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Re: exercising current aarch64 kprobe support with systemtap
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: David Long <dave dot long at linaro dot org>
- Cc: Pratyush Anand <panand at redhat dot com>, William Cohen <wcohen at redhat dot com>, systemtap at sourceware dot org, Mark Brown <broonie at linaro dot org>, Jeremy Linton <jlinton at redhat dot com>, David Smith <dsmith at redhat dot com>
- Date: Thu, 07 Jul 2016 15:58:37 -0400
- Subject: Re: exercising current aarch64 kprobe support with systemtap
- Authentication-results: sourceware.org; auth=none
- References: <befacf57-b8eb-2926-8f4f-742f0f055a4c@redhat.com> <d03cd7b7-3d6a-4e4d-71b6-a7325ddd76f3@redhat.com> <8f40d0b9-5550-92f9-d1c5-8769f52304c0@redhat.com> <576B5501.1030106@linaro.org> <e5f466f7-4a60-efb3-d104-375807d271b2@redhat.com> <576C29E1.8060805@linaro.org> <0a594132-796b-779d-b473-a06c0f3e8ae8@redhat.com> <20160627141840.GB8139@dhcppc9> <ff385049-3e0f-b3ee-8395-4cc3ab1b13d5@redhat.com> <CAHB_Guqex38XodKctocG_4X6foZ2ZWZggYtMjAPhpDUL53DbXA@mail.gmail.com> <577EA7EE.2070607@linaro.org>
David Long <dave.long@linaro.org> writes:
> [...]
>> - bug_handler() calls report_bug() which calls __warn()
>> - __warn() does lot of pr_warn() which invokes print_worker_info()
>> where we have a kprobe instrumented.
>> - Therefore, we are encountering this issue.
>> [...]
> It sounds like the only fix would be to expand the blacklist to any
> function that could be called in a debug exception-handling context? [...]
The kernel maintains its own blacklist by means of designating some
low-level functions with the "__kprobes" attribute. That protects
those regions of code from "perf probe"-directed kprobes too.
- FChE