elf: Introduce GLRO (dl_libc_freeres), called from __libc_freeres

This will be used to deallocate memory allocated using the non-minimal
malloc.

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

elf/Makefile

@@ -68,7 +68,7 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
 rtld-routines	= rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \
   dl-error-minimal dl-conflict dl-hwcaps dl-hwcaps_split dl-hwcaps-subdirs \
   dl-usage dl-diagnostics dl-diagnostics-kernel dl-diagnostics-cpu \
-  dl-mutex
+  dl-mutex dl-libc_freeres
 all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
 
 CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables

elf/dl-libc_freeres.c

@@ -0,0 +1,24 @@
+/* Deallocating malloc'ed memory from the dynamic loader.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+
+void
+__rtld_libc_freeres (void)
+{
+}

elf/rtld.c

@@ -378,6 +378,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
     ._dl_catch_error = _rtld_catch_error,
     ._dl_error_free = _dl_error_free,
     ._dl_tls_get_addr_soft = _dl_tls_get_addr_soft,
+    ._dl_libc_freeres = __rtld_libc_freeres,
 #ifdef HAVE_DL_DISCOVER_OSVERSION
     ._dl_discover_osversion = _dl_discover_osversion
 #endif

malloc/set-freeres.c

@@ -21,6 +21,7 @@
 #include <libc-internal.h>
 #include <unwind-link.h>
 #include <dlfcn/dlerror.h>
+#include <ldsodefs.h>
 
 #include "../nss/nsswitch.h"
 #include "../libio/libioP.h"
@@ -67,6 +68,10 @@ __libc_freeres (void)
 
       call_function_static_weak (__libc_dlerror_result_free);
 
+#ifdef SHARED
+      GLRO (dl_libc_freeres) ();
+#endif
+
       for (p = symbol_set_first_element (__libc_freeres_ptrs);
            !symbol_set_end_p (__libc_freeres_ptrs, p); ++p)
         free (*p);

sysdeps/generic/ldsodefs.h

@@ -712,6 +712,10 @@ struct rtld_global_ro
      namespace.  */
   void (*_dl_error_free) (void *);
   void *(*_dl_tls_get_addr_soft) (struct link_map *);
+
+  /* Called from __libc_shared to deallocate malloc'ed memory.  */
+  void (*_dl_libc_freeres) (void);
+
 #ifdef HAVE_DL_DISCOVER_OSVERSION
   int (*_dl_discover_osversion) (void);
 #endif
@@ -1416,6 +1420,9 @@ __rtld_mutex_init (void)
 }
 #endif /* !PTHREAD_IN_LIBC */
 
+/* Implementation of GL (dl_libc_freeres).  */
+void __rtld_libc_freeres (void) attribute_hidden;
+
 void __thread_gscope_wait (void) attribute_hidden;
 # define THREAD_GSCOPE_WAIT() __thread_gscope_wait ()