Re: System call support in reversible debugging

[Michael Snyder <msnyder at vmware dot com>]

Sean Chen wrote:
> On Sat, Nov 28, 2009 at 2:07 AM, Michael Snyder <msnyder@vmware.com> wrote:
> > These are two separate questions.  I think the one you started with
> > is can gdb record a system call, and the answer is "yes".
> >
> >
> > The issue with mmap has a lot of history, and rather than try to
> > explain it, I urge you to look up the threads which have "mmap"
> > or "sbrk" in the title) and read them.
>
> Thanks for the explanation. That is very kind of you.
>
> I am confused about the first question. How does gdb record the system
> call instructions? You know, they are in the kernel space? It seems
> that I must have made a mistake somewhere. Please help to clarify.
>
> Thanks in advance.

Sean,

I wish I understood this better -- maybe Hui will explain it more.

As I understand it, each system call is recorded as if it were a
single instruction.  Instead of 'tracing' into the system code,
we know the specific side effects for each system call, and for
instance if the syscall will write to a buffer we take a snapshot
of that buffer first.

Michael