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From: Mark Brown <broonie@kernel.org>
To: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: 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 1/8] arm64: Implement stack trace termination record
Date: Fri, 19 Mar 2021 12:30:23 +0000	[thread overview]
Message-ID: <20210319123023.GC5619@sirena.org.uk> (raw)
In-Reply-To: <8591e34a-c181-f3ff-e691-a6350225e5b4@linux.microsoft.com>

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On Thu, Mar 18, 2021 at 03:26:13PM -0500, Madhavan T. Venkataraman wrote:
> On 3/18/21 10:09 AM, Mark Brown wrote:

> > If we are going to add the extra record there would probably be less
> > potential for confusion if we pointed it at some sensibly named dummy
> > function so anything or anyone that does see it on the stack doesn't get
> > confused by a NULL.

> I agree. I will think about this some more. If no other solution presents
> itself, I will add the dummy function.

After discussing this with Mark Rutland offlist he convinced me that so
long as we ensure the kernel doesn't print the NULL record we're
probably OK here, the effort setting the function pointer up correctly
in all circumstances (especially when we're not in the normal memory
map) is probably not worth it for the limited impact it's likely to have
to see the NULL pointer (probably mainly a person working with some
external debugger).  It should be noted in the changelog though, and/or
merged in with the relevant change to the unwinder.

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WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie@kernel.org>
To: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: 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 1/8] arm64: Implement stack trace termination record
Date: Fri, 19 Mar 2021 12:30:23 +0000	[thread overview]
Message-ID: <20210319123023.GC5619@sirena.org.uk> (raw)
In-Reply-To: <8591e34a-c181-f3ff-e691-a6350225e5b4@linux.microsoft.com>


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On Thu, Mar 18, 2021 at 03:26:13PM -0500, Madhavan T. Venkataraman wrote:
> On 3/18/21 10:09 AM, Mark Brown wrote:

> > If we are going to add the extra record there would probably be less
> > potential for confusion if we pointed it at some sensibly named dummy
> > function so anything or anyone that does see it on the stack doesn't get
> > confused by a NULL.

> I agree. I will think about this some more. If no other solution presents
> itself, I will add the dummy function.

After discussing this with Mark Rutland offlist he convinced me that so
long as we ensure the kernel doesn't print the NULL record we're
probably OK here, the effort setting the function pointer up correctly
in all circumstances (especially when we're not in the normal memory
map) is probably not worth it for the limited impact it's likely to have
to see the NULL pointer (probably mainly a person working with some
external debugger).  It should be noted in the changelog though, and/or
merged in with the relevant change to the unwinder.

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  reply	other threads:[~2021-03-19 12:31 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 [this message]
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
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

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