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This CRC64 variant comes from the NVME NVM Command Set Specification (https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0e-2024.07.29-Ratified.pdf). The "Rocksoft Model CRC Algorithm", published in 1993 and available at https://www.zlib.net/crc_v3.txt, is a generalized CRC algorithm that can calculate any variant of CRC, given a list of parameters such as polynomial, bit order, etc. It is not a CRC variant. The NVME NVM Command Set Specification has a table that gives the "Rocksoft Model Parameters" for the CRC variant it uses. When support for this CRC variant was added to Linux, this table seems to have been misinterpreted as naming the CRC variant the "Rocksoft" CRC. In fact, the table names the CRC variant as the "NVM Express 64b CRC". Most implementations of this CRC variant outside Linux have been calling it CRC64-NVME. Therefore, update Linux to match. While at it, remove the superfluous "update" from the function name, so crc64_rocksoft_update() is now just crc64_nvme(), matching most of the other CRC library functions. Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com> Acked-by: Keith Busch <kbusch@kernel.org> Link: https://lore.kernel.org/r/20250130035130.180676-4-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
79 lines
2.4 KiB
C
79 lines
2.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Normal 64-bit CRC calculation.
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*
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* This is a basic crc64 implementation following ECMA-182 specification,
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* which can be found from,
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* https://www.ecma-international.org/publications/standards/Ecma-182.htm
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*
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* Dr. Ross N. Williams has a great document to introduce the idea of CRC
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* algorithm, here the CRC64 code is also inspired by the table-driven
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* algorithm and detail example from this paper. This paper can be found
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* from,
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* http://www.ross.net/crc/download/crc_v3.txt
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*
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* crc64table[256] is the lookup table of a table-driven 64-bit CRC
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* calculation, which is generated by gen_crc64table.c in kernel build
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* time. The polynomial of crc64 arithmetic is from ECMA-182 specification
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* as well, which is defined as,
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*
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* x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
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* x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
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* x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
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* x^7 + x^4 + x + 1
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*
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* crc64nvmetable[256] uses the CRC64 polynomial from the NVME NVM Command Set
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* Specification and uses least-significant-bit first bit order:
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*
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* x^64 + x^63 + x^61 + x^59 + x^58 + x^56 + x^55 + x^52 + x^49 + x^48 + x^47 +
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* x^46 + x^44 + x^41 + x^37 + x^36 + x^34 + x^32 + x^31 + x^28 + x^26 + x^23 +
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* x^22 + x^19 + x^16 + x^13 + x^12 + x^10 + x^9 + x^6 + x^4 + x^3 + 1
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*
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* Copyright 2018 SUSE Linux.
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* Author: Coly Li <colyli@suse.de>
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/crc64.h>
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#include "crc64table.h"
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MODULE_DESCRIPTION("CRC64 calculations");
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MODULE_LICENSE("GPL v2");
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/**
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* crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
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* @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
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* or the previous crc64 value if computing incrementally.
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* @p: pointer to buffer over which CRC64 is run
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* @len: length of buffer @p
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*/
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u64 __pure crc64_be(u64 crc, const void *p, size_t len)
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{
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size_t i, t;
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const unsigned char *_p = p;
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for (i = 0; i < len; i++) {
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t = ((crc >> 56) ^ (*_p++)) & 0xFF;
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crc = crc64table[t] ^ (crc << 8);
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}
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return crc;
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}
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EXPORT_SYMBOL_GPL(crc64_be);
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u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len)
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{
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const unsigned char *_p = p;
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size_t i;
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crc = ~crc;
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for (i = 0; i < len; i++)
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crc = (crc >> 8) ^ crc64nvmetable[(crc & 0xff) ^ *_p++];
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return ~crc;
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}
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EXPORT_SYMBOL_GPL(crc64_nvme_generic);
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