From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001
From: Duncan Wilkie <antigravityd@gmail.com>
Date: Sat, 18 Nov 2023 06:11:09 -0600
Subject: Initial commit.

---
 gmp-6.3.0/mpn/generic/sec_tabselect.c | 134 ++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 gmp-6.3.0/mpn/generic/sec_tabselect.c

(limited to 'gmp-6.3.0/mpn/generic/sec_tabselect.c')

diff --git a/gmp-6.3.0/mpn/generic/sec_tabselect.c b/gmp-6.3.0/mpn/generic/sec_tabselect.c
new file mode 100644
index 0000000..f50bdac
--- /dev/null
+++ b/gmp-6.3.0/mpn/generic/sec_tabselect.c
@@ -0,0 +1,134 @@
+/* mpn_sec_tabselect.
+
+Copyright 2007-2009, 2011, 2013, 2021 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include <stdio.h>
+#include "gmp-impl.h"
+
+#ifndef SEC_TABSELECT_METHOD
+#define SEC_TABSELECT_METHOD 1
+#endif
+
+/* Select entry `which' from table `tab', which has nents entries, each `n'
+   limbs.  Store the selected entry at rp.  Reads entire table to avoid
+   side-channel information leaks.  O(n*nents).  */
+
+#if SEC_TABSELECT_METHOD == 1
+void
+mpn_sec_tabselect (volatile mp_limb_t *rp, volatile const mp_limb_t *tab,
+		   mp_size_t n, mp_size_t nents, mp_size_t which)
+{
+  mp_size_t k, i;
+  mp_limb_t mask;
+  volatile const mp_limb_t *tp;
+
+  tp = tab;
+
+  /* Place first entry into result area. */
+  for (i = 0; i < n; i++)
+    rp[i] = tp[i];
+
+  /* Conditionally replace entry in result area by entry 1...(nents-1) using
+     masking trickery. */
+  for (k = 1; k < nents; k++)
+    {
+      /* Generate a mask using an expression which all compilers should compile
+	 into branch-free code.  The convoluted expression is designed to both
+	 allow mp_limb_t greater and mp_limb_t smaller than mp_size_t. */
+      mask = -(mp_limb_t) ((-(unsigned long) (which ^ k)) >> (BITS_PER_ULONG - 1));
+      tp += n;
+      for (i = 0; i < n; i++)
+	rp[i] = (rp[i] & mask) | (tp[i] & ~mask);
+    }
+}
+#endif
+
+#if SEC_TABSELECT_METHOD == 2
+void
+mpn_sec_tabselect (volatile mp_limb_t * restrict rp,
+		   volatile const mp_limb_t * restrict tab,
+		   mp_size_t n, mp_size_t nents, mp_size_t which)
+{
+  mp_size_t k, i;
+  mp_limb_t mask, r0, r1, r2, r3;
+  volatile const mp_limb_t * restrict tp;
+
+  if (n & 1)
+    {
+      tp = tab;
+      r0 = 0;
+      for (k = 0; k < nents; k++)
+	{
+	  mask = (mp_limb_t) ((-(unsigned long) (which ^ k)) >> (BITS_PER_ULONG - 1)) - 1;
+	  r0 += tp[0] & mask;
+	  tp += n;
+	}
+      rp[0] = r0;
+      rp += 1;
+      tab += 1;
+    }
+
+  if (n & 2)
+    {
+      tp = tab;
+      r0 = r1 = 0;
+      for (k = 0; k < nents; k++)
+	{
+	  mask = (mp_limb_t) ((-(unsigned long) (which ^ k)) >> (BITS_PER_ULONG - 1)) - 1;
+	  r0 += tp[0] & mask;
+	  r1 += tp[1] & mask;
+	  tp += n;
+	}
+      rp[0] = r0;
+      rp[1] = r1;
+      rp += 2;
+      tab += 2;
+    }
+
+  for (i = 0; i <= n - 4; i += 4)
+    {
+      tp = tab + i;
+      r0 = r1 = r2 = r3 = 0;
+      for (k = 0; k < nents; k++)
+	{
+	  mask = (mp_limb_t) ((-(unsigned long) (which ^ k)) >> (BITS_PER_ULONG - 1)) - 1;
+	  r0 += tp[0] & mask;
+	  r1 += tp[1] & mask;
+	  r2 += tp[2] & mask;
+	  r3 += tp[3] & mask;
+	  tp += n;
+	}
+      rp[0] = r0;
+      rp[1] = r1;
+      rp[2] = r2;
+      rp[3] = r3;
+      rp += 4;
+    }
+}
+#endif
-- 
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