src/runtime/os_fuchsia.go - third_party/go - Git at Google

 // Copyright 2016 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package runtime

 import (
 	"runtime/internal/atomic"
 	"syscall/zx"
 	"unsafe"
 )

 type mOS struct{}

 type sigset struct{}

 //go:nosplit
 func getRandomData(r []byte) {
 	zx.RandRead(r)
 }

 //go:nosplit
 func futexsleep(addr *uint32, val uint32, ns int64) {
 	deadline := zx.Sys_deadline_after(zx.Duration(ns))
 	if ns < 0 {
 		deadline = zx.Time(zx.TimensecInfinite)
 	}
 	zx.Sys_futex_wait((*int32)(unsafe.Pointer(addr)), int32(val), zx.HandleInvalid, deadline)
 }

 //go:nosplit
 func futexwakeup(addr *uint32, cnt uint32) {
 	zx.Sys_futex_wake((*int32)(unsafe.Pointer(addr)), cnt)
 }

 //go:nosplit
 func osyield() {
 	zx.Sys_nanosleep(0)
 }

 // cgocallm0 calls a C function on the current stack.
 //
 // It is intended for use inside functions like osinit that run
 // before mstart directly on an OS thread stack.
 //
 // If in doubt, do not use.
 func cgocallm0(fn, arg unsafe.Pointer)

 func osinit() {
 	if _cgo_get_initial_handles != nil {
 		cgocallm0(_cgo_get_initial_handles, unsafe.Pointer(&fdioHandles))
 		for i := 0; i < 3; i = i + 1 {
 			zx.StdioHandles[i] = fdioHandles.stdioClones[i]
 			zx.StdioHandleTypes[i] = int(fdioHandles.stdioCloneTypes[i])
 		}
 		zx.ProcHandle = zx.Handle(fdioHandles.processSelf)
 		zx.VMARRoot = zx.VMAR(fdioHandles.vmarRootSelf)
 	} else {
 		// TODO: implement cgo-less init
 		println("runtime: no fuchsia process handle without cgo yet")
 		exit(2)
 	}

 	ncpu = int32(zx.Sys_system_get_num_cpus())
 	physPageSize = 4096
 }

 func parseRootNS() {
 	if fdioHandles.rootNSNumHandles > 0 {
 		const maxHandleCount = 1 << 20 // arbitrary
 		paths := (*(*[maxHandleCount]*byte)(unsafe.Pointer(fdioHandles.rootNSPaths)))[:fdioHandles.rootNSNumHandles]
 		handles := (*(*[maxHandleCount]zx.Handle)(unsafe.Pointer(fdioHandles.rootNSHandles)))[:fdioHandles.rootNSNumHandles]
 		zx.RootNSMap = make(map[string]zx.Handle)
 		for i, p := range paths {
 			zx.RootNSMap[gostring(p)] = handles[i]
 		}
 	}
 }

 // Filled in by runtime/cgo when linked into binary.

 var (
 	_cgo_get_initial_handles    unsafe.Pointer
 	_cgo_get_thread_self_handle unsafe.Pointer
 )

 //go:nosplit
 func minit() {
 	var h zx.Handle
 	asmcgocall(_cgo_get_thread_self_handle, unsafe.Pointer(&h))
 	atomic.Storeuintptr(&getg().m.thread, uintptr(h))
 }

 //go:nosplit
 func unminit() {
 	// TODO
 }

 func sigpanic() {
 	// TODO
 }

 func mpreinit(mp *m) {
 	// TODO
 }

 //go:nosplit
 func msigsave(mp *m) {
 	// TODO
 }

 //go:nosplit
 func msigrestore(sigmask sigset) {
 	// TODO
 }

 func initsig(preinit bool) {
 	// TODO
 }

 //go:nosplit
 func sigblock() {
 	// TODO
 }

 func sigenable(sig uint32) {
 	// TODO
 }

 func sigdisable(sig uint32) {
 	// TODO
 }

 func sigignore(sig uint32) {
 	// TODO
 }

 func crash() {
 	*(*int32)(nil) = 0
 }

 func threadinit(mp *m)

 var gothreadname = []byte("gothread")

