Source file src/runtime/os_windows.go

Documentation: runtime

     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/goarch"
    10  	"runtime/internal/atomic"
    11  	"unsafe"
    12  )
    13  
    14  // TODO(brainman): should not need those
    15  const (
    16  	_NSIG = 65
    17  )
    18  
    19  //go:cgo_import_dynamic runtime._AddVectoredContinueHandler AddVectoredContinueHandler%2 "kernel32.dll"
    20  //go:cgo_import_dynamic runtime._AddVectoredExceptionHandler AddVectoredExceptionHandler%2 "kernel32.dll"
    21  //go:cgo_import_dynamic runtime._CloseHandle CloseHandle%1 "kernel32.dll"
    22  //go:cgo_import_dynamic runtime._CreateEventA CreateEventA%4 "kernel32.dll"
    23  //go:cgo_import_dynamic runtime._CreateFileA CreateFileA%7 "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._LoadLibraryW LoadLibraryW%1 "kernel32.dll"
    45  //go:cgo_import_dynamic runtime._PostQueuedCompletionStatus PostQueuedCompletionStatus%4 "kernel32.dll"
    46  //go:cgo_import_dynamic runtime._QueryPerformanceCounter QueryPerformanceCounter%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  	_CreateFileA,
    82  	_CreateIoCompletionPort,
    83  	_CreateThread,
    84  	_CreateWaitableTimerA,
    85  	_CreateWaitableTimerExW,
    86  	_DuplicateHandle,
    87  	_ExitProcess,
    88  	_FreeEnvironmentStringsW,
    89  	_GetConsoleMode,
    90  	_GetCurrentThreadId,
    91  	_GetEnvironmentStringsW,
    92  	_GetErrorMode,
    93  	_GetProcAddress,
    94  	_GetProcessAffinityMask,
    95  	_GetQueuedCompletionStatusEx,
    96  	_GetStdHandle,
    97  	_GetSystemDirectoryA,
    98  	_GetSystemInfo,
    99  	_GetThreadContext,
   100  	_SetThreadContext,
   101  	_LoadLibraryExW,
   102  	_LoadLibraryW,
   103  	_PostQueuedCompletionStatus,
   104  	_QueryPerformanceCounter,
   105  	_RaiseFailFastException,
   106  	_ResumeThread,
   107  	_RtlLookupFunctionEntry,
   108  	_RtlVirtualUnwind,
   109  	_SetConsoleCtrlHandler,
   110  	_SetErrorMode,
   111  	_SetEvent,
   112  	_SetProcessPriorityBoost,
   113  	_SetThreadPriority,
   114  	_SetUnhandledExceptionFilter,
   115  	_SetWaitableTimer,
   116  	_SuspendThread,
   117  	_SwitchToThread,
   118  	_TlsAlloc,
   119  	_VirtualAlloc,
   120  	_VirtualFree,
   121  	_VirtualQuery,
   122  	_WaitForSingleObject,
   123  	_WaitForMultipleObjects,
   124  	_WerGetFlags,
   125  	_WerSetFlags,
   126  	_WriteConsoleW,
   127  	_WriteFile,
   128  	_ stdFunction
   129  
   130  	// Use ProcessPrng to generate cryptographically random data.
   131  	_ProcessPrng stdFunction
   132  
   133  	// Load ntdll.dll manually during startup, otherwise Mingw
   134  	// links wrong printf function to cgo executable (see issue
   135  	// 12030 for details).
   136  	_RtlGetCurrentPeb       stdFunction
   137  	_RtlGetNtVersionNumbers stdFunction
   138  
   139  	// These are from non-kernel32.dll, so we prefer to LoadLibraryEx them.
   140  	_timeBeginPeriod,
   141  	_timeEndPeriod,
   142  	_WSAGetOverlappedResult,
   143  	_ stdFunction
   144  )
   145  
   146  var (
   147  	bcryptprimitivesdll = [...]uint16{'b', 'c', 'r', 'y', 'p', 't', 'p', 'r', 'i', 'm', 'i', 't', 'i', 'v', 'e', 's', '.', 'd', 'l', 'l', 0}
   148  	ntdlldll            = [...]uint16{'n', 't', 'd', 'l', 'l', '.', 'd', 'l', 'l', 0}
   149  	powrprofdll         = [...]uint16{'p', 'o', 'w', 'r', 'p', 'r', 'o', 'f', '.', 'd', 'l', 'l', 0}
   150  	winmmdll            = [...]uint16{'w', 'i', 'n', 'm', 'm', '.', 'd', 'l', 'l', 0}
   151  	ws2_32dll           = [...]uint16{'w', 's', '2', '_', '3', '2', '.', '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  	threadLock mutex   // protects "thread" and prevents closing
   163  	thread     uintptr // thread handle
   164  
   165  	waitsema   uintptr // semaphore for parking on locks
   166  	resumesema uintptr // semaphore to indicate suspend/resume
   167  
   168  	highResTimer uintptr // high resolution timer handle used in usleep
   169  
   170  	// preemptExtLock synchronizes preemptM with entry/exit from
   171  	// external C code.
   172  	//
   173  	// This protects against races between preemptM calling
   174  	// SuspendThread and external code on this thread calling
   175  	// ExitProcess. If these happen concurrently, it's possible to
   176  	// exit the suspending thread and suspend the exiting thread,
   177  	// leading to deadlock.
   178  	//
   179  	// 0 indicates this M is not being preempted or in external
   180  	// code. Entering external code CASes this from 0 to 1. If
   181  	// this fails, a preemption is in progress, so the thread must
   182  	// wait for the preemption. preemptM also CASes this from 0 to
   183  	// 1. If this fails, the preemption fails (as it would if the
   184  	// PC weren't in Go code). The value is reset to 0 when
   185  	// returning from external code or after a preemption is
   186  	// complete.
   187  	//
   188  	// TODO(austin): We may not need this if preemption were more
   189  	// tightly synchronized on the G/P status and preemption
   190  	// blocked transition into _Gsyscall/_Psyscall.
   191  	preemptExtLock uint32
   192  }
   193  
   194  // Stubs so tests can link correctly. These should never be called.
   195  func open(name *byte, mode, perm int32) int32 {
   196  	throw("unimplemented")
   197  	return -1
   198  }
   199  func closefd(fd int32) int32 {
   200  	throw("unimplemented")
   201  	return -1
   202  }
   203  func read(fd int32, p unsafe.Pointer, n int32) int32 {
   204  	throw("unimplemented")
   205  	return -1
   206  }
   207  
   208  type sigset struct{}
   209  
   210  // Call a Windows function with stdcall conventions,
   211  // and switch to os stack during the call.
