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, 10 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index 838381f562..3e3c074238 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,9 @@ Version 2.35
 
 Major new features:
 
+* Bump r_version in the debugger interface to 2 and add a new field,
+  r_next, support multiple namespaces.
+
 * Support for the C.UTF-8 locale has been added to glibc.  The locale
   supports full code-point sorting for all valid Unicode code points.  A
   limitation in the framework for fnmatch, regexec, and regcomp requires
@@ -28,7 +31,13 @@ Major new features:
 
 Deprecated and removed features, and other changes affecting compatibility:
 
-  [Add deprecations, removals and changes affecting compatibility here]
+* The r_version update in the debugger interface makes the glibc binary
+  incompatible with GDB binaries built without the following commits:
+
+  c0154a4a21a gdb: Don't assume r_ldsomap when r_version > 1 on Linux
+  4eb629d50d4 gdbserver: Check r_version < 1 for Linux debugger interface
+
+  when audit modules or dlmopen are used.
 
 Changes to build and runtime requirements: