Source file src/runtime/os_windows.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  import (
     8  	"internal/abi"
     9  	"internal/runtime/atomic"
    10  	"internal/runtime/sys"
    11  	"internal/runtime/syscall/windows"
    12  	"unsafe"
    13  )
    14  
    15  // TODO(brainman): should not need those
    16  const (
    17  	_NSIG = 65
    18  )
    19  
    20  //go:cgo_import_dynamic runtime._AddVectoredContinueHandler AddVectoredContinueHandler%2 "kernel32.dll"
    21  //go:cgo_import_dynamic runtime._AddVectoredExceptionHandler AddVectoredExceptionHandler%2 "kernel32.dll"
    22  //go:cgo_import_dynamic runtime._CloseHandle CloseHandle%1 "kernel32.dll"
    23  //go:cgo_import_dynamic runtime._CreateEventA CreateEventA%4 "kernel32.dll"
    24  //go:cgo_import_dynamic runtime._CreateIoCompletionPort CreateIoCompletionPort%4 "kernel32.dll"
    25  //go:cgo_import_dynamic runtime._CreateThread CreateThread%6 "kernel32.dll"
    26  //go:cgo_import_dynamic runtime._CreateWaitableTimerA CreateWaitableTimerA%3 "kernel32.dll"
    27  //go:cgo_import_dynamic runtime._CreateWaitableTimerExW CreateWaitableTimerExW%4 "kernel32.dll"
    28  //go:cgo_import_dynamic runtime._DuplicateHandle DuplicateHandle%7 "kernel32.dll"
    29  //go:cgo_import_dynamic runtime._ExitProcess ExitProcess%1 "kernel32.dll"
    30  //go:cgo_import_dynamic runtime._FreeEnvironmentStringsW FreeEnvironmentStringsW%1 "kernel32.dll"
    31  //go:cgo_import_dynamic runtime._GetConsoleMode GetConsoleMode%2 "kernel32.dll"
    32  //go:cgo_import_dynamic runtime._GetCurrentThreadId GetCurrentThreadId%0 "kernel32.dll"
    33  //go:cgo_import_dynamic runtime._GetEnvironmentStringsW GetEnvironmentStringsW%0 "kernel32.dll"
    34  //go:cgo_import_dynamic runtime._GetErrorMode GetErrorMode%0 "kernel32.dll"
    35  //go:cgo_import_dynamic runtime._GetProcAddress GetProcAddress%2 "kernel32.dll"
    36  //go:cgo_import_dynamic runtime._GetProcessAffinityMask GetProcessAffinityMask%3 "kernel32.dll"
    37  //go:cgo_import_dynamic runtime._GetQueuedCompletionStatusEx GetQueuedCompletionStatusEx%6 "kernel32.dll"
    38  //go:cgo_import_dynamic runtime._GetStdHandle GetStdHandle%1 "kernel32.dll"
    39  //go:cgo_import_dynamic runtime._GetSystemDirectoryA GetSystemDirectoryA%2 "kernel32.dll"
    40  //go:cgo_import_dynamic runtime._GetSystemInfo GetSystemInfo%1 "kernel32.dll"
    41  //go:cgo_import_dynamic runtime._GetThreadContext GetThreadContext%2 "kernel32.dll"
    42  //go:cgo_import_dynamic runtime._SetThreadContext SetThreadContext%2 "kernel32.dll"
    43  //go:cgo_import_dynamic runtime._LoadLibraryExW LoadLibraryExW%3 "kernel32.dll"
    44  //go:cgo_import_dynamic runtime._PostQueuedCompletionStatus PostQueuedCompletionStatus%4 "kernel32.dll"
    45  //go:cgo_import_dynamic runtime._QueryPerformanceCounter QueryPerformanceCounter%1 "kernel32.dll"
    46  //go:cgo_import_dynamic runtime._QueryPerformanceFrequency QueryPerformanceFrequency%1 "kernel32.dll"
    47  //go:cgo_import_dynamic runtime._RaiseFailFastException RaiseFailFastException%3 "kernel32.dll"
    48  //go:cgo_import_dynamic runtime._ResumeThread ResumeThread%1 "kernel32.dll"
    49  //go:cgo_import_dynamic runtime._RtlLookupFunctionEntry RtlLookupFunctionEntry%3 "kernel32.dll"
    50  //go:cgo_import_dynamic runtime._RtlVirtualUnwind  RtlVirtualUnwind%8 "kernel32.dll"
    51  //go:cgo_import_dynamic runtime._SetConsoleCtrlHandler SetConsoleCtrlHandler%2 "kernel32.dll"
    52  //go:cgo_import_dynamic runtime._SetErrorMode SetErrorMode%1 "kernel32.dll"
    53  //go:cgo_import_dynamic runtime._SetEvent SetEvent%1 "kernel32.dll"
    54  //go:cgo_import_dynamic runtime._SetProcessPriorityBoost SetProcessPriorityBoost%2 "kernel32.dll"
    55  //go:cgo_import_dynamic runtime._SetThreadPriority SetThreadPriority%2 "kernel32.dll"
    56  //go:cgo_import_dynamic runtime._SetUnhandledExceptionFilter SetUnhandledExceptionFilter%1 "kernel32.dll"
    57  //go:cgo_import_dynamic runtime._SetWaitableTimer SetWaitableTimer%6 "kernel32.dll"
    58  //go:cgo_import_dynamic runtime._SuspendThread SuspendThread%1 "kernel32.dll"
    59  //go:cgo_import_dynamic runtime._SwitchToThread SwitchToThread%0 "kernel32.dll"
    60  //go:cgo_import_dynamic runtime._TlsAlloc TlsAlloc%0 "kernel32.dll"
    61  //go:cgo_import_dynamic runtime._VirtualAlloc VirtualAlloc%4 "kernel32.dll"
    62  //go:cgo_import_dynamic runtime._VirtualFree VirtualFree%3 "kernel32.dll"
    63  //go:cgo_import_dynamic runtime._VirtualQuery VirtualQuery%3 "kernel32.dll"
    64  //go:cgo_import_dynamic runtime._WaitForSingleObject WaitForSingleObject%2 "kernel32.dll"
    65  //go:cgo_import_dynamic runtime._WaitForMultipleObjects WaitForMultipleObjects%4 "kernel32.dll"
    66  //go:cgo_import_dynamic runtime._WerGetFlags WerGetFlags%2 "kernel32.dll"
    67  //go:cgo_import_dynamic runtime._WerSetFlags WerSetFlags%1 "kernel32.dll"
    68  //go:cgo_import_dynamic runtime._WriteConsoleW WriteConsoleW%5 "kernel32.dll"
    69  //go:cgo_import_dynamic runtime._WriteFile WriteFile%5 "kernel32.dll"
    70  
    71  type stdFunction unsafe.Pointer
    72  
    73  var (
    74  	// Following syscalls are available on every Windows PC.
    75  	// All these variables are set by the Windows executable
    76  	// loader before the Go program starts.
