Re: [reverse/record] adjust_pc_after_break in reverse execution mode?

[teawater <teawater at gmail dot com>]

The old patch make my_waitpid_record set pc even if this is not a breakpoint.
So I make a new patch that my_waitpid_record just set pc when this is
a breakpoint.


2008-10-24  Hui Zhu  <teawater@gmail.com>

	* record.c (record_wait): Check breakpint before forward
	execute in replay mode.
	Check breakpoint use function "breakpoint_inserted_here_p"
	in replay mode.
	Set pc if forward execute, gdbarch_decr_pc_after_break is not
	0 and this is not single step in replay mode.

	* linux-nat.c (my_waitpid_record): Add
	gdbarch_decr_pc_after_break to pc if need.



On Fri, Oct 24, 2008 at 17:57, teawater <teawater@gmail.com> wrote:
> Hi buddies,
>
> This is the new patch that fix the break bug.
>
> But I think I still need to add some code to deal with signal.
>
> 2008-10-24  Hui Zhu  <teawater@gmail.com>
>
>        * record.c (record_wait): Check breakpint before forward
>        execute in replay mode.
>        Check breakpoint use function "breakpoint_inserted_here_p"
>        in replay mode.
>        Set pc if forward execute, gdbarch_decr_pc_after_break is not
>        0 and this is not single step in replay mode.
>
>        * linux-nat.c (my_waitpid_record): Add
>        gdbarch_decr_pc_after_break to pc if need.
>
> Thanks,
> Hui
>
> On Fri, Oct 24, 2008 at 16:10, teawater <teawater@gmail.com> wrote:
>> Thanks Pedro and Michael,
>>
>> I think the reason is P record let inferior step recycle in the
>> linux-nat target.
>> So when it break by breakpint, it will not let
>> (pc+gdbarch_decr_pc_after_break (gdbarch)). Then after
>> adjust_pc_after_break, The PC is error.
>>
>> I will try to deal with it.
>>
>> Hui
>>
>> On Fri, Oct 24, 2008 at 09:50, Pedro Alves <pedro@codesourcery.com> wrote:
>>> On Friday 24 October 2008 01:37:31, Michael Snyder wrote:
>>>> > In sum, it appears that decr_pc_after_break doesn't matter when you have
>>>> > continguous breakpoints, as long as you get from from B1's address to B2's
>>>> > address by single-stepping.  All is good then, it appears!
>>>>
>>>> I agree, at least that is the conclusion I am leaning toward.
>>>>
>>>
>>> Not so fast!  I knew I had to spend a little extra thinking about
>>> it, 'cause I knew something was broken, just couldn't find what.  :-)
>>> *as long as you get from from B1's address to B2's address
>>> by single-stepping* was a restriction that doesn't always apply.
>>>
>>> Here's a test that will fail in forward record/replay mode, but not
>>> in normal "play" mode.
>>>
>>> volatile int global_foo = 0;
>>>
>>> int
>>> main (int argc, char **argv)
>>> {
>>>  asm ("nop"); /* 1st insn */
>>>  asm ("nop"); /* 2nd insn */
>>>  asm ("nop"); /* 3rd insn */
>>>  asm ("nop"); /* 4th insn */
>>>  if (!global_foo)
>>>    goto ahead;
>>>  asm ("nop"); /* 5th insn */
>>>  asm ("nop"); /* 6th insn */
>>>  asm ("nop"); /* 7th insn */
>>>  asm ("nop"); /* 8th insn */  <<< break 1 here
>>>  ahead:
>>>  asm ("nop"); /* 9th insn */  <<< break 2 here
>>>  end:
>>>  return 0;
>>> }
>>>
>>> If you let the program reply until break 2 is hit, and assuming insn
>>> 8th and 9th are assembled as contiguous (they do on x86 -O0 for me), you'll
>>> see that adjust_pc_after_break will indeed make it appear that breakpoint
>>> 1 was hit.  Now, nops are nops, but real code could have something
>>> else there...
>>>
>>> /me goes back to bed.
>>>
>>> --
>>> Pedro Alves
>>>
>>
>

Attachment: record_wait_breakpoint.txt
Description: Text document