1 files changed, 581 insertions, 1 deletions

diff --git a/libgo/go/runtime/signal_unix.go b/libgo/go/runtime/signal_unix.go
index f59c9b95497..43247538b66 100644
--- a/libgo/go/runtime/signal_unix.go
+++ b/libgo/go/runtime/signal_unix.go
@@ -6,7 +6,16 @@
 
 package runtime
 
-import _ "unsafe" // for go:linkname
+import (
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// For gccgo's C code to call:
+//go:linkname initsig runtime.initsig
+//go:linkname crash runtime.crash
+//go:linkname resetcpuprofiler runtime.resetcpuprofiler
+//go:linkname sigtrampgo runtime.sigtrampgo
 
 //go:linkname os_sigpipe os.sigpipe
 func os_sigpipe() {
@@ -19,3 +28,574 @@ func signame(sig uint32) string {
 	}
 	return sigtable[sig].name
 }
+
+const (
+	_SIG_DFL uintptr = 0
+	_SIG_IGN uintptr = 1
+)
+
+// Stores the signal handlers registered before Go installed its own.
+// These signal handlers will be invoked in cases where Go doesn't want to
+// handle a particular signal (e.g., signal occurred on a non-Go thread).
+// See sigfwdgo() for more information on when the signals are forwarded.
+//
+// Signal forwarding is currently available only on Darwin and Linux.
+var fwdSig [_NSIG]uintptr
+
+// channels for synchronizing signal mask updates with the signal mask
+// thread
+var (
+	disableSigChan  chan uint32
+	enableSigChan   chan uint32
+	maskUpdatedChan chan struct{}
+)
+
+func init() {
+	// _NSIG is the number of signals on this operating system.
+	// sigtable should describe what to do for all the possible signals.
+	if len(sigtable) != _NSIG {
+		print("runtime: len(sigtable)=", len(sigtable), " _NSIG=", _NSIG, "\n")
+		throw("bad sigtable len")
+	}
+}
+
+var signalsOK bool
+
+// Initialize signals.
+// Called by libpreinit so runtime may not be initialized.
+//go:nosplit
+//go:nowritebarrierrec
+func initsig(preinit bool) {
+	if !preinit {
+		// It's now OK for signal handlers to run.
+		signalsOK = true
+	}
+
+	// For c-archive/c-shared this is called by libpreinit with
+	// preinit == true.
+	if (isarchive || islibrary) && !preinit {
+		return
+	}
+
+	for i := uint32(0); i < _NSIG; i++ {
+		t := &sigtable[i]
+		if t.flags == 0 || t.flags&_SigDefault != 0 {
+			continue
+		}
+		fwdSig[i] = getsig(i)
+
+		if !sigInstallGoHandler(i) {
+			// Even if we are not installing a signal handler,
+			// set SA_ONSTACK if necessary.
+			if fwdSig[i] != _SIG_DFL && fwdSig[i] != _SIG_IGN {
+				setsigstack(i)
+			}
+			continue
+		}
+
+		t.flags |= _SigHandling
+		setsig(i, getSigtramp())
+	}
+}
+
+//go:nosplit
+//go:nowritebarrierrec
+func sigInstallGoHandler(sig uint32) bool {
+	// For some signals, we respect an inherited SIG_IGN handler
+	// rather than insist on installing our own default handler.
+	// Even these signals can be fetched using the os/signal package.
+	switch sig {
+	case _SIGHUP, _SIGINT:
+		if fwdSig[sig] == _SIG_IGN {
+			return false
+		}
+	}
+
+	t := &sigtable[sig]
+	if t.flags&_SigSetStack != 0 {
+		return false
+	}
+
+	// When built using c-archive or c-shared, only install signal
+	// handlers for synchronous signals.
