if hint.down {
		start, end = addr-heapArenaBytes, addr
		addr -= physPageSize
	} else {
		start, end = addr, addr+heapArenaBytes
	}
	got := sysReserve(unsafe.Pointer(addr), physPageSize)
	ok = (addr == uintptr(got))
	if !ok {
		// We were unable to get the requested reservation.
		// Release what we did get and fail.
		sysFreeOS(got, physPageSize)
	}
	return
}

func GetNextArenaHint() uintptr {

		// We're assuming here we can read at least the page containing the PC.
		// I suppose it is possible that the page is mapped executable but not readable?
		pc := c.sigpc()
		if n > physPageSize-pc%physPageSize {
			n = physPageSize - pc%physPageSize
		}
		print("instruction bytes:")
		b := (*[maxN]byte)(unsafe.Pointer(pc))
		for i := uintptr(0); i < n; i++ {
			print(" ", hex(b[i]))
		}
		println()
	}
	print("\n")

//go:linkname syscall_runtime_envs syscall.runtime_envs
func syscall_runtime_envs() []string { return append([]string{}, envs...) }

//go:linkname syscall_Getpagesize syscall.Getpagesize
func syscall_Getpagesize() int { return int(physPageSize) }

//go:linkname os_runtime_args os.runtime_args
func os_runtime_args() []string { return append([]string{}, argslice...) }

//go:linkname syscall_Exit syscall.Exit
//go:nosplit

	if fd >= 0 {
		read(fd, unsafe.Pointer(&b), int32(len(b)))
		closefd(fd)
	}
	c := b[:]
	for c[0] == ' ' || c[0] == '\t' {
		c = c[1:]
	}
	return uint64(_atoi(c))
}

func osinit() {
	physPageSize = getPageSize()
	initBloc()
	ncpu = getproccount()
	getg().m.procid = getpid()
}

//go:nosplit
func crash() {
	notify(nil)
	*(*int)(nil) = 0
}

//go:nosplit

	if n&(n-1) != 0 {
		throw("stack size not a power of 2")
	}
	if stackDebug >= 1 {
		print("stackalloc ", n, "\n")
	}

	if debug.efence != 0 || stackFromSystem != 0 {
		n = uint32(alignUp(uintptr(n), physPageSize))
		v := sysAlloc(uintptr(n), &memstats.stacks_sys)
		if v == nil {
			throw("out of memory (stackalloc)")
		}
		return stack{uintptr(v), uintptr(v) + uintptr(n)}
	}