    77  	_AddVectoredContinueHandler,
    78  	_AddVectoredExceptionHandler,
    79  	_CloseHandle,
    80  	_CreateEventA,
    81  	_CreateIoCompletionPort,
    82  	_CreateThread,
    83  	_CreateWaitableTimerA,
    84  	_CreateWaitableTimerExW,
    85  	_DuplicateHandle,
    86  	_ExitProcess,
    87  	_FreeEnvironmentStringsW,
    88  	_GetConsoleMode,
    89  	_GetCurrentThreadId,
    90  	_GetEnvironmentStringsW,
    91  	_GetErrorMode,
    92  	_GetProcAddress,
    93  	_GetProcessAffinityMask,
    94  	_GetQueuedCompletionStatusEx,
    95  	_GetStdHandle,
    96  	_GetSystemDirectoryA,
    97  	_GetSystemInfo,
    98  	_GetThreadContext,
    99  	_SetThreadContext,
   100  	_LoadLibraryExW,
   101  	_PostQueuedCompletionStatus,
   102  	_QueryPerformanceCounter,
   103  	_QueryPerformanceFrequency,
   104  	_RaiseFailFastException,
   105  	_ResumeThread,
   106  	_RtlLookupFunctionEntry,
   107  	_RtlVirtualUnwind,
   108  	_SetConsoleCtrlHandler,
   109  	_SetErrorMode,
   110  	_SetEvent,
   111  	_SetProcessPriorityBoost,
   112  	_SetThreadPriority,
   113  	_SetUnhandledExceptionFilter,
   114  	_SetWaitableTimer,
   115  	_SuspendThread,
   116  	_SwitchToThread,
   117  	_TlsAlloc,
   118  	_VirtualAlloc,
   119  	_VirtualFree,
   120  	_VirtualQuery,
   121  	_WaitForSingleObject,
   122  	_WaitForMultipleObjects,
   123  	_WerGetFlags,
   124  	_WerSetFlags,
   125  	_WriteConsoleW,
   126  	_WriteFile,
   127  	_ stdFunction
   128  
   129  	// Use ProcessPrng to generate cryptographically random data.
   130  	_ProcessPrng stdFunction
   131  
   132  	// Load ntdll.dll manually during startup, otherwise Mingw
   133  	// links wrong printf function to cgo executable (see issue
   134  	// 12030 for details).
   135  	_NtCreateWaitCompletionPacket    stdFunction
   136  	_NtAssociateWaitCompletionPacket stdFunction
   137  	_NtCancelWaitCompletionPacket    stdFunction
   138  	_RtlGetCurrentPeb                stdFunction
   139  	_RtlGetVersion                   stdFunction
   140  
   141  	// These are from non-kernel32.dll, so we prefer to LoadLibraryEx them.
   142  	_timeBeginPeriod,
   143  	_timeEndPeriod,
   144  	_ stdFunction
   145  )
   146  
   147  var (
   148  	bcryptprimitivesdll = [...]uint16{'b', 'c', 'r', 'y', 'p', 't', 'p', 'r', 'i', 'm', 'i', 't', 'i', 'v', 'e', 's', '.', 'd', 'l', 'l', 0}
   149  	ntdlldll            = [...]uint16{'n', 't', 'd', 'l', 'l', '.', 'd', 'l', 'l', 0}
   150  	powrprofdll         = [...]uint16{'p', 'o', 'w', 'r', 'p', 'r', 'o', 'f', '.', 'd', 'l', 'l', 0}
   151  	winmmdll            = [...]uint16{'w', 'i', 'n', 'm', 'm', '.', 'd', 'l', 'l', 0}
   152  )
   153  
   154  // Function to be called by windows CreateThread
   155  // to start new os thread.
   156  func tstart_stdcall(newm *m)
   157  
   158  // Init-time helper
   159  func wintls()
   160  
   161  type mOS struct {
   162  	// This is here to avoid using the G stack so the stack can move during the call.
   163  	stdCallInfo windows.StdCallInfo
   164  
   165  	threadLock mutex   // protects "thread" and prevents closing
   166  	thread     uintptr // thread handle
   167  
   168  	waitsema   uintptr // semaphore for parking on locks
   169  	resumesema uintptr // semaphore to indicate suspend/resume
   170  
   171  	highResTimer   uintptr // high resolution timer handle used in usleep
   172  	waitIocpTimer  uintptr // high resolution timer handle used in netpoll
   173  	waitIocpHandle uintptr // wait completion handle used in netpoll
   174  
   175  	// preemptExtLock synchronizes preemptM with entry/exit from
   176  	// external C code.
   177  	//
   178  	// This protects against races between preemptM calling
   179  	// SuspendThread and external code on this thread calling
   180  	// ExitProcess. If these happen concurrently, it's possible to
   181  	// exit the suspending thread and suspend the exiting thread,
   182  	// leading to deadlock.
   183  	//
   184  	// 0 indicates this M is not being preempted or in external
   185  	// code. Entering external code CASes this from 0 to 1. If
   186  	// this fails, a preemption is in progress, so the thread must
   187  	// wait for the preemption. preemptM also CASes this from 0 to
   188  	// 1. If this fails, the preemption fails (as it would if the
   189  	// PC weren't in Go code). The value is reset to 0 when
   190  	// returning from external code or after a preemption is
   191  	// complete.
   192  	//
   193  	// TODO(austin): We may not need this if preemption were more
   194  	// tightly synchronized on the G/P status and preemption
   195  	// blocked transition into _Gsyscall/_Psyscall.
   196  	preemptExtLock uint32
   197  }
   198  
   199  // Stubs so tests can link correctly. These should never be called.
   200  func open(name *byte, mode, perm int32) int32 {
   201  	throw("unimplemented")
   202  	return -1
   203  }
   204  func closefd(fd int32) int32 {
   205  	throw("unimplemented")
   206  	return -1
   207  }
   208  func read(fd int32, p unsafe.Pointer, n int32) int32 {
   209  	throw("unimplemented")
   210  	return -1
   211  }
   212  
   213  type sigset struct{}
   214  
   215  var asmstdcallAddr unsafe.Pointer
   216  
   217  type winlibcall windows.StdCallInfo
   218  
   219  func windowsFindfunc(lib uintptr, name []byte) stdFunction {
   220  	if name[len(name)-1] != 0 {
   221  		throw("usage")
   222  	}
   223  	f := stdcall(_GetProcAddress, lib, uintptr(unsafe.Pointer(&name[0])))
   224  	return stdFunction(unsafe.Pointer(f))
   225  }
   226  
   227  const _MAX_PATH = 260 // https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
   228  var sysDirectory [_MAX_PATH + 1]byte
   229  var sysDirectoryLen uintptr
   230  
   231  func initSysDirectory() {
   232  	l := stdcall(_GetSystemDirectoryA, uintptr(unsafe.Pointer(&sysDirectory[0])), uintptr(len(sysDirectory)-1))
   233  	if l == 0 || l > uintptr(len(sysDirectory)-1) {
   234  		throw("Unable to determine system directory")
   235  	}
   236  	sysDirectory[l] = '\\'
   237  	sysDirectoryLen = l + 1
   238  }
   239  
   240  //go:linkname windows_GetSystemDirectory internal/syscall/windows.GetSystemDirectory
   241  func windows_GetSystemDirectory() string {
   242  	return unsafe.String(&sysDirectory[0], sysDirectoryLen)
   243  }
   244  
   245  func windowsLoadSystemLib(name []uint16) uintptr {
   246  	const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
   247  	return stdcall(_LoadLibraryExW, uintptr(unsafe.Pointer(&name[0])), 0, _LOAD_LIBRARY_SEARCH_SYSTEM32)
   248  }
   249  
   250  //go:linkname windows_QueryPerformanceCounter internal/syscall/windows.QueryPerformanceCounter
   251  func windows_QueryPerformanceCounter() int64 {
   252  	var counter int64
   253  	stdcall(_QueryPerformanceCounter, uintptr(unsafe.Pointer(&counter)))
   254  	return counter
   255  }
   256  
   257  //go:linkname windows_QueryPerformanceFrequency internal/syscall/windows.QueryPerformanceFrequency
   258  func windows_QueryPerformanceFrequency() int64 {
   259  	var frequency int64
   260  	stdcall(_QueryPerformanceFrequency, uintptr(unsafe.Pointer(&frequency)))
   261  	return frequency
   262  }
   263  
   264  func loadOptionalSyscalls() {
   265  	bcryptPrimitives := windowsLoadSystemLib(bcryptprimitivesdll[:])
   266  	if bcryptPrimitives == 0 {
   267  		throw("bcryptprimitives.dll not found")
   268  	}
   269  	_ProcessPrng = windowsFindfunc(bcryptPrimitives, []byte("ProcessPrng\000"))
   270  
   271  	n32 := windowsLoadSystemLib(ntdlldll[:])
   272  	if n32 == 0 {
   273  		throw("ntdll.dll not found")
   274  	}
   275  	_NtCreateWaitCompletionPacket = windowsFindfunc(n32, []byte("NtCreateWaitCompletionPacket\000"))
   276  	if _NtCreateWaitCompletionPacket != nil {
   277  		// These functions should exists if NtCreateWaitCompletionPacket exists.
