linux-kernel - Re: [PATCH v12 14/19] tpm, tpm

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Message-ID: <Z8qaw4XwH3QljLEM@kernel.org>
Date: Fri, 7 Mar 2025 09:05:39 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Ross Philipson <ross.philipson@...cle.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
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Subject: Re: [PATCH v12 14/19] tpm, tpm_tis: Close all localities

On Thu, Dec 19, 2024 at 11:42:11AM -0800, Ross Philipson wrote:
> From: "Daniel P. Smith" <dpsmith@...rtussolutions.com>
> 
> There are environments, for example, those that comply with the TCG D-RTM
> specification that requires the TPM to be left in locality 2. Prepare
> kernel for such environments by closing all the localities.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@...rtussolutions.com>
> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 11 ++++++++++-
>  include/linux/tpm.h             |  6 ++++++
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index fdef214b9f6b..c58f360fb4a4 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -1104,7 +1104,7 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  	u32 intmask;
>  	u32 clkrun_val;
>  	u8 rid;
> -	int rc, probe;
> +	int rc, probe, i;
>  	struct tpm_chip *chip;
>  
>  	chip = tpmm_chip_alloc(dev, &tpm_tis);
> @@ -1166,6 +1166,15 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		goto out_err;
>  	}
>  
> +	/*
> +	 * There are environments, for example, those that comply with the TCG D-RTM
> +	 * specification that requires the TPM to be left in Locality 2.
> +	 */

I'd just shorten this into

/*
 * In order to comply with the TCG D-RTM specification, relinquish all
 * the localities.
 */

And that's it. It's a punctual reminder and that is what source code
comments should be for.


> +	for (i = 0; i <= TPM_MAX_LOCALITY; i++) {
> +		if (check_locality(chip, i))
> +			tpm_tis_relinquish_locality(chip, i);
> +	}
> +
>  	/* Take control of the TPM's interrupt hardware and shut it off */
>  	rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask);
>  	if (rc < 0)
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 20a40ade8030..c5a4a2d7dd15 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -147,6 +147,12 @@ struct tpm_chip_seqops {
>   */
>  #define TPM2_MAX_CONTEXT_SIZE 4096
>  
> +/*
> + * The maximum locality (0 - 4) for a TPM, as defined in section 3.2 of the
> + * Client Platform Profile Specification.
> + */
> +#define TPM_MAX_LOCALITY		4
> +
>  struct tpm_chip {
>  	struct device dev;
>  	struct device devs;
> -- 
> 2.39.3
> 

Otherwise, this is great.

BR, Jarkko