1 | /* |
2 | * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin |
3 | * cleaned up code to current version of sparse and added the slicing-by-8 |
4 | * algorithm to the closely similar existing slicing-by-4 algorithm. |
5 | * |
6 | * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com> |
7 | * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! |
8 | * Code was from the public domain, copyright abandoned. Code was |
9 | * subsequently included in the kernel, thus was re-licensed under the |
10 | * GNU GPL v2. |
11 | * |
12 | * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com> |
13 | * Same crc32 function was used in 5 other places in the kernel. |
14 | * I made one version, and deleted the others. |
15 | * There are various incantations of crc32(). Some use a seed of 0 or ~0. |
16 | * Some xor at the end with ~0. The generic crc32() function takes |
17 | * seed as an argument, and doesn't xor at the end. Then individual |
18 | * users can do whatever they need. |
19 | * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. |
20 | * fs/jffs2 uses seed 0, doesn't xor with ~0. |
21 | * fs/partitions/efi.c uses seed ~0, xor's with ~0. |
22 | * |
23 | * This source code is licensed under the GNU General Public License, |
24 | * Version 2. See the file COPYING for more details. |
25 | */ |
26 | |
27 | /* see: Documentation/staging/crc32.rst for a description of algorithms */ |
28 | |
29 | #include <linux/crc32.h> |
30 | #include <linux/crc32poly.h> |
31 | #include <linux/module.h> |
32 | #include <linux/types.h> |
33 | #include <linux/sched.h> |
34 | #include "crc32defs.h" |
35 | |
36 | #if CRC_LE_BITS > 8 |
37 | # define tole(x) ((__force u32) cpu_to_le32(x)) |
38 | #else |
39 | # define tole(x) (x) |
40 | #endif |
41 | |
42 | #if CRC_BE_BITS > 8 |
43 | # define tobe(x) ((__force u32) cpu_to_be32(x)) |
44 | #else |
45 | # define tobe(x) (x) |
46 | #endif |
47 | |
48 | #include "crc32table.h" |
49 | |
50 | MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>" ); |
51 | MODULE_DESCRIPTION("Various CRC32 calculations" ); |
52 | MODULE_LICENSE("GPL" ); |
53 | |
54 | #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 |
55 | |
56 | /* implements slicing-by-4 or slicing-by-8 algorithm */ |
57 | static inline u32 __pure |
58 | crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) |
59 | { |
60 | # ifdef __LITTLE_ENDIAN |
61 | # define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8) |
62 | # define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \ |
63 | t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255]) |
64 | # define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \ |
65 | t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255]) |
66 | # else |
67 | # define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8) |
68 | # define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \ |
69 | t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255]) |
70 | # define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \ |
71 | t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255]) |
72 | # endif |
73 | const u32 *b; |
74 | size_t rem_len; |
75 | # ifdef CONFIG_X86 |
76 | size_t i; |
77 | # endif |
78 | const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; |
79 | # if CRC_LE_BITS != 32 |
80 | const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7]; |
81 | # endif |
82 | u32 q; |
83 | |
84 | /* Align it */ |
85 | if (unlikely((long)buf & 3 && len)) { |
86 | do { |
87 | DO_CRC(*buf++); |
88 | } while ((--len) && ((long)buf)&3); |
89 | } |
90 | |
91 | # if CRC_LE_BITS == 32 |
92 | rem_len = len & 3; |
93 | len = len >> 2; |
94 | # else |
95 | rem_len = len & 7; |
96 | len = len >> 3; |
97 | # endif |
98 | |
99 | b = (const u32 *)buf; |
100 | # ifdef CONFIG_X86 |
101 | --b; |
102 | for (i = 0; i < len; i++) { |
103 | # else |
104 | for (--b; len; --len) { |
105 | # endif |
