linux-kernel - Re: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support

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Date:	Thu, 14 Jul 2016 13:09:08 -0400
From:	William Cohen <wcohen@...hat.com>
To:	Catalin Marinas <catalin.marinas@....com>,
	David Long <dave.long@...aro.org>
Cc:	Huang Shijie <shijie.huang@....com>,
	James Morse <james.morse@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Pratyush Anand <panand@...hat.com>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Steve Capper <steve.capper@...aro.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Li Bin <huawei.libin@...wei.com>,
	Jisheng Zhang <jszhang@...vell.com>,
	Mark Rutland <mark.rutland@....com>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Petr Mladek <pmladek@...e.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Robin Murphy <robin.murphy@....com>,
	Mark Brown <broonie@...nel.org>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Dave P Martin <Dave.Martin@....com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	yalin wang <yalin.wang2010@...il.com>,
	Yang Shi <yang.shi@...aro.org>,
	Zi Shen Lim <zlim.lnx@...il.com>,
	John Blackwood <john.blackwood@...r.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Adam Buchbinder <adam.buchbinder@...il.com>,
	Christoffer Dall <christoffer.dall@...aro.org>
Subject: Re: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support

On 07/14/2016 12:22 PM, Catalin Marinas wrote:
> On Fri, Jul 08, 2016 at 12:35:44PM -0400, David Long wrote:
>> David A. Long (3):
>>   arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature
>>   arm64: Add more test functions to insn.c
>>   arm64: add conditional instruction simulation support
>>
>> Pratyush Anand (2):
>>   arm64: Blacklist non-kprobe-able symbol
>>   arm64: Treat all entry code as non-kprobe-able
>>
>> Sandeepa Prabhu (4):
>>   arm64: Kprobes with single stepping support
>>   arm64: kprobes instruction simulation support
>>   arm64: Add kernel return probes support (kretprobes)
>>   kprobes: Add arm64 case in kprobe example module
>>
>> William Cohen (1):
>>   arm64: Add trampoline code for kretprobes
> 
> I applied these patches on top of the arm64 for-next/core branch an
> tried to run the resulting kernel in a guest (on a Juno platform using
> both kvmtool and qemu) with KPROBES_SANITY_TEST enabled. Unfortunately,
> the kernel fails to boot with lots of "Unexpected kernel single-step
> exception at EL1".
> 
> Did you manage to run Kprobes in a guest before?
> 

Hi,

I ran the systemtap testsuite several times on a physical machine running a kernel with the kprobe v15 patches without problem. Shouldn't the guest machine behave in the same manner as a host machine for single stepping and exception handling?  If the guest machine is failing, wouldn't that suggest there is a problem with the KVM handling of single stepping for guests?

-Will Cohen