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Re: Question about _dl_debug_state and new glibc
On Mon, Oct 11, 2004 at 09:13:41PM +0200, Mark Kettenis wrote:
> Date: Mon, 11 Oct 2004 13:55:25 -0400
> From: Daniel Jacobowitz <drow@false.org>
>
> On Mon, Oct 11, 2004 at 10:46:47AM -0700, Kevin Buettner wrote:
> > On Mon, 11 Oct 2004 10:22:07 -0700
> > Randolph Chung <randolph@tausq.org> wrote:
> >
> > > I've been away from gdb for a bit, so hopefully this is not something
> > > simple I missed while I've been away :)
> > >
> > > It appears that newer versions of glibc now marks the _dl_debug_state
> > > function as hidden, making it not visible to gdb. This breaks the
> > > solib tracking code in solib-svr4.c.....
> > >
> > > Looking at the docs, it looks like the "proper" way for gdb to do this
> > > is to look up the r_debug symbol and use the r_brk member to locate
> > > _dl_debug_state's address. is there any particular reason why we don't
> > > do this in gdb?
>
> Only for static executables usually; for dynamic executables it's
> supposed to be DT_DEBUG if that's available. Same difference.
>
> Hey wake up Daniel. Static executables don't have shared libraries.
Oddly enough, in glibc they can - and often do. There's a static
version of the runtime linker included, and things like dlopen work -
and internal libc functionality like NSS (gethostname, etc.) and gconv
use it.
Also, there are architectures where DT_DEBUG is missing. I think MIPS
may be one. Or maybe I'm misremembering this bit.
> I suppose this is just something that has never been completely
> implemented. Somehow I think the dynamic linker was supposed to trap
> just after initializing r_debug and setting DT_DEBUG if it was being
> traced, perhaps if it noticed that DT_DEBUG was set to some special
> value by the debugger. Perhaps we'll know when "Open Solaris" is
> released.
Makes sense to me. Do any of the BSDs support using r_debug this way,
or do they export _dl_debug_state also?
> I see it hasn't been exported since March. Blech.
>
> So we should ask the glibc developers to unhide _dl_debug_state.
I agree.
--
Daniel Jacobowitz