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

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Message-ID: <578E32C1.3000903@linaro.org>
Date:	Tue, 19 Jul 2016 10:01:37 -0400
From:	David Long <dave.long@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Petr Mladek <pmladek@...e.com>,
	Zi Shen Lim <zlim.lnx@...il.com>,
	Will Deacon <will.deacon@....com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	yalin wang <yalin.wang2010@...il.com>,
	Li Bin <huawei.libin@...wei.com>,
	John Blackwood <john.blackwood@...r.com>,
	Pratyush Anand <panand@...hat.com>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Huang Shijie <shijie.huang@....com>,
	Dave P Martin <Dave.Martin@....com>,
	Jisheng Zhang <jszhang@...vell.com>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Steve Capper <steve.capper@...aro.org>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Yang Shi <yang.shi@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	William Cohen <wcohen@...hat.com>,
	Alex Bennée <alex.bennee@...aro.org>,
	Adam Buchbinder <adam.buchbinder@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Murphy <robin.murphy@....com>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Christoffer Dall <christoffer.dall@...aro.org>
Subject: Re: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support

On 07/19/2016 09:57 AM, Catalin Marinas wrote:
> On Thu, Jul 14, 2016 at 05:22:08PM +0100, 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".
>
> FYI, we managed to track down the issue to two bugs in the arm64 kernel
> boot part, occasionally leaving the PSTATE.D bit set for kernel threads.
> While not KVM specific, the pre-conditions were more likely when running
> as a guest (receiving interrupts early on during boot, possibly because
> of a slow-down in the booting process due to stage 2 page faulting
> mechanism).
>
> Will is going to post the fixes soon.
>

Excellent news.

Thanks,
-dl