 //go:nowritebarrier
 func newosproc(mp *m) {
 	stk := unsafe.Pointer(mp.g0.stack.hi)
 	p := zx.Handle(0) // TODO: only works due to temporary hack in zircon
 	var h zx.Handle
 	status := zx.Sys_thread_create(p, &gothreadname[0], uint(len(gothreadname)), 0, &h)
 	if status < 0 {
 		println("runtime: newosproc zx.Sys_thread_create failed:", h)
 		exit(2)
 	}

 	mp.thread = uintptr(h)

 	status = zx.Sys_thread_start(h, zx.Vaddr(funcPC(threadinit)), zx.Vaddr(stk), uintptr(unsafe.Pointer(mp)), 0)
 	if status < 0 {
 		println("runtime: newosproc zx.Sys_thread_start failed:", h)
 		exit(2)
 	}
 }

 type zx_proc_args struct {
 	protocol        uint32
 	version         uint32
 	handle_info_off uint32
 	args_off        uint32
 	args_num        uint32
 }

 type zx_proc_info struct {
 	magic         uint32
 	version       uint32
 	next_tls_slot uint32
 	proc_args     *zx_proc_args
 	handle        *zx.Handle
 	handle_info   *uint32
 	handle_count  int32
 	argv          **byte
 	argc          int32
 }

 type zx_tls_root struct {
 	self     *zx_tls_root
 	proc     *zx_proc_info
 	magic    uint32
 	flags    uint16
 	maxslots uint16
 	slots    [8]uintptr // has length maxslots
 }

 func resetcpuprofiler(hz int32) {
 	// TODO
 }

 // fdio_init matches a Go struct of the same name in gcc_fdio.c.
 type fdio_init struct {
 	stdioClones          [3]zx.Handle
 	stdioCloneNumHandles [3]uint32
 	stdioCloneTypes      [3]uint32
 	processSelf          zx.Handle
 	vmarRootSelf         zx.Handle
 	envlen               int32
 	environ              **byte
 	_                    [4]byte
 	rootNSNumHandles     int32
 	rootNSHandles        *zx.Handle
 	rootNSPaths          **byte
 }

 var fdioHandles fdio_init

 func goenvs() {
 	if _cgo_get_initial_handles != nil {
 		const maxEnvSize = 1 << 20 // arbitrary
 		envp := (*(*[maxEnvSize]*byte)(unsafe.Pointer(fdioHandles.environ)))[:fdioHandles.envlen]
 		envs = make([]string, len(envp))
 		for i, e := range envp {
 			envs[i] = gostring(e)
 		}
 		// TODO: find a better place to call this
 		parseRootNS()
 	} else {
 		// TODO: implement cgo-less init
 		println("runtime: no fuchsia process handle without cgo yet")
 		exit(2)
 	}
 }

 const _NSIG = 65 // TODO

 const (
 	ZX_CLOCK_MONOTONIC           = 0
 	ZX_HANDLE_INVALID            = 0
 	ZX_INFO_THREAD               = uint32(10)
 	ZX_OK                        = int32(0)
 	ZX_THREAD_STATE_GENERAL_REGS = uint32(0)
 	ZX_THREAD_STATE_NEW          = uint32(0)
 	ZX_THREAD_SUSPENDED          = uint32(1 << 5)
 	ZX_THREAD_TERMINATED         = uint32(1 << 3)
 	ZX_TIME_INFINITE             = int64(^uint64(1 << 63))
 	ZX_TIMER_SIGNALED            = uint32(1 << 3)
 	ZX_TIMER_SLACK_EARLY         = 1
 )

 //go:nosplit
 func nanotime() int64 {
 	return int64(zx.Sys_clock_get_monotonic())
 }

 //go:linkname time_now time.now
 //go:nosplit
 func time_now() (sec int64, nsec int32, mono int64) {
 	const ZX_CLOCK_UTC = 1
 	var x zx.Time
 	zx.Sys_clock_get(ZX_CLOCK_UTC, &x)
 	return int64(x / 1e9), int32(x % 1e9), nanotime()
 }

 func unixnanotime() int64 {
 	return nanotime()
 }

 // #define LOGBUF_MAX (ZX_LOG_RECORD_MAX - sizeof(zx_log_record_t))
 const logBufMax = 224

 var logger zx.Handle
 var logBufferArray [logBufMax]byte
 var logBufferN int

 //go:nosplit
 func write(fd uintptr, buf unsafe.Pointer, n int32) int32 {
 	if fd != 1 && fd != 2 {
 		panic("runtime.write(): can not write to non-log fd")
 	}

 	// This initialization mechanism is not thread-safe, but if the only calls to 'write' with
 	// these file descriptors come from print, they will already be serialized by a lock in
 	// print's implementation.
 	if logger <= 0 {
 		zx.Sys_debuglog_create(0, 0, &logger)
 		logBufferN = 0
 	}
 	// Ideally this should panic, but that would go down "blind", which is arguably worse.
 	if logger <= 0 {
 		return -1
 	}

 	for i := int32(0); i < n; i++ {
 		c := *(*byte)(unsafe.Pointer(uintptr(buf) + uintptr(i)))

 		if c == '\n' {
 			zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
 			logBufferN = 0
 			continue
 		}

 		if c < ' ' {
 			continue
 		}

 		logBufferArray[logBufferN] = c
 		logBufferN++

 		if logBufferN == len(logBufferArray) {
 			zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
 			logBufferN = 0
 		}
 	}

 	return n
 }

 //go:nosplit
 func exit(code int32) {
 	zx.Sys_process_exit(int64(code))
 }

 //go:nosplit
 func usleep(usec uint32) {
 	zx.Sys_nanosleep(zx.Sys_deadline_after(zx.Duration(usec * 1000)))
 }

 func signame(sig uint32) string {
 	return "unknown_sig" // TODO
 }

 // zircon_mktls
 //go:nosplit
 func zircon_mktls() {
 	// TODO
 }

 //go:nosplit
 func zircon_settls(val uintptr) {
 	// TODO: should call zx_set_object_property with property ZX_PROP_REGISTER_FS in amd64 or
 	// ZX_PROP_REGISTER_CP15 on arm.
 }

 //go:linkname os_sigpipe os.sigpipe
 func os_sigpipe() {
 	// TODO
 }

 // gsignalStack is unused on fuchsia
 type gsignalStack struct{}

 const (
 	profStkSize = uintptr(1 << 16)
 )

 var (
 	profTimer   uint32 // timer handle
 	profThread  uint32 // thread handle
 	profHz      = ZX_TIME_INFINITE
 	profName    = []byte("profiler")
 	profStk     unsafe.Pointer
 	profStkFail = []byte("runtime: failed to allocate stack for the new OS thread\n")
 )

 type zxCpuSet struct {
 	mask [16]uint32
 }

 type zxInfoThread struct {
 	state                 uint32
 	waitExceptionPortType uint32
 	affinityMask          zxCpuSet
 }

 //go:noescape
 //go:nosplit
 func profiler_object_wait_one(handle uint32, signals uint32, deadline int64, observed *uint32) int32

 func profilem(mp *m, thread uint32) {
 	// Ignore nascent threads.
 	var observed uint32
 	var info zxInfoThread
 	var actualSize uint64
 	var availSize uint64
 	if status := vdsoCall_zx_object_get_info(thread, ZX_INFO_THREAD, unsafe.Pointer(&info), uint(unsafe.Sizeof(info)), unsafe.Pointer(&actualSize), unsafe.Pointer(&availSize)); status != ZX_OK {
 		return
 	}
 	if info.state == ZX_THREAD_STATE_NEW {
 		return
 	}