106 | q = crc ^ *++b; /* use pre increment for speed */ |
107 | # if CRC_LE_BITS == 32 |
108 | crc = DO_CRC4; |
109 | # else |
110 | crc = DO_CRC8; |
111 | q = *++b; |
112 | crc ^= DO_CRC4; |
113 | # endif |
114 | } |
115 | len = rem_len; |
116 | /* And the last few bytes */ |
117 | if (len) { |
118 | u8 *p = (u8 *)(b + 1) - 1; |
119 | # ifdef CONFIG_X86 |
120 | for (i = 0; i < len; i++) |
121 | DO_CRC(*++p); /* use pre increment for speed */ |
122 | # else |
123 | do { |
124 | DO_CRC(*++p); /* use pre increment for speed */ |
125 | } while (--len); |
126 | # endif |
127 | } |
128 | return crc; |
129 | #undef DO_CRC |
130 | #undef DO_CRC4 |
131 | #undef DO_CRC8 |
132 | } |
133 | #endif |
134 | |
135 | |
136 | /** |
137 | * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II |
138 | * CRC32/CRC32C |
139 | * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other |
140 | * uses, or the previous crc32/crc32c value if computing incrementally. |
141 | * @p: pointer to buffer over which CRC32/CRC32C is run |
142 | * @len: length of buffer @p |
143 | * @tab: little-endian Ethernet table |
144 | * @polynomial: CRC32/CRC32c LE polynomial |
145 | */ |
146 | static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p, |
147 | size_t len, const u32 (*tab)[256], |
148 | u32 polynomial) |
149 | { |
150 | #if CRC_LE_BITS == 1 |
151 | int i; |
152 | while (len--) { |
153 | crc ^= *p++; |
154 | for (i = 0; i < 8; i++) |
155 | crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0); |
156 | } |
157 | # elif CRC_LE_BITS == 2 |
158 | while (len--) { |
159 | crc ^= *p++; |
160 | crc = (crc >> 2) ^ tab[0][crc & 3]; |
161 | crc = (crc >> 2) ^ tab[0][crc & 3]; |
162 | crc = (crc >> 2) ^ tab[0][crc & 3]; |
163 | crc = (crc >> 2) ^ tab[0][crc & 3]; |
164 | } |
165 | # elif CRC_LE_BITS == 4 |
166 | while (len--) { |
167 | crc ^= *p++; |
168 | crc = (crc >> 4) ^ tab[0][crc & 15]; |
169 | crc = (crc >> 4) ^ tab[0][crc & 15]; |
170 | } |
171 | # elif CRC_LE_BITS == 8 |
172 | /* aka Sarwate algorithm */ |
173 | while (len--) { |
174 | crc ^= *p++; |
175 | crc = (crc >> 8) ^ tab[0][crc & 255]; |
176 | } |
177 | # else |
178 | crc = (__force u32) __cpu_to_le32(crc); |
179 | crc = crc32_body(crc, buf: p, len, tab); |
180 | crc = __le32_to_cpu((__force __le32)crc); |
181 | #endif |
182 | return crc; |
183 | } |
184 | |
185 | #if CRC_LE_BITS == 1 |
186 | u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) |
187 | { |
188 | return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE); |
189 | } |
190 | u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) |
191 | { |
192 | return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE); |
193 | } |
194 | #else |
195 | u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) |
196 | { |
197 | return crc32_le_generic(crc, p, len, tab: crc32table_le, CRC32_POLY_LE); |
198 | } |
199 | u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) |
200 | { |
201 | return crc32_le_generic(crc, p, len, tab: crc32ctable_le, CRC32C_POLY_LE); |
202 | } |
203 | #endif |
204 | EXPORT_SYMBOL(crc32_le); |
205 | EXPORT_SYMBOL(__crc32c_le); |
206 | |
207 | u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le); |
208 | u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le); |
209 | u32 __pure crc32_be_base(u32, unsigned char const *, size_t) __alias(crc32_be); |
210 | |
211 | /* |
212 | * This multiplies the polynomials x and y modulo the given modulus. |
213 | * This follows the "little-endian" CRC convention that the lsbit |
214 | * represents the highest power of x, and the msbit represents x^0. |
215 | */ |
216 | static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus) |
217 | { |
218 | u32 product = x & 1 ? y : 0; |
219 | int i; |
220 | |
221 | for (i = 0; i < 31; i++) { |
222 | product = (product >> 1) ^ (product & 1 ? modulus : 0); |
223 | x >>= 1; |
224 | product ^= x & 1 ? y : 0; |
225 | } |
226 | |
