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1da177e4 LT |
1 | /* |
2 | * linux/arch/arm/lib/csumpartial.S | |
3 | * | |
4 | * Copyright (C) 1995-1998 Russell King | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | */ | |
10 | #include <linux/linkage.h> | |
11 | #include <asm/assembler.h> | |
12 | ||
13 | .text | |
14 | ||
15 | /* | |
16 | * Function: __u32 csum_partial(const char *src, int len, __u32 sum) | |
17 | * Params : r0 = buffer, r1 = len, r2 = checksum | |
18 | * Returns : r0 = new checksum | |
19 | */ | |
20 | ||
21 | buf .req r0 | |
22 | len .req r1 | |
23 | sum .req r2 | |
24 | td0 .req r3 | |
25 | td1 .req r4 @ save before use | |
26 | td2 .req r5 @ save before use | |
27 | td3 .req lr | |
28 | ||
29 | .zero: mov r0, sum | |
30 | add sp, sp, #4 | |
31 | ldr pc, [sp], #4 | |
32 | ||
33 | /* | |
34 | * Handle 0 to 7 bytes, with any alignment of source and | |
35 | * destination pointers. Note that when we get here, C = 0 | |
36 | */ | |
37 | .less8: teq len, #0 @ check for zero count | |
38 | beq .zero | |
39 | ||
40 | /* we must have at least one byte. */ | |
41 | tst buf, #1 @ odd address? | |
42 | ldrneb td0, [buf], #1 | |
43 | subne len, len, #1 | |
44 | adcnes sum, sum, td0, put_byte_1 | |
45 | ||
46 | .less4: tst len, #6 | |
47 | beq .less8_byte | |
48 | ||
49 | /* we are now half-word aligned */ | |
50 | ||
51 | .less8_wordlp: | |
52 | #if __LINUX_ARM_ARCH__ >= 4 | |
53 | ldrh td0, [buf], #2 | |
54 | sub len, len, #2 | |
55 | #else | |
56 | ldrb td0, [buf], #1 | |
57 | ldrb td3, [buf], #1 | |
58 | sub len, len, #2 | |
59 | #ifndef __ARMEB__ | |
60 | orr td0, td0, td3, lsl #8 | |
61 | #else | |
62 | orr td0, td3, td0, lsl #8 | |
63 | #endif | |
64 | #endif | |
65 | adcs sum, sum, td0 | |
66 | tst len, #6 | |
67 | bne .less8_wordlp | |
68 | ||
69 | .less8_byte: tst len, #1 @ odd number of bytes | |
70 | ldrneb td0, [buf], #1 @ include last byte | |
71 | adcnes sum, sum, td0, put_byte_0 @ update checksum | |
72 | ||
73 | .done: adc r0, sum, #0 @ collect up the last carry | |
74 | ldr td0, [sp], #4 | |
75 | tst td0, #1 @ check buffer alignment | |
76 | movne r0, r0, ror #8 @ rotate checksum by 8 bits | |
77 | ldr pc, [sp], #4 @ return | |
78 | ||
79 | .not_aligned: tst buf, #1 @ odd address | |
80 | ldrneb td0, [buf], #1 @ make even | |
81 | subne len, len, #1 | |
82 | adcnes sum, sum, td0, put_byte_1 @ update checksum | |
83 | ||
84 | tst buf, #2 @ 32-bit aligned? | |
85 | #if __LINUX_ARM_ARCH__ >= 4 | |
86 | ldrneh td0, [buf], #2 @ make 32-bit aligned | |
87 | subne len, len, #2 | |
88 | #else | |
89 | ldrneb td0, [buf], #1 | |
90 | ldrneb ip, [buf], #1 | |
91 | subne len, len, #2 | |
92 | #ifndef __ARMEB__ | |
93 | orrne td0, td0, ip, lsl #8 | |
94 | #else | |
95 | orrne td0, ip, td0, lsl #8 | |
96 | #endif | |
97 | #endif | |
98 | adcnes sum, sum, td0 @ update checksum | |
99 | mov pc, lr | |
100 | ||
101 | ENTRY(csum_partial) | |
102 | stmfd sp!, {buf, lr} | |
103 | cmp len, #8 @ Ensure that we have at least | |
104 | blo .less8 @ 8 bytes to copy. | |
105 | ||
106 | adds sum, sum, #0 @ C = 0 | |
107 | tst buf, #3 @ Test destination alignment | |
108 | blne .not_aligned @ aligh destination, return here | |
109 | ||
110 | 1: bics ip, len, #31 | |
111 | beq 3f | |
112 | ||
113 | stmfd sp!, {r4 - r5} | |
114 | 2: ldmia buf!, {td0, td1, td2, td3} | |
115 | adcs sum, sum, td0 | |
116 | adcs sum, sum, td1 | |
117 | adcs sum, sum, td2 | |
118 | adcs sum, sum, td3 | |
119 | ldmia buf!, {td0, td1, td2, td3} | |
120 | adcs sum, sum, td0 | |
121 | adcs sum, sum, td1 | |
122 | adcs sum, sum, td2 | |
123 | adcs sum, sum, td3 | |
124 | sub ip, ip, #32 | |
125 | teq ip, #0 | |
126 | bne 2b | |
127 | ldmfd sp!, {r4 - r5} | |
128 | ||
129 | 3: tst len, #0x1c @ should not change C | |
130 | beq .less4 | |
131 | ||
132 | 4: ldr td0, [buf], #4 | |
133 | sub len, len, #4 | |
134 | adcs sum, sum, td0 | |
135 | tst len, #0x1c | |
136 | bne 4b | |
137 | b .less4 |