From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
jpoimboe@redhat.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
Subject: Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable
Date: Tue, 23 Mar 2021 15:23:33 -0500 [thread overview]
Message-ID: <78329592-1992-4560-72f2-b0ab4eb088c6@linux.microsoft.com> (raw)
In-Reply-To: <20210323182753.GE5490@sirena.org.uk>
On 3/23/21 1:27 PM, Mark Brown wrote:
> On Tue, Mar 23, 2021 at 12:23:34PM -0500, Madhavan T. Venkataraman wrote:
>> On 3/23/21 12:02 PM, Mark Rutland wrote:
>
>>> 3. Figure out exception boundary handling. I'm currently working to
>>> simplify the entry assembly down to a uniform set of stubs, and I'd
>>> prefer to get that sorted before we teach the unwinder about
>>> exception boundaries, as it'll be significantly simpler to reason
>>> about and won't end up clashing with the rework.
>
>> So, here is where I still have a question. Is it necessary for the unwinder
>> to know the exception boundaries? Is it not enough if it knows if there are
>> exceptions present? For instance, using something like num_special_frames
>> I suggested above?
>
> For reliable stack trace we can live with just flagging things as
> unreliable when we know there's an exception boundary somewhere but (as
> Mark mentioned elsewhere) being able to actually go through a subset of
> exception boundaries safely is likely to help usefully improve the
> performance of live patching, and for defensiveness we want to try to
> detect during an actual unwind anyway so it ends up being a performance
> improvment and double check rather than saving us code. Better
> understanding of what's going on in the presence of exceptions may also
> help other users of the unwinder which can use stacks which aren't
> reliable get better results.
>
Actually, I was not suggesting that the counter replace the unwinder
intelligence to recognize exception boundaries. I was only suggesting
the use of the counter for arch_stack_walk_reliable().
But I am fine with not implementing the counter for now.
Madhavan
WARNING: multiple messages have this Message-ID (diff)
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
jpoimboe@redhat.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
Subject: Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable
Date: Tue, 23 Mar 2021 15:23:33 -0500 [thread overview]
Message-ID: <78329592-1992-4560-72f2-b0ab4eb088c6@linux.microsoft.com> (raw)
In-Reply-To: <20210323182753.GE5490@sirena.org.uk>
On 3/23/21 1:27 PM, Mark Brown wrote:
> On Tue, Mar 23, 2021 at 12:23:34PM -0500, Madhavan T. Venkataraman wrote:
>> On 3/23/21 12:02 PM, Mark Rutland wrote:
>
>>> 3. Figure out exception boundary handling. I'm currently working to
>>> simplify the entry assembly down to a uniform set of stubs, and I'd
>>> prefer to get that sorted before we teach the unwinder about
>>> exception boundaries, as it'll be significantly simpler to reason
>>> about and won't end up clashing with the rework.
>
>> So, here is where I still have a question. Is it necessary for the unwinder
>> to know the exception boundaries? Is it not enough if it knows if there are
>> exceptions present? For instance, using something like num_special_frames
>> I suggested above?
>
> For reliable stack trace we can live with just flagging things as
> unreliable when we know there's an exception boundary somewhere but (as
> Mark mentioned elsewhere) being able to actually go through a subset of
> exception boundaries safely is likely to help usefully improve the
> performance of live patching, and for defensiveness we want to try to
> detect during an actual unwind anyway so it ends up being a performance
> improvment and double check rather than saving us code. Better
> understanding of what's going on in the presence of exceptions may also
> help other users of the unwinder which can use stacks which aren't
> reliable get better results.
>
Actually, I was not suggesting that the counter replace the unwinder
intelligence to recognize exception boundaries. I was only suggesting
the use of the counter for arch_stack_walk_reliable().
But I am fine with not implementing the counter for now.
