Kernel/core/random.cpp

/*
	This file is part of Fennix Kernel.

	Fennix Kernel is free software: you can redistribute it and/or
	modify it under the terms of the GNU General Public License as
	published by the Free Software Foundation, either version 3 of
	the License, or (at your option) any later version.

	Fennix Kernel is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
*/

#include <rand.hpp>
#include <cpu.hpp>

namespace Random
{
	static uint64_t Seed = 0xdeadbeef;

	uint16_t rand16()
	{
#if defined(a86)
		static int RDRANDFlag = 0x1A1A;
		if (unlikely(RDRANDFlag == 0x1A1A))
		{
			if (strcmp(CPU::Hypervisor(), x86_CPUID_VENDOR_TCG) != 0)
			{
				if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_AMD) == 0)
				{
					CPU::x86::AMD::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
				else if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_INTEL) == 0)
				{
					CPU::x86::Intel::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
			}
			else
				RDRANDFlag = 0;
		}

		if (RDRANDFlag)
		{
			uint16_t RDRANDValue = 0;
			asmv("1: rdrand %0; jnc 1b"
				 : "=r"(RDRANDValue));
			return RDRANDValue;
		}

		Seed = Seed * 1103515245 + 12345;
		return (uint16_t)(Seed / 65536) % __UINT16_MAX__;
#endif
		return 0;
	}

	uint32_t rand32()
	{
#if defined(a86)
		static int RDRANDFlag = 0x1A1A;
		if (unlikely(RDRANDFlag == 0x1A1A))
		{
			if (strcmp(CPU::Hypervisor(), x86_CPUID_VENDOR_TCG) != 0)
			{
				if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_AMD) == 0)
				{
					CPU::x86::AMD::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
				else if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_INTEL) == 0)
				{
					CPU::x86::Intel::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
			}
			else
				RDRANDFlag = 0;
		}

		if (RDRANDFlag)
		{
			uint32_t RDRANDValue = 0;
			asmv("1: rdrand %0; jnc 1b"
				 : "=r"(RDRANDValue));
			return RDRANDValue;
		}

		Seed = Seed * 1103515245 + 12345;
		return (uint32_t)(Seed / 65536) % __UINT32_MAX__;
#endif
		return 0;
	}

	uint64_t rand64()
	{
#if defined(a86)
		static int RDRANDFlag = 0x1A1A;
		if (unlikely(RDRANDFlag == 0x1A1A))
		{
			if (strcmp(CPU::Hypervisor(), x86_CPUID_VENDOR_TCG) != 0)
			{
				if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_AMD) == 0)
				{
					CPU::x86::AMD::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
				else if (strcmp(CPU::Vendor(), x86_CPUID_VENDOR_INTEL) == 0)
				{
					CPU::x86::Intel::CPUID0x00000001 cpuid;
					cpuid.Get();
					RDRANDFlag = cpuid.ECX.RDRAND;
				}
			}
			else
				RDRANDFlag = 0;
		}

		if (RDRANDFlag)
		{
			uintptr_t RDRANDValue = 0;
			asmv("1: rdrand %0; jnc 1b"
				 : "=r"(RDRANDValue));
			return RDRANDValue;
		}

		Seed = Seed * 1103515245 + 12345;
		return (uint64_t)(Seed / 65536) % __UINT64_MAX__;
#endif
		return 0;
	}

	void ChangeSeed(uint64_t CustomSeed) { Seed = CustomSeed; }
}