Hi David,

Hi there!

Hi David,

I don't know what options you tried to build with, but I managed to build with the ROMLIB feature for the FVP platform. I will post everything I did here, hoping it will be of some use to you.
I used the following command to build:

MBEDTLS_DIR=<path_to_mbedtls> make ARM_ROTPK_LOCATION=devel_rsa CROSS_COMPILE=<path_to_cross_compiler(aarch64)> GENERATE_COT=1 PLAT=fvp ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem TRUSTED_BOARD_BOOT=1 USE_ROMLIB=1  DEBUG=1 fiptool all

The cross-compiler I used is GCC 8.3 for AArch64 ELF bare-metal target. You can get it from here:
https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-a/downloads

So, just to be clear: Imagine a scenario with two devices - one I made (I know the keys and code on BL1) and another one that some malicious user cloned (he signed with his own keys). My device will have a Root of Trust in BL1 based on my hardware and the keys I own. The second device also has a BL1 but that image was signed by someone I don't trust. In the end, both devices will boot up successfully because they are based on each individual Chain of Trust but there's no way a third party (i.e. remote attestation server) can know the difference between the malicious device and my device solely relying on Verified Boot, right?

Verified boot in itself already proves the boot integrity of all firmware images from BL1 up to BL33.

BL1 is the root of trust and cannot be tampered with, as it is hardware-protected. All other BL image are signed and their signature is verified before they get executed: BL1 verifies the signature of BL2, and BL2 does the same for all subsequent BL3x images. If one of the signatures is invalid then TF-A refuses to execute the corresponding image. This is treated as a fatal error that the firmware cannot recover from and the platform will typically panic in this case.

Sorry, I completely missed your point at first!

In T464#5627, @soby-mathew wrote:

Hi vivina,

Hi @soby-mathew !

Hi vivina,
Are you thinking something similar to measured boot ?
The TF-A implements what is called verified boot. Found a good description for difference between verified and measured boot here:
https://forums.juniper.net/t5/Security/What-s-the-Difference-between-Secure-Boot-and-Measured-Boot/ba-p/281251

Thanks Sandrine!

Hi Viviane,

Please email me at soby.mathew@arm.com

ARM Support have asked me not to post any Cryptocell code publicly.

Hi Neil
The Cryptocell variant supported by TF-A is CC-712 which only has support for RSA 2048.

Reopening so it can be answered

It’s better to create a task from scratch than edit the example task. Added back in TF-A project so it is shown on the project workbook with your question.

Hi David, Sorry for the delay in replying.

Support platform for rockchip px30
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/1253

Thanks guys! The dmbish() is not a huge deal. Just get a little nervous when i see barriers and don't completely understand why it is there. :)

Ah, You are right. Having taken a look at it again, yes, the SP-> SPM communication is register based and this spm_response_add() is invoked by SPM to push to a buffer within EL3 (its not a shared buffer between different ELs). I suspect the shared buffer primitives were written with shared buffer scenario in mind and the current prototype implementation does not optimize it for the case when the buffer is within EL3.

Thanks Paul, Soby.
spm_response_*() currently cannot invoked by any secure partition since the responses[] array is in EL3 space. Is this not the case ? or is it the expectation that the responses array will be mapped to secure EL0 some time in the future? I don't see how a secure partition can invoke spm_response_* other than through an SMC, in which case we are already in EL3 context and dont require the dmbish(), as Paul pointed. I understand your argument for sprt_queue_*, since they are invoked by EL3 and the secure partition.

Who is the lockless reader for spm_response_add() and spm_response_get()?

Apologies for the delay. I've had a look into the spm_buffers.c file and I understand your query is around the dmbish() that's performed shortly before releasing the lock in both spm_response_add() and spm_response_get().