   278  		_NtAssociateWaitCompletionPacket = windowsFindfunc(n32, []byte("NtAssociateWaitCompletionPacket\000"))
   279  		if _NtAssociateWaitCompletionPacket == nil {
   280  			throw("NtCreateWaitCompletionPacket exists but NtAssociateWaitCompletionPacket does not")
   281  		}
   282  		_NtCancelWaitCompletionPacket = windowsFindfunc(n32, []byte("NtCancelWaitCompletionPacket\000"))
   283  		if _NtCancelWaitCompletionPacket == nil {
   284  			throw("NtCreateWaitCompletionPacket exists but NtCancelWaitCompletionPacket does not")
   285  		}
   286  	}
   287  	_RtlGetCurrentPeb = windowsFindfunc(n32, []byte("RtlGetCurrentPeb\000"))
   288  	_RtlGetVersion = windowsFindfunc(n32, []byte("RtlGetVersion\000"))
   289  }
   290  
   291  func monitorSuspendResume() {
   292  	const (
   293  		_DEVICE_NOTIFY_CALLBACK = 2
   294  	)
   295  	type _DEVICE_NOTIFY_SUBSCRIBE_PARAMETERS struct {
   296  		callback uintptr
   297  		context  uintptr
   298  	}
   299  
   300  	powrprof := windowsLoadSystemLib(powrprofdll[:])
   301  	if powrprof == 0 {
   302  		return // Running on Windows 7, where we don't need it anyway.
   303  	}
   304  	powerRegisterSuspendResumeNotification := windowsFindfunc(powrprof, []byte("PowerRegisterSuspendResumeNotification\000"))
   305  	if powerRegisterSuspendResumeNotification == nil {
   306  		return // Running on Windows 7, where we don't need it anyway.
   307  	}
   308  	var fn any = func(context uintptr, changeType uint32, setting uintptr) uintptr {
   309  		for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
   310  			if mp.resumesema != 0 {
   311  				stdcall(_SetEvent, mp.resumesema)
   312  			}
   313  		}
   314  		return 0
   315  	}
   316  	params := _DEVICE_NOTIFY_SUBSCRIBE_PARAMETERS{
   317  		callback: compileCallback(*efaceOf(&fn), true),
   318  	}
   319  	handle := uintptr(0)
   320  	stdcall(powerRegisterSuspendResumeNotification, _DEVICE_NOTIFY_CALLBACK,
   321  		uintptr(unsafe.Pointer(&params)), uintptr(unsafe.Pointer(&handle)))
   322  }
   323  
   324  func getCPUCount() int32 {
   325  	var mask, sysmask uintptr
   326  	ret := stdcall(_GetProcessAffinityMask, windows.CurrentProcess, uintptr(unsafe.Pointer(&mask)), uintptr(unsafe.Pointer(&sysmask)))
   327  	if ret != 0 {
   328  		n := 0
   329  		maskbits := int(unsafe.Sizeof(mask) * 8)
   330  		for i := 0; i < maskbits; i++ {
   331  			if mask&(1<<uint(i)) != 0 {
   332  				n++
   333  			}
   334  		}
   335  		if n != 0 {
   336  			return int32(n)
   337  		}
   338  	}
   339  	// use GetSystemInfo if GetProcessAffinityMask fails
   340  	var info windows.SystemInfo
   341  	stdcall(_GetSystemInfo, uintptr(unsafe.Pointer(&info)))
   342  	return int32(info.NumberOfProcessors)
   343  }
   344  
   345  func getPageSize() uintptr {
   346  	var info windows.SystemInfo
   347  	stdcall(_GetSystemInfo, uintptr(unsafe.Pointer(&info)))
   348  	return uintptr(info.PageSize)
   349  }
   350  
   351  // in sys_windows_386.s and sys_windows_amd64.s:
   352  func getlasterror() uint32
   353  
   354  var timeBeginPeriodRetValue uint32
   355  
   356  // osRelaxMinNS indicates that sysmon shouldn't osRelax if the next
   357  // timer is less than 60 ms from now. Since osRelaxing may reduce
   358  // timer resolution to 15.6 ms, this keeps timer error under roughly 1
   359  // part in 4.
   360  const osRelaxMinNS = 60 * 1e6
   361  
   362  // osRelax is called by the scheduler when transitioning to and from
   363  // all Ps being idle.
   364  //
   365  // Some versions of Windows have high resolution timer. For those
   366  // versions osRelax is noop.
   367  // For Windows versions without high resolution timer, osRelax
   368  // adjusts the system-wide timer resolution. Go needs a
   369  // high resolution timer while running and there's little extra cost
   370  // if we're already using the CPU, but if all Ps are idle there's no
   371  // need to consume extra power to drive the high-res timer.
   372  func osRelax(relax bool) uint32 {
   373  	if haveHighResTimer {
   374  		// If the high resolution timer is available, the runtime uses the timer
   375  		// to sleep for short durations. This means there's no need to adjust
   376  		// the global clock frequency.
   377  		return 0
   378  	}
   379  
   380  	if relax {
   381  		return uint32(stdcall(_timeEndPeriod, 1))
   382  	} else {
   383  		return uint32(stdcall(_timeBeginPeriod, 1))
   384  	}
   385  }
   386  
   387  // haveHighResTimer indicates that the CreateWaitableTimerEx
   388  // CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag is available.
   389  var haveHighResTimer = false
   390  
   391  // haveHighResSleep indicates that NtCreateWaitCompletionPacket
   392  // exists and haveHighResTimer is true.
   393  // NtCreateWaitCompletionPacket has been available since Windows 10,
   394  // but has just been publicly documented, so some platforms, like Wine,
   395  // doesn't support it yet.
