linux-kernel - Re: [EXT] Re: [PATCH v5 4/5] crypto: caam - add in-kernel interface for blob generator

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Message-ID: <7f1e4cbd-2d02-2345-493b-68ded3357f26@pengutronix.de>
Date:   Mon, 14 Mar 2022 16:33:39 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Pankaj Gupta <pankaj.gupta@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>
Cc:     David Gstir <david@...ma-star.at>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        Matthias Schiffer <matthias.schiffer@...tq-group.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Horia Geanta <horia.geanta@....com>,
        Richard Weinberger <richard@....at>,
        James Morris <jmorris@...ei.org>,
        Eric Biggers <ebiggers@...nel.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "tharvey@...eworks.com" <tharvey@...eworks.com>,
        Franck Lenormand <franck.lenormand@....com>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        Sumit Garg <sumit.garg@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [EXT] Re: [PATCH v5 4/5] crypto: caam - add in-kernel interface
 for blob generator

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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