#include <intrin.h>
#endif
+/*
+ * GHASH is defined over elements of GF(2^128) with "full little-endian"
+ * representation: leftmost byte is least significant, and, within each
+ * byte, leftmost _bit_ is least significant. The natural ordering in
+ * x86 is "mixed little-endian": bytes are ordered from least to most
+ * significant, but bits within a byte are in most-to-least significant
+ * order. Going to full little-endian representation would require
+ * reversing bits within each byte, which is doable but expensive.
+ *
+ * Instead, we go to full big-endian representation, by swapping bytes
+ * around, which is done with a single _mm_shuffle_epi8() opcode (it
+ * comes with SSSE3; all CPU that offer pclmulqdq also have SSSE3). We
+ * can use a full big-endian representation because in a carryless
+ * multiplication, we have a nice bit reversal property:
+ *
+ * rev_128(x) * rev_128(y) = rev_255(x * y)
+ *
+ * So by using full big-endian, we still get the right result, except
+ * that it is right-shifted by 1 bit. The left-shift is relatively
+ * inexpensive, and it can be mutualised.
+ *
+ *
+ * Since SSE2 opcodes do not have facilities for shitfting full 128-bit
+ * values with bit precision, we have to break down values into 64-bit
+ * chunks. We number chunks from 0 to 3 in left to right order.
+ */
+
+/*
+ * From a 128-bit value kw, compute kx as the XOR of the two 64-bit
+ * halves of kw (into the right half of kx; left half is unspecified).
+ */
+#define BK(kw, kx) do { \
+ kx = _mm_xor_si128(kw, _mm_shuffle_epi32(kw, 0x0E)); \
+ } while (0)
+
+/*
+ * Combine two 64-bit values (k0:k1) into a 128-bit (kw) value and
+ * the XOR of the two values (kx).
+ */
+#define PBK(k0, k1, kw, kx) do { \
+ kw = _mm_unpacklo_epi64(k1, k0); \
+ kx = _mm_xor_si128(k0, k1); \
+ } while (0)
+
+/*
+ * Left-shift by 1 bit a 256-bit value (in four 64-bit words).
+ */
+#define SL_256(x0, x1, x2, x3) do { \
+ x0 = _mm_or_si128( \
+ _mm_slli_epi64(x0, 1), \
+ _mm_srli_epi64(x1, 63)); \
+ x1 = _mm_or_si128( \
+ _mm_slli_epi64(x1, 1), \
+ _mm_srli_epi64(x2, 63)); \
+ x2 = _mm_or_si128( \
+ _mm_slli_epi64(x2, 1), \
+ _mm_srli_epi64(x3, 63)); \
+ x3 = _mm_slli_epi64(x3, 1); \
+ } while (0)
+
+/*
+ * Perform reduction in GF(2^128). The 256-bit value is in x0..x3;
+ * result is written in x0..x1.
+ */
+#define REDUCE_F128(x0, x1, x2, x3) do { \
+ x1 = _mm_xor_si128( \
+ x1, \
+ _mm_xor_si128( \
+ _mm_xor_si128( \
+ x3, \
+ _mm_srli_epi64(x3, 1)), \
+ _mm_xor_si128( \
+ _mm_srli_epi64(x3, 2), \
+ _mm_srli_epi64(x3, 7)))); \
+ x2 = _mm_xor_si128( \
+ _mm_xor_si128( \
+ x2, \
+ _mm_slli_epi64(x3, 63)), \
+ _mm_xor_si128( \
+ _mm_slli_epi64(x3, 62), \
+ _mm_slli_epi64(x3, 57))); \
+ x0 = _mm_xor_si128( \
+ x0, \
+ _mm_xor_si128( \
+ _mm_xor_si128( \
+ x2, \
+ _mm_srli_epi64(x2, 1)), \
+ _mm_xor_si128( \
+ _mm_srli_epi64(x2, 2), \
+ _mm_srli_epi64(x2, 7)))); \
+ x1 = _mm_xor_si128( \
+ _mm_xor_si128( \
+ x1, \
+ _mm_slli_epi64(x2, 63)), \
+ _mm_xor_si128( \
+ _mm_slli_epi64(x2, 62), \
+ _mm_slli_epi64(x2, 57))); \
+ } while (0)
+
+/*
+ * Square value kw into (dw,dx).