   212  func asmstdcall(fn unsafe.Pointer)
   213  
   214  var asmstdcallAddr unsafe.Pointer
   215  
   216  func windowsFindfunc(lib uintptr, name []byte) stdFunction {
   217  	if name[len(name)-1] != 0 {
   218  		throw("usage")
   219  	}
   220  	f := stdcall2(_GetProcAddress, lib, uintptr(unsafe.Pointer(&name[0])))
   221  	return stdFunction(unsafe.Pointer(f))
   222  }
   223  
   224  const _MAX_PATH = 260 // https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
   225  var sysDirectory [_MAX_PATH + 1]byte
   226  var sysDirectoryLen uintptr
   227  
   228  func initSysDirectory() {
   229  	l := stdcall2(_GetSystemDirectoryA, uintptr(unsafe.Pointer(&sysDirectory[0])), uintptr(len(sysDirectory)-1))
   230  	if l == 0 || l > uintptr(len(sysDirectory)-1) {
   231  		throw("Unable to determine system directory")
   232  	}
   233  	sysDirectory[l] = '\\'
   234  	sysDirectoryLen = l + 1
   235  }
   236  
   237  //go:linkname windows_GetSystemDirectory internal/syscall/windows.GetSystemDirectory
   238  func windows_GetSystemDirectory() string {
   239  	return unsafe.String(&sysDirectory[0], sysDirectoryLen)
   240  }
   241  
   242  func windowsLoadSystemLib(name []uint16) uintptr {
   243  	return stdcall3(_LoadLibraryExW, uintptr(unsafe.Pointer(&name[0])), 0, _LOAD_LIBRARY_SEARCH_SYSTEM32)
   244  }
   245  
   246  func loadOptionalSyscalls() {
   247  	bcryptPrimitives := windowsLoadSystemLib(bcryptprimitivesdll[:])
   248  	if bcryptPrimitives == 0 {
   249  		throw("bcryptprimitives.dll not found")
   250  	}
   251  	_ProcessPrng = windowsFindfunc(bcryptPrimitives, []byte("ProcessPrng\000"))
   252  
   253  	n32 := windowsLoadSystemLib(ntdlldll[:])
   254  	if n32 == 0 {
   255  		throw("ntdll.dll not found")
   256  	}
   257  	_RtlGetCurrentPeb = windowsFindfunc(n32, []byte("RtlGetCurrentPeb\000"))
   258  	_RtlGetNtVersionNumbers = windowsFindfunc(n32, []byte("RtlGetNtVersionNumbers\000"))
   259  
   260  	m32 := windowsLoadSystemLib(winmmdll[:])
   261  	if m32 == 0 {
   262  		throw("winmm.dll not found")
   263  	}
   264  	_timeBeginPeriod = windowsFindfunc(m32, []byte("timeBeginPeriod\000"))
   265  	_timeEndPeriod = windowsFindfunc(m32, []byte("timeEndPeriod\000"))
   266  	if _timeBeginPeriod == nil || _timeEndPeriod == nil {
   267  		throw("timeBegin/EndPeriod not found")
   268  	}
   269  
   270  	ws232 := windowsLoadSystemLib(ws2_32dll[:])
   271  	if ws232 == 0 {
   272  		throw("ws2_32.dll not found")
   273  	}
   274  	_WSAGetOverlappedResult = windowsFindfunc(ws232, []byte("WSAGetOverlappedResult\000"))
   275  	if _WSAGetOverlappedResult == nil {
   276  		throw("WSAGetOverlappedResult not found")
   277  	}
   278  }
   279  
   280  func monitorSuspendResume() {
   281  	const (
   282  		_DEVICE_NOTIFY_CALLBACK = 2
   283  	)
   284  	type _DEVICE_NOTIFY_SUBSCRIBE_PARAMETERS struct {
   285  		callback uintptr
   286  		context  uintptr
   287  	}
   288  
   289  	powrprof := windowsLoadSystemLib(powrprofdll[:])
   290  	if powrprof == 0 {
   291  		return // Running on Windows 7, where we don't need it anyway.
   292  	}
   293  	powerRegisterSuspendResumeNotification := windowsFindfunc(powrprof, []byte("PowerRegisterSuspendResumeNotification\000"))
   294  	if powerRegisterSuspendResumeNotification == nil {
   295  		return // Running on Windows 7, where we don't need it anyway.
   296  	}
   297  	var fn any = func(context uintptr, changeType uint32, setting uintptr) uintptr {
   298  		for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
   299  			if mp.resumesema != 0 {
   300  				stdcall1(_SetEvent, mp.resumesema)
   301  			}
   302  		}
   303  		return 0
   304  	}
   305  	params := _DEVICE_NOTIFY_SUBSCRIBE_PARAMETERS{
   306  		callback: compileCallback(*efaceOf(&fn), true),
   307  	}
   308  	handle := uintptr(0)
   309  	stdcall3(powerRegisterSuspendResumeNotification, _DEVICE_NOTIFY_CALLBACK,
   310  		uintptr(unsafe.Pointer(&params)), uintptr(unsafe.Pointer(&handle)))
   311  }
   312  
   313  //go:nosplit
   314  func getLoadLibrary() uintptr {
   315  	return uintptr(unsafe.Pointer(_LoadLibraryW))
   316  }
   317  
   318  //go:nosplit
   319  func getLoadLibraryEx() uintptr {
   320  	return uintptr(unsafe.Pointer(_LoadLibraryExW))
   321  }
   322  
   323  //go:nosplit
   324  func getGetProcAddress() uintptr {
   325  	return uintptr(unsafe.Pointer(_GetProcAddress))
   326  }
   327  
   328  func getproccount() int32 {
   329  	var mask, sysmask uintptr
   330  	ret := stdcall3(_GetProcessAffinityMask, currentProcess, uintptr(unsafe.Pointer(&mask)), uintptr(unsafe.Pointer(&sysmask)))
   331  	if ret != 0 {
   332  		n := 0
   333  		maskbits := int(unsafe.Sizeof(mask) * 8)
   334  		for i := 0; i < maskbits; i++ {
   335  			if mask&(1<<uint(i)) != 0 {
   336  				n++
   337  			}
   338  		}
   339  		if n != 0 {
   340  			return int32(n)
   341  		}
   342  	}
   343  	// use GetSystemInfo if GetProcessAffinityMask fails
   344  	var info systeminfo
   345  	stdcall1(_GetSystemInfo, uintptr(unsafe.Pointer(&info)))
   346  	return int32(info.dwnumberofprocessors)
   347  }
   348  
   349  func getPageSize() uintptr {
   350  	var info systeminfo
   351  	stdcall1(_GetSystemInfo, uintptr(unsafe.Pointer(&info)))
   352  	return uintptr(info.dwpagesize)
   353  }
   354  
   355  const (
   356  	currentProcess = ^uintptr(0) // -1 = current process
   357  	currentThread  = ^uintptr(1) // -2 = current thread
   358  )
   359  
   360  // in sys_windows_386.s and sys_windows_amd64.s:
   361  func getlasterror() uint32
   362  
   363  var timeBeginPeriodRetValue uint32
   364  
   365  // osRelaxMinNS indicates that sysmon shouldn't osRelax if the next
   366  // timer is less than 60 ms from now. Since osRelaxing may reduce
   367  // timer resolution to 15.6 ms, this keeps timer error under roughly 1
   368  // part in 4.
   369  const osRelaxMinNS = 60 * 1e6
   370  
   371  // osRelax is called by the scheduler when transitioning to and from
   372  // all Ps being idle.
   373  //
   374  // Some versions of Windows have high resolution timer. For those
   375  // versions osRelax is noop.
