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From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: "nobuta.keiya@fujitsu.com" <nobuta.keiya@fujitsu.com>
Cc: "mark.rutland@arm.com" <mark.rutland@arm.com>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
	"ardb@kernel.org" <ardb@kernel.org>,
	"sjitindarsingh@gmail.com" <sjitindarsingh@gmail.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"will@kernel.org" <will@kernel.org>,
	"jmorris@namei.org" <jmorris@namei.org>,
	"pasha.tatashin@soleen.com" <pasha.tatashin@soleen.com>,
	"jthierry@redhat.com" <jthierry@redhat.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"live-patching@vger.kernel.org" <live-patching@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v8 3/4] arm64: Introduce stack trace reliability checks in the unwinder
Date: Tue, 24 Aug 2021 07:19:52 -0500	[thread overview]
Message-ID: <62d8969d-8ba1-4554-16b4-1c0bd4f8d9e7@linux.microsoft.com> (raw)
In-Reply-To: <TY2PR01MB5257EA835C6F28ABF457EB0B85C59@TY2PR01MB5257.jpnprd01.prod.outlook.com>



On 8/24/21 12:55 AM, nobuta.keiya@fujitsu.com wrote:
> Hi Madhavan,
> 
>> @@ -245,7 +271,36 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
>>  		fp = thread_saved_fp(task);
>>  		pc = thread_saved_pc(task);
>>  	}
>> -	unwind(consume_entry, cookie, task, fp, pc);
>> +	unwind(consume_entry, cookie, task, fp, pc, false);
>> +}
>> +
>> +/*
>> + * arch_stack_walk_reliable() may not be used for livepatch until all of
>> + * the reliability checks are in place in unwind_consume(). However,
>> + * debug and test code can choose to use it even if all the checks are not
>> + * in place.
>> + */
> 
> I'm glad to see the long-awaited function :)
> 
> Does the above comment mean that this comment will be removed by
> another patch series that about live patch enablement, instead of [PATCH 4/4]?
> 
> It seems to take time... But I start thinking about test code.
> 

Yes. This comment will be removed when livepatch will be enabled eventually.
So, AFAICT, there are 4 pieces that are needed:

- Reliable stack trace in the kernel. I am trying to address that with my patch
  series.

- Mark Rutland's work for making patching safe on ARM64.

- Objtool (or alternative method) for stack validation.

- Suraj Jitindar Singh's patch for miscellaneous things needed to enable live patch.

Once all of these pieces are in place, livepatch can be enabled.

That said, arch_stack_walk_reliable() can be used for test and debug purposes anytime
once this patch series gets accepted.

Thanks.

Madhavan

  reply	other threads:[~2021-08-24 12:19 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <b45aac2843f16ca759e065ea547ab0afff8c0f01>
2021-08-12 19:05 ` [RFC PATCH v8 0/4] arm64: Reorganize the unwinder and implement stack trace reliability checks madvenka
2021-08-12 19:06   ` [RFC PATCH v8 1/4] arm64: Make all stack walking functions use arch_stack_walk() madvenka
2021-08-24 13:13     ` Mark Rutland
2021-08-24 17:21       ` Madhavan T. Venkataraman
2021-08-24 17:38         ` Madhavan T. Venkataraman
2021-08-24 17:38         ` Mark Brown
2021-08-24 17:40           ` Madhavan T. Venkataraman
2021-08-26  4:52       ` Madhavan T. Venkataraman
2021-10-09 23:41       ` Madhavan T. Venkataraman
2021-08-12 19:06   ` [RFC PATCH v8 2/4] arm64: Reorganize the unwinder code for better consistency and maintenance madvenka
2021-08-26 15:46     ` Mark Brown
2021-08-26 23:19       ` Madhavan T. Venkataraman
2021-09-01 16:20         ` Mark Brown
2021-09-02  7:10           ` Madhavan T. Venkataraman
2021-08-12 19:06   ` [RFC PATCH v8 3/4] arm64: Introduce stack trace reliability checks in the unwinder madvenka
2021-08-24  5:55     ` nobuta.keiya
2021-08-24 12:19       ` Madhavan T. Venkataraman [this message]
2021-08-25  0:01         ` nobuta.keiya
2021-08-26 15:57     ` Mark Brown
2021-08-26 23:31       ` Madhavan T. Venkataraman
2021-08-12 19:06   ` [RFC PATCH v8 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka
2021-08-12 19:17   ` [RFC PATCH v8 0/4] arm64: Reorganize the unwinder and implement stack trace reliability checks Madhavan T. Venkataraman

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