Line data Source code
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 0 : 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 0 : const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];
79 : # if CRC_LE_BITS != 32
80 0 : const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
81 : # endif
82 : u32 q;
83 :
84 : /* Align it */
85 0 : if (unlikely((long)buf & 3 && len)) {
86 : do {
87 0 : DO_CRC(*buf++);
88 0 : } 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 0 : rem_len = len & 7;
96 0 : len = len >> 3;
97 : # endif
98 :
99 0 : b = (const u32 *)buf;
100 : # ifdef CONFIG_X86
101 : --b;
102 : for (i = 0; i < len; i++) {
103 : # else
104 0 : for (--b; len; --len) {
105 : # endif
106 0 : q = crc ^ *++b; /* use pre increment for speed */
107 : # if CRC_LE_BITS == 32
108 : crc = DO_CRC4;
109 : # else
110 0 : crc = DO_CRC8;
111 0 : q = *++b;
112 0 : crc ^= DO_CRC4;
113 : # endif
114 : }
115 0 : len = rem_len;
116 : /* And the last few bytes */
117 0 : if (len) {
118 0 : 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 0 : DO_CRC(*++p); /* use pre increment for speed */
125 0 : } while (--len);
126 : # endif
127 : }
128 0 : 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 0 : crc = (__force u32) __cpu_to_le32(crc);
179 0 : crc = crc32_body(crc, p, len, tab);
180 0 : 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 0 : u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len)
196 : {
197 0 : return crc32_le_generic(crc, p, len, crc32table_le, CRC32_POLY_LE);
198 : }
199 0 : u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
200 : {
201 0 : return crc32_le_generic(crc, p, len, 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 0 : u32 product = x & 1 ? y : 0;
219 : int i;
220 :
221 0 : for (i = 0; i < 31; i++) {
222 0 : product = (product >> 1) ^ (product & 1 ? modulus : 0);
223 0 : x >>= 1;
224 0 : 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 0 : static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len,
243 : u32 polynomial)
244 : {
245 0 : u32 power = polynomial; /* CRC of x^32 */
246 : int i;
247 :
248 : /* Shift up to 32 bits in the simple linear way */
249 0 : for (i = 0; i < 8 * (int)(len & 3); i++)
250 0 : crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0);
251 :
252 0 : len >>= 2;
253 0 : if (!len)
254 : return crc;
255 :
256 : for (;;) {
257 : /* "power" is x^(2^i), modulo the polynomial */
258 0 : if (len & 1)
259 : crc = gf2_multiply(crc, power, polynomial);
260 :
261 0 : len >>= 1;
262 0 : if (!len)
263 : break;
264 :
265 : /* Square power, advancing to x^(2^(i+1)) */
266 : power = gf2_multiply(power, power, polynomial);
267 : }
268 :
269 : return crc;
270 : }
271 :
272 0 : u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len)
273 : {
274 0 : return crc32_generic_shift(crc, len, CRC32_POLY_LE);
275 : }
276 :
277 0 : u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
278 : {
279 0 : 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 0 : 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 0 : crc = (__force u32) __cpu_to_be32(crc);
327 0 : crc = crc32_body(crc, p, len, tab);
328 0 : crc = __be32_to_cpu((__force __be32)crc);
329 : # endif
330 0 : 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 0 : u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len)
340 : {
341 0 : return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE);
342 : }
343 : #endif
344 : EXPORT_SYMBOL(crc32_be);
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