PR27719, lang_mark_undefineds trashes memory

It's not enough to test that the output is ELF before casting
bfd_link_hash_entry to elf_link_hash_entry.  Some ELF targets (d30v,
dlx, pj, s12z, xgate) use the generic linker support in bfd/linker.c
and thus their symbols are of type generic_link_hash_entry.

Not all of the places this patch touches can result in wrong accesses,
but I thought it worth ensuring that all occurrences of
elf_link_hash_entry in ld/ were obviously correct.

	PR 27719
	* ldlang.c (lang_mark_undefineds, undef_start_stop): Test that
	the symbol hash table is the correct type before accessing
	elf_link_hash_entry symbols.
	* plugin.c (is_visible_from_outside): Likewise.
	* emultempl/armelf.em (ld${EMULATION_NAME}_finish): Likewise.
	* emultempl/solaris2.em (elf_solaris2_before_allocation): Likewise.

5 files changed, 16 insertions, 5 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index c07105d..aad02a2 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,13 @@
+2021-04-12  Alan Modra  <amodra@gmail.com>
+
+	PR 27719
+	* ldlang.c (lang_mark_undefineds, undef_start_stop): Test that
+	the symbol hash table is the correct type before accessing
+	elf_link_hash_entry symbols.
+	* plugin.c (is_visible_from_outside): Likewise.
+	* emultempl/armelf.em (ld${EMULATION_NAME}_finish): Likewise.
+	* emultempl/solaris2.em (elf_solaris2_before_allocation): Likewise.
+
 2021-04-09  Alan Modra  <amodra@gmail.com>
 
 	* testsuite/ld-powerpc/inlinepcrel-1.d: Update expected output.
diff --git a/ld/emultempl/armelf.em b/ld/emultempl/armelf.em
index bcb60d2..7aec17e 100644
--- a/ld/emultempl/armelf.em
+++ b/ld/emultempl/armelf.em
@@ -463,7 +463,7 @@ gld${EMULATION_NAME}_finish (void)
     {
       struct elf_link_hash_entry * eh;
 
-      if (!entry_symbol.name)
+      if (!entry_symbol.name || !is_elf_hash_table (link_info.hash))
 	return;
 
       h = bfd_link_hash_lookup (link_info.hash, entry_symbol.name,
diff --git a/ld/emultempl/solaris2.em b/ld/emultempl/solaris2.em
index 9fb739c..e2b4fd63b 100644
--- a/ld/emultempl/solaris2.em
+++ b/ld/emultempl/solaris2.em
@@ -64,7 +64,8 @@ elf_solaris2_before_allocation (void)
   const char **sym;
 
   /* Do this for both executables and shared objects.  */
-  if (!bfd_link_relocatable (&link_info))
+  if (!bfd_link_relocatable (&link_info)
+      && is_elf_hash_table (link_info.hash))
     {
       for (sym = global_syms; *sym != NULL; sym++)
 	{
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 8910899..37b64c8 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -4009,7 +4009,7 @@ lang_mark_undefineds (void)
 {
   ldlang_undef_chain_list_type *ptr;
 
-  if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
+  if (is_elf_hash_table (link_info.hash))
     for (ptr = ldlang_undef_chain_list_head; ptr != NULL; ptr = ptr->next)
       {
 	struct elf_link_hash_entry *h = (struct elf_link_hash_entry *)
@@ -6822,7 +6822,7 @@ undef_start_stop (struct bfd_link_hash_entry *h)
 	}
       h->type = bfd_link_hash_undefined;
       h->u.undef.abfd = NULL;
-      if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
+      if (is_elf_hash_table (link_info.hash))
 	{
 	  const struct elf_backend_data *bed;
 	  struct elf_link_hash_entry *eh = (struct elf_link_hash_entry *) h;
diff --git a/ld/plugin.c b/ld/plugin.c
index adaba32..98a83bc 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -636,7 +636,7 @@ is_visible_from_outside (struct ld_plugin_symbol *lsym,
 				   blhe->root.string))
 	return false;
       /* Only ELF symbols really have visibility.  */
-      if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
+      if (is_elf_hash_table (link_info.hash))
 	{
 	  struct elf_link_hash_entry *el = (struct elf_link_hash_entry *)blhe;
 	  int vis = ELF_ST_VISIBILITY (el->other);