Rewrite ppc32 backend .sdata and .sdata2 handling

[Alan Modra <amodra at gmail dot com>]

This patch rewrites some of the ppc32 backend .sdata and .sdata2 code:
1) _SDA_BASE_ and _SDA2_BASE_ and defined automatically, in a similar
   manner to the way _GLOBAL_OFFSET_TABLE_ is handled.  It's a little
   more complicated to remove the symbols because _SDA_BASE_ needs to
   be there if either .sdata or .sbss is present, and similarly for
   _SDA2_BASE.
2) The linker created .sdata and .sdata2 sections used for
   R_PPC_EMB_SDAI16 and R_PPC_EMB_SDA2I16 pointers are created early.
   Nowadays we strip unneeded sections from the output, so it isn't
   necessary to delay creating the sections.
3) The output section for targets of various SDA relocs is now checked
   as per the ABI(s).  We previously allowed .sdata.foo and similar,
   most likely because at some stage we were checking input sections.

Also, the patch fixes a long-standing bug in size_input_sections
that affects the values of symbols defined in stripped input
sections.

bfd/
	PR 16952
	* elf32-ppc.c (ppc_elf_create_linker_section): Move earlier.
	Remove redundant setting of htab->elf.dynobj.  Don't align.
	Define .sdata symbols using _bfd_elf_define_linkage_sym.
	(ppc_elf_create_glink): Call ppc_elf_create_linker_section.
	(create_sdata_sym): Delete.
	(elf_allocate_pointer_linker_section): Rename from
	elf_create_pointer_linker_section.  Align section.
	(ppc_elf_check_relocs): Don't call ppc_elf_creat_linker_section
	directly here, or create_sdata_sym.  Set ref_regular on _SDA_BASE_
	and _SDA2_BASE_.
	(ppc_elf_size_dynamic_sections): Remove ATTRIBUTE_UNUSED on param.
	Remove unnecessary tests on _SDA_BASE_ sym.
	(maybe_strip_sdasym, ppc_elf_maybe_strip_sdata_syms): New functions.
	(ppc_elf_relocate_section): Tighten SDA reloc symbol section checks.
	* elf32-ppc.h (ppc_elf_set_sdata_syms): Delete.
	(ppc_elf_maybe_strip_sdata_syms): Declare.
ld/
	PR 16952
	* emulparams/elf32ppccommon.sh (_SDA_BASE_, _SDA2_BASE_): Delete.
	* emultempl/ppc32elf.em (ppc_before_allocation): Call
	ppc_elf_maybe_strip_sdata_syms.
	* ldlang.c (size_input_section): Correct output_offset value
	for excluded input sections.

diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index b99db68..c2624cc 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -3338,6 +3338,37 @@ ppc_elf_create_got (bfd *abfd, struct bfd_link_info *info)
   return TRUE;
 }
 
+/* Create a special linker section, used for R_PPC_EMB_SDAI16 and
+   R_PPC_EMB_SDA2I16 pointers.  These sections become part of .sdata
+   and .sdata2.  Create _SDA_BASE_ and _SDA2_BASE too.  */
+
+static bfd_boolean
+ppc_elf_create_linker_section (bfd *abfd,
+			       struct bfd_link_info *info,
+			       flagword flags,
+			       elf_linker_section_t *lsect)
+{
+  asection *s;
+
+  flags |= (SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY
+	    | SEC_LINKER_CREATED);
+
+  s = bfd_make_section_anyway_with_flags (abfd, lsect->name, flags);
+  if (s == NULL
+      || !bfd_set_section_alignment (abfd, s, 2))
+    return FALSE;
+  lsect->section = s;
+
+  /* Define the sym on the first section of this name.  */
+  s = bfd_get_section_by_name (abfd, lsect->name);
+
+  lsect->sym = _bfd_elf_define_linkage_sym (abfd, info, s, lsect->sym_name);
+  if (lsect->sym == NULL)
+    return FALSE;
+  lsect->sym->root.u.def.value = 0x8000;
+  return TRUE;
+}
+
 static bfd_boolean
 ppc_elf_create_glink (bfd *abfd, struct bfd_link_info *info)
 {
@@ -3379,6 +3410,15 @@ ppc_elf_create_glink (bfd *abfd, struct bfd_link_info *info)
   if (s == NULL
       || ! bfd_set_section_alignment (abfd, s, 2))
     return FALSE;
+
+  if (!ppc_elf_create_linker_section (abfd, info, 0,
+				      &htab->sdata[0]))
+    return FALSE;
+
+  if (!ppc_elf_create_linker_section (abfd, info, SEC_READONLY,
+				      &htab->sdata[1]))
+    return FALSE;
+
   return TRUE;
 }
 