   396  var haveHighResSleep = false
   397  
   398  // createHighResTimer calls CreateWaitableTimerEx with
   399  // CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag to create high
   400  // resolution timer. createHighResTimer returns new timer
   401  // handle or 0, if CreateWaitableTimerEx failed.
   402  func createHighResTimer() uintptr {
   403  	// As per @jstarks, see
   404  	// https://github.com/golang/go/issues/8687#issuecomment-656259353
   405  	return stdcall(_CreateWaitableTimerExW, 0, 0,
   406  		windows.CREATE_WAITABLE_TIMER_HIGH_RESOLUTION,
   407  		windows.SYNCHRONIZE|windows.TIMER_QUERY_STATE|windows.TIMER_MODIFY_STATE)
   408  }
   409  
   410  func initHighResTimer() {
   411  	h := createHighResTimer()
   412  	if h != 0 {
   413  		haveHighResTimer = true
   414  		haveHighResSleep = _NtCreateWaitCompletionPacket != nil
   415  		stdcall(_CloseHandle, h)
   416  	} else {
   417  		// Only load winmm.dll if we need it.
   418  		// This avoids a dependency on winmm.dll for Go programs
   419  		// that run on new Windows versions.
   420  		m32 := windowsLoadSystemLib(winmmdll[:])
   421  		if m32 == 0 {
   422  			print("runtime: LoadLibraryExW failed; errno=", getlasterror(), "\n")
   423  			throw("winmm.dll not found")
   424  		}
   425  		_timeBeginPeriod = windowsFindfunc(m32, []byte("timeBeginPeriod\000"))
   426  		_timeEndPeriod = windowsFindfunc(m32, []byte("timeEndPeriod\000"))
   427  		if _timeBeginPeriod == nil || _timeEndPeriod == nil {
   428  			print("runtime: GetProcAddress failed; errno=", getlasterror(), "\n")
   429  			throw("timeBegin/EndPeriod not found")
   430  		}
   431  	}
   432  }
   433  
   434  //go:linkname canUseLongPaths internal/syscall/windows.CanUseLongPaths
   435  var canUseLongPaths bool
   436  
   437  // initLongPathSupport enables long path support.
   438  func initLongPathSupport() {
   439  	const (
   440  		IsLongPathAwareProcess = 0x80
   441  		PebBitFieldOffset      = 3
   442  	)
   443  
   444  	// Check that we're ≥ 10.0.15063.
   445  	info := windows.OSVERSIONINFOW{}
   446  	info.OSVersionInfoSize = uint32(unsafe.Sizeof(info))
   447  	stdcall(_RtlGetVersion, uintptr(unsafe.Pointer(&info)))
   448  	if info.MajorVersion < 10 || (info.MajorVersion == 10 && info.MinorVersion == 0 && info.BuildNumber < 15063) {
   449  		return
   450  	}
   451  
   452  	// Set the IsLongPathAwareProcess flag of the PEB's bit field.
   453  	// This flag is not documented, but it's known to be used
   454  	// by Windows to enable long path support.
   455  	bitField := (*byte)(unsafe.Pointer(stdcall(_RtlGetCurrentPeb) + PebBitFieldOffset))
   456  	*bitField |= IsLongPathAwareProcess
   457  
   458  	canUseLongPaths = true
   459  }
   460  
   461  func osinit() {
   462  	asmstdcallAddr = unsafe.Pointer(windows.AsmStdCallAddr())
   463  
   464  	loadOptionalSyscalls()
   465  
   466  	preventErrorDialogs()
   467  
   468  	initExceptionHandler()
   469  
   470  	initHighResTimer()
   471  	timeBeginPeriodRetValue = osRelax(false)
   472  
   473  	initSysDirectory()
   474  	initLongPathSupport()
   475  
   476  	numCPUStartup = getCPUCount()
   477  
   478  	physPageSize = getPageSize()
   479  
   480  	// Windows dynamic priority boosting assumes that a process has different types
   481  	// of dedicated threads -- GUI, IO, computational, etc. Go processes use
   482  	// equivalent threads that all do a mix of GUI, IO, computations, etc.
   483  	// In such context dynamic priority boosting does nothing but harm, so we turn it off.
   484  	stdcall(_SetProcessPriorityBoost, windows.CurrentProcess, 1)
   485  }
   486  
   487  //go:nosplit
   488  func readRandom(r []byte) int {
   489  	n := 0
   490  	if stdcall(_ProcessPrng, uintptr(unsafe.Pointer(&r[0])), uintptr(len(r)))&0xff != 0 {
   491  		n = len(r)
   492  	}
   493  	return n
   494  }
   495  
   496  func goenvs() {
   497  	// strings is a pointer to environment variable pairs in the form:
   498  	//     "envA=valA\x00envB=valB\x00\x00" (in UTF-16)
   499  	// Two consecutive zero bytes end the list.
   500  	strings := unsafe.Pointer(stdcall(_GetEnvironmentStringsW))
   501  	p := (*[1 << 24]uint16)(strings)[:]
   502  
   503  	n := 0
   504  	for from, i := 0, 0; true; i++ {
   505  		if p[i] == 0 {
   506  			// empty string marks the end
   507  			if i == from {
   508  				break
   509  			}
   510  			from = i + 1
   511  			n++
   512  		}
   513  	}
   514  	envs = make([]string, n)
   515  
   516  	for i := range envs {
   517  		envs[i] = gostringw(&p[0])
   518  		for p[0] != 0 {
   519  			p = p[1:]
   520  		}
   521  		p = p[1:] // skip nil byte
   522  	}
   523  
   524  	stdcall(_FreeEnvironmentStringsW, uintptr(strings))
   525  
   526  	// We call these all the way here, late in init, so that malloc works
   527  	// for the callback functions these generate.
   528  	var fn any = ctrlHandler
   529  	ctrlHandlerPC := compileCallback(*efaceOf(&fn), true)
   530  	stdcall(_SetConsoleCtrlHandler, ctrlHandlerPC, 1)
   531  
   532  	monitorSuspendResume()
   533  }
   534  
   535  // exiting is set to non-zero when the process is exiting.
   536  var exiting uint32
   537  
   538  //go:nosplit
   539  func exit(code int32) {
   540  	// Disallow thread suspension for preemption. Otherwise,
   541  	// ExitProcess and SuspendThread can race: SuspendThread
   542  	// queues a suspension request for this thread, ExitProcess
   543  	// kills the suspending thread, and then this thread suspends.
   544  	lock(&suspendLock)
   545  	atomic.Store(&exiting, 1)
   546  	stdcall(_ExitProcess, uintptr(code))
   547  }
   548  
   549  // write1 must be nosplit because it's used as a last resort in
   550  // functions like badmorestackg0. In such cases, we'll always take the
   551  // ASCII path.
   552  //
   553  //go:nosplit
   554  func write1(fd uintptr, buf unsafe.Pointer, n int32) int32 {
   555  	const (
   556  		_STD_OUTPUT_HANDLE = ^uintptr(10) // -11
   557  		_STD_ERROR_HANDLE  = ^uintptr(11) // -12
   558  	)
   559  	var handle uintptr
   560  	switch fd {
   561  	case 1:
   562  		handle = stdcall(_GetStdHandle, _STD_OUTPUT_HANDLE)
   563  	case 2:
   564  		handle = stdcall(_GetStdHandle, _STD_ERROR_HANDLE)
   565  	default:
   566  		// assume fd is real windows handle.
   567  		handle = fd
   568  	}
   569  	isASCII := true
   570  	b := (*[1 << 30]byte)(buf)[:n]
   571  	for _, x := range b {
   572  		if x >= 0x80 {
   573  			isASCII = false
   574  			break
   575  		}
   576  	}
   577  
   578  	if !isASCII {
   579  		var m uint32
   580  		isConsole := stdcall(_GetConsoleMode, handle, uintptr(unsafe.Pointer(&m))) != 0
   581  		// If this is a console output, various non-unicode code pages can be in use.
   582  		// Use the dedicated WriteConsole call to ensure unicode is printed correctly.
   583  		if isConsole {
   584  			return int32(writeConsole(handle, buf, n))
   585  		}
   586  	}
   587  	var written uint32
   588  	stdcall(_WriteFile, handle, uintptr(buf), uintptr(n), uintptr(unsafe.Pointer(&written)), 0)
   589  	return int32(written)
   590  }
   591  
   592  var (
   593  	utf16ConsoleBack     [1000]uint16
   594  	utf16ConsoleBackLock mutex
   595  )
   596  
   597  // writeConsole writes bufLen bytes from buf to the console File.
   598  // It returns the number of bytes written.
   599  func writeConsole(handle uintptr, buf unsafe.Pointer, bufLen int32) int {
   600  	const surr2 = (surrogateMin + surrogateMax + 1) / 2
   601  
   602  	// Do not use defer for unlock. May cause issues when printing a panic.
   603  	lock(&utf16ConsoleBackLock)
   604  
   605  	b := (*[1 << 30]byte)(buf)[:bufLen]
   606  	s := *(*string)(unsafe.Pointer(&b))
   607  
   608  	utf16tmp := utf16ConsoleBack[:]
   609  
   610  	total := len(s)
   611  	w := 0
   612  	for _, r := range s {
   613  		if w >= len(utf16tmp)-2 {
   614  			writeConsoleUTF16(handle, utf16tmp[:w])
   615  			w = 0
   616  		}
   617  		if r < 0x10000 {
   618  			utf16tmp[w] = uint16(r)
   619  			w++
   620  		} else {
   621  			r -= 0x10000
   622  			utf16tmp[w] = surrogateMin + uint16(r>>10)&0x3ff
   623  			utf16tmp[w+1] = surr2 + uint16(r)&0x3ff
   624  			w += 2
   625  		}
   626  	}
   627  	writeConsoleUTF16(handle, utf16tmp[:w])
   628  	unlock(&utf16ConsoleBackLock)
   629  	return total
   630  }
   631  
   632  // writeConsoleUTF16 is the dedicated windows calls that correctly prints
   633  // to the console regardless of the current code page. Input is utf-16 code points.
   634  // The handle must be a console handle.
   635  func writeConsoleUTF16(handle uintptr, b []uint16) {
   636  	l := uint32(len(b))
   637  	if l == 0 {
   638  		return
   639  	}
   640  	var written uint32
   641  	stdcall(_WriteConsoleW,
   642  		handle,
   643  		uintptr(unsafe.Pointer(&b[0])),
   644  		uintptr(l),
   645  		uintptr(unsafe.Pointer(&written)),
   646  		0,
   647  	)
   648  	return
   649  }
   650  
   651  //go:nosplit
   652  func semasleep(ns int64) int32 {
   653  	const (
   654  		_WAIT_ABANDONED = 0x00000080
   655  		_WAIT_OBJECT_0  = 0x00000000
   656  		_WAIT_TIMEOUT   = 0x00000102
   657  		_WAIT_FAILED    = 0xFFFFFFFF
   658  	)
   659  
   660  	var result uintptr
   661  	if ns < 0 {
   662  		result = stdcall(_WaitForSingleObject, getg().m.waitsema, uintptr(windows.INFINITE))
   663  	} else {
   664  		start := nanotime()
   665  		elapsed := int64(0)
   666  		for {
   667  			ms := int64(timediv(ns-elapsed, 1000000, nil))
   668  			if ms == 0 {
   669  				ms = 1
   670  			}
   671  			result = stdcall(_WaitForMultipleObjects, 2,
   672  				uintptr(unsafe.Pointer(&[2]uintptr{getg().m.waitsema, getg().m.resumesema})),
   673  				0, uintptr(ms))
   674  			if result != _WAIT_OBJECT_0+1 {
   675  				// Not a suspend/resume event
   676  				break
   677  			}
   678  			elapsed = nanotime() - start
   679  			if elapsed >= ns {
   680  				return -1
   681  			}
   682  		}
   683  	}
   684  	switch result {
   685  	case _WAIT_OBJECT_0: // Signaled
   686  		return 0
   687  
   688  	case _WAIT_TIMEOUT:
   689  		return -1
   690  
   691  	case _WAIT_ABANDONED:
   692  		systemstack(func() {
   693  			throw("runtime.semasleep wait_abandoned")
   694  		})
   695  
   696  	case _WAIT_FAILED:
   697  		systemstack(func() {
   698  			print("runtime: waitforsingleobject wait_failed; errno=", getlasterror(), "\n")
   699  			throw("runtime.semasleep wait_failed")
   700  		})
   701  
   702  	default:
   703  		systemstack(func() {
   704  			print("runtime: waitforsingleobject unexpected; result=", result, "\n")
   705  			throw("runtime.semasleep unexpected")
   706  		})
   707  	}
   708  
   709  	return -1 // unreachable
   710  }
   711  
   712  //go:nosplit
   713  func semawakeup(mp *m) {
   714  	if stdcall(_SetEvent, mp.waitsema) == 0 {
   715  		systemstack(func() {
   716  			print("runtime: setevent failed; errno=", getlasterror(), "\n")
   717  			throw("runtime.semawakeup")
   718  		})
   719  	}
   720  }
   721  
   722  //go:nosplit
   723  func semacreate(mp *m) {
   724  	if mp.waitsema != 0 {
   725  		return
   726  	}
   727  	mp.waitsema = stdcall(_CreateEventA, 0, 0, 0, 0)
   728  	if mp.waitsema == 0 {
   729  		systemstack(func() {
   730  			print("runtime: createevent failed; errno=", getlasterror(), "\n")
   731  			throw("runtime.semacreate")
   732  		})
   733  	}
   734  	mp.resumesema = stdcall(_CreateEventA, 0, 0, 0, 0)
   735  	if mp.resumesema == 0 {
   736  		systemstack(func() {
   737  			print("runtime: createevent failed; errno=", getlasterror(), "\n")
   738  			throw("runtime.semacreate")
   739  		})
   740  		stdcall(_CloseHandle, mp.waitsema)
   741  		mp.waitsema = 0
   742  	}
   743  }
   744  
   745  // May run with m.p==nil, so write barriers are not allowed. This
   746  // function is called by newosproc0, so it is also required to
   747  // operate without stack guards.
   748  //
   749  //go:nowritebarrierrec
   750  //go:nosplit
   751  func newosproc(mp *m) {
   752  	// We pass 0 for the stack size to use the default for this binary.
   753  	thandle := stdcall(_CreateThread, 0, 0,
   754  		abi.FuncPCABI0(tstart_stdcall), uintptr(unsafe.Pointer(mp)),
   755  		0, 0)
   756  
   757  	if thandle == 0 {
   758  		if atomic.Load(&exiting) != 0 {
   759  			// CreateThread may fail if called
   760  			// concurrently with ExitProcess. If this
   761  			// happens, just freeze this thread and let
   762  			// the process exit. See issue #18253.
