On Wed, Sep 18, 2024 at 03:28:44PM +0800, Gary Lin via Grub-devel wrote:
> On Tue, Sep 17, 2024 at 11:14:33PM -0400, Stefan Berger wrote:
> > On 9/6/24 5:11 AM, Gary Lin wrote:
> > > A Trusted Platform Module (TPM) Software Stack (TSS) provides logic to
> > > compose and submit TPM commands and parse reponses.
> > >
> >
> > > +static TPM_RC_t
> > > +tpm2_submit_command_real (const TPMI_ST_COMMAND_TAG_t tag,
> > > + const TPM_CC_t commandCode,
> > > + TPM_RC_t *responseCode,
> > > + const struct grub_tpm2_buffer *in,
> > > + struct grub_tpm2_buffer *out)
> > > +{
> > > + grub_err_t err;
> > > + struct grub_tpm2_buffer buf;
> > > + TPMI_ST_COMMAND_TAG_t tag_out;
> > > + grub_uint32_t command_size;
> > > + grub_size_t max_output_size;
> > > +
> > > + /* Marshal */
> > > + grub_tpm2_buffer_init (&buf);
> > > + grub_tpm2_buffer_pack_u16 (&buf, tag);
> > > + grub_tpm2_buffer_pack_u32 (&buf, 0);
> > > + grub_tpm2_buffer_pack_u32 (&buf, commandCode);
> > > + grub_tpm2_buffer_pack (&buf, in->data, in->size);
> > > +
> > > + if (buf.error != 0)
> > > + return TPM_RC_FAILURE;
> > > +
> > > + command_size = grub_swap_bytes32 (buf.size);
> > > + grub_memcpy (&buf.data[sizeof (grub_uint16_t)], &command_size,
> > > + sizeof (command_size));
> >
> > This is odd. So UEFI requires that the command size is in little endian
> > while the TPM commands are typically all in big endian format? If so, could
> > you push this into the grub_tcg2_submit_command? Other firmware doesn't need
> > this odd endianess switch and could just leave the size as-is and just pass
> > the TPM command to the device without switching endianess again.
>
> EFI_TCG2_PROTOCOL.SubmitCommand() expects the little-endian
> InputParameterBlockSize, and InputParameterBlock in big-endian for the
> TPM command stream.
>
> Actually, the code is also needed when running grub-emu on a
> little-endian system. Maybe we can add an additional check for the
> endianness here and only run the code for the little-endian systems.
Why do not define grub_cpu_to_tpm32()/grub_tpm_to_cpu32() et consores
macros and make them noop on some archs?
Daniel
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