[PATCH RFC v4 1/4] MPILIB: add mpi_read_buf(), mpi_copy() and mpi_get_size() helpers
From: Tadeusz Struk
Date: Thu Jun 11 2015 - 15:05:47 EST
Added a mpi_read_buf() helper function to export MPI to a buf provided by
the user, and a mpi_get_size() helper, that tells the user how big the buf is.
Implemented mpi_copy(), which was declared in mpi.h, but never implemented.
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
---
include/linux/mpi.h | 3 ++
lib/mpi/mpicoder.c | 86 ++++++++++++++++++++++++++++++++++++++++-----------
lib/mpi/mpiutil.c | 47 ++++++++++++++++++++++++++++
3 files changed, 117 insertions(+), 19 deletions(-)
diff --git a/include/linux/mpi.h b/include/linux/mpi.h
index 5af1b81..5e55fd0 100644
--- a/include/linux/mpi.h
+++ b/include/linux/mpi.h
@@ -73,6 +73,7 @@ int mpi_set_ui(MPI w, ulong u);
MPI mpi_alloc_set_ui(unsigned long u);
void mpi_m_check(MPI a);
void mpi_swap(MPI a, MPI b);
+unsigned int mpi_get_size(MPI a);
/*-- mpicoder.c --*/
MPI do_encode_md(const void *sha_buffer, unsigned nbits);
@@ -81,6 +82,8 @@ MPI mpi_read_from_buffer(const void *buffer, unsigned *ret_nread);
int mpi_fromstr(MPI val, const char *str);
u32 mpi_get_keyid(MPI a, u32 *keyid);
void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign);
+int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
+ int *sign);
void *mpi_get_secure_buffer(MPI a, unsigned *nbytes, int *sign);
int mpi_set_buffer(MPI a, const void *buffer, unsigned nbytes, int sign);
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 4cc6442..f48b028 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -128,28 +128,36 @@ leave:
}
EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
-/****************
- * Return an allocated buffer with the MPI (msb first).
- * NBYTES receives the length of this buffer. Caller must free the
- * return string (This function does return a 0 byte buffer with NBYTES
- * set to zero if the value of A is zero. If sign is not NULL, it will
- * be set to the sign of the A.
+/**
+ * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
+ *
+ * @a: a multi precision integer
+ * @buf: bufer to which the output will be written to. Needs to be at
+ * leaset mpi_get_size(a) long.
+ * @buf_len: size of the buf.
+ * @nbytes: 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
*/
-void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
+ int *sign)
{
- uint8_t *p, *buffer;
+ uint8_t *p;
mpi_limb_t alimb;
+ unsigned int n = mpi_get_size(a);
int i;
- unsigned int n;
+
+ if (buf_len < n || !buf)
+ return -EINVAL;
if (sign)
*sign = a->sign;
- *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
- if (!n)
- n++; /* avoid zero length allocation */
- p = buffer = kmalloc(n, GFP_KERNEL);
- if (!p)
- return NULL;
+
+ if (nbytes)
+ *nbytes = n;
+
+ p = buf;
for (i = a->nlimbs - 1; i >= 0; i--) {
alimb = a->d[i];
@@ -171,15 +179,55 @@ void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
#error please implement for this limb size.
#endif
}
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_read_buffer);
+
+/*
+ * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
+ * Caller must free the return string.
+ * This function does return a 0 byte buffer with nbytes set to zero if the
+ * value of A is zero.
+ *
+ * @a: a multi precision integer.
+ * @nbytes: receives the length of this buffer.
+ * @sign: if not NULL, it will be set to the sign of the a.
+ *
+ * Return: Pointer to MPI buffer or NULL on error
+ */
+void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+{
+ uint8_t *buf, *p;
+ int n, ret;
+
+ if (!nbytes)
+ return NULL;
+
+ n = mpi_get_size(a);
+
+ if (!n)
+ n++;
+
+ buf = kmalloc(n, GFP_KERNEL);
+
+ if (!buf)
+ return NULL;
+
+ ret = mpi_read_buffer(a, buf, n, nbytes, sign);
+
+ if (ret) {
+ kfree(buf);
+ return NULL;
+ }
/* this is sub-optimal but we need to do the shift operation
* because the caller has to free the returned buffer */
- for (p = buffer; !*p && *nbytes; p++, --*nbytes)
+ for (p = buf; !*p && *nbytes; p++, --*nbytes)
;
- if (p != buffer)
- memmove(buffer, p, *nbytes);
+ if (p != buf)
+ memmove(buf, p, *nbytes);
- return buffer;
+ return buf;
}
EXPORT_SYMBOL_GPL(mpi_get_buffer);
diff --git a/lib/mpi/mpiutil.c b/lib/mpi/mpiutil.c
index bf076d2..ee078e2 100644
--- a/lib/mpi/mpiutil.c
+++ b/lib/mpi/mpiutil.c
@@ -54,6 +54,40 @@ MPI mpi_alloc(unsigned nlimbs)
}
EXPORT_SYMBOL_GPL(mpi_alloc);
+/**
+ * mpi_copy() - allocates a new MPI as exact copy of a.
+ *
+ * @copy: pointer to an MPI in which the copy will be stored
+ * @a: A multi precision integer for which we want to do a copy
+ *
+ * Return: 0 on success or err
+ */
+int mpi_copy(MPI *copy, MPI a)
+{
+ int ret = 0;
+
+ if (!copy)
+ return -EINVAL;
+
+ if (a) {
+ *copy = mpi_alloc(a->nlimbs);
+ if (*copy) {
+ memcpy((*copy)->d, a->d, a->nlimbs *
+ sizeof(mpi_limb_t));
+ (*copy)->nlimbs = a->nlimbs;
+ (*copy)->sign = a->sign;
+ (*copy)->flags = a->flags;
+ (*copy)->nbits = a->nbits;
+ } else {
+ ret = -ENOMEM;
+ }
+ } else {
+ *copy = NULL;
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(mpi_copy);
+
mpi_ptr_t mpi_alloc_limb_space(unsigned nlimbs)
{
size_t len = nlimbs * sizeof(mpi_limb_t);
@@ -122,5 +156,18 @@ void mpi_free(MPI a)
}
EXPORT_SYMBOL_GPL(mpi_free);
+/**
+ * mpi_get_size() - returns max size required to store the number
+ *
+ * @a: A multi precision integer for which we want to allocate a bufer
+ *
+ * Return: size required to store the number
+ */
+unsigned int mpi_get_size(MPI a)
+{
+ return a->nlimbs * BYTES_PER_MPI_LIMB;
+}
+EXPORT_SYMBOL_GPL(mpi_get_size);
+
MODULE_DESCRIPTION("Multiprecision maths library");
MODULE_LICENSE("GPL");
--
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