elf: Add _dl_find_object function

It can be used to speed up the libgcc unwinder, and the internal
_dl_find_dso_for_object function (which is used for caller
identification in dlopen and related functions, and in dladdr).

_dl_find_object is in the internal namespace due to bug 28503.
If libgcc switches to _dl_find_object, this namespace issue will
be fixed.  It is located in libc for two reasons: it is necessary
to forward the call to the static libc after static dlopen, and
there is a link ordering issue with -static-libgcc and libgcc_eh.a
because libc.so is not a linker script that includes ld.so in the
glibc build tree (so that GCC's internal -lc after libgcc_eh.a does
not pick up ld.so).

It is necessary to do the i386 customization in the
sysdeps/x86/bits/dl_find_object.h header shared with x86-64 because
otherwise, multilib installations are broken.

The implementation uses software transactional memory, as suggested
by Torvald Riegel.  Two copies of the supporting data structures are
used, also achieving full async-signal-safety.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/elf/dl-open.c b/elf/dl-open.c
index 4f4d72e325..a4ad81e9cb 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -36,6 +36,7 @@
 #include <array_length.h>
 #include <libc-early-init.h>
 #include <gnu/lib-names.h>
+#include <dl-find_object.h>
 
 #include <dl-dst.h>
 #include <dl-prop.h>
@@ -731,6 +732,10 @@ dl_open_worker_begin (void *a)
      objects.  */
   update_scopes (new);
 
+  if (!_dl_find_object_update (new))
+    _dl_signal_error (ENOMEM, new->l_libname->name, NULL,
+		      N_ ("cannot allocate address lookup data"));
+
   /* FIXME: It is unclear whether the order here is correct.
      Shouldn't new objects be made available for binding (and thus
      execution) only after there TLS data has been set up fully?