PR27625, powerpc64 gold __tls_get_addr calls

This patch supports linking powerpc64 glibc with gold, specifically
the __tls_get_addr call in elf/dl-sym.c.  That call lacks marker
relocations tying it to the arg setup instructions, but the arg setup
insns are also contructed lacking the usual relocations on a Global
Dynamic TLS code sequence.  So there is no chance that anything in
that sequence might be wrongly edited by the linker.

In fact, the aim of linking glibc could have been supported by simply
omitting the error whenever TLS optimisation is disabled, as it is
when linking a shared library.  The patch goes further than that,
disabling TLS GD and LD sequence optimisation on a per-object basis
for object files lacking marker relocs.

	PR gold/27625
	* powerpc.cc (Powerpc_relobj): Add no_tls_marker_, tls_marker_,
	and tls_opt_error_ variables and accessors.
	(Target_powerpc::Scan::local, global): Call set_tls_marker and
	set_no_tls_marker for GD and LD code sequence relocations.
	(Target_powerpc::Relocate::relocate): Downgrade the "lacks marker
	reloc" error to a warning when safe to do so, and omit the error
	entirely if not optimising TLS sequences.  Do not optimise GD and
	LD sequences for objects lacking marker relocs.
	(Target_powerpc::relocate_relocs): Heed no_tls_marker here too.

gold/ChangeLog

@@ -1,3 +1,16 @@
+2021-03-30  Alan Modra  <amodra@gmail.com>
+
+	PR gold/27625
+	* powerpc.cc (Powerpc_relobj): Add no_tls_marker_, tls_marker_,
+	and tls_opt_error_ variables and accessors.
+	(Target_powerpc::Scan::local, global): Call set_tls_marker and
+	set_no_tls_marker for GD and LD code sequence relocations.
+	(Target_powerpc::Relocate::relocate): Downgrade the "lacks marker
+	reloc" error to a warning when safe to do so, and omit the error
+	entirely if not optimising TLS sequences.  Do not optimise GD and
+	LD sequences for objects lacking marker relocs.
+	(Target_powerpc::relocate_relocs): Heed no_tls_marker here too.
+
 2021-03-19  Cary Coutant  <ccoutant@gmail.com>
 
 	PR gold/27615

gold/powerpc.cc

@@ -101,6 +101,7 @@ public:
     : Sized_relobj_file<size, big_endian>(name, input_file, offset, ehdr),
       uniq_(object_id++), special_(0), relatoc_(0), toc_(0),
       has_small_toc_reloc_(false), opd_valid_(false),
+      no_tls_marker_(false), tls_marker_(false), tls_opt_error_(false),
       e_flags_(ehdr.get_e_flags()), no_toc_opt_(), opd_ent_(),
       access_from_map_(), has14_(), stub_table_index_(), st_other_(),
       attributes_section_data_(NULL)
@@ -161,6 +162,30 @@ public:
     return this->no_toc_opt_[off];
   }
 
+  void
+  set_no_tls_marker()
+  {
+    if (!this->no_tls_marker_ && this->tls_marker_)
+      this->tls_opt_error_ = true;
+    this->no_tls_marker_ = true;
+  }
+
+  bool
+  no_tls_marker() const
+  { return this->no_tls_marker_; }
+
+  void
+  set_tls_marker()
+  { this->tls_marker_ = true; }
+
+  bool
+  tls_marker() const
+  { return this->tls_marker_; }
+
+  bool
+  tls_opt_error() const
+  { return this->tls_opt_error_; }
+
   // The .got2 section shndx.
   unsigned int
   got2_shndx() const
@@ -454,6 +479,19 @@ private:
   // access_from_map_.
   bool opd_valid_;
 
+  // Set when finding a __tls_get_addr call without marker relocs.
+  // Such a call disables GD and LD tls optimisations for the object file.
+  bool no_tls_marker_;
+
+  // Set when finding a __tls_get_addr call with marker relocs, or
+  // when finding a relocation that needs __tls_get_addr calls with
+  // marker relocs.
+  bool tls_marker_;
+
+  // Set when seeing a __tls_get_addr call without marker relocs after
+  // seeing some __tls_get_addr calls with marker relocs.
+  bool tls_opt_error_;
+
   // Header e_flags
   elfcpp::Elf_Word e_flags_;
 