   376  // For Windows versions without high resolution timer, osRelax
   377  // adjusts the system-wide timer resolution. Go needs a
   378  // high resolution timer while running and there's little extra cost
   379  // if we're already using the CPU, but if all Ps are idle there's no
   380  // need to consume extra power to drive the high-res timer.
   381  func osRelax(relax bool) uint32 {
   382  	if haveHighResTimer {
   383  		// If the high resolution timer is available, the runtime uses the timer
   384  		// to sleep for short durations. This means there's no need to adjust
   385  		// the global clock frequency.
   386  		return 0
   387  	}
   388  
   389  	if relax {
   390  		return uint32(stdcall1(_timeEndPeriod, 1))
   391  	} else {
   392  		return uint32(stdcall1(_timeBeginPeriod, 1))
   393  	}
   394  }
   395  
   396  // haveHighResTimer indicates that the CreateWaitableTimerEx
   397  // CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag is available.
   398  var haveHighResTimer = false
   399  
   400  // createHighResTimer calls CreateWaitableTimerEx with
   401  // CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag to create high
   402  // resolution timer. createHighResTimer returns new timer
   403  // handle or 0, if CreateWaitableTimerEx failed.
   404  func createHighResTimer() uintptr {
   405  	const (
   406  		// As per @jstarks, see
   407  		// https://github.com/golang/go/issues/8687#issuecomment-656259353
   408  		_CREATE_WAITABLE_TIMER_HIGH_RESOLUTION = 0x00000002
   409  
   410  		_SYNCHRONIZE        = 0x00100000
   411  		_TIMER_QUERY_STATE  = 0x0001
   412  		_TIMER_MODIFY_STATE = 0x0002
   413  	)
   414  	return stdcall4(_CreateWaitableTimerExW, 0, 0,
   415  		_CREATE_WAITABLE_TIMER_HIGH_RESOLUTION,
   416  		_SYNCHRONIZE|_TIMER_QUERY_STATE|_TIMER_MODIFY_STATE)
   417  }
   418  
   419  func initHighResTimer() {
   420  	h := createHighResTimer()
   421  	if h != 0 {
   422  		haveHighResTimer = true
   423  		stdcall1(_CloseHandle, h)
   424  	}
   425  }
   426  
   427  //go:linkname canUseLongPaths os.canUseLongPaths
   428  var canUseLongPaths bool
   429  
   430  // We want this to be large enough to hold the contents of sysDirectory, *plus*
   431  // a slash and another component that itself is greater than MAX_PATH.
   432  var longFileName [(_MAX_PATH+1)*2 + 1]byte
   433  
   434  // initLongPathSupport initializes the canUseLongPaths variable, which is
   435  // linked into os.canUseLongPaths for determining whether or not long paths
   436  // need to be fixed up. In the best case, this function is running on newer
   437  // Windows 10 builds, which have a bit field member of the PEB called
   438  // "IsLongPathAwareProcess." When this is set, we don't need to go through the
   439  // error-prone fixup function in order to access long paths. So this init
   440  // function first checks the Windows build number, sets the flag, and then
   441  // tests to see if it's actually working. If everything checks out, then
   442  // canUseLongPaths is set to true, and later when called, os.fixLongPath
   443  // returns early without doing work.
   444  func initLongPathSupport() {
   445  	const (
   446  		IsLongPathAwareProcess = 0x80
   447  		PebBitFieldOffset      = 3
   448  		OPEN_EXISTING          = 3
   449  		ERROR_PATH_NOT_FOUND   = 3
   450  	)
   451  
   452  	// Check that we're ≥ 10.0.15063.
   453  	var maj, min, build uint32
   454  	stdcall3(_RtlGetNtVersionNumbers, uintptr(unsafe.Pointer(&maj)), uintptr(unsafe.Pointer(&min)), uintptr(unsafe.Pointer(&build)))
   455  	if maj < 10 || (maj == 10 && min == 0 && build&0xffff < 15063) {
   456  		return
   457  	}
   458  
   459  	// Set the IsLongPathAwareProcess flag of the PEB's bit field.
   460  	bitField := (*byte)(unsafe.Pointer(stdcall0(_RtlGetCurrentPeb) + PebBitFieldOffset))
   461  	originalBitField := *bitField
   462  	*bitField |= IsLongPathAwareProcess
   463  
   464  	// Check that this actually has an effect, by constructing a large file
   465  	// path and seeing whether we get ERROR_PATH_NOT_FOUND, rather than
   466  	// some other error, which would indicate the path is too long, and
   467  	// hence long path support is not successful. This whole section is NOT
   468  	// strictly necessary, but is a nice validity check for the near to
   469  	// medium term, when this functionality is still relatively new in
   470  	// Windows.
   471  	targ := longFileName[len(longFileName)-33 : len(longFileName)-1]
   472  	if readRandom(targ) != len(targ) {
   473  		readTimeRandom(targ)
   474  	}
   475  	start := copy(longFileName[:], sysDirectory[:sysDirectoryLen])
   476  	const dig = "0123456789abcdef"
   477  	for i := 0; i < 32; i++ {
   478  		longFileName[start+i*2] = dig[longFileName[len(longFileName)-33+i]>>4]
   479  		longFileName[start+i*2+1] = dig[longFileName[len(longFileName)-33+i]&0xf]
   480  	}
   481  	start += 64
   482  	for i := start; i < len(longFileName)-1; i++ {
   483  		longFileName[i] = 'A'
   484  	}
   485  	stdcall7(_CreateFileA, uintptr(unsafe.Pointer(&longFileName[0])), 0, 0, 0, OPEN_EXISTING, 0, 0)
   486  	// The ERROR_PATH_NOT_FOUND error value is distinct from
   487  	// ERROR_FILE_NOT_FOUND or ERROR_INVALID_NAME, the latter of which we
   488  	// expect here due to the final component being too long.
   489  	if getlasterror() == ERROR_PATH_NOT_FOUND {
   490  		*bitField = originalBitField
   491  		println("runtime: warning: IsLongPathAwareProcess failed to enable long paths; proceeding in fixup mode")
   492  		return
   493  	}
   494  
   495  	canUseLongPaths = true
   496  }
   497  
   498  func osinit() {
   499  	asmstdcallAddr = unsafe.Pointer(abi.FuncPCABI0(asmstdcall))
   500  
   501  	loadOptionalSyscalls()
   502  
   503  	preventErrorDialogs()
   504  
   505  	initExceptionHandler()
   506  
   507  	initHighResTimer()
   508  	timeBeginPeriodRetValue = osRelax(false)
   509  
   510  	initSysDirectory()
   511  	initLongPathSupport()
   512  
   513  	ncpu = getproccount()
   514  
   515  	physPageSize = getPageSize()
   516  
   517  	// Windows dynamic priority boosting assumes that a process has different types
   518  	// of dedicated threads -- GUI, IO, computational, etc. Go processes use
   519  	// equivalent threads that all do a mix of GUI, IO, computations, etc.
   520  	// In such context dynamic priority boosting does nothing but harm, so we turn it off.