   763  			lock(&deadlock)
   764  			lock(&deadlock)
   765  		}
   766  		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", getlasterror(), ")\n")
   767  		throw("runtime.newosproc")
   768  	}
   769  
   770  	// Close thandle to avoid leaking the thread object if it exits.
   771  	stdcall(_CloseHandle, thandle)
   772  }
   773  
   774  // Used by the C library build mode. On Linux this function would allocate a
   775  // stack, but that's not necessary for Windows. No stack guards are present
   776  // and the GC has not been initialized, so write barriers will fail.
   777  //
   778  //go:nowritebarrierrec
   779  //go:nosplit
   780  func newosproc0(stacksize uintptr, fn uintptr) {
   781  	throw("bad newosproc0")
   782  }
   783  
   784  //go:nosplit
   785  //go:nowritebarrierrec
   786  func libpreinit() {}
   787  
   788  func exitThread(wait *atomic.Uint32) {
   789  	// We should never reach exitThread on Windows because we let
   790  	// the OS clean up threads.
   791  	throw("exitThread")
   792  }
   793  
   794  // Called to initialize a new m (including the bootstrap m).
   795  // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
   796  func mpreinit(mp *m) {
   797  }
   798  
   799  //go:nosplit
   800  func sigsave(p *sigset) {
   801  }
   802  
   803  //go:nosplit
   804  func msigrestore(sigmask sigset) {
   805  }
   806  
   807  //go:nosplit
   808  //go:nowritebarrierrec
   809  func clearSignalHandlers() {
   810  }
   811  
   812  //go:nosplit
   813  func sigblock(exiting bool) {
   814  }
   815  
   816  // Called to initialize a new m (including the bootstrap m).
   817  // Called on the new thread, cannot allocate Go memory.
   818  func minit() {
   819  	var thandle uintptr
   820  	if stdcall(_DuplicateHandle, windows.CurrentProcess, windows.CurrentThread, windows.CurrentProcess, uintptr(unsafe.Pointer(&thandle)), 0, 0, windows.DUPLICATE_SAME_ACCESS) == 0 {
   821  		print("runtime.minit: duplicatehandle failed; errno=", getlasterror(), "\n")
   822  		throw("runtime.minit: duplicatehandle failed")
   823  	}
   824  
   825  	mp := getg().m
   826  	lock(&mp.threadLock)
   827  	mp.thread = thandle
   828  	mp.procid = uint64(stdcall(_GetCurrentThreadId))
   829  
   830  	// Configure usleep timer, if possible.
   831  	if mp.highResTimer == 0 && haveHighResTimer {
   832  		mp.highResTimer = createHighResTimer()
   833  		if mp.highResTimer == 0 {
   834  			print("runtime: CreateWaitableTimerEx failed; errno=", getlasterror(), "\n")
   835  			throw("CreateWaitableTimerEx when creating timer failed")
   836  		}
   837  	}
   838  	if mp.waitIocpHandle == 0 && haveHighResSleep {
   839  		mp.waitIocpTimer = createHighResTimer()
   840  		if mp.waitIocpTimer == 0 {
   841  			print("runtime: CreateWaitableTimerEx failed; errno=", getlasterror(), "\n")
   842  			throw("CreateWaitableTimerEx when creating timer failed")
   843  		}
   844  		const GENERIC_ALL = 0x10000000
   845  		errno := stdcall(_NtCreateWaitCompletionPacket, uintptr(unsafe.Pointer(&mp.waitIocpHandle)), GENERIC_ALL, 0)
   846  		if mp.waitIocpHandle == 0 {
   847  			print("runtime: NtCreateWaitCompletionPacket failed; errno=", errno, "\n")
   848  			throw("NtCreateWaitCompletionPacket failed")
   849  		}
   850  	}
   851  	unlock(&mp.threadLock)
   852  
   853  	// Query the true stack base from the OS. Currently we're
   854  	// running on a small assumed stack.
   855  	var mbi windows.MemoryBasicInformation
   856  	res := stdcall(_VirtualQuery, uintptr(unsafe.Pointer(&mbi)), uintptr(unsafe.Pointer(&mbi)), unsafe.Sizeof(mbi))
   857  	if res == 0 {
   858  		print("runtime: VirtualQuery failed; errno=", getlasterror(), "\n")
   859  		throw("VirtualQuery for stack base failed")
   860  	}
   861  	// The system leaves an 8K PAGE_GUARD region at the bottom of
   862  	// the stack (in theory VirtualQuery isn't supposed to include
   863  	// that, but it does). Add an additional 8K of slop for
   864  	// calling C functions that don't have stack checks and for
   865  	// lastcontinuehandler. We shouldn't be anywhere near this
   866  	// bound anyway.
   867  	base := mbi.AllocationBase + 16<<10
   868  	// Sanity check the stack bounds.
   869  	g0 := getg()
   870  	if base > g0.stack.hi || g0.stack.hi-base > 64<<20 {
   871  		print("runtime: g0 stack [", hex(base), ",", hex(g0.stack.hi), ")\n")
   872  		throw("bad g0 stack")
   873  	}
   874  	g0.stack.lo = base
   875  	g0.stackguard0 = g0.stack.lo + stackGuard
   876  	g0.stackguard1 = g0.stackguard0
   877  	// Sanity check the SP.
   878  	stackcheck()
   879  }
   880  
   881  // Called from dropm to undo the effect of an minit.
   882  //
   883  //go:nosplit
   884  func unminit() {
   885  	mp := getg().m
   886  	lock(&mp.threadLock)
   887  	if mp.thread != 0 {
   888  		stdcall(_CloseHandle, mp.thread)
   889  		mp.thread = 0
   890  	}
   891  	unlock(&mp.threadLock)
   892  
   893  	mp.procid = 0
   894  }
   895  
   896  // Called from mexit, but not from dropm, to undo the effect of thread-owned
   897  // resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
   898  //
   899  // This always runs without a P, so //go:nowritebarrierrec is required.
   900  //
   901  //go:nowritebarrierrec
   902  //go:nosplit
   903  func mdestroy(mp *m) {
   904  	if mp.highResTimer != 0 {
   905  		stdcall(_CloseHandle, mp.highResTimer)
   906  		mp.highResTimer = 0
   907  	}
   908  	if mp.waitIocpTimer != 0 {
   909  		stdcall(_CloseHandle, mp.waitIocpTimer)
   910  		mp.waitIocpTimer = 0
   911  	}
   912  	if mp.waitIocpHandle != 0 {
   913  		stdcall(_CloseHandle, mp.waitIocpHandle)
   914  		mp.waitIocpHandle = 0
   915  	}
   916  	if mp.waitsema != 0 {
   917  		stdcall(_CloseHandle, mp.waitsema)
   918  		mp.waitsema = 0
   919  	}
   920  	if mp.resumesema != 0 {
   921  		stdcall(_CloseHandle, mp.resumesema)
   922  		mp.resumesema = 0
   923  	}
   924  }
   925  
   926  // stdcall_no_g is like [stdcall] but can be called without a G.
