static Pinvoke()
{
var buf = IntPtr.Zero;
try
{
// We pad the functions to 64 bytes (the length of a cacheline on the Intel processors)
var rdtscpLength = (ReturnOnlyAsm.Length & 63) != 0 ? (ReturnOnlyAsm.Length | 63) + 1 : ReturnOnlyAsm.Length;
buf = VirtualAlloc(IntPtr.Zero, (IntPtr)rdtscpLength, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if (buf == IntPtr.Zero)
{
throw new Win32Exception();
}
Marshal.Copy(ReturnOnlyAsm, 0, buf, ReturnOnlyAsm.Length);
for (var i = ReturnOnlyAsm.Length; i < rdtscpLength; i++)
{
Marshal.WriteByte(buf, i, 0x90); // nop
}
// Change the access of the allocated memory from R/W to Execute
var result = VirtualProtect(buf, (IntPtr)rdtscpLength, PAGE_EXECUTE, out var oldProtection);
if (!result)
{
throw new Win32Exception();
}
// Create a delegate to the "function"
Empty = (FuncUInt64)Marshal.GetDelegateForFunctionPointer(buf, typeof(FuncUInt64));
buf = IntPtr.Zero;
}
finally
{
if (buf != IntPtr.Zero)
{
VirtualFree(buf, IntPtr.Zero, MEM_RELEASE);
}
}
}
static Rdtsc()
{
SystemInfo systemInfo;
GetNativeSystemInfo(out systemInfo);
if (systemInfo.wProcessorArchitecture != 0 /* PROCESSOR_ARCHITECTURE_INTEL */ &&
systemInfo.wProcessorArchitecture != 9 /* PROCESSOR_ARCHITECTURE_AMD64 */)
{
// Fallback for ARM/IA64/...
Timestamp = StopwatchGetTimestamp;
TimestampP = StopwatchGetTimestamp;
IsRdtscSupported = false;
IsRdtscPSupported = false;
return;
}
byte[] cpuid, rdtsc, rdtscp, rdtsccpuid;
IsRdtscSupported = true;
// Assembly generated with https://defuse.ca/online-x86-assembler.htm
if (Environment.Is64BitProcess)
{
/* CPUID x64:
* push rbx;
* mov eax, 0x80000000;
* cpuid;
* mov ebx, 0x80000001;
* cmp eax, ebx;
* jb Error;
* mov eax, ebx;
* cpuid;
* mov eax, ecx;
* shl rax, 0x20;
* or rax, rdx
* jmp End;
* Error:
* xor rax, rax;
* End:
* pop rbx;
* ret;
* 0: 53 push rbx
* 1: b8 00 00 00 80 mov eax,0x80000000
* 6: 0f a2 cpuid
* 8: bb 01 00 00 80 mov ebx,0x80000001
* d: 39 d8 cmp eax,ebx
* f: 72 0f jb 20 <Error>
* 11: 89 d8 mov eax,ebx
* 13: 0f a2 cpuid
* 15: 89 c8 mov eax,ecx
* 17: 48 c1 e0 20 shl rax,0x20
* 1b: 48 09 d0 or rax,rdx
* 1e: eb 03 jmp 23 <End>
* 0000000000000020 <Error>:
* 20: 48 31 c0 xor rax,rax
* 0000000000000023 <End>:
* 23: 5b pop rbx
* 24: c3 ret
*/
cpuid = new byte[] { 0x53, 0xB8, 0x00, 0x00, 0x00, 0x80, 0x0F, 0xA2, 0xBB, 0x01, 0x00, 0x00, 0x80, 0x39, 0xD8, 0x72, 0x16, 0x89, 0xD8, 0x48, 0xC7, 0xC2, 0xFF, 0xFF, 0xFF, 0xFF, 0x0F, 0xA2, 0x89, 0xC8, 0x48, 0xC1, 0xE0, 0x20, 0x48, 0x09, 0xD0, 0xEB, 0x03, 0x48, 0x31, 0xC0, 0x5B, 0xC3 };
/* RDTSC x64:
* rdtsc;
* shl rdx, 0x20;
* or rax,rdx;
* ret;
* 0: 0f 31 rdtsc
* 2: 48 c1 e2 20 shl rdx,0x20
* 6: 48 09 d0 or rax,rdx
* 9: c3 ret
*/