   521  	stdcall2(_SetProcessPriorityBoost, currentProcess, 1)
   522  }
   523  
   524  //go:nosplit
   525  func readRandom(r []byte) int {
   526  	n := 0
   527  	if stdcall2(_ProcessPrng, uintptr(unsafe.Pointer(&r[0])), uintptr(len(r)))&0xff != 0 {
   528  		n = len(r)
   529  	}
   530  	return n
   531  }
   532  
   533  func goenvs() {
   534  	// strings is a pointer to environment variable pairs in the form:
   535  	//     "envA=valA\x00envB=valB\x00\x00" (in UTF-16)
   536  	// Two consecutive zero bytes end the list.
   537  	strings := unsafe.Pointer(stdcall0(_GetEnvironmentStringsW))
   538  	p := (*[1 << 24]uint16)(strings)[:]
   539  
   540  	n := 0
   541  	for from, i := 0, 0; true; i++ {
   542  		if p[i] == 0 {
   543  			// empty string marks the end
   544  			if i == from {
   545  				break
   546  			}
   547  			from = i + 1
   548  			n++
   549  		}
   550  	}
   551  	envs = make([]string, n)
   552  
   553  	for i := range envs {
   554  		envs[i] = gostringw(&p[0])
   555  		for p[0] != 0 {
   556  			p = p[1:]
   557  		}
   558  		p = p[1:] // skip nil byte
   559  	}
   560  
   561  	stdcall1(_FreeEnvironmentStringsW, uintptr(strings))
   562  
   563  	// We call these all the way here, late in init, so that malloc works
   564  	// for the callback functions these generate.
   565  	var fn any = ctrlHandler
   566  	ctrlHandlerPC := compileCallback(*efaceOf(&fn), true)
   567  	stdcall2(_SetConsoleCtrlHandler, ctrlHandlerPC, 1)
   568  
   569  	monitorSuspendResume()
   570  }
   571  
   572  // exiting is set to non-zero when the process is exiting.
   573  var exiting uint32
   574  
   575  //go:nosplit
   576  func exit(code int32) {
   577  	// Disallow thread suspension for preemption. Otherwise,
   578  	// ExitProcess and SuspendThread can race: SuspendThread
   579  	// queues a suspension request for this thread, ExitProcess
   580  	// kills the suspending thread, and then this thread suspends.
   581  	lock(&suspendLock)
   582  	atomic.Store(&exiting, 1)
   583  	stdcall1(_ExitProcess, uintptr(code))
   584  }
   585  
   586  // write1 must be nosplit because it's used as a last resort in
   587  // functions like badmorestackg0. In such cases, we'll always take the
   588  // ASCII path.
   589  //
   590  //go:nosplit
   591  func write1(fd uintptr, buf unsafe.Pointer, n int32) int32 {
   592  	const (
   593  		_STD_OUTPUT_HANDLE = ^uintptr(10) // -11
   594  		_STD_ERROR_HANDLE  = ^uintptr(11) // -12
   595  	)
   596  	var handle uintptr
   597  	switch fd {
   598  	case 1:
   599  		handle = stdcall1(_GetStdHandle, _STD_OUTPUT_HANDLE)
   600  	case 2:
   601  		handle = stdcall1(_GetStdHandle, _STD_ERROR_HANDLE)
   602  	default:
   603  		// assume fd is real windows handle.
   604  		handle = fd
   605  	}
   606  	isASCII := true
   607  	b := (*[1 << 30]byte)(buf)[:n]
   608  	for _, x := range b {
   609  		if x >= 0x80 {
   610  			isASCII = false
   611  			break
   612  		}
   613  	}
   614  
   615  	if !isASCII {
   616  		var m uint32
   617  		isConsole := stdcall2(_GetConsoleMode, handle, uintptr(unsafe.Pointer(&m))) != 0
   618  		// If this is a console output, various non-unicode code pages can be in use.
   619  		// Use the dedicated WriteConsole call to ensure unicode is printed correctly.
   620  		if isConsole {
   621  			return int32(writeConsole(handle, buf, n))
   622  		}
   623  	}
   624  	var written uint32
   625  	stdcall5(_WriteFile, handle, uintptr(buf), uintptr(n), uintptr(unsafe.Pointer(&written)), 0)
   626  	return int32(written)
   627  }
   628  
   629  var (
   630  	utf16ConsoleBack     [1000]uint16
   631  	utf16ConsoleBackLock mutex
   632  )
   633  
   634  // writeConsole writes bufLen bytes from buf to the console File.
   635  // It returns the number of bytes written.
   636  func writeConsole(handle uintptr, buf unsafe.Pointer, bufLen int32) int {
   637  	const surr2 = (surrogateMin + surrogateMax + 1) / 2
   638  
   639  	// Do not use defer for unlock. May cause issues when printing a panic.
   640  	lock(&utf16ConsoleBackLock)
   641  
   642  	b := (*[1 << 30]byte)(buf)[:bufLen]
   643  	s := *(*string)(unsafe.Pointer(&b))
   644  
   645  	utf16tmp := utf16ConsoleBack[:]
   646  
   647  	total := len(s)
   648  	w := 0
   649  	for _, r := range s {
   650  		if w >= len(utf16tmp)-2 {
   651  			writeConsoleUTF16(handle, utf16tmp[:w])
   652  			w = 0
   653  		}
   654  		if r < 0x10000 {
   655  			utf16tmp[w] = uint16(r)
   656  			w++
   657  		} else {
   658  			r -= 0x10000
   659  			utf16tmp[w] = surrogateMin + uint16(r>>10)&0x3ff
   660  			utf16tmp[w+1] = surr2 + uint16(r)&0x3ff
   661  			w += 2
   662  		}
   663  	}
   664  	writeConsoleUTF16(handle, utf16tmp[:w])
   665  	unlock(&utf16ConsoleBackLock)
   666  	return total
   667  }
   668  
   669  // writeConsoleUTF16 is the dedicated windows calls that correctly prints
   670  // to the console regardless of the current code page. Input is utf-16 code points.
   671  // The handle must be a console handle.
