Re: [PATCH v5 2/8] lib/mpi: Extend the MPI library

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On 2020/7/10 21:12, Marcelo Henrique Cerri wrote:
Hi, Tianjia.

On Thu, Jul 09, 2020 at 04:40:09PM +0800, Tianjia Zhang wrote:
Expand the mpi library based on libgcrypt, and the ECC algorithm of
mpi based on libgcrypt requires these functions.
Some other algorithms will be developed based on mpi ecc, such as SM2.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
  include/linux/mpi.h    |  88 +++++++++++
  lib/mpi/Makefile       |   5 +
  lib/mpi/mpi-add.c      | 207 +++++++++++++++++++++++++
  lib/mpi/mpi-bit.c      | 251 ++++++++++++++++++++++++++++++
  lib/mpi/mpi-cmp.c      |  46 ++++--
  lib/mpi/mpi-div.c      | 238 +++++++++++++++++++++++++++++
  lib/mpi/mpi-internal.h |  53 +++++++
  lib/mpi/mpi-inv.c      | 143 ++++++++++++++++++
  lib/mpi/mpi-mod.c      | 155 +++++++++++++++++++
  lib/mpi/mpi-mul.c      |  94 ++++++++++++
  lib/mpi/mpicoder.c     | 336 +++++++++++++++++++++++++++++++++++++++++
  lib/mpi/mpih-div.c     | 294 ++++++++++++++++++++++++++++++++++++
  lib/mpi/mpih-mul.c     |  25 +++
  lib/mpi/mpiutil.c      | 204 +++++++++++++++++++++++++
  14 files changed, 2129 insertions(+), 10 deletions(-)
  create mode 100644 lib/mpi/mpi-add.c
  create mode 100644 lib/mpi/mpi-div.c
  create mode 100644 lib/mpi/mpi-inv.c
  create mode 100644 lib/mpi/mpi-mod.c
  create mode 100644 lib/mpi/mpi-mul.c

diff --git a/lib/mpi/mpi-add.c b/lib/mpi/mpi-add.c
new file mode 100644
index 000000000000..9afad7832737
--- /dev/null
+++ b/lib/mpi/mpi-add.c
@@ -0,0 +1,207 @@
+/* mpi-add.c  -  MPI functions
+ * Copyright (C) 1994, 1996, 1998, 2001, 2002,
+ *               2003 Free Software Foundation, Inc.
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ *	 Actually it's the same code with only minor changes in the
+ *	 way the data is stored; this is to support the abstraction
+ *	 of an optional secure memory allocation which may be used
+ *	 to avoid revealing of sensitive data due to paging etc.
+ */
+
+#include "mpi-internal.h"
+
+/****************
+ * Add the unsigned integer V to the mpi-integer U and store the
+ * result in W. U and V may be the same.
+ */
+void mpi_add_ui(MPI w, MPI u, unsigned long v)
+{
+	mpi_ptr_t wp, up;
+	mpi_size_t usize, wsize;
+	int usign, wsign;
+
+	usize = u->nlimbs;
+	usign = u->sign;
+	wsign = 0;
+
+	/* If not space for W (and possible carry), increase space.  */
+	wsize = usize + 1;
+	if (w->alloced < wsize)
+		mpi_resize(w, wsize);

You are ignoring the mpi_resize() return. I believe these new functions
need to return an int to indicate errors as mpi_powm() does.


Yes, of course.  Thanks for pointing it out.

Thanks,
Tianjia


+
+	/* These must be after realloc (U may be the same as W).  */
+	up = u->d;
+	wp = w->d;
+
+	if (!usize) {  /* simple */
+		wp[0] = v;
+		wsize = v ? 1:0;
+	} else if (!usign) {  /* mpi is not negative */
+		mpi_limb_t cy;
+		cy = mpihelp_add_1(wp, up, usize, v);
+		wp[usize] = cy;
+		wsize = usize + cy;
+	} else {
+		/* The signs are different.  Need exact comparison to determine
+		 * which operand to subtract from which.
+		 */
+		if (usize == 1 && up[0] < v) {
+			wp[0] = v - up[0];
+			wsize = 1;
+		} else {
+			mpihelp_sub_1(wp, up, usize, v);
+			/* Size can decrease with at most one limb. */
+			wsize = usize - (wp[usize-1] == 0);
+			wsign = 1;
+		}
+	}
+
+	w->nlimbs = wsize;
+	w->sign   = wsign;
+}
+




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