+ */
+#define SQUARE_F128(kw, dw, dx) do { \
+ __m128i z0, z1, z2, z3; \
+ z1 = _mm_clmulepi64_si128(kw, kw, 0x11); \
+ z3 = _mm_clmulepi64_si128(kw, kw, 0x00); \
+ z0 = _mm_shuffle_epi32(z1, 0x0E); \
+ z2 = _mm_shuffle_epi32(z3, 0x0E); \
+ SL_256(z0, z1, z2, z3); \
+ REDUCE_F128(z0, z1, z2, z3); \
+ PBK(z0, z1, dw, dx); \
+ } while (0)
+
/* see bearssl_hash.h */
BR_TARGET("ssse3,pclmul")
void
br_ghash_pclmul(void *y, const void *h, const void *data, size_t len)
{
+ const unsigned char *buf1, *buf2;
+ unsigned char tmp[64];
+ size_t num4, num1;
+ __m128i yw, h1w, h1x;
+ __m128i byteswap_index;
+
/*
- * TODO: loop below processes one 16-bit word at a time. We
- * could parallelize, using:
- * ((y+x0)*h+x1)*h = (y+x0)*(h^2) + x1*h
- * i.e. precompute h^2, then handle two words at a time, mostly
- * in parallel (this may extend to more words as well...).
+ * We split data into two chunks. First chunk starts at buf1
+ * and contains num4 blocks of 64-byte values. Second chunk
+ * starts at buf2 and contains num1 blocks of 16-byte values.
+ * We want the first chunk to be as large as possible.
*/
+ buf1 = data;
+ num4 = len >> 6;
+ len &= 63;
+ buf2 = buf1 + (num4 << 6);
+ num1 = (len + 15) >> 4;
+ if ((len & 15) != 0) {
+ memcpy(tmp, buf2, len);
+ memset(tmp + len, 0, (num1 << 4) - len);
+ buf2 = tmp;
+ }
- const unsigned char *buf;
- __m128i yx, hx;
- __m128i h0, h1, h2;
- __m128i byteswap_index;
-
+ /*
+ * Constant value to perform endian conversion.
+ */
byteswap_index = _mm_set_epi8(
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
- yx = _mm_loadu_si128(y);
- hx = _mm_loadu_si128(h);
- yx = _mm_shuffle_epi8(yx, byteswap_index);
- hx = _mm_shuffle_epi8(hx, byteswap_index);
/*
- * We byte-swap y and h for full big-endian interpretation
- * (see below).
+ * Load y and h.
*/
+ yw = _mm_loadu_si128(y);
+ h1w = _mm_loadu_si128(h);
+ yw = _mm_shuffle_epi8(yw, byteswap_index);
+ h1w = _mm_shuffle_epi8(h1w, byteswap_index);
+ BK(h1w, h1x);
- h0 = hx;
- h1 = _mm_shuffle_epi32(hx, 0x0E);
- h2 = _mm_xor_si128(h0, h1);
-
- buf = data;
- while (len > 0) {
- __m128i x;
- __m128i t0, t1, t2, v0, v1, v2, v3;
- __m128i y0, y1, y2;
+ if (num4 > 0) {
+ __m128i h2w, h2x, h3w, h3x, h4w, h4x;
+ __m128i t0, t1, t2, t3;
/*
- * Load next 128-bit word. If there are not enough bytes
- * for the next word, we pad it with zeros (as per the
- * API for this function; it's also what is useful for
- * implementation of GCM).
+ * Compute h2 = h^2.
*/
- if (len >= 16) {
- x = _mm_loadu_si128((const void *)buf);
- buf += 16;
- len -= 16;
- } else {
- unsigned char tmp[16];
-
- memcpy(tmp, buf, len);
- memset(tmp + len, 0, (sizeof tmp) - len);
- x = _mm_loadu_si128((void *)tmp);
- len = 0;
- }
+ SQUARE_F128(h1w, h2w, h2x);
/*
- * Specification of GCM is basically "full little-endian",
- * i.e. leftmost bit is most significant; but decoding
- * performed by _mm_loadu_si128 is "mixed endian" (leftmost
- * _byte_ is least significant, but within each byte, the
- * leftmost _bit_ is most significant). We could reverse
- * bits in each byte; however, it is more efficient to
- * swap the bytes and thus emulate full big-endian
- * decoding.
