On Fri, 23 Sep 2022 at 20:14:23 +0000, David Holland wrote:
On Fri, Sep 23, 2022 at 01:39:16PM +0200, Martin Husemann wrote:
> > Then, shouldn't the open(2) (and posix_openpt(3)) at least fail with
> > EINVAL or something if other flags are specified?
>
> The man page says:
>
> Note that unlike implementations on some other operating systems,
> posix_openpt() does not return EINVAL if the value of oflag would be
> deemed invalid, instead it is simply ignored. This means it is not
> possible to dynamically test which open(2) flags are possible to set, and
> apply a fallback if EINVAL is received.
That is, however, kind of a feeble excuse :-)
Agreed. But I inferred this was perhaps done this way on purpose, and
could be controversial to change. (Would also then mean downstream code
would have to special-case NetBSD releases and/or add tests which could
be cumbersome.) I hadn't got around to asking, I was dealing with
documenting the reality and working with the vte project so that NetBSD
support for gnome-terminal/mate-terminal/xfce4-terminal/et al. was
accepted.
While my inclination would be to make it work, until someone wants to
figure out how to do that it seems straightforward to make O_NONBLOCK
fail:
Index: tty_ptm.c
===================================================================
RCS file: /cvsroot/src/sys/kern/tty_ptm.c,v
retrieving revision 1.43
diff -u -p -r1.43 tty_ptm.c
--- tty_ptm.c 29 Jun 2021 22:40:53 -0000 1.43
+++ tty_ptm.c 23 Sep 2022 20:12:07 -0000
@@ -338,6 +338,10 @@ ptmopen(dev_t dev, int flag, int mode, s
dev_t ttydev;
struct mount *mp;
+ if (flag & O_NONBLOCK) {
+ return EINVAL;
+ }
+
switch(minor(dev)) {
case 0: /* /dev/ptmx */
case 2: /* /emul/linux/dev/ptmx */
It's not just O_NONBLOCK that can be expected/desired, vte wants to set
O_CLOEXEC as well. The Linux kernel accepts and applies both of those
flags in a posix_openpt(3) call.
OpenBSD does this validation in posix_openpt(3) directly:
/* User must specify O_RDWR in oflag. */
if ((oflag & O_ACCMODE) != O_RDWR ||
(oflag & ~(O_ACCMODE | O_NOCTTY)) != 0) {
errno = EINVAL;
return -1;
}
Now, that doesn't cover the case that someone simply calls open(2) on
the ptmx cloning device directly, so safer to be placed where you're
suggesting. (And I make no claims to being an authority on any of
this, I've simply looked at it a bit, and may well have missed
something.)
Regards,
Dave