rdtsc = new byte[] { 0x0F, 0x31, 0x48, 0xC1, 0xE2, 0x20, 0x48, 0x09, 0xD0, 0xC3 };
/* RDTSCP x64
* rdtscp;
* shl rdx, 0x20;
* or rax, rdx;
* ret;
* 0: 0f 01 f9 rdtscp
* 3: 48 c1 e2 20 shl rdx,0x20
* 7: 48 09 d0 or rax,rdx
* a: c3 ret
*/
rdtscp = new byte[] { 0x0F, 0x01, 0xF9, 0x48, 0xC1, 0xE2, 0x20, 0x48, 0x09, 0xD0, 0xC3 };
/* RDTSC + CPUID x64
* push rbx;
* xor eax, eax;
* cpuid;
* rdtsc;
* shl rdx, 0x20;
* or rax, rdx;
* pop rbx;
* ret;
* 0: 53 push rbx
* 1: 31 c0 xor eax,eax
* 3: 0f a2 cpuid
* 5: 0f 31 rdtsc
* 7: 48 c1 e2 20 shl rdx,0x20
* b: 48 09 d0 or rax,rdx
* e: 5b pop rbx
* f: c3 ret
*/
rdtsccpuid = new byte[] { 0x53, 0x31, 0xC0, 0x0F, 0xA2, 0x0F, 0x31, 0x48, 0xC1, 0xE2, 0x20, 0x48, 0x09, 0xD0, 0x5B, 0xC3 };
}
else
{
/* CPUID x86:
* push ebx;
* mov eax, 0x80000000;
* cpuid;
* mov ebx, 0x80000001;
* cmp eax, ebx;
* jb Error;
* mov eax, ebx;
* cpuid;
* mov eax, edx;
* mov edx, ecx;
* jmp End;
* Error:
* xor eax, eax;
* xor edx, edx;
* End:
* pop ebx;
* ret;
* 0: 53 push ebx
* 1: b8 00 00 00 80 mov eax,0x80000000
* 6: 0f a2 cpuid
* 8: bb 01 00 00 80 mov ebx,0x80000001
* d: 39 d8 cmp eax,ebx
* f: 72 0a jb 1b <Error>
* 11: 89 d8 mov eax,ebx
* 13: 0f a2 cpuid
* 15: 89 d0 mov eax,edx
* 17: 89 ca mov edx,ecx
* 19: eb 04 jmp 1f <End>
* 0000001b <Error>:
* 1b: 31 c0 xor eax,eax
* 1d: 31 d2 xor edx,edx
* 0000001f <End>:
* 1f: 5b pop ebx
* 20: c3 ret
*/
cpuid = new byte[] { 0x53, 0xB8, 0x00, 0x00, 0x00, 0x80, 0x0F, 0xA2, 0xBB, 0x01, 0x00, 0x00, 0x80, 0x39, 0xD8, 0x72, 0x0A, 0x89, 0xD8, 0x0F, 0xA2, 0x89, 0xD0, 0x89, 0xCA, 0xEB, 0x04, 0x31, 0xC0, 0x31, 0xD2, 0x5B, 0xC3 };
/* RDTSC x86:
* rdtsc;
* ret;
* 0: 0f 31 rdtsc
* 2: c3 ret
*/
rdtsc = new byte[] { 0x0F, 0x31, 0xC3 };
/* RDTSCP x86
* rdtscp;
* ret;
* 0: 0f 01 f9 rdtscp
* 3: c3 ret
*/
rdtscp = new byte[] { 0x0F, 0x01, 0xF9, 0xC3 };
/* RDTSC + CPUID x86
* push ebx;
* xor eax,eax;
* cpuid;
* rdtsc;
* pop ebx;
* ret;
* 0: 53 push ebx
* 1: 31 c0 xor eax,eax
* 3: 0f a2 cpuid
* 5: 0f 31 rdtsc
* 7: 5b pop ebx
* 8: c3 ret
*/
rdtsccpuid = new byte[] { 0x53, 0x31, 0xC0, 0x0F, 0xA2, 0x0F, 0x31, 0x5B, 0xC3 };
}
IntPtr buf = IntPtr.Zero;
try
{
// We pad the functions to 64 bytes (the length of a cache
// line on the Intel processors)
int cpuidLength = (cpuid.Length & 63) != 0 ? (cpuid.Length | 63) + 1 : cpuid.Length;
int rdtscLength = (rdtsc.Length & 63) != 0 ? (rdtsc.Length | 63) + 1 : rdtsc.Length;
int rdtscpLength = (rdtscp.Length & 63) != 0 ? (rdtscp.Length | 63) + 1 : rdtscp.Length;
int rdtsccpuidLength = (rdtsccpuid.Length & 63) != 0 ? (rdtsccpuid.Length | 63) + 1 : rdtsccpuid.Length;
// We don't know which one of rdtscp or rdtsccpuid we will
// use, so we calculate space for the biggest one.
