Re: Question about _dl_debug_state and new glibc

[Kevin Buettner <kevinb at redhat dot com>]

On Mon, 11 Oct 2004 13:55:25 -0400
Daniel Jacobowitz <drow@false.org> wrote:

> On Mon, Oct 11, 2004 at 10:46:47AM -0700, Kevin Buettner wrote:
>
> > I can't think of any reason.  I'm guessing that it was more expedient
> > for the original authors of the code to do it the way it was done.
> > In any case, I know of no reason not to change it so that it's done
> > "properly".
> 
> We set the breakpoint on _dl_debug_state before starting the inferior.
> _dl_debug_initialize initializes _r_debug somewhat later...  I'm not
> sure how it is supposed to be used.  Do either of you know?

Ah!  Perhaps that's the reason why _dl_debug_state was used directly.

I ran into this problem when I wrote the FR-V's solib code.  (Due to
the fact that text and data are independetly relocated, the code in
solib-svr4.c couldn't be used.) The symbol in question was not
exported and could only be accessed from the r_debug struct.  But as you
say, it's value wasn't immediately available.  So, we set the solib
event breakpoint on the executable's entry point (probably _start). 
Once this breakpoint was hit, the data structures in question had been
initialized, and so we reset it to the address determined by examining
the r_debug struct.

I suspect that a similar strategy could be used for solib-svr4.c.

Kevin