   672  func writeConsoleUTF16(handle uintptr, b []uint16) {
   673  	l := uint32(len(b))
   674  	if l == 0 {
   675  		return
   676  	}
   677  	var written uint32
   678  	stdcall5(_WriteConsoleW,
   679  		handle,
   680  		uintptr(unsafe.Pointer(&b[0])),
   681  		uintptr(l),
   682  		uintptr(unsafe.Pointer(&written)),
   683  		0,
   684  	)
   685  	return
   686  }
   687  
   688  //go:nosplit
   689  func semasleep(ns int64) int32 {
   690  	const (
   691  		_WAIT_ABANDONED = 0x00000080
   692  		_WAIT_OBJECT_0  = 0x00000000
   693  		_WAIT_TIMEOUT   = 0x00000102
   694  		_WAIT_FAILED    = 0xFFFFFFFF
   695  	)
   696  
   697  	var result uintptr
   698  	if ns < 0 {
   699  		result = stdcall2(_WaitForSingleObject, getg().m.waitsema, uintptr(_INFINITE))
   700  	} else {
   701  		start := nanotime()
   702  		elapsed := int64(0)
   703  		for {
   704  			ms := int64(timediv(ns-elapsed, 1000000, nil))
   705  			if ms == 0 {
   706  				ms = 1
   707  			}
   708  			result = stdcall4(_WaitForMultipleObjects, 2,
   709  				uintptr(unsafe.Pointer(&[2]uintptr{getg().m.waitsema, getg().m.resumesema})),
   710  				0, uintptr(ms))
   711  			if result != _WAIT_OBJECT_0+1 {
   712  				// Not a suspend/resume event
   713  				break
   714  			}
   715  			elapsed = nanotime() - start
   716  			if elapsed >= ns {
   717  				return -1
   718  			}
   719  		}
   720  	}
   721  	switch result {
   722  	case _WAIT_OBJECT_0: // Signaled
   723  		return 0
   724  
   725  	case _WAIT_TIMEOUT:
   726  		return -1
   727  
   728  	case _WAIT_ABANDONED:
   729  		systemstack(func() {
   730  			throw("runtime.semasleep wait_abandoned")
   731  		})
   732  
   733  	case _WAIT_FAILED:
   734  		systemstack(func() {
   735  			print("runtime: waitforsingleobject wait_failed; errno=", getlasterror(), "\n")
   736  			throw("runtime.semasleep wait_failed")
   737  		})
   738  
   739  	default:
   740  		systemstack(func() {
   741  			print("runtime: waitforsingleobject unexpected; result=", result, "\n")
   742  			throw("runtime.semasleep unexpected")
   743  		})
   744  	}
   745  
   746  	return -1 // unreachable
   747  }
   748  
   749  //go:nosplit
   750  func semawakeup(mp *m) {
   751  	if stdcall1(_SetEvent, mp.waitsema) == 0 {
   752  		systemstack(func() {
   753  			print("runtime: setevent failed; errno=", getlasterror(), "\n")
   754  			throw("runtime.semawakeup")
   755  		})
   756  	}
   757  }
   758  
   759  //go:nosplit
   760  func semacreate(mp *m) {
   761  	if mp.waitsema != 0 {
   762  		return
   763  	}
   764  	mp.waitsema = stdcall4(_CreateEventA, 0, 0, 0, 0)
   765  	if mp.waitsema == 0 {
   766  		systemstack(func() {
   767  			print("runtime: createevent failed; errno=", getlasterror(), "\n")
   768  			throw("runtime.semacreate")
   769  		})
   770  	}
   771  	mp.resumesema = stdcall4(_CreateEventA, 0, 0, 0, 0)
   772  	if mp.resumesema == 0 {
   773  		systemstack(func() {
   774  			print("runtime: createevent failed; errno=", getlasterror(), "\n")
   775  			throw("runtime.semacreate")
   776  		})
   777  		stdcall1(_CloseHandle, mp.waitsema)
   778  		mp.waitsema = 0
   779  	}
   780  }
   781  
   782  // May run with m.p==nil, so write barriers are not allowed. This
   783  // function is called by newosproc0, so it is also required to
   784  // operate without stack guards.
   785  //
   786  //go:nowritebarrierrec
   787  //go:nosplit
   788  func newosproc(mp *m) {
   789  	// We pass 0 for the stack size to use the default for this binary.
   790  	thandle := stdcall6(_CreateThread, 0, 0,
   791  		abi.FuncPCABI0(tstart_stdcall), uintptr(unsafe.Pointer(mp)),
   792  		0, 0)
   793  
   794  	if thandle == 0 {
   795  		if atomic.Load(&exiting) != 0 {
   796  			// CreateThread may fail if called
   797  			// concurrently with ExitProcess. If this
   798  			// happens, just freeze this thread and let
   799  			// the process exit. See issue #18253.
   800  			lock(&deadlock)
   801  			lock(&deadlock)
   802  		}
   803  		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", getlasterror(), ")\n")
   804  		throw("runtime.newosproc")
   805  	}
   806  
   807  	// Close thandle to avoid leaking the thread object if it exits.
   808  	stdcall1(_CloseHandle, thandle)
   809  }
   810  
   811  // Used by the C library build mode. On Linux this function would allocate a
   812  // stack, but that's not necessary for Windows. No stack guards are present
   813  // and the GC has not been initialized, so write barriers will fail.
   814  //
   815  //go:nowritebarrierrec
   816  //go:nosplit
   817  func newosproc0(mp *m, stk unsafe.Pointer) {
   818  	// TODO: this is completely broken. The args passed to newosproc0 (in asm_amd64.s)
   819  	// are stacksize and function, not *m and stack.
   820  	// Check os_linux.go for an implementation that might actually work.
   821  	throw("bad newosproc0")
   822  }
   823  
   824  func exitThread(wait *atomic.Uint32) {
   825  	// We should never reach exitThread on Windows because we let
   826  	// the OS clean up threads.
   827  	throw("exitThread")
   828  }
   829  
   830  // Called to initialize a new m (including the bootstrap m).
   831  // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
   832  func mpreinit(mp *m) {
   833  }
   834  
   835  //go:nosplit
   836  func sigsave(p *sigset) {
   837  }
   838  
   839  //go:nosplit
   840  func msigrestore(sigmask sigset) {
   841  }
   842  
   843  //go:nosplit
   844  //go:nowritebarrierrec
   845  func clearSignalHandlers() {
   846  }
   847  
   848  //go:nosplit
   849  func sigblock(exiting bool) {
   850  }
   851  
   852  // Called to initialize a new m (including the bootstrap m).
   853  // Called on the new thread, cannot allocate memory.
   854  func minit() {
   855  	var thandle uintptr
   856  	if stdcall7(_DuplicateHandle, currentProcess, currentThread, currentProcess, uintptr(unsafe.Pointer(&thandle)), 0, 0, _DUPLICATE_SAME_ACCESS) == 0 {
   857  		print("runtime.minit: duplicatehandle failed; errno=", getlasterror(), "\n")
   858  		throw("runtime.minit: duplicatehandle failed")
   859  	}
   860  
   861  	mp := getg().m
   862  	lock(&mp.threadLock)
   863  	mp.thread = thandle
   864  	mp.procid = uint64(stdcall0(_GetCurrentThreadId))
   865  
   866  	// Configure usleep timer, if possible.
   867  	if mp.highResTimer == 0 && haveHighResTimer {
   868  		mp.highResTimer = createHighResTimer()
   869  		if mp.highResTimer == 0 {
   870  			print("runtime: CreateWaitableTimerEx failed; errno=", getlasterror(), "\n")
   871  			throw("CreateWaitableTimerEx when creating timer failed")
   872  		}
   873  	}
   874  	unlock(&mp.threadLock)
   875  
   876  	// Query the true stack base from the OS. Currently we're
   877  	// running on a small assumed stack.
   878  	var mbi memoryBasicInformation
   879  	res := stdcall3(_VirtualQuery, uintptr(unsafe.Pointer(&mbi)), uintptr(unsafe.Pointer(&mbi)), unsafe.Sizeof(mbi))
   880  	if res == 0 {
   881  		print("runtime: VirtualQuery failed; errno=", getlasterror(), "\n")
   882  		throw("VirtualQuery for stack base failed")
   883  	}
   884  	// The system leaves an 8K PAGE_GUARD region at the bottom of
   885  	// the stack (in theory VirtualQuery isn't supposed to include
   886  	// that, but it does). Add an additional 8K of slop for
   887  	// calling C functions that don't have stack checks and for
   888  	// lastcontinuehandler. We shouldn't be anywhere near this
   889  	// bound anyway.
