No PT_INTERP when .interp is zero size

[Alan Modra]

Some targets don't set a default interpreter, resulting in an empty
.interp section unless --dynamic-linker is passed to ld.  A PT_INTERP
without a path is rather useless.

The testsuite change fixes a failure on microblaze-linux.

bfd/
	* elf.c (get_program_header_size): Don't count PT_INTERP if
	.interp is empty.
	(_bfd_elf_map_sections_to_segments): Don't create PT_INTERP if
	.interp is empty.
ld/
	* testsuite/ld-elf/pr22423.d: Pass --dynamic-linker to ld.

diff --git a/bfd/elf.c b/bfd/elf.c
index b3ce110893..fe43c9ffe7 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -4335,7 +4335,7 @@ get_program_header_size (bfd *abfd, struct bfd_link_info *info)
   segs = 2;
 
   s = bfd_get_section_by_name (abfd, ".interp");
-  if (s != NULL && (s->flags & SEC_LOAD) != 0)
+  if (s != NULL && (s->flags & SEC_LOAD) != 0 && s->size != 0)
     {
       /* If we have a loadable interpreter section, we need a
 	 PT_INTERP segment.  In this case, assume we also need a
@@ -4647,7 +4647,7 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
 	 the program headers and a PT_INTERP segment for the .interp
 	 section.  */
       s = bfd_get_section_by_name (abfd, ".interp");
-      if (s != NULL && (s->flags & SEC_LOAD) != 0)
+      if (s != NULL && (s->flags & SEC_LOAD) != 0 && s->size != 0)
 	{
 	  amt = sizeof (struct elf_segment_map);
 	  m = (struct elf_segment_map *) bfd_zalloc (abfd, amt);
diff --git a/ld/testsuite/ld-elf/pr22423.d b/ld/testsuite/ld-elf/pr22423.d
index 70bd59e399..9255c7e77b 100644
--- a/ld/testsuite/ld-elf/pr22423.d
+++ b/ld/testsuite/ld-elf/pr22423.d
@@ -1,6 +1,6 @@
 #source: start.s
 #readelf: -l -W
-#ld: -pie
+#ld: -pie --dynamic-linker=/usr/lib/ld.so.1
 #target: *-*-linux* *-*-gnu* arm*-*-uclinuxfdpiceabi
 
 #...

-- 
Alan Modra
Australia Development Lab, IBM