Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request_locality function.

From: Jarkko Sakkinen
Date: Wed May 24 2017 - 18:21:39 EST


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@xxxxxxxxxxxxxxxxxx>
> ---
> 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