   890  	base := mbi.allocationBase + 16<<10
   891  	// Sanity check the stack bounds.
   892  	g0 := getg()
   893  	if base > g0.stack.hi || g0.stack.hi-base > 64<<20 {
   894  		print("runtime: g0 stack [", hex(base), ",", hex(g0.stack.hi), ")\n")
   895  		throw("bad g0 stack")
   896  	}
   897  	g0.stack.lo = base
   898  	g0.stackguard0 = g0.stack.lo + stackGuard
   899  	g0.stackguard1 = g0.stackguard0
   900  	// Sanity check the SP.
   901  	stackcheck()
   902  }
   903  
   904  // Called from dropm to undo the effect of an minit.
   905  //
   906  //go:nosplit
   907  func unminit() {
   908  	mp := getg().m
   909  	lock(&mp.threadLock)
   910  	if mp.thread != 0 {
   911  		stdcall1(_CloseHandle, mp.thread)
   912  		mp.thread = 0
   913  	}
   914  	unlock(&mp.threadLock)
   915  
   916  	mp.procid = 0
   917  }
   918  
   919  // Called from exitm, but not from drop, to undo the effect of thread-owned
   920  // resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
   921  //
   922  //go:nosplit
   923  func mdestroy(mp *m) {
   924  	if mp.highResTimer != 0 {
   925  		stdcall1(_CloseHandle, mp.highResTimer)
   926  		mp.highResTimer = 0
   927  	}
   928  	if mp.waitsema != 0 {
   929  		stdcall1(_CloseHandle, mp.waitsema)
   930  		mp.waitsema = 0
   931  	}
   932  	if mp.resumesema != 0 {
   933  		stdcall1(_CloseHandle, mp.resumesema)
   934  		mp.resumesema = 0
   935  	}
   936  }
   937  
   938  // asmstdcall_trampoline calls asmstdcall converting from Go to C calling convention.
   939  func asmstdcall_trampoline(args unsafe.Pointer)
   940  
   941  // stdcall_no_g calls asmstdcall on os stack without using g.
   942  //
   943  //go:nosplit
   944  func stdcall_no_g(fn stdFunction, n int, args uintptr) uintptr {
   945  	libcall := libcall{
   946  		fn:   uintptr(unsafe.Pointer(fn)),
   947  		n:    uintptr(n),
   948  		args: args,
   949  	}
   950  	asmstdcall_trampoline(noescape(unsafe.Pointer(&libcall)))
   951  	return libcall.r1
   952  }
   953  
   954  // Calling stdcall on os stack.
   955  // May run during STW, so write barriers are not allowed.
   956  //
   957  //go:nowritebarrier
   958  //go:nosplit
   959  func stdcall(fn stdFunction) uintptr {
   960  	gp := getg()
   961  	mp := gp.m
   962  	mp.libcall.fn = uintptr(unsafe.Pointer(fn))
   963  	resetLibcall := false
   964  	if mp.profilehz != 0 && mp.libcallsp == 0 {
   965  		// leave pc/sp for cpu profiler
   966  		mp.libcallg.set(gp)
   967  		mp.libcallpc = getcallerpc()
   968  		// sp must be the last, because once async cpu profiler finds
   969  		// all three values to be non-zero, it will use them
   970  		mp.libcallsp = getcallersp()
   971  		resetLibcall = true // See comment in sys_darwin.go:libcCall
   972  	}
   973  	asmcgocall(asmstdcallAddr, unsafe.Pointer(&mp.libcall))
   974  	if resetLibcall {
   975  		mp.libcallsp = 0
   976  	}
   977  	return mp.libcall.r1
   978  }
   979  
   980  //go:nosplit
   981  func stdcall0(fn stdFunction) uintptr {
   982  	mp := getg().m
   983  	mp.libcall.n = 0
   984  	mp.libcall.args = 0
   985  	return stdcall(fn)
   986  }
   987  
   988  //go:nosplit
   989  //go:cgo_unsafe_args
   990  func stdcall1(fn stdFunction, a0 uintptr) uintptr {
   991  	mp := getg().m
   992  	mp.libcall.n = 1
   993  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
   994  	return stdcall(fn)
   995  }
   996  
   997  //go:nosplit
   998  //go:cgo_unsafe_args
   999  func stdcall2(fn stdFunction, a0, a1 uintptr) uintptr {
  1000  	mp := getg().m
  1001  	mp.libcall.n = 2
  1002  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1003  	return stdcall(fn)
  1004  }
  1005  
  1006  //go:nosplit
  1007  //go:cgo_unsafe_args
  1008  func stdcall3(fn stdFunction, a0, a1, a2 uintptr) uintptr {
  1009  	mp := getg().m
  1010  	mp.libcall.n = 3
  1011  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1012  	return stdcall(fn)
  1013  }
  1014  
  1015  //go:nosplit
  1016  //go:cgo_unsafe_args
  1017  func stdcall4(fn stdFunction, a0, a1, a2, a3 uintptr) uintptr {
  1018  	mp := getg().m
  1019  	mp.libcall.n = 4
  1020  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1021  	return stdcall(fn)
  1022  }
  1023  
  1024  //go:nosplit
  1025  //go:cgo_unsafe_args
  1026  func stdcall5(fn stdFunction, a0, a1, a2, a3, a4 uintptr) uintptr {
  1027  	mp := getg().m
  1028  	mp.libcall.n = 5
  1029  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1030  	return stdcall(fn)
  1031  }
  1032  
  1033  //go:nosplit
  1034  //go:cgo_unsafe_args
  1035  func stdcall6(fn stdFunction, a0, a1, a2, a3, a4, a5 uintptr) uintptr {
  1036  	mp := getg().m
  1037  	mp.libcall.n = 6
  1038  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1039  	return stdcall(fn)
  1040  }
  1041  
  1042  //go:nosplit
  1043  //go:cgo_unsafe_args
  1044  func stdcall7(fn stdFunction, a0, a1, a2, a3, a4, a5, a6 uintptr) uintptr {
  1045  	mp := getg().m
  1046  	mp.libcall.n = 7
  1047  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1048  	return stdcall(fn)
  1049  }
  1050  
  1051  //go:nosplit
  1052  //go:cgo_unsafe_args
  1053  func stdcall8(fn stdFunction, a0, a1, a2, a3, a4, a5, a6, a7 uintptr) uintptr {
  1054  	mp := getg().m
  1055  	mp.libcall.n = 8
  1056  	mp.libcall.args = uintptr(noescape(unsafe.Pointer(&a0)))
  1057  	return stdcall(fn)
  1058  }
  1059  
  1060  // These must run on the system stack only.
