SYS_SSTK                 = 70  // { int|sys||sstk(int incr); }
	SYS_VADVISE              = 72  // { int|sys||ovadvise(int anom); }
	SYS_MUNMAP               = 73  // { int|sys||munmap(void *addr, size_t len); }
	SYS_MPROTECT             = 74  // { int|sys||mprotect(void *addr, size_t len, int prot); }
	SYS_MADVISE              = 75  // { int|sys||madvise(void *addr, size_t len, int behav); }

	SYS_SSTK                 = 70  // { int|sys||sstk(int incr); }
	SYS_VADVISE              = 72  // { int|sys||ovadvise(int anom); }
	SYS_MUNMAP               = 73  // { int|sys||munmap(void *addr, size_t len); }
	SYS_MPROTECT             = 74  // { int|sys||mprotect(void *addr, size_t len, int prot); }
	SYS_MADVISE              = 75  // { int|sys||madvise(void *addr, size_t len, int behav); }

	SYS_SSTK                 = 70  // { int|sys||sstk(int incr); }
	SYS_VADVISE              = 72  // { int|sys||ovadvise(int anom); }
	SYS_MUNMAP               = 73  // { int|sys||munmap(void *addr, size_t len); }
	SYS_MPROTECT             = 74  // { int|sys||mprotect(void *addr, size_t len, int prot); }
	SYS_MADVISE              = 75  // { int|sys||madvise(void *addr, size_t len, int behav); }

	SYS_SSTK                 = 70  // { int|sys||sstk(int incr); }
	SYS_VADVISE              = 72  // { int|sys||ovadvise(int anom); }
	SYS_MUNMAP               = 73  // { int|sys||munmap(void *addr, size_t len); }
	SYS_MPROTECT             = 74  // { int|sys||mprotect(void *addr, size_t len, int prot); }
	SYS_MADVISE              = 75  // { int|sys||madvise(void *addr, size_t len, int behav); }

		// madvise will round this to any physical page
		// *covered* by this range, so an unaligned madvise
		// will release more memory than intended.
		throw("unaligned sysUnused")
	}

	advise := atomic.Load(&adviseUnused)
	if debug.madvdontneed != 0 && advise != madviseUnsupported {
		advise = _MADV_DONTNEED
	}
	switch advise {
	case _MADV_FREE:
		if madvise(v, n, _MADV_FREE) == 0 {

	// accounting information about the process to task_info.
	madvise(v, n, _MADV_FREE_REUSABLE)
}

func sysUsedOS(v unsafe.Pointer, n uintptr) {
	// MADV_FREE_REUSE is necessary to keep the kernel's accounting
	// accurate. If called on any memory region that hasn't been
	// MADV_FREE_REUSABLE'd, it's a no-op.
	madvise(v, n, _MADV_FREE_REUSE)
}

func sysHugePageOS(v unsafe.Pointer, n uintptr) {
}

	if err != 0 {
		return nil
	}
	return v
}

func sysUnusedOS(v unsafe.Pointer, n uintptr) {
	if debug.madvdontneed != 0 {
		madvise(v, n, _MADV_DONTNEED)
	} else {
		madvise(v, n, _MADV_FREE)
	}
}

func sysUsedOS(v unsafe.Pointer, n uintptr) {
}

func sysHugePageOS(v unsafe.Pointer, n uintptr) {
}

func sysNoHugePageOS(v unsafe.Pointer, n uintptr) {

//go:cgo_import_dynamic mach_task_self_ mach_task_self_ ""
//go:cgo_import_dynamic mach_timebase_info mach_timebase_info ""
//go:cgo_import_dynamic mach_vm_region_recurse mach_vm_region_recurse ""
//go:cgo_import_dynamic madvise madvise ""
//go:cgo_import_dynamic malloc_num_zones malloc_num_zones ""
//go:cgo_import_dynamic malloc_zones malloc_zones ""
//go:cgo_import_dynamic memcpy memcpy ""
//go:cgo_import_dynamic memset_pattern16 memset_pattern16 ""

//go:cgo_import_dynamic mach_task_self_ mach_task_self_ ""
//go:cgo_import_dynamic mach_timebase_info mach_timebase_info ""
//go:cgo_import_dynamic mach_vm_region_recurse mach_vm_region_recurse ""
//go:cgo_import_dynamic madvise madvise ""
//go:cgo_import_dynamic malloc_num_zones malloc_num_zones ""
//go:cgo_import_dynamic malloc_zones malloc_zones ""
//go:cgo_import_dynamic memcpy memcpy ""
//go:cgo_import_dynamic memset_pattern16 memset_pattern16 ""

//
//go:noescape
func write1(fd uintptr, p unsafe.Pointer, n int32) int32

//go:noescape
func open(name *byte, mode, perm int32) int32

// return value is only set on linux to be used in osinit().
func madvise(addr unsafe.Pointer, n uintptr, flags int32) int32

// exitThread terminates the current thread, writing *wait = freeMStack when
// the stack is safe to reclaim.
//
//go:noescape