+++ /dev/null
-/*
- * crc32.c --- CRC32 function
- *
- * Copyright (C) 2008 Theodore Ts'o.
- *
- * %Begin-Header%
- * This file may be redistributed under the terms of the GNU Public
- * License.
- * %End-Header%
- */
-
-/*
- * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com>
- * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks!
- * Code was from the public domain, copyright abandoned. Code was
- * subsequently included in the kernel, thus was re-licensed under the
- * GNU GPL v2.
- *
- * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com>
- * Same crc32 function was used in 5 other places in the kernel.
- * I made one version, and deleted the others.
- * There are various incantations of crc32(). Some use a seed of 0 or ~0.
- * Some xor at the end with ~0. The generic crc32() function takes
- * seed as an argument, and doesn't xor at the end. Then individual
- * users can do whatever they need.
- * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0.
- * fs/jffs2 uses seed 0, doesn't xor with ~0.
- * fs/partitions/efi.c uses seed ~0, xor's with ~0.
- *
- * This source code is licensed under the GNU General Public License,
- * Version 2. See the file COPYING for more details.
- */
-
-#include "config.h"
-#include <stdlib.h>
-#include <unistd.h>
-#include <string.h>
-#include <ctype.h>
-
-#ifdef UNITTEST
-#undef ENABLE_NLS
-#endif
-#include "e2fsck.h"
-
-#include "crc32defs.h"
-#if CRC_LE_BITS == 8
-#define tole(x) __constant_cpu_to_le32(x)
-#define tobe(x) __constant_cpu_to_be32(x)
-#else
-#define tole(x) (x)
-#define tobe(x) (x)
-#endif
-#include "crc32table.h"
-
-#ifdef UNITTEST
-
-/**
- * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32
- * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
- * other uses, or the previous crc32 value if computing incrementally.
- * @p: pointer to buffer over which CRC is run
- * @len: length of buffer @p
- */
-__u32 crc32_le(__u32 crc, unsigned char const *p, size_t len);
-
-#if CRC_LE_BITS == 1
-/*
- * In fact, the table-based code will work in this case, but it can be
- * simplified by inlining the table in ?: form.
- */
-
-__u32 crc32_le(__u32 crc, unsigned char const *p, size_t len)
-{
- int i;
- while (len--) {
- crc ^= *p++;
- for (i = 0; i < 8; i++)
- crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
- }
- return crc;
-}
-#else /* Table-based approach */
-
-__u32 crc32_le(__u32 crc, unsigned char const *p, size_t len)
-{
-# if CRC_LE_BITS == 8
- const __u32 *b =(__u32 *)p;
- const __u32 *tab = crc32table_le;
-
-# ifdef WORDS_BIGENDIAN
-# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
-# else
-# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
-# endif
-
- crc = __cpu_to_le32(crc);
- /* Align it */
- if(unlikely(((long)b)&3 && len)){
- do {
- __u8 *p = (__u8 *)b;
- DO_CRC(*p++);
- b = (void *)p;
- } while ((--len) && ((long)b)&3 );
- }
- if(likely(len >= 4)){
- /* load data 32 bits wide, xor data 32 bits wide. */
- size_t save_len = len & 3;
- len = len >> 2;
- --b; /* use pre increment below(*++b) for speed */
- do {
- crc ^= *++b;
- DO_CRC(0);
- DO_CRC(0);
- DO_CRC(0);
- DO_CRC(0);
- } while (--len);
- b++; /* point to next byte(s) */
- len = save_len;
- }
- /* And the last few bytes */
- if(len){
- do {
- __u8 *p = (__u8 *)b;
- DO_CRC(*p++);
- b = (void *)p;
- } while (--len);
- }
-
- return __le32_to_cpu(crc);
-#undef ENDIAN_SHIFT
-#undef DO_CRC
-
-# elif CRC_LE_BITS == 4
- while (len--) {
- crc ^= *p++;
- crc = (crc >> 4) ^ crc32table_le[crc & 15];
- crc = (crc >> 4) ^ crc32table_le[crc & 15];
- }
- return crc;
-# elif CRC_LE_BITS == 2
- while (len--) {
- crc ^= *p++;
- crc = (crc >> 2) ^ crc32table_le[crc & 3];
- crc = (crc >> 2) ^ crc32table_le[crc & 3];
- crc = (crc >> 2) ^ crc32table_le[crc & 3];
- crc = (crc >> 2) ^ crc32table_le[crc & 3];
- }
- return crc;
-# endif
-}
-#endif
-
-#endif /* UNITTEST */
-
-/**
- * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
- * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
- * other uses, or the previous crc32 value if computing incrementally.
