linux-kernel - Re: [PATCH v2 3/5] misc: fastrpc: Add CRC support using invokeV2 request

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Message-ID: <5gxdsaq2xlj3jijg3hpcnxbq4dpor2cq7q4r4dnkvwxny42tth@3nuxnn2rvb6v>
Date: Wed, 29 Jan 2025 12:41:51 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Ekansh Gupta <quic_ekangupt@...cinc.com>
Cc: srinivas.kandagatla@...aro.org, linux-arm-msm@...r.kernel.org, 
	gregkh@...uxfoundation.org, quic_bkumar@...cinc.com, linux-kernel@...r.kernel.org, 
	quic_chennak@...cinc.com, dri-devel@...ts.freedesktop.org, arnd@...db.de
Subject: Re: [PATCH v2 3/5] misc: fastrpc: Add CRC support using invokeV2
 request

On Mon, Jan 27, 2025 at 10:12:37AM +0530, Ekansh Gupta wrote:
> InvokeV2 request is intended to support multiple enhanced invoke
> requests like CRC check, performance counter enablement and polling
> mode for RPC invocations. CRC check is getting enabled as part of
> this patch. CRC check for input and output argument helps in ensuring
> data consistency over a remote call. If user intends to enable CRC
> check, first local user CRC is calculated at user end and a CRC buffer
> is passed to DSP to capture remote CRC values. DSP is expected to
> write to the remote CRC buffer which is then compared at user level
> with the local CRC values.
> 
> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
> ---
>  drivers/misc/fastrpc.c      | 78 ++++++++++++++++++++++++++++++-------
>  include/uapi/misc/fastrpc.h |  7 ++++
>  2 files changed, 70 insertions(+), 15 deletions(-)
> 
> +
> +static int fastrpc_invokev2(struct fastrpc_user *fl, char __user *argp)
> +{
> +	struct fastrpc_ctx_args *cargs;
> +	struct fastrpc_invoke_v2 inv2;
> +	int i, err;
> +
> +	if (copy_from_user(&inv2, argp, sizeof(inv2)))
> +		return -EFAULT;
> +
> +	/* Check if all reserved fields are zero */
> +	for (i = 0; i < 16; i++) {

Noticed this while reviewing next patch. No. Nak. Never. Who makes sure
that this magic 16 is the same as the actual size of an array? Please
always use ARRAY_SIZE in such cases.

> +		if (inv2.reserved[i] != 0)
> +			return -EINVAL;
>  	}
>  
> -	cargs->args = args;
> -	err = fastrpc_internal_invoke(fl, false, inv.handle, inv.sc, cargs);
> -	kfree(args);
> +	cargs = kzalloc(sizeof(*cargs), GFP_KERNEL);
> +	if (!cargs)
> +		return -ENOMEM;
> +
> +	cargs->crc = (void __user *)(uintptr_t)inv2.crc;
> +
> +	err = fastrpc_remote_invoke(fl, &inv2.inv, cargs);
>  	kfree(cargs);
>  
>  	return err;

-- 
With best wishes
Dmitry