Hi,
I would like to restart a discussion that we already had a few years
ago on a thread called "SMC to intentionally trigger a panic in TF-A"
(https://lists.trustedfirmware.org/archives/search?mlist=tf-a%40lists.truste…)
but that petered out without any real resolution (and resulted in me
ultimately not implementing the feature I was hoping to add).
Basically, we are repeatedly stumbling over the problem that we have a
use case for some platform-independent SMC API that we want to
implement in TF-A, but don't have an appropriate SMC FID range to put
it. My request from a few years ago was about implementing a call to
intentionally trigger a panic in TF-A for test-automation purposes.
Today we came up with a use case where a Trusted OS wants to query
BL31 about the location of a shared log buffer:
https://review.trustedfirmware.org/20478 .
Currently, the available SMC ranges are Arm, CPU, SiP, OEM, Standard,
Hypervisor, TA and TOS. The SiP, OEM and TOS ranges are all specific
to a single silicon vendor, OEM or trusted OS implementation, so they
are not good targets to implement APIs that would make sense to be
shared among multiple of these. In theory, the Standard range would
probably be the right target to implement calls that are independently
useful for multiple platforms / OSes... but as far as I understand,
adding a new call to that range requires petitioning Arm to update the
SMC calling convention itself, which is a ridiculously high bar to
implement a small utility API. In practice, the only choice we have
for implementing these kinds of calls is to let every OEM, SiP or TOS
assign its own (different) FID for it and then write separate SMC
handlers for each in TF-A that all end up calling the same underlying
function... which creates a lot of unnecessary code duplication and
identifier soup (especially in the case of SMCs for the non-secure OS
which would then be implemented by a platform-independent Linux driver
that needs a big mapping table to decide which FID to use on which
platform for the same API).
I think it would be very useful if there was another range of easily
allocatable FIDs that developers could just add to with a simple TF-A
CL without having to go through a huge specification update process.
There are still 41 OENs unused in the Arm SMCCC, and I don't think any
new ones were added in the 10 years that the specification existed...
so we are really not going to run out of them any time soon. If we
could get even one of those OENs for this purpose, we would have 64K
FIDs to use up for our small, simple platform-independent API needs,
which should last us a long while. We could maybe call it the "Secure
Monitor range" and say the FIDs are specific to a certain
implementation of Secure Monitor (e.g. TF-A). Then there could just be
a header file in the TF-A sources that serves as the authoritative FID
assignment table for TF-A, and anyone with a sufficiently useful idea
(subject to TF-A maintainer review) for a platform-independent API
like this could add it there by just uploading a patch.
I recently argued for a similar "simple tag allocation" concept on
https://github.com/FirmwareHandoff/firmware_handoff and it found
support there, so I hope I'll be able to convince you that it would be
useful for SMC FIDs as well?
Hello,
We use fiptool extensively to generate the FIP blobs for NVIDIA platforms. But, we encountered the following issues during deployment.
1. fiptool has a dependency on the host machine for OpenSSL and gcc.
2. fiptool resides under the TF-A repo and is used by Hafnium and SPs. This creates a cross-repository dependency.
As a workaround, we ship a prebuilt fiptool. But, due to OS dependency, this approach is not scalable across OS versions. E.g. One OS distribution might be using a lower OpenSSL version compared another, creating an incompatibility.
I was thinking if converting fiptool to a python script might help resolve these issues. Sptool was converted into a Python script, so was wondering if anyone has tried converting fiptool to a Python script too.
-Varun
Hi All,
I wanted to let you know that next Thursday, July 27th, the TF-A Tech Forum
will be hosting a presentation on OpenCI and MISRA presented by Paul
Sokolovski of Linaro and Roberto Bagnara from Bugseng. MISRA is being
enabled on both TF-A and TF-M in OpenCI, so sending this out to both lists
since users in both domains may be interested in the session.
Meeting time and dial up info can be found in the TF community calendar
located here: https://www.trustedfirmware.org/meetings/
Best Regards,
Don Harbin
TrustedFirmware Community Manager
don.harbin(a)linaro.org
Hi,
Typically, BL31 runs in SRAM which tends to be limited. As we add
support for newer architectural features e.g. CCA, general features
and standards, the size of BL31 image will grow and become harder to
fit in most SRAMs.
This email is to share ideas on how to address this problem.
A simple approach will be to identify parts of NOBITS ELF sections of
BL31 which can be moved out to DRAM. Since NOBITS sections aren't part
of the file image, loading and authentication code doesn't have to
change. The challenge will be to come up with some criteria to help
decide what kind of buffers can be kept in DRAM vs SRAM.
Other ideas are also welcome. Please share your thoughts.
Thanks,
Okash
Hi,
We have two topics for the upcoming TF-A Tech Forum on Jul, 13th:
Certificate signer-id retrieval - Manish Badarkhe
* Quick recap
* Authentication Mechanism
* Role of public key
* What is signer ID and its usage?
* Design of signer ID retrieval for attestation
Updates to EL3 vector entry path to cater for async EA(SError) exceptions - Manish Pandey
*
Description of error synchronization during EL3 entry.
* Go through the implementation of handling of these errors in EL3 for Firmware First Handling (FFH) scenarios.
* Reflecting it back in Kernel First Handling (KFH) scenario.
* Description of the test scenarios introduced.
Regards,
Olivier.
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Hi Manish,
I'll answer on behalf of Benjamin and Sieu because I think they are offline now.
I reached out to these guys privately this morning and they said they will post patches to fix these defects.
Cheers,
Sandrine