os_darwin.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  	"unsafe"
    10  )
    11  
    12  type mOS struct {
    13  	initialized bool
    14  	mutex       pthreadmutex
    15  	cond        pthreadcond
    16  	count       int
    17  }
    18  
    19  func unimplemented(name string) {
    20  	println(name, "not implemented")
    21  	*(*int)(unsafe.Pointer(uintptr(1231))) = 1231
    22  }
    23  
    24  //go:nosplit
    25  func semacreate(mp *m) {
    26  	if mp.initialized {
    27  		return
    28  	}
    29  	mp.initialized = true
    30  	if err := pthread_mutex_init(&mp.mutex, nil); err != 0 {
    31  		throw("pthread_mutex_init")
    32  	}
    33  	if err := pthread_cond_init(&mp.cond, nil); err != 0 {
    34  		throw("pthread_cond_init")
    35  	}
    36  }
    37  
    38  //go:nosplit
    39  func semasleep(ns int64) int32 {
    40  	var start int64
    41  	if ns >= 0 {
    42  		start = nanotime()
    43  	}
    44  	mp := getg().m
    45  	pthread_mutex_lock(&mp.mutex)
    46  	for {
    47  		if mp.count > 0 {
    48  			mp.count--
    49  			pthread_mutex_unlock(&mp.mutex)
    50  			return 0
    51  		}
    52  		if ns >= 0 {
    53  			spent := nanotime() - start
    54  			if spent >= ns {
    55  				pthread_mutex_unlock(&mp.mutex)
    56  				return -1
    57  			}
    58  			var t timespec
    59  			t.setNsec(ns - spent)
    60  			err := pthread_cond_timedwait_relative_np(&mp.cond, &mp.mutex, &t)
    61  			if err == _ETIMEDOUT {
    62  				pthread_mutex_unlock(&mp.mutex)
    63  				return -1
    64  			}
    65  		} else {
    66  			pthread_cond_wait(&mp.cond, &mp.mutex)
    67  		}
    68  	}
    69  }
    70  
    71  //go:nosplit
    72  func semawakeup(mp *m) {
    73  	pthread_mutex_lock(&mp.mutex)
    74  	mp.count++
    75  	if mp.count > 0 {
    76  		pthread_cond_signal(&mp.cond)
    77  	}
    78  	pthread_mutex_unlock(&mp.mutex)
    79  }
    80  
    81  // The read and write file descriptors used by the sigNote functions.
    82  var sigNoteRead, sigNoteWrite int32
    83  
    84  // sigNoteSetup initializes an async-signal-safe note.
    85  //
    86  // The current implementation of notes on Darwin is not async-signal-safe,
    87  // because the functions pthread_mutex_lock, pthread_cond_signal, and
    88  // pthread_mutex_unlock, called by semawakeup, are not async-signal-safe.
    89  // There is only one case where we need to wake up a note from a signal
    90  // handler: the sigsend function. The signal handler code does not require
    91  // all the features of notes: it does not need to do a timed wait.
    92  // This is a separate implementation of notes, based on a pipe, that does
    93  // not support timed waits but is async-signal-safe.
    94  func sigNoteSetup(*note) {
    95  	if sigNoteRead != 0 || sigNoteWrite != 0 {
    96  		throw("duplicate sigNoteSetup")
    97  	}
    98  	var errno int32
    99  	sigNoteRead, sigNoteWrite, errno = pipe()
   100  	if errno != 0 {
   101  		throw("pipe failed")
   102  	}
   103  	closeonexec(sigNoteRead)
   104  	closeonexec(sigNoteWrite)
   105  
   106  	// Make the write end of the pipe non-blocking, so that if the pipe
   107  	// buffer is somehow full we will not block in the signal handler.
   108  	// Leave the read end of the pipe blocking so that we will block
   109  	// in sigNoteSleep.
   110  	setNonblock(sigNoteWrite)
   111  }
   112  
   113  // sigNoteWakeup wakes up a thread sleeping on a note created by sigNoteSetup.
   114  func sigNoteWakeup(*note) {
   115  	var b byte
   116  	write(uintptr(sigNoteWrite), unsafe.Pointer(&b), 1)
   117  }
   118  
   119  // sigNoteSleep waits for a note created by sigNoteSetup to be woken.
