Re: ptrace single-stepping change breaks Wine

Linus Torvalds
2004-12-29T20:05:46Z

On Wed, 29 Dec 2004, Jesse Allen wrote:
>
> >
> > So does removing the conditional TF clear make everything work again?
> >
>
> Yes, as long as TIF_SINGLESTEP is not set in set_singlestep().

That may be a clue, if only because that makes absolutely _zero_ sense.

Setting TIF_SINGLESTEP shouldn't actually matter in this case, since we
set the TRAP_FLAG in eflags by hand anyway (and that's what TIF_SINGESTEP
will just re-do when returning to user space).

What TIF_SINGLESTEP _does_ do, however, is change how some other issues
are reported to user space. In particular, it causes system call tracing
(see arch/i386/kernel/ptrace.c: do_syscall_trace), and maybe it is _that_
that messes up Wine.

So instead of removing the setting of TIF_SINGLESTEP in set_singlestep(),
can you test whether removing the _testing_ of it in do_syscall_trace()
makes things happier for you? Hmm?

(Also, looking at the code, I get the feeling that set_singlestep() should
_only_ set TIF_SINGLESTEP, and not set the TRAP_FLAG by hand at all, since
TIF_SINGESTEP should take care of that detail regardless).

Linus