PR16867, linking object with separate debug file

This teaches the DWARF2 find_line functions how to deal with separate
debug relocatable object files.  Also fixes a major bug:
When _bfd_dwarf2_slurp_debug_info was split out, place_sections ran
after .debug_info was relocated.  This defeated the whole purpose of
place_sections.  See the comment I added before place_sections.
Fixes some minor bugs too:
- place_sections didn't set VMA for alloc but non-load sections (bss).
- zero size sections can have symbols, so they need their VMA set too.
- last_vma was incorrectly adjusted.
- my last change to place_sections left VMA unchanged for .debug_info
  when the linker has mapped input to output sections, but this is
  wrong since bfd_simple_get_relocated_section_contents unmaps debug
  sections.

	PR 16867
	* dwarf2.c: Formatting.
	(struct dwarf2_debug): Make adjusted_section_count signed.
	(unset_sections): Make i signed.
	(set_debug_vma): New function.
	(place_sections): Handle separate debug object file.  Set VMA
	on debug sections, even if they have an output section.  Also
	set VMA on zero size sections, and non-load but alloc sections.
	Set adjusted_section_count to -1 when no section adjustment.
	Malloc adjusted_sections.  Don't double last_vma.  Transfer
	alloc section VMAs to separate debug file.
	(_bfd_dwarf2_cleanup_debug_info): Free adjusted_sections.
	(_bfd_dwarf2_slurp_debug_info): Add do_place parameter.  Drop
	test on symbols being the same before using old stash.  Read
	and use separate debug file symbols.  Call place_sections.
	(find_line): Don't call place_sections here.
	* libbfd-in.h (_bfd_dwarf2_slurp_debug_info): Update proto.
	* libbfd.h: Regenerate.
	* mach-o.c (bfd_mach_o_find_nearest_line): Adjust
	_bfd_dwarf2_slurp_debug_info call.
	* simple.c (simple_save_output_info): Clarify comment.

bfd/ChangeLog

@@ -1,3 +1,27 @@
+2014-04-24  Alan Modra  <amodra@gmail.com>
+
+	PR 16867
+	* dwarf2.c: Formatting.
+	(struct dwarf2_debug): Make adjusted_section_count signed.
+	(unset_sections): Make i signed.
+	(set_debug_vma): New function.
+	(place_sections): Handle separate debug object file.  Set VMA
+	on debug sections, even if they have an output section.  Also
+	set VMA on zero size sections, and non-load but alloc sections.
+	Set adjusted_section_count to -1 when no section adjustment.
+	Malloc adjusted_sections.  Don't double last_vma.  Transfer
+	alloc section VMAs to separate debug file.
+	(_bfd_dwarf2_cleanup_debug_info): Free adjusted_sections.
+	(_bfd_dwarf2_slurp_debug_info): Add do_place parameter.  Drop
+	test on symbols being the same before using old stash.  Read
+	and use separate debug file symbols.  Call place_sections.
+	(find_line): Don't call place_sections here.
+	* libbfd-in.h (_bfd_dwarf2_slurp_debug_info): Update proto.
+	* libbfd.h: Regenerate.
+	* mach-o.c (bfd_mach_o_find_nearest_line): Adjust
+	_bfd_dwarf2_slurp_debug_info call.
+	* simple.c (simple_save_output_info): Clarify comment.
+
 2014-04-24  Nick Clifton  <nickc@redhat.com>
 
 	PR ld/16807

bfd/dwarf2.c

@@ -160,7 +160,7 @@ struct dwarf2_debug
   bfd_vma *sec_vma;
 
   /* Number of sections whose VMA we must adjust.  */
-  unsigned int adjusted_section_count;
+  int adjusted_section_count;
 
   /* Array of sections with adjusted VMA.  */
   struct adjusted_section *adjusted_sections;
@@ -645,7 +645,7 @@ read_indirect_string (struct comp_unit * unit,
 }
 
 /* Like read_indirect_string but uses a .debug_str located in
-   an alternate filepointed to by the .gnu_debuglink section.
+   an alternate file pointed to by the .gnu_debugaltlink section.
    Used to impement DW_FORM_GNU_strp_alt.  */
 
 static char *
@@ -2990,12 +2990,36 @@ find_debug_info (bfd *abfd, const struct dwarf_debug_section *debug_sections,
   return NULL;
 }
 
