Re: [PATCH 7/8] tpm: Implement state command for Cr50

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Mon, Feb 28, 2022 at 05:11:24PM -0700, Simon Glass wrote:
> Add a vendor-specific TPM2 command for this and implement it for Cr50.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
> 
>  drivers/tpm/cr50_i2c.c | 117 +++++++++++++++++++++++++++++++++++++++++
>  include/tpm-v2.h       |  54 +++++++++++++++++++
>  lib/tpm-v2.c           |  24 +++++++++
>  3 files changed, 195 insertions(+)
> 
> diff --git a/drivers/tpm/cr50_i2c.c b/drivers/tpm/cr50_i2c.c
> index f8c3087894..dabf617be0 100644
> --- a/drivers/tpm/cr50_i2c.c
> +++ b/drivers/tpm/cr50_i2c.c
> @@ -13,11 +13,13 @@
>  #include <irq.h>
>  #include <log.h>
>  #include <spl.h>
> +#include <tpm-common.h>
>  #include <tpm-v2.h>
>  #include <acpi/acpigen.h>
>  #include <acpi/acpi_device.h>
>  #include <asm/gpio.h>
>  #include <asm/io.h>
> +#include <asm/unaligned.h>
>  #include <linux/delay.h>
>  #include <dm/acpi.h>
>  
> @@ -54,6 +56,41 @@ struct cr50_priv {
>  	bool use_irq;
>  };
>  
> +/*
> + * The below structure represents the body of the response to the 'report tpm
> + * state' vendor command.
> + *
> + * It is transferred over the wire, so it needs to be serialized/deserialized,
> + * and it is likely to change, so its contents must be versioned.
> + */
> +#define TPM_STATE_VERSION	1
> +struct tpm_vendor_state {
> +	u32 version;
> +	/*
> +	 * The following three fields are set by the TPM in case of an assert.
> +	 * There is no other processing than setting the source code line
> +	 * number, error code and the first 4 characters of the function name.
> +	 *
> +	 * We don't expect this happening, but it is included in the report
> +	 * just in case.
> +	 */
> +	u32 fail_line;	/* s_failLIne */
> +	u32 fail_code;	/* s_failCode */
> +	char func_name[4];	/* s_failFunction, limited to 4 chars */
> +
> +	/*
> +	 * The following two fields are the current time filtered value of the
> +	 * 'failed tries' TPM counter, and the maximum allowed value of the
> +	 * counter.
> +	 *
> +	 * failed_tries == max_tries is the definition of the TPM lockout
> +	 * condition.
> +	 */
> +	u32 failed_tries;	/* gp.failedTries */
> +	u32 max_tries;	/* gp.maxTries */
> +	/* The below fields are present in version 2 and above */
> +};
> +
>  /* Wait for interrupt to indicate TPM is ready */
>  static int cr50_i2c_wait_tpm_ready(struct udevice *dev)
>  {
> @@ -573,6 +610,85 @@ static int cr50_i2c_get_desc(struct udevice *dev, char *buf, int size)
>  	return len;
>  }
>  
> +static int stringify_state(char *buf, int len, char *str, size_t max_size)
> +{
> +	struct tpm_vendor_state state;
> +	size_t text_size = 0;
> +
> +	state.version = get_unaligned_be32(buf +
> +		offsetof(struct tpm_vendor_state, version));
> +	state.fail_line = get_unaligned_be32(buf +
> +		offsetof(struct tpm_vendor_state, fail_line));
> +	state.fail_code = get_unaligned_be32(buf +
> +		offsetof(struct tpm_vendor_state, fail_code));
> +	memcpy(state.func_name,
> +	       buf + offsetof(struct tpm_vendor_state, func_name),
> +	       sizeof(state.func_name));
> +	state.failed_tries = get_unaligned_be32(buf +
> +		offsetof(struct tpm_vendor_state, failed_tries));
> +	state.max_tries = get_unaligned_be32(buf +
> +		offsetof(struct tpm_vendor_state, max_tries));
> +
> +	text_size += snprintf(str + text_size, max_size - text_size,
> +			      "v=%d", state.version);
> +	if (text_size >= max_size)
> +		return -ENOSPC;
> +
> +	if (state.version > TPM_STATE_VERSION)
> +		text_size += snprintf(str + text_size,
> +				      max_size - text_size,
> +				      " not fully supported\n");
> +	if (text_size >= max_size)
> +		return -ENOSPC;
> +
> +	if (state.version == 0)
> +		return -EINVAL;	/* This should never happen */
> +
> +	text_size += snprintf(str + text_size,
> +			      max_size - text_size,
> +			      " failed_tries=%d max_tries=%d\n",
> +			      state.failed_tries, state.max_tries);
> +	if (text_size >= max_size)
> +		return -ENOSPC;
> +
> +	if (state.fail_line) {
> +		/* make sure function name is zero terminated. */
> +		char func_name[sizeof(state.func_name) + 1];
> +
> +		memcpy(func_name, state.func_name, sizeof(state.func_name));
> +		func_name[sizeof(state.func_name)] = '\0';
> +
> +		text_size += snprintf(str + text_size,
> +				      max_size - text_size,
> +				      "tpm failed: f %s line %d code %d",
> +				      func_name,
> +				      state.fail_line,
> +				      state.fail_code);
> +		if (text_size >= max_size)
> +			return -ENOSPC;
> +	}
> +
> +	return 0;
> +}

Is this error state described in the TCG TIS specs ?  If so we should plug
this into the generic TPM API and the driver should only define
cr50_i2c_report_state() etc

> +
> +static int cr50_i2c_report_state(struct udevice *dev, char *str, int str_max)
> +{
> +	char buf[50];
> +	int buf_size = sizeof(buf);
> +	int ret;
> +
> +	ret = tpm2_cr50_report_state(dev, buf, &buf_size);
> +	if (ret)
> +		return ret;
> +
> +	/* TPM responded as expected */
> +	ret = stringify_state(buf, buf_size, str, str_max);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +

[...]

Thanks
/Ilias