Re: [PATCH 7/8] tpm: Implement state command for Cr50

[Simon Glass <sjg@chromium.org>]

Hi Ilias,

On Tue, 7 Jun 2022 at 02:54, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> On Mon, Feb 28, 2022 at 05:11:24PM -0700, Simon Glass wrote:
> > Add a vendor-specific TPM2 command for this and implement it for Cr50.
> >
> > Signed-off-by: Simon Glass <sjg@chromium.org>
> > ---
> >
> >  drivers/tpm/cr50_i2c.c | 117 +++++++++++++++++++++++++++++++++++++++++
> >  include/tpm-v2.h       |  54 +++++++++++++++++++
> >  lib/tpm-v2.c           |  24 +++++++++
> >  3 files changed, 195 insertions(+)
> >
> > diff --git a/drivers/tpm/cr50_i2c.c b/drivers/tpm/cr50_i2c.c
> > index f8c3087894..dabf617be0 100644
> > --- a/drivers/tpm/cr50_i2c.c
> > +++ b/drivers/tpm/cr50_i2c.c
> > @@ -13,11 +13,13 @@
> >  #include <irq.h>
> >  #include <log.h>
> >  #include <spl.h>
> > +#include <tpm-common.h>
> >  #include <tpm-v2.h>
> >  #include <acpi/acpigen.h>
> >  #include <acpi/acpi_device.h>
> >  #include <asm/gpio.h>
> >  #include <asm/io.h>
> > +#include <asm/unaligned.h>
> >  #include <linux/delay.h>
> >  #include <dm/acpi.h>
> >
> > @@ -54,6 +56,41 @@ struct cr50_priv {
> >       bool use_irq;
> >  };
> >
> > +/*
> > + * The below structure represents the body of the response to the 'report tpm
> > + * state' vendor command.
> > + *
> > + * It is transferred over the wire, so it needs to be serialized/deserialized,
> > + * and it is likely to change, so its contents must be versioned.
> > + */
> > +#define TPM_STATE_VERSION    1
> > +struct tpm_vendor_state {
> > +     u32 version;
> > +     /*
> > +      * The following three fields are set by the TPM in case of an assert.
> > +      * There is no other processing than setting the source code line
> > +      * number, error code and the first 4 characters of the function name.
> > +      *
> > +      * We don't expect this happening, but it is included in the report
> > +      * just in case.
> > +      */
> > +     u32 fail_line;  /* s_failLIne */
> > +     u32 fail_code;  /* s_failCode */
> > +     char func_name[4];      /* s_failFunction, limited to 4 chars */
> > +
> > +     /*
> > +      * The following two fields are the current time filtered value of the
> > +      * 'failed tries' TPM counter, and the maximum allowed value of the
> > +      * counter.
> > +      *
> > +      * failed_tries == max_tries is the definition of the TPM lockout
> > +      * condition.
> > +      */
> > +     u32 failed_tries;       /* gp.failedTries */
> > +     u32 max_tries;  /* gp.maxTries */
> > +     /* The below fields are present in version 2 and above */
> > +};
> > +
> >  /* Wait for interrupt to indicate TPM is ready */
> >  static int cr50_i2c_wait_tpm_ready(struct udevice *dev)
> >  {
> > @@ -573,6 +610,85 @@ static int cr50_i2c_get_desc(struct udevice *dev, char *buf, int size)
> >       return len;
> >  }
> >
> > +static int stringify_state(char *buf, int len, char *str, size_t max_size)
> > +{
> > +     struct tpm_vendor_state state;
> > +     size_t text_size = 0;
> > +
> > +     state.version = get_unaligned_be32(buf +
> > +             offsetof(struct tpm_vendor_state, version));
> > +     state.fail_line = get_unaligned_be32(buf +
> > +             offsetof(struct tpm_vendor_state, fail_line));
> > +     state.fail_code = get_unaligned_be32(buf +
> > +             offsetof(struct tpm_vendor_state, fail_code));
> > +     memcpy(state.func_name,
> > +            buf + offsetof(struct tpm_vendor_state, func_name),
> > +            sizeof(state.func_name));
> > +     state.failed_tries = get_unaligned_be32(buf +
> > +             offsetof(struct tpm_vendor_state, failed_tries));
> > +     state.max_tries = get_unaligned_be32(buf +
> > +             offsetof(struct tpm_vendor_state, max_tries));
> > +
> > +     text_size += snprintf(str + text_size, max_size - text_size,
> > +                           "v=%d", state.version);
> > +     if (text_size >= max_size)
> > +             return -ENOSPC;
> > +
> > +     if (state.version > TPM_STATE_VERSION)
> > +             text_size += snprintf(str + text_size,
> > +                                   max_size - text_size,
> > +                                   " not fully supported\n");
> > +     if (text_size >= max_size)
> > +             return -ENOSPC;
> > +
> > +     if (state.version == 0)
> > +             return -EINVAL; /* This should never happen */
> > +
> > +     text_size += snprintf(str + text_size,
> > +                           max_size - text_size,
> > +                           " failed_tries=%d max_tries=%d\n",
> > +                           state.failed_tries, state.max_tries);
> > +     if (text_size >= max_size)
> > +             return -ENOSPC;
> > +
> > +     if (state.fail_line) {
> > +             /* make sure function name is zero terminated. */
> > +             char func_name[sizeof(state.func_name) + 1];
> > +
> > +             memcpy(func_name, state.func_name, sizeof(state.func_name));
> > +             func_name[sizeof(state.func_name)] = '\0';
> > +
> > +             text_size += snprintf(str + text_size,
> > +                                   max_size - text_size,
> > +                                   "tpm failed: f %s line %d code %d",
> > +                                   func_name,
> > +                                   state.fail_line,
> > +                                   state.fail_code);
> > +             if (text_size >= max_size)
> > +                     return -ENOSPC;
> > +     }
> > +
> > +     return 0;
> > +}
>
> Is this error state described in the TCG TIS specs ?  If so we should plug
> this into the generic TPM API and the driver should only define
> cr50_i2c_report_state() etc

No, this is not in the spec. It is one of the many extensions supported by Cr50.

>
> > +
> > +static int cr50_i2c_report_state(struct udevice *dev, char *str, int str_max)
> > +{
> > +     char buf[50];
> > +     int buf_size = sizeof(buf);
> > +     int ret;
> > +
> > +     ret = tpm2_cr50_report_state(dev, buf, &buf_size);
> > +     if (ret)
> > +             return ret;
> > +
> > +     /* TPM responded as expected */
> > +     ret = stringify_state(buf, buf_size, str, str_max);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return 0;
> > +}
> > +
>
> [...]
>
> Thanks
> /Ilias

Regards,
Simon