lib/mpi: Add mpi sgl helpers

Add mpi_read_raw_from_sgl and mpi_write_to_sgl helpers.

Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 196 insertions, 0 deletions

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 95c52a95259e..c20ef27ad876 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -319,3 +319,199 @@ int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
         return 0;
 }
 EXPORT_SYMBOL_GPL(mpi_set_buffer);
+
+/**
+ * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
+ *
+ * This function works in the same way as the mpi_read_buffer, but it
+ * takes an sgl instead of u8 * buf.
+ *
+ * @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.
+ * @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 *sign)
+{
+        u8 *p, *p2;
+        mpi_limb_t alimb, alimb2;
+        unsigned int n = mpi_get_size(a);
+        int i, x, y = 0, lzeros = 0, buf_len;
+
+        if (!nbytes || *nbytes < n)
+                return -EINVAL;
+
+        if (sign)
+                *sign = a->sign;
+
+        p = (void *)&a->d[a->nlimbs] - 1;
+
+        for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
+                if (!*p)
+                        lzeros++;
+                else
+                        break;
+        }
+
+        *nbytes = n - lzeros;
+        buf_len = sgl->length;
+        p2 = sg_virt(sgl);
+
+        for (i = a->nlimbs - 1; i >= 0; i--) {
+                alimb = a->d[i];
+                p = (u8 *)&alimb2;
+#if BYTES_PER_MPI_LIMB == 4
+                *p++ = alimb >> 24;
+                *p++ = alimb >> 16;
+                *p++ = alimb >> 8;
+                *p++ = alimb;
+#elif BYTES_PER_MPI_LIMB == 8
+                *p++ = alimb >> 56;
+                *p++ = alimb >> 48;
+                *p++ = alimb >> 40;
+                *p++ = alimb >> 32;
+                *p++ = alimb >> 24;
+                *p++ = alimb >> 16;
+                *p++ = alimb >> 8;
+                *p++ = alimb;
+#else
+#error please implement for this limb size.
+#endif
+                if (lzeros > 0) {
+                        if (lzeros >= sizeof(alimb)) {
+                                p -= sizeof(alimb);
+                                continue;
+                        } else {
+                                mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
+                                mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
+                                                        + lzeros;
+                                *limb1 = *limb2;
+                                p -= lzeros;
+                                y = lzeros;
+                        }
+                        lzeros -= sizeof(alimb);
+                }
+
+                p = p - (sizeof(alimb) - y);
+
+                for (x = 0; x < sizeof(alimb) - y; x++) {
+                        if (!buf_len) {
+                                sgl = sg_next(sgl);
+                                if (!sgl)
+                                        return -EINVAL;
+                                buf_len = sgl->length;
+                                p2 = sg_virt(sgl);
+                        }
+                        *p2++ = *p++;
+                        buf_len--;
+                }
+                y = 0;
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
+
+/*
+ * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
+ *                           data from the sgl
+ *
+ * This function works in the same way as the mpi_read_raw_data, but it
+ * takes an sgl instead of void * buffer. i.e. it allocates
+ * a new MPI and reads the content of the sgl to the MPI.
+ *
+ * @sgl:        scatterlist to read from
+ * @len:        number of bytes to read
+ *
+ * Return:      Pointer to a new MPI or NULL on error
+ */
+MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
+{
+        struct scatterlist *sg;
+        int x, i, j, z, lzeros, ents;
+        unsigned int nbits, nlimbs, nbytes;
+        mpi_limb_t a;
+        MPI val = NULL;
+
+        lzeros = 0;
+        ents = sg_nents(sgl);
+
+        for_each_sg(sgl, sg, ents, i) {
+                const u8 *buff = sg_virt(sg);
+                int len = sg->length;
+
+                while (len-- && !*buff++)
+                        lzeros++;
+
+                if (len && *buff)
+                        break;
+
+                ents--;
+                lzeros = 0;
+        }
+
+        sgl = sg;
+
+        if (!ents)
+                nbytes = 0;
+        else
+                nbytes = len - lzeros;
+
+        nbits = nbytes * 8;
+        if (nbits > MAX_EXTERN_MPI_BITS) {
+                pr_info("MPI: mpi too large (%u bits)\n", nbits);
+                return NULL;
+        }
+
+        if (nbytes > 0)
+                nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
+        else
+                nbits = 0;
+
+        nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
+        val = mpi_alloc(nlimbs);
+        if (!val)
+                return NULL;
+
+        val->nbits = nbits;
+        val->sign = 0;
+        val->nlimbs = nlimbs;
+
+        if (nbytes == 0)
+                return val;
+
+        j = nlimbs - 1;
+        a = 0;
+        z = 0;
+        x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+        x %= BYTES_PER_MPI_LIMB;
+
+        for_each_sg(sgl, sg, ents, i) {
+                const u8 *buffer = sg_virt(sg) + lzeros;
+                int len = sg->length - lzeros;
+                int buf_shift = x;
+
+                if  (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
+                        len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);
+
+                for (; x < len + buf_shift; x++) {
+                        a <<= 8;
+                        a |= *buffer++;
+                        if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
+                                val->d[j--] = a;
+                                a = 0;
+                        }
+                }
+                z += x;
+                x = 0;
+                lzeros = 0;
+        }
+        return val;
+}
+EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);