Re: [Discussion/Prec] The record speed up plan (Make speed like without prec)

[Hui Zhu <teawater@gmail.com>]

Are you use gdb-cvs-head?

Hui

On Fri, May 21, 2010 at 13:33, paawan oza <paawan1982@yahoo.com> wrote:
> Hi Hui,
>
> would you please explain the idea of following lines ?
>
> if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)
>    fork_fn = find_function_in_inferior ("fork", &fork_objf);
> if (!fork_fn)
>    if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)
>      fork_fn = find_function_in_inferior ("fork", &fork_objf);
>      if (!fork_fn) +    return -1; +  ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
>  /* Tell record.c that the following inferior change doesn't need record. */
>      old_cleanups = record_disable_set (); + +
>  /* Tell target that this is linux pre-record.  */
>      self_cleanups = make_cleanup_restore_integer      (&linux_pre_recording); +  linux_pre_recording = 1;
>      ret = call_function_by_hand (fork_fn, 0, &ret); + +  do_cleanups (self_cleanups);
>
>
> PS: I am unable to find some definations e.g. find_function_in_inferior
>
> please comment.
>
> Regards,
> Oza.
>
>
>
>
> ----- Original Message ----
> From: Hui Zhu <teawater@gmail.com>
> To: gdb@sourceware.org
> Cc: Michael Snyder <msnyder@vmware.com>; paawan oza <paawan1982@yahoo.com>; Eli Zaretskii <eliz@gnu.org>
> Sent: Wed, May 19, 2010 12:48:50 PM
> Subject: Re: [Discussion/Prec] The record speed up plan (Make speed like  without prec)
>
> Hi,
>
> This is a demo.
>
> Still not support segment register, system call and some others.
>
> Thanks,
> Hui
>
> On Fri, Apr 30, 2010 at 21:23, Hui Zhu <teawater@gmail.com> wrote:
>> Hello,
>>
>> I think the record speed is the biggest trouble of prec.
>> After I did a long think and a lot of test around with it.  I got a
>> idea.  Actually, I have began the code work.
>>
>> I found that the big trouble is prec let the inferior just step.  It
>> make inferior speed very low.  Because the setp need a lot of context
>> works.
>> So I think let inferior continue can make it speed up.  But How to
>> record the change of each step?
>>
>> Some physicists said all the things in the world have execution rules.
>>  So use the current stat of this thing, we will get what will happen
>> in the future.  Looks most of rules are still not found.  :)
>>
>> But lucky for us that insns exec rules we know.  So most of insns
>> (There a some special, I will talk it later), if we have the a
>> inferior value(memory and reg), we can get the each value of next
>> insn.
>> So if we can record the all the value of a inferior A(or all the value
>> that will be change, but to get it will need parse the insns that will
>> be exec, this is not easy.) , we can let the inferior exec without
>> step.  If the user want reverse exec, get the each step value from A.
>> Then the record speed will very faster than before.
>>
>> But this way have a 2 question.
>> 1.  How to record all the status of a inferior？ For the linux,
>> checkpoint already use fork to record the inferior.  So prec will use
>> it too.
>> And when we want get the old status of inferior step by step, we can
>> let the forked process step by step.  That will easy by parse the insn
>> and know what will happen.
>>
>> 2.  How to handle special insns that we will not know what will happen
>> after it exec?
>> The first type of this insns is system call.  Linux have catchpoint
>> that make inferior stop before and after syscall.  Then we can record
>> the change after the system call.
>> The other insn is like rdtsc, I don't know howto get the feature value
>> of this type.  My current idea with them is give up all the record
>> after this insn.
>> If user need, insert special breakpoint for it.  Next time, inferior
>> will stop on this insn, then prec can record the value after it exec.
>>
>> BTW, I call this new function pre_record, I agree with you if you said
>> this name is ugly. :)
>>
>> Please tell me your opinions about my idea.  That will help me a lot.  Thanks.
>>
>> Thanks,
>> Hui
>>
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