From: Pedro Alves <palves@redhat.com>
To: Tom Tromey <tromey@redhat.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH 1/2] avoid infinite loop with bad debuginfo
Date: Tue, 19 Nov 2013 15:10:00 -0000 [thread overview]
Message-ID: <528B7F15.7040605@redhat.com> (raw)
In-Reply-To: <87d2lxpo1l.fsf@fleche.redhat.com>
On 11/18/2013 06:23 PM, Tom Tromey wrote:
>>> + if (VALUE_LVAL (new_val) == lval_register
>>> + && value_lazy (new_val)
>>> + && frame_id_eq (VALUE_FRAME_ID (new_val), last_frame_id))
>
> Pedro> I think this should also check the regnum:
>
> Barf. I have a memory of actually writing that. False memory I guess.
> Sigh.
>
>>> #4 0x0000007fb7f0956c in clone () from /lib64/libc.so.6
>>> #5 0x0000007fb7f0956c in clone () from /lib64/libc.so.6
>>> Backtrace stopped: previous frame identical to this frame (corrupt stack?)
>
> Pedro> Doesn't this all then mean that we somehow ended up with two identical
> Pedro> frames with the same id on the frame chain (#4 and #5) ?
> Pedro> That seems very wrong to me.
>
> Pedro> It seems to be a better fix would be to make
> Pedro> get_prev_frame_1/get_prev_frame_raw discard frame #5 before it
> Pedro> was ever linked in. Either that, or, if we really need to keep
> Pedro> #5 linked in, we should find a way for frame_id_eq (#4, #5) to
> Pedro> return false.
>
> I will look into it, but my recollection is that last time we got into
> this area, it was somehow undesirable to undo whatever changes were done
> by existing frame sniffers.
Hmm, I don't think that's the same issue. I'm just talking about
something like moving the frame_id_eq check to the end of
get_prev_frame_1, after calling get_prev_frame_raw. Something
like:
prev_frame = get_prev_frame_raw (this_frame);
/* Check that this and the prev frame are not identical. If they
are, there is most likely a stack cycle. */
if (prev_frame != NULL
&& frame_id_eq (get_frame_id (prev_frame),
get_frame_id (this_frame)))
{
if (frame_debug)
{
fprintf_unfiltered (gdb_stdlog, "-> ");
fprint_frame (gdb_stdlog, NULL);
fprintf_unfiltered (gdb_stdlog, " // this frame has same ID }\n");
}
this_frame->stop_reason = UNWIND_SAME_ID;
/* Unlink. */
this_frame->prev = NULL;
return NULL;
}
return prev_frame;
}
--
Pedro Alves
next prev parent reply other threads:[~2013-11-19 15:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-13 20:51 [PATCH 0/2] fix multi-threaded unwinding on AArch64 Tom Tromey
2013-11-13 20:51 ` [PATCH 2/2] handle an unspecified return address column Tom Tromey
2013-11-22 18:22 ` Tom Tromey
2013-11-26 13:55 ` Joel Brobecker
2013-11-26 14:30 ` Mark Kettenis
2013-11-26 14:37 ` Joel Brobecker
2013-11-26 14:41 ` Mark Kettenis
2013-11-26 14:42 ` Joel Brobecker
2013-11-26 14:50 ` Tom Tromey
2013-11-26 15:05 ` Tom Tromey
2013-11-26 15:16 ` Tom Tromey
2013-11-26 16:11 ` Joel Brobecker
2013-11-13 22:03 ` [PATCH 1/2] avoid infinite loop with bad debuginfo Tom Tromey
2013-11-14 17:34 ` Pedro Alves
2013-11-18 18:25 ` Tom Tromey
2013-11-19 15:10 ` Pedro Alves [this message]
2013-11-19 15:47 ` Tom Tromey
2013-11-19 16:33 ` Pedro Alves
2013-11-19 19:07 ` Tom Tromey
2013-11-19 20:24 ` Pedro Alves
2013-11-19 20:56 ` Tom Tromey
2013-11-20 18:27 ` [PATCH] Don't let two frames with the same id end up in the frame chain. (Re: [PATCH 1/2] avoid infinite loop with bad debuginfo) Pedro Alves
2013-11-21 0:33 ` Tom Tromey
2013-11-21 16:40 ` Pedro Alves
2013-11-21 19:25 ` Tom Tromey
2013-11-22 14:13 ` [COMMITTED] Make use of the frame stash to detect wider stack cycles. (was: Re: [PATCH] Don't let two frames with the same id end up in the frame chain. (Re: [PATCH 1/2] avoid infinite loop with bad debuginfo)) Pedro Alves
2013-11-22 14:29 ` [PATCH] Don't let two frames with the same id end up in the frame chain. (Re: [PATCH 1/2] avoid infinite loop with bad debuginfo) Pedro Alves
2013-11-22 14:52 ` [PATCH 1/2] avoid infinite loop with bad debuginfo Pedro Alves
2013-11-22 17:16 ` Tom Tromey
2013-11-22 17:56 ` Pedro Alves
2013-11-19 15:52 ` Tom Tromey
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