+/* Transfer VMAs from object file to separate debug file.  */
+
+static void
+set_debug_vma (bfd *orig_bfd, bfd *debug_bfd)
+{
+  asection *s, *d;
+
+  for (s = orig_bfd->sections, d = debug_bfd->sections;
+       s != NULL && d != NULL;
+       s = s->next, d = d->next)
+    {
+      if ((d->flags & SEC_DEBUGGING) != 0)
+	break;
+      /* ??? Assumes 1-1 correspondence between sections in the
+	 two files.  */
+      if (strcmp (s->name, d->name) == 0)
+	{
+	  d->output_section = s->output_section;
+	  d->output_offset = s->output_offset;
+	  d->vma = s->vma;
+	}
+    }
+}
+
 /* Unset vmas for adjusted sections in STASH.  */
 
 static void
 unset_sections (struct dwarf2_debug *stash)
 {
-  unsigned int i;
+  int i;
   struct adjusted_section *p;
 
   i = stash->adjusted_section_count;
@@ -3004,14 +3028,23 @@ unset_sections (struct dwarf2_debug *stash)
     p->section->vma = 0;
 }
 
-/* Set unique VMAs for loadable and DWARF sections in ABFD and save
+/* Set VMAs for allocated and .debug_info sections in ORIG_BFD, a
-   VMAs in STASH for unset_sections.  */
+   relocatable object file.  VMAs are normally all zero in relocatable
+   object files, so if we want to distinguish locations in sections by
+   address we need to set VMAs so the sections do not overlap.  We
+   also set VMA on .debug_info so that when we have multiple
+   .debug_info sections (or the linkonce variant) they also do not
+   overlap.  The multiple .debug_info sections make up a single
+   logical section.  ??? We should probably do the same for other
+   debug sections.  */
 
 static bfd_boolean
-place_sections (bfd *abfd, struct dwarf2_debug *stash)
+place_sections (bfd *orig_bfd, struct dwarf2_debug *stash)
 {
+  bfd *abfd;
   struct adjusted_section *p;
-  unsigned int i;
+  int i;
+  const char *debug_info_name;
 
   if (stash->adjusted_section_count != 0)
     {
@@ -3019,91 +3052,86 @@ place_sections (bfd *abfd, struct dwarf2_debug *stash)
       p = stash->adjusted_sections;
       for (; i > 0; i--, p++)
 	p->section->vma = p->adj_vma;
+      return TRUE;
     }
-  else
-    {
-      asection *sect;
-      bfd_vma last_vma = 0, last_dwarf = 0;
-      bfd_size_type amt;
-      const char *debug_info_name;
 
   debug_info_name = stash->debug_sections[debug_info].uncompressed_name;
   i = 0;
+  abfd = orig_bfd;
+  while (1)
+    {
+      asection *sect;
+
       for (sect = abfd->sections; sect != NULL; sect = sect->next)
 	{
-	  bfd_size_type sz;
 	  int is_debug_info;
 
 	  if ((sect->output_section != NULL
-	       && sect->output_section != sect)
+	       && sect->output_section != sect
+	       && (sect->flags & SEC_DEBUGGING) == 0)
 	      || sect->vma != 0)
 	    continue;
 
-	  /* We need to adjust the VMAs of any .debug_info sections.
+	  is_debug_info = (strcmp (sect->name, debug_info_name) == 0
-	     Skip compressed ones, since no relocations could target
+			   || CONST_STRNEQ (sect->name, GNU_LINKONCE_INFO));
-	     them - they should not appear in object files anyway.  */
-	  if (strcmp (sect->name, debug_info_name) == 0)
-	    is_debug_info = 1;
-	  else if (CONST_STRNEQ (sect->name, GNU_LINKONCE_INFO))
-	    is_debug_info = 1;
-	  else
-	    is_debug_info = 0;
 
-	  if (!is_debug_info && (sect->flags & SEC_LOAD) == 0)
+	  if (!((sect->flags & SEC_ALLOC) != 0 && abfd == orig_bfd)
-	    continue;
+	      && !is_debug_info)
-
-	  sz = sect->rawsize ? sect->rawsize : sect->size;
-	  if (sz == 0)
 	    continue;
 
 	  i++;
 	}
-      if (i <= 1)
+      if (abfd == stash->bfd_ptr)
-	return TRUE;
+	break;
+      abfd = stash->bfd_ptr;
+    }
 
-      amt = i * sizeof (struct adjusted_section);
+  if (i <= 1)
-      p = (struct adjusted_section *) bfd_alloc (abfd, amt);
+    stash->adjusted_section_count = -1;
-      if (! p)
+  else
+    {
+      bfd_vma last_vma = 0, last_dwarf = 0;
+      bfd_size_type amt = i * sizeof (struct adjusted_section);
+
+      p = (struct adjusted_section *) bfd_malloc (amt);
+      if (p == NULL)
 	return FALSE;
 
       stash->adjusted_sections = p;
       stash->adjusted_section_count = i;
 
