message: Only check futex pointer in futex_wait and not in futex_wake.
  futex_wake doesn't access the futex itself, so should accept pointers to
  memory that's no longer there.
diff: @@ -10,14 +10,12 @@ pub fn futex<'tcx>(
  if args.len() < 4 {
  throw_ub_format!("incorrect number of arguments for futex syscall: got {}, expected at least 4", args.len());
  }
  - let addr = this.read_scalar(args[1])?.check_init()?;
  + let addr = args[1];
  + let addr_scalar = this.read_scalar(addr)?.check_init()?;
  + let futex_ptr = this.force_ptr(addr_scalar)?.erase_tag();
  let op = this.read_scalar(args[2])?.to_i32()?;
  let val = this.read_scalar(args[3])?.to_i32()?;
  - this.memory.check_ptr_access(addr, Size::from_bytes(4), Align::from_bytes(4).unwrap())?;
  -
  - let addr = addr.assert_ptr().erase_tag();
  -
  let thread = this.get_active_thread();
  let futex_private = this.eval_libc_i32("FUTEX_PRIVATE_FLAG")?;
  @@ -33,10 +31,11 @@ pub fn futex<'tcx>(
  if !this.is_null(timeout)? {
  throw_ub_format!("miri does not support timeouts for futex operations");
  }
  + this.memory.check_ptr_access(addr_scalar, Size::from_bytes(4), Align::from_bytes(4).unwrap())?;
  let futex_val = this.read_scalar_at_offset(args[1], 0, this.machine.layouts.i32)?.to_i32()?;
  if val == futex_val {
  this.block_thread(thread);
  - this.futex_wait(addr, thread);
  + this.futex_wait(futex_ptr, thread);
  } else {
  let eagain = this.eval_libc("EAGAIN")?;
  this.set_last_error(eagain)?;
  @@ -45,7 +44,7 @@ pub fn futex<'tcx>(
  op if op == futex_wake => {
  let mut n = 0;
  for _ in 0..val {
  - if let Some(thread) = this.futex_wake(addr) {
  + if let Some(thread) = this.futex_wake(futex_ptr) {
  this.unblock_thread(thread);
  n += 1;
  } else {
  