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Subject: Re: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support
To: Catalin Marinas <catalin.marinas@arm.com>
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Cc: Mark Rutland <mark.rutland@arm.com>, Petr Mladek <pmladek@suse.com>,
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From: David Long <dave.long@linaro.org>
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Date: Tue, 19 Jul 2016 10:01:37 -0400
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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