Re: [PATCH v5 3/4] tpm: Allow TPM chip drivers to override reported command durations

[Ed Swierk]

On Fri, Jun 10, 2016 at 5:19 AM, Jarkko Sakkinen
<jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> On Wed, Jun 08, 2016 at 04:00:17PM -0700, Ed Swierk wrote:
>> Some TPM chips report bogus command durations in their capabilities,
>> just as others report incorrect timeouts. Rework tpm_get_timeouts()
>> to allow chip drivers to override either via a single callback.
>> Also clean up handling of TPMs that report milliseconds instead of
>> microseconds.
>>
>> Signed-off-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
>> ---
>>  drivers/char/tpm/tpm-interface.c | 177 +++++++++++++++++++++------------------
>>  drivers/char/tpm/tpm_tis.c       |  35 ++------
>>  include/linux/tpm.h              |   3 +-
>>  3 files changed, 106 insertions(+), 109 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index cc1e5bc..b8a08bb 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -502,123 +502,138 @@ static int tpm_startup(struct tpm_chip *chip, __be16 startup_type)
>>                               "attempting to start the TPM");
>>  }
>>
>> -int tpm_get_timeouts(struct tpm_chip *chip)
>> +static int tpm_get_cap_prop(struct tpm_chip *chip, __be32 type, int size,
>> +                         cap_t *cap, char *desc)
>>  {
>>       struct tpm_cmd_t tpm_cmd;
>> -     unsigned long new_timeout[4];
>> -     unsigned long old_timeout[4];
>> -     struct duration_t *duration_cap;
>>       ssize_t rc;
>>
>>       tpm_cmd.header.in = tpm_getcap_header;
>>       tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
>>       tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
>> -     tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
>> +     tpm_cmd.params.getcap_in.subcap = type;
>>       rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, NULL);
>>
>>       if (rc == TPM_ERR_INVALID_POSTINIT) {
>>               /* The TPM is not started, we are the first to talk to it.
>>                  Execute a startup command. */
>> -             dev_info(chip->pdev, "Issuing TPM_STARTUP");
>> +             dev_info(chip->pdev, "Issuing TPM_STARTUP\n");
>>               if (tpm_startup(chip, TPM_ST_CLEAR))
>>                       return rc;
>>
>>               tpm_cmd.header.in = tpm_getcap_header;
>>               tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
>>               tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
>> -             tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
>> +             tpm_cmd.params.getcap_in.subcap = type;
>>               rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
>>                                 NULL);
>>       }
>> +
>>       if (rc) {
>>               dev_err(chip->pdev,
>> -                     "A TPM error (%zd) occurred attempting to determine the timeouts\n",
>> -                     rc);
>> -             goto duration;
>> +                     "Error %zd reading %s\n", rc, desc);
>> +             return -EINVAL;
>>       }
>>
>>       if (be32_to_cpu(tpm_cmd.header.out.return_code) != 0 ||
>>           be32_to_cpu(tpm_cmd.header.out.length)
>> -         != sizeof(tpm_cmd.header.out) + sizeof(u32) + 4 * sizeof(u32))
>> +         != sizeof(tpm_cmd.header.out) + sizeof(u32) + size * sizeof(u32)) {
>> +             dev_err(chip->pdev,
>> +                     "Bad return code or length reading %s\n", desc);
>>               return -EINVAL;
>> -
>> -     old_timeout[0] = be32_to_cpu(tpm_cmd.params.getcap_out.cap.timeout.a);
>> -     old_timeout[1] = be32_to_cpu(tpm_cmd.params.getcap_out.cap.timeout.b);
>> -     old_timeout[2] = be32_to_cpu(tpm_cmd.params.getcap_out.cap.timeout.c);
>> -     old_timeout[3] = be32_to_cpu(tpm_cmd.params.getcap_out.cap.timeout.d);
>> -     memcpy(new_timeout, old_timeout, sizeof(new_timeout));
>> -
>> -     /*
>> -      * Provide ability for vendor overrides of timeout values in case
>> -      * of misreporting.
