stack unwinding on aix

stack unwinding on aix

[Kamal R. Prasad]

Hello,

 I am trying to locate a piece of code in gdb 6.3
which does srack unwinding in AIX (5.3). When
unwinding the stack in my C code, I noticed a lot of
dummy frames whose pc points to the data segment
and/or outside th text segment(s). Can someone tell me
how gdb identifies such dummy frames and wherein the
code base it is? rs6000-tdep.c contains some algo for
frameless function detection etc.., but that isn't all
to it.

thanks
-kamal


------------------------------------------------------------
Kamal R. Prasad
UNIX systems consultant 
http://members.fortunecity.com/kamalp
kamalp@acm.org

In theory, there is no difference between theory and practice. In practice, there is.
------------------------------------------------------------


		
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Re: stack unwinding on aix

[Mark Kettenis]

   Date: Mon, 20 Jun 2005 23:25:50 -0700 (PDT)
   From: "Kamal R. Prasad" <kamalpr@yahoo.com>

   Hello,

    I am trying to locate a piece of code in gdb 6.3
   which does srack unwinding in AIX (5.3). When
   unwinding the stack in my C code, I noticed a lot of
   dummy frames whose pc points to the data segment
   and/or outside th text segment(s). Can someone tell me
   how gdb identifies such dummy frames and wherein the
   code base it is? rs6000-tdep.c contains some algo for
   frameless function detection etc.., but that isn't all
   to it.

I'm afraid the AIX/RS6000/POWER code is suffering from quite a bit of
bit-rot.  It's a bit of a mess, so I can't blame you for failing to
understand the code.  The sparc, vax or m88k code might be much easier
for you to understand..  Look frame functions name xxx_frame_cache,
xxx_prev_register for code that does the stack unwinding.

Anyway, the AIX/RS6000/POWER support in gdb really could use some
loving care.  AFAIK almost none of the gdb developers actually have
access to an AIX system.  So I'm not sure we'll be able to help you.

Mark

Re: stack unwinding on aix

[Kamal R. Prasad]

--- Mark Kettenis <mark.kettenis@xs4all.nl> wrote:

>    Date: Mon, 20 Jun 2005 23:25:50 -0700 (PDT)
>    From: "Kamal R. Prasad" <kamalpr@yahoo.com>
> 
>    Hello,
> 
>     I am trying to locate a piece of code in gdb 6.3
>    which does srack unwinding in AIX (5.3). When
>    unwinding the stack in my C code, I noticed a lot
> of
>    dummy frames whose pc points to the data segment
>    and/or outside th text segment(s). Can someone
> tell me
>    how gdb identifies such dummy frames and wherein
> the
>    code base it is? rs6000-tdep.c contains some algo
> for
>    frameless function detection etc.., but that
> isn't all
>    to it.
> 
> I'm afraid the AIX/RS6000/POWER code is suffering
> from quite a bit of
> bit-rot.  It's a bit of a mess, so I can't blame you
> for failing to
> understand the code.  The sparc, vax or m88k code
> might be much easier
> for you to understand..  Look frame functions name
> xxx_frame_cache,
> xxx_prev_register for code that does the stack
> unwinding.
> 
Doing the stack unwinding is the easier part. The
difficult part is identifying intermediate aka dummy
frames.I believe some dummyframes get introduced due
to late binding.
> Anyway, the AIX/RS6000/POWER support in gdb really
> could use some
> loving care.  AFAIK almost none of the gdb
> developers actually have
> access to an AIX system.  So I'm not sure we'll be
> able to help you.
> 
gdb actually works fine on AIX -and Im looking to
import existing functionality from gdb to my s/w, not
re-work gdb which you seem to be implying. I have a
set of AIX systems at the workplace, but Im not sure
if I can give outsiders access for security reasons.
Is  skip_prologue() the core of functionality that
identifies what to do with a frame?

regards
-kamal

> Mark
> 


------------------------------------------------------------
Kamal R. Prasad
UNIX systems consultant 
http://members.fortunecity.com/kamalp
kamalp@acm.org

In theory, there is no difference between theory and practice. In practice, there is.
------------------------------------------------------------


		
____________________________________________________ 
Yahoo! Sports 
Rekindle the Rivalries. Sign up for Fantasy Football 
http://football.fantasysports.yahoo.com