+      abfd = orig_bfd;
+      while (1)
+	{
+	  asection *sect;
+
 	  for (sect = abfd->sections; sect != NULL; sect = sect->next)
 	    {
 	      bfd_size_type sz;
 	      int is_debug_info;
 
 	      if ((sect->output_section != NULL
-	       && sect->output_section != sect)
+		   && sect->output_section != sect
+		   && (sect->flags & SEC_DEBUGGING) == 0)
 		  || sect->vma != 0)
 		continue;
 
-	  /* We need to adjust the VMAs of any .debug_info sections.
+	      is_debug_info = (strcmp (sect->name, debug_info_name) == 0
-	     Skip compressed ones, since no relocations could target
+			       || CONST_STRNEQ (sect->name, GNU_LINKONCE_INFO));
-	     them - they should not appear in object files anyway.  */
-	  if (strcmp (sect->name, debug_info_name) == 0)
-	    is_debug_info = 1;
-	  else if (CONST_STRNEQ (sect->name, GNU_LINKONCE_INFO))
-	    is_debug_info = 1;
-	  else
-	    is_debug_info = 0;
 
-	  if (!is_debug_info && (sect->flags & SEC_LOAD) == 0)
+	      if (!((sect->flags & SEC_ALLOC) != 0 && abfd == orig_bfd)
+		  && !is_debug_info)
 		continue;
 
 	      sz = sect->rawsize ? sect->rawsize : sect->size;
-	  if (sz == 0)
-	    continue;
 
-	  p->section = sect;
 	      if (is_debug_info)
 		{
 		  BFD_ASSERT (sect->alignment_power == 0);
 		  sect->vma = last_dwarf;
 		  last_dwarf += sz;
 		}
-	  else if (last_vma != 0)
+	      else
 		{
 		  /* Align the new address to the current section
 		     alignment.  */
@@ -3111,16 +3139,21 @@ place_sections (bfd *abfd, struct dwarf2_debug *stash)
 			       + ~((bfd_vma) -1 << sect->alignment_power))
 			      & ((bfd_vma) -1 << sect->alignment_power));
 		  sect->vma = last_vma;
-	      last_vma += sect->vma + sz;
+		  last_vma += sz;
 		}
-	  else
-	    last_vma += sect->vma + sz;
 
+	      p->section = sect;
 	      p->adj_vma = sect->vma;
-
 	      p++;
 	    }
+	  if (abfd == stash->bfd_ptr)
+	    break;
+	  abfd = stash->bfd_ptr;
 	}
+    }
+
+  if (orig_bfd != stash->bfd_ptr)
+    set_debug_vma (orig_bfd, stash->bfd_ptr);
 
   return TRUE;
 }
@@ -3409,7 +3442,8 @@ bfd_boolean
 _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
 			      const struct dwarf_debug_section *debug_sections,
 			      asymbol **symbols,
-                              void **pinfo)
+			      void **pinfo,
+			      bfd_boolean do_place)
 {
   bfd_size_type amt = sizeof (struct dwarf2_debug);
   bfd_size_type total_size;
@@ -3418,8 +3452,7 @@ _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
 
   if (stash != NULL)
     {
-      if (stash->syms == symbols
+      if (section_vma_same (abfd, stash))
-	  && section_vma_same (abfd, stash))
 	return TRUE;
       _bfd_dwarf2_cleanup_debug_info (abfd, pinfo);
       memset (stash, 0, amt);
@@ -3455,7 +3488,8 @@ _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
       if ((debug_bfd = bfd_openr (debug_filename, NULL)) == NULL
 	  || ! bfd_check_format (debug_bfd, bfd_object)
 	  || (msec = find_debug_info (debug_bfd,
-				      debug_sections, NULL)) == NULL)
+				      debug_sections, NULL)) == NULL
+	  || !bfd_generic_link_read_symbols (debug_bfd))
 	{
 	  if (debug_bfd)
 	    bfd_close (debug_bfd);
@@ -3463,10 +3497,17 @@ _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
 	  free (debug_filename);
 	  return FALSE;
 	}
+
+      symbols = bfd_get_outsymbols (debug_bfd);
+      stash->syms = symbols;
       stash->close_on_cleanup = TRUE;
     }
   stash->bfd_ptr = debug_bfd;
 
+  if (do_place
+      && !place_sections (abfd, stash))
+    return FALSE;
+
   /* There can be more than one DWARF2 info section in a BFD these
      days.  First handle the easy case when there's only one.  If
      there's more than one, try case two: none of the sections is
@@ -3574,20 +3615,13 @@ find_line (bfd *abfd,
   if (discriminator_ptr)
     *discriminator_ptr = 0;
 
