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[RFHelp] Linux, threads, and regsets in thread_db
- To: gdb at sources dot redhat dot com
- Subject: [RFHelp] Linux, threads, and regsets in thread_db
- From: Daniel Jacobowitz <drow at mvista dot com>
- Date: Mon, 24 Sep 2001 21:28:08 -0400
I spent a while this summer making thread debugging work on some more
non-x86 targets, with great frustration. Eventually I reached the
decision that my problem was in fact a glibc bug; the attached messages
explain it. Ulrich has categorically (and without explanation, when
asked. sigh.) refused the patch.
Could someone on this list at least sanity check my patch? I have a
(disgusting) workaround for GDB if the header is not changed, but I'd
much rather someone convince Ulrich that I'm not crazy. Especially
since I can not get the workaround to compile without warnings. C
behaves badly in the presence of casts to/from array types.
----- Forwarded message from Daniel Jacobowitz <dmj+@andrew.cmu.edu> -----
Date: Mon, 18 Jun 2001 12:06:08 -0700
From: Daniel Jacobowitz <dmj+@andrew.cmu.edu>
Subject: gregset vs prgregset vs elf_gregset in thread_db
To: libc-alpha@sources.redhat.com
Mail-Followup-To: libc-alpha@sources.redhat.com
The thread-db routines are defined to take arguments of type 'prgregset_t'.
On about half the supported architectures, prgregset_t is typedef'd to be
'gregset_t'; on the other half it is 'elf_gregset_t'. I don't know where
the gregset_t definitions came from, especially on platforms that have
always been ELF, but they are substantially less useful than their elf
counterparts - what we really want to fill in is the data we can get from
ptrace, and pt_regs is usually fairly similar to an elf_gregset_t and an
elf_fpregset_t.
For instance, on PowerPC the NIP is not in any of r0 - r31, and a gregset_t
only has 32 elements. No way to convey the thread's NIP, which makes
debugging all but meaningless.
The only consumer of the prgregset_t and prfpregset_t types is thread-db.
Is there any objection to changing them to the elf_* variants, and possibly
bumping the thread-db soname? Although I'm not sure the latter is even
necessary; gdb is the only consumer of thread-db I've ever found on linux,
and it doesn't work with threads on the architectures affected yet anyway.
--
Daniel Jacobowitz Debian GNU/Linux Developer
Monta Vista Software Debian Security Team
----- End forwarded message -----
----- Forwarded message from Daniel Jacobowitz <dmj+@andrew.cmu.edu> -----
Date: Tue, 26 Jun 2001 22:53:23 -0700
From: Daniel Jacobowitz <dmj+@andrew.cmu.edu>
Subject: Re: gregset vs prgregset vs elf_gregset in thread_db
To: Geoff Keating <geoffk@redhat.com>
Cc: libc-alpha@sources.redhat.com
Mail-Followup-To: Geoff Keating <geoffk@redhat.com>,
libc-alpha@sources.redhat.com
On Tue, Jun 26, 2001 at 09:59:32AM -0700, Geoff Keating wrote:
> > Date: Mon, 25 Jun 2001 22:15:37 -0700
> > From: Daniel Jacobowitz <dmj+@andrew.cmu.edu>
>
> > On Mon, Jun 25, 2001 at 10:25:48PM -0700, Geoff Keating wrote:
> > > I don't believe anything other than gdb uses these structures. They
> > > don't reflect anything that the kernel produces, do they?
> >
> > That's right. They're solely an interface for debuggers, and I do not
> > know of any Linux debugger other than gdb which uses them, so I figure
> > changing them to be more convenient to gdb would be a reasonable thing.
>
> That's what I'd thought. In that case, they can be changed in any way
> that gdb finds convenient.
In that case, is this patch OK?
2001-06-26 Daniel Jacobowitz <dan@debian.org>
* sysdeps/unix/sysv/linux/alpha/sys/procfs.h: Change prgregset_t
and prfpregset_t to match their elf counterparts.
