elf: Rework exception handling in the dynamic loader [BZ #25486]

The old exception handling implementation used function interposition
to replace the dynamic loader implementation (no TLS support) with the
libc implementation (TLS support).  This results in problems if the
link order between the dynamic loader and libc is reversed (bug 25486).

The new implementation moves the entire implementation of the
exception handling functions back into the dynamic loader, using
THREAD_GETMEM and THREAD_SETMEM for thread-local data support.
These depends on Hurd support for these macros, added in commit
b65a82e4e757c1e6cb7073916 ("hurd: Add THREAD_GET/SETMEM/_NC").

One small obstacle is that the exception handling facilities are used
before the TCB has been set up, so a check is needed if the TCB is
available.  If not, a regular global variable is used to store the
exception handling information.

Also rename dl-error.c to dl-catch.c, to avoid confusion with the
dlerror function.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/nptl/descr.h b/nptl/descr.h
index 5cacb28..0fa0e48 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -390,6 +390,9 @@ struct pthread
      masked.)  */
   internal_sigset_t sigmask;
 
+  /* Used by the exception handling implementation in the dynamic loader.  */
+  struct rtld_catch *rtld_catch;
+
   /* Indicates whether is a C11 thread created by thrd_creat.  */
   bool c11;