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Date:   Mon, 14 Mar 2022 16:33:39 +0100
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Subject: Re: [EXT] Re: [PATCH v5 4/5] crypto: caam - add in-kernel interface
 for blob generator
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To:     Pankaj Gupta <pankaj.gupta@nxp.com>,
        Jarkko Sakkinen <jarkko@kernel.org>
Cc:     David Gstir <david@sigma-star.at>,
        Aymen Sghaier <aymen.sghaier@nxp.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        David Howells <dhowells@redhat.com>,
        "keyrings@vger.kernel.org" <keyrings@vger.kernel.org>,
        Matthias Schiffer <matthias.schiffer@ew.tq-group.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Horia Geanta <horia.geanta@nxp.com>,
        Richard Weinberger <richard@nod.at>,
        James Morris <jmorris@namei.org>,
        Eric Biggers <ebiggers@kernel.org>,
        James Bottomley <jejb@linux.ibm.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        "tharvey@gateworks.com" <tharvey@gateworks.com>,
        Franck Lenormand <franck.lenormand@nxp.com>,
        Jan Luebbe <j.luebbe@pengutronix.de>,
        Sumit Garg <sumit.garg@linaro.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-security-module@vger.kernel.org" 
        <linux-security-module@vger.kernel.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>
References: <20220222195819.2313913-1-a.fatoum@pengutronix.de>
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 <a8cb99e0-fe01-2234-9839-fea28ca09f6d@pengutronix.de>
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From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
In-Reply-To: <DU2PR04MB863084B70239A69E4DE9D65B953E9@DU2PR04MB8630.eurprd04.prod.outlook.com>
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Hello Pankaj,

On 25.02.22 13:20, Pankaj Gupta wrote:
>>>> +static u32 *caam_blob_alloc_desc(size_t keymod_len) {
>>>> +    size_t len;
>>>> +
>>>> +    /* header + (key mod immediate) + 2x pointers + op */
>>>> +    len = 4 + (4 + ALIGN(keymod_len, 4)) + 2*(4 + 4 +
>>>> + CAAM_PTR_SZ_MAX) + 4;
>>>
>>> Nit: the amount of magic numbers is overwhelming here. I neither
>>> understand the statement nor how that comment should help me to
>> understand it.
>>
>> header              =  4
>> (key mod immediate) = (4 + ALIGN(keymod_len, 4))
>> 2x pointer          =  2 * (4 + 4 + CAAM_PTR_SZ_MAX)
>> op                  =  4
> 
> Instead of the function caam_blob_alloc_desc(), it will be great if the caller functions caam_encap_blob()/caam_encap_blob (), could add local array:
> uint32_t desc[CAAM_DESC_BYTES_MAX];

I just looked into this and placing desc on stack is not possible
as it is used for DMA inside caam_jr_enqueue().

Cheers,
Ahmad


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