* sysdeps/unix/sysv/linux/ia64/sys/procfs.h: Likewise.
* sysdeps/unix/sysv/linux/mips/sys/procfs.h: Likewise.
* sysdeps/unix/sysv/linux/sys/procfs.h: Likewise.
Index: sysdeps/unix/sysv/linux/alpha/sys/procfs.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/alpha/sys/procfs.h,v
retrieving revision 1.7
diff -u -r1.7 procfs.h
--- procfs.h 1999/11/18 00:11:49 1.7
+++ procfs.h 2001/06/27 05:48:39
@@ -99,8 +99,8 @@
typedef void *psaddr_t;
/* Register sets. Linux has different names. */
-typedef gregset_t prgregset_t;
-typedef fpregset_t prfpregset_t;
+typedef elf_gregset_t prgregset_t;
+typedef elf_fpregset_t prfpregset_t;
/* We don't have any differences between processes and threads,
therefore habe only ine PID type. */
Index: sysdeps/unix/sysv/linux/ia64/sys/procfs.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/ia64/sys/procfs.h,v
retrieving revision 1.1
diff -u -r1.1 procfs.h
--- procfs.h 2000/06/20 03:34:47 1.1
+++ procfs.h 2001/06/27 05:48:40
@@ -104,8 +104,8 @@
typedef void *psaddr_t;
/* Register sets. Linux has different names. */
-typedef gregset_t prgregset_t;
-typedef fpregset_t prfpregset_t;
+typedef elf_gregset_t prgregset_t;
+typedef elf_fpregset_t prfpregset_t;
/* We don't have any differences between processes and threads,
therefore habe only ine PID type. */
Index: sysdeps/unix/sysv/linux/mips/sys/procfs.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/mips/sys/procfs.h,v
retrieving revision 1.6
diff -u -r1.6 procfs.h
--- procfs.h 2000/01/10 14:27:50 1.6
+++ procfs.h 2001/06/27 05:48:40
@@ -101,8 +101,8 @@
typedef void *psaddr_t;
/* Register sets. Linux has different names. */
-typedef gregset_t prgregset_t;
-typedef fpregset_t prfpregset_t;
+typedef elf_gregset_t prgregset_t;
+typedef elf_fpregset_t prfpregset_t;
/* We don't have any differences between processes and threads,
therefore habe only ine PID type. */
Index: sysdeps/unix/sysv/linux/sys/procfs.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/sys/procfs.h,v
retrieving revision 1.11
diff -u -r1.11 procfs.h
--- procfs.h 1999/11/15 07:59:41 1.11
+++ procfs.h 2001/06/27 05:48:40
@@ -99,8 +99,8 @@
typedef void *psaddr_t;
/* Register sets. Linux has different names. */
-typedef gregset_t prgregset_t;
-typedef fpregset_t prfpregset_t;
+typedef elf_gregset_t prgregset_t;
+typedef elf_fpregset_t prfpregset_t;
/* We don't have any differences between processes and threads,
therefore habe only ine PID type. */
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer
----- End forwarded message -----
----- Forwarded message from Ulrich Drepper <drepper@redhat.com> -----
Date: 14 Sep 2001 19:56:47 -0700
From: Ulrich Drepper <drepper@redhat.com>
Subject: Re: gregset vs prgregset vs elf_gregset in thread_db
To: Daniel Jacobowitz <drow@mvista.com>
Cc: Geoff Keating <geoffk@redhat.com>, libc-alpha@sources.redhat.com
Reply-To: drepper@cygnus.com (Ulrich Drepper)
Daniel Jacobowitz <drow@mvista.com> writes:
> I posted this patch three months ago and no one objected; could it
> please be applied?
There is absolutely no reason to apply this.
--
---------------. ,-. 1325 Chesapeake Terrace
Ulrich Drepper \ ,-------------------' \ Sunnyvale, CA 94089 USA
Red Hat `--' drepper at redhat.com `------------------------
----- End forwarded message -----
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer