func osStackAlloc(s *mspan) {
	osStackRemap(s, _MAP_STACK)
}

func osStackFree(s *mspan) {
	// Undo MAP_STACK.
	osStackRemap(s, 0)
}

func osStackRemap(s *mspan, flags int32) {
	a, err := mmap(unsafe.Pointer(s.base()), s.npages*pageSize, _PROT_READ|_PROT_WRITE, _MAP_PRIVATE|_MAP_ANON|_MAP_FIXED|flags, -1, 0)
	if err != 0 || uintptr(a) != s.base() {

golang.org/x/telemetry/counter/countertest
golang.org/x/telemetry/internal/config
golang.org/x/telemetry/internal/configstore
golang.org/x/telemetry/internal/counter
golang.org/x/telemetry/internal/crashmonitor
golang.org/x/telemetry/internal/mmap
golang.org/x/telemetry/internal/telemetry
golang.org/x/telemetry/internal/upload
# golang.org/x/term v0.20.0
## explicit; go 1.18
golang.org/x/term
# golang.org/x/text v0.16.0
## explicit; go 1.18

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

type sigset_t struct {
	X__val [16]uint64
}

// mmap varies by architecture; see syscall_linux_*.go.
//sys	munmap(addr uintptr, length uintptr) (err error)

var mapper = &mmapper{
	active: make(map[*byte][]byte),
	mmap:   mmap,
	munmap: munmap,
}

func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
	return mapper.Mmap(fd, offset, length, prot, flags)
}

func setTimeval(sec, usec int64) Timeval {
	return Timeval{Sec: int32(sec), Usec: int32(usec)}
}

//sys	mmap2(addr uintptr, length uintptr, prot int, flags int, fd int, pageOffset uintptr) (xaddr uintptr, err error)

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

func GetMmap(c Cache, id ActionID) ([]byte, Entry, error) {
	entry, err := c.Get(id)
	if err != nil {
		return nil, entry, err
	}
	md, err := mmap.Mmap(c.OutputFile(entry.OutputID))
	if err != nil {
		return nil, Entry{}, err
	}
	if int64(len(md.Data)) != entry.Size {
		return nil, Entry{}, &entryNotFoundError{Err: errors.New("file incomplete")}
	}

	if err != nil {
		return err
	}
	_, _, e := Syscall(SYS_STATFS64, uintptr(unsafe.Pointer(pathp)), unsafe.Sizeof(*buf), uintptr(unsafe.Pointer(buf)))
	if e != 0 {
		err = e
	}
	return
}

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

	if e != 0 {
		err = e
	}
	return
}

//sys	mmap2(addr uintptr, length uintptr, prot int, flags int, fd int, pageOffset uintptr) (xaddr uintptr, err error)

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

	if err != nil {
		return err
	}
	_, _, e := Syscall(SYS_STATFS64, uintptr(unsafe.Pointer(pathp)), unsafe.Sizeof(*buf), uintptr(unsafe.Pointer(buf)))
	if e != 0 {
		err = e
	}
	return
}

func mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) {
	page := uintptr(offset / 4096)
	if offset != int64(page)*4096 {
		return 0, EINVAL
	}

//sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
//sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
//sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)

type sigset_t struct {
	X__val [16]uint64
}