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authorDavid Woodhouse <dwmw2@tylersburg.infradead.org>2009-07-13 10:35:12 (GMT)
committerDavid Woodhouse <David.Woodhouse@intel.com>2009-10-29 14:38:47 (GMT)
commitf5e70d0fe3ea990cfb3fc8d7f76a719adcb1e0b5 (patch)
tree1794eb51814228ff76f672a541100ad62dd791c9 /lib/raid6/mktables.c
parent17d857be649a21ca90008c6dc425d849fa83db5c (diff)
md: Factor out RAID6 algorithms into lib/
We'll want to use these in btrfs too. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'lib/raid6/mktables.c')
-rw-r--r--lib/raid6/mktables.c132
1 files changed, 132 insertions, 0 deletions
diff --git a/lib/raid6/mktables.c b/lib/raid6/mktables.c
new file mode 100644
index 0000000..3b15008
--- /dev/null
+++ b/lib/raid6/mktables.c
@@ -0,0 +1,132 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ * Copyright 2002-2007 H. Peter Anvin - All Rights Reserved
+ *
+ * This file is part of the Linux kernel, and is made available under
+ * the terms of the GNU General Public License version 2 or (at your
+ * option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * mktables.c
+ *
+ * Make RAID-6 tables. This is a host user space program to be run at
+ * compile time.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <time.h>
+
+static uint8_t gfmul(uint8_t a, uint8_t b)
+{
+ uint8_t v = 0;
+
+ while (b) {
+ if (b & 1)
+ v ^= a;
+ a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
+ b >>= 1;
+ }
+
+ return v;
+}
+
+static uint8_t gfpow(uint8_t a, int b)
+{
+ uint8_t v = 1;
+
+ b %= 255;
+ if (b < 0)
+ b += 255;
+
+ while (b) {
+ if (b & 1)
+ v = gfmul(v, a);
+ a = gfmul(a, a);
+ b >>= 1;
+ }
+
+ return v;
+}
+
+int main(int argc, char *argv[])
+{
+ int i, j, k;
+ uint8_t v;
+ uint8_t exptbl[256], invtbl[256];
+
+ printf("#include <linux/raid/pq.h>\n");
+
+ /* Compute multiplication table */
+ printf("\nconst u8 __attribute__((aligned(256)))\n"
+ "raid6_gfmul[256][256] =\n"
+ "{\n");
+ for (i = 0; i < 256; i++) {
+ printf("\t{\n");
+ for (j = 0; j < 256; j += 8) {
+ printf("\t\t");
+ for (k = 0; k < 8; k++)
+ printf("0x%02x,%c", gfmul(i, j + k),
+ (k == 7) ? '\n' : ' ');
+ }
+ printf("\t},\n");
+ }
+ printf("};\n");
+ printf("#ifdef __KERNEL__\n");
+ printf("EXPORT_SYMBOL(raid6_gfmul);\n");
+ printf("#endif\n");
+
+ /* Compute power-of-2 table (exponent) */
+ v = 1;
+ printf("\nconst u8 __attribute__((aligned(256)))\n"
+ "raid6_gfexp[256] =\n" "{\n");
+ for (i = 0; i < 256; i += 8) {
+ printf("\t");
+ for (j = 0; j < 8; j++) {
+ exptbl[i + j] = v;
+ printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
+ v = gfmul(v, 2);
+ if (v == 1)
+ v = 0; /* For entry 255, not a real entry */
+ }
+ }
+ printf("};\n");
+ printf("#ifdef __KERNEL__\n");
+ printf("EXPORT_SYMBOL(raid6_gfexp);\n");
+ printf("#endif\n");
+
+ /* Compute inverse table x^-1 == x^254 */
+ printf("\nconst u8 __attribute__((aligned(256)))\n"
+ "raid6_gfinv[256] =\n" "{\n");
+ for (i = 0; i < 256; i += 8) {
+ printf("\t");
+ for (j = 0; j < 8; j++) {
+ invtbl[i + j] = v = gfpow(i + j, 254);
+ printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
+ }
+ }
+ printf("};\n");
+ printf("#ifdef __KERNEL__\n");
+ printf("EXPORT_SYMBOL(raid6_gfinv);\n");
+ printf("#endif\n");
+
+ /* Compute inv(2^x + 1) (exponent-xor-inverse) table */
+ printf("\nconst u8 __attribute__((aligned(256)))\n"
+ "raid6_gfexi[256] =\n" "{\n");
+ for (i = 0; i < 256; i += 8) {
+ printf("\t");
+ for (j = 0; j < 8; j++)
+ printf("0x%02x,%c", invtbl[exptbl[i + j] ^ 1],
+ (j == 7) ? '\n' : ' ');
+ }
+ printf("};\n");
+ printf("#ifdef __KERNEL__\n");
+ printf("EXPORT_SYMBOL(raid6_gfexi);\n");
+ printf("#endif\n");
+
+ return 0;
+}

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