[PATCH v4 2/7] tpm: tpm_tis: Add check_data handle to tpm_tis_phy_ops in order to check data integrity

[<amirmizi6@gmail.com>]

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/received 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 received 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.

Co-developed-by: Christophe Richard <hristophe-h.ricard@st.com>
Signed-off-by: Christophe Richard <hristophe-h.ricard@st.com>
Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
---
 drivers/char/tpm/tpm_tis_core.c | 102 +++++++++++++++++++++++++---------------
 drivers/char/tpm/tpm_tis_core.h |   3 ++
 2 files changed, 67 insertions(+), 38 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 27c6ca0..6c4f232 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 +317,59 @@ 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 +474,19 @@ 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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