arm64: Implement archrandom.h for ARMv8.5-RNG

Expose the ID_AA64ISAR0.RNDR field to userspace, as the RNG system
registers are always available at EL0.

Implement arch_get_random_seed_long using RNDR.  Given that the
TRNG is likely to be a shared resource between cores, and VMs,
do not explicitly force re-seeding with RNDRRS.  In order to avoid
code complexity and potential issues with hetrogenous systems only
provide values after cpufeature has finalized the system capabilities.

Signed-off-by: Richard Henderson <[email protected]>
[Modified to only function after cpufeature has finalized the system
capabilities and move all the code into the header -- broonie]
Signed-off-by: Mark Brown <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
[will: Advertise HWCAP via /proc/cpuinfo]
Signed-off-by: Will Deacon <[email protected]>

0 files changed, 0 insertions, 0 deletions