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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/lib/crypto/mpi/mpi-mul.c
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/* mpi-mul.c  -  MPI functions

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 * Copyright (C) 1994, 1996, 1998, 2001, 2002,

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 *               2003 Free Software Foundation, Inc.

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 *

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 * This file is part of Libgcrypt.

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 *

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 * Note: This code is heavily based on the GNU MP Library.

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 *	 Actually it's the same code with only minor changes in the

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 *	 way the data is stored; this is to support the abstraction

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 *	 of an optional secure memory allocation which may be used

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 *	 to avoid revealing of sensitive data due to paging etc.

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 */

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#include <linux/export.h>

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#include "mpi-internal.h"

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int mpi_mul(MPI w, MPI u, MPI v)

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{

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	mpi_size_t usize, vsize, wsize;

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	mpi_ptr_t up, vp, wp;

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	mpi_limb_t cy;

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	int usign, vsign, sign_product;

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	int assign_wp = 0;

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	mpi_ptr_t tmp_limb = NULL;

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	int err = 0;

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	if (u->nlimbs < v->nlimbs) {

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		/* Swap U and V. */

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		usize = v->nlimbs;

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		usign = v->sign;

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		up    = v->d;

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		vsize = u->nlimbs;

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		vsign = u->sign;

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		vp    = u->d;

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	} else {

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		usize = u->nlimbs;

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		usign = u->sign;

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		up    = u->d;

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		vsize = v->nlimbs;

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		vsign = v->sign;

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		vp    = v->d;

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	}

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	sign_product = usign ^ vsign;

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	wp = w->d;

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	/* Ensure W has space enough to store the result.  */

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	wsize = usize + vsize;

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	if (w->alloced < wsize) {

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		if (wp == up || wp == vp) {

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			wp = mpi_alloc_limb_space(wsize);

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			if (!wp)

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				return -ENOMEM;

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			assign_wp = 1;

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		} else {

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			err = mpi_resize(w, wsize);

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			if (err)

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				return err;

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			wp = w->d;

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		}

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	} else { /* Make U and V not overlap with W.	*/

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		if (wp == up) {

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			/* W and U are identical.  Allocate temporary space for U. */

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			up = tmp_limb = mpi_alloc_limb_space(usize);

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			if (!up)

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				return -ENOMEM;

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			/* Is V identical too?  Keep it identical with U.  */

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			if (wp == vp)

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				vp = up;

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			/* Copy to the temporary space.  */

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			MPN_COPY(up, wp, usize);

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		} else if (wp == vp) {

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			/* W and V are identical.  Allocate temporary space for V. */

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			vp = tmp_limb = mpi_alloc_limb_space(vsize);

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			if (!vp)

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				return -ENOMEM;

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			/* Copy to the temporary space.  */

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			MPN_COPY(vp, wp, vsize);

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		}

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	}

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	if (!vsize)

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		wsize = 0;

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	else {

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		err = mpihelp_mul(wp, up, usize, vp, vsize, &cy);

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		if (err) {

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			if (assign_wp)

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				mpi_free_limb_space(wp);

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			goto free_tmp_limb;

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		}

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		wsize -= cy ? 0:1;

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	}

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	if (assign_wp)

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		mpi_assign_limb_space(w, wp, wsize);

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	w->nlimbs = wsize;

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	w->sign = sign_product;

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free_tmp_limb:

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	if (tmp_limb)

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		mpi_free_limb_space(tmp_limb);

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	return err;

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}

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EXPORT_SYMBOL_GPL(mpi_mul);

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int mpi_mulm(MPI w, MPI u, MPI v, MPI m)

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{

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	return mpi_mul(w, u, v) ?:

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	       mpi_tdiv_r(w, w, m);

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}

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EXPORT_SYMBOL_GPL(mpi_mulm);

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