 	// Wait for the thread to be suspended.
 	if status := profiler_object_wait_one(thread, ZX_THREAD_SUSPENDED|ZX_THREAD_TERMINATED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
 		return
 	}

 	// Ignore threads that were terminated as a result of suspension.
 	if observed&ZX_THREAD_TERMINATED == ZX_THREAD_TERMINATED {
 		return
 	}

 	var r generalRegs
 	if status := vdsoCall_zx_thread_read_state(thread, ZX_THREAD_STATE_GENERAL_REGS, unsafe.Pointer(&r), uint(unsafe.Sizeof(r))); status != ZX_OK {
 		return
 	}

 	if mp.curg != nil {
 		sigprof(r.rPC(), r.rSP(), r.rLR(), mp.curg, mp)
 	} else {
 		sigprofNonGoPC(r.rPC())
 	}
 }

 // profileLoop is called when pprof CPU tracing is enabled. It runs without a p, hence nowritebarrierrec.
 //
 //go:nosplit
 //go:nowritebarrierrec
 func profileLoop() {
 	me := getg().m
 	for {
 		var observed uint32
 		if status := profiler_object_wait_one(profTimer, ZX_TIMER_SIGNALED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
 			continue
 		}

 		// Scan over all threads and suspend them, then trace. Ideally, we'd scan over
 		// all of them and give them a chance to suspend before this, but I don't want
 		// to deal with allocation here.
 		first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
 		for mp := first; mp != nil; mp = mp.alllink {
 			thread := uint32(atomic.Loaduintptr(&mp.thread))
 			// Do not profile threads blocked on Notes (this includes idle worker threads, idle timer thread,
 			// idle heap scavenger, etc.). Do not profile this thread.
 			if thread == ZX_HANDLE_INVALID || mp.profilehz == 0 || mp.blocked || mp == me {
 				continue
 			}

 			var token uint32
 			if status := vdsoCall_zx_task_suspend_token(thread, unsafe.Pointer(&token)); status == ZX_OK {
 				profilem(mp, thread)
 			}
 			vdsoCall_zx_handle_close(token)

 		}

 		due := vdsoCall_zx_deadline_after(profHz)
 		if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
 			// TODO: what do?
 			return
 		}
 	}
 }

 // profileloop is defined in sys_fuchsia_{amd,arm}64.s
 func profileloop()

 func setProcessCPUProfiler(hz int32) {
 	// This function is entered in the critical section guarded by
 	// prof.signalLock in proc.go and is thus safe to assume the profiler's
 	// timer is created atomically.
 	if profTimer == ZX_HANDLE_INVALID {
 		if status := vdsoCall_zx_timer_create(ZX_TIMER_SLACK_EARLY, ZX_CLOCK_MONOTONIC, unsafe.Pointer(&profTimer)); status != ZX_OK {
 			// TODO: what do?
 			return
 		}

 		newm(profileLoop, nil)
 	}
 }

 func setThreadCPUProfiler(hz int32) {
 	// Don't do anything if we don't have a timer yet.
 	if profTimer == ZX_HANDLE_INVALID {
 		return
 	}

 	atomic.Store((*uint32)(unsafe.Pointer(&getg().m.profilehz)), uint32(hz))

 	if hz > 0 {
 		ns := int64(int64(1000000000) / int64(hz))
 		// Bound tracing frequency to microseconds. This is likely
 		// already well above the granularity traces can actually
 		// provide.
 		if ns < 1000 {
 			ns = 1000
 		}

 		profHz = ns
 		due := vdsoCall_zx_deadline_after(ns)
 		if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
 			// TODO: what do?
 			return
 		}
 	} else {
 		if status := vdsoCall_zx_timer_cancel(profTimer); status != ZX_OK {
 			return
 		}
 	}
 }

