#define CSIGSTKSZ 0x4000
#else
#define CSIGSTKSZ SIGSTKSZ
#endif

static stack_t oss;
static char signalStack[CSIGSTKSZ];

static void changeSignalStack(void) {
	stack_t ss;
	memset(&ss, 0, sizeof ss);
	ss.ss_sp = signalStack;
	ss.ss_flags = 0;
	ss.ss_size = CSIGSTKSZ;
	if (sigaltstack(&ss, &oss) < 0) {
		perror("sigaltstack");
		abort();
	}
}

	var gsignalStack gsignalStack
	setStack := adjustSignalStack(sig, gp.m, &gsignalStack)
	if setStack {
		gp.m.gsignal.stktopsp = getcallersp()
	}

	if gp.stackguard0 == stackFork {
		signalDuringFork(sig)
	}

	c.fixsigcode(sig)
	sighandler(sig, info, ctx, gp)
	setg(gp)
	if setStack {
		restoreGsignalStack(&gsignalStack)
	}
}

	// the same signal stack. This breaks the case of a thread
	// created in C that calls sigaltstack and then calls a Go
	// function, because we will lose track of the C code's
	// sigaltstack, but it's the best we can do.
	signalstack(&gp.m.gsignal.stack)
	gp.m.newSigstack = true

	minitSignalMask()
}

// Called from dropm to undo the effect of an minit.
//
//go:nosplit
func unminit() {
	unminitSignals()

	return
}

//go:nosplit
func cputicks() int64 {
	// runtime·nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
	return nanotime()
}

// gsignalStack is unused on js.
type gsignalStack struct{}

const preemptMSupported = false

func preemptM(mp *m) {
	// No threads, so nothing to do.
}

}

func setProcessCPUProfiler(hz int32) {
}

func setThreadCPUProfiler(hz int32) {
	// TODO: Enable profiling interrupts.
	getg().m.profilehz = hz
}

// gsignalStack is unused on Plan 9.

	}
	const FAIL_FAST_GENERATE_EXCEPTION_ADDRESS = 0x1
	stdcall3(_RaiseFailFastException, uintptr(unsafe.Pointer(info)), uintptr(unsafe.Pointer(r)), FAIL_FAST_GENERATE_EXCEPTION_ADDRESS)
}

// gsignalStack is unused on Windows.

// dropm is called when a cgo callback has called needm but is now
// done with the callback and returning back into the non-Go thread.
//
// The main expense here is the call to signalstack to release the
// m's signal stack, and then the call to needm on the next callback
// from this thread. It is tempting to try to save the m for next time,
// which would eliminate both these costs, but there might not be

	// Fields not known to debuggers.
	procid        uint64            // for debuggers, but offset not hard-coded
	gsignal       *g                // signal-handling g
	goSigStack    gsignalStack      // Go-allocated signal handling stack
	sigmask       sigset            // storage for saved signal mask
	tls           [tlsSlots]uintptr // thread-local storage (for x86 extern register)
	mstartfn      func()