@@ -3605,51 +3645,6 @@ ppc_elf_add_symbol_hook (bfd *abfd,
   return TRUE;
 }
 
-static bfd_boolean
-create_sdata_sym (struct bfd_link_info *info, elf_linker_section_t *lsect)
-{
-  struct ppc_elf_link_hash_table *htab = ppc_elf_hash_table (info);
-
-  lsect->sym = elf_link_hash_lookup (&htab->elf, lsect->sym_name,
-				     TRUE, FALSE, TRUE);
-  if (lsect->sym == NULL)
-    return FALSE;
-  if (lsect->sym->root.type == bfd_link_hash_new)
-    lsect->sym->non_elf = 0;
-  lsect->sym->ref_regular = 1;
-  _bfd_elf_link_hash_hide_symbol (info, lsect->sym, TRUE);
-  return TRUE;
-}
-
-/* Create a special linker section.  */
-
-static bfd_boolean
-ppc_elf_create_linker_section (bfd *abfd,
-			       struct bfd_link_info *info,
-			       flagword flags,
-			       elf_linker_section_t *lsect)
-{
-  struct ppc_elf_link_hash_table *htab = ppc_elf_hash_table (info);
-  asection *s;
-
-  flags |= (SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY
-	    | SEC_LINKER_CREATED);
-
-  /* Record the first bfd that needs the special sections.  */
-  if (!htab->elf.dynobj)
-    htab->elf.dynobj = abfd;
-
-  s = bfd_make_section_anyway_with_flags (htab->elf.dynobj,
-					  lsect->name,
-					  flags);
-  if (s == NULL
-      || !bfd_set_section_alignment (htab->elf.dynobj, s, 2))
-    return FALSE;
-  lsect->section = s;
-
-  return create_sdata_sym (info, lsect);
-}
-
 /* Find a linker generated pointer with a given addend and type.  */
 
 static elf_linker_section_pointers_t *
@@ -3668,10 +3663,10 @@ elf_find_pointer_linker_section
 /* Allocate a pointer to live in a linker created section.  */
 
 static bfd_boolean
-elf_create_pointer_linker_section (bfd *abfd,
-				   elf_linker_section_t *lsect,
-				   struct elf_link_hash_entry *h,
-				   const Elf_Internal_Rela *rel)
+elf_allocate_pointer_linker_section (bfd *abfd,
+				     elf_linker_section_t *lsect,
+				     struct elf_link_hash_entry *h,
+				     const Elf_Internal_Rela *rel)
 {
   elf_linker_section_pointers_t **ptr_linker_section_ptr = NULL;
   elf_linker_section_pointers_t *linker_section_ptr;
@@ -4074,12 +4069,9 @@ ppc_elf_check_relocs (bfd *abfd,
 	      bad_shared_reloc (abfd, r_type);
 	      return FALSE;
 	    }
-	  if (htab->sdata[0].section == NULL
-	      && !ppc_elf_create_linker_section (abfd, info, 0,
-						 &htab->sdata[0]))
-	    return FALSE;
-	  if (!elf_create_pointer_linker_section (abfd, &htab->sdata[0],
-						  h, rel))
+	  htab->sdata[0].sym->ref_regular = 1;
+	  if (!elf_allocate_pointer_linker_section (abfd, &htab->sdata[0],
+						    h, rel))
 	    return FALSE;
 	  if (h != NULL)
 	    {
@@ -4095,12 +4087,9 @@ ppc_elf_check_relocs (bfd *abfd,
 	      bad_shared_reloc (abfd, r_type);
 	      return FALSE;
 	    }
-	  if (htab->sdata[1].section == NULL
-	      && !ppc_elf_create_linker_section (abfd, info, SEC_READONLY,
-						 &htab->sdata[1]))
-	    return FALSE;
-	  if (!elf_create_pointer_linker_section (abfd, &htab->sdata[1],
-						  h, rel))
+	  htab->sdata[1].sym->ref_regular = 1;
+	  if (!elf_allocate_pointer_linker_section (abfd, &htab->sdata[1],
+						    h, rel))
 	    return FALSE;
 	  if (h != NULL)
 	    {
@@ -4109,21 +4098,16 @@ ppc_elf_check_relocs (bfd *abfd,
 	    }
 	  break;
 
