Hi,
On Wed, May 12, 2021 at 06:19:58PM +0200, Heinrich Schuchardt wrote:
On 12.05.21 18:05, Simon Glass wrote:
Hi Heinrich,
On Wed, 12 May 2021 at 10:01, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 17.02.21 04:20, Joel Stanley wrote:
Similar to support for SHA1 and SHA256, allow the use of hardware hashing engine by enabling the algorithm and setting CONFIG_SHA_HW_ACCEL / CONFIG_SHA_PROG_HW_ACCEL.
Signed-off-by: Joel Stanley joel@jms.id.au
This merged patch leads to errors compiling the EFI TCG2 protocol on boards with CONFIG_SHA_HW_ACCEL.
There is not as single implementation of hw_sha384 and hw_sha512. You could only use CONFIG_SHA_HW_ACCEL for selecting these functions if these were implemented for *all* boards with CONFIG_SHA_HW_ACCEL=y. But this will never happen.
*This patch needs to be reverted.*
Why do we have CONFIG_SHA_HW_ACCEL at all and don't use weak functions instead?
This is all a mess. We should not use weak functions IMO, but instead have a driver interface, like we do with filesystems.
Part of the challenge is the need to keep code size small for platforms that only need one algorithm.
If a function is not referenced, the linker will eliminate it. But with a driver interface every function in the interface is referenced.
Best regards
Heinrich
There's a fundamental problem with TCG2. The algorithms you need to support and log are dictated by the TPM2 hardware and it's configuration. That's a thing we can't detect at build time.
So since we don't know that, we are requiring support for all the known algorithms U-Boot supports and are mandated from the spec (SHA1/256/384/512). One way to solve this is move the 'select' to 'depends', and only allow for the protocol, if all the algorithms we need are present in the .config. But this is just a way to sidestep the problem for now. I agree with Heinrich that using a single Kconfig isn't realistic.