Re: [RFC] Unified watchpoints for x86 platforms

[Kevin Buettner <kevinb at cygnus dot com>]

On Feb 15,  5:17pm, Mark Kettenis wrote:

> > > I started working on the unified support for hardware-assisted
> > > breakpoints and watchpoints on x86 platforms (see TODO).  Since I
> > > don't feel I know enough about all the aspects of this on any platform
> > > but DJGPP, I thought I'd better get the framework agreed to before I
> > > start coding.
> > > 
> > > Here's the API I suggest for use by higher-level GDB code:
> > > 
> > >   (Note: I'm not good at inventing names, so please suggest better
> > >   ones if you want.)
> > > 
> > >   int i386_hwbp_insert (int pid, CORE_ADDR addr, int len, int kind);
> 
> Is there any particular reason why you need the PID argument?  AFAICS
> it will always be equal to INFERIOR_PID, so I think we can do without
> it.  This is also true for the other i386_hwbp_* functions you're
> proposing.

I think it'd be better to not rely on ``inferior_pid''.  I would
rather see the explicitly passed.  There will come a day when GDB
is able to debug more than one process at a time and to perpetuate
reliance on inferior pid would be short sighted.

> > >   In the discussion we had back in September, Mark said that the
> > >   status register should be per thread.  Does that mean that we need
> > >   an additional argument (int tid?) to pass to HWBP_GET_STATUS?  If
> > >   so, how will this argument get into the i386_hwbp_* functions which
> > >   will call these macros?
> 
> I don't think an additional argument is needed.  When calling
> HWBP_GET_STATUS, it is the current thread that has encountered a trap,
> and INFERIOR_PID should be set appropriately.
> 
> > >   Or maybe the target end can figure out the thread id by itself with
> > >   some TIDGET(pid) magic?

Hopefully I'll find time to merge my pid/tid/lwp patch sometime soon.
When this occurs, you'll be able to extract the thread id from what is
now the pid argument.

I have read the rest of Eli's proposal as well as Mark's comments and
I agree with the rest of Mark's remarks.

Kevin