+	case R_PPC_SDAREL16:
+	  htab->sdata[0].sym->ref_regular = 1;
+	  /* Fall thru */
+
 	case R_PPC_VLE_SDAREL_LO16A:
 	case R_PPC_VLE_SDAREL_LO16D:
 	case R_PPC_VLE_SDAREL_HI16A:
 	case R_PPC_VLE_SDAREL_HI16D:
 	case R_PPC_VLE_SDAREL_HA16A:
 	case R_PPC_VLE_SDAREL_HA16D:
-	case R_PPC_SDAREL16:
-	  if (htab->sdata[0].sym == NULL
-	      && !create_sdata_sym (info, &htab->sdata[0]))
-	    return FALSE;
-
-	  if (htab->sdata[1].sym == NULL
-	      && !create_sdata_sym (info, &htab->sdata[1]))
-	    return FALSE;
-
 	  if (h != NULL)
 	    {
 	      ppc_elf_hash_entry (h)->has_sda_refs = TRUE;
@@ -4148,9 +4132,7 @@ ppc_elf_check_relocs (bfd *abfd,
 	      bad_shared_reloc (abfd, r_type);
 	      return FALSE;
 	    }
-	  if (htab->sdata[1].sym == NULL
-	      && !create_sdata_sym (info, &htab->sdata[1]))
-	    return FALSE;
+	  htab->sdata[1].sym->ref_regular = 1;
 	  if (h != NULL)
 	    {
 	      ppc_elf_hash_entry (h)->has_sda_refs = TRUE;
@@ -4167,12 +4149,6 @@ ppc_elf_check_relocs (bfd *abfd,
 	      bad_shared_reloc (abfd, r_type);
 	      return FALSE;
 	    }
-	  if (htab->sdata[0].sym == NULL
-	      && !create_sdata_sym (info, &htab->sdata[0]))
-	    return FALSE;
-	  if (htab->sdata[1].sym == NULL
-	      && !create_sdata_sym (info, &htab->sdata[1]))
-	    return FALSE;
 	  if (h != NULL)
 	    {
 	      ppc_elf_hash_entry (h)->has_sda_refs = TRUE;
@@ -6119,7 +6095,7 @@ static const unsigned char glink_eh_frame_cie[] =
 /* Set the sizes of the dynamic sections.  */
 
 static bfd_boolean
-ppc_elf_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
+ppc_elf_size_dynamic_sections (bfd *output_bfd,
 			       struct bfd_link_info *info)
 {
   struct ppc_elf_link_hash_table *htab;
@@ -6323,14 +6299,9 @@ ppc_elf_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
   if (info->shared)
     {
       struct elf_link_hash_entry *sda = htab->sdata[0].sym;
-      if (sda != NULL
-	  && !(sda->root.type == bfd_link_hash_defined
-	       || sda->root.type == bfd_link_hash_defweak))
-	{
-	  sda->root.type = bfd_link_hash_defined;
-	  sda->root.u.def.section = htab->elf.hgot->root.u.def.section;
-	  sda->root.u.def.value = htab->elf.hgot->root.u.def.value;
-	}
+
+      sda->root.u.def.section = htab->elf.hgot->root.u.def.section;
+      sda->root.u.def.value = htab->elf.hgot->root.u.def.value;
     }
 
   if (htab->glink != NULL
@@ -6599,6 +6570,46 @@ ppc_elf_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
   return TRUE;
 }
 
