linux-kernel - RE: [PATCH] crypto: inside-secure - fix type of buffer in eip197_write

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Date:   Thu, 17 Oct 2019 17:14:14 +0000
From:   Pascal Van Leeuwen <pvanleeuwen@...imatrix.com>
To:     "Ben Dooks (Codethink)" <ben.dooks@...ethink.co.uk>,
        "linux-kernel@...ts.codethink.co.uk" 
        <linux-kernel@...ts.codethink.co.uk>
CC:     Antoine Tenart <antoine.tenart@...tlin.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] crypto: inside-secure - fix type of buffer in
 eip197_write_firmware

> -----Original Message-----
> From: linux-crypto-owner@...r.kernel.org <linux-crypto-owner@...r.kernel.org> On Behalf Of Ben
> Dooks (Codethink)
> Sent: Wednesday, October 16, 2019 1:50 PM
> To: linux-kernel@...ts.codethink.co.uk
> Cc: Ben Dooks (Codethink) <ben.dooks@...ethink.co.uk>; Antoine Tenart
> <antoine.tenart@...tlin.com>; Herbert Xu <herbert@...dor.apana.org.au>; David S. Miller
> <davem@...emloft.net>; linux-crypto@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] crypto: inside-secure - fix type of buffer in eip197_write_firmware
> 
> In eip197_write_firmware() the firmware buffer is sent using
> writel(be32_to_cpu(),,,) this produces a number of warnings.
> 
> Note, should this really be cpu_to_be32()  ?
> 
No, it should certainly not be cpu_to_be32() since the HW itself is most
definitely little endian, so that would not make sense to me.

Actually, I don't think either solution would be correct on a big-endian
CPU. But I don't have any big-endian CPU available to test that theory.

What I believe must happen is that the bytes must *always* be swapped 
here, regardless of the endianness of the CPU. And with a little-endian
CPU, be32_to_cpu() coincidentally always does that.

Basically, what we need here is: read a dword (32 bits) from the memory
subsystem and write it back to the memory subsystem with bytes reversed.

Does the kernel have any dedicated function for just always swapping?

Anyway: NACK on this patch for now due to this.

> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> drivers/crypto/inside-secure/safexcel.c:306:17: warning: cast to restricted __be32
> 
> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
> ---
> Cc: Antoine Tenart <antoine.tenart@...tlin.com>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: linux-crypto@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/crypto/inside-secure/safexcel.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/inside-secure/safexcel.c b/drivers/crypto/inside-secure/safexcel.c
> index 223d1bfdc7e6..dd33f6dda295 100644
> --- a/drivers/crypto/inside-secure/safexcel.c
> +++ b/drivers/crypto/inside-secure/safexcel.c
> @@ -298,13 +298,13 @@ static void eip197_init_firmware(struct safexcel_crypto_priv *priv)
>  static int eip197_write_firmware(struct safexcel_crypto_priv *priv,
>  				  const struct firmware *fw)
>  {
> -	const u32 *data = (const u32 *)fw->data;
> +	const __be32 *data = (const __be32 *)fw->data;
>  	int i;
> 
>  	/* Write the firmware */
> -	for (i = 0; i < fw->size / sizeof(u32); i++)
> +	for (i = 0; i < fw->size / sizeof(__be32); i++)
>  		writel(be32_to_cpu(data[i]),
> -		       priv->base + EIP197_CLASSIFICATION_RAMS + i * sizeof(u32));
> +		       priv->base + EIP197_CLASSIFICATION_RAMS + i * sizeof(__be32));
> 
>  	/* Exclude final 2 NOPs from size */
>  	return i - EIP197_FW_TERMINAL_NOPS;
> --
> 2.23.0

Regards,
Pascal van Leeuwen
Silicon IP Architect, Multi-Protocol Engines @ Verimatrix
www.insidesecure.com