- * @p: pointer to buffer over which CRC is run
- * @len: length of buffer @p
- */
-__u32 crc32_be(__u32 crc, unsigned char const *p, size_t len);
-
-#if CRC_BE_BITS == 1
-/*
- * In fact, the table-based code will work in this case, but it can be
- * simplified by inlining the table in ?: form.
- */
-
-__u32 crc32_be(__u32 crc, unsigned char const *p, size_t len)
-{
- int i;
- while (len--) {
- crc ^= *p++ << 24;
- for (i = 0; i < 8; i++)
- crc =
- (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE :
- 0);
- }
- return crc;
-}
-
-#else /* Table-based approach */
-__u32 crc32_be(__u32 crc, unsigned char const *p, size_t len)
-{
-# if CRC_BE_BITS == 8
- const __u32 *b =(const __u32 *)p;
- const __u32 *tab = crc32table_be;
-
-# ifdef WORDS_BIGENDIAN
-# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
-# else
-# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
-# endif
-
- crc = __cpu_to_be32(crc);
- /* Align it */
- if(unlikely(((long)b)&3 && len)){
- do {
- const __u8 *q = (const __u8 *)b;
- DO_CRC(*q++);
- b = (const __u32 *)q;
- } while ((--len) && ((long)b)&3 );
- }
- if(likely(len >= 4)){
- /* load data 32 bits wide, xor data 32 bits wide. */
- size_t save_len = len & 3;
- len = len >> 2;
- --b; /* use pre increment below(*++b) for speed */
- do {
- crc ^= *++b;
- DO_CRC(0);
- DO_CRC(0);
- DO_CRC(0);
- DO_CRC(0);
- } while (--len);
- b++; /* point to next byte(s) */
- len = save_len;
- }
- /* And the last few bytes */
- if(len){
- do {
- const __u8 *q = (const __u8 *)b;
- DO_CRC(*q++);
- b = (const void *)q;
- } while (--len);
- }
- return __be32_to_cpu(crc);
-#undef ENDIAN_SHIFT
-#undef DO_CRC
-
-# elif CRC_BE_BITS == 4
- while (len--) {
- crc ^= *p++ << 24;
- crc = (crc << 4) ^ crc32table_be[crc >> 28];
- crc = (crc << 4) ^ crc32table_be[crc >> 28];
- }
- return crc;
-# elif CRC_BE_BITS == 2
- while (len--) {
- crc ^= *p++ << 24;
- crc = (crc << 2) ^ crc32table_be[crc >> 30];
- crc = (crc << 2) ^ crc32table_be[crc >> 30];
- crc = (crc << 2) ^ crc32table_be[crc >> 30];
- crc = (crc << 2) ^ crc32table_be[crc >> 30];
- }
- return crc;
-# endif
-}
-#endif
-
-/*
- * A brief CRC tutorial.
- *
- * A CRC is a long-division remainder. You add the CRC to the message,
- * and the whole thing (message+CRC) is a multiple of the given
- * CRC polynomial. To check the CRC, you can either check that the
- * CRC matches the recomputed value, *or* you can check that the
- * remainder computed on the message+CRC is 0. This latter approach
- * is used by a lot of hardware implementations, and is why so many
- * protocols put the end-of-frame flag after the CRC.
- *
- * It's actually the same long division you learned in school, except that
- * - We're working in binary, so the digits are only 0 and 1, and
- * - When dividing polynomials, there are no carries. Rather than add and
- * subtract, we just xor. Thus, we tend to get a bit sloppy about
- * the difference between adding and subtracting.
- *
- * A 32-bit CRC polynomial is actually 33 bits long. But since it's
- * 33 bits long, bit 32 is always going to be set, so usually the CRC
- * is written in hex with the most significant bit omitted. (If you're
- * familiar with the IEEE 754 floating-point format, it's the same idea.)
- *
- * Note that a CRC is computed over a string of *bits*, so you have
- * to decide on the endianness of the bits within each byte. To get
- * the best error-detecting properties, this should correspond to the
- * order they're actually sent. For example, standard RS-232 serial is
- * little-endian; the most significant bit (sometimes used for parity)
- * is sent last. And when appending a CRC word to a message, you should
- * do it in the right order, matching the endianness.
- *
- * Just like with ordinary division, the remainder is always smaller than
- * the divisor (the CRC polynomial) you're dividing by. Each step of the
- * division, you take one more digit (bit) of the dividend and append it
- * to the current remainder. Then you figure out the appropriate multiple
- * of the divisor to subtract to being the remainder back into range.
- * In binary, it's easy - it has to be either 0 or 1, and to make the
- * XOR cancel, it's just a copy of bit 32 of the remainder.
