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Subject[PATCH v2 2/5] char: tpm: Add check_data handle to tpm_tis_phy_ops in order to check data integrity
Date
From: Amir Mizinski <amirmizi6@gmail.com>

In order to compute the crc over the data sent in lower layer (I2C for instance),
tpm_tis_check_data() calls an operation (if available) to check data integrity.
If data integrity cannot be verified, a retry attempt to save the sent/recieved data is implemented.

The current steps are done when sending a command:
1. Host writes to TPM_STS.commandReady.
2. Host writes command.
3. Host checks that TPM received data is valid.
4. If data is currupted go to step 1.

When receiving data:
1. Host checks that TPM_STS.dataAvail is set.
2. Host saves recieved data.
3. Host checks that received data is correct.
4. If data is currupted Host writes to TPM_STS.responseRetry and go to step 1.

This commit is based on previous work by Christophe Richard.

Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
---
drivers/char/tpm/tpm_tis_core.c | 101 +++++++++++++++++++++++++---------------
drivers/char/tpm/tpm_tis_core.h | 3 ++
2 files changed, 66 insertions(+), 38 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index c3181ea..43784fd 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -242,6 +242,15 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
return status;
}

+static bool tpm_tis_check_data(struct tpm_chip *chip, const u8 *buf, size_t len)
+{
+ struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
+
+ if (priv->phy_ops->check_data)
+ return priv->phy_ops->check_data(priv, buf, len);
+ return true;
+}
+
static void tpm_tis_ready(struct tpm_chip *chip)
{
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
@@ -308,47 +317,58 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
int size = 0;
- int status;
+ int status, i;
u32 expected;
+ bool check_data = false;

- if (count < TPM_HEADER_SIZE) {
- size = -EIO;
- goto out;
- }
+ for (i = 0; i < TPM_RETRY; i++) {
+ if (count < TPM_HEADER_SIZE) {
+ size = -EIO;
+ goto out;
+ }

- size = recv_data(chip, buf, TPM_HEADER_SIZE);
- /* read first 10 bytes, including tag, paramsize, and result */
- if (size < TPM_HEADER_SIZE) {
- dev_err(&chip->dev, "Unable to read header\n");
- goto out;
- }
+ size = recv_data(chip, buf, TPM_HEADER_SIZE);
+ /* read first 10 bytes, including tag, paramsize, and result */
+ if (size < TPM_HEADER_SIZE) {
+ dev_err(&chip->dev, "Unable to read header\n");
+ goto out;
+ }

- expected = be32_to_cpu(*(__be32 *) (buf + 2));
- if (expected > count || expected < TPM_HEADER_SIZE) {
- size = -EIO;
- goto out;
- }
+ expected = be32_to_cpu(*(__be32 *) (buf + 2));
+ if (expected > count || expected < TPM_HEADER_SIZE) {
+ size = -EIO;
+ goto out;
+ }

- size += recv_data(chip, &buf[TPM_HEADER_SIZE],
- expected - TPM_HEADER_SIZE);
- if (size < expected) {
- dev_err(&chip->dev, "Unable to read remainder of result\n");
- size = -ETIME;
- goto out;
- }
+ size += recv_data(chip, &buf[TPM_HEADER_SIZE],
+ expected - TPM_HEADER_SIZE);
+ if (size < expected) {
+ dev_err(&chip->dev, "Unable to read remainder of result\n");
+ size = -ETIME;
+ goto out;
+ }

- if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
- &priv->int_queue, false) < 0) {
- size = -ETIME;
- goto out;
+ if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
+ &priv->int_queue, false) < 0) {
+ size = -ETIME;
+ goto out;
+ }
+
+ status = tpm_tis_status(chip);
+ if (status & TPM_STS_DATA_AVAIL) { /* retry? */
+ dev_err(&chip->dev, "Error left over data\n");
+ size = -EIO;
+ goto out;
+ }
+
+ check_data = tpm_tis_check_data(chip, buf, size);
+ if (!check_data)
+ tpm_tis_write8(priv, TPM_STS(priv->locality),
+ TPM_STS_RESPONSE_RETRY);
+ else break;
}
- status = tpm_tis_status(chip);
- if (status & TPM_STS_DATA_AVAIL) { /* retry? */
- dev_err(&chip->dev, "Error left over data\n");
+ if (!check_data)
size = -EIO;
- goto out;
- }
-
out:
tpm_tis_ready(chip);
return size;
@@ -453,14 +473,19 @@ static void disable_interrupts(struct tpm_chip *chip)
static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
{
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
- int rc;
+ int rc, i;
u32 ordinal;
unsigned long dur;
+ bool data_valid = false;

- rc = tpm_tis_send_data(chip, buf, len);
- if (rc < 0)
- return rc;
-
+ for (i = 0; i < TPM_RETRY && !data_valid; i++) {
+ rc = tpm_tis_send_data(chip, buf, len);
+ if (rc < 0)
+ return rc;
+ data_valid = tpm_tis_check_data(chip, buf, len);
+ }
+ if (!data_valid)
+ return -EIO;
/* go and do it */
rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);
if (rc < 0)
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index d06c65b..486c2e9 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -34,6 +34,7 @@ enum tis_status {
TPM_STS_GO = 0x20,
TPM_STS_DATA_AVAIL = 0x10,
TPM_STS_DATA_EXPECT = 0x08,
+ TPM_STS_RESPONSE_RETRY = 0x02,
};

enum tis_int_flags {
@@ -106,6 +107,8 @@ struct tpm_tis_phy_ops {
int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
+ bool (*check_data)(struct tpm_tis_data *data, const u8 *buf,
+ size_t len);
};

static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,
--
2.7.4
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