#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();
	}
}

static void restoreSignalStack(void) {

			exit(EXIT_FAILURE);
		}
	}

	// We should still be on the same signal stack.
	if (sigaltstack(NULL, &nss) < 0) {
		die("sigaltstack check");
	}
	if ((nss.ss_flags & SS_DISABLE) != 0) {
		fprintf(stderr, "sigaltstack disabled on return from Go\n");
		ok = 0;
	} else if (nss.ss_sp != ss.ss_sp) {
		fprintf(stderr, "sigaltstack changed on return from Go\n");
		ok = 0;
	}

	return NULL;
}

	if (base == MAP_FAILED) {
		perror("mmap failed");
		abort();
	}
	stack_t st = {}, ost = {};
	st.ss_sp = (char*)base;
	st.ss_flags = 0;
	st.ss_size = CSIGSTKSZ;
	if (sigaltstack(&st, &ost) < 0) {
		perror("sigaltstack failed");
		abort();
	}

	// Call Go.
	SigStackCallback();

	// Disable signal stack and protect it so we can detect reuse.
	if (ost.ss_flags & SS_DISABLE) {

	// new signal stack here, to avoid having two Go threads using
	// 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.
//

	// in minit, but it's a simple change that keeps NetBSD
	// working like other OS's. At this point all signals are
	// blocked, so there is no race.
	memset(&ss, 0, sizeof ss);
	ss.ss_flags = SS_DISABLE;
	sigaltstack(&ss, nil);

	crosscall1(ts.fn, setg_gcc, ts.g);
	return nil;

	gp.stackguard0 = st.stackguard0
	gp.stackguard1 = st.stackguard1
	gp.stktopsp = st.stktopsp
}

// signalstack sets the current thread's alternate signal stack to s.
//
//go:nosplit
func signalstack(s *stack) {
	st := stackt{ss_size: s.hi - s.lo}
	setSignalstackSP(&st, s.lo)
	sigaltstack(&st, nil)
}

// setsigsegv is used on darwin/arm64 to fake a segmentation fault.
//

	asmcgocall_no_g(unsafe.Pointer(abi.FuncPCABI0(sigprocmask_trampoline)), unsafe.Pointer(&how))
	KeepAlive(new)
	KeepAlive(old)
}
func sigprocmask_trampoline()

//go:nosplit
//go:cgo_unsafe_args
func sigaltstack(new *stackt, old *stackt) {
	libcCall(unsafe.Pointer(abi.FuncPCABI0(sigaltstack_trampoline)), unsafe.Pointer(&new))
	KeepAlive(new)
	KeepAlive(old)
}
func sigaltstack_trampoline()

// munmap calls the munmap system call. It is implemented in assembly.
func munmap(addr unsafe.Pointer, n uintptr)

func nanotime1() int64

//go:noescape
func sigaltstack(new, old *stackt)

func fcntl(fd, cmd, arg int32) (ret int32, errno int32)

func walltime() (sec int64, nsec int32)

	sigaction1(sig, uintptr(unsafe.Pointer(new)), uintptr(unsafe.Pointer(old)))
}

//go:nosplit
func sigaltstack(new, old *stackt) {
	r, err := syscall2(&libc_sigaltstack, uintptr(unsafe.Pointer(new)), uintptr(unsafe.Pointer(old)))
	if int32(r) == -1 {
		println("syscall sigaltstack failed: ", hex(err))
		throw("syscall sigaltstack")
	}
}

//go:nosplit
//go:linkname internal_cpu_getsystemcfg internal/cpu.getsystemcfg

	KeepAlive(old)
}
func sigprocmask_trampoline()

//go:nosplit
//go:cgo_unsafe_args
func sigaltstack(new *stackt, old *stackt) {
	if new != nil && new.ss_flags&_SS_DISABLE != 0 && new.ss_size == 0 {
		// Despite the fact that Darwin's sigaltstack man page says it ignores the size
		// when SS_DISABLE is set, it doesn't. sigaltstack returns ENOMEM
		// if we don't give it a reasonable size.