+	if (isarchive || islibrary) && t.flags&_SigPanic == 0 {
+		return false
+	}
+
+	return true
+}
+
+func sigenable(sig uint32) {
+	if sig >= uint32(len(sigtable)) {
+		return
+	}
+
+	t := &sigtable[sig]
+	if t.flags&_SigNotify != 0 {
+		ensureSigM()
+		enableSigChan <- sig
+		<-maskUpdatedChan
+		if t.flags&_SigHandling == 0 {
+			t.flags |= _SigHandling
+			fwdSig[sig] = getsig(sig)
+			setsig(sig, getSigtramp())
+		}
+	}
+}
+
+func sigdisable(sig uint32) {
+	if sig >= uint32(len(sigtable)) {
+		return
+	}
+
+	t := &sigtable[sig]
+	if t.flags&_SigNotify != 0 {
+		ensureSigM()
+		disableSigChan <- sig
+		<-maskUpdatedChan
+
+		// If initsig does not install a signal handler for a
+		// signal, then to go back to the state before Notify
+		// we should remove the one we installed.
+		if !sigInstallGoHandler(sig) {
+			t.flags &^= _SigHandling
+			setsig(sig, fwdSig[sig])
+		}
+	}
+}
+
+func sigignore(sig uint32) {
+	if sig >= uint32(len(sigtable)) {
+		return
+	}
+
+	t := &sigtable[sig]
+	if t.flags&_SigNotify != 0 {
+		t.flags &^= _SigHandling
+		setsig(sig, _SIG_IGN)
+	}
+}
+
+func resetcpuprofiler(hz int32) {
+	var it _itimerval
+	if hz == 0 {
+		setitimer(_ITIMER_PROF, &it, nil)
+	} else {
+		it.it_interval.tv_sec = 0
+		it.it_interval.set_usec(1000000 / hz)
+		it.it_value = it.it_interval
+		setitimer(_ITIMER_PROF, &it, nil)
+	}
+	_g_ := getg()
+	_g_.m.profilehz = hz
+}
+
+func sigpipe() {
+	if sigsend(_SIGPIPE) {
+		return
+	}
+	dieFromSignal(_SIGPIPE)
+}
+
+// sigtrampgo is called from the signal handler function, sigtramp,
+// written in assembly code.
+// This is called by the signal handler, and the world may be stopped.
+//go:nosplit
+//go:nowritebarrierrec
+func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
+	if sigfwdgo(sig, info, ctx) {
+		return
+	}
+	g := getg()
+	if g == nil {
+		c := sigctxt{info, ctx}
+		if sig == _SIGPROF {
+			_, pc := getSiginfo(info, ctx)
+			sigprofNonGoPC(pc)
+			return
+		}
+		badsignal(uintptr(sig), &c)
+		return
+	}
+
+	setg(g.m.gsignal)
+	sighandler(sig, info, ctx, g)
+	setg(g)
+}
+
+// sigpanic turns a synchronous signal into a run-time panic.
+// If the signal handler sees a synchronous panic, it arranges the
+// stack to look like the function where the signal occurred called
+// sigpanic, sets the signal's PC value to sigpanic, and returns from
+// the signal handler. The effect is that the program will act as
+// though the function that got the signal simply called sigpanic
+// instead.
+func sigpanic() {
+	g := getg()
+	if !canpanic(g) {
+		throw("unexpected signal during runtime execution")
+	}
+
+	switch g.sig {
+	case _SIGBUS:
+		if g.sigcode0 == _BUS_ADRERR && g.sigcode1 < 0x1000 {
+			panicmem()
+		}
+		// Support runtime/debug.SetPanicOnFault.
+		if g.paniconfault {
+			panicmem()
+		}
+		print("unexpected fault address ", hex(g.sigcode1), "\n")
+		throw("fault")
+	case _SIGSEGV:
+		if (g.sigcode0 == 0 || g.sigcode0 == _SEGV_MAPERR || g.sigcode0 == _SEGV_ACCERR) && g.sigcode1 < 0x1000 {
+			panicmem()
+		}
+		// Support runtime/debug.SetPanicOnFault.