+/* Arrange to have _SDA_BASE_ or _SDA2_BASE_ stripped from the output
+   if it looks like nothing is using them.  */
+
+static void
+maybe_strip_sdasym (bfd *output_bfd, elf_linker_section_t *lsect)
+{
+  struct elf_link_hash_entry *sda = lsect->sym;
+
+  if (sda != NULL && !sda->ref_regular && sda->dynindx == -1)
+    {
+      asection *s;
+
+      s = bfd_get_section_by_name (output_bfd, lsect->name);
+      if (s == NULL || bfd_section_removed_from_list (output_bfd, s))
+	{
+	  s = bfd_get_section_by_name (output_bfd, lsect->bss_name);
+	  if (s == NULL || bfd_section_removed_from_list (output_bfd, s))
+	    {
+	      sda->def_regular = 0;
+	      /* This is somewhat magic.  See elf_link_output_extsym.  */
+	      sda->ref_dynamic = 1;
+	      sda->forced_local = 0;
+	    }
+	}
+    }
+}
+
+void
+ppc_elf_maybe_strip_sdata_syms (struct bfd_link_info *info)
+{
+  struct ppc_elf_link_hash_table *htab = ppc_elf_hash_table (info);
+
+  if (htab != NULL)
+    {
+      maybe_strip_sdasym (info->output_bfd, &htab->sdata[0]);
+      maybe_strip_sdasym (info->output_bfd, &htab->sdata[1]);
+    }
+}
+
+
 /* Return TRUE if symbol should be hashed in the `.gnu.hash' section.  */
 
 static bfd_boolean
@@ -8696,10 +8707,8 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	    addend -= SYM_VAL (sda);
 
 	    name = bfd_get_section_name (output_bfd, sec->output_section);
-	    if (! ((CONST_STRNEQ (name, ".sdata")
-		    && (name[6] == 0 || name[6] == '.'))
-		   || (CONST_STRNEQ (name, ".sbss")
-		       && (name[5] == 0 || name[5] == '.'))))
+	    if (!(strcmp (name, ".sdata") == 0
+		  || strcmp (name, ".sbss") == 0))
 	      {
 		info->callbacks->einfo
 		  (_("%P: %B: the target (%s) of a %s relocation is "
@@ -8728,8 +8737,8 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	    addend -= SYM_VAL (sda);
 
 	    name = bfd_get_section_name (output_bfd, sec->output_section);
-	    if (! (CONST_STRNEQ (name, ".sdata2")
-		   || CONST_STRNEQ (name, ".sbss2")))
+	    if (!(strcmp (name, ".sdata2") == 0
+		  || strcmp (name, ".sbss2") == 0))
 	      {
 		info->callbacks->einfo
 		  (_("%P: %B: the target (%s) of a %s relocation is "
@@ -8796,16 +8805,14 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	      }
 
 	    name = bfd_get_section_name (output_bfd, sec->output_section);
-	    if (((CONST_STRNEQ (name, ".sdata")
-		  && (name[6] == 0 || name[6] == '.'))
-		 || (CONST_STRNEQ (name, ".sbss")
-		     && (name[5] == 0 || name[5] == '.'))))
+	    if (strcmp (name, ".sdata") == 0
+		|| strcmp (name, ".sbss") == 0)
 	      {
 		reg = 13;
 		sda = htab->sdata[0].sym;
 	      }
-	    else if (CONST_STRNEQ (name, ".sdata2")
-		     || CONST_STRNEQ (name, ".sbss2"))
+	    else if (strcmp (name, ".sdata2") == 0
+		     || strcmp (name, ".sbss2") == 0)
 	      {
 		reg = 2;
 		sda = htab->sdata[1].sym;
@@ -8897,16 +8904,14 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	      }
 
