As per the TCG Specification[1][2], RC_COMMAND_CODE indicates that the TPM
command is not implemented or not supported. When RC_COMMAND_CODE is
returned in response to the partial selftest, this is not the case. TPM 2.0
supports TPM2_GetTestResult[3], which can be used to check the selftest
status before sending the full selftest command.
This patch implements the tpm2_get_selftest_result function to check the
selftest status when partial selftest returns RC_COMMAND_CODE.
This change results in finishing of the selftest much earlier compared to
the existing case where full selftest is immediately sent to retry. The
Pi's dmesg shows: the TPM selftest completed at 1.243864 secs compared
with the previous timestamp of 1.939667 secs.
[1] As per the TCG Specification, Trusted Platform Module Library,
Part 2 - Structures, Section 6.6.3 and Section 4.18:
"RC_COMMAND_CODE 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."
[2] As per the TCG Specification, Trusted Platform Module Library,
Part 2 - Commands, Section 5.2:
"The TPM shall successfully unmarshal a TPM_CC and verify that the command
is implemented (TPM_RC_COMMAND_CODE)."
[3] As per the TCG Specification, Trusted Platform Module Library,
Part 2 - Commands, Section 10.4:
"This command(TPM2_GetTestResult) returns manufacturer-specific information
regarding the results of a self-test and an indication of the test status."
Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
Tested-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> (on Pi with TPM 2.0)
---
Changelog v2:
* changed the subject and updated patch description
* removed the logs
drivers/char/tpm/tpm.h | 2 ++
drivers/char/tpm/tpm2-cmd.c | 48 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index af3bb87d3ea1..1de4240b52c4 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -114,6 +114,7 @@ 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,
TPM2_RC_RETRY = 0x0922,
@@ -144,6 +145,7 @@ 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 96c77c8e7f40..4abba0ebe25b 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -825,6 +825,50 @@ 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
@@ -853,6 +897,10 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
"attempting the self test");
tpm_buf_destroy(&buf);
+ /* Check the selftest status */
+ if (rc == TPM2_RC_COMMAND_CODE)
+ rc = tpm2_get_selftest_result(chip);
+
if (rc == TPM2_RC_TESTING)
rc = TPM2_RC_SUCCESS;
if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
--
2.13.6