+		if g.paniconfault {
+			panicmem()
+		}
+		print("unexpected fault address ", hex(g.sigcode1), "\n")
+		throw("fault")
+	case _SIGFPE:
+		switch g.sigcode0 {
+		case _FPE_INTDIV:
+			panicdivide()
+		case _FPE_INTOVF:
+			panicoverflow()
+		}
+		panicfloat()
+	}
+
+	if g.sig >= uint32(len(sigtable)) {
+		// can't happen: we looked up g.sig in sigtable to decide to call sigpanic
+		throw("unexpected signal value")
+	}
+	panic(errorString(sigtable[g.sig].name))
+}
+
+// dieFromSignal kills the program with a signal.
+// This provides the expected exit status for the shell.
+// This is only called with fatal signals expected to kill the process.
+//go:nosplit
+//go:nowritebarrierrec
+func dieFromSignal(sig uint32) {
+	setsig(sig, _SIG_DFL)
+	unblocksig(sig)
+	raise(sig)
+
+	// That should have killed us. On some systems, though, raise
+	// sends the signal to the whole process rather than to just
+	// the current thread, which means that the signal may not yet
+	// have been delivered. Give other threads a chance to run and
+	// pick up the signal.
+	osyield()
+	osyield()
+	osyield()
+
+	// If we are still somehow running, just exit with the wrong status.
+	exit(2)
+}
+
+// raisebadsignal is called when a signal is received on a non-Go
+// thread, and the Go program does not want to handle it (that is, the
+// program has not called os/signal.Notify for the signal).
+func raisebadsignal(sig uint32, c *sigctxt) {
+	if sig == _SIGPROF {
+		// Ignore profiling signals that arrive on non-Go threads.
+		return
+	}
+
+	var handler uintptr
+	if sig >= _NSIG {
+		handler = _SIG_DFL
+	} else {
+		handler = fwdSig[sig]
+	}
+
+	// Reset the signal handler and raise the signal.
+	// We are currently running inside a signal handler, so the
+	// signal is blocked. We need to unblock it before raising the
+	// signal, or the signal we raise will be ignored until we return
+	// from the signal handler. We know that the signal was unblocked
+	// before entering the handler, or else we would not have received
+	// it. That means that we don't have to worry about blocking it
+	// again.
+	unblocksig(sig)
+	setsig(sig, handler)
+
+	// If we're linked into a non-Go program we want to try to
+	// avoid modifying the original context in which the signal
+	// was raised. If the handler is the default, we know it
+	// is non-recoverable, so we don't have to worry about
+	// re-installing sighandler. At this point we can just
+	// return and the signal will be re-raised and caught by
+	// the default handler with the correct context.
+	if (isarchive || islibrary) && handler == _SIG_DFL && c.sigcode() != _SI_USER {
+		return
+	}
+
+	raise(sig)
+
+	// Give the signal a chance to be delivered.
+	// In almost all real cases the program is about to crash,
+	// so sleeping here is not a waste of time.
+	usleep(1000)
+
+	// If the signal didn't cause the program to exit, restore the
+	// Go signal handler and carry on.
+	//
+	// We may receive another instance of the signal before we
+	// restore the Go handler, but that is not so bad: we know
+	// that the Go program has been ignoring the signal.
+	setsig(sig, getSigtramp())
+}
+
+func crash() {
+	if GOOS == "darwin" {
+		// OS X core dumps are linear dumps of the mapped memory,
+		// from the first virtual byte to the last, with zeros in the gaps.
+		// Because of the way we arrange the address space on 64-bit systems,
+		// this means the OS X core file will be >128 GB and even on a zippy
+		// workstation can take OS X well over an hour to write (uninterruptible).
+		// Save users from making that mistake.
+		if sys.PtrSize == 8 {
+			return
+		}
+	}
+
+	dieFromSignal(_SIGABRT)
+}
+
+// ensureSigM starts one global, sleeping thread to make sure at least one thread
+// is available to catch signals enabled for os/signal.
+func ensureSigM() {
+	if maskUpdatedChan != nil {
+		return
+	}
+	maskUpdatedChan = make(chan struct{})
+	disableSigChan = make(chan uint32)
+	enableSigChan = make(chan uint32)
+	go func() {
+		// Signal masks are per-thread, so make sure this goroutine stays on one
+		// thread.