- *
- * Big-endian works here because multiplication in
- * GF[2](X) is "carry-less", thereby allowing reversal:
- * if rev_n(x) consists in reversing the order of bits
- * in x, then:
- * rev_128(A)*rev_128(B) = rev_255(A*B)
- * so we can compute A*B by using rev_128(A) and rev_128(B),
- * and an extra shift at the end (because 255 != 256). Bit
- * reversal is exactly what happens when converting from
- * full little-endian to full big-endian.
+ * Compute h3 = h^3 = h*(h^2).
*/
- x = _mm_shuffle_epi8(x, byteswap_index);
- yx = _mm_xor_si128(yx, x);
+ t1 = _mm_clmulepi64_si128(h1w, h2w, 0x11);
+ t3 = _mm_clmulepi64_si128(h1w, h2w, 0x00);
+ t2 = _mm_xor_si128(_mm_clmulepi64_si128(h1x, h2x, 0x00),
+ _mm_xor_si128(t1, t3));
+ t0 = _mm_shuffle_epi32(t1, 0x0E);
+ t1 = _mm_xor_si128(t1, _mm_shuffle_epi32(t2, 0x0E));
+ t2 = _mm_xor_si128(t2, _mm_shuffle_epi32(t3, 0x0E));
+ SL_256(t0, t1, t2, t3);
+ REDUCE_F128(t0, t1, t2, t3);
+ PBK(t0, t1, h3w, h3x);
/*
- * We want the product to be broken down into four
- * 64-bit values, because there is no SSE* opcode that
- * can do a shift on a 128-bit value.
+ * Compute h4 = h^4 = (h^2)^2.
*/
- y0 = yx;
- y1 = _mm_shuffle_epi32(yx, 0x0E);
- y2 = _mm_xor_si128(y0, y1);
- t0 = _mm_clmulepi64_si128(y0, h0, 0x00);
- t1 = _mm_clmulepi64_si128(yx, hx, 0x11);
- t2 = _mm_clmulepi64_si128(y2, h2, 0x00);
- t2 = _mm_xor_si128(t2, _mm_xor_si128(t0, t1));
- v0 = t0;
- v1 = _mm_xor_si128(_mm_shuffle_epi32(t0, 0x0E), t2);
- v2 = _mm_xor_si128(t1, _mm_shuffle_epi32(t2, 0x0E));
- v3 = _mm_shuffle_epi32(t1, 0x0E);
+ SQUARE_F128(h2w, h4w, h4x);
- /*
- * Do the corrective 1-bit shift (255->256).
- */
- v3 = _mm_or_si128(
- _mm_slli_epi64(v3, 1),
- _mm_srli_epi64(v2, 63));
- v2 = _mm_or_si128(
- _mm_slli_epi64(v2, 1),
- _mm_srli_epi64(v1, 63));
- v1 = _mm_or_si128(
- _mm_slli_epi64(v1, 1),
- _mm_srli_epi64(v0, 63));
- v0 = _mm_slli_epi64(v0, 1);
+ while (num4 -- > 0) {
+ __m128i aw0, aw1, aw2, aw3;
+ __m128i ax0, ax1, ax2, ax3;
- /*
- * Perform polynomial reduction into GF(2^128).
