linux-kernel - Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request

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Date:   Wed, 24 May 2017 15:21:30 -0700
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, jgunthorpe@...idianresearch.com
Subject: Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request_locality
 function.

On Wed, May 24, 2017 at 05:39:40PM -0400, Stefan Berger wrote:
> Implement the request_locality function. To set the locality on the
> backend we define vendor-specific TPM 1.2 and TPM 2 ordinals and send
> a command to the backend to set the locality for the next commands.
> 
> To avoid recursing into requesting the locality, we set the
> TPM_TRANSMIT_RAW flag when calling tpm_transmit_cmd. To avoid recursing
> into TPM 2 space related commands, we set the space parameter to NULL.
> 
> Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
> ---
>  drivers/char/tpm/tpm-interface.c  |  1 +
>  drivers/char/tpm/tpm_vtpm_proxy.c | 36 ++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/vtpm_proxy.h   |  4 ++++
>  3 files changed, 41 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 2eacda2..876d45f 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -537,6 +537,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
>  
>  #define TPM_DIGEST_SIZE 20
>  #define TPM_RET_CODE_IDX 6
> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> index 751059d..66024bf 100644
> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> @@ -371,6 +371,41 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
>  	return ret;
>  }
>  
> +static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
> +{
> +	struct tpm_buf buf;
> +	int rc;
> +	const struct tpm_output_header *header;
> +
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
> +				  TPM2_CC_SET_LOCALITY);

I would always go with this branch.

> +	else
> +		rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
> +				  TPM_ORD_SET_LOCALITY);
> +	if (rc)
> +		return rc;
> +	tpm_buf_append_u8(&buf, locality);
> +
> +	rc = tpm_transmit_cmd(chip, NULL, buf.data, tpm_buf_length(&buf), 0,
> +			      TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_RAW,
> +			      "attempting to set locality");
> +	if (rc < 0) {
> +		locality = rc;
> +		goto out;
> +	}
> +
> +	header = (const struct tpm_output_header *)buf.data;
> +	rc = be32_to_cpu(header->return_code);
> +	if (rc)
> +		locality = -1;
> +
> +out:
> +	tpm_buf_destroy(&buf);
> +
> +	return locality;
> +}
> +
>  static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>  	.flags = TPM_OPS_AUTO_STARTUP,
>  	.recv = vtpm_proxy_tpm_op_recv,
> @@ -380,6 +415,7 @@ static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>  	.req_complete_mask = VTPM_PROXY_REQ_COMPLETE_FLAG,
>  	.req_complete_val = VTPM_PROXY_REQ_COMPLETE_FLAG,
>  	.req_canceled = vtpm_proxy_tpm_req_canceled,
> +	.request_locality = vtpm_proxy_request_locality,
>  };
>  
>  /*
> diff --git a/include/uapi/linux/vtpm_proxy.h b/include/uapi/linux/vtpm_proxy.h
> index a69e991..58ac73c 100644
> --- a/include/uapi/linux/vtpm_proxy.h
> +++ b/include/uapi/linux/vtpm_proxy.h
> @@ -46,4 +46,8 @@ struct vtpm_proxy_new_dev {
>  
>  #define VTPM_PROXY_IOC_NEW_DEV	_IOWR(0xa1, 0x00, struct vtpm_proxy_new_dev)
>  
> +/* vendor specific commands to set locality */
> +#define TPM2_CC_SET_LOCALITY	0x20001000
> +#define TPM_ORD_SET_LOCALITY	0x20001000
> +
>  #endif /* _UAPI_LINUX_VTPM_PROXY_H */
> -- 
> 2.4.3

What practical benefit you get from these two constants? I understand
the value range but not so much the redundant code.

/Jarkko