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
18 buf .req r0
19 len .req r1
20 sum .req r2
21 td0 .req r3
22 td1 .req r4 @ save before use
23 td2 .req r5 @ save before use
24 td3 .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
99 ENTRY(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
111 1: bics ip, len, #31
112 beq 3f
113
114 stmfd sp!, {r4 - r5}
115 2: 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
130 3: tst len, #0x1c @ should not change C
131 beq .Lless4
132
133 4: ldr td0, [buf], #4
134 sub len, len, #4
135 adcs sum, sum, td0
136 tst len, #0x1c
137 bne 4b
138 b .Lless4
139 ENDPROC(csum_partial)
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