   927  //
   928  //go:nowritebarrier
   929  //go:nosplit
   930  //go:uintptrkeepalive
   931  func stdcall_no_g(fn stdFunction, args ...uintptr) uintptr {
   932  	call := windows.StdCallInfo{
   933  		Fn: uintptr(unsafe.Pointer(fn)),
   934  		N:  uintptr(len(args)),
   935  	}
   936  	if len(args) > 0 {
   937  		call.Args = uintptr(abi.NoEscape(unsafe.Pointer(&args[0])))
   938  	}
   939  	windows.StdCall(&call)
   940  	return call.R1
   941  }
   942  
   943  // stdcall calls fn with the given arguments using the stdcall calling convention.
   944  // Must be called from the system stack.
   945  // May run during STW, so write barriers are not allowed.
   946  //
   947  //go:nowritebarrier
   948  //go:nosplit
   949  //go:uintptrkeepalive
   950  func stdcall(fn stdFunction, args ...uintptr) uintptr {
   951  	gp := getg()
   952  	mp := gp.m
   953  	mp.stdCallInfo.Fn = uintptr(unsafe.Pointer(fn))
   954  	mp.stdCallInfo.N = uintptr(len(args))
   955  	if len(args) > 0 {
   956  		mp.stdCallInfo.Args = uintptr(abi.NoEscape(unsafe.Pointer(&args[0])))
   957  	}
   958  	resetLibcall := false
   959  	if mp.profilehz != 0 && mp.libcallsp == 0 {
   960  		// leave pc/sp for cpu profiler
   961  		mp.libcallg.set(gp)
   962  		mp.libcallpc = sys.GetCallerPC()
   963  		// sp must be the last, because once async cpu profiler finds
   964  		// all three values to be non-zero, it will use them
   965  		mp.libcallsp = sys.GetCallerSP()
   966  		resetLibcall = true // See comment in sys_darwin.go:libcCall
   967  	}
   968  	asmcgocall(asmstdcallAddr, unsafe.Pointer(&mp.stdCallInfo))
   969  	if resetLibcall {
   970  		mp.libcallsp = 0
   971  	}
   972  	return mp.stdCallInfo.R1
   973  }
   974  
   975  // These must run on the system stack only.
   976  
   977  //go:nosplit
   978  func osyield_no_g() {
   979  	stdcall_no_g(_SwitchToThread)
   980  }
   981  
   982  //go:nosplit
   983  func osyield() {
   984  	systemstack(func() {
   985  		stdcall(_SwitchToThread)
   986  	})
   987  }
   988  
   989  //go:nosplit
   990  func usleep_no_g(us uint32) {
   991  	timeout := uintptr(us) / 1000 // ms units
   992  	stdcall_no_g(_WaitForSingleObject, windows.INVALID_HANDLE_VALUE, timeout)
   993  }
   994  
   995  //go:nosplit
   996  func usleep(us uint32) {
   997  	systemstack(func() {
   998  		var h, timeout uintptr
   999  		// If the high-res timer is available and its handle has been allocated for this m, use it.
  1000  		// Otherwise fall back to the low-res one, which doesn't need a handle.
  1001  		if haveHighResTimer && getg().m.highResTimer != 0 {
  1002  			h = getg().m.highResTimer
  1003  			dt := -10 * int64(us) // relative sleep (negative), 100ns units
  1004  			stdcall(_SetWaitableTimer, h, uintptr(unsafe.Pointer(&dt)), 0, 0, 0, 0)
  1005  			timeout = windows.INFINITE
  1006  		} else {
  1007  			h = windows.INVALID_HANDLE_VALUE
  1008  			timeout = uintptr(us) / 1000 // ms units
  1009  		}
  1010  		stdcall(_WaitForSingleObject, h, timeout)
  1011  	})
  1012  }
  1013  
  1014  func ctrlHandler(_type uint32) uintptr {
  1015  	var s uint32
  1016  
  1017  	switch _type {
  1018  	case windows.CTRL_C_EVENT, windows.CTRL_BREAK_EVENT:
  1019  		s = windows.SIGINT
  1020  	case windows.CTRL_CLOSE_EVENT, windows.CTRL_LOGOFF_EVENT, windows.CTRL_SHUTDOWN_EVENT:
  1021  		s = windows.SIGTERM
  1022  	default:
  1023  		return 0
  1024  	}
  1025  
  1026  	if sigsend(s) {
  1027  		if s == windows.SIGTERM {
  1028  			// Windows terminates the process after this handler returns.
  1029  			// Block indefinitely to give signal handlers a chance to clean up,
  1030  			// but make sure to be properly parked first, so the rest of the
  1031  			// program can continue executing.
  1032  			block()
  1033  		}
  1034  		return 1
  1035  	}
  1036  	return 0
  1037  }
  1038  
  1039  // called from zcallback_windows_*.s to sys_windows_*.s
  1040  func callbackasm1()
  1041  
  1042  var profiletimer uintptr
  1043  
  1044  func profilem(mp *m, thread uintptr) {
  1045  	// Align Context to 16 bytes.
  1046  	var c *windows.Context
  1047  	var cbuf [unsafe.Sizeof(*c) + 15]byte
  1048  	c = (*windows.Context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
  1049  
  1050  	c.ContextFlags = windows.CONTEXT_CONTROL
  1051  	stdcall(_GetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1052  
  1053  	gp := gFromSP(mp, c.SP())
  1054  
  1055  	sigprof(c.PC(), c.SP(), c.LR(), gp, mp)
  1056  }
  1057  
  1058  func gFromSP(mp *m, sp uintptr) *g {
  1059  	if gp := mp.g0; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1060  		return gp
  1061  	}
  1062  	if gp := mp.gsignal; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1063  		return gp
  1064  	}
  1065  	if gp := mp.curg; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1066  		return gp
  1067  	}
  1068  	return nil
  1069  }
  1070  
  1071  func profileLoop() {
  1072  	stdcall(_SetThreadPriority, windows.CurrentThread, windows.THREAD_PRIORITY_HIGHEST)
  1073  
  1074  	for {
  1075  		stdcall(_WaitForSingleObject, profiletimer, windows.INFINITE)
  1076  		first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
  1077  		for mp := first; mp != nil; mp = mp.alllink {
  1078  			if mp == getg().m {
  1079  				// Don't profile ourselves.
  1080  				continue
  1081  			}
  1082  
  1083  			lock(&mp.threadLock)
  1084  			// Do not profile threads blocked on Notes,
  1085  			// this includes idle worker threads,
  1086  			// idle timer thread, idle heap scavenger, etc.
  1087  			if mp.thread == 0 || mp.profilehz == 0 || mp.blocked {
  1088  				unlock(&mp.threadLock)
  1089  				continue
  1090  			}
  1091  			// Acquire our own handle to the thread.
  1092  			var thread uintptr
  1093  			if stdcall(_DuplicateHandle, windows.CurrentProcess, mp.thread, windows.CurrentProcess, uintptr(unsafe.Pointer(&thread)), 0, 0, windows.DUPLICATE_SAME_ACCESS) == 0 {
  1094  				print("runtime: duplicatehandle failed; errno=", getlasterror(), "\n")
  1095  				throw("duplicatehandle failed")
  1096  			}
  1097  			unlock(&mp.threadLock)
  1098  
  1099  			// mp may exit between the DuplicateHandle
  1100  			// above and the SuspendThread. The handle
  1101  			// will remain valid, but SuspendThread may
  1102  			// fail.
