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

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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 <richard.henderson@linaro.org>
[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 <broonie@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
[will: Advertise HWCAP via /proc/cpuinfo]
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Richard Henderson
2020-01-21 12:58:52 +00:00
committed by Will Deacon
parent 46cf053efe
commit 1a50ec0b3b
10 changed files with 108 additions and 1 deletions
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arch/arm64/include/uapi/asm/hwcap.h
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@@ -65,5 +65,6 @@
#define HWCAP2_SVESM4 (1 << 6)
#define HWCAP2_FLAGM2 (1 << 7)
#define HWCAP2_FRINT (1 << 8)
#define HWCAP2_RNG (1 << 9)
#endif /* _UAPI__ASM_HWCAP_H */