PR21441, Unnecessary padding of .eh_frame section

Until all .eh_frame sections have been edited we don't know their
sizes.  So it isn't possible to properly decide whether a non-empty
.eh_frame section follows a given section until editing is complete.

bfd/
	PR 21441
	* elf-eh-frame.c (_bfd_elf_discard_section_eh_frame): Don't add
	alignment padding here.
	* elflink.c (bfd_elf_discard_info): Add .eh_frame padding here
	in a reverse pass over sections.
ld/
	PR 21441
	* testsuite/ld-x86-64/pr21038a.d: Adjust.
	* testsuite/ld-x86-64/pr21038a-now.d: Adjust.

1 files changed, 29 insertions, 0 deletions

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 424de21..f9886dc 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -13836,6 +13836,7 @@ bfd_elf_discard_info (bfd *output_bfd, struct bfd_link_info *info)
     {
       asection *i;
       int eh_changed = 0;
+      unsigned int eh_alignment;
 
       for (i = o->map_head.s; i != NULL; i = i->map_head.s)
 	{
@@ -13861,6 +13862,34 @@ bfd_elf_discard_info (bfd *output_bfd, struct bfd_link_info *info)
 
 	  fini_reloc_cookie_for_section (&cookie, i);
 	}
+      eh_alignment = 1 << o->alignment_power;
+      if (eh_alignment > 4)
+	{
+	  /* Skip over zero terminator, and prevent empty sections
+	     from adding alignment padding at the end.  */
+	  for (i = o->map_tail.s; i != NULL; i = i->map_tail.s)
+	    if (i->size == 0)
+	      i->flags |= SEC_EXCLUDE;
+	    else if (i->size > 4)
+	      break;
+	  /* The last non-empty eh_frame section doesn't need padding.  */
+	  if (i != NULL)
+	    i = i->map_tail.s;
+	  /* Any prior sections must pad the last FDE out to the
+	     output section alignment.  Otherwise we might have zero
+	     padding between sections, which would be seen as a
+	     terminator.  */
+	  for (; i != NULL; i = i->map_tail.s)
+	    {
+	      bfd_size_type size = (i->size + eh_alignment - 1) & -eh_alignment;
+	      if (i->size != size)
+		{
+		  i->size = size;
+		  changed = 1;
+		  eh_changed = 1;
+		}
+	    }
+	}
       if (eh_changed)
 	elf_link_hash_traverse (elf_hash_table (info),
 				_bfd_elf_adjust_eh_frame_global_symbol, NULL);