PowerPC inline PLT call support

In addition to the existing relocs we need two more to mark all
instructions in the call sequence, PLTCALL on the call itself (plus
the toc restore insn for ppc64), and PLTSEQ on others.  All
relocations in a particular sequence have the same symbol.

Example ppc64 ELFv2 assembly:
 .reloc .,R_PPC64_PLTSEQ,puts
	std 2,24(1)
	addis 12,2,puts@plt@ha	# .reloc .,R_PPC64_PLT16_HA,puts
	ld 12,puts@plt@l(12)	# .reloc .,R_PPC64_PLT16_LO_DS,puts
 .reloc .,R_PPC64_PLTSEQ,puts
	mtctr 12
 .reloc .,R_PPC64_PLTCALL,puts
	bctrl
	ld 2,24(1)

Example ppc32 -fPIC assembly:
	addis 12,30,puts+32768@plt@ha # .reloc .,R_PPC_PLT16_HA,puts+0x8000
	lwz 12,12,puts+32768@plt@l    # .reloc .,R_PPC_PLT16_LO,puts+0x8000
 .reloc .,R_PPC_PLTSEQ,puts+32768
	mtctr 12
 .reloc .,R_PPC_PLTCALL,puts+32768
	bctrl

Marking sequences like this allows the linker to convert them to nops
and a direct call if the target symbol turns out to be local.

When the call is __tls_get_addr, each relocation shown above is paired
with an R_PPC*_TLSLD or R_PPC*_TLSGD reloc to additionally mark the
sequence for possible TLS optimization.  The TLSLD or TLSGD relocs are
emitted first.

include/
	* elf/ppc.h (R_PPC_PLTSEQ, R_PPC_PLTCALL): Define.
	* elf/ppc64.h (R_PPC64_PLTSEQ, R_PPC64_PLTCALL): Define.
bfd/
	* elf32-ppc.c (ppc_elf_howto_raw): Add PLTSEQ and PLTCALL howtos.
	(is_plt_seq_reloc): New function.
	(ppc_elf_check_relocs): Handle PLTSEQ and PLTCALL relocs.
	(ppc_elf_tls_optimize): Handle inline plt call sequence.
	(ppc_elf_relax_section): Handle PLTCALL reloc.
	(ppc_elf_relocate_section): Nop out inline plt call sequence when
	resolving locally.
	* elf64-ppc.c (ppc64_elf_howto_raw): Add R_PPC64_PLTSEQ and
	R_PPC64_PLTCALL entries.  Comment R_PPC64_TOCSAVE.
	(has_tls_get_addr_call): Correct comment.
	(is_branch_reloc): Add PLTCALL.
	(is_plt_seq_reloc): New function.
	(ppc64_elf_check_relocs): Handle PLT16_LO_DS reloc.  Set
	has_tls_reloc for R_PPC64_TLSGD and R_PPC64_TLSLD.  Create plt
	entry for R_PPC64_PLTCALL.
	(ppc64_elf_tls_optimize): Handle inline plt call sequence.
	(ppc_type_of_stub): Handle PLTCALL reloc.
	(toc_adjusting_stub_needed): Likewise.
	(ppc64_elf_relocate_section): Set "can_plt_call" for PLTCALL
	reloc insn.  Nop out inline plt call sequence when resolving
	locally.  Handle __tls_get_addr inline plt call optimization.
elfcpp/
	* powerpc.h (R_POWERPC_PLTSEQ, R_POWERPC_PLTCALL): Define.
gold/
	* powerpc.cc (Target_powerpc::Track_tls::maybe_skip_tls_get_addr_call):
	Handle inline plt sequence relocs.
	(Stub_table::Plt_stub_key::Plt_stub_key): Likewise.
	(Target_powerpc::Scan::reloc_needs_plt_for_ifunc): Likewise.
	(Target_powerpc::Relocate::relocate): Likewise.

1 files changed, 143 insertions, 5 deletions

diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 5da7230..36a01ee 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -818,6 +818,35 @@ static reloc_howto_type ppc_elf_howto_raw[] = {
 	 0,			/* dst_mask */
 	 FALSE),		/* pcrel_offset */
 
+  /* Marker relocs on inline plt call instructions.  */
+  HOWTO (R_PPC_PLTSEQ,
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 bfd_elf_generic_reloc,	/* special_function */
+	 "R_PPC_PLTSEQ",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0,			/* src_mask */
+	 0,			/* dst_mask */
+	 FALSE),		/* pcrel_offset */
+
+  HOWTO (R_PPC_PLTCALL,
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 bfd_elf_generic_reloc,	/* special_function */
+	 "R_PPC_PLTCALL",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0,			/* src_mask */
+	 0,			/* dst_mask */
+	 FALSE),		/* pcrel_offset */
+
   /* Computes the load module index of the load module that contains the
      definition of its TLS sym.  */
   HOWTO (R_PPC_DTPMOD32,
@@ -3956,6 +3985,17 @@ is_branch_reloc (enum elf_ppc_reloc_type r_type)
 	  || r_type == R_PPC_VLE_REL24);
 }
 
