Add R_X86_64_[REX_]GOTPCRELX support to gas and ld

This patch adds support for the R_X86_64_GOTPCRELX and
R_X86_64_REX_GOTPCRELX relocations proposed in

https://groups.google.com/forum/#!topic/x86-64-abi/n9AWHogmVY0

to gas and ld.  It updates gas to generate R_X86_64_GOTPCRELX,
R_X86_64_REX_GOTPCRELX if there is a REX prefix, relocation for memory
operand, foo@GOTPCREL(%rip).  With the locally defined symbol, foo, we
convert

  mov foo@GOTPCREL(%rip), %reg

to

   lea foo(%rip), %reg

and convert

   call/jmp *foo@GOTPCREL(%rip)
to

   nop call foo/jmp foo nop

When PIC is false, convert

   test %reg, foo@GOTPCREL(%rip)
to

test $foo, %reg

and convert

   binop foo@GOTPCREL(%rip), %reg

to

   binop $foo, %reg

where binop is one of adc, add, and, cmp, or, sbb, sub, xor instructions.

bfd/

	* elf64-x86-64.c: Include opcode/i386.h.
	(x86_64_elf_howto_table): Add R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.
	(R_X86_64_standard): Replace R_X86_64_PLT32_BND with
	R_X86_64_REX_GOTPCRELX.
	(x86_64_reloc_map): Add BFD_RELOC_X86_64_GOTPCRELX and
	BFD_RELOC_X86_64_REX_GOTPCRELX.
	(need_convert_mov_to_lea): Renamed to ...
	(need_convert_load): This.
	(elf_x86_64_check_relocs): Handle R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.  Replace need_convert_mov_to_lea with
	need_convert_load.
	(elf_x86_64_gc_sweep_hook): Handle R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.
	(elf_x86_64_size_dynamic_sections): Likewise.
	(elf_x86_64_relocate_section): Likewise.
	(elf_x86_64_convert_mov_to_lea): Renamed to ...
	(elf_x86_64_convert_load): This.  Replace need_convert_mov_to_lea
	with need_convert_load.  Support R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX transformations.
	* reloc.c (BFD_RELOC_X86_64_GOTPCRELX): New.
	(BFD_RELOC_X86_64_REX_GOTPCRELX): Likewise.
	* bfd-in2.h: Regenerated.
	* libbfd.h: Likewise.

gas/

	* config/tc-i386.c (tc_i386_fix_adjustable): Handle
	BFD_RELOC_X86_64_GOTPCRELX and BFD_RELOC_X86_64_REX_GOTPCRELX.
	(tc_gen_reloc): Likewise.
	(i386_validate_fix): Generate BFD_RELOC_X86_64_GOTPCRELX or
	BFD_RELOC_X86_64_REX_GOTPCRELX if fx_tcbit2 is set.
	* config/tc-i386.h (TC_FORCE_RELOCATION_LOCAL): Also return
	true for BFD_RELOC_X86_64_GOTPCRELX and
	BFD_RELOC_X86_64_REX_GOTPCRELX.

gas/testsuite/

	* gas/i386/i386.exp: Run x86-64-gotpcrel.
	* gas/i386/x86-64-gotpcrel.d: New file.
	* gas/i386/x86-64-gotpcrel.s: Likewise.
	* gas/i386/ilp32/x86-64-gotpcrel.d: Likewise.
	* gas/i386/x86-64-localpic.d: Replace R_X86_64_GOTPCREL with
	R_X86_64_REX_GOTPCRELX.
	* gas/i386/ilp32/x86-64-localpic.d: Likewise.

include/elf/

	* x86-64.h (R_X86_64_GOTPCRELX): New.
	(R_X86_64_REX_GOTPCRELX): Likewise.

ld/testsuite/

	* ld-ifunc/ifunc-5r-local-x86-64.d: Replace R_X86_64_GOTPCREL
	with R_X86_64_REX_GOTPCRELX.
	* ld-x86-64/plt-main1.rd: Likewise.
	* ld-x86-64/plt-main3.rd: Likewise.
	* ld-x86-64/plt-main4.rd: Likewise.
	* ld-x86-64/gotpcrel1.dd: New file.
	* ld-x86-64/gotpcrel1.out: Likewise.
	* ld-x86-64/gotpcrel1a.S: Likewise.
	* ld-x86-64/gotpcrel1b.c: Likewise.
	* ld-x86-64/gotpcrel1c.c: Likewise.
	* ld-x86-64/gotpcrel1d.S: Likewise.
	* ld-x86-64/load1.s: Likewise.
	* ld-x86-64/load1a.d: Likewise.
	* ld-x86-64/load1b.d: Likewise.
	* ld-x86-64/load1c.d: Likewise.
	* ld-x86-64/load1d.d: Likewise.
	* ld-x86-64/x86-64.exp: Run load1a, load1b, load1c and load1d
	tests.  Run gotpcrel1 test.

