Don't generate PLT for IFUNC GOT/pointer reference

If a backend supports it, PLT entry isn't needed when all references
to a STT_GNU_IFUNC symbols are done via GOT or static function pointers.
For GOT entries, We generate dynamic R_*_GLOB_DAT relocations for
preemptable symbols and R_*_IRELATIVE relocations for non-preemptable
symbols to update them with real function address.  For static pointer
pointers, we generate dynamic pointer relocations and store them in:

1. .rel[a].ifunc section in PIC object.
2. .rel[a].got section in dynamic executable.
3. .rel[a].iplt section in static executable.

We don't allocate GOT entry if it isn't used.

bfd/

	PR ld/20253
	* elf-bfd.h (_bfd_elf_allocate_ifunc_dyn_relocs): Add an
	bfd_boolean argument.
	* elf-ifunc.c (_bfd_elf_create_ifunc_sections): Replace
	"shared object" with "PIC object" in comments.
	(_bfd_elf_allocate_ifunc_dyn_relocs): Updated.  Replace
	"shared object" with "PIC object" in comments.  Avoid PLT if
	requested.  Generate dynamic relocations for non-GOT references.
	Make room for the special first entry in PLT and allocate PLT
	entry only for PLT and PC-relative references.  Store dynamic
	GOT relocations in .rel[a].iplt section for static executables.
	If PLT isn't used, always use GOT for symbol value.  Don't
	allocate GOT entry if it isn't used.
	* elf32-i386.c (elf_i386_check_relocs): Increment PLT reference
	count only in the code section.  Allocate dynamic pointer
	relocation against STT_GNU_IFUNC symbol in the non-code section.
	(elf_i386_adjust_dynamic_symbol): Increment PLT reference count
	only for PC-relative references.
	(elf_i386_allocate_dynrelocs): Pass TRUE to
	_bfd_elf_allocate_ifunc_dyn_relocs.
	(elf_i386_relocate_section): Allow R_386_GOT32/R_386_GOT32X
	relocations against STT_GNU_IFUNC symbols without PLT.  Generate
	dynamic pointer relocation against STT_GNU_IFUNC symbol in
	the non-code section and store it in the proper REL section.
	Don't allow non-pointer relocation against STT_GNU_IFUNC symbol
	without PLT.
	(elf_i386_finish_dynamic_symbol): Generate dynamic
	R_386_IRELATIVE and R_386_GLOB_DAT GOT relocations against
	STT_GNU_IFUNC symbols without PLT.
	(elf_i386_finish_dynamic_sections): Don't handle local
	STT_GNU_IFUNC symbols here.
	(elf_i386_output_arch_local_syms): Handle local STT_GNU_IFUNC
	symbols here.
	(elf_backend_output_arch_local_syms): New.
	* elf32-x86-64.c (elf_i386_check_relocs): Increment PLT reference
	count only in the code section.  Allocate dynamic pointer
	relocation against STT_GNU_IFUNC symbol in the non-code section.
	(elf_x86_64_adjust_dynamic_symbol): Increment PLT reference
	count only for PC-relative references.
	(elf_x86_64_allocate_dynrelocs): Pass TRUE to
	_bfd_elf_allocate_ifunc_dyn_relocs.
	(elf_x86_64_relocate_section): Allow R_X86_64_GOTPCREL,
	R_X86_64_GOTPCRELX, R_X86_64_REX_GOTPCRELX and
	R_X86_64_GOTPCREL64 relocations against STT_GNU_IFUNC symbols
	without PLT.  Generate dynamic pointer relocation against
	STT_GNU_IFUNC symbol in the non-code section and store it in
	the proper RELA section.  Don't allow non-pointer relocation
	against STT_GNU_IFUNC symbol without PLT.
	(elf_x86_64_finish_dynamic_symbol): Generate dynamic
	R_X86_64_IRELATIVE and R_X86_64_GLOB_DAT GOT relocations against
	STT_GNU_IFUNC symbols without PLT.
	(elf_x86_64_finish_dynamic_sections): Don't handle local
	STT_GNU_IFUNC symbols here.
	(elf_x86_64_output_arch_local_syms): Handle local STT_GNU_IFUNC
	symbols here.
	(elf_backend_output_arch_local_syms): New.
	* elfnn-aarch64.c (elfNN_aarch64_allocate_ifunc_dynrelocs):
	Pass FALSE to _bfd_elf_allocate_ifunc_dyn_relocs.

