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Re: [Fwd: Re: Regarding systemtap support for AArch64]
- From: Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>
- To: Petr Machata <pmachata at redhat dot com>
- Cc: William Cohen <wcohen at redhat dot com>, Mark Wielaard <mjw at redhat dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, systemtap at sourceware dot org, Deepak Saxena <dsaxena at linaro dot org>, Mark Salter <msalter at redhat dot com>
- Date: Thu, 7 Nov 2013 19:19:55 +0530
- Subject: Re: [Fwd: Re: Regarding systemtap support for AArch64]
- Authentication-results: sourceware.org; auth=none
- References: <1383340682 dot 3850 dot 864 dot camel at bordewijk dot wildebeest dot org> <m2habsnq4w dot fsf at redhat dot com> <5277FBF2 dot 2080108 at redhat dot com> <m2wqknmumc dot fsf at redhat dot com> <52791818 dot 9070809 at redhat dot com> <m2eh6tn9cv dot fsf at redhat dot com> <CA+b37P2xA5vDBW7rWrEfTOvrzCC+VQpjad+Ge26m6uRjG-sp2w at mail dot gmail dot com> <CA+b37P3gWnONOPTeuPSTOc9U=_mEcg+BD+xOqpoaFSsaiD3T-A at mail dot gmail dot com>
On 7 November 2013 19:13, Sandeepa Prabhu <sandeepa.prabhu@linaro.org> wrote:
> On 7 November 2013 17:24, Sandeepa Prabhu <sandeepa.prabhu@linaro.org> wrote:
>> On 6 November 2013 15:24, Petr Machata <pmachata@redhat.com> wrote:
>>> William Cohen <wcohen@redhat.com> writes:
>>>
>>>> On 11/04/2013 09:48 PM, Petr Machata wrote:
>>>>> That 0x3F in x8 might be __NR_read, that might be from the syscall that
>>>>> got us here. So possibly makes sense. 0x112 is __NR_syscalls, I don't
>>>>> see how that ended up there. Maybe from a conditional? 0x2004 might
>>>>> certainly be a length, though it's an odd one. The two kernel-space
>>>>> parameters have similar values, and the one user-space is quite
>>>>> different--again, makes sense.
>>>>
>>>> These examples systemtap might not be the best. It is just printing
>>>> information for the first vfs.read or vfs.read.return encountered, so
>>>
>>> I understand. I was trying to figue out what's in the registers. I can
>>> agree that x0 to x4 hold vfs_read arguments on entry, so why doesn't, on
>>> function return, x0 hold the return value?
>>>
>>>> I wonder if there might be some issue with the patches implementing
>>>> the arm64 kprobes support and that the registers are not be saved
>>>> properly.
>>>
>>> I was wondering about the same thing.
>> Hi Will, Petr,
>>
>> Yes, I found some design issue with respect to trampoline placement,
>> (my code is the culprit!!). I am going to fix this soon and update you
>> all.
>>
> Hi Will, Petr,
>
> I have fixed the issue and now able to get proper function return
> values. (Earlier, trampoline was not installed at correct location, so
> used to carry wrong register context to handler)
> Updated patches are at:
> https://git.linaro.org/gitweb?p=people/sandeepa.prabhu/linux-aarch64.git;a=shortlog;h=refs/heads/arm64-kprobes-devel
>
> Please switch to my devel branch:
> "git://git.linaro.org/people/sandeepa.prabhu/linux-aarch64.git
> Branch: arm64-kprobes-devel" and let me know how this work.
[ Also, please ignore the code comment and commit descriptions, I will
change them when publishing v3 patchset, but before that, want to
conduct more test and find as many bugs as possible ]
>
> ~Sandeepa
>
>> Thanks,
>> Sandeepa
>>>
>>> Thanks,
>>> PM