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using System;
using System.Runtime.InteropServices;
namespace ChocolArm64.Memory
{
static class CompareExchange128
{
private struct Int128
{
public ulong Low { get; }
public ulong High { get; }
public Int128(ulong low, ulong high)
{
Low = low;
High = high;
}
}
private delegate Int128 InterlockedCompareExchange(IntPtr address, Int128 expected, Int128 desired);
private delegate int GetCpuId();
private static InterlockedCompareExchange _interlockedCompareExchange;
static CompareExchange128()
{
if (RuntimeInformation.OSArchitecture != Architecture.X64 || !IsCmpxchg16bSupported())
{
throw new PlatformNotSupportedException();
}
byte[] interlockedCompareExchange128Code;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
interlockedCompareExchange128Code = new byte[]
{
0x53, // push rbx
0x49, 0x8b, 0x00, // mov rax, [r8]
0x49, 0x8b, 0x19, // mov rbx, [r9]
0x49, 0x89, 0xca, // mov r10, rcx
0x49, 0x89, 0xd3, // mov r11, rdx
0x49, 0x8b, 0x49, 0x08, // mov rcx, [r9+8]
0x49, 0x8b, 0x50, 0x08, // mov rdx, [r8+8]
0xf0, 0x49, 0x0f, 0xc7, 0x0b, // lock cmpxchg16b [r11]
0x49, 0x89, 0x02, // mov [r10], rax
0x4c, 0x89, 0xd0, // mov rax, r10
0x49, 0x89, 0x52, 0x08, // mov [r10+8], rdx
0x5b, // pop rbx
0xc3 // ret
};
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) ||
RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
interlockedCompareExchange128Code = new byte[]
{
0x53, // push rbx
0x49, 0x89, 0xd1, // mov r9, rdx
0x48, 0x89, 0xcb, // mov rbx, rcx
0x48, 0x89, 0xf0, // mov rax, rsi
0x4c, 0x89, 0xca, // mov rdx, r9
0x4c, 0x89, 0xc1, // mov rcx, r8
0xf0, 0x48, 0x0f, 0xc7, 0x0f, // lock cmpxchg16b [rdi]
0x5b, // pop rbx
0xc3 // ret
};
}
else
{
throw new PlatformNotSupportedException();
}
IntPtr funcPtr = MapCodeAsExecutable(interlockedCompareExchange128Code);
_interlockedCompareExchange = Marshal.GetDelegateForFunctionPointer<InterlockedCompareExchange>(funcPtr);
}
private static bool IsCmpxchg16bSupported()
{
byte[] getCpuIdCode = new byte[]
{
0x53, // push rbx
0xb8, 0x01, 0x00, 0x00, 0x00, // mov eax, 0x1
0x0f, 0xa2, // cpuid
0x89, 0xc8, // mov eax, ecx
0x5b, // pop rbx
0xc3 // ret
};
IntPtr funcPtr = MapCodeAsExecutable(getCpuIdCode);
GetCpuId getCpuId = Marshal.GetDelegateForFunctionPointer<GetCpuId>(funcPtr);
int cpuId = getCpuId();
MemoryManagement.Free(funcPtr);
return (cpuId & (1 << 13)) != 0;
}
private static IntPtr MapCodeAsExecutable(byte[] code)
{
ulong codeLength = (ulong)code.Length;
IntPtr funcPtr = MemoryManagement.Allocate(codeLength);
unsafe
{
fixed (byte* codePtr = code)
{
byte* dest = (byte*)funcPtr;
long size = (long)codeLength;
Buffer.MemoryCopy(codePtr, dest, size, size);
}
}
MemoryManagement.Reprotect(funcPtr, codeLength, MemoryProtection.Execute);
return funcPtr;
}
public static bool InterlockedCompareExchange128(
IntPtr address,
ulong expectedLow,
ulong expectedHigh,
ulong desiredLow,
ulong desiredHigh)
{
Int128 expected = new Int128(expectedLow, expectedHigh);
Int128 desired = new Int128(desiredLow, desiredHigh);
Int128 old = _interlockedCompareExchange(address, expected, desired);
return old.Low == expected.Low && old.High == expected.High;
}
public static void InterlockedRead128(IntPtr address, out ulong low, out ulong high)
{
Int128 zero = new Int128(0, 0);
Int128 old = _interlockedCompareExchange(address, zero, zero);
low = old.Low;
high = old.High;
}
}
}
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