On Thu, Apr 07, 2016 at 05:20:50PM -0700, Andy Lutomirski wrote:
> > > > I had a trinity process get stuck last overnight.
> > > > The reason for it getting stuck is my bug (I think), but
> > > > there's an odd unrelated thing I noticed while debugging this..
> > > >
> > > > $ strace -p 20966
> > > > strace: Process 20966 attached
> > > > strace: [ Process PID=20966 runs in x32 mode. ]
> > > >
> > > > So I don't use that new-fangled x32 stuff.
> > > > I don't even have CONFIG_X86_X32 compiled in.
> > > >
> > > > Is this strace getting confused, or did we somehow screw
> > > > up the syscall entry code ?
> > > >
> > > > Dave
> > > >
> > >
> > > I think you're just seeing an oddity of how x32 works. Unlike
> > > "compat", x32-ness of the current syscall isn't a special magic state
> > > variable; it's just but 31 in the syscall nr. So trying to do an x32
> > > syscall on a non-x32 syscall should still show bit 31 set to ptracers,
> > > and the strace probably decodes this as being in x32 mode.
> >
> > But this is an x86-64 binary, and it's the main process, not one of the
> > fuzzing
> > child processes. It shouldn't be even trying to do anything weird.
> > It creates a bunch of fd's, then enters a loop forking/reaping children.
> > (In this case it actually hung while creating the fd's)
> >
> > Trinity doesn't actually have any knowledge of x32 at all, mostly because
> > it's been irrelevant to me (and most other people).
> >
>
> Hmm. Do you have the next couple lines of strace output by any
> chance? I'm wondering if this is a classic bug/misfeature/confusion
> in the way that orig_ax works.
I don't. That box got rebooted a couple dozen times since then.
FWIW, I've not seen this happen since. Very strange.
Dave