Madhavan
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-03-23 20:24 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5997dfe8d261a3a543667b83c902883c1e4bd270>
2021-03-15 16:57 ` [RFC PATCH v2 0/8] arm64: Implement reliable stack trace madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:57 ` [RFC PATCH v2 1/8] arm64: Implement stack trace termination record madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 15:09 ` Mark Brown
2021-03-18 15:09 ` Mark Brown
2021-03-18 20:26 ` Madhavan T. Venkataraman
2021-03-18 20:26 ` Madhavan T. Venkataraman
2021-03-19 12:30 ` Mark Brown
2021-03-19 12:30 ` Mark Brown
2021-03-19 14:29 ` Madhavan T. Venkataraman
2021-03-19 14:29 ` Madhavan T. Venkataraman
2021-03-19 18:19 ` Madhavan T. Venkataraman
2021-03-19 18:19 ` Madhavan T. Venkataraman
2021-03-19 22:03 ` Madhavan T. Venkataraman
2021-03-19 22:03 ` Madhavan T. Venkataraman
2021-03-23 10:24 ` Mark Rutland
2021-03-23 10:24 ` Mark Rutland
2021-03-23 12:39 ` Madhavan T. Venkataraman
2021-03-23 12:39 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 2/8] arm64: Implement frame types madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 17:40 ` Mark Brown
2021-03-18 17:40 ` Mark Brown
2021-03-18 22:22 ` Madhavan T. Venkataraman
2021-03-18 22:22 ` Madhavan T. Venkataraman
2021-03-19 13:22 ` Mark Brown
2021-03-19 13:22 ` Mark Brown
2021-03-19 14:40 ` Madhavan T. Venkataraman
2021-03-19 14:40 ` Madhavan T. Venkataraman
2021-03-19 15:02 ` Madhavan T. Venkataraman
2021-03-19 15:02 ` Madhavan T. Venkataraman
2021-03-19 16:20 ` Mark Brown
2021-03-19 16:20 ` Mark Brown
2021-03-19 16:27 ` Madhavan T. Venkataraman
2021-03-19 16:27 ` Madhavan T. Venkataraman
2021-03-23 10:34 ` Mark Rutland
2021-03-23 10:34 ` Mark Rutland
2021-03-15 16:57 ` [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 18:26 ` Mark Brown
2021-03-18 18:26 ` Mark Brown
2021-03-18 20:29 ` Madhavan T. Venkataraman
2021-03-18 20:29 ` Madhavan T. Venkataraman
2021-03-23 10:36 ` Mark Rutland
2021-03-23 10:36 ` Mark Rutland
2021-03-23 12:40 ` Madhavan T. Venkataraman
2021-03-23 12:40 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 4/8] arm64: Detect an EL1 exception frame and mark a stack trace unreliable madvenka
2021-03-15 16:57 ` madvenka
2021-03-23 10:42 ` Mark Rutland
2021-03-23 10:42 ` Mark Rutland
2021-03-23 12:46 ` Madhavan T. Venkataraman
2021-03-23 12:46 ` Madhavan T. Venkataraman
2021-03-23 13:04 ` Mark Rutland
2021-03-23 13:04 ` Mark Rutland
2021-03-23 13:31 ` Madhavan T. Venkataraman
2021-03-23 13:31 ` Madhavan T. Venkataraman
2021-03-23 14:33 ` Mark Rutland
2021-03-23 14:33 ` Mark Rutland
2021-03-23 15:22 ` Madhavan T. Venkataraman
2021-03-23 15:22 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 5/8] arm64: Detect an FTRACE " madvenka
2021-03-15 16:57 ` madvenka
2021-03-23 10:51 ` Mark Rutland
2021-03-23 10:51 ` Mark Rutland
2021-03-23 12:56 ` Madhavan T. Venkataraman
2021-03-23 12:56 ` Madhavan T. Venkataraman
2021-03-23 13:36 ` Mark Rutland
2021-03-23 13:36 ` Mark Rutland
2021-03-23 13:38 ` Madhavan T. Venkataraman
2021-03-23 13:38 ` Madhavan T. Venkataraman
2021-03-23 14:15 ` Madhavan T. Venkataraman
2021-03-23 14:15 ` Madhavan T. Venkataraman
2021-03-23 14:57 ` Mark Rutland
2021-03-23 14:57 ` Mark Rutland
2021-03-23 15:26 ` Madhavan T. Venkataraman
2021-03-23 15:26 ` Madhavan T. Venkataraman
2021-03-23 16:20 ` Madhavan T. Venkataraman
2021-03-23 16:20 ` Madhavan T. Venkataraman
2021-03-23 17:02 ` Mark Rutland
2021-03-23 17:02 ` Mark Rutland
2021-03-23 17:23 ` Madhavan T. Venkataraman
2021-03-23 17:23 ` Madhavan T. Venkataraman
2021-03-23 17:27 ` Madhavan T. Venkataraman
2021-03-23 17:27 ` Madhavan T. Venkataraman
2021-03-23 18:27 ` Mark Brown
2021-03-23 18:27 ` Mark Brown
2021-03-23 20:23 ` Madhavan T. Venkataraman [this message]
2021-03-23 20:23 ` Madhavan T. Venkataraman
2021-03-23 18:30 ` Mark Rutland
2021-03-23 18:30 ` Mark Rutland
2021-03-23 20:24 ` Madhavan T. Venkataraman
2021-03-23 20:24 ` Madhavan T. Venkataraman
2021-03-23 21:04 ` Madhavan T. Venkataraman
2021-03-23 21:04 ` Madhavan T. Venkataraman
2021-03-23 16:48 ` Mark Rutland
2021-03-23 16:48 ` Mark Rutland
2021-03-23 16:53 ` Madhavan T. Venkataraman
2021-03-23 16:53 ` Madhavan T. Venkataraman
2021-03-23 17:09 ` Mark Rutland
2021-03-23 17:09 ` Mark Rutland
2021-03-15 16:57 ` [RFC PATCH v2 6/8] arm64: Check the return PC of every stack frame madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:57 ` [RFC PATCH v2 7/8] arm64: Detect kretprobed functions in stack trace madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:58 ` [RFC PATCH v2 8/8] arm64: Implement arch_stack_walk_reliable() madvenka
2021-03-15 16:58 ` madvenka
2021-03-15 19:01 ` [RFC PATCH v2 0/8] arm64: Implement reliable stack trace Madhavan T. Venkataraman
2021-03-15 19:01 ` Madhavan T. Venkataraman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=78329592-1992-4560-72f2-b0ab4eb088c6@linux.microsoft.com \
--to=madvenka@linux.microsoft.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=jpoimboe@redhat.com \
--cc=jthierry@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.