elf: Support dlvsym within libc.so

This commit adds a new _dl_open_hook entry for dlvsym and implements the
function using the existing dl_lookup_symbol_x function supplied by the
dynamic loader.

A new hook variable, _dl_open_hook2, is introduced, which should make
this change suitable for backporting: For old statically linked
binaries, __libc_dlvsym will always return NULL.

1 files changed, 2 insertions, 2 deletions

diff --git a/elf/Versions b/elf/Versions
index 79ffaf73d2..3b09901f6c 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -23,9 +23,9 @@ libc {
   GLIBC_PRIVATE {
     # functions used in other libraries
     _dl_addr;
-    _dl_open_hook;
+    _dl_open_hook; _dl_open_hook2;
     _dl_sym; _dl_vsym;
-    __libc_dlclose; __libc_dlopen_mode; __libc_dlsym;
+    __libc_dlclose; __libc_dlopen_mode; __libc_dlsym; __libc_dlvsym;
 
     # Internal error handling support.  Interposes the functions in ld.so.
     _dl_signal_exception; _dl_catch_exception;