cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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mpi-sub-ui.c (2322B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/* mpi-sub-ui.c - Subtract an unsigned integer from an MPI.
      3 *
      4 * Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 2015
      5 * Free Software Foundation, Inc.
      6 *
      7 * This file was based on the GNU MP Library source file:
      8 * https://gmplib.org/repo/gmp-6.2/file/510b83519d1c/mpz/aors_ui.h
      9 *
     10 * The GNU MP Library is free software; you can redistribute it and/or modify
     11 * it under the terms of either:
     12 *
     13 *   * the GNU Lesser General Public License as published by the Free
     14 *     Software Foundation; either version 3 of the License, or (at your
     15 *     option) any later version.
     16 *
     17 * or
     18 *
     19 *   * the GNU General Public License as published by the Free Software
     20 *     Foundation; either version 2 of the License, or (at your option) any
     21 *     later version.
     22 *
     23 * or both in parallel, as here.
     24 *
     25 * The GNU MP Library is distributed in the hope that it will be useful, but
     26 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     27 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
     28 * for more details.
     29 *
     30 * You should have received copies of the GNU General Public License and the
     31 * GNU Lesser General Public License along with the GNU MP Library.  If not,
     32 * see https://www.gnu.org/licenses/.
     33 */
     34
     35#include "mpi-internal.h"
     36
     37int mpi_sub_ui(MPI w, MPI u, unsigned long vval)
     38{
     39	if (u->nlimbs == 0) {
     40		if (mpi_resize(w, 1) < 0)
     41			return -ENOMEM;
     42		w->d[0] = vval;
     43		w->nlimbs = (vval != 0);
     44		w->sign = (vval != 0);
     45		return 0;
     46	}
     47
     48	/* If not space for W (and possible carry), increase space. */
     49	if (mpi_resize(w, u->nlimbs + 1))
     50		return -ENOMEM;
     51
     52	if (u->sign) {
     53		mpi_limb_t cy;
     54
     55		cy = mpihelp_add_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
     56		w->d[u->nlimbs] = cy;
     57		w->nlimbs = u->nlimbs + cy;
     58		w->sign = 1;
     59	} else {
     60		/* The signs are different.  Need exact comparison to determine
     61		 * which operand to subtract from which.
     62		 */
     63		if (u->nlimbs == 1 && u->d[0] < vval) {
     64			w->d[0] = vval - u->d[0];
     65			w->nlimbs = 1;
     66			w->sign = 1;
     67		} else {
     68			mpihelp_sub_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
     69			/* Size can decrease with at most one limb. */
     70			w->nlimbs = (u->nlimbs - (w->d[u->nlimbs - 1] == 0));
     71			w->sign = 0;
     72		}
     73	}
     74
     75	mpi_normalize(w);
     76	return 0;
     77}
     78EXPORT_SYMBOL_GPL(mpi_sub_ui);