1 files changed, 164 insertions, 30 deletions

diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index dc5fd0d..f8bb0d5 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -31,6 +31,7 @@
 #include "dwarf2.h"
 #include "libiberty.h"
 
+#include "opcode/i386.h"
 #include "elf/x86-64.h"
 
 #ifdef CORE_HEADER
@@ -176,12 +177,18 @@ static reloc_howto_type x86_64_elf_howto_table[] =
   HOWTO(R_X86_64_PLT32_BND, 0, 2, 32, TRUE, 0, complain_overflow_signed,
 	bfd_elf_generic_reloc, "R_X86_64_PLT32_BND", FALSE, 0xffffffff, 0xffffffff,
 	TRUE),
+  HOWTO(R_X86_64_GOTPCRELX, 0, 2, 32, TRUE, 0, complain_overflow_signed,
+	bfd_elf_generic_reloc, "R_X86_64_GOTPCRELX", FALSE, 0xffffffff,
+	0xffffffff, TRUE),
+  HOWTO(R_X86_64_REX_GOTPCRELX, 0, 2, 32, TRUE, 0, complain_overflow_signed,
+	bfd_elf_generic_reloc, "R_X86_64_REX_GOTPCRELX", FALSE, 0xffffffff,
+	0xffffffff, TRUE),
 
   /* We have a gap in the reloc numbers here.
      R_X86_64_standard counts the number up to this point, and
      R_X86_64_vt_offset is the value to subtract from a reloc type of
      R_X86_64_GNU_VT* to form an index into this table.  */
-#define R_X86_64_standard (R_X86_64_PLT32_BND + 1)
+#define R_X86_64_standard (R_X86_64_REX_GOTPCRELX + 1)
 #define R_X86_64_vt_offset (R_X86_64_GNU_VTINHERIT - R_X86_64_standard)
 
 /* GNU extension to record C++ vtable hierarchy.  */
@@ -253,8 +260,10 @@ static const struct elf_reloc_map x86_64_reloc_map[] =
   { BFD_RELOC_X86_64_TLSDESC_CALL, R_X86_64_TLSDESC_CALL, },
   { BFD_RELOC_X86_64_TLSDESC,	R_X86_64_TLSDESC, },
   { BFD_RELOC_X86_64_IRELATIVE,	R_X86_64_IRELATIVE, },
-  { BFD_RELOC_X86_64_PC32_BND,	R_X86_64_PC32_BND,},
-  { BFD_RELOC_X86_64_PLT32_BND,	R_X86_64_PLT32_BND,},
+  { BFD_RELOC_X86_64_PC32_BND,	R_X86_64_PC32_BND, },
+  { BFD_RELOC_X86_64_PLT32_BND,	R_X86_64_PLT32_BND, },
+  { BFD_RELOC_X86_64_GOTPCRELX, R_X86_64_GOTPCRELX, },
+  { BFD_RELOC_X86_64_REX_GOTPCRELX, R_X86_64_REX_GOTPCRELX, },
   { BFD_RELOC_VTABLE_INHERIT,	R_X86_64_GNU_VTINHERIT, },
   { BFD_RELOC_VTABLE_ENTRY,	R_X86_64_GNU_VTENTRY, },
 };
@@ -1545,7 +1554,7 @@ elf_x86_64_tls_transition (struct bfd_link_info *info, bfd *abfd,
 
 /* Rename some of the generic section flags to better document how they
    are used here.  */
-#define need_convert_mov_to_lea sec_flg0
+#define need_convert_load sec_flg0
 