>> -      */
>> -     if (chip->ops->update_timeouts != NULL)
>> -             chip->vendor.timeout_adjusted =
>> -                     chip->ops->update_timeouts(chip, new_timeout);
>> -
>> -     if (!chip->vendor.timeout_adjusted) {
>> -             /* Don't overwrite default if value is 0 */
>> -             if (new_timeout[0] != 0 && new_timeout[0] < 1000) {
>> -                     int i;
>> -
>> -                     /* timeouts in msec rather usec */
>> -                     for (i = 0; i != ARRAY_SIZE(new_timeout); i++)
>> -                             new_timeout[i] *= 1000;
>> -                     chip->vendor.timeout_adjusted = true;
>> -             }
>>       }
>>
>> -     /* Report adjusted timeouts */
>> -     if (chip->vendor.timeout_adjusted) {
>> -             dev_info(chip->pdev,
>> -                      HW_ERR "Adjusting reported timeouts: A %lu->%luus B %lu->%luus C %lu->%luus D %lu->%luus\n",
>> -                      old_timeout[0], new_timeout[0],
>> -                      old_timeout[1], new_timeout[1],
>> -                      old_timeout[2], new_timeout[2],
>> -                      old_timeout[3], new_timeout[3]);
>> -     }
>> +     memcpy(cap, &tpm_cmd.params.getcap_out.cap, sizeof(cap_t));
>>
>> -     chip->vendor.timeout_a = usecs_to_jiffies(new_timeout[0]);
>> -     chip->vendor.timeout_b = usecs_to_jiffies(new_timeout[1]);
>> -     chip->vendor.timeout_c = usecs_to_jiffies(new_timeout[2]);
>> -     chip->vendor.timeout_d = usecs_to_jiffies(new_timeout[3]);
>> +     return 0;
>> +}
>>
>> -duration:
>> -     tpm_cmd.header.in = tpm_getcap_header;
>> -     tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
>> -     tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
>> -     tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_DURATION;
>> +int tpm_get_timeouts(struct tpm_chip *chip)
>> +{
>> +     cap_t cap1, cap2;
>> +     int rc1, rc2;
>> +     struct tpm_vendor_specific orig_vendor;
>> +
>> +     rc1 = tpm_get_cap_prop(chip, TPM_CAP_PROP_TIS_TIMEOUT, 4, &cap1,
>> +                            "timeouts");
>> +     if (rc1 == 0) {
>> +             be32_to_cpus(&cap1.timeout.a);
>> +             be32_to_cpus(&cap1.timeout.b);
>> +             be32_to_cpus(&cap1.timeout.c);
>> +             be32_to_cpus(&cap1.timeout.d);
>> +             chip->vendor.timeout_a = usecs_to_jiffies(cap1.timeout.a);
>> +             chip->vendor.timeout_b = usecs_to_jiffies(cap1.timeout.b);
>> +             chip->vendor.timeout_c = usecs_to_jiffies(cap1.timeout.c);
>> +             chip->vendor.timeout_d = usecs_to_jiffies(cap1.timeout.d);
>> +     }
>> +     rc2 = tpm_get_cap_prop(chip, TPM_CAP_PROP_TIS_DURATION, 3, &cap2,
>> +                            "durations");
>> +     if (rc2 == 0) {
>> +             be32_to_cpus(&cap2.duration.tpm_short);
>> +             be32_to_cpus(&cap2.duration.tpm_medium);
>> +             be32_to_cpus(&cap2.duration.tpm_long);
>> +             chip->vendor.duration[TPM_SHORT] =
>> +                     usecs_to_jiffies(cap2.duration.tpm_short);
>> +             chip->vendor.duration[TPM_MEDIUM] =
>> +                     usecs_to_jiffies(cap2.duration.tpm_medium);
>> +             chip->vendor.duration[TPM_LONG] =
>> +                     usecs_to_jiffies(cap2.duration.tpm_long);
>> +     }
>
> This is major change to the semantics. Before -EINVAL would have been
> return on error condition.
>
> PS If you want to encapsulate tpm_get_cap_prop(), that step should be
> a separate commit (prepend this one).

Good points.

I'm confused about the error semantics in the first (timeouts) part of
tpm_get_timeouts(). If tpm_transmit_cmd() returns zero and a header
check fails, it returns -EINVAL. But if tpm_transmit_cmd() returns
nonzero, it swallows the error.

In contrast, in the second (durations) part, an error is returned in
either case.

Is this difference intentional, or should tpm_get_timeouts() return
errors immediately in all cases?

--Ed