Debugging multi-threaded SSE using programs

Debugging multi-threaded SSE using programs

[Mark Kettenis]

The current version of GDB doesn't correctly support displaying the
SSE registers for debugging multi-threaded programs.  This is due to
the fact that the current version of libthread_db doesn't provide the
means to track these registers.  Browsing through the code it seems
that td_thr_getxregs(), td_thr_getxregsize() and td_thr_setxregs() are
intended to be used for supporting extra register sets.  It seems that
these calls are unused on Solaris x86.  Would it be OK to provide an
implementation of these calls for Linux x86 that manages the SSE
registers?

Mark

Re: Debugging multi-threaded SSE using programs

[Ulrich Drepper]

Mark Kettenis <kettenis@wins.uva.nl> writes:

> Would it be OK to provide an implementation of these calls for Linux
> x86 that manages the SSE registers?

Yes.  But please try to make it a bit generic so that it can be used
with the different registers extensions already out there and also has
room if there are yet more extensions to come.

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Ulrich Drepper  \    ,-------------------'   \  Sunnyvale, CA 94089 USA
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Re: Debugging multi-threaded SSE using programs

[Mark Kettenis]

   From: Ulrich Drepper <drepper@redhat.com>
   Date: 01 Sep 2001 14:34:47 -0700

   Mark Kettenis <kettenis@wins.uva.nl> writes:

   > Would it be OK to provide an implementation of these calls for Linux
   > x86 that manages the SSE registers?

   Yes.  But please try to make it a bit generic so that it can be used
   with the different registers extensions already out there and also has
   room if there are yet more extensions to come.

I did some reverse-engineering on sparc-sun-solaris2.6, and it seems
that we can punt any interpretation of these extra registers to the
debugger.  In libthread_db we should simply call ps_lgetxregsize,
ps_lgetxregs or ps_lsetxregs with the appropriate arguments, or return
an appropraite error code.  This means that we cannot zero out the
register set when a thread already terminated as we do for
td_thr_getfpregs.  So be it.  Any debugger will need to deal with it.

Since the current libthread_db doesn't require ps_lgetxregsize,
ps_lgetxregs and ps_lsetxregs, I probably should use weak references
for these functions, shouldn't I?

Mark

Re: Debugging multi-threaded SSE using programs

[Ulrich Drepper]

Mark Kettenis <kettenis@wins.uva.nl> writes:

> Since the current libthread_db doesn't require ps_lgetxregsize,
> ps_lgetxregs and ps_lsetxregs, I probably should use weak references
> for these functions, shouldn't I?

Making the references weak shouldn't be a problem and it would help in
some situations to use a new libthread_db with an old gdb.

-- 
---------------.                          ,-.   1325 Chesapeake Terrace
Ulrich Drepper  \    ,-------------------'   \  Sunnyvale, CA 94089 USA
Red Hat          `--' drepper at redhat.com   `------------------------