 /* Look through the relocs for a section during the first phase, and
    calculate needed space in the global offset table, procedure
@@ -1726,6 +1735,8 @@ elf_x86_64_check_relocs (bfd *abfd, struct bfd_link_info *info,
 	    case R_X86_64_32S:
 	    case R_X86_64_PC64:
 	    case R_X86_64_GOTPCREL:
+	    case R_X86_64_GOTPCRELX:
+	    case R_X86_64_REX_GOTPCRELX:
 	    case R_X86_64_GOTPCREL64:
 	      if (htab->elf.dynobj == NULL)
 		htab->elf.dynobj = abfd;
@@ -1779,6 +1790,8 @@ elf_x86_64_check_relocs (bfd *abfd, struct bfd_link_info *info,
 
 	case R_X86_64_GOT32:
 	case R_X86_64_GOTPCREL:
+	case R_X86_64_GOTPCRELX:
+	case R_X86_64_REX_GOTPCRELX:
 	case R_X86_64_TLSGD:
 	case R_X86_64_GOT64:
 	case R_X86_64_GOTPCREL64:
@@ -2151,9 +2164,11 @@ do_size:
 	    return FALSE;
 	}
 
-      if (r_type == R_X86_64_GOTPCREL
+      if ((r_type == R_X86_64_GOTPCREL
+	   || r_type == R_X86_64_GOTPCRELX
+	   || r_type == R_X86_64_REX_GOTPCRELX)
 	  && (h == NULL || h->type != STT_GNU_IFUNC))
-	sec->need_convert_mov_to_lea = 1;
+	sec->need_convert_load = 1;
     }
 
   return TRUE;
@@ -2279,6 +2294,8 @@ elf_x86_64_gc_sweep_hook (bfd *abfd, struct bfd_link_info *info,
 	case R_X86_64_GOTTPOFF:
 	case R_X86_64_GOT32:
 	case R_X86_64_GOTPCREL:
+	case R_X86_64_GOTPCRELX:
+	case R_X86_64_REX_GOTPCRELX:
 	case R_X86_64_GOT64:
 	case R_X86_64_GOTPCREL64:
 	case R_X86_64_GOTPLT64:
@@ -2953,15 +2970,28 @@ elf_x86_64_readonly_dynrelocs (struct elf_link_hash_entry *h,
   return TRUE;
 }
 
-/* Convert
+/* With the local symbol, foo, we convert
    mov foo@GOTPCREL(%rip), %reg
    to
    lea foo(%rip), %reg
-   with the local symbol, foo.  */
+   and convert
+   call/jmp *foo@GOTPCREL(%rip)
+   to
+   nop call foo/jmp foo nop
+   When PIC is false, convert
+   test %reg, foo@GOTPCREL(%rip)
+   to
+   test $foo, %reg
+   and convert
+   binop foo@GOTPCREL(%rip), %reg
+   to
+   binop $foo, %reg
+   where binop is one of adc, add, and, cmp, or, sbb, sub, xor
+   instructions.  */
 
 static bfd_boolean
-elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
-			       struct bfd_link_info *link_info)
+elf_x86_64_convert_load (bfd *abfd, asection *sec,
+			 struct bfd_link_info *link_info)
 {
   Elf_Internal_Shdr *symtab_hdr;
   Elf_Internal_Rela *internal_relocs;
@@ -2979,7 +3009,7 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 
   /* Nothing to do if there is no need or no output.  */
   if ((sec->flags & (SEC_CODE | SEC_RELOC)) != (SEC_CODE | SEC_RELOC)
-      || sec->need_convert_mov_to_lea == 0
+      || sec->need_convert_load == 0
       || bfd_is_abs_section (sec->output_section))
     return TRUE;
 
@@ -3017,22 +3047,45 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
       asection *tsec;
       char symtype;
       bfd_vma toff, roff;
+      bfd_signed_vma raddend;
       unsigned int opcode;
+      unsigned int modrm;
 
-      if (r_type != R_X86_64_GOTPCREL)
+      if (r_type != R_X86_64_GOTPCREL
+	  && r_type != R_X86_64_GOTPCRELX
+	  && r_type != R_X86_64_REX_GOTPCRELX)
 	continue;
 
       roff = irel->r_offset;
+      if (roff < (r_type == R_X86_64_REX_GOTPCRELX ? 3 : 2))
+	continue;
 
