xref: /linux/arch/arm/lib/csumpartial.S (revision ae22a94997b8a03dcb3c922857c203246711f9d4) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/lib/csumpartial.S
4 *
5 *  Copyright (C) 1995-1998 Russell King
6 */
7#include <linux/linkage.h>
8#include <asm/assembler.h>
9
10		.text
11
12/*
13 * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
14 * Params  : r0 = buffer, r1 = len, r2 = checksum
15 * Returns : r0 = new checksum
16 */
17
18buf	.req	r0
19len	.req	r1
20sum	.req	r2
21td0	.req	r3
22td1	.req	r4	@ save before use
23td2	.req	r5	@ save before use
24td3	.req	lr
25
26.Lzero:		mov	r0, sum
27		add	sp, sp, #4
28		ldr	pc, [sp], #4
29
30		/*
31		 * Handle 0 to 7 bytes, with any alignment of source and
32		 * destination pointers.  Note that when we get here, C = 0
33		 */
34.Lless8:		teq	len, #0			@ check for zero count
35		beq	.Lzero
36
37		/* we must have at least one byte. */
38		tst	buf, #1			@ odd address?
39		movne	sum, sum, ror #8
40		ldrbne	td0, [buf], #1
41		subne	len, len, #1
42		adcsne	sum, sum, td0, put_byte_1
43
44.Lless4:		tst	len, #6
45		beq	.Lless8_byte
46
47		/* we are now half-word aligned */
48
49.Lless8_wordlp:
50#if __LINUX_ARM_ARCH__ >= 4
51		ldrh	td0, [buf], #2
52		sub	len, len, #2
53#else
54		ldrb	td0, [buf], #1
55		ldrb	td3, [buf], #1
56		sub	len, len, #2
57#ifndef __ARMEB__
58		orr	td0, td0, td3, lsl #8
59#else
60		orr	td0, td3, td0, lsl #8
61#endif
62#endif
63		adcs	sum, sum, td0
64		tst	len, #6
65		bne	.Lless8_wordlp
66
67.Lless8_byte:	tst	len, #1			@ odd number of bytes
68		ldrbne	td0, [buf], #1		@ include last byte
69		adcsne	sum, sum, td0, put_byte_0	@ update checksum
70
71.Ldone:		adc	r0, sum, #0		@ collect up the last carry
72		ldr	td0, [sp], #4
73		tst	td0, #1			@ check buffer alignment
74		movne	r0, r0, ror #8		@ rotate checksum by 8 bits
75		ldr	pc, [sp], #4		@ return
76
77.Lnot_aligned:	tst	buf, #1			@ odd address
78		ldrbne	td0, [buf], #1		@ make even
79		subne	len, len, #1
80		adcsne	sum, sum, td0, put_byte_1	@ update checksum
81
82		tst	buf, #2			@ 32-bit aligned?
83#if __LINUX_ARM_ARCH__ >= 4
84		ldrhne	td0, [buf], #2		@ make 32-bit aligned
85		subne	len, len, #2
86#else
87		ldrbne	td0, [buf], #1
88		ldrbne	ip, [buf], #1
89		subne	len, len, #2
90#ifndef __ARMEB__
91		orrne	td0, td0, ip, lsl #8
92#else
93		orrne	td0, ip, td0, lsl #8
94#endif
95#endif
96		adcsne	sum, sum, td0		@ update checksum
97		ret	lr
98
99ENTRY(csum_partial)
100		stmfd	sp!, {buf, lr}
101		cmp	len, #8			@ Ensure that we have at least
102		blo	.Lless8			@ 8 bytes to copy.
103
104		tst	buf, #1
105		movne	sum, sum, ror #8
106
107		adds	sum, sum, #0		@ C = 0
108		tst	buf, #3			@ Test destination alignment
109		blne	.Lnot_aligned		@ align destination, return here
110
1111:		bics	ip, len, #31
112		beq	3f
113
114		stmfd	sp!, {r4 - r5}
1152:		ldmia	buf!, {td0, td1, td2, td3}
116		adcs	sum, sum, td0
117		adcs	sum, sum, td1
118		adcs	sum, sum, td2
119		adcs	sum, sum, td3
120		ldmia	buf!, {td0, td1, td2, td3}
121		adcs	sum, sum, td0
122		adcs	sum, sum, td1
123		adcs	sum, sum, td2
124		adcs	sum, sum, td3
125		sub	ip, ip, #32
126		teq	ip, #0
127		bne	2b
128		ldmfd	sp!, {r4 - r5}
129
1303:		tst	len, #0x1c		@ should not change C
131		beq	.Lless4
132
1334:		ldr	td0, [buf], #4
134		sub	len, len, #4
135		adcs	sum, sum, td0
136		tst	len, #0x1c
137		bne	4b
138		b	.Lless4
139ENDPROC(csum_partial)
140