PR13616, linker should pad executable sections with nops, not zeros

This implements padding of orphan executable sections for PowerPC.
Of course, the simple implementation of bfd_arch_ppc_nop_fill and
removing the NOP definition didn't work, with powerpc64 hitting a
testsuite failure linking to S-records.  That's because the srec
target is BFD_ENDIAN_UNKNOWN so the test of bfd_big_endian (abfd) in
default_data_link_order therefore returned false, resulting in a
little-endian nop pattern.  The rest of the patch fixes that problem
by adding a new field to bfd_link_info that can be used to determine
actual endianness on targets like srec.

	PR 13616
include/
	* bfdlink.h (struct bfd_link_info <big_endian>): New field.
bfd/
	* cpu-powerpc.c (bfd_arch_ppc_nop_fill): New function, use it
	for all ppc arch info.
	* linker.c (default_data_link_order): Pass info->big_endian to
	arch_info->fill function.
ld/
	* emulparams/elf64lppc.sh (NOP): Don't define.
	* emulparams/elf64ppc.sh (NOP): Don't define.
	* ldwrite.c (build_link_order): Use link_info.big_endian.  Move
	code determining endian to use for data_statement to..
	* ldemul.c (after_open_default): ..here.  Set link_info.big_endian.

3 files changed, 48 insertions, 3 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 5a9bfd7..74cdda4 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,11 @@
+2019-10-16  Alan Modra  <amodra@gmail.com>
+
+	PR 13616
+	* cpu-powerpc.c (bfd_arch_ppc_nop_fill): New function, use it
+	for all ppc arch info.
+	* linker.c (default_data_link_order): Pass info->big_endian to
+	arch_info->fill function.
+
 2019-10-15  Alan Modra  <amodra@gmail.com>
 
 	* elf32-m68hc1x.c (reloc_warning): Add printf attribute.
diff --git a/bfd/cpu-powerpc.c b/bfd/cpu-powerpc.c
index 4959467..6c54388 100644
--- a/bfd/cpu-powerpc.c
+++ b/bfd/cpu-powerpc.c
@@ -48,6 +48,43 @@ powerpc_compatible (const bfd_arch_info_type *a,
   /*NOTREACHED*/
 }
 
+/* Return a COUNT sized buffer filled with nops (if CODE is TRUE) or
+   zeros (if CODE is FALSE).  This is the fill used between input
+   sections for alignment.  It won't normally be executed.   */
+
+static void *
+bfd_arch_ppc_nop_fill (bfd_size_type count,
+		       bfd_boolean is_bigendian,
+		       bfd_boolean code)
+{
+  bfd_byte *fill;
+
+  if (count == 0)
+    return NULL;
+  fill = bfd_malloc (count);
+  if (fill == NULL)
+    return fill;
+
+  if (code && (count & 3) == 0)
+    {
+      static const char nop_be[4] = {0x60, 0, 0, 0};
+      static const char nop_le[4] = {0, 0, 0, 0x60};
+      const char *nop = is_bigendian ? nop_be : nop_le;
+      bfd_byte *p = fill;
+
+      while (count != 0)
+	{
+	  memcpy (p, nop, 4);
+	  p += 4;
+	  count -= 4;
+	}
+    }
+  else
+    memset (fill, 0, count);
+
+  return fill;
+}
+
 #define N(BITS, NUMBER, PRINT, DEFAULT, NEXT)		\
   {							\
     BITS,      /* Bits in a word.  */			\
@@ -61,7 +98,7 @@ powerpc_compatible (const bfd_arch_info_type *a,
     DEFAULT,						\
     powerpc_compatible,					\
     bfd_default_scan,					\
-    bfd_arch_default_fill,				\
+    bfd_arch_ppc_nop_fill,				\
     NEXT,						\
     0 /* Maximum offset of a reloc from the start of an insn.  */ \
   }
diff --git a/bfd/linker.c b/bfd/linker.c
index 143b8eb..382b69d 100644
--- a/bfd/linker.c
+++ b/bfd/linker.c
@@ -2469,7 +2469,7 @@ _bfd_default_link_order (bfd *abfd,
 
 static bfd_boolean
 default_data_link_order (bfd *abfd,
-			 struct bfd_link_info *info ATTRIBUTE_UNUSED,
+			 struct bfd_link_info *info,
 			 asection *sec,
 			 struct bfd_link_order *link_order)
 {
@@ -2489,7 +2489,7 @@ default_data_link_order (bfd *abfd,
   fill_size = link_order->u.data.size;
   if (fill_size == 0)
     {
-      fill = abfd->arch_info->fill (size, bfd_big_endian (abfd),
+      fill = abfd->arch_info->fill (size, info->big_endian,
 				    (sec->flags & SEC_CODE) != 0);
       if (fill == NULL)
 	return FALSE;