RE: [PATCH v13 11/11] arm64: Select HAVE_RELIABLE_STACKTRACE

From: "nobuta.keiya@fujitsu.com" <nobuta.keiya@fujitsu.com>
To: "'Madhavan T. Venkataraman'" <madvenka@linux.microsoft.com>,
	"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>,
	"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: [PATCH v13 11/11] arm64: Select HAVE_RELIABLE_STACKTRACE
Date: Thu, 27 Jan 2022 01:13:37 +0000	[thread overview]
Message-ID: <TY2PR01MB5257F92BDD5E55914A63DD2C85219@TY2PR01MB5257.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <1a0e19db-a7f8-4c8e-0163-398fcd364d54@linux.microsoft.com>

> >> I have not seen any activity on that in a long time. IIRC, Julien quit RedHat.
> >> I don't know if anyone else has taken over this work in RedHat.
> >>
> >> Sorry, I don't have any more information.
> >>
> >> Madhavan
> >
> > Thanks for your information.
> >
> > By the way, I'm considering test code for arch_stack_walk_reliable().
> > Specifically, I apply Suraj's patch to enable livepatch, and added a function
> > that sleeps between SYM_CODE_START and SYM_CODE_END, then livepatch
> > checks if the task has an unreliable stack.
> > For now my internal test code working correctly, but my Kconfig excludes
> > STACK_VALIDATION dependency.
> >
> > It seems that objtool will not be enabled yet, so I would like to test it easier.
> > If you are already testing with this patch, could you tell me how to do it?
> >
> >
> 
> For now, I have an instrumented kernel that directly invokes arch_stack_walk_reliable()
> from various places in the kernel (interrupt handlers, exception handlers, ftrace entry,
> kprobe handler, etc). I also have a test driver to induce conditions like null pointer
> dereference. I use this to test different cases where arch_stack_walk_reliable() should
> return an error.

That's good to know, thanks.

> 
> As for livepatch testing, I have enhanced objtool and the kernel so the frame pointer can
> be validated dynamically rather than statically. I have tested various different livepatch
> selftests successfully. I have also written my own livepatch tests to add to the selftests.
> I am currently working on preparing an RFC patch series for review. Basically, this series
> implements STACK_VALIDATION in a different way.
> 
> I plan to publish my work soon (hopefully Feb 2022). I was going to do in December. However,
> my workload in Microsoft did not permit me to do that. I am also planning to set up a github
> repo so people can try out my changes, if they are interested.
> 
> So, stay tuned.
> 
> Madhavan

I'm very interested, so I would to be happy if you could tell me when the github repo is set up.

Thanks again,

Keiya