From: Pedro Alves <palves@redhat.com>
To: Yao Qi <yao@codesourcery.com>
Cc: Michal Lesniewski <m.lesniewski@samsung.com>, gdb@sourceware.org
Subject: Re: Implementation of different software breakpoint kinds in gdb server
Date: Thu, 18 Oct 2012 10:42:00 -0000 [thread overview]
Message-ID: <507FDD00.1000309@redhat.com> (raw)
In-Reply-To: <507FD9CB.7060805@codesourcery.com>
On 10/18/2012 11:28 AM, Yao Qi wrote:
> On 10/18/2012 06:08 PM, Pedro Alves wrote:
>> Offhand, the main issues with tracepoints on ARM are:
>>
>> #1 - gdbserver needs to know how to step over the tracepoints, without gdb's intervention.
>>
>> #2 - ARM can't hw single-step, so that needs to be done the hard way, with breakpoints
>> (a.k.a., software single-step).
>> All the logic to do that is in gdb. This conflicts with #1.
>>
>> So we'd need to teach gdbserver to software single-step. Maybe it's possible
>> to tell offline all the possible destinations of an instruction, so we could still
>> leave that logic in gdb, but I suspect not.
>
> I am wondering that it might be relatively easier to implement fast tracepoint in which step-over is not needed, if finding a jumppad is not a problem :)
Maybe. :-)
The "move out of jumppad" logic uses single-stepping. I guess we could come up
with something clever to avoid it. Related, linux_fast_tracepoint_collecting logic
assumes it can identify a thread from its tls base / thread area. And this assumes
you can retrieve this address without an infcall. This is possible on x86. Don't know
about ARM (well, in an ABI-stable way).
--
Pedro Alves
next prev parent reply other threads:[~2012-10-18 10:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-18 9:23 Michal Lesniewski
2012-10-18 10:08 ` Pedro Alves
2012-10-18 10:28 ` Yao Qi
2012-10-18 10:42 ` Pedro Alves [this message]
2012-10-18 11:44 ` Michal Lesniewski
2012-10-18 12:01 ` Pedro Alves
2012-10-19 0:31 ` John Gilmore
2012-10-19 8:51 ` Michal Lesniewski
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