  1103  			if int32(stdcall(_SuspendThread, thread)) == -1 {
  1104  				// The thread no longer exists.
  1105  				stdcall(_CloseHandle, thread)
  1106  				continue
  1107  			}
  1108  			if mp.profilehz != 0 && !mp.blocked {
  1109  				// Pass the thread handle in case mp
  1110  				// was in the process of shutting down.
  1111  				profilem(mp, thread)
  1112  			}
  1113  			stdcall(_ResumeThread, thread)
  1114  			stdcall(_CloseHandle, thread)
  1115  		}
  1116  	}
  1117  }
  1118  
  1119  func setProcessCPUProfiler(hz int32) {
  1120  	if profiletimer == 0 {
  1121  		var timer uintptr
  1122  		if haveHighResTimer {
  1123  			timer = createHighResTimer()
  1124  		} else {
  1125  			timer = stdcall(_CreateWaitableTimerA, 0, 0, 0)
  1126  		}
  1127  		atomic.Storeuintptr(&profiletimer, timer)
  1128  		newm(profileLoop, nil, -1)
  1129  	}
  1130  }
  1131  
  1132  func setThreadCPUProfiler(hz int32) {
  1133  	ms := int32(0)
  1134  	due := ^int64(^uint64(1 << 63))
  1135  	if hz > 0 {
  1136  		ms = 1000 / hz
  1137  		if ms == 0 {
  1138  			ms = 1
  1139  		}
  1140  		due = int64(ms) * -10000
  1141  	}
  1142  	stdcall(_SetWaitableTimer, profiletimer, uintptr(unsafe.Pointer(&due)), uintptr(ms), 0, 0, 0)
  1143  	atomic.Store((*uint32)(unsafe.Pointer(&getg().m.profilehz)), uint32(hz))
  1144  }
  1145  
  1146  const preemptMSupported = true
  1147  
  1148  // suspendLock protects simultaneous SuspendThread operations from
  1149  // suspending each other.
  1150  var suspendLock mutex
  1151  
  1152  func preemptM(mp *m) {
  1153  	if mp == getg().m {
  1154  		throw("self-preempt")
  1155  	}
  1156  
  1157  	// Synchronize with external code that may try to ExitProcess.
  1158  	if !atomic.Cas(&mp.preemptExtLock, 0, 1) {
  1159  		// External code is running. Fail the preemption
  1160  		// attempt.
  1161  		mp.preemptGen.Add(1)
  1162  		return
  1163  	}
  1164  
  1165  	// Acquire our own handle to mp's thread.
  1166  	lock(&mp.threadLock)
  1167  	if mp.thread == 0 {
  1168  		// The M hasn't been minit'd yet (or was just unminit'd).
  1169  		unlock(&mp.threadLock)
  1170  		atomic.Store(&mp.preemptExtLock, 0)
  1171  		mp.preemptGen.Add(1)
  1172  		return
  1173  	}
  1174  	var thread uintptr
  1175  	if stdcall(_DuplicateHandle, windows.CurrentProcess, mp.thread, windows.CurrentProcess, uintptr(unsafe.Pointer(&thread)), 0, 0, windows.DUPLICATE_SAME_ACCESS) == 0 {
  1176  		print("runtime.preemptM: duplicatehandle failed; errno=", getlasterror(), "\n")
  1177  		throw("runtime.preemptM: duplicatehandle failed")
  1178  	}
  1179  	unlock(&mp.threadLock)
  1180  
  1181  	// Prepare thread context buffer. This must be aligned to 16 bytes.
  1182  	var c *windows.Context
  1183  	var cbuf [unsafe.Sizeof(*c) + 15]byte
  1184  	c = (*windows.Context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
  1185  	c.ContextFlags = windows.CONTEXT_CONTROL
  1186  
  1187  	// Serialize thread suspension. SuspendThread is asynchronous,
  1188  	// so it's otherwise possible for two threads to suspend each
  1189  	// other and deadlock. We must hold this lock until after
  1190  	// GetThreadContext, since that blocks until the thread is
  1191  	// actually suspended.
  1192  	lock(&suspendLock)
  1193  
  1194  	// Suspend the thread.
  1195  	if int32(stdcall(_SuspendThread, thread)) == -1 {
  1196  		unlock(&suspendLock)
  1197  		stdcall(_CloseHandle, thread)
  1198  		atomic.Store(&mp.preemptExtLock, 0)
  1199  		// The thread no longer exists. This shouldn't be
  1200  		// possible, but just acknowledge the request.
  1201  		mp.preemptGen.Add(1)
  1202  		return
  1203  	}
  1204  
  1205  	// We have to be very careful between this point and once
  1206  	// we've shown mp is at an async safe-point. This is like a
  1207  	// signal handler in the sense that mp could have been doing
  1208  	// anything when we stopped it, including holding arbitrary
  1209  	// locks.
  1210  
  1211  	// We have to get the thread context before inspecting the M
  1212  	// because SuspendThread only requests a suspend.
  1213  	// GetThreadContext actually blocks until it's suspended.
  1214  	stdcall(_GetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1215  
  1216  	unlock(&suspendLock)
  1217  
  1218  	// Does it want a preemption and is it safe to preempt?
  1219  	gp := gFromSP(mp, c.SP())
  1220  	if gp != nil && wantAsyncPreempt(gp) {
  1221  		if ok, resumePC := isAsyncSafePoint(gp, c.PC(), c.SP(), c.LR()); ok {
  1222  			// Inject call to asyncPreempt
  1223  			targetPC := abi.FuncPCABI0(asyncPreempt)
  1224  			c.PushCall(targetPC, resumePC)
  1225  			stdcall(_SetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1226  		}
  1227  	}
  1228  
  1229  	atomic.Store(&mp.preemptExtLock, 0)
  1230  
  1231  	// Acknowledge the preemption.
  1232  	mp.preemptGen.Add(1)
  1233  
  1234  	stdcall(_ResumeThread, thread)
  1235  	stdcall(_CloseHandle, thread)
  1236  }
  1237  
  1238  // osPreemptExtEnter is called before entering external code that may
  1239  // call ExitProcess.
  1240  //
  1241  // This must be nosplit because it may be called from a syscall with
  1242  // untyped stack slots, so the stack must not be grown or scanned.
  1243  //
  1244  //go:nosplit
  1245  func osPreemptExtEnter(mp *m) {
  1246  	for !atomic.Cas(&mp.preemptExtLock, 0, 1) {
  1247  		// An asynchronous preemption is in progress. It's not
  1248  		// safe to enter external code because it may call
  1249  		// ExitProcess and deadlock with SuspendThread.
  1250  		// Ideally we would do the preemption ourselves, but
  1251  		// can't since there may be untyped syscall arguments
  1252  		// on the stack. Instead, just wait and encourage the
  1253  		// SuspendThread APC to run. The preemption should be
  1254  		// done shortly.
  1255  		osyield()
  1256  	}
  1257  	// Asynchronous preemption is now blocked.
  1258  }
  1259  
  1260  // osPreemptExtExit is called after returning from external code that
  1261  // may call ExitProcess.
  1262  //
  1263  // See osPreemptExtEnter for why this is nosplit.
  1264  //
  1265  //go:nosplit
  1266  func osPreemptExtExit(mp *m) {
  1267  	atomic.Store(&mp.preemptExtLock, 0)
  1268  }
  1269  

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