  1061  
  1062  //go:nosplit
  1063  func osyield_no_g() {
  1064  	stdcall_no_g(_SwitchToThread, 0, 0)
  1065  }
  1066  
  1067  //go:nosplit
  1068  func osyield() {
  1069  	systemstack(func() {
  1070  		stdcall0(_SwitchToThread)
  1071  	})
  1072  }
  1073  
  1074  //go:nosplit
  1075  func usleep_no_g(us uint32) {
  1076  	timeout := uintptr(us) / 1000 // ms units
  1077  	args := [...]uintptr{_INVALID_HANDLE_VALUE, timeout}
  1078  	stdcall_no_g(_WaitForSingleObject, len(args), uintptr(noescape(unsafe.Pointer(&args[0]))))
  1079  }
  1080  
  1081  //go:nosplit
  1082  func usleep(us uint32) {
  1083  	systemstack(func() {
  1084  		var h, timeout uintptr
  1085  		// If the high-res timer is available and its handle has been allocated for this m, use it.
  1086  		// Otherwise fall back to the low-res one, which doesn't need a handle.
  1087  		if haveHighResTimer && getg().m.highResTimer != 0 {
  1088  			h = getg().m.highResTimer
  1089  			dt := -10 * int64(us) // relative sleep (negative), 100ns units
  1090  			stdcall6(_SetWaitableTimer, h, uintptr(unsafe.Pointer(&dt)), 0, 0, 0, 0)
  1091  			timeout = _INFINITE
  1092  		} else {
  1093  			h = _INVALID_HANDLE_VALUE
  1094  			timeout = uintptr(us) / 1000 // ms units
  1095  		}
  1096  		stdcall2(_WaitForSingleObject, h, timeout)
  1097  	})
  1098  }
  1099  
  1100  func ctrlHandler(_type uint32) uintptr {
  1101  	var s uint32
  1102  
  1103  	switch _type {
  1104  	case _CTRL_C_EVENT, _CTRL_BREAK_EVENT:
  1105  		s = _SIGINT
  1106  	case _CTRL_CLOSE_EVENT, _CTRL_LOGOFF_EVENT, _CTRL_SHUTDOWN_EVENT:
  1107  		s = _SIGTERM
  1108  	default:
  1109  		return 0
  1110  	}
  1111  
  1112  	if sigsend(s) {
  1113  		if s == _SIGTERM {
  1114  			// Windows terminates the process after this handler returns.
  1115  			// Block indefinitely to give signal handlers a chance to clean up,
  1116  			// but make sure to be properly parked first, so the rest of the
  1117  			// program can continue executing.
  1118  			block()
  1119  		}
  1120  		return 1
  1121  	}
  1122  	return 0
  1123  }
  1124  
  1125  // called from zcallback_windows_*.s to sys_windows_*.s
  1126  func callbackasm1()
  1127  
  1128  var profiletimer uintptr
  1129  
  1130  func profilem(mp *m, thread uintptr) {
  1131  	// Align Context to 16 bytes.
  1132  	var c *context
  1133  	var cbuf [unsafe.Sizeof(*c) + 15]byte
  1134  	c = (*context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
  1135  
  1136  	c.contextflags = _CONTEXT_CONTROL
  1137  	stdcall2(_GetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1138  
  1139  	gp := gFromSP(mp, c.sp())
  1140  
  1141  	sigprof(c.ip(), c.sp(), c.lr(), gp, mp)
  1142  }
  1143  
  1144  func gFromSP(mp *m, sp uintptr) *g {
  1145  	if gp := mp.g0; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1146  		return gp
  1147  	}
  1148  	if gp := mp.gsignal; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1149  		return gp
  1150  	}
  1151  	if gp := mp.curg; gp != nil && gp.stack.lo < sp && sp < gp.stack.hi {
  1152  		return gp
  1153  	}
  1154  	return nil
  1155  }
  1156  
  1157  func profileLoop() {
  1158  	stdcall2(_SetThreadPriority, currentThread, _THREAD_PRIORITY_HIGHEST)
  1159  
  1160  	for {
  1161  		stdcall2(_WaitForSingleObject, profiletimer, _INFINITE)
  1162  		first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
  1163  		for mp := first; mp != nil; mp = mp.alllink {
  1164  			if mp == getg().m {
  1165  				// Don't profile ourselves.
  1166  				continue
  1167  			}
  1168  
  1169  			lock(&mp.threadLock)
  1170  			// Do not profile threads blocked on Notes,
  1171  			// this includes idle worker threads,
  1172  			// idle timer thread, idle heap scavenger, etc.
  1173  			if mp.thread == 0 || mp.profilehz == 0 || mp.blocked {
  1174  				unlock(&mp.threadLock)
  1175  				continue
  1176  			}
  1177  			// Acquire our own handle to the thread.
  1178  			var thread uintptr
  1179  			if stdcall7(_DuplicateHandle, currentProcess, mp.thread, currentProcess, uintptr(unsafe.Pointer(&thread)), 0, 0, _DUPLICATE_SAME_ACCESS) == 0 {
  1180  				print("runtime: duplicatehandle failed; errno=", getlasterror(), "\n")
  1181  				throw("duplicatehandle failed")
  1182  			}
  1183  			unlock(&mp.threadLock)
  1184  
  1185  			// mp may exit between the DuplicateHandle
  1186  			// above and the SuspendThread. The handle
  1187  			// will remain valid, but SuspendThread may
  1188  			// fail.
  1189  			if int32(stdcall1(_SuspendThread, thread)) == -1 {
  1190  				// The thread no longer exists.
  1191  				stdcall1(_CloseHandle, thread)
  1192  				continue
  1193  			}
  1194  			if mp.profilehz != 0 && !mp.blocked {
  1195  				// Pass the thread handle in case mp
  1196  				// was in the process of shutting down.
  1197  				profilem(mp, thread)
  1198  			}
  1199  			stdcall1(_ResumeThread, thread)
  1200  			stdcall1(_CloseHandle, thread)
  1201  		}
  1202  	}
  1203  }
  1204  
  1205  func setProcessCPUProfiler(hz int32) {
  1206  	if profiletimer == 0 {
  1207  		var timer uintptr
  1208  		if haveHighResTimer {
  1209  			timer = createHighResTimer()
  1210  		} else {
  1211  			timer = stdcall3(_CreateWaitableTimerA, 0, 0, 0)
  1212  		}
  1213  		atomic.Storeuintptr(&profiletimer, timer)
  1214  		newm(profileLoop, nil, -1)
  1215  	}
  1216  }
  1217  
  1218  func setThreadCPUProfiler(hz int32) {
  1219  	ms := int32(0)
  1220  	due := ^int64(^uint64(1 << 63))
  1221  	if hz > 0 {
  1222  		ms = 1000 / hz
  1223  		if ms == 0 {
  1224  			ms = 1
  1225  		}
  1226  		due = int64(ms) * -10000
  1227  	}
  1228  	stdcall6(_SetWaitableTimer, profiletimer, uintptr(unsafe.Pointer(&due)), uintptr(ms), 0, 0, 0)
  1229  	atomic.Store((*uint32)(unsafe.Pointer(&getg().m.profilehz)), uint32(hz))
  1230  }
  1231  
  1232  const preemptMSupported = true
  1233  
  1234  // suspendLock protects simultaneous SuspendThread operations from
  1235  // suspending each other.
