MOVD	R3, R0				// arg = g
	MOVD	$0, -16(RSP)			// dummy LR
	SUB	$16, RSP
	MOVD	0(R26), R4			// code pointer
	BL	(R4)
	B	runtime·badmcall2(SB)

// systemstack_switch is a dummy routine that systemstack leaves at the bottom
// of the G stack. We need to distinguish the routine that
// lives at the bottom of the G stack from the one that lives
// at the top of the system stack because the one at the top of

	if ret >= 0 {
		return
	}

	// I don't know that futex wakeup can return
	// EAGAIN or EINTR, but if it does, it would be
	// safe to loop and call futex again.
	systemstack(func() {
		print("futexwakeup addr=", addr, " returned ", ret, "\n")
	})

	*(*int32)(unsafe.Pointer(uintptr(0x1006))) = 0x1006
}

func getproccount() int32 {

		fallthrough // because of //go:cgo_unsafe_args
	default:
		verb := text
		if i := strings.Index(text, " "); i >= 0 {
			verb = verb[:i]
		}
		flag := pragmaFlag(verb)
		const runtimePragmas = ir.Systemstack | ir.Nowritebarrier | ir.Nowritebarrierrec | ir.Yeswritebarrierrec
		if !base.Flag.CompilingRuntime && flag&runtimePragmas != 0 {
			p.error(syntax.Error{Pos: pos, Msg: fmt.Sprintf("//%s only allowed in runtime", verb)})
		}

			case abi.FuncID_systemstack:
				// systemstack returns normally, so just follow the
				// stack transition.
				if usesLR && funcspdelta(f, frame.pc) == 0 {
					// We're at the function prologue and the stack
					// switch hasn't happened, or epilogue where we're
					// about to return. Just unwind normally.
					// Do this only on LR machines because on x86
					// systemstack doesn't have an SP delta (the CALL

System and signal stacks cannot grow, but are large enough to execute
runtime and cgo code (8K in a pure Go binary; system-allocated in a
cgo binary).

Runtime code often temporarily switches to the system stack using
`systemstack`, `mcall`, or `asmcgocall` to perform tasks that must not
be preempted, that must not grow the user stack, or that switch user
goroutines. Code running on the system stack is implicitly

	// peak stack depths and we risk blowing the system stack.
	// This is safe because the world is stopped, so we don't
	// need to worry about anyone shrinking and therefore moving
	// our stack.
	var m MemStats
	systemstack(func() {
		// Call readmemstats_m here instead of deeper in
		// writeheapdump_m because we might blow the system stack
		// otherwise.
		readmemstats_m(&m)
		writeheapdump_m(fd, &m)
	})

	startTheWorld(stw)

	// Don't do any operations that lock the heap on the G stack.
	// It might trigger stack growth, and the stack growth code needs
	// to be able to allocate heap.
	var s *mspan
	systemstack(func() {
		// To prevent excessive heap growth, before allocating n pages
		// we need to sweep and reclaim at least n pages.
		if !isSweepDone() {
			h.reclaim(npages)
		}

	a.gcMiscSys = memstats.gcMiscSys.load()
	a.otherSys = memstats.other_sys.load()
	a.heapGoal = gcController.heapGoal()
	a.gcCyclesDone = uint64(memstats.numgc)
	a.gcCyclesForced = uint64(memstats.numforcedgc)

	systemstack(func() {
		lock(&mheap_.lock)
		a.mSpanSys = memstats.mspan_sys.load()
		a.mSpanInUse = uint64(mheap_.spanalloc.inuse)
		a.mCacheSys = memstats.mcache_sys.load()
		a.mCacheInUse = uint64(mheap_.cachealloc.inuse)

		// in blockTimerChan, but timerHeaped not being set means
		// it hasn't run t.maybeAdd yet; in that case, running the
		// timer ourselves now is fine.)
		if now := nanotime(); t.when <= now {
			systemstack(func() {
				t.unlockAndRun(now) // resets t.when
			})
			t.lock()
		}
	}
}

// stop stops the timer t. It may be on some other P, so we can't

	if mp.mallocing != 0 {
		throw("malloc deadlock")
	}
	if mp.gsignal == getg() {
		throw("malloc during signal")
	}
	mp.mallocing = 1

	// Allocate a new user arena.
	var span *mspan
	systemstack(func() {
		span = mheap_.allocUserArenaChunk()
	})
	if span == nil {
		throw("out of memory")
	}
	x := unsafe.Pointer(span.base())

	// Allocate black during GC.