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From: Mark Rutland <mark.rutland@arm.com>
To: Doug Anderson <dianders@chromium.org>
Cc: kgdb-bugreport@lists.sourceforge.net,
	Will Deacon <will.deacon@arm.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Stephen Boyd <swboyd@chromium.org>
Subject: Re: Possible to annotate ARM64 IRQ handling to help gdb?
Date: Mon, 4 Feb 2019 13:12:41 +0000	[thread overview]
Message-ID: <20190204131241.GB46085@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <CAD=FV=X+YOf6Pt8bwuh0KCs=H3KTAW3atLLEP_X-5BMqtYMyZQ@mail.gmail.com>

On Fri, Feb 01, 2019 at 01:38:05PM -0800, Doug Anderson wrote:
> Hi,

Hi Doug,

> I was wondering if anyone out there has given any thought to
> annotating the ARM64 IRQ handling in such a way that we could stack
> crawl past el1_irq() when in gdb.
> 
> I spent a bit of time on this a few months ago and documented all my
> findings in:
> 
> https://bugs.chromium.org/p/chromium/issues/detail?id=908721

There, the error from GDB is:

    Backtrace stopped: previous frame identical to this frame (corrupt
    stack?)

... is that misleading?

... or do we have some duplicate stack frame that we somewhow skip in
the kernel unwinder?

> I can copy and paste all the discussion from that bug here, but since
> it's public hopefully folks can read the discussion / investigation
> there.  To put it briefly, though: I can stack crawl past "el1_irq"
> with the normal linux stack crawl (which is what kdb uses) but I can't
> crawl past "el1_irq" in gdb().  After talking to some of our tools
> guys here I'm fairly certain that we could solve this with the right
> CFI directives, but when I poked at it I wasn't able to figure out the
> magic.

AFAICT, we don't know why GDB is terminating early. Could we please
figure that out first? e.g. by looking for the above message in the GDB
sources.

If we do need CFI annotations, I'd rather move that entry code to C
first, to minimize how painful that is. I have an ongoing project [1] to
do just that...

Thanks,
Mark.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/entry-deasm

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  parent reply	other threads:[~2019-02-04 13:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-01 21:38 Possible to annotate ARM64 IRQ handling to help gdb? Doug Anderson
2019-02-04 12:31 ` Dave Martin
2019-02-11 17:27   ` Doug Anderson
2019-02-11 19:57     ` Dave Martin
2019-02-13 21:19       ` Doug Anderson
2019-02-04 13:12 ` Mark Rutland [this message]
2019-02-11 18:05   ` Doug Anderson

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