| // Copyright 2021 The Fuchsia Authors |
| // |
| // Use of this source code is governed by a MIT-style |
| // license that can be found in the LICENSE file or at |
| // https://opensource.org/licenses/MIT |
| |
| #include <lib/arch/arm64/feature.h> |
| #include <lib/arch/intrin.h> |
| #include <lib/arch/random.h> |
| |
| namespace arch { |
| |
| template <bool Reseed> |
| bool Random<Reseed>::Supported() { |
| return ArmIdAa64IsaR0El1::Read().rndr() != ArmIdAa64IsaR0El1::Rndr::kNone; |
| } |
| |
| template <bool Reseed> |
| std::optional<uint64_t> Random<Reseed>::Get() { |
| uint64_t value; |
| uint32_t flag; |
| |
| #define READ_REGISTER(regname) \ |
| __asm__ volatile( \ |
| ".arch armv8.5-a+rng\n\t" \ |
| "mrs %[value], " #regname \ |
| "\n\t" \ |
| "cset %w[flag], ne" \ |
| : [value] "=r"(value), [flag] "=r"(flag) \ |
| : \ |
| : "cc") |
| |
| if constexpr (Reseed) { |
| READ_REGISTER(RNDRRS); |
| } else { |
| READ_REGISTER(RNDR); |
| } |
| |
| #undef READ_REGISTER |
| |
| return flag ? std::make_optional(value) : std::nullopt; |
| } |
| |
| template struct Random<false>; |
| template struct Random<true>; |
| |
| } // namespace arch |
