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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: Tue, 20 Oct 2020 11:28:06 -0500	[thread overview]
Message-ID: <20201020162806.6kl6japxkij7dzel@treble> (raw)
In-Reply-To: <20201020153913.GE9448@sirena.org.uk>

On Tue, Oct 20, 2020 at 04:39:13PM +0100, Mark Brown wrote:
> On Mon, Oct 19, 2020 at 06:41:55PM -0500, Josh Poimboeuf wrote:
> > On Fri, Oct 16, 2020 at 01:15:34PM +0100, Mark Brown wrote:
> 
> > > 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.
> 
> Is it just the particular poison value that you're concerned about here
> or are you looking for additional checks of some other kind?

You just need to know you've conclusively reached the user entry point
on the stack, without missing any functions.

A sufficiently unique poison value might be ok.  Though, defining a
certain stack offset as the "end" seems more robust.

-- 
Josh


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  reply	other threads:[~2020-10-20 16:29 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
2020-10-20 15:39             ` Mark Brown
2020-10-20 16:28               ` Josh Poimboeuf [this message]
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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