PR22431, powerpc64 ld segfault when .plt discarded

The fix for the PR is to not use input_section->output_section->owner
to get to the output bfd, but use the output bfd directly since it is
available nowadays in struct bfd_link_info.

I thought it worth warning when non-empty dynamic sections are
discarded too, which meant a tweak to one of the ld tests to avoid the
warning.

bfd/
	PR 22431
	* elf64-ppc.c (ppc64_elf_size_dynamic_sections): Warn on discarding
	non-empty dynamic section.
	(ppc_build_one_stub): Take elf_gp from output bfd, not output
	section owner.
	(ppc_size_one_stub, ppc64_elf_next_toc_section): Likewise.
ld/
	* testsuite/ld-elf/note-3.t: Don't discard .got.

bfd/ChangeLog

@@ -1,3 +1,12 @@
+2017-11-14  Alan Modra  <amodra@gmail.com>
+
+	PR 22431
+	* elf64-ppc.c (ppc64_elf_size_dynamic_sections): Warn on discarding
+	non-empty dynamic section.
+	(ppc_build_one_stub): Take elf_gp from output bfd, not output
+	section owner.
+	(ppc_size_one_stub, ppc64_elf_next_toc_section): Likewise.
+
 2017-11-14  Alan Modra  <amodra@gmail.com>
 
 	* elf64-ppc.c (ppc64_elf_size_stubs): Correct test for user

bfd/elf64-ppc.c

@@ -10202,6 +10202,10 @@ ppc64_elf_size_dynamic_sections (bfd *output_bfd,
 	  continue;
 	}
 
+      if (bfd_is_abs_section (s->output_section))
+	_bfd_error_handler (_("warning: discarding dynamic section %s"),
+			    s->name);
+
       if ((s->flags & SEC_HAS_CONTENTS) == 0)
 	continue;
 
@@ -10996,7 +11000,7 @@ ppc_build_one_stub (struct bfd_hash_entry *gen_entry, void *in_arg)
 	      + htab->brlt->output_section->vma);
 
       off = (dest
-	     - elf_gp (htab->brlt->output_section->owner)
+	     - elf_gp (info->output_bfd)
 	     - htab->sec_info[stub_entry->group->link_sec->id].toc_off);
 
       if (off + 0x80008000 > 0xffffffff || (off & 7) != 0)
@@ -11147,7 +11151,7 @@ ppc_build_one_stub (struct bfd_hash_entry *gen_entry, void *in_arg)
 	}
 
       off = (dest
-	     - elf_gp (plt->output_section->owner)
+	     - elf_gp (info->output_bfd)
 	     - htab->sec_info[stub_entry->group->link_sec->id].toc_off);
 
       if (off + 0x80008000 > 0xffffffff || (off & 7) != 0)
@@ -11295,7 +11299,7 @@ ppc_size_one_stub (struct bfd_hash_entry *gen_entry, void *in_arg)
 	plt = htab->elf.iplt;
       off += (plt->output_offset
 	      + plt->output_section->vma
-	      - elf_gp (plt->output_section->owner)
+	      - elf_gp (info->output_bfd)
 	      - htab->sec_info[stub_entry->group->link_sec->id].toc_off);
 
       size = plt_stub_size (htab, stub_entry, off);
@@ -11398,7 +11402,7 @@ ppc_size_one_stub (struct bfd_hash_entry *gen_entry, void *in_arg)
 	  off = (br_entry->offset
 		 + htab->brlt->output_offset
 		 + htab->brlt->output_section->vma
-		 - elf_gp (htab->brlt->output_section->owner)
+		 - elf_gp (info->output_bfd)
 		 - htab->sec_info[stub_entry->group->link_sec->id].toc_off);
 
 	  if (info->emitrelocations)
@@ -11518,7 +11522,7 @@ ppc64_elf_next_toc_section (struct bfd_link_info *info, asection *isec)
 	 output toc base plus 0x8000.  Making the input elf_gp an
 	 offset allows us to move the toc as a whole without
 	 recalculating input elf_gp.  */
-      off = htab->toc_curr - elf_gp (isec->output_section->owner);
+      off = htab->toc_curr - elf_gp (info->output_bfd);
       off += TOC_BASE_OFF;
 
       /* Die if someone uses a linker script that doesn't keep input
@@ -11547,7 +11551,7 @@ ppc64_elf_next_toc_section (struct bfd_link_info *info, asection *isec)
     }
   addr = (htab->toc_first_sec->output_offset
 	  + htab->toc_first_sec->output_section->vma);
-  off = addr - elf_gp (isec->output_section->owner) + TOC_BASE_OFF;
+  off = addr - elf_gp (info->output_bfd) + TOC_BASE_OFF;
   elf_gp (isec->owner) = off;
 
   return TRUE;

ld/ChangeLog

@@ -1,3 +1,7 @@
+2017-11-14  Alan Modra  <amodra@gmail.com>
+
+	* testsuite/ld-elf/note-3.t: Don't discard .got.
+
 2017-11-14  Alan Modra  <amodra@gmail.com>
 
 	* testsuite/ld-ifunc/ifunc.exp: Ensure non-PIC tests are really

ld/testsuite/ld-elf/note-3.t

@@ -18,6 +18,7 @@ SECTIONS
   
   .dynstr : { *(.dynstr) }
   .dynsym : { *(.dynsym) }
+  .got : { *(.got .toc) *(.igot) }
   .got.plt : { *(.got.plt) *(.igot.plt) }
   /DISCARD/ : { *(*) }
 }