[v4,0/1] arm64: Implement archrandom.h for ARMv8.5-RNG

Message

Richard Henderson Nov. 6, 2019, 2:19 p.m. UTC

The ARMv8.5-RNG extension adds a hardware random number generator.
The plumbing for this is already present in the kernel; we just
have to take advantage of that.

Changes since v2:
  * Keep arch_get_random{,_seed}_long in sync.
  * Use __cpus_have_const_cap before falling back to this_cpu_has_cap.

Changes since v1:
  * Use __mrs_s and fix missing cc clobber (Mark),
  * Log rng failures with pr_warn (Mark),
  * Use __must_check; put RNDR in arch_get_random_long and RNDRRS
    in arch_get_random_seed_long (Ard),
  * Use ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE, and check this_cpu_has_cap
    when reading random data.
  * Move everything out of line, now that there are 5 other function
    calls involved, and to unify the rate limiting on the pr_warn.

Tested with QEMU.  What's not tested is hot plugging cpus with differing
capabilities; QEMU would need some extension to allow that sort of thing.


r~


Richard Henderson (1):
  arm64: Implement archrandom.h for ARMv8.5-RNG

 Documentation/arm64/cpu-feature-registers.rst |  2 +
 arch/arm64/include/asm/archrandom.h           | 35 ++++++++
 arch/arm64/include/asm/cpucaps.h              |  3 +-
 arch/arm64/include/asm/sysreg.h               |  4 +
 arch/arm64/kernel/cpufeature.c                | 13 +++
 arch/arm64/kernel/random.c                    | 79 +++++++++++++++++++
 arch/arm64/Kconfig                            | 12 +++
 arch/arm64/kernel/Makefile                    |  1 +
 drivers/char/Kconfig                          |  4 +-
 9 files changed, 150 insertions(+), 3 deletions(-)
 create mode 100644 arch/arm64/include/asm/archrandom.h
 create mode 100644 arch/arm64/kernel/random.c