On Thu, Jun 20, 2019 at 11:21:20AM +0200, Remco wrote: > On 19-06-19 07:13, Patrick Wildt wrote: > > Hi, > > > > this diff adds the necessary helpers to arm64 so that libcrypto knows > > which of the hardware crypto features are available on the machine. > > Those helpers are used by the existing and matching armv7 code. > > > > ok? > > > > Patrick > > > > Does it make sense to query the ID_AA64PFR0_EL1 and ID_AA64ISAR0_EL1 system > registers for that using the mrs instruction ?
It looks like those indeed encode enough information to figure it out, but apparently the registers are not readable from userland, only from EL1 and above. The armv7 code works the same like this diff for arm64, where the instruction is executed and if it traps we know it's not supported. This way it fits right in. Patrick
