[PATCH v2 2/5] char: tpm: Add check_data handle to tpm_tis_phy_ops in order to check data integrity

[amirmizi6]

From: Amir Mizinski <amirmizi6@xxxxxxxxx>

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@xxxxxxxxx>
---
 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