On Wed, Nov 04, 2020 at 10:59:03PM +0100, Heinrich Schuchardt wrote:
> On 11/4/20 6:26 PM, Ilias Apalodimas wrote:
> > Hi Heinrich,
> >
> > On Wed, Nov 04, 2020 at 05:50:16PM +0100, Heinrich Schuchardt wrote:
> >> On 04.11.20 16:56, Ilias Apalodimas wrote:
> >>>>>
> >>>>> u32 tpm2_get_capability(struct udevice *dev, u32 capability, u32
> >>>>> property,
> >>>>> - void *buf, size_t prop_count)
> >>>>> + void *buf, size_t prop_count, bool get_count)
> >>>>
> >>>> The implementation would be more stable if we would derive the offset
> >>>> from field property instead of adding get_count.
> >>>>
> >>>
> >>> We are not defining the tpmv2 internal structures anywhere in U-Boot.
> >>> That's why the code is doing static sizeof(uX) instead of using offsetof.
> >>> In the EFI part of the patchset, I've done exaclty that.
> >>> Working with offsets on well defined struct is better, but out of scope
> >>> for this
> >>> patchset imho.
> >>> We can look into refactoring the generic tpmv2 code once I add the rest
> >>> of the EFI
> >>> protocol parts?
> >>
> >> Can't we add the structures that we need to tpm-v2.h and use their size
> >> here?
> >
> > Yes we can, but the scope of the patch is adding EFI_TCG2_PROTOCOL, not
> > re-factor the tpmv2
> > code along the way.
> > Since the only change on the existing code to support the functionality
> > needed for the
> > EFI_TCG2_PROTOCOL protocol is just 4 bytes on an existing buffer, can we
> > stick to that and
> > think of refactoring the tpm stuff afterwards?
>
> You expect a TPML_PCR_SELECTION when capabilities is TPM_CAP_PCRS.
>
> typedef struct {
> UINT32 count;
> TPMS_PCR_SELECTION pcrSelections[TPM2_NUM_PCR_BANKS];
> } TPML_PCR_SELECTION;
>
> Why do you have to skip over the UINT32 here?
You *don't* have to skip it since you need to implement GetCapabilty() and
specifically
the HashAlgorithmBitmap and ActivePcrBanks.
That's what this patch is actually doing, preserve the u32 (corresponding to
count).
>
> You just have to define this one structure in preparation of patch 2 and
> then you can correctly parse the response in your implementation of the
> EFI protocol.
The struct is defined in this patchset, it's part of patch 2 and used to
implement
the EFI protocol.
>
> I suggest not to change tpm2_get_capability() at all.
You can't.
The current code has this comment:
" * In the response buffer, the properties are located after the:
* tag (u16), response size (u32), response code (u32),
* YES/NO flag (u8), TPM_CAP (u32) and TPMU_CAPABILITIES (u32)."
So unless I am missing something it's referring to:
typedef struct {
UINT32 count;
TPMS_TAGGED_PROPERTY tpmProperty[MAX_TPM_PROPERTIES];
} TPML_TAGGED_TPM_PROPERTY;
So the last u32 that's removed from the buffer is the 'count', which it removes
to access
the tpmProperty directly.
Regards
/Ilias
>
> Best regards
>
> Heinrich
>
> >
> > Regards
> > /Ilias
> >>
> >> Best regards
> >>
> >> Heinrich
> >>
> >>>
> >>>>> {
> >>>>> u8 command_v2[COMMAND_BUFFER_SIZE] = {
> >>>>
> >>>> Shouldn't COMMAND_BUFFER_SIZE be changed to something with TPM in the
> >>>> name, e.g TPM_COMMAND_BUFFER_SIZE?
> >>>>
> >>>>> tpm_u16(TPM2_ST_NO_SESSIONS), /* TAG */
> >>>>> @@ -181,13 +181,17 @@ u32 tpm2_get_capability(struct udevice *dev, u32
> >>>>> capability, u32 property,
> >>>>> if (ret)
> >>>>> return ret;
> >>>>>
> >>>>> + /* When reading PCR properties we need the count */
> >>>>> + properties_off = sizeof(u16) + sizeof(u32) + sizeof(u32) +
> >>>>> + sizeof(u8) + sizeof(u32);
> >>>>> /*
> >>>>> * In the response buffer, the properties are located after the:
> >>>>> * tag (u16), response size (u32), response code (u32),
> >>>>> * YES/NO flag (u8), TPM_CAP (u32) and TPMU_CAPABILITIES (u32).
> >>>>> */
> >>>>
> >>>> This comment should be above 'properties_off ='. 'get_count' related
> >>>> field should be mentioned.
> >>>
> >>> Sure, I'll fix this
> >>>
> >>> Regards
> >>> /Ilias
> >>>>
> >>>> Best regards
> >>>>
> >>>> Heinrich
> >>>>
> >>>>> - properties_off = sizeof(u16) + sizeof(u32) + sizeof(u32) +
> >>>>> - sizeof(u8) + sizeof(u32) + sizeof(u32);
> >>>>> + if (!get_count)
> >>>>> + properties_off += sizeof(u32);
> >>>>> +
> >>>>> memcpy(buf, &response[properties_off], response_len -
> >>>>> properties_off);
> >>>>>
> >>>>> return 0;
> >>>>>
> >>>>
> >>
>