+/* Relocs on inline plt call sequence insns prior to the call.  */
+
+static bfd_boolean
+is_plt_seq_reloc (enum elf_ppc_reloc_type r_type)
+{
+  return (r_type == R_PPC_PLT16_HA
+	  || r_type == R_PPC_PLT16_HI
+	  || r_type == R_PPC_PLT16_LO
+	  || r_type == R_PPC_PLTSEQ);
+}
+
 static void
 bad_shared_reloc (bfd *abfd, enum elf_ppc_reloc_type r_type)
 {
@@ -4131,6 +4171,9 @@ ppc_elf_check_relocs (bfd *abfd,
 	      return FALSE;
 	  break;
 
+	case R_PPC_PLTSEQ:
+	  break;
+
 	case R_PPC_GOT_TLSLD16:
 	case R_PPC_GOT_TLSLD16_LO:
 	case R_PPC_GOT_TLSLD16_HI:
@@ -4310,6 +4353,7 @@ ppc_elf_check_relocs (bfd *abfd,
 	  ppc_elf_tdata (abfd)->makes_plt_call = 1;
 	  /* Fall through */
 
+	case R_PPC_PLTCALL:
 	case R_PPC_PLT32:
 	case R_PPC_PLTREL32:
 	case R_PPC_PLT16_LO:
@@ -5437,6 +5481,40 @@ ppc_elf_tls_optimize (bfd *obfd ATTRIBUTE_UNUSED,
 
 		    case R_PPC_TLSGD:
 		    case R_PPC_TLSLD:
+		      if (rel + 1 < relend
+			  && is_plt_seq_reloc (ELF32_R_TYPE (rel[1].r_info)))
+			{
+			  if (pass != 0
+			      && ELF32_R_TYPE (rel[1].r_info) != R_PPC_PLTSEQ)
+			    {
+			      r_type = ELF32_R_TYPE (rel[1].r_info);
+			      r_symndx = ELF32_R_SYM (rel[1].r_info);
+			      if (r_symndx >= symtab_hdr->sh_info)
+				{
+				  struct elf_link_hash_entry **sym_hashes;
+
+				  sym_hashes = elf_sym_hashes (ibfd);
+				  h = sym_hashes[r_symndx - symtab_hdr->sh_info];
+				  while (h->root.type == bfd_link_hash_indirect
+					 || h->root.type == bfd_link_hash_warning)
+				    h = (struct elf_link_hash_entry *) h->root.u.i.link;
+				  if (h != NULL)
+				    {
+				      struct plt_entry *ent = NULL;
+				      bfd_vma addend = 0;
+
+				      if (bfd_link_pic (info))
+					addend = rel->r_addend;
+				      ent = find_plt_ent (&h->plt.plist,
+							  got2, addend);
+				      if (ent != NULL
+					  && ent->plt.refcount > 0)
+					ent->plt.refcount -= 1;
+				    }
+				}
+			    }
+			  continue;
+			}
 		      expecting_tls_get_addr = 2;
 		      tls_set = 0;
 		      tls_clear = 0;
@@ -5449,8 +5527,7 @@ ppc_elf_tls_optimize (bfd *obfd ATTRIBUTE_UNUSED,
 		  if (pass == 0)
 		    {
 		      if (!expecting_tls_get_addr
-			  || (expecting_tls_get_addr == 1
-			      && !sec->has_tls_get_addr_call))
+			  || !sec->has_tls_get_addr_call)
 			continue;
 
 		      if (rel + 1 < relend
@@ -5511,7 +5588,8 @@ ppc_elf_tls_optimize (bfd *obfd ATTRIBUTE_UNUSED,
 		      bfd_vma addend = 0;
 
 		      if (bfd_link_pic (info)
-			  && ELF32_R_TYPE (rel[1].r_info) == R_PPC_PLTREL24)
+			  && (ELF32_R_TYPE (rel[1].r_info) == R_PPC_PLTREL24
+			      || ELF32_R_TYPE (rel[1].r_info) == R_PPC_PLTCALL))
 			addend = rel[1].r_addend;
 		      ent = find_plt_ent (&htab->tls_get_addr->plt.plist,
 					  got2, addend);
@@ -7062,6 +7140,7 @@ ppc_elf_relax_section (bfd *abfd,
 	    case R_PPC_REL24:
 	    case R_PPC_LOCAL24PC:
 	    case R_PPC_PLTREL24:
+	    case R_PPC_PLTCALL:
 	      max_branch_offset = 1 << 25;
 	      break;
 
