[PATCH] Fix _dl_debug_initialize

[PATCH] Fix _dl_debug_initialize

[Jakub Jelinek]

Hi!

If ld.so is prelinked and a program is executed through ld.so
(/lib*/ld-*.so --library-path whatever /the/program) and kernel
mmaps prelink at its base address, then _r_debug.r_map is NULL.
_r_debug is initialized by _dl_debug_initialize calls.  When
invoking /the/program directly, GL(dl_ns)[ns]._ns_loaded
is initialized before first call to _dl_debug_initialize,
but when invoking program using ld.so, it is non-NULL only
on the second and following _dl_debug_initialize calls.
But at that point _r_debug.r_brk is already non-zero.
If ld.so is not prelinked or kernel mmaps it elsewhere, one of
the following _dl_debug_initialize calls will have ldbase != 0
and it will be still reinitialized.  But when rtld's l_addr
is 0 (i.e. it is mmapped at the prelinked address), _dl_debug_initialize
never reinitializes it.

We talked about splitting _dl_debug_initialize into _dl_debug_initialize
and _dl_debug_query which wouldn't initialize it, just return the
struct address, while _dl_debug_initialize would reinitialize always,
but I think that just can't work in other namespaces.

The following patch is much shorter, we simply keep reinitializing
until r_map is non-NULL.  If r->r_map is non-NULL, we know r->r_brk
is also != 0.

2006-10-09  Jakub Jelinek  <jakub@redhat.com>

	* elf/dl-debug.c (_dl_debug_initialize): Check r->r_map for 0
	rather than r->r_brk.

--- libc/elf/dl-debug.c.jj	2006-10-19 17:28:01.000000000 +0200
+++ libc/elf/dl-debug.c	2006-11-09 12:04:37.000000000 +0100
@@ -54,7 +54,7 @@ _dl_debug_initialize (ElfW(Addr) ldbase,
   else
     r = &GL(dl_ns)[ns]._ns_debug;
 
-  if (r->r_brk == 0 || ldbase != 0)
+  if (r->r_map == NULL || ldbase != 0)
     {
       /* Tell the debugger where to find the map of loaded objects.  */
       r->r_version = 1	/* R_DEBUG_VERSION XXX */;

	Jakub