// Note that it is very unlikely that we will go over 4096
// bytes (the minimum size of memory allocated by
// VirtualAlloc)
int totalLength = cpuidLength + rdtscLength + Math.Max(rdtscpLength, rdtsccpuidLength);
// We VirtualAlloc totalLength bytes, with R/W access
// Note that from what I've read, MEM_RESERVE is useless
// if the first parameter is IntPtr.Zero
buf = VirtualAlloc(IntPtr.Zero, (IntPtr)totalLength, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if (buf == IntPtr.Zero)
{
throw new Win32Exception();
}
// Copy cpuid instructions in the buf
Marshal.Copy(cpuid, 0, buf, cpuid.Length);
for (int i = cpuid.Length; i < cpuidLength; i++)
{
Marshal.WriteByte(buf, i, 0x90); // nop
}
// Copy rdtsc instructions in the buf
Marshal.Copy(rdtsc, 0, buf + cpuidLength, rdtsc.Length);
for (int i = rdtsc.Length; i < rdtscLength; i++)
{
Marshal.WriteByte(buf, cpuidLength + i, 0x90); // nop
}
var cpuidFunc = (FuncUInt64)Marshal.GetDelegateForFunctionPointer(buf, typeof(FuncUInt64));
// We use cpuid, EAX=0x80000001 to check for the rdtscp
ulong supportedFeatures = cpuidFunc();
byte[] rdtscpSelected;
int rdtscpSelectedLength;
// Check the rdtscp flag
if ((supportedFeatures & (1L << 27)) != 0)
{
// rdtscp supported
rdtscpSelected = rdtscp;
rdtscpSelectedLength = rdtscpLength;
IsRdtscPSupported = true;
}
else
{
// rdtscp not supported. We use cpuid + rdtsc
rdtscpSelected = rdtsccpuid;
rdtscpSelectedLength = rdtsccpuidLength;
IsRdtscPSupported = false;
}
// Copy rdtscp/rdtsccpuid instructions in the buf
Marshal.Copy(rdtscpSelected, 0, buf + cpuidLength + rdtscLength, rdtscpSelected.Length);
for (int i = rdtscpSelected.Length; i < rdtscpSelectedLength; i++)
{
Marshal.WriteByte(buf, cpuidLength + rdtscLength + i, 0x90); // nop
}
// Change the access of the allocated memory from R/W to Execute
uint oldProtection;
bool result = VirtualProtect(buf, (IntPtr)totalLength, PAGE_EXECUTE, out oldProtection);
if (!result)
{
throw new Win32Exception();
}
// Create a delegate to the "function"
Timestamp = (FuncUInt64)Marshal.GetDelegateForFunctionPointer(buf + cpuidLength, typeof(FuncUInt64));
TimestampP = (FuncUInt64)Marshal.GetDelegateForFunctionPointer(buf + cpuidLength + rdtscLength, typeof(FuncUInt64));
buf = IntPtr.Zero;
}
finally
{
// There was an error!
if (buf != IntPtr.Zero)
{
// Free the allocated memory
bool result = VirtualFree(buf, IntPtr.Zero, MEM_RELEASE);
if (!result)
{
throw new Win32Exception();
}
}
}
}