 func exitThread(wait *uint32) {}

 //go:nosplit
 //go:nowritebarrierrec
 func clearSignalHandlers() {}
	// Copyright 2016 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package runtime

	import (
	"runtime/internal/atomic"
	"syscall/zx"
	"unsafe"
	)

	type mOS struct{}

	type sigset struct{}

	//go:nosplit
	func getRandomData(r []byte) {
	zx.RandRead(r)
	}

	//go:nosplit
	func futexsleep(addr *uint32, val uint32, ns int64) {
	deadline := zx.Sys_deadline_after(zx.Duration(ns))
	if ns < 0 {
	deadline = zx.Time(zx.TimensecInfinite)
	}
	zx.Sys_futex_wait((*int32)(unsafe.Pointer(addr)), int32(val), zx.HandleInvalid, deadline)
	}

	//go:nosplit
	func futexwakeup(addr *uint32, cnt uint32) {
	zx.Sys_futex_wake((*int32)(unsafe.Pointer(addr)), cnt)
	}

	//go:nosplit
	func osyield() {
	zx.Sys_nanosleep(0)
	}

	// cgocallm0 calls a C function on the current stack.
	//
	// It is intended for use inside functions like osinit that run
	// before mstart directly on an OS thread stack.
	//
	// If in doubt, do not use.
	func cgocallm0(fn, arg unsafe.Pointer)

	func osinit() {
	if _cgo_get_initial_handles != nil {
	cgocallm0(_cgo_get_initial_handles, unsafe.Pointer(&fdioHandles))
	for i := 0; i < 3; i = i + 1 {
	zx.StdioHandles[i] = fdioHandles.stdioClones[i]
	zx.StdioHandleTypes[i] = int(fdioHandles.stdioCloneTypes[i])
	}
	zx.ProcHandle = zx.Handle(fdioHandles.processSelf)
	zx.VMARRoot = zx.VMAR(fdioHandles.vmarRootSelf)
	} else {
	// TODO: implement cgo-less init
	println("runtime: no fuchsia process handle without cgo yet")
	exit(2)
	}

	ncpu = int32(zx.Sys_system_get_num_cpus())
	physPageSize = 4096
	}

	func parseRootNS() {
	if fdioHandles.rootNSNumHandles > 0 {
	const maxHandleCount = 1 << 20 // arbitrary
	paths := (([maxHandleCount]*byte)(unsafe.Pointer(fdioHandles.rootNSPaths)))[:fdioHandles.rootNSNumHandles]
	handles := (([maxHandleCount]zx.Handle)(unsafe.Pointer(fdioHandles.rootNSHandles)))[:fdioHandles.rootNSNumHandles]
	zx.RootNSMap = make(map[string]zx.Handle)
	for i, p := range paths {
	zx.RootNSMap[gostring(p)] = handles[i]
	}
	}
	}

	// Filled in by runtime/cgo when linked into binary.

	var (
	_cgo_get_initial_handles unsafe.Pointer
	_cgo_get_thread_self_handle unsafe.Pointer
	)

	//go:nosplit
	func minit() {
	var h zx.Handle
	asmcgocall(_cgo_get_thread_self_handle, unsafe.Pointer(&h))
	atomic.Storeuintptr(&getg().m.thread, uintptr(h))
	}

	//go:nosplit
	func unminit() {
	// TODO
	}

	func sigpanic() {
	// TODO
	}

	func mpreinit(mp *m) {
	// TODO
	}

	//go:nosplit
	func msigsave(mp *m) {
	// TODO
	}

	//go:nosplit
	func msigrestore(sigmask sigset) {
	// TODO
	}

	func initsig(preinit bool) {
	// TODO
	}

	//go:nosplit
	func sigblock() {
	// TODO
	}

	func sigenable(sig uint32) {
	// TODO
	}

	func sigdisable(sig uint32) {
	// TODO
	}

	func sigignore(sig uint32) {
	// TODO
	}

	func crash() {
	(int32)(nil) = 0
	}

	func threadinit(mp *m)

	var gothreadname = []byte("gothread")

