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-rw-r--r--lib/gen_crc64table.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/lib/gen_crc64table.c b/lib/gen_crc64table.c
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+++ b/lib/gen_crc64table.c
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+// 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 <colyli@suse.de>
+ */
+#include <inttypes.h>
+#include <stdio.h>
+
+#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
+#define CRC64_ROCKSOFT_POLY 0x9A6C9329AC4BC9B5ULL
+
+static uint64_t crc64_table[256] = {0};
+static uint64_t crc64_rocksoft_table[256] = {0};
+
+static void generate_reflected_crc64_table(uint64_t table[256], uint64_t poly)
+{
+ uint64_t i, j, c, crc;
+
+ for (i = 0; i < 256; i++) {
+ crc = 0ULL;
+ c = i;
+
+ for (j = 0; j < 8; j++) {
+ if ((crc ^ (c >> j)) & 1)
+ crc = (crc >> 1) ^ poly;
+ else
+ crc >>= 1;
+ }
+ table[i] = crc;
+ }
+}
+
+static void generate_crc64_table(uint64_t table[256], uint64_t poly)
+{
+ 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) ^ poly;
+ else
+ crc <<= 1;
+ c <<= 1;
+ }
+
+ table[i] = crc;
+ }
+}
+
+static void output_table(uint64_t table[256])
+{
+ int i;
+
+ for (i = 0; i < 256; i++) {
+ printf("\t0x%016" PRIx64 "ULL", table[i]);
+ if (i & 0x1)
+ printf(",\n");
+ else
+ printf(", ");
+ }
+ printf("};\n");
+}
+
+static void print_crc64_tables(void)
+{
+ 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");
+ output_table(crc64_table);
+
+ printf("\nstatic const u64 ____cacheline_aligned crc64rocksofttable[256] = {\n");
+ output_table(crc64_rocksoft_table);
+}
+
+int main(int argc, char *argv[])
+{
+ generate_crc64_table(crc64_table, CRC64_ECMA182_POLY);
+ generate_reflected_crc64_table(crc64_rocksoft_table, CRC64_ROCKSOFT_POLY);
+ print_crc64_tables();
+ return 0;
+}