+		LockOSThread()
+		defer UnlockOSThread()
+		// The sigBlocked mask contains the signals not active for os/signal,
+		// initially all signals except the essential. When signal.Notify()/Stop is called,
+		// sigenable/sigdisable in turn notify this thread to update its signal
+		// mask accordingly.
+		var sigBlocked sigset
+		sigfillset(&sigBlocked)
+		for i := range sigtable {
+			if sigtable[i].flags&_SigUnblock != 0 {
+				sigdelset(&sigBlocked, i)
+			}
+		}
+		sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
+		for {
+			select {
+			case sig := <-enableSigChan:
+				if sig > 0 {
+					sigdelset(&sigBlocked, int(sig))
+				}
+			case sig := <-disableSigChan:
+				if sig > 0 {
+					sigaddset(&sigBlocked, int(sig))
+				}
+			}
+			sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
+			maskUpdatedChan <- struct{}{}
+		}
+	}()
+}
+
+// This is called when we receive a signal when there is no signal stack.
+// This can only happen if non-Go code calls sigaltstack to disable the
+// signal stack.
+func noSignalStack(sig uint32) {
+	println("signal", sig, "received on thread with no signal stack")
+	throw("non-Go code disabled sigaltstack")
+}
+
+// This is called if we receive a signal when there is a signal stack
+// but we are not on it. This can only happen if non-Go code called
+// sigaction without setting the SS_ONSTACK flag.
+func sigNotOnStack(sig uint32) {
+	println("signal", sig, "received but handler not on signal stack")
+	throw("non-Go code set up signal handler without SA_ONSTACK flag")
+}
+
+// This runs on a foreign stack, without an m or a g. No stack split.
+//go:nosplit
+//go:norace
+//go:nowritebarrierrec
+func badsignal(sig uintptr, c *sigctxt) {
+	needm(0)
+	if !sigsend(uint32(sig)) {
+		// A foreign thread received the signal sig, and the
+		// Go code does not want to handle it.
+		raisebadsignal(uint32(sig), c)
+	}
+	dropm()
+}
+
+// Determines if the signal should be handled by Go and if not, forwards the
+// signal to the handler that was installed before Go's. Returns whether the
+// signal was forwarded.
+// This is called by the signal handler, and the world may be stopped.
+//go:nosplit
+//go:nowritebarrierrec
+func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
+	if sig >= uint32(len(sigtable)) {
+		return false
+	}
+	fwdFn := fwdSig[sig]
+
+	if !signalsOK {
+		// The only way we can get here is if we are in a
+		// library or archive, we installed a signal handler
+		// at program startup, but the Go runtime has not yet
+		// been initialized.
+		if fwdFn == _SIG_DFL {
+			dieFromSignal(sig)
+		} else {
+			sigfwd(fwdFn, sig, info, ctx)
+		}
+		return true
+	}
+
+	flags := sigtable[sig].flags
+
+	// If there is no handler to forward to, no need to forward.
+	if fwdFn == _SIG_DFL {
+		return false
+	}
+
+	// If we aren't handling the signal, forward it.
+	if flags&_SigHandling == 0 {
+		sigfwd(fwdFn, sig, info, ctx)
+		return true
+	}
+
+	// Only forward synchronous signals.
+	c := sigctxt{info, ctx}
+	if c.sigcode() == _SI_USER || flags&_SigPanic == 0 {
+		return false
+	}
+	// Determine if the signal occurred inside Go code. We test that:
+	//   (1) we were in a goroutine (i.e., m.curg != nil), and
+	//   (2) we weren't in CGO (i.e., m.curg.syscallsp == 0).
+	g := getg()
+	if g != nil && g.m != nil && g.m.curg != nil && g.m.curg.syscallsp == 0 {
+		return false
+	}
+	// Signal not handled by Go, forward it.
+	if fwdFn != _SIG_IGN {
+		sigfwd(fwdFn, sig, info, ctx)
+	}
+	return true
+}
+
+// msigsave saves the current thread's signal mask into mp.sigmask.