- */
- v2 = _mm_xor_si128(
- v2,
- _mm_xor_si128(
+ aw0 = _mm_loadu_si128((void *)(buf1 + 0));
+ aw1 = _mm_loadu_si128((void *)(buf1 + 16));
+ aw2 = _mm_loadu_si128((void *)(buf1 + 32));
+ aw3 = _mm_loadu_si128((void *)(buf1 + 48));
+ aw0 = _mm_shuffle_epi8(aw0, byteswap_index);
+ aw1 = _mm_shuffle_epi8(aw1, byteswap_index);
+ aw2 = _mm_shuffle_epi8(aw2, byteswap_index);
+ aw3 = _mm_shuffle_epi8(aw3, byteswap_index);
+ buf1 += 64;
+
+ aw0 = _mm_xor_si128(aw0, yw);
+ BK(aw1, ax1);
+ BK(aw2, ax2);
+ BK(aw3, ax3);
+ BK(aw0, ax0);
+
+ t1 = _mm_xor_si128(
+ _mm_xor_si128(
+ _mm_clmulepi64_si128(aw0, h4w, 0x11),
+ _mm_clmulepi64_si128(aw1, h3w, 0x11)),
_mm_xor_si128(
- v0,
- _mm_srli_epi64(v0, 1)),
+ _mm_clmulepi64_si128(aw2, h2w, 0x11),
+ _mm_clmulepi64_si128(aw3, h1w, 0x11)));
+ t3 = _mm_xor_si128(
_mm_xor_si128(
- _mm_srli_epi64(v0, 2),
- _mm_srli_epi64(v0, 7))));
- v1 = _mm_xor_si128(
- _mm_xor_si128(
- v1,
- _mm_slli_epi64(v0, 63)),
- _mm_xor_si128(
- _mm_slli_epi64(v0, 62),
- _mm_slli_epi64(v0, 57)));
- v3 = _mm_xor_si128(
- v3,
- _mm_xor_si128(
+ _mm_clmulepi64_si128(aw0, h4w, 0x00),
+ _mm_clmulepi64_si128(aw1, h3w, 0x00)),
_mm_xor_si128(
- v1,
- _mm_srli_epi64(v1, 1)),
+ _mm_clmulepi64_si128(aw2, h2w, 0x00),
+ _mm_clmulepi64_si128(aw3, h1w, 0x00)));
+ t2 = _mm_xor_si128(
_mm_xor_si128(
- _mm_srli_epi64(v1, 2),
- _mm_srli_epi64(v1, 7))));
- v2 = _mm_xor_si128(
- _mm_xor_si128(
- v2,
- _mm_slli_epi64(v1, 63)),
- _mm_xor_si128(
- _mm_slli_epi64(v1, 62),
- _mm_slli_epi64(v1, 57)));
+ _mm_clmulepi64_si128(ax0, h4x, 0x00),
+ _mm_clmulepi64_si128(ax1, h3x, 0x00)),
+ _mm_xor_si128(
+ _mm_clmulepi64_si128(ax2, h2x, 0x00),
+ _mm_clmulepi64_si128(ax3, h1x, 0x00)));
+ t2 = _mm_xor_si128(t2, _mm_xor_si128(t1, t3));
+ t0 = _mm_shuffle_epi32(t1, 0x0E);
+ t1 = _mm_xor_si128(t1, _mm_shuffle_epi32(t2, 0x0E));
+ t2 = _mm_xor_si128(t2, _mm_shuffle_epi32(t3, 0x0E));
+ SL_256(t0, t1, t2, t3);
+ REDUCE_F128(t0, t1, t2, t3);
+ yw = _mm_unpacklo_epi64(t1, t0);
+ }
+ }
- /*
- * We reduced toward the high words (v2 and v3), which
- * are the new value for y.
- */
- yx = _mm_unpacklo_epi64(v2, v3);
+ while (num1 -- > 0) {
+ __m128i aw, ax;
+ __m128i t0, t1, t2, t3;
+
+ aw = _mm_loadu_si128((void *)buf2);
+ aw = _mm_shuffle_epi8(aw, byteswap_index);
+ buf2 += 16;
+
+ aw = _mm_xor_si128(aw, yw);
+ BK(aw, ax);
+
+ t1 = _mm_clmulepi64_si128(aw, h1w, 0x11);
+ t3 = _mm_clmulepi64_si128(aw, h1w, 0x00);
+ t2 = _mm_clmulepi64_si128(ax, h1x, 0x00);
+ t2 = _mm_xor_si128(t2, _mm_xor_si128(t1, t3));
+ t0 = _mm_shuffle_epi32(t1, 0x0E);
+ t1 = _mm_xor_si128(t1, _mm_shuffle_epi32(t2, 0x0E));
+ t2 = _mm_xor_si128(t2, _mm_shuffle_epi32(t3, 0x0E));
+ SL_256(t0, t1, t2, t3);
+ REDUCE_F128(t0, t1, t2, t3);
+ yw = _mm_unpacklo_epi64(t1, t0);
}
- yx = _mm_shuffle_epi8(yx, byteswap_index);
- _mm_storeu_si128(y, yx);
+ yw = _mm_shuffle_epi8(yw, byteswap_index);
+ _mm_storeu_si128(y, yw);
}
/*
projects / BearSSL / commitdiff