在 2025/7/11 5:58, James Bottomley 写道:
On Mon, 2025-07-07 at 11:14 +0800, yangge1116@126.com wrote:
The pcr_idx value in the Intel TDX log header is 1, causing the function __calc_tpm2_event_size() to fail to recognize the log header, ultimately leading to the "Failed to parse event in TPM Final Events Log" error.
According to UEFI Specification 2.10, Section 38.4.1: For TDX, TPM PCR 0 maps to MRTD, so the log header uses TPM PCR 1 instead. To successfully parse the TDX event log header, the check for a pcr_idx value of 0 must be skipped.
I think someone has misread the spec. EV_NO_ACTION events produce no PCR extension. So the PCR value zero is conventional (and required by the TCG) since nothing gets logged. Therefore even if you're technically using PCR0 for something else EV_NO_ACTION events should still have the conventional PCR = 0 value to conform to the TCG spec. I assume it's too late to correct this in the implementation?
According to Table 14 in Section 10.4.1 of the TCG PC Client Specification, for EV_NO_ACTION events, the PCR (Platform Configuration Register) value can be 0 or other values, such as 6.
Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClient_PFP_r1p05_...
__calc_tpm2_event_size(struct tcg_pcr_event2_head *ev count = event->count; event_type = event->event_type;
- /* Verify that it's the log header */
- if (event_header->pcr_idx != 0 ||
- /*
* Verify that it's the log header. According to the TCG PCClient
* Specification, when identifying a log header, the checkfor a
* pcr_idx value of 0 is not required. For CC platforms,skipping
* this check during log header is necessary; otherwise, theCC
* platform's log header may fail to be recognized.*/- if ((!is_cc_event && event_header->pcr_idx != 0) ||
event_header->event_type != NO_ACTION || memcmp(event_header->digest, zero_digest, sizeof(zero_digest))) { size = 0;
The above is just a heuristic to recognize an EV_NO_ACTION event as zero size. All the TCG specs require that EV_NO_ACTION have pcr 0 in the event, but if the heuristic is wrong because of Intel/CC spec violations which can't be fixed, then we should update the heuristic ... so I don't think you need to thread the is_cc_event.
It seems that the TCG specifications do not stipulate that the EV_NO_ACTION event must have PCR 0. In addition, adding is_cc_event can maximize the reuse of TPM code for CC platforms without disrupting TPM functionality; otherwise, new functions would need to be added for CC platforms.
Please review the latest patch. Patch link: https://lore.kernel.org/lkml/1751961289-29673-1-git-send-email-yangge1116@12...
Regards,
James