+// This is used to preserve the non-Go signal mask when a non-Go
+// thread calls a Go function.
+// This is nosplit and nowritebarrierrec because it is called by needm
+// which may be called on a non-Go thread with no g available.
+//go:nosplit
+//go:nowritebarrierrec
+func msigsave(mp *m) {
+	sigprocmask(_SIG_SETMASK, nil, &mp.sigmask)
+}
+
+// msigrestore sets the current thread's signal mask to sigmask.
+// This is used to restore the non-Go signal mask when a non-Go thread
+// calls a Go function.
+// This is nosplit and nowritebarrierrec because it is called by dropm
+// after g has been cleared.
+//go:nosplit
+//go:nowritebarrierrec
+func msigrestore(sigmask sigset) {
+	sigprocmask(_SIG_SETMASK, &sigmask, nil)
+}
+
+// sigblock blocks all signals in the current thread's signal mask.
+// This is used to block signals while setting up and tearing down g
+// when a non-Go thread calls a Go function.
+// The OS-specific code is expected to define sigset_all.
+// This is nosplit and nowritebarrierrec because it is called by needm
+// which may be called on a non-Go thread with no g available.
+//go:nosplit
+//go:nowritebarrierrec
+func sigblock() {
+	var set sigset
+	sigfillset(&set)
+	sigprocmask(_SIG_SETMASK, &set, nil)
+}
+
+// unblocksig removes sig from the current thread's signal mask.
+// This is nosplit and nowritebarrierrec because it is called from
+// dieFromSignal, which can be called by sigfwdgo while running in the
+// signal handler, on the signal stack, with no g available.
+//go:nosplit
+//go:nowritebarrierrec
+func unblocksig(sig uint32) {
+	var set sigset
+	sigemptyset(&set)
+	sigaddset(&set, int(sig))
+	sigprocmask(_SIG_UNBLOCK, &set, nil)
+}
+
+// minitSignals is called when initializing a new m to set the
+// thread's alternate signal stack and signal mask.
+func minitSignals() {
+	minitSignalStack()
+	minitSignalMask()
+}
+
+// minitSignalStack is called when initializing a new m to set the
+// alternate signal stack. If the alternate signal stack is not set
+// for the thread (the normal case) then set the alternate signal
+// stack to the gsignal stack. If the alternate signal stack is set
+// for the thread (the case when a non-Go thread sets the alternate
+// signal stack and then calls a Go function) then set the gsignal
+// stack to the alternate signal stack. Record which choice was made
+// in newSigstack, so that it can be undone in unminit.
+func minitSignalStack() {
+	_g_ := getg()
+	var st _stack_t
+	sigaltstack(nil, &st)
+	if st.ss_flags&_SS_DISABLE != 0 {
+		signalstack(_g_.m.gsignalstack, _g_.m.gsignalstacksize)
+		_g_.m.newSigstack = true
+	} else {
+		_g_.m.newSigstack = false
+	}
+}
+
+// minitSignalMask is called when initializing a new m to set the
+// thread's signal mask. When this is called all signals have been
+// blocked for the thread.  This starts with m.sigmask, which was set
+// either from initSigmask for a newly created thread or by calling
+// msigsave if this is a non-Go thread calling a Go function. It
+// removes all essential signals from the mask, thus causing those
+// signals to not be blocked. Then it sets the thread's signal mask.
+// After this is called the thread can receive signals.
+func minitSignalMask() {
+	nmask := getg().m.sigmask
+	for i := range sigtable {
+		if sigtable[i].flags&_SigUnblock != 0 {
+			sigdelset(&nmask, i)
+		}
+	}
+	sigprocmask(_SIG_SETMASK, &nmask, nil)
+}
+
+// unminitSignals is called from dropm, via unminit, to undo the
+// effect of calling minit on a non-Go thread.
+//go:nosplit
+func unminitSignals() {
+	if getg().m.newSigstack {
+		signalstack(nil, 0)
+	}
+}