Commit feba04fd authored by Coly Li's avatar Coly Li Committed by Linus Torvalds
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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.

[colyli@suse.de: fix review comments from v4]
  Link: http://lkml.kernel.org/r/20180726053352.2781-2-colyli@suse.de
Link: http://lkml.kernel.org/r/20180718165545.1622-2-colyli@suse.de


Signed-off-by: default avatarColy Li <colyli@suse.de>
Co-developed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Michael Lyle <mlyle@lyle.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Noah Massey <noah.massey@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b15f5f1a

include/linux/crc64.h

0 → 100644
+11 −0
Original line number Diff line number Diff line 
/* 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

+2 −0
Original line number Diff line number Diff line
@@ -2,5 +2,7 @@ 
# Generated files

#

gen_crc32table

gen_crc64table

crc32table.h

crc64table.h

oid_registry_data.c

lib/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -170,6 +170,14 @@ config CRC32_BIT 


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

+11 −0
Original line number Diff line number Diff line
@@ -103,6 +103,7 @@ obj-$(CONFIG_CRC16) += crc16.o 
obj-$(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-$(CONFIG_CRC7)	+= crc7.o
@@ -217,7 +218,9 @@ obj-$(CONFIG_FONT_SUPPORT) += fonts/ 
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
@@ -227,6 +230,14 @@ quiet_cmd_crc32 = GEN $@ 
$(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

0 → 100644
+56 −0
Original line number Diff line number Diff line 
// 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 <colyli@suse.de>

 */



#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);

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