, put_byte_0	@ update checksum

.Ldone:		adc	r0, sum, #0		@ collect up the last carry
		ldr	td0, [sp], #4
		tst	td0, #1			@ check buffer alignment
		movne	r0, r0, ror #8		@ rotate checksum by 8 bits
		ldr	pc, [sp], #4		@ return

.Lnot_aligned:	tst	buf, #1			@ odd address
		ldrbne	td0, [buf], #1		@ make even
		subne	len, len, #1
		adcsne	sum, sum, td0, put_byte_1	@ update checksum

		tst	buf, #2			@ 32-bit aligned?
#if __LINUX_ARM_ARCH__ >= 4
		ldrhne	td0, [buf], #2		@ make 32-bit aligned
		subne	len, len, #2
#else
		ldrbne	td0, [buf], #1
		ldrbne	ip, [buf], #1
		subne	len, len, #2
#ifndef __ARMEB__
		orrne	td0, td0, ip, lsl #8
#else
		orrne	td0, ip, td0, lsl #8
#endif
#endif
		adcsne	sum, sum, td0		@ update checksum
		ret	lr

ENTRY(csum_partial)
		stmfd	sp!, {buf, lr}
		cmp	len, #8			@ Ensure that we have at least
		blo	.Lless8			@ 8 bytes to copy.

		tst	buf, #1
		movne	sum, sum, ror #8

		adds	sum, sum, #0		@ C = 0
		tst	buf, #3			@ Test destination alignment
		blne	.Lnot_aligned		@ align destination, return here

1:		bics	ip, len, #31
		beq	3f

		stmfd	sp!, {r4 - r5}
2:		ldmia	buf!, {td0, td1, td2, td3}
		adcs	sum, sum, td0
		adcs	sum, sum, td1
		adcs	sum, sum, td2
		adcs	sum, sum, td3
		ldmia	buf!, {td0, td1, td2, td3}
		adcs	sum, sum, td0
		adcs	sum, sum, td1
		adcs	sum, sum, td2
		adcs	sum, sum, td3
		sub	ip, ip, #32
		teq	ip, #0
		bne	2b
		ldmfd	sp!, {r4 - r5}

3:		tst	len, #0x1c		@ should not change C
		beq	.Lless4

4:		ldr	td0, [buf], #4
		sub	len, len, #4
		adcs	sum, sum, td0
		tst	len, #0x1c
		bne	4b
		b	.Lless4
ENDPROC(csum_partial)