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/crc32.txt 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
crc32_body(u32 crc,unsigned char const * buf,size_t len,const u32 (* tab)[256])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, 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,
198 (const u32 (*)[256])crc32table_le, CRC32_POLY_LE);
199 }
200 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
201 {
202 return crc32_le_generic(crc, p, len,
203 (const u32 (*)[256])crc32ctable_le, CRC32C_POLY_LE);
204 }
205 #endif
206 EXPORT_SYMBOL(crc32_le);
207 EXPORT_SYMBOL(__crc32c_le);
208
209 u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);
210 u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);
211
212 /*
213 * This multiplies the polynomials x and y modulo the given modulus.
214 * This follows the "little-endian" CRC convention that the lsbit
215 * represents the highest power of x, and the msbit represents x^0.
216 */
217 static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus)
218 {
219 u32 product = x & 1 ? y : 0;
220 int i;
221
222 for (i = 0; i < 31; i++) {
223 product = (product >> 1) ^ (product & 1 ? modulus : 0);
224 x >>= 1;
225 product ^= x & 1 ? y : 0;
226 }
227
228 return product;
229 }
230
231 /**
232 * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time
233 * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient)
234 * @len: The number of bytes. @crc is multiplied by x^(8*@len)
235 * @polynomial: The modulus used to reduce the result to 32 bits.
236 *
237 * It's possible to parallelize CRC computations by computing a CRC
238 * over separate ranges of a buffer, then summing them.
239 * This shifts the given CRC by 8*len bits (i.e. produces the same effect
240 * as appending len bytes of zero to the data), in time proportional
241 * to log(len).
242 */
243 static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len,
244 u32 polynomial)
245 {
246 u32 power = polynomial; /* CRC of x^32 */
247 int i;
248
249 /* Shift up to 32 bits in the simple linear way */
250 for (i = 0; i < 8 * (int)(len & 3); i++)
251 crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0);
252
253 len >>= 2;
254 if (!len)
255 return crc;
256
257 for (;;) {
258 /* "power" is x^(2^i), modulo the polynomial */
259 if (len & 1)
260 crc = gf2_multiply(crc, power, polynomial);
261
262 len >>= 1;
263 if (!len)
264 break;
265
266 /* Square power, advancing to x^(2^(i+1)) */
267 power = gf2_multiply(power, power, polynomial);
268 }
269
270 return crc;
271 }
272
273 u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len)
274 {
275 return crc32_generic_shift(crc, len, CRC32_POLY_LE);
276 }
277
278 u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
279 {
280 return crc32_generic_shift(crc, len, CRC32C_POLY_LE);
281 }
282 EXPORT_SYMBOL(crc32_le_shift);
283 EXPORT_SYMBOL(__crc32c_le_shift);
284
285 /**
286 * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
287 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
288 * other uses, or the previous crc32 value if computing incrementally.
289 * @p: pointer to buffer over which CRC32 is run
290 * @len: length of buffer @p
291 * @tab: big-endian Ethernet table
292 * @polynomial: CRC32 BE polynomial
293 */
294 static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p,
295 size_t len, const u32 (*tab)[256],
296 u32 polynomial)
297 {
298 #if CRC_BE_BITS == 1
299 int i;
300 while (len--) {
301 crc ^= *p++ << 24;
302 for (i = 0; i < 8; i++)
303 crc =
304 (crc << 1) ^ ((crc & 0x80000000) ? polynomial :
305 0);
306 }
307 # elif CRC_BE_BITS == 2
308 while (len--) {
309 crc ^= *p++ << 24;
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 crc = (crc << 2) ^ tab[0][crc >> 30];
314 }
315 # elif CRC_BE_BITS == 4
316 while (len--) {
317 crc ^= *p++ << 24;
318 crc = (crc << 4) ^ tab[0][crc >> 28];
319 crc = (crc << 4) ^ tab[0][crc >> 28];
320 }
321 # elif CRC_BE_BITS == 8
322 while (len--) {
323 crc ^= *p++ << 24;
324 crc = (crc << 8) ^ tab[0][crc >> 24];
325 }
326 # else
327 crc = (__force u32) __cpu_to_be32(crc);
328 crc = crc32_body(crc, p, len, tab);
329 crc = __be32_to_cpu((__force __be32)crc);
330 # endif
331 return crc;
332 }
333
334 #if CRC_LE_BITS == 1
335 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
336 {
337 return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE);
338 }
339 #else
340 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
341 {
342 return crc32_be_generic(crc, p, len,
343 (const u32 (*)[256])crc32table_be, CRC32_POLY_BE);
344 }
345 #endif
346 EXPORT_SYMBOL(crc32_be);
347
