crypto: Add generic 8-bit carry-less multiply routines

[mirror_qemu.git] / crypto / clmul.c

diff --git a/crypto/clmul.c b/crypto/clmul.c
new file mode 100644 (file)
index 0000000..82d873f
--- /dev/null
+++ b/crypto/clmul.c
@@ -0,0 +1,60 @@
+/*
+ * Carry-less multiply operations.
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * Copyright (C) 2023 Linaro, Ltd.
+ */
+
+#include "qemu/osdep.h"
+#include "crypto/clmul.h"
+
+uint64_t clmul_8x8_low(uint64_t n, uint64_t m)
+{
+    uint64_t r = 0;
+
+    for (int i = 0; i < 8; ++i) {
+        uint64_t mask = (n & 0x0101010101010101ull) * 0xff;
+        r ^= m & mask;
+        m = (m << 1) & 0xfefefefefefefefeull;
+        n >>= 1;
+    }
+    return r;
+}
+
+static uint64_t clmul_8x4_even_int(uint64_t n, uint64_t m)
+{
+    uint64_t r = 0;
+
+    for (int i = 0; i < 8; ++i) {
+        uint64_t mask = (n & 0x0001000100010001ull) * 0xffff;
+        r ^= m & mask;
+        n >>= 1;
+        m <<= 1;
+    }
+    return r;
+}
+
+uint64_t clmul_8x4_even(uint64_t n, uint64_t m)
+{
+    n &= 0x00ff00ff00ff00ffull;
+    m &= 0x00ff00ff00ff00ffull;
+    return clmul_8x4_even_int(n, m);
+}
+
+uint64_t clmul_8x4_odd(uint64_t n, uint64_t m)
+{
+    return clmul_8x4_even(n >> 8, m >> 8);
+}
+
+static uint64_t unpack_8_to_16(uint64_t x)
+{
+    return  (x & 0x000000ff)
+         | ((x & 0x0000ff00) << 8)
+         | ((x & 0x00ff0000) << 16)
+         | ((x & 0xff000000) << 24);
+}
+
+uint64_t clmul_8x4_packed(uint32_t n, uint32_t m)
+{
+    return clmul_8x4_even_int(unpack_8_to_16(n), unpack_8_to_16(m));
+}