linux-kernel - Re: [PATCH v2 6/6] soc/fsl/qe: qe.c: fold qe_get_num_of_snums into qe_snums

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Date:   Thu, 2 May 2019 06:54:07 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Qiang Zhao <qiang.zhao@....com>, Li Yang <leoyang.li@....com>
Cc:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Scott Wood <oss@...error.net>,
        Mark Rutland <mark.rutland@....com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: Re: [PATCH v2 6/6] soc/fsl/qe: qe.c: fold qe_get_num_of_snums into
 qe_snums_init



Le 01/05/2019 à 11:29, Rasmus Villemoes a écrit :
> The comment "No QE ever has fewer than 28 SNUMs" is false; e.g. the
> MPC8309 has 14. The code path returning -EINVAL is also a recipe for
> instant disaster, since the caller (qe_snums_init) uncritically
> assigns the return value to the unsigned qe_num_of_snum, and would
> thus proceed to attempt to copy 4GB from snum_init_46[] to the snum[]
> array.
> 
> So fold the handling of the legacy fsl,qe-num-snums into
> qe_snums_init, and make sure we do not end up using the snum_init_46
> array in cases other than the two where we know it makes sense.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>

Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

> ---
>   drivers/soc/fsl/qe/qe.c | 46 ++++++++++++++---------------------------
>   1 file changed, 16 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c
> index 325d689cbf5c..276d7d78ebfc 100644
> --- a/drivers/soc/fsl/qe/qe.c
> +++ b/drivers/soc/fsl/qe/qe.c
> @@ -308,24 +308,33 @@ static void qe_snums_init(void)
>   	int i;
>   
>   	bitmap_zero(snum_state, QE_NUM_OF_SNUM);
> +	qe_num_of_snum = 28; /* The default number of snum for threads is 28 */
>   	qe = qe_get_device_node();
>   	if (qe) {
>   		i = of_property_read_variable_u8_array(qe, "fsl,qe-snums",
>   						       snums, 1, QE_NUM_OF_SNUM);
> -		of_node_put(qe);
>   		if (i > 0) {
> +			of_node_put(qe);
>   			qe_num_of_snum = i;
>   			return;
>   		}
> +		/*
> +		 * Fall back to legacy binding of using the value of
> +		 * fsl,qe-num-snums to choose one of the static arrays
> +		 * above.
> +		 */
> +		of_property_read_u32(qe, "fsl,qe-num-snums", &qe_num_of_snum);
> +		of_node_put(qe);
>   	}
>   
> -	qe_num_of_snum = qe_get_num_of_snums();
> -
> -	if (qe_num_of_snum == 76)
> +	if (qe_num_of_snum == 76) {
>   		snum_init = snum_init_76;
> -	else
> +	} else if (qe_num_of_snum == 28 || qe_num_of_snum == 46) {
>   		snum_init = snum_init_46;
> -
> +	} else {
> +		pr_err("QE: unsupported value of fsl,qe-num-snums: %u\n", qe_num_of_snum);
> +		return;
> +	}
>   	memcpy(snums, snum_init, qe_num_of_snum);
>   }
>   
> @@ -641,30 +650,7 @@ EXPORT_SYMBOL(qe_get_num_of_risc);
>   
>   unsigned int qe_get_num_of_snums(void)
>   {
> -	struct device_node *qe;
> -	int size;
> -	unsigned int num_of_snums;
> -	const u32 *prop;
> -
> -	num_of_snums = 28; /* The default number of snum for threads is 28 */
> -	qe = qe_get_device_node();
> -	if (!qe)
> -		return num_of_snums;
> -
> -	prop = of_get_property(qe, "fsl,qe-num-snums", &size);
> -	if (prop && size == sizeof(*prop)) {
> -		num_of_snums = *prop;
> -		if ((num_of_snums < 28) || (num_of_snums > QE_NUM_OF_SNUM)) {
> -			/* No QE ever has fewer than 28 SNUMs */
> -			pr_err("QE: number of snum is invalid\n");
> -			of_node_put(qe);
> -			return -EINVAL;
> -		}
> -	}
> -
> -	of_node_put(qe);
> -
> -	return num_of_snums;
> +	return qe_num_of_snum;
>   }
>   EXPORT_SYMBOL(qe_get_num_of_snums);
>   
>