-      if (roff < 2)
+      raddend = irel->r_addend;
+      /* Addend for 32-bit PC-relative relocation must be -4.  */
+      if (raddend != -4)
 	continue;
 
       opcode = bfd_get_8 (abfd, contents + roff - 2);
 
-      /* PR ld/18591: Don't convert R_X86_64_GOTPCREL relocation if it
-         isn't for mov instruction.  */
+      /* It is OK to convert mov to lea.  */
       if (opcode != 0x8b)
-	continue;
+	{
+	  /* Only convert R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX
+	     for mov call, jmp or one of adc, add, and, cmp, or, sbb,
+	     sub, test, xor instructions.  */
+	  if (r_type != R_X86_64_GOTPCRELX
+	      && r_type != R_X86_64_REX_GOTPCRELX)
+	    continue;
+
+	  /* It is OK to convert indirect branch to direct branch.  */
+	  if (opcode != 0xff)
+	    {
+	      /* It is OK to convert adc, add, and, cmp, or, sbb, sub,
+		 test, xor only when PIC is false.   */
+	      if (bfd_link_pic (link_info))
+		continue;
+	    }
+	}
 
       /* Get the symbol referred to by the reloc.  */
       if (r_symndx < symtab_hdr->sh_info)
@@ -3044,8 +3097,8 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 
 	  symtype = ELF_ST_TYPE (isym->st_info);
 
-	  /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation and
-	     skip relocation against undefined symbols.  */
+	  /* STT_GNU_IFUNC must keep GOTPCREL relocations and skip
+	     relocation against undefined symbols.  */
 	  if (symtype == STT_GNU_IFUNC || isym->st_shndx == SHN_UNDEF)
 	    continue;
 
@@ -3071,9 +3124,9 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 		 || h->root.type == bfd_link_hash_warning)
 	    h = (struct elf_link_hash_entry *) h->root.u.i.link;
 
-	  /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation.  We also
-	     avoid optimizing _DYNAMIC since ld.so may use its link-time
-	     address.  */
+	  /* STT_GNU_IFUNC must keep GOTPCREL relocations.  We also
+	     avoid optimizing GOTPCREL relocations againt _DYNAMIC
+	     since ld.so may use its link-time address.  */
 	  if ((h->root.type == bfd_link_hash_defined
 	       || h->root.type == bfd_link_hash_defweak)
 	      && h->type != STT_GNU_IFUNC
@@ -3107,17 +3160,17 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 	     access is presumed to be an offset from "sym";  The
 	     location of interest is just "sym".  */
 	   if (symtype == STT_SECTION)
-	     toff += irel->r_addend;
+	     toff += raddend;
 
 	   toff = _bfd_merged_section_offset (abfd, &tsec,
 					      elf_section_data (tsec)->sec_info,
 					      toff);
 
 	   if (symtype != STT_SECTION)
-	     toff += irel->r_addend;
+	     toff += raddend;
 	}
       else
-	toff += irel->r_addend;
+	toff += raddend;
 
       /* Don't convert if R_X86_64_PC32 relocation overflows.  */
       if (tsec->output_section == sec->output_section)
@@ -3148,8 +3201,8 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 		}
 	    }
 
-	  /* Don't convert R_X86_64_GOTPCREL if TSEC isn't placed after
-	     SEC.  */
+	  /* Don't convert GOTPCREL relocations if TSEC isn't placed
+	     after SEC.  */
 	  if (asect == NULL)
 	    continue;
 
@@ -3160,8 +3213,82 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
 	    continue;
 	}
 
