Re: [PATCH v15 1/6] tpm_tis: Fix expected bit handling and send all bytes in one shot without last byte in exception

[Jarkko Sakkinen <jarkko@kernel.org>]

On Tue, 2021-09-14 at 18:10 +0300, amirmizi6@gmail.com wrote:
> From: Amir Mizinski <amirmizi6@gmail.com>
> 
> Detected an incorrect implementation of the send command.
> Currently, the driver polls the TPM_STS.stsValid field until TRUE; then it
> reads TPM_STS register again to verify only that TPM_STS.expect field is
> FALSE (i.e., it ignores TPM_STS.stsValid).
> Since TPM_STS.stsValid represents the TPM_STS.expect validity, both fields
> fields should be checked in the same TPM_STS register read value.

This is missing description of what kind of error/consquence this caused.
Perhaps you got something to the klog, or how did you find out about the
issue? Since you have reproduced, please connect it to the reality.

> Modify the signature of 'wait_for_tpm_stat()', add an additional
> "mask_result" parameter to its call and rename it to
> 'tpm_tis_wait_for_stat()' for better alignment with other naming.
> 'tpm_tis_wait_for_stat()' is now polling the TPM_STS with a mask and waits
> for the value in mask_result. Add the ability to check if certain TPM_STS
> bits have been cleared.

The commit description is probably out of sync (not only rename, there is no
parameter called mask_result).

It's also lacking description, how this new parameter is taken advantage of.

E.g.

"Use the new parameter to check that status TPM_STS_VALID is set,
 in addition that TPM_STS_EXPECT is zeroed. This prevents a racy
 checkk


> In addition, the send command was changed to comply with
> TCG_DesignPrinciples_TPM2p0Driver_vp24_pubrev.pdf as follows:
> - send all command bytes in one loop
> - remove special handling of the last byte
> 
> Suggested-by: Benoit Houyere <benoit.houyere@st.com>
> Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 68 +++++++++++++++--------------------------
>  1 file changed, 25 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 69579ef..7d5854b 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -44,9 +44,9 @@ static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
>  	return false;
>  }
>  
> -static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
> -		unsigned long timeout, wait_queue_head_t *queue,
> -		bool check_cancel)
> +static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask, u8 stat,
> +				 unsigned long timeout,
> +				 wait_queue_head_t *queue, bool check_cancel)

This naming is not too great, considering that there is already local variable
called status.


>  {
>  	unsigned long stop;
>  	long rc;
> @@ -55,7 +55,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>  
>  	/* check current status */
>  	status = chip->ops->status(chip);
> -	if ((status & mask) == mask)
> +	if ((status & mask) == stat)
>  		return 0;
>  
>  	stop = jiffies + timeout;
> @@ -83,7 +83,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>  			usleep_range(TPM_TIMEOUT_USECS_MIN,
>  				     TPM_TIMEOUT_USECS_MAX);
>  			status = chip->ops->status(chip);
> -			if ((status & mask) == mask)
> +			if ((status & mask) == stat)
>  				return 0;
>  		} while (time_before(jiffies, stop));
>  	}
> @@ -260,9 +260,10 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
>  
>  	while (size < count) {
>  		rc = wait_for_tpm_stat(chip,
> -				 TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> -				 chip->timeout_c,
> -				 &priv->read_queue, true);
> +					   TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +					   TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +					   chip->timeout_c, &priv->read_queue,
> +					   true);
>  		if (rc < 0)
>  			return rc;
>  		burstcnt = get_burstcount(chip);
> @@ -315,8 +316,9 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>  		goto out;
>  	}
>  
> -	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> -				&priv->int_queue, false) < 0) {
> +	if (wait_for_tpm_stat(chip, TPM_STS_VALID, TPM_STS_VALID,
> +				  chip->timeout_c, &priv->int_queue,
> +				  false) < 0) {
>  		size = -ETIME;
>  		goto out;
>  	}
> @@ -342,61 +344,40 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>  	int rc, status, burstcnt;
>  	size_t count = 0;
> -	bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND;
>  
>  	status = tpm_tis_status(chip);
>  	if ((status & TPM_STS_COMMAND_READY) == 0) {
>  		tpm_tis_ready(chip);
> -		if (wait_for_tpm_stat
> -		    (chip, TPM_STS_COMMAND_READY, chip->timeout_b,
> -		     &priv->int_queue, false) < 0) {
> +		if (wait_for_tpm_stat(chip, TPM_STS_COMMAND_READY,
> +					  TPM_STS_COMMAND_READY,
> +					  chip->timeout_b, &priv->int_queue,
> +					  false) < 0) {
>  			rc = -ETIME;
>  			goto out_err;
>  		}
>  	}
>  
> -	while (count < len - 1) {
> +	while (count < len) {

This.

>  		burstcnt = get_burstcount(chip);
>  		if (burstcnt < 0) {
>  			dev_err(&chip->dev, "Unable to read burstcount\n");
>  			rc = burstcnt;
>  			goto out_err;
>  		}
> -		burstcnt = min_t(int, burstcnt, len - count - 1);
> +		burstcnt = min_t(int, burstcnt, len - count);

What are these two changes (loop condition and the right above change)?

>  		rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
>  					 burstcnt, buf + count);
>  		if (rc < 0)
>  			goto out_err;
>  
>  		count += burstcnt;
> -
> -		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> -					&priv->int_queue, false) < 0) {
> -			rc = -ETIME;
> -			goto out_err;
> -		}
> -		status = tpm_tis_status(chip);
> -		if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
> -			rc = -EIO;
> -			goto out_err;
> -		}
>  	}
> -
> -	/* write last byte */
> -	rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[count]);
> -	if (rc < 0)
> -		goto out_err;
> -
> -	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> -				&priv->int_queue, false) < 0) {
> +	if (wait_for_tpm_stat(chip, TPM_STS_VALID | TPM_STS_DATA_EXPECT,
> +				  TPM_STS_VALID, chip->timeout_a,
> +				  &priv->int_queue, false) < 0) {
>  		rc = -ETIME;
>  		goto out_err;
>  	}
> -	status = tpm_tis_status(chip);
> -	if (!itpm && (status & TPM_STS_DATA_EXPECT) != 0) {
> -		rc = -EIO;
> -		goto out_err;
> -	}
>  
>  	return 0;
>  
> @@ -451,9 +432,10 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>  		ordinal = be32_to_cpu(*((__be32 *) (buf + 6)));
>  
>  		dur = tpm_calc_ordinal_duration(chip, ordinal);
> -		if (wait_for_tpm_stat
> -		    (chip, TPM_STS_DATA_AVAIL | TPM_STS_VALID, dur,
> -		     &priv->read_queue, false) < 0) {
> +		if (wait_for_tpm_stat(chip,
> +					  TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +					  TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +					  dur, &priv->read_queue, false) < 0) {
>  			rc = -ETIME;
>  			goto out_err;
>  		}

/Jarkko