RE: [PATCH] crypto: inside-secure - fix type of buffer in eip197_write_firmware

[Pascal Van Leeuwen <pvanleeuwen@verimatrix.com>]

> -----Original Message-----
> From: Pascal Van Leeuwen
> Sent: Thursday, October 17, 2019 7:14 PM
> To: 'Ben Dooks (Codethink)' <ben.dooks@codethink.co.uk>; linux-
> kernel@lists.codethink.co.uk
> Cc: Antoine Tenart <antoine.tenart@bootlin.com>; Herbert Xu
> <herbert@gondor.apana.org.au>; David S. Miller <davem@davemloft.net>; linux-
> crypto@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: RE: [PATCH] crypto: inside-secure - fix type of buffer in eip197_write_firmware
> 
> > -----Original Message-----
> > From: linux-crypto-owner@vger.kernel.org <linux-crypto-owner@vger.kernel.org> On Behalf
> Of Ben
> > Dooks (Codethink)
> > Sent: Wednesday, October 16, 2019 1:50 PM
> > To: linux-kernel@lists.codethink.co.uk
> > Cc: Ben Dooks (Codethink) <ben.dooks@codethink.co.uk>; Antoine Tenart
> > <antoine.tenart@bootlin.com>; Herbert Xu <herbert@gondor.apana.org.au>; David S. Miller
> > <davem@davemloft.net>; linux-crypto@vger.kernel.org; linux-kernel@vger.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?
> 

After some more thought on the train home:

I think the correct construct would be cpu_to_le32(be32_to_cpu(data[i]))
This would correctly reflect that the data is read from big-endian
memory and subsequently written to little-endian "memory" (aka the EIP).
It also fits in nicely with your other changes. Could you work that into
a patch v2? Then I would ack it (after testing).

> 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@codethink.co.uk>
> > ---
> > Cc: Antoine Tenart <antoine.tenart@bootlin.com>
> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: linux-crypto@vger.kernel.org
> > Cc: linux-kernel@vger.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

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