ld/

	PR ld/20253
	* testsuite/ld-i386/i386.exp: Run PR ld/20253 tests.
	* testsuite/ld-i386/no-plt.exp: Likewise.
	* testsuite/ld-x86-64/no-plt.exp: Likewise.
	* testsuite/ld-i386/pr13302.d: Remove .rel.plt section.
	* testsuite/ld-ifunc/ifunc-13-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-13-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-15-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-15-x86-64.d: Likewise.
	* testsuite/ld-x86-64/pr13082-5a.d: Likewise.
	* testsuite/ld-x86-64/pr13082-5b.d: Likewise.
	* testsuite/ld-x86-64/pr13082-6a.d: Likewise.
	* testsuite/ld-x86-64/pr13082-6b.d: Likewise.
	* testsuite/ld-i386/pr20244-2a.d: Remove .plt section.
	* testsuite/ld-ifunc/ifunc-21-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-21-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-22-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-22-x86-64.d: Likewise.
	* testsuite/ld-i386/pr20244-2b.d: Updated.
	* testsuite/ld-i386/pr20244-2c.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18a-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18a-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18b-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18b-x86-64.d: Likewise.
	* testsuite/ld-i386/pr20253-1a.c: New file.
	* testsuite/ld-i386/pr20253-1b.S: Likewise.
	* testsuite/ld-i386/pr20253-1c.S: Likewise.
	* testsuite/ld-i386/pr20253-1d.S: Likewise.
	* testsuite/ld-i386/pr20253-2a.c: Likewise.
	* testsuite/ld-i386/pr20253-2b.S: Likewise.
	* testsuite/ld-i386/pr20253-2c.S: Likewise.
	* testsuite/ld-i386/pr20253-2d.S: Likewise.
	* testsuite/ld-i386/pr20253-3.d: Likewise.
	* testsuite/ld-i386/pr20253-3.s: Likewise.
	* testsuite/ld-i386/pr20253-4.s: Likewise.
	* testsuite/ld-i386/pr20253-4a.d: Likewise.
	* testsuite/ld-i386/pr20253-4b.d: Likewise.
	* testsuite/ld-i386/pr20253-4c.d: Likewise.
	* testsuite/ld-i386/pr20253-5.d: Likewise.
	* testsuite/ld-i386/pr20253-5.s: Likewise.
	* testsuite/ld-ifunc/ifunc-23-x86.s: Likewise.
	* testsuite/ld-ifunc/ifunc-23a-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-23b-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-23c-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-24-x86.s: Likewise.
	* testsuite/ld-ifunc/ifunc-24a-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-24b-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-24c-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-25-x86.s: Likewise.
	* testsuite/ld-ifunc/ifunc-25a-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-25b-x86.d: Likewise.
	* testsuite/ld-ifunc/ifunc-25c-x86.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1.s: Likewise.
	* testsuite/ld-x86-64/pr20253-1a.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1b.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1c.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1d.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1e.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1f.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1g.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1h.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1i.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1j.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1k.d: Likewise.
	* testsuite/ld-x86-64/pr20253-1l.d: Likewise.
	* testsuite/ld-x86-64/pr20253-2a.c: Likewise.
	* testsuite/ld-x86-64/pr20253-2b.S: Likewise.
	* testsuite/ld-x86-64/pr20253-2c.S: Likewise.
	* testsuite/ld-x86-64/pr20253-2d.S: Likewise.
	* testsuite/ld-x86-64/pr20253-3.d: Likewise.
	* testsuite/ld-x86-64/pr20253-3.s: Likewise.
	* testsuite/ld-x86-64/pr20253-4.s: Likewise.
	* testsuite/ld-x86-64/pr20253-4a.d: Likewise.
	* testsuite/ld-x86-64/pr20253-4b.d: Likewise.
	* testsuite/ld-x86-64/pr20253-4c.d: Likewise.
	* testsuite/ld-x86-64/pr20253-4d.d: Likewise.
	* testsuite/ld-x86-64/pr20253-4e.d: Likewise.
	* testsuite/ld-x86-64/pr20253-4f.d: Likewise.
	* testsuite/ld-x86-64/pr20253-5.s: Likewise.
	* testsuite/ld-x86-64/pr20253-5a.d: Likewise.
	* testsuite/ld-x86-64/pr20253-5b.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18a-i386.d: Remove extra IRELATIVE
	relocation.
	* testsuite/ld-ifunc/ifunc-18a-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18b-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18b-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-18a.s: Fix a typo.
	* testsuite/ld-x86-64/x86-64.exp: Run pr20253-1 tests.