   120  func sigNoteSleep(*note) {
   121  	for {
   122  		var b byte
   123  		entersyscallblock()
   124  		n := read(sigNoteRead, unsafe.Pointer(&b), 1)
   125  		exitsyscall()
   126  		if n != -_EINTR {
   127  			return
   128  		}
   129  	}
   130  }
   131  
   132  // BSD interface for threading.
   133  func osinit() {
   134  	// pthread_create delayed until end of goenvs so that we
   135  	// can look at the environment first.
   136  
   137  	ncpu = getncpu()
   138  	physPageSize = getPageSize()
   139  }
   140  
   141  func sysctlbynameInt32(name []byte) (int32, int32) {
   142  	out := int32(0)
   143  	nout := unsafe.Sizeof(out)
   144  	ret := sysctlbyname(&name[0], (*byte)(unsafe.Pointer(&out)), &nout, nil, 0)
   145  	return ret, out
   146  }
   147  
   148  //go:linkname internal_cpu_getsysctlbyname internal/cpu.getsysctlbyname
   149  func internal_cpu_getsysctlbyname(name []byte) (int32, int32) {
   150  	return sysctlbynameInt32(name)
   151  }
   152  
   153  const (
   154  	_CTL_HW      = 6
   155  	_HW_NCPU     = 3
   156  	_HW_PAGESIZE = 7
   157  )
   158  
   159  func getncpu() int32 {
   160  	// Use sysctl to fetch hw.ncpu.
   161  	mib := [2]uint32{_CTL_HW, _HW_NCPU}
   162  	out := uint32(0)
   163  	nout := unsafe.Sizeof(out)
   164  	ret := sysctl(&mib[0], 2, (*byte)(unsafe.Pointer(&out)), &nout, nil, 0)
   165  	if ret >= 0 && int32(out) > 0 {
   166  		return int32(out)
   167  	}
   168  	return 1
   169  }
   170  
   171  func getPageSize() uintptr {
   172  	// Use sysctl to fetch hw.pagesize.
   173  	mib := [2]uint32{_CTL_HW, _HW_PAGESIZE}
   174  	out := uint32(0)
   175  	nout := unsafe.Sizeof(out)
   176  	ret := sysctl(&mib[0], 2, (*byte)(unsafe.Pointer(&out)), &nout, nil, 0)
   177  	if ret >= 0 && int32(out) > 0 {
   178  		return uintptr(out)
   179  	}
   180  	return 0
   181  }
   182  
   183  var urandom_dev = []byte("/dev/urandom\x00")
   184  
   185  //go:nosplit
   186  func getRandomData(r []byte) {
   187  	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
   188  	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
   189  	closefd(fd)
   190  	extendRandom(r, int(n))
   191  }
   192  
   193  func goenvs() {
   194  	goenvs_unix()
   195  }
   196  
   197  // May run with m.p==nil, so write barriers are not allowed.
   198  //go:nowritebarrierrec
   199  func newosproc(mp *m) {
   200  	stk := unsafe.Pointer(mp.g0.stack.hi)
   201  	if false {
   202  		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
   203  	}
   204  
   205  	// Initialize an attribute object.
   206  	var attr pthreadattr
   207  	var err int32
   208  	err = pthread_attr_init(&attr)
   209  	if err != 0 {
   210  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   211  		exit(1)
   212  	}
   213  
   214  	// Find out OS stack size for our own stack guard.
   215  	var stacksize uintptr
   216  	if pthread_attr_getstacksize(&attr, &stacksize) != 0 {
   217  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   218  		exit(1)
   219  	}
   220  	mp.g0.stack.hi = stacksize // for mstart
   221  
   222  	// Tell the pthread library we won't join with this thread.
   223  	if pthread_attr_setdetachstate(&attr, _PTHREAD_CREATE_DETACHED) != 0 {
   224  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   225  		exit(1)
   226  	}
   227  
   228  	// Finally, create the thread. It starts at mstart_stub, which does some low-level
   229  	// setup and then calls mstart.
