The TPM can choose one of two ways to react to the TPM2_SelfTest command.
It can either run all self tests synchronously and then return RC_SUCCESS
once all tests were successful. Or it can choose to run the tests
asynchronously and return RC_TESTING immediately while the self tests still
execute in the background.
The previous implementation apparently was not aware of those possibilities
and attributed RC_TESTING to some prototype chips instead. With this change
the return code of TPM2_SelfTest is interpreted correctly, i.e. the self
test result is polled if and only if RC_TESTING is received. Unfortunately,
the polling cannot be done in the most straightforward way, so the solution
is explained with a comment in the code.
Signed-off-by: Alexander Steffen <alexander.stef...@infineon.com>
---
drivers/char/tpm/tpm2-cmd.c | 68 ++++++++++++++++++---------------------------
1 file changed, 27 insertions(+), 41 deletions(-)
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e3d4cc3..d09032f 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -834,68 +834,54 @@ static const struct tpm_input_header tpm2_selftest_header
= {
};
/**
- * tpm2_continue_selftest() - start a self test
- *
- * @chip: TPM chip to use
- * @full: test all commands instead of testing only those that were not
- * previously tested.
- *
- * Return: Same as with tpm_transmit_cmd with exception of RC_TESTING.
- */
-static int tpm2_start_selftest(struct tpm_chip *chip, bool full)
-{
- int rc;
- struct tpm2_cmd cmd;
-
- cmd.header.in = tpm2_selftest_header;
- cmd.params.selftest_in.full_test = full;
-
- rc = tpm_transmit_cmd(chip, NULL, &cmd, TPM2_SELF_TEST_IN_SIZE, 0, 0,
- "continue selftest");
-
- /* At least some prototype chips seem to give RC_TESTING error
- * immediately. This is a workaround for that.
- */
- if (rc == TPM2_RC_TESTING) {
- dev_warn(&chip->dev, "Got RC_TESTING, ignoring\n");
- rc = 0;
- }
-
- return rc;
-}
-
-/**
* tpm2_do_selftest() - ensure that all self tests have passed
*
* @chip: TPM chip to use
*
* Return: Same as with tpm_transmit_cmd.
*
- * During the self test TPM2 commands return with the error code RC_TESTING.
- * Waiting is done by issuing PCR read until it executes successfully.
+ * The TPM can either run all self tests synchronously and then return
+ * RC_SUCCESS once all tests were successful. Or it can choose to run the tests
+ * asynchronously and return RC_TESTING immediately while the self tests still
+ * execute in the background. This function handles both cases and waits until
+ * all tests have completed.
*/
static int tpm2_do_selftest(struct tpm_chip *chip)
{
int rc;
unsigned int delay_msec = 20;
long duration;
+ struct tpm2_cmd cmd;
duration = jiffies_to_msecs(
tpm2_calc_ordinal_duration(chip, TPM2_CC_SELF_TEST));
- rc = tpm2_start_selftest(chip, false);
- if (rc)
- return rc;
-
while (duration > 0) {
- /* Attempt to read a PCR value */
- rc = tpm2_pcr_read(chip, 0, NULL);
- if (rc < 0)
- break;
+ cmd.header.in = tpm2_selftest_header;
+ cmd.params.selftest_in.full_test = 0;
+
+ rc = tpm_transmit_cmd(chip, NULL, &cmd, TPM2_SELF_TEST_IN_SIZE,
+ 0, 0, "continue selftest");
if (rc != TPM2_RC_TESTING)
break;
+ /* If RC_TESTING is received, ideally the code should now poll
+ * the selfTestDone bit in the STS register, as this avoids
+ * sending more commands, that might interrupt self tests
+ * executing in the background and thus prevent them from ever
+ * completing.
+ * Unfortunately, it cannot be guaranteed that this bit is
+ * correctly implemented for all devices, so the next best thing
+ * would be to use TPM2_GetTestResult to query the test result.
+ * But the response to that command can be very long, and the
+ * code currently lacks the capabilities for efficient
+ * unmarshalling, so it is difficult to execute this command.
+ * Therefore, we simply run the TPM2_SelfTest command in a loop,
+ * which should complete eventually, since we only request the
+ * execution of self tests that have not yet been done.
+ */
+
msleep(delay_msec);
duration -= delay_msec;
--
2.7.4
------------------------------------------------------------------------------
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