	//go:nowritebarrier
	func newosproc(mp *m) {
	stk := unsafe.Pointer(mp.g0.stack.hi)
	p := zx.Handle(0) // TODO: only works due to temporary hack in zircon
	var h zx.Handle
	status := zx.Sys_thread_create(p, &gothreadname[0], uint(len(gothreadname)), 0, &h)
	if status < 0 {
	println("runtime: newosproc zx.Sys_thread_create failed:", h)
	exit(2)
	}

	mp.thread = uintptr(h)

	status = zx.Sys_thread_start(h, zx.Vaddr(funcPC(threadinit)), zx.Vaddr(stk), uintptr(unsafe.Pointer(mp)), 0)
	if status < 0 {
	println("runtime: newosproc zx.Sys_thread_start failed:", h)
	exit(2)
	}
	}

	type zx_proc_args struct {
	protocol uint32
	version uint32
	handle_info_off uint32
	args_off uint32
	args_num uint32
	}

	type zx_proc_info struct {
	magic uint32
	version uint32
	next_tls_slot uint32
	proc_args *zx_proc_args
	handle *zx.Handle
	handle_info *uint32
	handle_count int32
	argv **byte
	argc int32
	}

	type zx_tls_root struct {
	self *zx_tls_root
	proc *zx_proc_info
	magic uint32
	flags uint16
	maxslots uint16
	slots [8]uintptr // has length maxslots
	}

	func resetcpuprofiler(hz int32) {
	// TODO
	}

	// fdio_init matches a Go struct of the same name in gcc_fdio.c.
	type fdio_init struct {
	stdioClones [3]zx.Handle
	stdioCloneNumHandles [3]uint32
	stdioCloneTypes [3]uint32
	processSelf zx.Handle
	vmarRootSelf zx.Handle
	envlen int32
	environ **byte
	_ [4]byte
	rootNSNumHandles int32
	rootNSHandles *zx.Handle
	rootNSPaths **byte
	}

	var fdioHandles fdio_init

	func goenvs() {
	if _cgo_get_initial_handles != nil {
	const maxEnvSize = 1 << 20 // arbitrary
	envp := (([maxEnvSize]*byte)(unsafe.Pointer(fdioHandles.environ)))[:fdioHandles.envlen]
	envs = make([]string, len(envp))
	for i, e := range envp {
	envs[i] = gostring(e)
	}
	// TODO: find a better place to call this
	parseRootNS()
	} else {
	// TODO: implement cgo-less init
	println("runtime: no fuchsia process handle without cgo yet")
	exit(2)
	}
	}

	const _NSIG = 65 // TODO

	const (
	ZX_CLOCK_MONOTONIC = 0
	ZX_HANDLE_INVALID = 0
	ZX_INFO_THREAD = uint32(10)
	ZX_OK = int32(0)
	ZX_THREAD_STATE_GENERAL_REGS = uint32(0)
	ZX_THREAD_STATE_NEW = uint32(0)
	ZX_THREAD_SUSPENDED = uint32(1 << 5)
	ZX_THREAD_TERMINATED = uint32(1 << 3)
	ZX_TIME_INFINITE = int64(^uint64(1 << 63))
	ZX_TIMER_SIGNALED = uint32(1 << 3)
	ZX_TIMER_SLACK_EARLY = 1
	)

	//go:nosplit
	func nanotime() int64 {
	return int64(zx.Sys_clock_get_monotonic())
	}

