From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
Miroslav Benes <mbenes@suse.cz>, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/3] arm64: Implement reliable stack trace
Date: Mon, 19 Oct 2020 18:41:55 -0500 [thread overview]
Message-ID: <20201019234155.q26jkm22fhnnztiw@treble> (raw)
In-Reply-To: <20201016121534.GC5274@sirena.org.uk>
On Fri, Oct 16, 2020 at 01:15:34PM +0100, Mark Brown wrote:
>
> Yes, exactly - just copying the existing implementations and hoping that
> it's sensible/relevant and covers everything that's needed. It's not
> entirely clear what a reliable stacktrace is expected to do that a
> normal stacktrace doesn't do beyond returning an error code.
While in the end there may not be much of a difference between normal
and reliable stacktraces beyond returning an error code, it still
requires beefing up the unwinder's error detection abilities.
> > > The searching for a defined thread entry point for example isn't
> > > entirely visible in the implementations.
>
> > For now I'll speak only of x86, because I don't quite remember how
> > powerpc does it.
>
> > For thread entry points, aka the "end" of the stack:
>
> > - For ORC, the end of the stack is either pt_regs, or -- when unwinding
> > from kthreads, idle tasks, or irqs/exceptions in entry code --
> > UNWIND_HINT_EMPTY (found by the unwinder's check for orc->end.
>
> > [ Admittedly the implementation needs to be cleaned up a bit. EMPTY
> > is too broad and needs to be split into UNDEFINED and ENTRY. ]
>
> > - For frame pointers, by convention, the end of the stack for all tasks
> > is a defined stack offset: end of stack page - sizeof(pt_regs).
>
> > And yes, all that needs to be documented.
>
> Ah, I'd have interpreted "defined thread entry point" as meaning
> expecting to find specific functions appering at the end of the stack
> rather than meaning positively identifying the end of the stack - for
> arm64 we use a NULL frame pointer to indicate this in all situations.
> In that case that's one bit that is already clear.
I think a NULL frame pointer isn't going to be robust enough. For
example NULL could easily be introduced by a corrupt stack, or by asm
frame pointer misuse.
--
Josh
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next prev parent reply other threads:[~2020-10-19 23:44 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 17:26 [RFC PATCH 0/3] arm64: Implement reliable stack trace Mark Brown
2020-10-12 17:26 ` [RFC PATCH 1/3] arm64: remove EL0 exception frame record Mark Brown
2020-10-12 17:26 ` [RFC PATCH 2/3] arm64: stacktrace: Report when we reach the end of the stack Mark Brown
2020-10-13 11:07 ` Mark Rutland
2020-10-12 17:26 ` [RFC PATCH 3/3] arm64: stacktrace: Implement reliable stacktrace Mark Brown
2020-10-13 10:42 ` Mark Brown
2020-10-13 11:42 ` Mark Rutland
2020-10-13 16:12 ` Mark Brown
2020-10-15 13:33 ` Miroslav Benes
2020-10-15 15:57 ` Mark Brown
2020-10-16 10:13 ` Miroslav Benes
2020-10-16 12:30 ` Mark Brown
2020-10-15 13:39 ` [RFC PATCH 0/3] arm64: Implement reliable stack trace Miroslav Benes
2020-10-15 14:16 ` Mark Rutland
2020-10-15 15:49 ` Mark Brown
2020-10-15 21:29 ` Josh Poimboeuf
2020-10-16 11:14 ` Mark Rutland
2020-10-20 10:03 ` Mark Rutland
2020-10-20 15:58 ` Josh Poimboeuf
2020-10-16 12:15 ` Mark Brown
2020-10-19 23:41 ` Josh Poimboeuf [this message]
2020-10-20 15:39 ` Mark Brown
2020-10-20 16:28 ` Josh Poimboeuf
2021-01-27 14:02 ` Madhavan T. Venkataraman
2021-01-27 16:40 ` Mark Rutland
2021-01-27 17:11 ` Mark Brown
2021-01-27 17:24 ` Madhavan T. Venkataraman
2021-01-27 19:54 ` Madhavan T. Venkataraman
2021-01-28 14:22 ` Mark Brown
2021-01-28 15:26 ` Josh Poimboeuf
2021-01-29 21:39 ` Madhavan T. Venkataraman
2021-02-01 3:20 ` Madhavan T. Venkataraman
2021-02-01 14:39 ` Mark Brown
2021-01-30 4:38 ` Madhavan T. Venkataraman
2021-02-01 15:21 ` Madhavan T. Venkataraman
2021-02-01 15:46 ` Madhavan T. Venkataraman
2021-02-01 16:02 ` Mark Rutland
2021-02-01 16:22 ` Mark Brown
2021-02-01 21:40 ` Madhavan T. Venkataraman
2021-02-01 21:38 ` Madhavan T. Venkataraman
2021-02-01 23:00 ` Josh Poimboeuf
2021-02-02 2:29 ` Madhavan T. Venkataraman
2021-02-02 3:36 ` Josh Poimboeuf
2021-02-02 10:05 ` Mark Rutland
2021-02-02 13:33 ` Madhavan T. Venkataraman
2021-02-02 13:35 ` Madhavan T. Venkataraman
2021-02-02 23:32 ` Madhavan T. Venkataraman
2021-02-03 16:53 ` Mark Rutland
2021-02-03 19:03 ` Madhavan T. Venkataraman
2021-02-05 2:36 ` Madhavan T. Venkataraman
2021-02-01 21:59 ` Madhavan T. Venkataraman
2021-02-02 13:36 ` Mark Brown
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