1 files changed, 122 insertions, 54 deletions

diff --git a/bfd/elf-ifunc.c b/bfd/elf-ifunc.c
index 1377fed..09cbf4a 100644
--- a/bfd/elf-ifunc.c
+++ b/bfd/elf-ifunc.c
@@ -55,7 +55,7 @@ _bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
 
   if (bfd_link_pic (info))
     {
-      /* We need to create .rel[a].ifunc for shared objects.  */
+      /* We need to create .rel[a].ifunc for PIC objects.  */
       const char *rel_sec = (bed->rela_plts_and_copies_p
 			     ? ".rela.ifunc" : ".rel.ifunc");
 
@@ -113,7 +113,8 @@ _bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
 				    bfd_boolean *readonly_dynrelocs_against_ifunc_p,
 				    unsigned int plt_entry_size,
 				    unsigned int plt_header_size,
-				    unsigned int got_entry_size)
+				    unsigned int got_entry_size,
+				    bfd_boolean avoid_plt)
 {
   asection *plt, *gotplt, *relplt;
   struct elf_dyn_relocs *p;
@@ -121,13 +122,17 @@ _bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
   const struct elf_backend_data *bed;
   struct elf_link_hash_table *htab;
   bfd_boolean readonly_dynrelocs_against_ifunc;
-
-  /* When a shared library references a STT_GNU_IFUNC symbol defined
-     in executable, the address of the resolved function may be used.
-     But in non-shared executable, the address of its .plt slot may
-     be used.  Pointer equality may not work correctly.  PIE should
-     be used if pointer equality is required here.  */
-  if (!bfd_link_pic (info)
+  /* If AVOID_PLT is TRUE, don't use PLT if possible.  */
+  bfd_boolean use_plt = !avoid_plt || h->plt.refcount > 0;
+  bfd_boolean need_dynreloc = !use_plt || bfd_link_pic (info);
+
+  /* When a PIC object references a STT_GNU_IFUNC symbol defined
+     in executable or it isn't referenced via PLT, the address of
+     the resolved function may be used.  But in non-PIC executable,
+     the address of its .plt slot may be used.  Pointer equality may
+     not work correctly.  PIE or non-PLT reference should be used if
+     pointer equality is required here.  */
+  if (!need_dynreloc
       && (h->dynindx != -1
 	  || info->export_dynamic)
       && h->pointer_equality_needed)
@@ -144,16 +149,30 @@ _bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
 
   htab = elf_hash_table (info);
 
-  /* When building shared library, we need to handle the case where it is
-     marked with regular reference, but not non-GOT reference since the
-     non-GOT reference bit may not be set here.  */
-  if (bfd_link_pic (info) && !h->non_got_ref && h->ref_regular)
-    for (p = *head; p != NULL; p = p->next)
-      if (p->count)
-	{
-	  h->non_got_ref = 1;
-	  goto keep;
-	}
+  /* When the symbol is marked with regular reference, if PLT isn't used
+     or we are building a PIC object, we must keep dynamic relocation
+     if there is non-GOT reference and use PLT if there is PC-relative
+     reference.  */
+  if (need_dynreloc && h->ref_regular)
+    {
+      bfd_boolean keep = FALSE;
+      for (p = *head; p != NULL; p = p->next)
+	if (p->count)
+	  {
+	    h->non_got_ref = 1;
+	    /* Need dynamic relocations for non-GOT reference.  */
+	    keep = TRUE;
+	    if (p->pc_count)
+	      {
+		/* Must use PLT for PC-relative reference.  */
+		use_plt = TRUE;
+		need_dynreloc = bfd_link_pic (info);
+		break;
+	      }
+	  }
+      if (keep)
+	goto keep;
+    }
 
   /* Support garbage collection against STT_GNU_IFUNC symbols.  */
   if (h->plt.refcount <= 0 && h->got.refcount <= 0)
@@ -165,7 +184,7 @@ _bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
     }
 
   /* Return and discard space for dynamic relocations against it if
-     it is never referenced in a non-shared object.  */
+     it is never referenced.  */
   if (!h->ref_regular)
     {
       if (h->plt.refcount > 0
@@ -192,9 +211,9 @@ keep:
       gotplt = htab->sgotplt;
       relplt = htab->srelplt;
 
-      /* If this is the first .plt entry, make room for the special
-	 first entry.  */
-      if (plt->size == 0)
+      /* If this is the first .plt entry and PLT is used, make room for
+	 the special first entry.  */
+      if (plt->size == 0 && use_plt)
 	plt->size += plt_header_size;
     }
   else
@@ -204,26 +223,31 @@ keep:
       relplt = htab->irelplt;
     }
 
-  /* Don't update value of STT_GNU_IFUNC symbol to PLT.  We need
-     the original value for R_*_IRELATIVE.  */
-  h->plt.offset = plt->size;
+  if (use_plt)
+    {
+      /* Don't update value of STT_GNU_IFUNC symbol to PLT.  We need
+	 the original value for R_*_IRELATIVE.  */
+      h->plt.offset = plt->size;
 
-  /* Make room for this entry in the .plt/.iplt section.  */
-  plt->size += plt_entry_size;
+      /* Make room for this entry in the .plt/.iplt section.  */
+      plt->size += plt_entry_size;
 
