Keep .plt section and DT_PLTGOT for prelink

Since the .plt section and DT_PLTGOT are used by prelink to undo
prelinking for dynamic relocations, we must keep them even if there is
no PLT relocation.  This patch reverted commit a3747075a.

bfd/

	* elf32-i386.c (elf_i386_allocate_dynrelocs): Always allocate
	space for the first .plt entry.
	(elf_i386_size_dynamic_sections): Always add DT_PLTGOT for .plt
	section.  Add DT_PLTRELSZ, DT_PLTREL and DT_JMPREL only if
	there are PLT relocations.
	* elf64-x86-64.c (elf_x86_64_allocate_dynrelocs): Always
	allocate space for the first .plt entry.
	(elf_x86_64_size_dynamic_sections): Always add DT_PLTGOT for
	.plt section.  Add DT_PLTRELSZ, DT_PLTREL and DT_JMPREL only if
	there are PLT relocations.

ld/testsuite/

	* ld-i386/i386.exp: Run pltgot-2 for Linux targets.
	* ld-x86-64/x86-64.exp: Likewise.
	* ld-i386/pltgot-1.d: Updated.
	* ld-x86-64/pltgot-1.d: Likewise.
	* ld-i386/pltgot-2.d: New file.
	* ld-x86-64/pltgot-2.d: Likewise.

bfd/ChangeLog

@@ -1,3 +1,16 @@
+2015-06-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* elf32-i386.c (elf_i386_allocate_dynrelocs): Always allocate
+	space for the first .plt entry.
+	(elf_i386_size_dynamic_sections): Always add DT_PLTGOT for .plt
+	section.  Add DT_PLTRELSZ, DT_PLTREL and DT_JMPREL only if
+	there are PLT relocations.
+	* elf64-x86-64.c (elf_x86_64_allocate_dynrelocs): Always
+	allocate space for the first .plt entry.
+	(elf_x86_64_size_dynamic_sections): Always add DT_PLTGOT for
+	.plt section.  Add DT_PLTRELSZ, DT_PLTREL and DT_JMPREL only if
+	there are PLT relocations.
+
 2015-06-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/18591

bfd/elf32-i386.c

@@ -2351,16 +2351,16 @@ elf_i386_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
 	  asection *s = htab->elf.splt;
 	  asection *got_s = htab->plt_got;
 
+	  /* If this is the first .plt entry, make room for the special
+	     first entry.  The .plt section is used by prelink to undo
+	     prelinking for dynamic relocations.  */
+	  if (s->size == 0)
+	    s->size = plt_entry_size;
+
 	  if (use_plt_got)
 	    eh->plt_got.offset = got_s->size;
 	  else
-	    {
-	      /* If this is the first .plt entry, make room for the
-		 special first entry.  */
-	      if (s->size == 0)
-		s->size = plt_entry_size;
 	    h->plt.offset = s->size;
-	    }
 
 	  /* If this symbol is not defined in a regular file, and we are
 	     not generating a shared library, then set the symbol to this
@@ -3119,12 +3119,19 @@ elf_i386_size_dynamic_sections (bfd *output_bfd, struct bfd_link_info *info)
 
       if (htab->elf.splt->size != 0)
 	{
-	  if (!add_dynamic_entry (DT_PLTGOT, 0)
+	  /* DT_PLTGOT is used by prelink even if there is no PLT
-	      || !add_dynamic_entry (DT_PLTRELSZ, 0)
+	     relocation.  */
+	  if (!add_dynamic_entry (DT_PLTGOT, 0))
+	    return FALSE;
+
+	  if (htab->elf.srelplt->size != 0)
+	    {
+	      if (!add_dynamic_entry (DT_PLTRELSZ, 0)
 		  || !add_dynamic_entry (DT_PLTREL, DT_REL)
 		  || !add_dynamic_entry (DT_JMPREL, 0))
 		return FALSE;
 	    }
+	}
 
       if (relocs)
 	{

bfd/elf64-x86-64.c

@@ -2571,14 +2571,16 @@ elf_x86_64_allocate_dynrelocs (struct elf_link_hash_entry *h, void * inf)
 	  asection *bnd_s = htab->plt_bnd;
 	  asection *got_s = htab->plt_got;
 
