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Kernel: Use RDSEED assembly snippet to seed RNG on Aarch64
There’s similar RDRAND register (encoded as ‘s3_3_c2_c4_0ʼ) to be added if needed. RNG CPU feature on Aarch64 guarantees existence of both RDSEED and RDRAND registers simultaneously—in contrast to x86-64, where respective instructions are independent of each other.
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@ -91,6 +91,19 @@ inline void enter_el1_from_el2()
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: "x0");
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}
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inline u64 read_rndrrs()
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{
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u64 value = 0;
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asm volatile(
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"retry:\n"
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"mrs %[value], s3_3_c2_c4_1 \n" // encoded RNDRRS register
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"b.eq retry\n"
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: [value] "=r"(value));
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return value;
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}
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}
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namespace Kernel {
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@ -44,6 +44,8 @@ void Processor::initialize()
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dmesgln("CPU[{}]: Supports {}", m_cpu, build_cpu_feature_names(m_features));
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dmesgln("CPU[{}]: Physical address bit width: {}", m_cpu, m_physical_address_bit_width);
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dmesgln("CPU[{}]: Virtual address bit width: {}", m_cpu, m_virtual_address_bit_width);
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if (!has_feature(CPUFeature::RNG))
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dmesgln("CPU[{}]: {} not detected, randomness will be poor", m_cpu, cpu_feature_to_description(CPUFeature::RNG));
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}
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[[noreturn]] void Processor::halt()
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