1 files changed, 26 insertions, 29 deletions

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 823cf5f..7150e5c 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -237,16 +237,13 @@ EXPORT_SYMBOL_GPL(mpi_get_buffer);
  * @a:		a multi precision integer
  * @sgl:	scatterlist to write to. Needs to be at least
  *		mpi_get_size(a) long.
- * @nbytes:	in/out param - it has the be set to the maximum number of
- *		bytes that can be written to sgl. This has to be at least
- *		the size of the integer a. On return it receives the actual
- *		length of the data written on success or the data that would
- *		be written if buffer was too small.
+ * @nbytes:	the number of bytes to write.  Leading bytes will be
+ *		filled with zero.
  * @sign:	if not NULL, it will be set to the sign of a.
  *
  * Return:	0 on success or error code in case of error
  */
-int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
+int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,
 		     int *sign)
 {
 	u8 *p, *p2;
@@ -258,43 +255,44 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
 #error please implement for this limb size.
 #endif
 	unsigned int n = mpi_get_size(a);
-	int i, x, y = 0, lzeros, buf_len;
-
-	if (!nbytes)
-		return -EINVAL;
+	int i, x, buf_len;
 
 	if (sign)
 		*sign = a->sign;
 
-	lzeros = count_lzeros(a);
-
-	if (*nbytes < n - lzeros) {
-		*nbytes = n - lzeros;
+	if (nbytes < n)
 		return -EOVERFLOW;
-	}
 
-	*nbytes = n - lzeros;
 	buf_len = sgl->length;
 	p2 = sg_virt(sgl);
 
-	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
-			lzeros %= BYTES_PER_MPI_LIMB;
-		i >= 0; i--) {
+	while (nbytes > n) {
+		if (!buf_len) {
+			sgl = sg_next(sgl);
+			if (!sgl)
+				return -EINVAL;
+			buf_len = sgl->length;
+			p2 = sg_virt(sgl);
+		}
+
+		i = min_t(unsigned, nbytes - n, buf_len);
+		memset(p2, 0, i);
+		p2 += i;
+		buf_len -= i;
+		nbytes -= i;
+	}
+
+	for (i = a->nlimbs - 1; i >= 0; i--) {
 #if BYTES_PER_MPI_LIMB == 4
-		alimb = cpu_to_be32(a->d[i]);
+		alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;
 #elif BYTES_PER_MPI_LIMB == 8
-		alimb = cpu_to_be64(a->d[i]);
+		alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;
 #else
 #error please implement for this limb size.
 #endif
-		if (lzeros) {
-			y = lzeros;
-			lzeros = 0;
-		}
-
-		p = (u8 *)&alimb + y;
+		p = (u8 *)&alimb;
 
-		for (x = 0; x < sizeof(alimb) - y; x++) {
+		for (x = 0; x < sizeof(alimb); x++) {
 			if (!buf_len) {
 				sgl = sg_next(sgl);
 				if (!sgl)
@@ -305,7 +303,6 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
 			*p2++ = *p++;
 			buf_len--;
 		}
-		y = 0;
 	}
 	return 0;
 }