  1236  var suspendLock mutex
  1237  
  1238  func preemptM(mp *m) {
  1239  	if mp == getg().m {
  1240  		throw("self-preempt")
  1241  	}
  1242  
  1243  	// Synchronize with external code that may try to ExitProcess.
  1244  	if !atomic.Cas(&mp.preemptExtLock, 0, 1) {
  1245  		// External code is running. Fail the preemption
  1246  		// attempt.
  1247  		mp.preemptGen.Add(1)
  1248  		return
  1249  	}
  1250  
  1251  	// Acquire our own handle to mp's thread.
  1252  	lock(&mp.threadLock)
  1253  	if mp.thread == 0 {
  1254  		// The M hasn't been minit'd yet (or was just unminit'd).
  1255  		unlock(&mp.threadLock)
  1256  		atomic.Store(&mp.preemptExtLock, 0)
  1257  		mp.preemptGen.Add(1)
  1258  		return
  1259  	}
  1260  	var thread uintptr
  1261  	if stdcall7(_DuplicateHandle, currentProcess, mp.thread, currentProcess, uintptr(unsafe.Pointer(&thread)), 0, 0, _DUPLICATE_SAME_ACCESS) == 0 {
  1262  		print("runtime.preemptM: duplicatehandle failed; errno=", getlasterror(), "\n")
  1263  		throw("runtime.preemptM: duplicatehandle failed")
  1264  	}
  1265  	unlock(&mp.threadLock)
  1266  
  1267  	// Prepare thread context buffer. This must be aligned to 16 bytes.
  1268  	var c *context
  1269  	var cbuf [unsafe.Sizeof(*c) + 15]byte
  1270  	c = (*context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
  1271  	c.contextflags = _CONTEXT_CONTROL
  1272  
  1273  	// Serialize thread suspension. SuspendThread is asynchronous,
  1274  	// so it's otherwise possible for two threads to suspend each
  1275  	// other and deadlock. We must hold this lock until after
  1276  	// GetThreadContext, since that blocks until the thread is
  1277  	// actually suspended.
  1278  	lock(&suspendLock)
  1279  
  1280  	// Suspend the thread.
  1281  	if int32(stdcall1(_SuspendThread, thread)) == -1 {
  1282  		unlock(&suspendLock)
  1283  		stdcall1(_CloseHandle, thread)
  1284  		atomic.Store(&mp.preemptExtLock, 0)
  1285  		// The thread no longer exists. This shouldn't be
  1286  		// possible, but just acknowledge the request.
  1287  		mp.preemptGen.Add(1)
  1288  		return
  1289  	}
  1290  
  1291  	// We have to be very careful between this point and once
  1292  	// we've shown mp is at an async safe-point. This is like a
  1293  	// signal handler in the sense that mp could have been doing
  1294  	// anything when we stopped it, including holding arbitrary
  1295  	// locks.
  1296  
  1297  	// We have to get the thread context before inspecting the M
  1298  	// because SuspendThread only requests a suspend.
  1299  	// GetThreadContext actually blocks until it's suspended.
  1300  	stdcall2(_GetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1301  
  1302  	unlock(&suspendLock)
  1303  
  1304  	// Does it want a preemption and is it safe to preempt?
  1305  	gp := gFromSP(mp, c.sp())
  1306  	if gp != nil && wantAsyncPreempt(gp) {
  1307  		if ok, newpc := isAsyncSafePoint(gp, c.ip(), c.sp(), c.lr()); ok {
  1308  			// Inject call to asyncPreempt
  1309  			targetPC := abi.FuncPCABI0(asyncPreempt)
  1310  			switch GOARCH {
  1311  			default:
  1312  				throw("unsupported architecture")
  1313  			case "386", "amd64":
  1314  				// Make it look like the thread called targetPC.
  1315  				sp := c.sp()
  1316  				sp -= goarch.PtrSize
  1317  				*(*uintptr)(unsafe.Pointer(sp)) = newpc
  1318  				c.set_sp(sp)
  1319  				c.set_ip(targetPC)
  1320  
  1321  			case "arm":
  1322  				// Push LR. The injected call is responsible
  1323  				// for restoring LR. gentraceback is aware of
  1324  				// this extra slot. See sigctxt.pushCall in
  1325  				// signal_arm.go, which is similar except we
  1326  				// subtract 1 from IP here.
  1327  				sp := c.sp()
  1328  				sp -= goarch.PtrSize
  1329  				c.set_sp(sp)
  1330  				*(*uint32)(unsafe.Pointer(sp)) = uint32(c.lr())
  1331  				c.set_lr(newpc - 1)
  1332  				c.set_ip(targetPC)
  1333  
  1334  			case "arm64":
  1335  				// Push LR. The injected call is responsible
  1336  				// for restoring LR. gentraceback is aware of
  1337  				// this extra slot. See sigctxt.pushCall in
  1338  				// signal_arm64.go.
  1339  				sp := c.sp() - 16 // SP needs 16-byte alignment
  1340  				c.set_sp(sp)
  1341  				*(*uint64)(unsafe.Pointer(sp)) = uint64(c.lr())
  1342  				c.set_lr(newpc)
  1343  				c.set_ip(targetPC)
  1344  			}
  1345  			stdcall2(_SetThreadContext, thread, uintptr(unsafe.Pointer(c)))
  1346  		}
  1347  	}
  1348  
  1349  	atomic.Store(&mp.preemptExtLock, 0)
  1350  
  1351  	// Acknowledge the preemption.
  1352  	mp.preemptGen.Add(1)
  1353  
  1354  	stdcall1(_ResumeThread, thread)
  1355  	stdcall1(_CloseHandle, thread)
  1356  }
  1357  
  1358  // osPreemptExtEnter is called before entering external code that may
  1359  // call ExitProcess.
  1360  //
  1361  // This must be nosplit because it may be called from a syscall with
  1362  // untyped stack slots, so the stack must not be grown or scanned.
  1363  //
  1364  //go:nosplit
  1365  func osPreemptExtEnter(mp *m) {
  1366  	for !atomic.Cas(&mp.preemptExtLock, 0, 1) {
  1367  		// An asynchronous preemption is in progress. It's not
  1368  		// safe to enter external code because it may call
  1369  		// ExitProcess and deadlock with SuspendThread.
  1370  		// Ideally we would do the preemption ourselves, but
  1371  		// can't since there may be untyped syscall arguments
  1372  		// on the stack. Instead, just wait and encourage the
  1373  		// SuspendThread APC to run. The preemption should be
  1374  		// done shortly.
  1375  		osyield()
  1376  	}
  1377  	// Asynchronous preemption is now blocked.
  1378  }
  1379  
  1380  // osPreemptExtExit is called after returning from external code that
  1381  // may call ExitProcess.
  1382  //
  1383  // See osPreemptExtEnter for why this is nosplit.
  1384  //
  1385  //go:nosplit
  1386  func osPreemptExtExit(mp *m) {
  1387  	atomic.Store(&mp.preemptExtLock, 0)
  1388  }
  1389  

View as plain text