 	    name = bfd_get_section_name (output_bfd, sec->output_section);
-	    if (((CONST_STRNEQ (name, ".sdata")
-		  && (name[6] == 0 || name[6] == '.'))
-		 || (CONST_STRNEQ (name, ".sbss")
-		     && (name[5] == 0 || name[5] == '.'))))
+	    if (strcmp (name, ".sdata") == 0
+		|| strcmp (name, ".sbss") == 0)
 	      {
 		//reg = 13;
 		sda = htab->sdata[0].sym;
 	      }
-	    else if (CONST_STRNEQ (name, ".sdata2")
-		     || CONST_STRNEQ (name, ".sbss2"))
+	    else if (strcmp (name, ".sdata2") == 0
+		     || strcmp (name, ".sbss2") == 0)
 	      {
 		//reg = 2;
 		sda = htab->sdata[1].sym;
diff --git a/bfd/elf32-ppc.h b/bfd/elf32-ppc.h
index e8d19ec..07dc4c8 100644
--- a/bfd/elf32-ppc.h
+++ b/bfd/elf32-ppc.h
@@ -50,7 +50,7 @@ void ppc_elf_link_params (struct bfd_link_info *, struct ppc_elf_params *);
 int ppc_elf_select_plt_layout (bfd *, struct bfd_link_info *);
 asection *ppc_elf_tls_setup (bfd *, struct bfd_link_info *);
 bfd_boolean ppc_elf_tls_optimize (bfd *, struct bfd_link_info *);
-void ppc_elf_set_sdata_syms (bfd *, struct bfd_link_info *);
+void ppc_elf_maybe_strip_sdata_syms (struct bfd_link_info *);
 extern bfd_boolean ppc_elf_modify_segment_map (bfd *,
 		           struct bfd_link_info * ATTRIBUTE_UNUSED);
 extern bfd_boolean ppc_elf_section_processing (bfd *, Elf_Internal_Shdr *);
diff --git a/ld/emulparams/elf32ppccommon.sh b/ld/emulparams/elf32ppccommon.sh
index 049fdb9..1f54ef8 100644
--- a/ld/emulparams/elf32ppccommon.sh
+++ b/ld/emulparams/elf32ppccommon.sh
@@ -13,8 +13,6 @@ ARCH=powerpc:common
 MACHINE=
 EXECUTABLE_SYMBOLS='PROVIDE (__stack = 0); PROVIDE (___stack = 0);'
 if test -z "${CREATE_SHLIB}"; then
-  SDATA_START_SYMBOLS="PROVIDE (_SDA_BASE_ = 32768);"
-  SDATA2_START_SYMBOLS="PROVIDE (_SDA2_BASE_ = 32768);"
   SBSS_START_SYMBOLS="PROVIDE (__sbss_start = .); PROVIDE (___sbss_start = .);"
   SBSS_END_SYMBOLS="PROVIDE (__sbss_end = .); PROVIDE (___sbss_end = .);"
 else
diff --git a/ld/emultempl/ppc32elf.em b/ld/emultempl/ppc32elf.em
index 069acd2..0e2af12 100644
--- a/ld/emultempl/ppc32elf.em
+++ b/ld/emultempl/ppc32elf.em
@@ -135,6 +135,8 @@ ppc_before_allocation (void)
 
   gld${EMULATION_NAME}_before_allocation ();
 
+  ppc_elf_maybe_strip_sdata_syms (&link_info);
+
   if (RELAXATION_ENABLED)
     params.branch_trampolines = 1;
 
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 8d1e3f7..7c076a2 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -4608,12 +4608,15 @@ size_input_section
 {
   lang_input_section_type *is = &((*this_ptr)->input_section);
   asection *i = is->section;
+  asection *o = output_section_statement->bfd_section;
 
-  if (i->sec_info_type != SEC_INFO_TYPE_JUST_SYMS
-      && (i->flags & SEC_EXCLUDE) == 0)
+  if (i->sec_info_type == SEC_INFO_TYPE_JUST_SYMS)
+    i->output_offset = i->vma - o->vma;
+  else if ((i->flags & SEC_EXCLUDE) != 0)
+    i->output_offset = dot - o->vma;
+  else
     {
       bfd_size_type alignment_needed;
-      asection *o;
 
       /* Align this section first to the input sections requirement,
 	 then to the output section's requirement.  If this alignment
@@ -4623,7 +4626,6 @@ size_input_section
       if (output_section_statement->subsection_alignment != -1)
 	i->alignment_power = output_section_statement->subsection_alignment;
 
-      o = output_section_statement->bfd_section;
       if (o->alignment_power < i->alignment_power)
 	o->alignment_power = i->alignment_power;
 
@@ -4636,17 +4638,12 @@ size_input_section
 	}
 
       /* Remember where in the output section this input section goes.  */
-
       i->output_offset = dot - o->vma;
 
       /* Mark how big the output section must be to contain this now.  */
       dot += TO_ADDR (i->size);
       o->size = TO_SIZE (dot - o->vma);
     }
-  else
-    {
-      i->output_offset = i->vma - output_section_statement->bfd_section->vma;
-    }
 
   return dot;
 }

-- 
Alan Modra
Australia Development Lab, IBM