@@ -7890,7 +7969,7 @@ ppc_elf_relocate_section (bfd *output_bfd,
       unsigned long r_symndx;
       bfd_vma relocation;
       bfd_vma branch_bit, from;
-      bfd_boolean unresolved_reloc;
+      bfd_boolean unresolved_reloc, save_unresolved_reloc;
       bfd_boolean warned;
       unsigned int tls_type, tls_mask, tls_gd;
       struct plt_entry **ifunc, **plt_list;
@@ -8160,6 +8239,13 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	      unsigned int insn2;
 	      bfd_vma offset = rel->r_offset;
 
+	      if (is_plt_seq_reloc (ELF32_R_TYPE (rel[1].r_info)))
+		{
+		  bfd_put_32 (input_bfd, NOP, contents + offset);
+		  rel[1].r_info = ELF32_R_INFO (STN_UNDEF, R_PPC_NONE);
+		  break;
+		}
+
 	      if ((tls_mask & TLS_TPRELGD) != 0)
 		{
 		  /* IE */
@@ -8187,6 +8273,13 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	    {
 	      unsigned int insn2;
 
+	      if (is_plt_seq_reloc (ELF32_R_TYPE (rel[1].r_info)))
+		{
+		  bfd_put_32 (input_bfd, NOP, contents + rel->r_offset);
+		  rel[1].r_info = ELF32_R_INFO (STN_UNDEF, R_PPC_NONE);
+		  break;
+		}
+
 	      for (r_symndx = 0;
 		   r_symndx < symtab_hdr->sh_info;
 		   r_symndx++)
@@ -8230,7 +8323,7 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	case R_PPC_ADDR14_BRNTAKEN:
 	case R_PPC_REL14_BRNTAKEN:
 	  {
-	    bfd_vma insn;
+	    unsigned int insn;
 
 	    insn = bfd_get_32 (input_bfd, contents + rel->r_offset);
 	    insn &= ~BRANCH_PREDICT_BIT;
@@ -8464,6 +8557,7 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	}
 
       addend = rel->r_addend;
+      save_unresolved_reloc = unresolved_reloc;
       howto = NULL;
       if (r_type < R_PPC_max)
 	howto = ppc_elf_howto_table[r_type];
@@ -9244,6 +9338,8 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	  addend = 0;
 	  break;
 
+	case R_PPC_PLTSEQ:
+	case R_PPC_PLTCALL:
 	case R_PPC_PLT16_LO:
 	case R_PPC_PLT16_HI:
 	case R_PPC_PLT16_HA:
@@ -9644,6 +9740,48 @@ ppc_elf_relocate_section (bfd *output_bfd,
 	  goto copy_reloc;
 	}
 
+      switch (r_type)
+	{
+	default:
+	  break;
+
+	case R_PPC_PLTCALL:
+	  if (unresolved_reloc)
+	    {
+	      bfd_byte *p = contents + rel->r_offset;
+	      unsigned int insn = bfd_get_32 (input_bfd, p);
+	      insn &= 1;
+	      bfd_put_32 (input_bfd, B | insn, p);
+	      unresolved_reloc = save_unresolved_reloc;
+	      r_type = R_PPC_REL24;
+	      howto = ppc_elf_howto_table[r_type];
+	    }
+	  else if (htab->plt_type != PLT_NEW)
+	    info->callbacks->einfo
+	      (_("%P: %H: %s relocation unsupported for bss-plt\n"),
+	       input_bfd, input_section, rel->r_offset,
+	       howto->name);
+	  break;
+
+	case R_PPC_PLTSEQ:
+	case R_PPC_PLT16_HA:
+	case R_PPC_PLT16_LO:
+	  if (unresolved_reloc)
+	    {
+	      bfd_byte *p = contents + (rel->r_offset & ~3);
+	      bfd_put_32 (input_bfd, NOP, p);
+	      unresolved_reloc = FALSE;
+	      r_type = R_PPC_NONE;
+	      howto = ppc_elf_howto_table[r_type];
+	    }
+	  else if (htab->plt_type != PLT_NEW)
+	    info->callbacks->einfo
+	      (_("%P: %H: %s relocation unsupported for bss-plt\n"),
+	       input_bfd, input_section, rel->r_offset,
+	       howto->name);
+	  break;
+	}
+
       /* Do any further special processing.  */
       switch (r_type)
 	{