[PATCH v8 4/8] tpm: tpm_tis: Fix expected bit handling and send all bytes in one shot without last byte in exception

amirmizi6
2020-05-12T14:15:55Z

Incorrect implementation of send message was detected. We polled only
TPM_STS.stsValid bit and then we single-checked the TPM_STS.expect bit
value.
TPM_STS.expected bit should be checked at the same time as
TPM_STS.stsValid bit, and this should be repeated until timeout_A.

To detect a TPM_STS.expected bit reset, the "wait_for_tpm_stat" function is
modified to "wait_for_tpm_stat_result". This function regularly reads the
status register and check the bits defined by "mask" to reach the value
defined in "mask_result".

This correct implementation is required for using the new CRC calculation
on I2C TPM command bytes or I2C TPM answer bytes. TPM_STS.expected bit is
reset after all bytes are acquired and the CRC result is inserted in the
dedicated register. It introduces a normal latency for TPM_STS.expected
bit reset.

Respectively, to send a message, as defined in
TCG_DesignPrinciples_TPM2p0Driver_vp24_pubrev.pdf, all bytes should be
sent in one shot instead of sending the last byte separately.

Suggested-by: Benoit Houyere <benoit.houyere@st.com>
Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
---
drivers/char/tpm/tpm_tis_core.c | 74 +++++++++++++++++------------------------
1 file changed, 30 insertions(+), 44 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 682f950..f71ecd8 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -44,9 +44,10 @@ 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_result(struct tpm_chip *chip, u8 mask,
+ u8 mask_result, unsigned long timeout,
+ wait_queue_head_t *queue,
+ bool check_cancel)
{
unsigned long stop;
long rc;
@@ -55,7 +56,7 @@ 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) == mask_result)
return 0;

stop = jiffies + timeout;
@@ -83,7 +84,7 @@ 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) == mask_result)
return 0;
} while (time_before(jiffies, stop));
}
@@ -292,10 +293,13 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
int size = 0, burstcnt, rc;

while (size < count) {
- rc = wait_for_tpm_stat(chip,
- TPM_STS_DATA_AVAIL | TPM_STS_VALID,
- chip->timeout_c,
- &priv->read_queue, true);
+ rc = wait_for_tpm_stat_result(chip,
+ 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);
@@ -350,8 +354,9 @@ 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_result(chip, TPM_STS_VALID,
+ TPM_STS_VALID, chip->timeout_c,
+ &priv->int_queue, false) < 0) {
size = -ETIME;
goto out;
}
@@ -387,61 +392,40 @@ 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_result(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) {
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);
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_result(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;

@@ -498,9 +482,11 @@ 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_result(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;
}
--
2.7.4