On Saturday 09 August 2008 13:11:16, Mark Kettenis wrote:
> > From: Pedro Alves <pedro@codesourcery.com>
> > Date: Sat, 9 Aug 2008 12:27:34 +0100
> >
> > On Saturday 09 August 2008 09:32:57, Mark Kettenis wrote:
> > > > From: Pedro Alves <pedro@codesourcery.com>
> > >
> > > Hmm, it is unfortunate that a process ID of 0 is "verboten", since
> > > that's what you are really looking at with "target kvm".  And it
> > > should be possible for me to actually make all the running processes
> > > visible as kernel "threads".
> > >
> > >
> > > I guess your diff is right, although I'd prefer a less arbitrary ptid
> > > to be used.  Would something like ptid_build(0, 1, 0) work?
> >
> > I'd prefer to get away without pid == 0.  I'm going to
> > introduce later a "struct inferior" which holds an "int pid", and
> > we will match a ptid to a struct inferior by its ptid.pid.
> > I'd rather avoid having an inferior with pid == 0.
> >
> > Does something like this work for you?
>
> Something like that'd work fine for the OpenBSD kernel.

> Sure, I'd just think you should use something that's a bit less
> arbitrary than 42000 (which could be confused with a real process ID)
> here.  

Eh, 42 carries some history.  :-)  It was used in several targets already,
even before I started changing then to use ptid(pid,0,tid), and always
registering a thread.  monitor used 42000, remote used 42000, remote-sim
used 42, go32-nat.c uses 42.  I just thought that carrying it around
would make it easier to spot what it is.

> I see that remote.c uses negative numbers for special cases. 
> Would using -1 or -2 work for you?

Those are in the tid field, which I just carried around when I
made the remote target use ptid(pid,0,tid) for threads instead
of ptid(tid,0,0).  The magic is in using lwp != 0.  The
special -1,-2 numbers have has some binding to the remote
stub current thread.

Let's not use -1, as that conflicts a bit with the special
ptid(-1,0,0) (aka, minus_one_ptid).

I actually have a patchlet in my series to bring back the 42000:

 remote.c:
   /* Take advantage of the fact that the LWP field is not used, to tag
      special ptids with it set to != 0.  */
 -  magic_null_ptid = ptid_build (0, 1, -1);
 -  not_sent_ptid = ptid_build (0, 1, -2);
 -  any_thread_ptid = ptid_build (0, 1, 0);
 +  magic_null_ptid = ptid_build (42000, 1, -1);
 +  not_sent_ptid = ptid_build (42000, 1, -2);
 +  any_thread_ptid = ptid_build (42000, 1, 0);

I guess we're numerically converging :-)

How about the attached?

With your fix for the %eip in, I now get,

 (gdb) tar kvm
 #0  0xd034ee05 in ?? ()
 (gdb) info threads
 * 1 <kvm>  0xd034ee05 in ?? ()

OK?

-- 
Pedro Alves