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

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Fri, Jun 10, 2016 at 10:34:15AM -0700, Ed Swierk wrote:
> On Fri, Jun 10, 2016 at 5:19 AM, Jarkko Sakkinen
> <jarkko.sakkinen@linux.intel.com> 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@skyportsystems.com>
> >> ---
> >>  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?

Sometimes these kinds of things are just "evolutional" :)

There are also couple of other things that don't look right:

* tpm_transmit_cmd() already prints the TPM error
* If you use dev_err(), you must fail. If we ought to continue, it
  should be at most dev_warn().

In my opinion it is just plain wrong to continue to the durations part
in the case of TPM error. I would like to hear a second opinion, though.

> --Ed

/Jarkko