arm64: random: implement arch_get_random_int/_long based on RNDR

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When support for RNDR/RNDRRS was introduced, we elected to only
implement arch_get_random_seed_int/_long(), and back them by RNDR
instead of RNDRRS. This was needed to prevent potential performance
and/or starvation issues resulting from the fact that the /dev/random
driver used to invoke these routines on various hot paths.

These issues have all been addressed now [0] [1], and so we can wire up
this API more straight-forwardly:

- map arch_get_random_int/_long() onto RNDR, which returns the output of
  a DRBG that is reseeded at an implemented defined rate;
- map arch_get_random_seed_int/_long() onto the TRNG firmware service,
  which returns true, conditioned entropy, or onto RNDRRS if the TRNG
  service is unavailable, which returns the output of a DRBG that is
  reseeded every time it is used.

[0] 390596c995 random: avoid arch_get_random_seed_long() when collecting IRQ randomness
[1] 2ee25b6968 random: avoid superfluous call to RDRAND in CRNG extraction

Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220113131239.1610455-1-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

...

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Ard Biesheuvel 2022-01-13 14:12:39 +01:00 • committed by Will Deacon

parent dfd42facf1

commit 35bde68bba

1 changed files with 39 additions and 6 deletions

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arch/arm64/include/asm/archrandom.h

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