Make __start/__stop symbols protected visibility

They can't be hidden visibility since apparently people use dlsym to
look them up.

bfd/
	PR ld/21964
	* elf-bfd.h (SYMBOLIC_BIND): Return TRUE for __start/__stop symbols.
	* elflink.c (bfd_elf_define_start_stop): Rewrite.
ld/
	PR ld/21964
	* testsuite/ld-elf/pr21562a.d: Update for changed start/stop symbols.
	* testsuite/ld-elf/pr21562b.d: Likewise.
	* testsuite/ld-elf/pr21562c.d: Likewise.
	* testsuite/ld-elf/pr21562d.d: Likewise.
	* testsuite/ld-elf/pr21562e.d: Likewise.
	* testsuite/ld-elf/pr21562f.d: Likewise.
	* testsuite/ld-elf/pr21562g.d: Likewise.
	* testsuite/ld-elf/pr21562h.d: Likewise.
	* testsuite/ld-elf/pr21562i.d: Likewise.
	* testsuite/ld-elf/pr21562j.d: Likewise.
	* testsuite/ld-elf/pr21562k.d: Likewise.
	* testsuite/ld-elf/pr21562l.d: Likewise.
	* testsuite/ld-elf/pr21562m.d: Likewise.
	* testsuite/ld-elf/pr21562n.d: Likewise.
	* testsuite/ld-elf/sizeofa.d: Likewise.
	* testsuite/ld-elf/sizeofb.d: Likewise.
	* testsuite/ld-elf/startofa.d: Likewise.
	* testsuite/ld-elf/startofb.d: Likewise.
	* testsuite/ld-gc/pr20022.d: Likewise.
	* testsuite/ld-gc/start.d: Likewise.
	* testsuite/ld-elf/pr21964-1a.c: New file.
	* testsuite/ld-elf/pr21964-1b.c: New file.
	* testsuite/ld-elf/pr21964-2a.c: New file.
	* testsuite/ld-elf/pr21964-2b.c: New file.
	* testsuite/ld-elf/shared.exp: Run PR ld/21964 tests.

3 files changed, 33 insertions, 12 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 6badc5d..15f1a3f 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2017-08-21  Alan Modra  <amodra@gmail.com>
+	    H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/21964
+	* elf-bfd.h (SYMBOLIC_BIND): Return TRUE for __start/__stop symbols.
+	* elflink.c (bfd_elf_define_start_stop): Rewrite.
+
 2017-08-21  Hans-Peter Nilsson  <hp@bitrange.com>
 
 	PR ld/20125
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 92a8e02..83958e4 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -2802,7 +2802,9 @@ extern asection _bfd_elf_large_com_section;
    library, if any.  A unique symbol can never be bound locally.  */
 #define SYMBOLIC_BIND(INFO, H) \
     (!(H)->unique_global \
-     && ((INFO)->symbolic || ((INFO)->dynamic && !(H)->dynamic)))
+     && ((INFO)->symbolic \
+	 || (H)->start_stop \
+	 || ((INFO)->dynamic && !(H)->dynamic)))
 
 #ifdef __cplusplus
 }
diff --git a/bfd/elflink.c b/bfd/elflink.c
index f9886dc..ceacb37 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -14260,18 +14260,30 @@ struct bfd_link_hash_entry *
 bfd_elf_define_start_stop (struct bfd_link_info *info,
 			   const char *symbol, asection *sec)
 {
-  struct bfd_link_hash_entry *h;
+  struct elf_link_hash_entry *h;
 
-  h = bfd_generic_define_start_stop (info, symbol, sec);
-  if (h != NULL)
+  h = elf_link_hash_lookup (elf_hash_table (info), symbol,
+			    FALSE, FALSE, TRUE);
+  if (h != NULL
+      && (h->root.type == bfd_link_hash_undefined
+	  || h->root.type == bfd_link_hash_undefweak
+	  || (h->ref_regular && !h->def_regular)))
     {
-      struct elf_link_hash_entry *eh = (struct elf_link_hash_entry *) h;
-      eh->start_stop = 1;
-      eh->u2.start_stop_section = sec;
-      _bfd_elf_link_hash_hide_symbol (info, eh, TRUE);
-      if (ELF_ST_VISIBILITY (eh->other) != STV_INTERNAL)
-	eh->other = ((eh->other & ~ELF_ST_VISIBILITY (-1))
-		     | STV_HIDDEN);
+      h->root.type = bfd_link_hash_defined;
+      h->root.u.def.section = sec;
+      h->root.u.def.value = 0;
+      h->def_regular = 1;
+      h->def_dynamic = 0;
+      h->start_stop = 1;
+      h->u2.start_stop_section = sec;
+      if (symbol[0] == '.')
+	{
+	  /* .startof. and .sizeof. symbols are local.  */
+	  _bfd_elf_link_hash_hide_symbol (info, h, TRUE);
+	}
+      else if (ELF_ST_VISIBILITY (h->other) == STV_DEFAULT)
+	h->other = (h->other & ~ELF_ST_VISIBILITY (-1)) | STV_PROTECTED;
+      return &h->root;
     }
-  return h;
+  return NULL;
 }