-  if (! _bfd_dwarf2_slurp_debug_info (abfd, NULL,
+  if (! _bfd_dwarf2_slurp_debug_info (abfd, NULL, debug_sections,
-				      debug_sections, symbols, pinfo))
+				      symbols, pinfo,
+				      (abfd->flags & (EXEC_P | DYNAMIC)) == 0))
     return FALSE;
 
   stash = (struct dwarf2_debug *) *pinfo;
 
-  /* In a relocatable file, 2 functions may have the same address.
-     We change the section vma so that they won't overlap.  */
-  if ((abfd->flags & (EXEC_P | DYNAMIC)) == 0)
-    {
-      if (! place_sections (abfd, stash))
-	return FALSE;
-    }
-
   do_line = (section == NULL
 	     && offset == 0
 	     && functionname_ptr == NULL
@@ -3962,6 +3996,8 @@ _bfd_dwarf2_cleanup_debug_info (bfd *abfd, void **pinfo)
     free (stash->alt_dwarf_info_buffer);
   if (stash->sec_vma)
     free (stash->sec_vma);
+  if (stash->adjusted_sections)
+    free (stash->adjusted_sections);
   if (stash->alt_bfd_ptr)
     bfd_close (stash->alt_bfd_ptr);
 }

bfd/libbfd-in.h

@@ -560,7 +560,8 @@ extern bfd_boolean _bfd_dwarf2_find_inliner_info
 
 /* Read DWARF 2 debugging information. */
 extern bfd_boolean _bfd_dwarf2_slurp_debug_info
-  (bfd *, bfd *, const struct dwarf_debug_section *, asymbol **, void **);
+  (bfd *, bfd *, const struct dwarf_debug_section *, asymbol **, void **,
+   bfd_boolean);
 
 /* Clean up the data used to handle DWARF 2 debugging information. */
 extern void _bfd_dwarf2_cleanup_debug_info

bfd/libbfd.h

@@ -565,7 +565,8 @@ extern bfd_boolean _bfd_dwarf2_find_inliner_info
 
 /* Read DWARF 2 debugging information. */
 extern bfd_boolean _bfd_dwarf2_slurp_debug_info
-  (bfd *, bfd *, const struct dwarf_debug_section *, asymbol **, void **);
+  (bfd *, bfd *, const struct dwarf_debug_section *, asymbol **, void **,
+   bfd_boolean);
 
 /* Clean up the data used to handle DWARF 2 debugging information. */
 extern void _bfd_dwarf2_cleanup_debug_info

bfd/mach-o.c

@@ -5660,7 +5660,8 @@ bfd_mach_o_find_nearest_line (bfd *abfd,
             break;
           if (! _bfd_dwarf2_slurp_debug_info (abfd, mdata->dsym_bfd,
                                               dwarf_debug_sections, symbols,
-                                              &mdata->dwarf2_find_line_info))
+                                              &mdata->dwarf2_find_line_info,
+					      FALSE))
             return FALSE;
         }
       break;

bfd/simple.c

@@ -106,6 +106,22 @@ struct saved_offsets
   struct saved_output_info *sections;
 };
 
+/* The sections in ABFD may already have output sections and offsets
+   set if we are here during linking.
+
+   DWARF-2 specifies offsets into debug sections in many cases and
+   bfd_simple_get_relocated_section_contents is called to relocate
+   debug info for a single relocatable object file.  So we want
+   offsets relative to that object file's sections, not offsets in the
+   output file.  For that reason, reset a debug section->output_offset
+   to zero.
+
+   If not called during linking then set section->output_section to
+   point back to the input section, because output_section must not be
+   NULL when calling the relocation routines.
+
+   Save the original output offset and section to restore later.  */
+
 static void
 simple_save_output_info (bfd *abfd ATTRIBUTE_UNUSED,
 			 asection *section,
@@ -220,15 +236,6 @@ bfd_simple_get_relocated_section_contents (bfd *abfd,
       outbuf = data;
     }
 
-  /* The sections in ABFD may already have output sections and offsets set.
-     Because this function is primarily for debug sections, and GCC uses the
-     knowledge that debug sections will generally have VMA 0 when emitting
-     relocations between DWARF-2 sections (which are supposed to be
-     section-relative offsets anyway), we need to reset the output offsets
-     to zero.  We also need to arrange for section->output_section->vma plus
-     section->output_offset to equal section->vma, which we do by setting
-     section->output_section to point back to section.  Save the original
-     output offset and output section to restore later.  */
   saved_offsets.section_count = abfd->section_count;
   saved_offsets.sections = malloc (sizeof (*saved_offsets.sections)
 				   * saved_offsets.section_count);