Re: [RFA/solib-svr4] use AT_BASE auxiliary entry to compute load base address

[Daniel Jacobowitz <drow@false.org>]

On Wed, Sep 12, 2007 at 02:18:05PM -0700, Joel Brobecker wrote:
> Hello,
> 
> I came across an unexpected issue on sparc-solaris 2.9, where I tried
> to attach to an Ada program. When I later did a "continue", the debugger
> error'ed out saying:
> 
>     (gdb) c
>     Continuing.
>     Warning:
>     Cannot insert breakpoint -1.
>     Error accessing memory address 0xff36159c: I/O error.

So, it has attached to the program and decided that it's at the start
address.  That means we tried this:

      /* On a running target, we can get the dynamic linker's base
         address from the shared library table.  */
      solib_add (NULL, 0, &current_target, auto_solib_add);
      so = master_so_list ();
      while (so)
...

and did not find any loaded libraries or else did not find the
interpreter in the list.  That's strange and almost certainly
indicates a bug that we should fix.  The loader should have
been in the list at that point.  Maybe it has a different
filename in the list than in .interp?

If you have time, I would recommend looking into this more.

> I think that the problem is that we're computing the wrong base load
> address in solib-svr4.c. As it turned out, there was a "TODO" hint
> added by Daniel that suggested using the AT_BASE auxiliary entry.
> The attached patch attempts to do that.
> 
> 2007-09-12  Joel Brobecker  <brobecker@adacore.com>
> 
>         * solib-svr4.c: Add include of "auxv.h".
>         (enable_break): Use the AT_BASE auxiliary entry if available.
>         * Makefile.in (solib-svr4.o): Update dependencies.

This patch, independently, is a good idea and I'm glad you did it.
It's OK.

-- 
Daniel Jacobowitz
CodeSourcery