From: marc.zyngier@arm.com (Marc Zyngier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support
Date: Fri, 15 Jul 2016 10:53:54 +0100 [thread overview]
Message-ID: <5788B2B2.8010205@arm.com> (raw)
In-Reply-To: <877fcn46pn.fsf@linaro.org>
On 15/07/16 09:59, Alex Benn?e wrote:
>
> Marc Zyngier <marc.zyngier@arm.com> writes:
>
>> On 15/07/16 08:50, Catalin Marinas wrote:
>>> On Thu, Jul 14, 2016 at 01:09:08PM -0400, William Cohen wrote:
>>>> 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?
>>>>
>>>> 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?
>>>
>>> It didn't fail for me on the host either. What's strange is that on some
>>> occasions even the guest managed to get to a prompt. I'll do more tests
>>> today on different CPU configurations, just to rule out potential
>>> hardware issues. If not hardware related, it's possible that the
>>> interaction with KVM doesn't work as expected, maybe the
>>> saving/restoring of the guest debug state loses information.
>>
>> Could well be the latter. I'll try to have a look, but Alex Benn?e (on
>> cc) is our man when it comes to the KVM debug infrastructure.
>>
>> Alex, any chance you could try this and shed some light on it?
>
> Sure I'll have a look. There are problems with running gdb inside a
> guest while trying to debug from outside associated with single-stepping
> but none of this should get in the way if your not debugging the guest.
>
> Let me get my system spun up and see if I can reproduce.
>
> Shall I just apply this series on top of the current master?
I managed to reproduce it by taskset-ing 2 vcpus on the same physical
CPU, and trying a few dozen times on Juno-r1. It is not easy to trigger,
but when it happens it is quite bad.
Warning, pure speculation ahead: I suspect that we preempt a vcpu with
single-step enabled, somehow fail to clear the SS state, schedule
another vcpu that inherits that state and takes this unexpected SS
exception.
/me goes and have a look...
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2016-07-15 9:53 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-08 16:35 [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support David Long
2016-07-08 16:35 ` [PATCH v15 01/10] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature David Long
2016-07-15 10:57 ` Catalin Marinas
2016-07-15 14:51 ` David Long
2016-07-15 15:13 ` Catalin Marinas
2016-07-15 17:51 ` David Long
2016-07-19 14:17 ` Catalin Marinas
2016-07-08 16:35 ` [PATCH v15 02/10] arm64: Add more test functions to insn.c David Long
2016-07-08 16:35 ` [PATCH v15 03/10] arm64: add conditional instruction simulation support David Long
2016-07-08 16:35 ` [PATCH v15 04/10] arm64: Kprobes with single stepping support David Long
2016-07-20 9:36 ` Marc Zyngier
2016-07-20 11:16 ` Catalin Marinas
2016-07-20 19:08 ` David Long
2016-07-21 8:44 ` Marc Zyngier
2016-07-20 15:49 ` Catalin Marinas
2016-07-21 14:50 ` David Long
2016-07-20 16:09 ` Marc Zyngier
2016-07-20 16:28 ` Catalin Marinas
2016-07-20 16:31 ` Marc Zyngier
2016-07-20 16:46 ` Marc Zyngier
2016-07-20 17:04 ` Catalin Marinas
2016-07-21 16:33 ` David Long
2016-07-21 17:16 ` Catalin Marinas
2016-07-21 17:23 ` Marc Zyngier
2016-07-21 18:33 ` David Long
2016-07-22 10:16 ` Catalin Marinas
2016-07-22 15:51 ` David Long
2016-07-25 17:13 ` Catalin Marinas
2016-07-25 22:27 ` David Long
2016-07-27 11:50 ` Daniel Thompson
2016-07-27 22:13 ` David Long
2016-07-28 14:40 ` Catalin Marinas
2016-07-29 9:01 ` Daniel Thompson
2016-08-04 4:47 ` David Long
2016-08-08 11:13 ` Daniel Thompson
2016-08-08 14:29 ` David Long
2016-08-08 22:49 ` Masami Hiramatsu
2016-08-09 17:23 ` Catalin Marinas
2016-08-10 20:41 ` David Long
2016-08-08 22:19 ` Masami Hiramatsu
2016-07-26 9:50 ` Daniel Thompson
2016-07-26 16:55 ` Catalin Marinas
2016-07-27 10:01 ` Dave Martin
2016-07-26 17:54 ` Mark Rutland
2016-07-27 11:19 ` Daniel Thompson
2016-07-27 11:38 ` Dave Martin
2016-07-27 11:42 ` Daniel Thompson
2016-07-27 13:38 ` Mark Rutland
2016-07-08 16:35 ` [PATCH v15 05/10] arm64: Blacklist non-kprobe-able symbol David Long
2016-07-08 16:35 ` [PATCH v15 06/10] arm64: Treat all entry code as non-kprobe-able David Long
2016-07-15 16:47 ` Catalin Marinas
2016-07-19 0:53 ` David Long
2016-07-08 16:35 ` [PATCH v15 07/10] arm64: kprobes instruction simulation support David Long
2016-07-10 22:51 ` Paul Gortmaker
2016-07-08 16:35 ` [PATCH v15 08/10] arm64: Add trampoline code for kretprobes David Long
2016-07-19 13:46 ` Catalin Marinas
2016-07-20 18:28 ` David Long
2016-07-08 16:35 ` [PATCH v15 09/10] arm64: Add kernel return probes support (kretprobes) David Long
2016-07-08 16:35 ` [PATCH v15 10/10] kprobes: Add arm64 case in kprobe example module David Long
2016-07-14 16:22 ` [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support Catalin Marinas
2016-07-14 17:09 ` William Cohen
2016-07-15 7:50 ` Catalin Marinas
2016-07-15 8:01 ` Marc Zyngier
2016-07-15 8:59 ` Alex Bennée
2016-07-15 9:04 ` Marc Zyngier
2016-07-15 9:53 ` Marc Zyngier [this message]
2016-07-14 17:56 ` David Long
2016-07-19 13:57 ` Catalin Marinas
2016-07-19 14:01 ` David Long
2016-07-19 18:27 ` Catalin Marinas
2016-07-19 19:38 ` David Long
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