From: Kevin Buettner <kevinb@redhat.com>
To: Nikola Prica <nikola.prica@rt-rk.com>
Cc: gdb-patches@sourceware.org,
"Ananthakrishna Sowda (asowda)" <asowda@cisco.com>,
"Ivan Baev (ibaev)" <ibaev@cisco.com>,
'Nemanja Popov' <nemanja.popov@rt-rk.com>,
Djordje Todorovic <Djordje.Todorovic@rt-rk.com>
Subject: Re: [PING]Fix for prologue processing on PowerPC
Date: Wed, 08 Nov 2017 16:58:00 -0000 [thread overview]
Message-ID: <20171108095850.394a48ca@pinnacle.lan> (raw)
In-Reply-To: <e3274bee-eb2d-3706-3af0-59f28c9c0899@rt-rk.com>
See:
https://sourceware.org/ml/gdb-patches/2017-10/msg00098.html
Kevin
On Thu, 26 Oct 2017 12:02:19 +0200
Nikola Prica <nikola.prica@rt-rk.com> wrote:
> Can someone please take a look into this?
>
> Thanks,
>
> Nikola Prica
>
> On 22.09.2017. 14:11, Nikola Prica wrote:
> > After analyzing dump of ppc program, whose crash occurred after
> > watchdog_force_here () function, GDB couldn't print full back trace
> > because GDB couldn't unwind PC from the watchdog fucntion.
> >
> > The problem is introduced with the following patch:
> >
> > https://sourceware.org/ml/gdb-patches/2008-08/msg00245.html
> >
> > In function skip_prologue(), shifted lr_reg makes below condition always
> > false because non-shifted lr_reg value is expected to be checked.
> >
> > else if (lr_reg >= 0 &&
> > /* std Rx, NUM(r1) || stdu Rx, NUM(r1) */
> > (((op & 0xffff0000) == (lr_reg | 0xf8010000)) ||
> > /* stw Rx, NUM(r1) */
> > ((op & 0xffff0000) == (lr_reg | 0x90010000)) ||
> > /* stwu Rx, NUM(r1) */
> > ((op & 0xffff0000) == (lr_reg | 0x94010000))))
> >
> > Before this fix unwinding was able to work because it relied on unwind
> > directives or on some of the next frames to find PC. Problem came with
> > watchdog_force_here() function which didn't contain unwind directives.
> >
> > I wasn't able to produce test case that would show improvements for end
> > user. I suppose that changes would be visible if watchdog event was
> > called, but I don't have valid ppc board to try this. I have tried this
> > code on simple test case with few functions in back trace. The back
> > trace is printed correctly with and without this fix, but the difference
> > between those two runs is that the body of the upper condition was
> > visited with this patch. After visiting the body there was no need to
> > look for PC counter in next frames nor to use unwind directives.
next prev parent reply other threads:[~2017-11-08 16:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-22 12:11 Fix " Nikola Prica
2017-10-05 2:01 ` Kevin Buettner
2017-10-26 10:02 ` [PING]Fix " Nikola Prica
2017-11-08 16:58 ` Kevin Buettner [this message]
2017-11-09 18:15 ` [PING][PATCH] Fix " Nikola Prica
2017-12-01 19:37 ` pedromfc
2017-12-19 15:57 ` Nikola Prica
2017-12-29 18:05 ` Pedro Franco de Carvalho
2018-01-09 11:22 ` Nikola Prica
2018-01-10 17:26 ` Pedro Franco de Carvalho
2018-01-11 15:12 ` Nikola Prica
2018-01-19 7:49 ` Nikola Prica
2018-01-19 19:01 ` Pedro Franco de Carvalho
2018-01-19 19:08 ` Pedro Franco de Carvalho
2018-01-27 14:32 ` Nikola Prica
2018-01-31 18:04 ` Pedro Franco de Carvalho
2018-01-31 18:28 ` Ulrich Weigand
2018-02-01 13:09 ` Nikola Prica
2018-01-02 10:29 ` Yao Qi
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