	//go:linkname time_now time.now
	//go:nosplit
	func time_now() (sec int64, nsec int32, mono int64) {
	const ZX_CLOCK_UTC = 1
	var x zx.Time
	zx.Sys_clock_get(ZX_CLOCK_UTC, &x)
	return int64(x / 1e9), int32(x % 1e9), nanotime()
	}

	func unixnanotime() int64 {
	return nanotime()
	}

	// #define LOGBUF_MAX (ZX_LOG_RECORD_MAX - sizeof(zx_log_record_t))
	const logBufMax = 224

	var logger zx.Handle
	var logBufferArray [logBufMax]byte
	var logBufferN int

	//go:nosplit
	func write(fd uintptr, buf unsafe.Pointer, n int32) int32 {
	if fd != 1 && fd != 2 {
	panic("runtime.write(): can not write to non-log fd")
	}

	// This initialization mechanism is not thread-safe, but if the only calls to 'write' with
	// these file descriptors come from print, they will already be serialized by a lock in
	// print's implementation.
	if logger <= 0 {
	zx.Sys_debuglog_create(0, 0, &logger)
	logBufferN = 0
	}
	// Ideally this should panic, but that would go down "blind", which is arguably worse.
	if logger <= 0 {
	return -1
	}

	for i := int32(0); i < n; i++ {
	c := (byte)(unsafe.Pointer(uintptr(buf) + uintptr(i)))

	if c == '\n' {
	zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
	logBufferN = 0
	continue
	}

	if c < ' ' {
	continue
	}

	logBufferArray[logBufferN] = c
	logBufferN++

	if logBufferN == len(logBufferArray) {
	zx.Sys_debuglog_write(logger, 0, unsafe.Pointer(&logBufferArray[0]), uint(logBufferN))
	logBufferN = 0
	}
	}

	return n
	}

	//go:nosplit
	func exit(code int32) {
	zx.Sys_process_exit(int64(code))
	}

	//go:nosplit
	func usleep(usec uint32) {
	zx.Sys_nanosleep(zx.Sys_deadline_after(zx.Duration(usec * 1000)))
	}

	func signame(sig uint32) string {
	return "unknown_sig" // TODO
	}

	// zircon_mktls
	//go:nosplit
	func zircon_mktls() {
	// TODO
	}

	//go:nosplit
	func zircon_settls(val uintptr) {
	// TODO: should call zx_set_object_property with property ZX_PROP_REGISTER_FS in amd64 or
	// ZX_PROP_REGISTER_CP15 on arm.
	}

	//go:linkname os_sigpipe os.sigpipe
	func os_sigpipe() {
	// TODO
	}

	// gsignalStack is unused on fuchsia
	type gsignalStack struct{}

	const (
	profStkSize = uintptr(1 << 16)
	)

	var (
	profTimer uint32 // timer handle
	profThread uint32 // thread handle
	profHz = ZX_TIME_INFINITE
	profName = []byte("profiler")
	profStk unsafe.Pointer
	profStkFail = []byte("runtime: failed to allocate stack for the new OS thread\n")
	)

	type zxCpuSet struct {
	mask [16]uint32
	}

	type zxInfoThread struct {
	state uint32
	waitExceptionPortType uint32
	affinityMask zxCpuSet
	}

	//go:noescape
	//go:nosplit
	func profiler_object_wait_one(handle uint32, signals uint32, deadline int64, observed *uint32) int32

	func profilem(mp *m, thread uint32) {
	// Ignore nascent threads.
	var observed uint32
	var info zxInfoThread
	var actualSize uint64
	var availSize uint64
	if status := vdsoCall_zx_object_get_info(thread, ZX_INFO_THREAD, unsafe.Pointer(&info), uint(unsafe.Sizeof(info)), unsafe.Pointer(&actualSize), unsafe.Pointer(&availSize)); status != ZX_OK {
	return
	}
	if info.state == ZX_THREAD_STATE_NEW {
	return
	}

	// Wait for the thread to be suspended.
	if status := profiler_object_wait_one(thread, ZX_THREAD_SUSPENDED\|ZX_THREAD_TERMINATED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
	return
	}