-  /* We also need to make an entry in the .got.plt/.got.iplt section,
-     which will be placed in the .got section by the linker script.  */
-  gotplt->size += got_entry_size;
+      /* We also need to make an entry in the .got.plt/.got.iplt section,
+	 which will be placed in the .got section by the linker script.  */
+      gotplt->size += got_entry_size;
+    }
 
   /* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
-     section.  */
-  relplt->size += sizeof_reloc;
-  relplt->reloc_count++;
+     section for GOTPLT relocation if PLT is used.  */
+  if (use_plt)
+    {
+      relplt->size += sizeof_reloc;
+      relplt->reloc_count++;
+    }
 
   /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
-     there is a non-GOT reference in a shared object.  */
-  if (!bfd_link_pic (info)
-      || !h->non_got_ref)
+     there is a non-GOT reference in a PIC object or PLT isn't used.  */
+  if (!need_dynreloc || !h->non_got_ref)
     *head = NULL;
 
   readonly_dynrelocs_against_ifunc = FALSE;
@@ -245,7 +269,20 @@ keep:
 	  p = p->next;
 	}
       while (p != NULL);
-      htab->irelifunc->size += count * sizeof_reloc;
+
+      /* Dynamic relocations are stored in
+	 1. .rel[a].ifunc section in PIC object.
+	 2. .rel[a].got section in dynamic executable.
+	 3. .rel[a].iplt section in static executable.  */
+      if (bfd_link_pic (info))
+	htab->irelifunc->size += count * sizeof_reloc;
+      else if (htab->splt != NULL)
+	htab->srelgot->size += count * sizeof_reloc;
+      else
+	{
+	  relplt->size += count * sizeof_reloc;
+	  relplt->reloc_count += count;
+	}
     }
 
   if (readonly_dynrelocs_against_ifunc_p)
@@ -254,34 +291,65 @@ keep:
   /* For STT_GNU_IFUNC symbol, .got.plt has the real function address
      and .got has the PLT entry adddress.  We will load the GOT entry
      with the PLT entry in finish_dynamic_symbol if it is used.  For
-     branch, it uses .got.plt.  For symbol value,
-     1. Use .got.plt in a shared object if it is forced local or not
+     branch, it uses .got.plt.  For symbol value, if PLT is used,
+     1. Use .got.plt in a PIC object if it is forced local or not
      dynamic.
-     2. Use .got.plt in a non-shared object if pointer equality isn't
+     2. Use .got.plt in a non-PIC object if pointer equality isn't
      needed.
      3. Use .got.plt in PIE.
      4. Use .got.plt if .got isn't used.
      5. Otherwise use .got so that it can be shared among different
      objects at run-time.
-     We only need to relocate .got entry in shared object.  */
-  if (h->got.refcount <= 0
-      || (bfd_link_pic (info)
-	  && (h->dynindx == -1
-	      || h->forced_local))
-      || (!bfd_link_pic (info)
-	  && !h->pointer_equality_needed)
-      || bfd_link_pie (info)
-      || htab->sgot == NULL)
+     If PLT isn't used, always use .got for symbol value.
+     We only need to relocate .got entry in PIC object or in dynamic
+     executable without PLT.  */
+  if (use_plt
+      && (h->got.refcount <= 0
+	  || (bfd_link_pic (info)
+	      && (h->dynindx == -1
+		  || h->forced_local))
+	  || (!bfd_link_pic (info)
+	      && !h->pointer_equality_needed)
+	  || bfd_link_pie (info)
+	  || htab->sgot == NULL))
     {
       /* Use .got.plt.  */
       h->got.offset = (bfd_vma) -1;
     }
   else
     {
-      h->got.offset = htab->sgot->size;
-      htab->sgot->size += got_entry_size;
-      if (bfd_link_pic (info))
-	htab->srelgot->size += sizeof_reloc;
+      if (!use_plt)
+	{
+	  /* PLT isn't used.  */
+	  h->plt.offset = (bfd_vma) -1;
+	}
+      if (h->got.refcount <= 0)
+	{
+	  /* GOT isn't need when there are only relocations for static
+	     pointers.  */
+	  h->got.offset = (bfd_vma) -1;
+	}
+      else
+	{
+	  h->got.offset = htab->sgot->size;
+	  htab->sgot->size += got_entry_size;
+	  /* Need to relocate the GOT entry in a PIC object or PLT isn't
+	     used.  Otherwise, the GOT entry will be filled with the PLT
+	     entry and dynamic GOT relocation isn't needed.  */
+	  if (need_dynreloc)
+	    {
+	      /* For non-static executable, dynamic GOT relocation is in
+		 .rel[a].got section, but for static executable, it is
+		 in .rel[a].iplt section.  */
+	      if (htab->splt != NULL)
+		htab->srelgot->size += sizeof_reloc;
+	      else
+		{
+		  relplt->size += sizeof_reloc;
+		  relplt->reloc_count++;
+		}
+	    }
+	}
     }
 
   return TRUE;