lib: add crc64 calculation routines

Patch series "add crc64 calculation as kernel library", v5.

This patchset adds basic implementation of crc64 calculation as a Linux
kernel library. Since bcache already does crc64 by itself, this patchset
also modifies bcache code to use the new crc64 library routine.

Currently bcache is the only user of crc64 calculation, another potential
user is bcachefs which is on the way to be in mainline kernel. Therefore
it makes sense to make crc64 calculation to be a public library.

bcache uses crc64 as storage checksum, if a change of crc lib routines
results an inconsistent result, the unmatched checksum may make bcache
'think' the on-disk is corrupted, such a change should be avoided or
detected as early as possible. Therefore a patch is being prepared which
adds a crc test framework, to check consistency of different calculations.

This patch (of 2):

Add the re-write crc64 calculation routines for Linux kernel. The CRC64
polynomical arithmetic follows ECMA-182 specification, inspired by CRC
paper of Dr. Ross N. Williams (see
http://www.ross.net/crc/download/crc_v3.txt) and other public domain
implementations.

All the changes work in this way,
- When Linux kernel is built, host program lib/gen_crc64table.c will be
compiled to lib/gen_crc64table and executed.
- The output of gen_crc64table execution is an array called as lookup
table (a.k.a POLY 0x42f0e1eba9ea369) which contain 256 64-bit long
numbers, this table is dumped into header file lib/crc64table.h.
- Then the header file is included by lib/crc64.c for normal 64bit crc
calculation.
- Function declaration of the crc64 calculation routines is placed in
include/linux/crc64.h

Currently bcache is the only user of crc64_be(), another potential user is
bcachefs which is on the way to be in mainline kernel. Therefore it makes
sense to move crc64 calculation into lib/crc64.c as public code.

[[e-mail]: fix review comments from v4]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Coly Li <[e-mail]>
Co-developed-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: Michael Lyle <[e-mail]>
Cc: Kent Overstreet <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Kate Stewart <[e-mail]>
Cc: Eric Biggers <[e-mail]>
Cc: Randy Dunlap <[e-mail]>
Cc: Noah Massey <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/crc64.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * See lib/crc64.c for the related specification and polynomial arithmetic.
+ */
+#ifndef _LINUX_CRC64_H
+#define _LINUX_CRC64_H
+
+#include <linux/types.h>
+
+u64 __pure crc64_be(u64 crc, const void *p, size_t len);
+#endif /* _LINUX_CRC64_H */

lib/.gitignore

···
 # Generated files
 #
 gen_crc32table
+gen_crc64table
 crc32table.h
+crc64table.h
 oid_registry_data.c

lib/Kconfig

···
 
 endchoice
 
+config CRC64
+	tristate "CRC64 functions"
+	help
+	  This option is provided for the case where no in-kernel-tree
+	  modules require CRC64 functions, but a module built outside
+	  the kernel tree does. Such modules that use library CRC64
+	  functions require M here.
+
 config CRC4
 	tristate "CRC4 functions"
 	help

lib/Makefile

···
 obj-$(CONFIG_CRC_T10DIF)+= crc-t10dif.o
 obj-$(CONFIG_CRC_ITU_T)	+= crc-itu-t.o
 obj-$(CONFIG_CRC32)	+= crc32.o
+obj-$(CONFIG_CRC64)     += crc64.o
 obj-$(CONFIG_CRC32_SELFTEST)	+= crc32test.o
 obj-$(CONFIG_CRC4)	+= crc4.o
 obj-$(CONFIG_CRC7)	+= crc7.o
···
 obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o
 
 hostprogs-y	:= gen_crc32table
+hostprogs-y	+= gen_crc64table
 clean-files	:= crc32table.h
+clean-files	+= crc64table.h
 
 $(obj)/crc32.o: $(obj)/crc32table.h
 
···
 
 $(obj)/crc32table.h: $(obj)/gen_crc32table
 	$(call cmd,crc32)
+
+$(obj)/crc64.o: $(obj)/crc64table.h
+
+quiet_cmd_crc64 = GEN     $@
+      cmd_crc64 = $< > $@
+
+$(obj)/crc64table.h: $(obj)/gen_crc64table
+	$(call cmd,crc64)
 
