Re: [PATCH 2/2] crypto: qat - Don't move data inside output buffer

[Tadeusz Struk]

Hi Herbert,
On 08/13/2015 11:26 PM, Herbert Xu wrote:
> On Thu, Aug 13, 2015 at 11:14:11PM -0700, Tadeusz Struk wrote:
>>
>> Right, but we don't need that anymore.
> 
> Why not? If you reduce the size without moving the buffer wouldn't
> it begin with a bunch of zeroes and wouldn't you lose the real bytes
> at the end?

Yes, that was wrong, sorry. The reason I wanted to change it is that
the SW implementation can return a number with leading zeros.
This is because mpi_read_buffer() returns the whole thing.

Because the format of the module signature starts with 0x00, 0x01
the two implementations return a different thing.
For instance SW returned a 512 bytes number starting with 0x00, 0x01
and HW returned 511 bytes number without the 0x00 at the beginning.
Technically both are correct, but then the rsa_signture_verify()
needs to check for both cases, which is not ideal.
To make it return the same thing as SW we can do something like this:

---8<---

Allow for leading zeros in output to make it exactly the same as the
SW implementation.
Change memcpy to memmove because the copy is done within the same buffer.

diff --git a/drivers/crypto/qat/qat_common/qat_asym_algs.c 
b/drivers/crypto/qat/qat_common/qat_asym_algs.c
index fe352a6..cc450fa 100644
--- a/drivers/crypto/qat/qat_common/qat_asym_algs.c
+++ b/drivers/crypto/qat/qat_common/qat_asym_algs.c
@@ -118,7 +118,13 @@ static void qat_rsa_cb(struct icp_qat_fw_pke_resp *resp)
        struct device *dev = &GET_DEV(req->ctx->inst->accel_dev);
        int err = ICP_QAT_FW_PKE_RESP_PKE_STAT_GET(
                                resp->pke_resp_hdr.comn_resp_flags);
-       char *ptr = areq->dst;
+#if BYTES_PER_MPI_LIMB == 4
+       u32 *ptr = areq->dst;
+#elif BYTES_PER_MPI_LIMB == 8
+       u64 *ptr = areq->dst;
+#else
+#error please implement for this limb size.
+#endif
 
        err = (err == ICP_QAT_FW_COMN_STATUS_FLAG_OK) ? 0 : -EINVAL;
 
@@ -140,12 +146,12 @@ static void qat_rsa_cb(struct icp_qat_fw_pke_resp *resp)
        areq->dst_len = req->ctx->key_sz;
        /* Need to set the corect length of the output */
        while (!(*ptr) && areq->dst_len) {
-               areq->dst_len--;
+               areq->dst_len -= sizeof(*ptr);
                ptr++;
        }
 
        if (areq->dst_len != req->ctx->key_sz)
-               memcpy(areq->dst, ptr, areq->dst_len);
+               memmove(areq->dst, ptr, areq->dst_len);
 
        akcipher_request_complete(areq, err);
 }

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