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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 19:13:54 +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>
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.
~Sandeepa
> Thanks,
> Sandeepa
>>
>> Thanks,
>> PM