- *
- * When computing a CRC, we don't care about the quotient, so we can
- * throw the quotient bit away, but subtract the appropriate multiple of
- * the polynomial from the remainder and we're back to where we started,
- * ready to process the next bit.
- *
- * A big-endian CRC written this way would be coded like:
- * for (i = 0; i < input_bits; i++) {
- * multiple = remainder & 0x80000000 ? CRCPOLY : 0;
- * remainder = (remainder << 1 | next_input_bit()) ^ multiple;
- * }
- * Notice how, to get at bit 32 of the shifted remainder, we look
- * at bit 31 of the remainder *before* shifting it.
- *
- * But also notice how the next_input_bit() bits we're shifting into
- * the remainder don't actually affect any decision-making until
- * 32 bits later. Thus, the first 32 cycles of this are pretty boring.
- * Also, to add the CRC to a message, we need a 32-bit-long hole for it at
- * the end, so we have to add 32 extra cycles shifting in zeros at the
- * end of every message,
- *
- * So the standard trick is to rearrage merging in the next_input_bit()
- * until the moment it's needed. Then the first 32 cycles can be precomputed,
- * and merging in the final 32 zero bits to make room for the CRC can be
- * skipped entirely.
- * This changes the code to:
- * for (i = 0; i < input_bits; i++) {
- * remainder ^= next_input_bit() << 31;
- * multiple = (remainder & 0x80000000) ? CRCPOLY : 0;
- * remainder = (remainder << 1) ^ multiple;
- * }
- * With this optimization, the little-endian code is simpler:
- * for (i = 0; i < input_bits; i++) {
- * remainder ^= next_input_bit();
- * multiple = (remainder & 1) ? CRCPOLY : 0;
- * remainder = (remainder >> 1) ^ multiple;
- * }
- *
- * Note that the other details of endianness have been hidden in CRCPOLY
- * (which must be bit-reversed) and next_input_bit().
- *
- * However, as long as next_input_bit is returning the bits in a sensible
- * order, we can actually do the merging 8 or more bits at a time rather
- * than one bit at a time:
- * for (i = 0; i < input_bytes; i++) {
- * remainder ^= next_input_byte() << 24;
- * for (j = 0; j < 8; j++) {
- * multiple = (remainder & 0x80000000) ? CRCPOLY : 0;
- * remainder = (remainder << 1) ^ multiple;
- * }
- * }
- * Or in little-endian:
- * for (i = 0; i < input_bytes; i++) {
- * remainder ^= next_input_byte();
- * for (j = 0; j < 8; j++) {
- * multiple = (remainder & 1) ? CRCPOLY : 0;
- * remainder = (remainder << 1) ^ multiple;
- * }
- * }
- * If the input is a multiple of 32 bits, you can even XOR in a 32-bit
- * word at a time and increase the inner loop count to 32.
- *
- * You can also mix and match the two loop styles, for example doing the
- * bulk of a message byte-at-a-time and adding bit-at-a-time processing
- * for any fractional bytes at the end.
- *
- * The only remaining optimization is to the byte-at-a-time table method.
- * Here, rather than just shifting one bit of the remainder to decide
- * in the correct multiple to subtract, we can shift a byte at a time.
- * This produces a 40-bit (rather than a 33-bit) intermediate remainder,
- * but again the multiple of the polynomial to subtract depends only on
- * the high bits, the high 8 bits in this case.
- *
- * The multiple we need in that case is the low 32 bits of a 40-bit
- * value whose high 8 bits are given, and which is a multiple of the
- * generator polynomial. This is simply the CRC-32 of the given
- * one-byte message.
- *
- * Two more details: normally, appending zero bits to a message which
- * is already a multiple of a polynomial produces a larger multiple of that
- * polynomial. To enable a CRC to detect this condition, it's common to
- * invert the CRC before appending it. This makes the remainder of the
- * message+crc come out not as zero, but some fixed non-zero value.
- *
- * The same problem applies to zero bits prepended to the message, and
- * a similar solution is used. Instead of starting with a remainder of
- * 0, an initial remainder of all ones is used. As long as you start
- * the same way on decoding, it doesn't make a difference.
