From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Cc: jpoimboe@redhat.com, peterz@infradead.org,
chenzhongjin@huawei.com, broonie@kernel.org,
nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com,
catalin.marinas@arm.com, will@kernel.org,
jamorris@linux.microsoft.com,
linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation
Date: Tue, 11 Apr 2023 23:50:51 -0500 [thread overview]
Message-ID: <8b7b779b-6552-c637-9a84-4dbc95fd0c07@linux.microsoft.com> (raw)
In-Reply-To: <c7e1df79-1506-4502-035b-24ddf6848311@linux.microsoft.com>
On 4/11/23 23:48, Madhavan T. Venkataraman wrote:
>
>
> On 4/11/23 23:17, Josh Poimboeuf wrote:
>> On Tue, Apr 11, 2023 at 02:25:11PM +0100, Mark Rutland wrote:
>>>> By your own argument, we cannot rely on the compiler as compiler implementations,
>>>> optimization strategies, etc can change in ways that are incompatible with any
>>>> livepatch implementation.
>>>
>>> That's not quite my argument.
>>>
>>> My argument is that if we assume some set of properties that compiler folk
>>> never agreed to (and were never made aware of), then compiler folk are well
>>> within their rights to change the compiler such that it doesn't provide those
>>> properties, and it's very likely that such expectation will be broken. We've
>>> seen that happen before (e.g. with jump tables).
>>>
>>> Consequently I think we should be working with compiler folk to agree upon some
>>> solution, where compiler folk will actually try to maintain the properties we
>>> depend upon (and e.g. they could have tests for). That sort of co-design has
>>> worked well so far (e.g. with things like kCFI).
>>>
>>> Ideally we'd have people in the same room to have a discussion (e.g. at LPC).
>>
>> That was the goal of my talk at LPC last year:
>>
>> https://lpc.events/event/16/contributions/1392/
>>
>> We discussed having the compiler annotate the tricky bits of control
>> flow, mainly jump tables and noreturns. It's still on my TODO list to
>> prototype that.
>>
>> Another alternative which has been suggested in the past by Indu and
>> others is for objtool to use DWARF/sframe as an input to help guide it
>> through the tricky bits.
>>
>
> I read through the SFrame spec file briefly. It looks like I can easily adapt my
> version 1 of the livepatch patchset which was based on DWARF to SFrame. If the compiler
> folks agree to properly support and maintain SFrame, then I could send the next version
> of the patchset based on SFrame.
>
> But I kinda need a clear path forward before I implement anything. I request the arm64
> folks to comment on the above approach. Would it be useful to initiate an email discussion
> with the compiler folks on what they plan to do to support SFrame? Or, should this all
> happen face to face in some forum like LPC?
>
> Madhavan
>
Just to be clear. This is not to replace Objtool as it has other uses as well, not just
reliable stack trace. I am trying to solve the reliable stack trace issue alone with
SFrame.
Madhavan
>> That seems more fragile -- as Madhavan mentioned, GCC-generated DWARF
>> has some reliability issues -- and also defeats some of the benefits of
>> reverse-engineering in the first place (we've found many compiler bugs
>> and other surprising kernel-compiler interactions over the years).
>>
>> Objtool's understanding of the control flow graph has been really
>> valuable for reasons beyond live patching (e.g., noinstr and uaccess
>> validation), it's definitely worth finding a way to make that more
>> sustainable.
>>
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next prev parent reply other threads:[~2023-04-12 4:51 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0337266cf19f4c98388e3f6d09f590d9de258dc7>
2023-02-02 7:40 ` [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation madvenka
2023-02-02 7:40 ` [RFC PATCH v3 01/22] objtool: Reorganize CFI code madvenka
2023-02-02 7:40 ` [RFC PATCH v3 02/22] objtool: Reorganize instruction-related code madvenka
2023-02-02 7:40 ` [RFC PATCH v3 03/22] objtool: Move decode_instructions() to a separate file madvenka
2023-02-02 7:40 ` [RFC PATCH v3 04/22] objtool: Reorganize Unwind hint code madvenka
2023-02-02 7:40 ` [RFC PATCH v3 05/22] objtool: Reorganize ORC types madvenka
2023-02-18 9:30 ` Suraj Jitindar Singh
2023-03-06 16:45 ` Madhavan T. Venkataraman
2023-02-02 7:40 ` [RFC PATCH v3 06/22] objtool: Reorganize ORC code madvenka
2023-02-02 7:40 ` [RFC PATCH v3 07/22] objtool: Reorganize ORC kernel code madvenka
2023-02-02 7:40 ` [RFC PATCH v3 08/22] objtool: Introduce STATIC_CHECK madvenka
2023-02-02 7:40 ` [RFC PATCH v3 09/22] objtool: arm64: Add basic definitions and compile madvenka
2023-02-02 7:40 ` [RFC PATCH v3 10/22] objtool: arm64: Implement decoder for Dynamic FP validation madvenka
2023-02-02 7:40 ` [RFC PATCH v3 11/22] objtool: arm64: Invoke the decoder madvenka
2023-02-02 7:40 ` [RFC PATCH v3 12/22] objtool: arm64: Compute destinations for call and jump instructions madvenka
2023-02-02 7:40 ` [RFC PATCH v3 13/22] objtool: arm64: Walk instructions and compute CFI for each instruction madvenka
2023-02-02 7:40 ` [RFC PATCH v3 14/22] objtool: arm64: Generate ORC data from CFI for object files madvenka
2023-02-02 7:40 ` [RFC PATCH v3 15/22] objtool: arm64: Add unwind hint support madvenka
2023-02-02 7:40 ` [RFC PATCH v3 16/22] arm64: Add unwind hints to exception handlers madvenka
2023-02-02 7:40 ` [RFC PATCH v3 17/22] arm64: Add kernel and module support for ORC madvenka
2023-02-02 7:40 ` [RFC PATCH v3 18/22] arm64: Build the kernel with ORC information madvenka
2023-02-10 7:52 ` Tomohiro Misono (Fujitsu)
2023-02-11 4:34 ` Madhavan T. Venkataraman
2023-02-02 7:40 ` [RFC PATCH v3 19/22] arm64: unwinder: Add a reliability check in the unwinder based on ORC madvenka
2023-02-23 4:07 ` Suraj Jitindar Singh
2023-03-06 16:52 ` Madhavan T. Venkataraman
2023-02-02 7:40 ` [RFC PATCH v3 20/22] arm64: Define HAVE_DYNAMIC_FTRACE_WITH_ARGS madvenka
2023-02-02 7:40 ` [RFC PATCH v3 21/22] arm64: Define TIF_PATCH_PENDING for livepatch madvenka
2023-02-02 7:40 ` [RFC PATCH v3 22/22] arm64: Enable livepatch for ARM64 madvenka
2023-03-01 3:12 ` [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation Tomohiro Misono (Fujitsu)
2023-03-02 16:23 ` Petr Mladek
2023-03-03 9:40 ` Tomohiro Misono (Fujitsu)
2023-03-06 16:58 ` Madhavan T. Venkataraman
2023-03-06 16:57 ` Madhavan T. Venkataraman
2023-03-23 17:17 ` Mark Rutland
2023-04-08 3:40 ` Madhavan T. Venkataraman
2023-04-11 13:25 ` Mark Rutland
2023-04-12 4:17 ` Josh Poimboeuf
2023-04-12 4:48 ` Madhavan T. Venkataraman
2023-04-12 4:50 ` Madhavan T. Venkataraman [this message]
2023-04-12 5:01 ` Josh Poimboeuf
2023-04-12 14:50 ` Madhavan T. Venkataraman
2023-04-12 15:52 ` Josh Poimboeuf
2023-04-13 14:59 ` Madhavan T. Venkataraman
2023-04-13 16:30 ` Josh Poimboeuf
2023-04-15 4:27 ` Madhavan T. Venkataraman
2023-04-15 5:05 ` Josh Poimboeuf
2023-04-15 16:15 ` Madhavan T. Venkataraman
2023-04-16 8:21 ` Indu Bhagat
2023-04-13 17:04 ` Nick Desaulniers
2023-04-13 18:15 ` Jose E. Marchesi
2023-04-15 4:14 ` Madhavan T. Venkataraman
2023-12-14 20:49 ` ARM64 Livepatch based on SFrame Madhavan T. Venkataraman
2023-12-15 13:04 ` Mark Rutland
2023-12-15 15:15 ` Madhavan T. Venkataraman
[not found] <CADBMgpxQ+oM_TrtKRiREcZoZSk=AfenV_bqOk_Vt-Ov5FPHMvw@mail.gmail.com>
2023-04-08 3:41 ` [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation Madhavan T. Venkataraman
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