unikernel/duniverse/mirage-crypto/ec/native/inversion_template.h

@@ -0,0 +1,61 @@
+#define MAKE_FN_NAME1(x,y) x ## y
+#define MAKE_FN_NAME(x,y) MAKE_FN_NAME1(x,y)
+
+#define PRECOMP MAKE_FN_NAME(CURVE_DESCRIPTION,_divstep_precomp)
+#define MSAT MAKE_FN_NAME(CURVE_DESCRIPTION,_msat)
+#define MONE MAKE_FN_NAME(CURVE_DESCRIPTION,_set_one)
+#define DIVSTEP MAKE_FN_NAME(CURVE_DESCRIPTION,_divstep)
+#define OPP MAKE_FN_NAME(CURVE_DESCRIPTION,_opp)
+#define MUL MAKE_FN_NAME(CURVE_DESCRIPTION,_mul)
+#define SZNZ MAKE_FN_NAME(CURVE_DESCRIPTION,_selectznz)
+
+#if LEN_PRIME < 46
+#define ITERATIONS (((49 * LEN_PRIME) + 80) / 17)
+#else
+#define ITERATIONS (((49 * LEN_PRIME) + 57) / 17)
+#endif
+
+#define SAT_LIMBS LIMBS + 1 /* we might need 2 more bits to represent m in twos complement */
+#define BYTES 8 * (((LEN_PRIME - 1) / 64) + 1)
+
+static void inverse(WORD out[LIMBS], WORD g[SAT_LIMBS]) {
+
+  WORD precomp[LIMBS];
+  PRECOMP(precomp);
+
+  WORD d = 1;
+  WORD f[SAT_LIMBS];
+  WORD v[LIMBS];
+  WORD r[LIMBS];
+  WORD out1;
+  WORD out2[SAT_LIMBS], out3[SAT_LIMBS], out4[LIMBS], out5[LIMBS];
+
+  MSAT(f);
+  MONE(r);
+  for (int j = 0; j < LIMBS; j++) v[j] = 0;
+
+  for (int i = 0; i < ITERATIONS - (ITERATIONS % 2); i+=2) {
+    DIVSTEP(&out1,out2,out3,out4,out5,d,f,g,v,r);
+    DIVSTEP(&d,f,g,v,r,out1,out2,out3,out4,out5);
+  }
+  if (ITERATIONS % 2) {
+    DIVSTEP(&out1,out2,out3,out4,out5,d,f,g,v,r);
+    for (int k = 0; k < LIMBS; k++) v[k] = out4[k];
+    for (int k = 0; k < SAT_LIMBS; k++) f[k] = out2[k];
+  }
+
+  WORD h[LIMBS];
+  OPP(h, v);
+  SZNZ(v, f[SAT_LIMBS -1 ] >> (WORDSIZE - 1), v, h);
+  MUL(out, v, precomp);
+
+  return;
+}
+
+static void inversion (WORD out[LIMBS], const WORD in[LIMBS]) {
+  WORD in_[SAT_LIMBS];
+  for (int i = 0; i < LIMBS; i++) in_[i] = in[i];
+  in_[LIMBS] = 0;
+  inverse(out, in_);
+  return;
+}