Add "-z call-nop=PADDING" option to ld

The ld linker can transform indirect call to a locally defined function,
foo, via its GOT slot, to either "NOP call foo" or "call foo NOP" where
NOP is a 1-byte NOP padding.  This patch adds a "-z call-nop=PADDING"
option to x86 ld to control 1-byte NOP padding for x86 call instruction.
PADDING is one of prefix-addr, prefix-nop, suffix-nop, prefix-NUMBER or
suffix-NUMBER.

bfd/

	* elf32-i386.c (elf_i386_convert_load): Use call_nop_byte and
	check call_nop_as_suffix for 1-byte NOP padding to pad call.
	* elf64-x86-64.c (elf_x86_64_convert_load): Likewise.

include/

	* bfdlink.h (bfd_link_info): Add call_nop_as_suffix and
	call_nop_byte.

ld/

	* ld/ld.texinfo: Document "-z call-nop=PADDING" option.
	* emulparams/call_nop.sh: New file.
	* emulparams/elf_i386_be.sh: Source
	${srcdir}/emulparams/call_nop.sh.
	* emulparams/elf_i386_chaos.sh: Likewise.
	* emulparams/elf_i386_ldso.sh: Likewise.
	* emulparams/elf_i386_vxworks.sh: Likewise.
	* emulparams/elf_iamcu.sh: Likewise.
	* emulparams/elf_k1om.sh: Likewise.
	* emulparams/elf_l1om.sh: Likewise.
	* emulparams/elf_x86_64.sh: Likewise.
	* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse): Set
	link_info.call_nop_byte if $CALL_NOP_BYTE isn't empty.

ld/testsuite/

	* ld-i386/call3.s: New file.
	* ld-i386/call3a.d: Likewise.
	* ld-i386/call3b.d: Likewise.
	* ld-i386/call3c.d: Likewise.
	* ld-i386/call3d.d: Likewise.
	* ld-i386/call3e.d: Likewise.
	* ld-i386/call3f.d: Likewise.
	* ld-i386/call3g.d: Likewise.
	* ld-i386/call3h.d: Likewise.
	* ld-i386/load1-nacl.d: Likewise.
	* ld-x86-64/call1.s: Likewise.
	* ld-x86-64/call1a.d: Likewise.
	* ld-x86-64/call1b.d: Likewise.
	* ld-x86-64/call1c.d: Likewise.
	* ld-x86-64/call1d.d: Likewise.
	* ld-x86-64/call1e.d: Likewise.
	* ld-x86-64/call1f.d: Likewise.
	* ld-x86-64/call1g.d: Likewise.
	* ld-x86-64/call1h.d: Likewise.
	* ld-x86-64/call1i.d: Likewise.
	* ld-x86-64/load1a-nacl.d: Likewise.
	* ld-x86-64/load1b-nacl.d: Likewise.
	* ld-x86-64/load1c-nacl.d: Likewise.
	* ld-x86-64/load1d-nacl.d: Likewise.

3 files changed, 25 insertions, 5 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index afc8029..961a385 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,11 @@
 2015-10-22  H.J. Lu  <hongjiu.lu@intel.com>
 
+	* elf32-i386.c (elf_i386_convert_load): Use call_nop_byte and
+	check call_nop_as_suffix for 1-byte NOP padding to pad call.
+	* elf64-x86-64.c (elf_x86_64_convert_load): Likewise.
+
+2015-10-22  H.J. Lu  <hongjiu.lu@intel.com>
+
 	* elf64-x86-64.c: Include opcode/i386.h.
 	(x86_64_elf_howto_table): Add R_X86_64_GOTPCRELX and
 	R_X86_64_REX_GOTPCRELX.
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index f56b39e..60cd91a 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -2924,8 +2924,14 @@ convert_branch:
 		  /* Convert to "nop call foo".  ADDR_PREFIX_OPCODE
 		     is a nop prefix.  */
 		  modrm = 0xe8;
-		  nop = ADDR_PREFIX_OPCODE;
-		  nop_offset = roff - 2;
+		  nop = link_info->call_nop_byte;
+		  if (link_info->call_nop_as_suffix)
+		    {
+		      nop_offset = roff + 3;
+		      irel->r_offset -= 1;
+		    }
+		  else
+		    nop_offset = roff - 2;
 		}
 	      else
 		{
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index f8bb0d5..f864834 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -3217,6 +3217,7 @@ elf_x86_64_convert_load (bfd *abfd, asection *sec,
 	{
 	  /* We have "call/jmp *foo@GOTPCREL(%rip)".  */
 	  unsigned int nop;
+	  unsigned int disp;
 	  bfd_vma nop_offset;
 
 	  /* Convert R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX to
@@ -3224,7 +3225,6 @@ elf_x86_64_convert_load (bfd *abfd, asection *sec,
 	  modrm = bfd_get_8 (abfd, contents + roff - 1);
 	  if (modrm == 0x25)
 	    {
-	      unsigned int disp;
 	      /* Convert to "jmp foo nop".  */
 	      modrm = 0xe9;
 	      nop = NOP_OPCODE;
@@ -3238,8 +3238,16 @@ elf_x86_64_convert_load (bfd *abfd, asection *sec,
 	      /* Convert to "nop call foo".  ADDR_PREFIX_OPCODE
 		 is a nop prefix.  */
 	      modrm = 0xe8;
-	      nop = ADDR_PREFIX_OPCODE;
-	      nop_offset = irel->r_offset - 2;
+	      nop = link_info->call_nop_byte;
+	      if (link_info->call_nop_as_suffix)
+		{
+		  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
+		nop_offset = irel->r_offset - 2;
 	    }
 	  bfd_put_8 (abfd, nop, contents + nop_offset);
 	  bfd_put_8 (abfd, modrm, contents + irel->r_offset - 1);