Discard zero address range eh_frame FDEs

These are useless because they can't match any address.  In fact,
worse than useless because the .eh_frame_hdr lookup table matching
addresses to FDEs does not contain information about the FDE range.
The table is sorted by address;  Range is inferred by the address
delta from one entry to the next.  So if a zero address range FDE is
followed by a normal non-zero range FDE for the same address,
everything is good.  However, the qsort could just as easily sort the
FDEs in the other order, in which case the normal FDE would
effectively be seen to have a zero range.

bfd/
	PR 17447
	* elf-bfd.h (struct eh_cie_fde): Comment re NULL u.fde.cie_inf.
	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Mark zero address
	range FDEs for discarding.
	(vma_compare): Sort on range after address.
	(_bfd_elf_gc_mark_fdes): Test for NULL u.fde.cie_inf.
	(_bfd_elf_discard_section_eh_frame): Likewise.  Write "FDE" in
	error message rather than "fde".
	(_bfd_elf_write_section_eh_frame_hdr): Write "PC" and "FDE" in
	error message.
ld/testsuite/
	* ld-elf/eh1.s: Don't create FDEs with zero address ranges.
	* ld-elf/eh3.s: Likewise.
	* ld-elf/eh1.d, * ld-elf/eh2.d, * ld-elf/eh3.d: Adjust.
	* ld-mips-elf/eh-frame1-n32.d: Warning match update.
	* ld-mips-elf/eh-frame1-n64.d: Likewise.
	* ld-mips-elf/eh-frame2-n32.d: Likewise.
	* ld-mips-elf/eh-frame2-n64.d: Likewise.

3 files changed, 35 insertions, 6 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index e4445dc..dd59324 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,16 @@
+2014-10-04  Alan Modra  <amodra@gmail.com>
+
+	PR 17447
+	* elf-bfd.h (struct eh_cie_fde): Comment re NULL u.fde.cie_inf.
+	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Mark zero address
+	range FDEs for discarding.
+	(vma_compare): Sort on range after address.
+	(_bfd_elf_gc_mark_fdes): Test for NULL u.fde.cie_inf.
+	(_bfd_elf_discard_section_eh_frame): Likewise.  Write "FDE" in
+	error message rather than "fde".
+	(_bfd_elf_write_section_eh_frame_hdr): Write "PC" and "FDE" in
+	error message.
+
 2014-09-29  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/17440
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index dc343ec..b2feee3 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -280,7 +280,9 @@ struct eh_cie_fde
 
 	 If REMOVED == 0, this is the CIE that we have chosen to use for
 	 the output FDE.  The CIE's REMOVED field is also 0, but the CIE
-	 might belong to a different .eh_frame input section from the FDE.  */
+	 might belong to a different .eh_frame input section from the FDE.
+
+	 May be NULL to signify that the FDE should be discarded.  */
       struct eh_cie_fde *cie_inf;
       struct eh_cie_fde *next_for_section;
     } fde;
diff --git a/bfd/elf-eh-frame.c b/bfd/elf-eh-frame.c
index b32add3..331570a 100644
--- a/bfd/elf-eh-frame.c
+++ b/bfd/elf-eh-frame.c
@@ -808,6 +808,16 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
 	  length = get_DW_EH_PE_width (cie->fde_encoding, ptr_size);
 	  REQUIRE (skip_bytes (&buf, end, 2 * length));
 
+	  SKIP_RELOCS (buf - length);
+	  if (!GET_RELOC (buf - length)
+	      && read_value (abfd, buf - length, length, FALSE) == 0)
+	    {
+	      (*info->callbacks->minfo)
+		(_("discarding zero address range FDE in %B(%A).\n"),
+		 abfd, sec);
+	      this_inf->u.fde.cie_inf = NULL;
+	    }
+
 	  /* Skip the augmentation size, if present.  */
 	  if (cie->augmentation[0] == 'z')
 	    REQUIRE (read_uleb128 (&buf, end, &length));
@@ -959,7 +969,7 @@ _bfd_elf_gc_mark_fdes (struct bfd_link_info *info, asection *sec,
       /* At this stage, all cie_inf fields point to local CIEs, so we
 	 can use the same cookie to refer to them.  */
       cie = fde->u.fde.cie_inf;
-      if (!cie->u.cie.gc_mark)
+      if (cie != NULL && !cie->u.cie.gc_mark)
 	{
 	  cie->u.cie.gc_mark = 1;
 	  if (!mark_entry (info, eh_frame, cie, gc_mark_hook, cookie))
@@ -1137,7 +1147,7 @@ _bfd_elf_discard_section_eh_frame
       /* There should only be one zero terminator, on the last input
 	 file supplying .eh_frame (crtend.o).  Remove any others.  */
       ent->removed = sec->map_head.s != NULL;
-    else if (!ent->cie)
+    else if (!ent->cie && ent->u.fde.cie_inf != NULL)
       {
 	bfd_boolean keep;
 	if ((sec->flags & SEC_LINKER_CREATED) != 0 && cookie->rels == NULL)
@@ -1170,7 +1180,7 @@ _bfd_elf_discard_section_eh_frame
 		   since it is affected by runtime relocations.  */
 		hdr_info->table = FALSE;
 		(*info->callbacks->einfo)
-		  (_("%P: fde encoding in %B(%A) prevents .eh_frame_hdr"
+		  (_("%P: FDE encoding in %B(%A) prevents .eh_frame_hdr"
 		     " table being created.\n"), abfd, sec);
 	      }
 	    ent->removed = 0;
@@ -1725,6 +1735,10 @@ vma_compare (const void *a, const void *b)
     return 1;
   if (p->initial_loc < q->initial_loc)
     return -1;
+  if (p->range > q->range)
+    return 1;
+  if (p->range < q->range)
+    return -1;
   return 0;
 }
 
@@ -1821,7 +1835,7 @@ _bfd_elf_write_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
 		  && (hdr_info->array[i].initial_loc
 		      != sec->output_section->vma + val))
 		(*info->callbacks->einfo)
-		  (_("%X%P: .eh_frame_hdr table[%u] pc overflow.\n"), i);
+		  (_("%X%P: .eh_frame_hdr table[%u] PC overflow.\n"), i);
 	      bfd_put_32 (abfd, val, contents + EH_FRAME_HDR_SIZE + i * 8 + 4);
 
 	      val = hdr_info->array[i].fde - sec->output_section->vma;
@@ -1830,7 +1844,7 @@ _bfd_elf_write_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
 		  && (hdr_info->array[i].fde
 		      != sec->output_section->vma + val))
 		(*info->callbacks->einfo)
-		  (_("%X%P: .eh_frame_hdr table[%u] fde overflow.\n"), i);
+		  (_("%X%P: .eh_frame_hdr table[%u] FDE overflow.\n"), i);
 	      bfd_put_32 (abfd, val, contents + EH_FRAME_HDR_SIZE + i * 8 + 8);
 
 	      if (i != 0