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Subject[PATCH] tpm: TPM 2.0 selftest performance improvement
Date
For selftest being run in the background, the TCG 2.0 Specification
provides the command TPM2_GetTestResult to check the status of selftest
completion.

When the partial selftest command is sent just after TPM initialization,
it is observed that it returns RC_COMMAND_CODE error, which as per TPM 2.0
Specification, indicates "the response code that is returned if the TPM is
unmarshalling a value that it expects to be a TPM_CC and the input value is
not in the table." This doesn't indicate the exact status of selftest
command on TPM. But, it can be verified by sending the TPM2_GetTestResult.

This patch implements the TPM2_GetTestResult command and uses it to check
the selftest status, before sending the full selftest command after partial
selftest returns RC_COMMAND_CODE.

With this change, dmesg shows the TPM selftest completed at 1.243864
compared with the previous 1.939667 time.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Tested-by: Mimi Zohar <zohar@linux.vnet.ibm.com> (on Pi with TPM 2.0)
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
drivers/char/tpm/tpm.h | 2 ++
drivers/char/tpm/tpm2-cmd.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 61 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 82ae7b722161..d95eeb7c002a 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -107,6 +107,7 @@ enum tpm2_return_codes {
TPM2_RC_FAILURE = 0x0101,
TPM2_RC_DISABLED = 0x0120,
TPM2_RC_COMMAND_CODE = 0x0143,
+ TPM2_RC_NEEDS_TEST = 0x0153,
TPM2_RC_TESTING = 0x090A, /* RC_WARN */
TPM2_RC_REFERENCE_H0 = 0x0910,
};
@@ -135,6 +136,7 @@ enum tpm2_command_codes {
TPM2_CC_FLUSH_CONTEXT = 0x0165,
TPM2_CC_GET_CAPABILITY = 0x017A,
TPM2_CC_GET_RANDOM = 0x017B,
+ TPM2_CC_GET_TEST_RESULT = 0x017C,
TPM2_CC_PCR_READ = 0x017E,
TPM2_CC_PCR_EXTEND = 0x0182,
TPM2_CC_LAST = 0x018F,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 89a5397b18d2..494f6dfbc65d 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -823,6 +823,50 @@ unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal)
EXPORT_SYMBOL_GPL(tpm2_calc_ordinal_duration);

/**
+ * tpm2_get_selftest_result() - get the status of self tests
+ *
+ * @chip: TPM chip to use
+ *
+ * Return: If error return rc, else return the result of the self tests.
+ * TPM_RC_NEEDS_TESTING: No self tests are done. Needs testing.
+ * TPM_RC_TESTING: Self tests are in progress.
+ * TPM_RC_SUCCESS: Self tests completed successfully.
+ * TPM_RC_FAILURE: Self tests completed failure.
+ *
+ * This function can be used to check the status of self tests on the TPM.
+ */
+static int tpm2_get_selftest_result(struct tpm_chip *chip)
+{
+ struct tpm_buf buf;
+ int rc;
+ int test_result;
+ uint16_t data_size;
+ int len;
+ const struct tpm_output_header *header;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_TEST_RESULT);
+ if (rc)
+ return rc;
+
+ len = tpm_transmit(chip, NULL, buf.data, PAGE_SIZE, 0);
+ if (len < 0)
+ return len;
+
+ header = (struct tpm_output_header *)buf.data;
+
+ rc = be32_to_cpu(header->return_code);
+ if (rc)
+ return rc;
+
+ data_size = be16_to_cpup((__be16 *)&buf.data[TPM_HEADER_SIZE]);
+
+ test_result = be32_to_cpup((__be32 *)
+ (&buf.data[TPM_HEADER_SIZE + 2 + data_size]));
+
+ return test_result;
+}
+
+/**
* tpm2_do_selftest() - ensure that all self tests have passed
*
* @chip: TPM chip to use
@@ -851,10 +895,25 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
"attempting the self test");
tpm_buf_destroy(&buf);

+ dev_dbg(&chip->dev, "tpm selftest command returned %04x\n", rc);
if (rc == TPM2_RC_TESTING)
rc = TPM2_RC_SUCCESS;
if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
return rc;
+
+ if (rc == TPM2_RC_COMMAND_CODE) {
+
+ dev_info(&chip->dev, "Check TPM Test Results\n");
+ rc = tpm2_get_selftest_result(chip);
+
+ dev_info(&chip->dev, "tpm self test result is %04x\n",
+ rc);
+ if (rc == TPM2_RC_TESTING)
+ rc = TPM2_RC_SUCCESS;
+ if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS
+ || TPM2_RC_FAILURE)
+ return rc;
+ }
}

return rc;
--
2.13.6
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