-      bfd_put_8 (abfd, 0x8d, contents + roff - 2);
-      irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
+      if (opcode == 0xff)
+	{
+	  /* We have "call/jmp *foo@GOTPCREL(%rip)".  */
+	  unsigned int nop;
+	  bfd_vma nop_offset;
+
+	  /* Convert R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX to
+	     R_X86_64_PC32.  */
+	  modrm = bfd_get_8 (abfd, contents + roff - 1);
+	  if (modrm == 0x25)
+	    {
+	      unsigned int disp;
+	      /* Convert to "jmp foo nop".  */
+	      modrm = 0xe9;
+	      nop = NOP_OPCODE;
+	      nop_offset = irel->r_offset + 3;
+	      disp = bfd_get_32 (abfd, contents + irel->r_offset);
+	      irel->r_offset -= 1;
+	      bfd_put_32 (abfd, disp, contents + irel->r_offset);
+	    }
+	  else
+	    {
+	      /* Convert to "nop call foo".  ADDR_PREFIX_OPCODE
+		 is a nop prefix.  */
+	      modrm = 0xe8;
+	      nop = ADDR_PREFIX_OPCODE;
+	      nop_offset = irel->r_offset - 2;
+	    }
+	  bfd_put_8 (abfd, nop, contents + nop_offset);
+	  bfd_put_8 (abfd, modrm, contents + irel->r_offset - 1);
+	  r_type = R_X86_64_PC32;
+	}
+      else
+	{
+	  if (opcode == 0x8b)
+	    {
+	      /* Convert "mov foo@GOTPCREL(%rip), %reg" to
+		 "lea foo(%rip), %reg".  */
+	      opcode = 0x8d;
+	      r_type = R_X86_64_PC32;
+	    }
+	  else
+	    {
+	      modrm = bfd_get_8 (abfd, contents + roff - 1);
+	      if (opcode == 0x85)
+		{
+		  /* Convert "test %reg, foo@GOTPCREL(%rip)" to
+		     "test $foo, %reg".  */
+		  modrm = 0xc0 | (modrm & 0x38) >> 3;
+		  opcode = 0xf7;
+		}
+	      else
+		{
+		  /* Convert "binop foo@GOTPCREL(%rip), %reg" to
+		     "binop $foo, %reg".  */
+		  modrm = 0xc0 | (modrm & 0x38) >> 3 | (opcode & 0x3c);
+		  opcode = 0x81;
+		}
+	      bfd_put_8 (abfd, modrm, contents + roff - 1);
+
+	      if (r_type == R_X86_64_REX_GOTPCRELX)
+		{
+		  /* Move the R bit to the B bit in REX byte.  */
+		  unsigned int rex = bfd_get_8 (abfd, contents + roff - 3);
+		  rex = (rex & ~REX_R) | (rex & REX_R) >> 2;
+		  bfd_put_8 (abfd, rex, contents + roff - 3);
+		}
+	      /* No addend for R_X86_64_32S relocation.  */
+	      irel->r_addend = 0;
+	      r_type = R_X86_64_32S;
+	    }
+
+	  bfd_put_8 (abfd, opcode, contents + roff - 2);
+	}
+
+      irel->r_info = htab->r_info (r_symndx, r_type);
       changed_contents = TRUE;
       changed_relocs = TRUE;
 
@@ -3264,7 +3391,7 @@ elf_x86_64_size_dynamic_sections (bfd *output_bfd,
 	{
 	  struct elf_dyn_relocs *p;
 
-	  if (!elf_x86_64_convert_mov_to_lea (ibfd, s, info))
+	  if (!elf_x86_64_convert_load (ibfd, s, info))
 	    return FALSE;
 
 	  for (p = (struct elf_dyn_relocs *)
@@ -3985,6 +4112,8 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 	      goto do_relocation;
 
 	    case R_X86_64_GOTPCREL:
+	    case R_X86_64_GOTPCRELX:
+	    case R_X86_64_REX_GOTPCRELX:
 	    case R_X86_64_GOTPCREL64:
 	      base_got = htab->elf.sgot;
 	      off = h->got.offset;
@@ -4053,6 +4182,8 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 	  /* Relocation is to the entry for this symbol in the global
 	     offset table.  */
 	case R_X86_64_GOTPCREL:
+	case R_X86_64_GOTPCRELX:
+	case R_X86_64_REX_GOTPCRELX:
 	case R_X86_64_GOTPCREL64:
 	  /* Use global offset table entry as symbol value.  */
 	case R_X86_64_GOTPLT64:
@@ -4158,7 +4289,10 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 
 	  relocation = base_got->output_section->vma
 		       + base_got->output_offset + off;
-	  if (r_type != R_X86_64_GOTPCREL && r_type != R_X86_64_GOTPCREL64)
+	  if (r_type != R_X86_64_GOTPCREL
+	      && r_type != R_X86_64_GOTPCRELX
+	      && r_type != R_X86_64_REX_GOTPCRELX
+	      && r_type != R_X86_64_GOTPCREL64)
 	    relocation -= htab->elf.sgotplt->output_section->vma
 			  - htab->elf.sgotplt->output_offset;