+	  /* If this is the first .plt entry, make room for the special
+	     first entry.  The .plt section is used by prelink to undo
+	     prelinking for dynamic relocations.  */
+	  if (s->size == 0)
+	    s->size = plt_entry_size;
+
 	  if (use_plt_got)
 	    eh->plt_got.offset = got_s->size;
 	  else
 	    {
-	      /* If this is the first .plt entry, make room for the
-		 special first entry.  */
-	      if (s->size == 0)
-		s->size = plt_entry_size;
 	      h->plt.offset = s->size;
 	      if (bnd_s)
 		eh->plt_bnd.offset = bnd_s->size;
@@ -3464,11 +3466,18 @@ elf_x86_64_size_dynamic_sections (bfd *output_bfd,
 
       if (htab->elf.splt->size != 0)
 	{
-	  if (!add_dynamic_entry (DT_PLTGOT, 0)
+	  /* DT_PLTGOT is used by prelink even if there is no PLT
-	      || !add_dynamic_entry (DT_PLTRELSZ, 0)
+	     relocation.  */
+	  if (!add_dynamic_entry (DT_PLTGOT, 0))
+	    return FALSE;
+
+	  if (htab->elf.srelplt->size != 0)
+	    {
+	      if (!add_dynamic_entry (DT_PLTRELSZ, 0)
 		  || !add_dynamic_entry (DT_PLTREL, DT_RELA)
 		  || !add_dynamic_entry (DT_JMPREL, 0))
 		return FALSE;
+	    }
 
 	  if (htab->tlsdesc_plt
 	      && (!add_dynamic_entry (DT_TLSDESC_PLT, 0)

ld/testsuite/ChangeLog

@@ -1,3 +1,12 @@
+2015-06-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* ld-i386/i386.exp: Run pltgot-2 for Linux targets.
+	* ld-x86-64/x86-64.exp: Likewise.
+	* ld-i386/pltgot-1.d: Updated.
+	* ld-x86-64/pltgot-1.d: Likewise.
+	* ld-i386/pltgot-2.d: New file.
+	* ld-x86-64/pltgot-2.d: Likewise.
+
 2015-06-23  Jiong Wang  <jiong.wang@arm.com>
 
 	* ld-aarch64/dt_textrel.s: New testcase.

ld/testsuite/ld-i386/i386.exp

@@ -525,3 +525,4 @@ if { !([istarget "i?86-*-linux*"]
 
 # Linux only tests
 run_dump_test "pltgot-1"
+run_dump_test "pltgot-2"

ld/testsuite/ld-i386/pltgot-1.d

@@ -2,7 +2,8 @@
 #readelf: -S --wide
 #as: --32
 
-#failif
 #...
- +\[ [0-9]+\] \.plt +PROGBITS +.*
+ +\[ *[0-9]+\] \.plt +PROGBITS +[0-9a-f]+ +[0-9a-f]+ +0+10 +.*
 #...
+ +\[ *[0-9]+\] \.got\.plt +PROGBITS +[0-9a-f]+ +[0-9a-f]+ +0+c +.*
+#pass

ld/testsuite/ld-i386/pltgot-2.d

@@ -0,0 +1,9 @@
+#source: pltgot-1.s
+#ld: -shared -melf_i386
+#readelf: -d --wide
+#as: --32
+
+#failif
+#...
+ +0x[0-9a-f]+ +\(PLTREL.*
+#...

ld/testsuite/ld-x86-64/pltgot-1.d

@@ -2,7 +2,8 @@
 #readelf: -S --wide
 #as: --64
 
-#failif
 #...
- +\[ [0-9]+\] \.plt +PROGBITS +.*
+ +\[ *[0-9]+\] \.plt +PROGBITS +[0-9a-f]+ +[0-9a-f]+ +0+10 +.*
 #...
+ +\[ *[0-9]+\] \.got\.plt +PROGBITS +[0-9a-f]+ +[0-9a-f]+ +0+18 +.*
+#pass

ld/testsuite/ld-x86-64/pltgot-2.d

@@ -0,0 +1,9 @@
+#source: pltgot-1.s
+#ld: -shared -melf_x86_64
+#readelf: -d --wide
+#as: --64
+
+#failif
+#...
+ +0x[0-9a-f]+ +\(PLTREL.*
+#...

ld/testsuite/ld-x86-64/x86-64.exp

@@ -574,3 +574,4 @@ if { ![istarget "x86_64-*-linux*"]} {
 # Linux only tests
 run_dump_test "pr17618"
 run_dump_test "pltgot-1"
+run_dump_test "pltgot-2"