Message-Id: <20180718165545.1622-2-colyli@suse.de>
Date:   Thu, 19 Jul 2018 00:55:43 +0800
From:   Coly Li <colyli@...e.de>
To:     linux-kernel@...r.kernel.org
Cc:     linux-bcache@...r.kernel.org, linux-block@...r.kernel.org,
        Coly Li <colyli@...e.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Lyle <mlyle@...e.org>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Eric Biggers <ebiggers3@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH v4 1/3] lib: add crc64 calculation routines

This patch adds 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 talbe 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.

Signed-off-by: Coly Li <colyli@...e.de>
Co-developed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Reviewed-by: Hannes Reinecke <hare@...e.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Michael Lyle <mlyle@...e.org>
Cc: Kent Overstreet <kent.overstreet@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Kate Stewart <kstewart@...uxfoundation.org>
Cc: Eric Biggers <ebiggers3@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Randy Dunlap <rdunlap@...radead.org>
---
Changelog:
v4: Only keep crc64_be() in lib/crc64.c, move rested bcache specific
    stuffs back to bcache code.
    Other fixes from the review comments of v3
v3: More fixes for review comments of v2
    By review comments from Eric Biggers, current functions naming with
    'le' is misleading. Remove 'le' from the crc function names, and use
    u64 to replace __le64 in parameters and return values.
v2: Fix reivew comments of v1
v1: Initial version.

 include/linux/crc64.h | 11 +++++++
 lib/.gitignore        |  2 ++
 lib/Kconfig           |  8 +++++
 lib/Makefile          | 11 +++++++
 lib/crc64.c           | 56 +++++++++++++++++++++++++++++++++++
 lib/gen_crc64table.c  | 68 +++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 156 insertions(+)
 create mode 100644 include/linux/crc64.h
 create mode 100644 lib/crc64.c
 create mode 100644 lib/gen_crc64table.c

diff --git a/include/linux/crc64.h b/include/linux/crc64.h
new file mode 100644
index 000000000000..1fc9f0710c10
--- /dev/null
+++ b/include/linux/crc64.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * See lib/crc64.c for the related specification and polynomical 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 */
diff --git a/lib/.gitignore b/lib/.gitignore
index 09aae85418ab..f2a39c9e5485 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -2,5 +2,7 @@
 # Generated files
 #
 gen_crc32table
+gen_crc64table
 crc32table.h
+crc64table.h
 oid_registry_data.c
diff --git a/lib/Kconfig b/lib/Kconfig
index 706836ec314d..9c10b9852563 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -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
diff --git a/lib/Makefile b/lib/Makefile
index 90dc5520b784..40c215181687 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -102,6 +102,7 @@ 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
@@ -215,7 +216,9 @@ 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
 
@@ -225,6 +228,14 @@ 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
 #
diff --git a/lib/crc64.c b/lib/crc64.c
new file mode 100644
index 000000000000..d093298ba2c6
--- /dev/null
+++ b/lib/crc64.c
@@ -0,0 +1,56 @@
+// 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-driver 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@...e.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 for a new CRC computing, 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);
diff --git a/lib/gen_crc64table.c b/lib/gen_crc64table.c
new file mode 100644
index 000000000000..8296b0c3ea30
--- /dev/null
+++ b/lib/gen_crc64table.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generate lookup table for the talbe-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-driver CRC64 calculation.
+ *
+ * See lib/crc64.c for more information about which specification
+ * and polynomical arithmetic that gen_crc64table.c follows to
+ * generate the lookup table.
+ *
+ * Copyright 2018 SUSE Linux.
+ *   Author: Coly Li <colyli@...e.de>
+ */
+#include <inttypes.h>
+#include <stdio.h>
+
+#include <linux/swab.h>
+
+#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
+
+static int64_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;
+}
-- 
2.17.1

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