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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>, Krishna Dani <krishna dot mohan at linaro dot org>, Jakub Pavelek <jakub dot pavelek at linaro dot org>, Mark Salter <msalter at redhat dot com>
- Date: Thu, 7 Nov 2013 17:24:37 +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>
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.
Thanks,
Sandeepa
>
> Thanks,
> PM