Extend struct r_debug to support multiple namespaces [BZ #15971]

Glibc does not provide an interface for debugger to access libraries
loaded in multiple namespaces via dlmopen.

The current rtld-debugger interface is described in the file:

elf/rtld-debugger-interface.txt

under the "Standard debugger interface" heading.  This interface only
provides access to the first link-map (LM_ID_BASE).

1. Bump r_version to 2 when multiple namespaces are used.  This triggers
the GDB bug:

https://sourceware.org/bugzilla/show_bug.cgi?id=28236

2. Add struct r_debug_extended to extend struct r_debug into a linked-list,
where each element correlates to an unique namespace.
3. Initialize the r_debug_extended structure.  Bump r_version to 2 for
the new namespace and add the new namespace to the namespace linked list.
4. Add _dl_debug_update to return the address of struct r_debug' of a
namespace.
5. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended.
6. Provide the symbol, _r_debug, with size of struct r_debug, as an alias
of _r_debug_extended, for programs which reference _r_debug.

This fixes BZ #15971.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 650e4ed..39e0d07 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -949,7 +949,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
   /* Initialize to keep the compiler happy.  */
   const char *errstring = NULL;
   int errval = 0;
-  struct r_debug *r = _dl_debug_initialize (0, nsid);
+  struct r_debug *r = _dl_debug_update (nsid);
   bool make_consistent = false;
 
   /* Get file information.  To match the kernel behavior, do not fill