   230  	var oset sigset
   231  	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
   232  	err = pthread_create(&attr, abi.FuncPCABI0(mstart_stub), unsafe.Pointer(mp))
   233  	sigprocmask(_SIG_SETMASK, &oset, nil)
   234  	if err != 0 {
   235  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   236  		exit(1)
   237  	}
   238  }
   239  
   240  // glue code to call mstart from pthread_create.
   241  func mstart_stub()
   242  
   243  // newosproc0 is a version of newosproc that can be called before the runtime
   244  // is initialized.
   245  //
   246  // This function is not safe to use after initialization as it does not pass an M as fnarg.
   247  //
   248  //go:nosplit
   249  func newosproc0(stacksize uintptr, fn uintptr) {
   250  	// Initialize an attribute object.
   251  	var attr pthreadattr
   252  	var err int32
   253  	err = pthread_attr_init(&attr)
   254  	if err != 0 {
   255  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   256  		exit(1)
   257  	}
   258  
   259  	// The caller passes in a suggested stack size,
   260  	// from when we allocated the stack and thread ourselves,
   261  	// without libpthread. Now that we're using libpthread,
   262  	// we use the OS default stack size instead of the suggestion.
   263  	// Find out that stack size for our own stack guard.
   264  	if pthread_attr_getstacksize(&attr, &stacksize) != 0 {
   265  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   266  		exit(1)
   267  	}
   268  	g0.stack.hi = stacksize // for mstart
   269  	memstats.stacks_sys.add(int64(stacksize))
   270  
   271  	// Tell the pthread library we won't join with this thread.
   272  	if pthread_attr_setdetachstate(&attr, _PTHREAD_CREATE_DETACHED) != 0 {
   273  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   274  		exit(1)
   275  	}
   276  
   277  	// Finally, create the thread. It starts at mstart_stub, which does some low-level
   278  	// setup and then calls mstart.
   279  	var oset sigset
   280  	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
   281  	err = pthread_create(&attr, fn, nil)
   282  	sigprocmask(_SIG_SETMASK, &oset, nil)
   283  	if err != 0 {
   284  		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
   285  		exit(1)
   286  	}
   287  }
   288  
   289  var failallocatestack = []byte("runtime: failed to allocate stack for the new OS thread\n")
   290  var failthreadcreate = []byte("runtime: failed to create new OS thread\n")
   291  
   292  // Called to do synchronous initialization of Go code built with
   293  // -buildmode=c-archive or -buildmode=c-shared.
   294  // None of the Go runtime is initialized.
   295  //go:nosplit
   296  //go:nowritebarrierrec
   297  func libpreinit() {
   298  	initsig(true)
   299  }
   300  
   301  // Called to initialize a new m (including the bootstrap m).
   302  // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
   303  func mpreinit(mp *m) {
   304  	mp.gsignal = malg(32 * 1024) // OS X wants >= 8K
   305  	mp.gsignal.m = mp
   306  	if GOOS == "darwin" && GOARCH == "arm64" {
   307  		// mlock the signal stack to work around a kernel bug where it may
   308  		// SIGILL when the signal stack is not faulted in while a signal
   309  		// arrives. See issue 42774.
   310  		mlock(unsafe.Pointer(mp.gsignal.stack.hi-physPageSize), physPageSize)
   311  	}
   312  }
   313  
   314  // Called to initialize a new m (including the bootstrap m).
   315  // Called on the new thread, cannot allocate memory.
   316  func minit() {
   317  	// iOS does not support alternate signal stack.
   318  	// The signal handler handles it directly.
   319  	if !(GOOS == "ios" && GOARCH == "arm64") {
   320  		minitSignalStack()
   321  	}
   322  	minitSignalMask()
   323  	getg().m.procid = uint64(pthread_self())
   324  }
   325  
   326  // Called from dropm to undo the effect of an minit.
   327  //go:nosplit
   328  func unminit() {
   329  	// iOS does not support alternate signal stack.
   330  	// See minit.
