[Hafnium] Re: Boot arguments for S-EL1 with SPMC at S-EL2

Hi Olivier,

Comments below.

On Tue, Mar 21, 2023 at 3:36 PM Olivier Deprez Olivier.Deprez@arm.com wrote:

Hi Jens,

See comments inline [OD].

Regards, Olivier.

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From: Jens Wiklander via Hafnium hafnium@lists.trustedfirmware.org Sent: 21 March 2023 09:30 To: Olivier Deprez Olivier.Deprez@arm.com Cc: hafnium@lists.trustedfirmware.org hafnium@lists.trustedfirmware.org; OP-TEE TrustedFirmware op-tee@lists.trustedfirmware.org Subject: [Hafnium] Boot arguments for S-EL1 with SPMC at S-EL2

Hi Olivier,

I'm trying to implement a relocatable OP-TEE binary so it can be loaded at different physical addresses without the need to recompile it. This means that in the case with Hafnium when changing "load-address" or "entrypoint-offset" in the OP-TEE SP manifest there's no need to recompile OP-TEE. For this to work OP-TEE must be able to figure out which memory range it's supposed to reside in.

[OD] Fair enough, I believe that would conflate into some generic PIE support? I can see how this helps with the multi OP-TEE instances use case, perhaps?

Yes, it should help with that too.

Currently, OP-TEE knows the entry point address from PC and "memory size" from X0. However, the "memory size" is from the "load-address" so "entrypoint-offset" must be subtracted from PC in order to know the allocated memory range.

Do you have ideas on how OP-TEE at runtime can determine the allocated memory range?

[OD] The standard way would be to use the FF-A boot protocol e.g. if you add this to OP-TEE's SP manifest:

•   /* Boot protocol */
  

•   gp-register-num = <0x0>;
  

•   /* Boot Info */
  

•   boot-info {
  

•           compatible = "arm,ffa-manifest-boot-info";
  

•           ffa_manifest;
  

•   };
  

Great! That does the trick.

Thanks, Jens

See https://trustedfirmware-a.readthedocs.io/en/latest/components/secure-partiti... At SP entry, x0 contains the address of a 'Boot Information Blob' (FF-A v1.1 REL0 section 5.4.2) starting with a Boot Information Header (Table 5.9). The SP manifest DT address can be extracted from a Boot Information Descriptor (Table 5.8). Eventually the SP is able to parse its own SP manifest, into which it finds FF-A standard fields (load-address...) in addition to any impdef field added. Note the partition size is not standarded (it should probably be), so for starters you can add your own memsize field. There is some sample usage in TF-a-tests: https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/spm/cactus/cactus_m... and also in context of EDKII/StMM: https://github.com/odeprez/edk2/commit/7066c913cb227056d68ea99de5e92f2067fe7...

Thanks, Jens -- Hafnium mailing list -- hafnium@lists.trustedfirmware.org To unsubscribe send an email to hafnium-leave@lists.trustedfirmware.org