227 | return product; |
228 | } |
229 | |
230 | /** |
231 | * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time |
232 | * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient) |
233 | * @len: The number of bytes. @crc is multiplied by x^(8*@len) |
234 | * @polynomial: The modulus used to reduce the result to 32 bits. |
235 | * |
236 | * It's possible to parallelize CRC computations by computing a CRC |
237 | * over separate ranges of a buffer, then summing them. |
238 | * This shifts the given CRC by 8*len bits (i.e. produces the same effect |
239 | * as appending len bytes of zero to the data), in time proportional |
240 | * to log(len). |
241 | */ |
242 | static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len, |
243 | u32 polynomial) |
244 | { |
245 | u32 power = polynomial; /* CRC of x^32 */ |
246 | int i; |
247 | |
248 | /* Shift up to 32 bits in the simple linear way */ |
249 | for (i = 0; i < 8 * (int)(len & 3); i++) |
250 | crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0); |
251 | |
252 | len >>= 2; |
253 | if (!len) |
254 | return crc; |
255 | |
256 | for (;;) { |
257 | /* "power" is x^(2^i), modulo the polynomial */ |
258 | if (len & 1) |
259 | crc = gf2_multiply(x: crc, y: power, modulus: polynomial); |
260 | |
261 | len >>= 1; |
262 | if (!len) |
263 | break; |
264 | |
265 | /* Square power, advancing to x^(2^(i+1)) */ |
266 | power = gf2_multiply(x: power, y: power, modulus: polynomial); |
267 | } |
268 | |
269 | return crc; |
270 | } |
271 | |
272 | u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len) |
273 | { |
274 | return crc32_generic_shift(crc, len, CRC32_POLY_LE); |
275 | } |
276 | |
277 | u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len) |
278 | { |
279 | return crc32_generic_shift(crc, len, CRC32C_POLY_LE); |
280 | } |
281 | EXPORT_SYMBOL(crc32_le_shift); |
282 | EXPORT_SYMBOL(__crc32c_le_shift); |
283 | |
284 | /** |
285 | * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 |
286 | * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for |
287 | * other uses, or the previous crc32 value if computing incrementally. |
288 | * @p: pointer to buffer over which CRC32 is run |
289 | * @len: length of buffer @p |
290 | * @tab: big-endian Ethernet table |
291 | * @polynomial: CRC32 BE polynomial |
292 | */ |
293 | static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p, |
294 | size_t len, const u32 (*tab)[256], |
295 | u32 polynomial) |
296 | { |
297 | #if CRC_BE_BITS == 1 |
298 | int i; |
299 | while (len--) { |
300 | crc ^= *p++ << 24; |
301 | for (i = 0; i < 8; i++) |
302 | crc = |
303 | (crc << 1) ^ ((crc & 0x80000000) ? polynomial : |
304 | 0); |
305 | } |
306 | # elif CRC_BE_BITS == 2 |
307 | while (len--) { |
308 | crc ^= *p++ << 24; |
309 | crc = (crc << 2) ^ tab[0][crc >> 30]; |
310 | crc = (crc << 2) ^ tab[0][crc >> 30]; |
311 | crc = (crc << 2) ^ tab[0][crc >> 30]; |
312 | crc = (crc << 2) ^ tab[0][crc >> 30]; |
313 | } |
314 | # elif CRC_BE_BITS == 4 |
315 | while (len--) { |
316 | crc ^= *p++ << 24; |
317 | crc = (crc << 4) ^ tab[0][crc >> 28]; |
318 | crc = (crc << 4) ^ tab[0][crc >> 28]; |
319 | } |
320 | # elif CRC_BE_BITS == 8 |
321 | while (len--) { |
322 | crc ^= *p++ << 24; |
323 | crc = (crc << 8) ^ tab[0][crc >> 24]; |
324 | } |
325 | # else |
326 | crc = (__force u32) __cpu_to_be32(crc); |
327 | crc = crc32_body(crc, buf: p, len, tab); |
328 | crc = __be32_to_cpu((__force __be32)crc); |
329 | # endif |
330 | return crc; |
331 | } |
332 | |
333 | #if CRC_BE_BITS == 1 |
334 | u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) |
335 | { |
336 | return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE); |
337 | } |
338 | #else |
339 | u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) |
340 | { |
341 | return crc32_be_generic(crc, p, len, tab: crc32table_be, CRC32_POLY_BE); |
342 | } |
343 | #endif |
344 | EXPORT_SYMBOL(crc32_be); |
345 | |