   331  	if !(GOOS == "ios" && GOARCH == "arm64") {
   332  		unminitSignals()
   333  	}
   334  }
   335  
   336  // Called from exitm, but not from drop, to undo the effect of thread-owned
   337  // resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
   338  func mdestroy(mp *m) {
   339  }
   340  
   341  //go:nosplit
   342  func osyield_no_g() {
   343  	usleep_no_g(1)
   344  }
   345  
   346  //go:nosplit
   347  func osyield() {
   348  	usleep(1)
   349  }
   350  
   351  const (
   352  	_NSIG        = 32
   353  	_SI_USER     = 0 /* empirically true, but not what headers say */
   354  	_SIG_BLOCK   = 1
   355  	_SIG_UNBLOCK = 2
   356  	_SIG_SETMASK = 3
   357  	_SS_DISABLE  = 4
   358  )
   359  
   360  //extern SigTabTT runtime·sigtab[];
   361  
   362  type sigset uint32
   363  
   364  var sigset_all = ^sigset(0)
   365  
   366  //go:nosplit
   367  //go:nowritebarrierrec
   368  func setsig(i uint32, fn uintptr) {
   369  	var sa usigactiont
   370  	sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK | _SA_RESTART
   371  	sa.sa_mask = ^uint32(0)
   372  	if fn == funcPC(sighandler) { // funcPC(sighandler) matches the callers in signal_unix.go
   373  		if iscgo {
   374  			fn = abi.FuncPCABI0(cgoSigtramp)
   375  		} else {
   376  			fn = abi.FuncPCABI0(sigtramp)
   377  		}
   378  	}
   379  	*(*uintptr)(unsafe.Pointer(&sa.__sigaction_u)) = fn
   380  	sigaction(i, &sa, nil)
   381  }
   382  
   383  // sigtramp is the callback from libc when a signal is received.
   384  // It is called with the C calling convention.
   385  func sigtramp()
   386  func cgoSigtramp()
   387  
   388  //go:nosplit
   389  //go:nowritebarrierrec
   390  func setsigstack(i uint32) {
   391  	var osa usigactiont
   392  	sigaction(i, nil, &osa)
   393  	handler := *(*uintptr)(unsafe.Pointer(&osa.__sigaction_u))
   394  	if osa.sa_flags&_SA_ONSTACK != 0 {
   395  		return
   396  	}
   397  	var sa usigactiont
   398  	*(*uintptr)(unsafe.Pointer(&sa.__sigaction_u)) = handler
   399  	sa.sa_mask = osa.sa_mask
   400  	sa.sa_flags = osa.sa_flags | _SA_ONSTACK
   401  	sigaction(i, &sa, nil)
   402  }
   403  
   404  //go:nosplit
   405  //go:nowritebarrierrec
   406  func getsig(i uint32) uintptr {
   407  	var sa usigactiont
   408  	sigaction(i, nil, &sa)
   409  	return *(*uintptr)(unsafe.Pointer(&sa.__sigaction_u))
   410  }
   411  
   412  // setSignaltstackSP sets the ss_sp field of a stackt.
   413  //go:nosplit
   414  func setSignalstackSP(s *stackt, sp uintptr) {
   415  	*(*uintptr)(unsafe.Pointer(&s.ss_sp)) = sp
   416  }
   417  
   418  //go:nosplit
   419  //go:nowritebarrierrec
   420  func sigaddset(mask *sigset, i int) {
   421  	*mask |= 1 << (uint32(i) - 1)
   422  }
   423  
   424  func sigdelset(mask *sigset, i int) {
   425  	*mask &^= 1 << (uint32(i) - 1)
   426  }
   427  
   428  //go:linkname executablePath os.executablePath
   429  var executablePath string
   430  
   431  func sysargs(argc int32, argv **byte) {
   432  	// skip over argv, envv and the first string will be the path
   433  	n := argc + 1
   434  	for argv_index(argv, n) != nil {
   435  		n++
   436  	}
   437  	executablePath = gostringnocopy(argv_index(argv, n+1))
   438  
   439  	// strip "executable_path=" prefix if available, it's added after OS X 10.11.
   440  	const prefix = "executable_path="
   441  	if len(executablePath) > len(prefix) && executablePath[:len(prefix)] == prefix {
   442  		executablePath = executablePath[len(prefix):]
   443  	}
   444  }
   445  
   446  func signalM(mp *m, sig int) {
   447  	pthread_kill(pthread(mp.procid), uint32(sig))
   448  }
   449
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