 #
 # Build a fast OID lookip registry from include/linux/oid_registry.h

lib/crc64.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Normal 64-bit CRC calculation.
+ *
+ * This is a basic crc64 implementation following ECMA-182 specification,
+ * which can be found from,
+ * http://www.ecma-international.org/publications/standards/Ecma-182.htm
+ *
+ * Dr. Ross N. Williams has a great document to introduce the idea of CRC
+ * algorithm, here the CRC64 code is also inspired by the table-driven
+ * algorithm and detail example from this paper. This paper can be found
+ * from,
+ * http://www.ross.net/crc/download/crc_v3.txt
+ *
+ * crc64table[256] is the lookup table of a table-driven 64-bit CRC
+ * calculation, which is generated by gen_crc64table.c in kernel build
+ * time. The polynomial of crc64 arithmetic is from ECMA-182 specification
+ * as well, which is defined as,
+ *
+ * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
+ * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
+ * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
+ * x^7 + x^4 + x + 1
+ *
+ * Copyright 2018 SUSE Linux.
+ *   Author: Coly Li <[e-mail]>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include "crc64table.h"
+
+MODULE_DESCRIPTION("CRC64 calculations");
+MODULE_LICENSE("GPL v2");
+
+/**
+ * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
+ * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
+	or the previous crc64 value if computing incrementally.
+ * @p: pointer to buffer over which CRC64 is run
+ * @len: length of buffer @p
+ */
+u64 __pure crc64_be(u64 crc, const void *p, size_t len)
+{
+	size_t i, t;
+
+	const unsigned char *_p = p;
+
+	for (i = 0; i < len; i++) {
+		t = ((crc >> 56) ^ (*_p++)) & 0xFF;
+		crc = crc64table[t] ^ (crc << 8);
+	}
+
+	return crc;
+}
+EXPORT_SYMBOL_GPL(crc64_be);

lib/gen_crc64table.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generate lookup table for the table-driven CRC64 calculation.
+ *
+ * gen_crc64table is executed in kernel build time and generates
+ * lib/crc64table.h. This header is included by lib/crc64.c for
+ * the table-driven CRC64 calculation.
+ *
+ * See lib/crc64.c for more information about which specification
+ * and polynomial arithmetic that gen_crc64table.c follows to
+ * generate the lookup table.
+ *
+ * Copyright 2018 SUSE Linux.
+ *   Author: Coly Li <[e-mail]>
+ */
+#include <inttypes.h>
+#include <stdio.h>
+
+#include <linux/swab.h>
+
+#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
+
+static uint64_t crc64_table[256] = {0};
+
+static void generate_crc64_table(void)
+{
+	uint64_t i, j, c, crc;
+
+	for (i = 0; i < 256; i++) {
+		crc = 0;
+		c = i << 56;
+
+		for (j = 0; j < 8; j++) {
+			if ((crc ^ c) & 0x8000000000000000ULL)
+				crc = (crc << 1) ^ CRC64_ECMA182_POLY;
+			else
+				crc <<= 1;
+			c <<= 1;
+		}
+
+		crc64_table[i] = crc;
+	}
+}
+
+static void print_crc64_table(void)
+{
+	int i;
+
+	printf("/* this file is generated - do not edit */\n\n");
+	printf("#include <linux/types.h>\n");
+	printf("#include <linux/cache.h>\n\n");
+	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
+	for (i = 0; i < 256; i++) {
+		printf("\t0x%016" PRIx64 "ULL", crc64_table[i]);
+		if (i & 0x1)
+			printf(",\n");
+		else
+			printf(", ");
+	}
+	printf("};\n");
+}
+
+int main(int argc, char *argv[])
+{
+	generate_crc64_table();
+	print_crc64_table();
+	return 0;
+}