Re: System call support in reversible debugging

[Greg Law <glaw at undo-software dot com>]

Ok, I can't resist jumping in :)

Jakob Engblom wrote:
>  
> > Hi Michael and Hui,
> >
> > I am sorry for my late response.
> >
> > Thanks for your explanation. So we can’t treat the system calls as a
> > black box and have to understand the detailed implementation of each
> > system call. I think we need to understand every lines of the code in
> > the system calls carefully enough, and care about the difference of
> > the Linux kernel since the code of system calls might change
> > frequently. Do we have any good ways to do it?
>
> To really do this right, you should use a full-system simulator that lets you
> debug OS and user code at the same time, as it is attacking the system at the
> hardware/software interface level. 

It all depends what you want to do.

If you want to debug kernel code, then absolutely you need a full system 
approach, such as Simics or VMware offers.  Similarly if you want to 
debug the whole host.  But if you're debugging just a process (i.e. the 
classic use-case of gdb), you may not want to wind back the state of the 
entire (virtual) machine.  In which case, something like UndoDB or prec 
is more appropriate.

I don't claim either approach is superior.  It's a bit like native 
debugging versus remote debugging.  Which one makes most sense all 
depends on what it is you're trying to debug.

Greg
--
Greg Law, Undo Software                       http://undo-software.com/