- */
-
-#ifdef UNITTEST
-
-#include <stdlib.h>
-#include <stdio.h>
-
-const __u8 byte_rev_table[256] = {
- 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
- 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
- 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
- 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
- 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
- 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
- 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
- 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
- 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
- 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
- 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
- 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
- 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
- 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
- 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
- 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
- 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
- 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
- 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
- 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
- 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
- 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
- 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
- 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
- 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
- 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
- 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
- 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
- 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
- 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
- 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
- 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
-};
-
-static inline __u8 bitrev8(__u8 byte)
-{
- return byte_rev_table[byte];
-}
-
-static inline __u16 bitrev16(__u16 x)
-{
- return (bitrev8(x & 0xff) << 8) | bitrev8(x >> 8);
-}
-
-/**
- * bitrev32 - reverse the order of bits in a u32 value
- * @x: value to be bit-reversed
- */
-static __u32 bitrev32(__u32 x)
-{
- return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);
-}
-
-#if 0 /*Not used at present */
-
-static void
-buf_dump(char const *prefix, unsigned char const *buf, size_t len)
-{
- fputs(prefix, stdout);
- while (len--)
- printf(" %02x", *buf++);
- putchar('\n');
-
-}
-#endif
-
-static void bytereverse(unsigned char *buf, size_t len)
-{
- while (len--) {
- unsigned char x = bitrev8(*buf);
- *buf++ = x;
- }
-}
-
-static void random_garbage(unsigned char *buf, size_t len)
-{
- while (len--)
- *buf++ = (unsigned char) random();
-}
-
-#if 0 /* Not used at present */
-static void store_le(__u32 x, unsigned char *buf)
-{
- buf[0] = (unsigned char) x;
- buf[1] = (unsigned char) (x >> 8);
- buf[2] = (unsigned char) (x >> 16);
- buf[3] = (unsigned char) (x >> 24);
-}
-#endif
-
-static void store_be(__u32 x, unsigned char *buf)
-{
- buf[0] = (unsigned char) (x >> 24);
- buf[1] = (unsigned char) (x >> 16);
- buf[2] = (unsigned char) (x >> 8);
- buf[3] = (unsigned char) x;
-}
-
-/*
- * This checks that CRC(buf + CRC(buf)) = 0, and that
- * CRC commutes with bit-reversal. This has the side effect
- * of bytewise bit-reversing the input buffer, and returns
- * the CRC of the reversed buffer.
- */
-static __u32 test_step(__u32 init, unsigned char *buf, size_t len)
-{
- __u32 crc1, crc2;
- size_t i;
-
- crc1 = crc32_be(init, buf, len);
- store_be(crc1, buf + len);
- crc2 = crc32_be(init, buf, len + 4);
- if (crc2)
- printf("\nCRC cancellation fail: 0x%08x should be 0\n",
- crc2);
-
- for (i = 0; i <= len + 4; i++) {
- crc2 = crc32_be(init, buf, i);
- crc2 = crc32_be(crc2, buf + i, len + 4 - i);
- if (crc2)
- printf("\nCRC split fail: 0x%08x\n", crc2);
- }
-
- /* Now swap it around for the other test */
-
- bytereverse(buf, len + 4);
- init = bitrev32(init);
- crc2 = bitrev32(crc1);
- if (crc1 != bitrev32(crc2))
- printf("\nBit reversal fail: 0x%08x -> 0x%08x -> 0x%08x\n",
- crc1, crc2, bitrev32(crc2));
- crc1 = crc32_le(init, buf, len);
- if (crc1 != crc2)
- printf("\nCRC endianness fail: 0x%08x != 0x%08x\n", crc1,
- crc2);
- crc2 = crc32_le(init, buf, len + 4);
- if (crc2)
- printf("\nCRC cancellation fail: 0x%08x should be 0\n",
- crc2);
-
- for (i = 0; i <= len + 4; i++) {
- crc2 = crc32_le(init, buf, i);
- crc2 = crc32_le(crc2, buf + i, len + 4 - i);
- if (crc2)
- printf("\nCRC split fail: 0x%08x\n", crc2);
- }
-
- return crc1;
-}
-
-#define SIZE 64
-#define INIT1 0
-#define INIT2 0
-
-int main(int argc, char **argv)
-{
- unsigned char buf1[SIZE + 4];
- unsigned char buf2[SIZE + 4];
- unsigned char buf3[SIZE + 4];
- int i, j;
- __u32 crc1, crc2, crc3;
- int exit_status = 0;
-
- for (i = 0; i <= SIZE; i++) {
- printf("\rTesting length %d...", i);
- fflush(stdout);
- random_garbage(buf1, i);
- random_garbage(buf2, i);
- for (j = 0; j < i; j++)
- buf3[j] = buf1[j] ^ buf2[j];
-
- crc1 = test_step(INIT1, buf1, i);
- crc2 = test_step(INIT2, buf2, i);
- /* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */
- crc3 = test_step(INIT1 ^ INIT2, buf3, i);
- if (crc3 != (crc1 ^ crc2)) {
- printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n",
- crc3, crc1, crc2);
- exit_status++;
- }
- }
- printf("\nAll test complete. No failures expected.\n");
- return 0;
-}
-
-#endif /* UNITTEST */
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