From: Mark Brown <broonie@kernel.org>
To: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks
Date: Tue, 13 Apr 2021 12:02:55 +0100 [thread overview]
Message-ID: <20210413110255.GB5586@sirena.org.uk> (raw)
In-Reply-To: <d92ec07e-81e1-efb8-b417-d1d8a211ef7f@linux.microsoft.com>
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On Mon, Apr 12, 2021 at 02:55:35PM -0500, Madhavan T. Venkataraman wrote:
>
> OK. Just so I am clear on the whole picture, let me state my understanding so far.
> Correct me if I am wrong.
> 1. We are hoping that we can convert a significant number of SYM_CODE functions to
> SYM_FUNC functions by providing them with a proper FP prolog and epilog so that
> we can get objtool coverage for them. These don't need any blacklisting.
I wouldn't expect to be converting lots of SYM_CODE to SYM_FUNC. I'd
expect the overwhelming majority of SYM_CODE to be SYM_CODE because it's
required to be non standard due to some external interface - things like
the exception vectors, ftrace, and stuff around suspend/hibernate. A
quick grep seems to confirm this.
> 3. We are going to assume that the reliable unwinder is only for livepatch purposes
> and will only be invoked on a task that is not currently running. The task either
The reliable unwinder can also be invoked on itself.
> 4. So, the only functions that will need blacklisting are the remaining SYM_CODE functions
> that might give up the CPU voluntarily. At this point, I am not even sure how
> many of these will exist. One hopes that all of these would have ended up as
> SYM_FUNC functions in (1).
There's stuff like ret_from_fork there.
> I suggest we do (3) first. Then, review the assembly functions to do (1). Then, review the
> remaining ones to see which ones must be blacklisted, if any.
I'm not clear what the concrete steps you're planning to do first are
there - your 3 seems like a statement of assumptions. For flagging
functions I do think it'd be safer to default to assuming that all
SYM_CODE functions can't be unwound reliably rather than only explicitly
listing ones that cause problems.
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next prev parent reply other threads:[~2021-04-13 11:03 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <705993ccb34a611c75cdae0a8cb1b40f9b218ebd>
2021-04-05 20:43 ` [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks madvenka
2021-04-05 20:43 ` [RFC PATCH v2 1/4] arm64: Implement infrastructure for " madvenka
2021-04-08 15:15 ` Mark Brown
2021-04-08 17:17 ` Mark Brown
2021-04-08 19:30 ` Madhavan T. Venkataraman
2021-04-08 23:30 ` Madhavan T. Venkataraman
2021-04-09 11:57 ` Mark Brown
2021-04-05 20:43 ` [RFC PATCH v2 2/4] arm64: Mark a stack trace unreliable if an EL1 exception frame is detected madvenka
2021-04-05 20:43 ` [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable madvenka
2021-04-08 16:58 ` Mark Brown
2021-04-08 19:23 ` Madhavan T. Venkataraman
2021-04-09 11:31 ` Mark Brown
2021-04-09 14:02 ` Madhavan T. Venkataraman
2021-04-09 12:27 ` Mark Rutland
2021-04-09 17:23 ` Madhavan T. Venkataraman
2021-04-05 20:43 ` [RFC PATCH v2 4/4] arm64: Mark stack trace as unreliable if kretprobed functions are present madvenka
2021-04-09 12:09 ` [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks Mark Rutland
2021-04-09 17:16 ` Madhavan T. Venkataraman
2021-04-09 21:37 ` Josh Poimboeuf
2021-04-09 22:05 ` Madhavan T. Venkataraman
2021-04-09 22:32 ` Josh Poimboeuf
2021-04-09 22:53 ` Josh Poimboeuf
2021-04-11 17:54 ` Madhavan T. Venkataraman
2021-04-12 16:59 ` Mark Brown
2021-04-13 22:53 ` Josh Poimboeuf
2021-04-14 12:24 ` Mark Brown
2021-04-12 17:36 ` Mark Brown
2021-04-12 19:55 ` Madhavan T. Venkataraman
2021-04-13 11:02 ` Mark Brown [this message]
2021-04-14 10:23 ` Madhavan T. Venkataraman
2021-04-14 12:35 ` Mark Brown
2021-04-16 14:43 ` Madhavan T. Venkataraman
2021-04-16 15:36 ` Mark Brown
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