topic Re: SGX - EPCM and data structures in Intel® Software Guard Extensions (Intel® SGX)

SGX - EPCM and data structures

BH21 — Wed, 19 Apr 2023 04:24:49 GMT

Hi there,

I was wondering where the EPCM and data structures (e.g. PCMD) are actually stored?

This Linux Kernel doc suggests that the EPCM is a "hardware data structure", does that mean it is stored in a separate component?

Are data structures stored in the EPC itself or a separate region in PRM?

Many thanks.

Re: SGX - EPCM and data structures

KFPW_Intel — Wed, 19 Apr 2023 06:58:29 GMT

Hi BH21,

Thank you for your interest in Intel® SGX.

Enclave Page Cache Map (EPCM) is a secure structure used by the processor to track the contents of the Enclave Page Cache (EPC). The contents of enclaves and the associated data structures are stored in the EPC, which is a subset of the Processor Reserved Memory (PRM). Here is the diagram for more information.

Meanwhile, Paging Crypto MetaData (PCMD) is used to keep track of crypto meta-data associated with a paged-out page. Combined with PAGEINFO, it provides enough information for the processor to verify, decrypt, and reload a paged-out EPC page. The PCMD is available in the system memory. Refer to the diagram for more information.

Here are the references could be useful for your use cases.

Hope that the information that I provided is useful for you. Let me know if you have any questions. Thank you.

Regards,

Ken

Re:SGX - EPCM and data structures

KFPW_Intel — Wed, 26 Apr 2023 01:12:25 GMT

Hi BH21,

I hope the information I provided was helpful to you. Do you need further help with this issue?

Please inform us if you have any question regards to this issue.

Thank you.

Regards,

Ken

Re: SGX - EPCM and data structures

BH21 — Thu, 27 Apr 2023 10:02:24 GMT

Hi Ken,

Thank you for you reply, this makes a lot of sense!

Regards,

Brandon

Re:SGX - EPCM and data structures

KFPW_Intel — Thu, 27 Apr 2023 15:09:06 GMT

Hi BH21,

Great to know the information is useful for you. Please inform us if you have any question regards to this issue.

Thank you.

Regards,

Ken

Re:SGX - EPCM and data structures

KFPW_Intel — Tue, 02 May 2023 01:59:20 GMT

Hi BH21,

We have not heard from you in several days so we will no longer monitor this thread. We hope you were able to resolve your issue. Please start a new thread if you need further help.

Regards,

Ken