	// Ignore threads that were terminated as a result of suspension.
	if observed&ZX_THREAD_TERMINATED == ZX_THREAD_TERMINATED {
	return
	}

	var r generalRegs
	if status := vdsoCall_zx_thread_read_state(thread, ZX_THREAD_STATE_GENERAL_REGS, unsafe.Pointer(&r), uint(unsafe.Sizeof(r))); status != ZX_OK {
	return
	}

	if mp.curg != nil {
	sigprof(r.rPC(), r.rSP(), r.rLR(), mp.curg, mp)
	} else {
	sigprofNonGoPC(r.rPC())
	}
	}

	// profileLoop is called when pprof CPU tracing is enabled. It runs without a p, hence nowritebarrierrec.
	//
	//go:nosplit
	//go:nowritebarrierrec
	func profileLoop() {
	me := getg().m
	for {
	var observed uint32
	if status := profiler_object_wait_one(profTimer, ZX_TIMER_SIGNALED, ZX_TIME_INFINITE, &observed); status != ZX_OK {
	continue
	}

	// Scan over all threads and suspend them, then trace. Ideally, we'd scan over
	// all of them and give them a chance to suspend before this, but I don't want
	// to deal with allocation here.
	first := (*m)(atomic.Loadp(unsafe.Pointer(&allm)))
	for mp := first; mp != nil; mp = mp.alllink {
	thread := uint32(atomic.Loaduintptr(&mp.thread))
	// Do not profile threads blocked on Notes (this includes idle worker threads, idle timer thread,
	// idle heap scavenger, etc.). Do not profile this thread.
	if thread == ZX_HANDLE_INVALID \|\| mp.profilehz == 0 \|\| mp.blocked \|\| mp == me {
	continue
	}

	var token uint32
	if status := vdsoCall_zx_task_suspend_token(thread, unsafe.Pointer(&token)); status == ZX_OK {
	profilem(mp, thread)
	}
	vdsoCall_zx_handle_close(token)

	}

	due := vdsoCall_zx_deadline_after(profHz)
	if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
	// TODO: what do?
	return
	}
	}
	}

	// profileloop is defined in sys_fuchsia_{amd,arm}64.s
	func profileloop()

	func setProcessCPUProfiler(hz int32) {
	// This function is entered in the critical section guarded by
	// prof.signalLock in proc.go and is thus safe to assume the profiler's
	// timer is created atomically.
	if profTimer == ZX_HANDLE_INVALID {
	if status := vdsoCall_zx_timer_create(ZX_TIMER_SLACK_EARLY, ZX_CLOCK_MONOTONIC, unsafe.Pointer(&profTimer)); status != ZX_OK {
	// TODO: what do?
	return
	}

	newm(profileLoop, nil)
	}
	}

	func setThreadCPUProfiler(hz int32) {
	// Don't do anything if we don't have a timer yet.
	if profTimer == ZX_HANDLE_INVALID {
	return
	}

	atomic.Store((*uint32)(unsafe.Pointer(&getg().m.profilehz)), uint32(hz))

	if hz > 0 {
	ns := int64(int64(1000000000) / int64(hz))
	// Bound tracing frequency to microseconds. This is likely
	// already well above the granularity traces can actually
	// provide.
	if ns < 1000 {
	ns = 1000
	}

	profHz = ns
	due := vdsoCall_zx_deadline_after(ns)
	if status := vdsoCall_zx_timer_set(profTimer, due, ZX_TIMER_SLACK_EARLY); status != ZX_OK {
	// TODO: what do?
	return
	}
	} else {
	if status := vdsoCall_zx_timer_cancel(profTimer); status != ZX_OK {
	return
	}
	}
	}

	func exitThread(wait *uint32) {}

	//go:nosplit
	//go:nowritebarrierrec
	func clearSignalHandlers() {}