@@ -7863,28 +7901,47 @@ Target_powerpc<size, big_endian>::Scan::local(
     const elfcpp::Sym<size, big_endian>& lsym,
     bool is_discarded)
 {
-  this->maybe_skip_tls_get_addr_call(target, r_type, NULL);
+  Powerpc_relobj<size, big_endian>* ppc_object
+    = static_cast<Powerpc_relobj<size, big_endian>*>(object);
+
+  switch (this->maybe_skip_tls_get_addr_call(target, r_type, NULL))
+    {
+    case Track_tls::NOT_EXPECTED:
+      ppc_object->set_no_tls_marker();
+      break;
+    default:
+      break;
+    }
 
   if ((size == 64 && r_type == elfcpp::R_PPC64_TLSGD)
       || (size == 32 && r_type == elfcpp::R_PPC_TLSGD))
     {
       this->expect_tls_get_addr_call();
-      const tls::Tls_optimization tls_type = target->optimize_tls_gd(true);
+      if (!ppc_object->no_tls_marker())
-      if (tls_type != tls::TLSOPT_NONE)
+	{
-	this->skip_next_tls_get_addr_call();
+	  tls::Tls_optimization tls_type = target->optimize_tls_gd(true);
+	  if (tls_type != tls::TLSOPT_NONE)
+	    {
+	      this->skip_next_tls_get_addr_call();
+	      ppc_object->set_tls_marker();
+	    }
+	}
     }
   else if ((size == 64 && r_type == elfcpp::R_PPC64_TLSLD)
 	   || (size == 32 && r_type == elfcpp::R_PPC_TLSLD))
     {
       this->expect_tls_get_addr_call();
-      const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+      if (!ppc_object->no_tls_marker())
-      if (tls_type != tls::TLSOPT_NONE)
+	{
-	this->skip_next_tls_get_addr_call();
+	  tls::Tls_optimization tls_type = target->optimize_tls_ld();
+	  if (tls_type != tls::TLSOPT_NONE)
+	    {
+	      this->skip_next_tls_get_addr_call();
+	      ppc_object->set_tls_marker();
+	    }
+	}
     }
 
-  Powerpc_relobj<size, big_endian>* ppc_object
-    = static_cast<Powerpc_relobj<size, big_endian>*>(object);
-
   if (is_discarded)
     {
       if (size == 64
@@ -8179,7 +8236,9 @@ Target_powerpc<size, big_endian>::Scan::local(
     case elfcpp::R_POWERPC_GOT_TLSGD16_HI:
     case elfcpp::R_POWERPC_GOT_TLSGD16_HA:
       {
-	const tls::Tls_optimization tls_type = target->optimize_tls_gd(true);
+	tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+	if (!ppc_object->no_tls_marker())
+	  tls_type = target->optimize_tls_gd(true);
 	if (tls_type == tls::TLSOPT_NONE)
 	  {
 	    Output_data_got_powerpc<size, big_endian>* got
@@ -8192,6 +8251,7 @@ Target_powerpc<size, big_endian>::Scan::local(
 	else if (tls_type == tls::TLSOPT_TO_LE)
 	  {
 	    // no GOT relocs needed for Local Exec.
+	    ppc_object->set_tls_marker();
 	  }
 	else
 	  gold_unreachable();
@@ -8204,7 +8264,9 @@ Target_powerpc<size, big_endian>::Scan::local(
     case elfcpp::R_POWERPC_GOT_TLSLD16_HI:
     case elfcpp::R_POWERPC_GOT_TLSLD16_HA:
       {
-	const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+	tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+	if (!ppc_object->no_tls_marker())
+	  tls_type = target->optimize_tls_ld();
 	if (tls_type == tls::TLSOPT_NONE)
 	  target->tlsld_got_offset(symtab, layout, object);
 	else if (tls_type == tls::TLSOPT_TO_LE)
@@ -8216,6 +8278,7 @@ Target_powerpc<size, big_endian>::Scan::local(
 		gold_assert(os != NULL);
 		os->set_needs_symtab_index();
 	      }
+	    ppc_object->set_tls_marker();
 	  }
 	else
 	  gold_unreachable();
@@ -8241,7 +8304,7 @@ Target_powerpc<size, big_endian>::Scan::local(
     case elfcpp::R_POWERPC_GOT_TPREL16_HI:
     case elfcpp::R_POWERPC_GOT_TPREL16_HA:
       {
-	const tls::Tls_optimization tls_type = target->optimize_tls_ie(true);
+	tls::Tls_optimization tls_type = target->optimize_tls_ie(true);
 	if (tls_type == tls::TLSOPT_NONE)
 	  {
 	    unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());
@@ -8545,9 +8608,19 @@ Target_powerpc<size, big_endian>::Scan::global(
     unsigned int r_type,
     Symbol* gsym)
 {
-  if (this->maybe_skip_tls_get_addr_call(target, r_type, gsym)
+  Powerpc_relobj<size, big_endian>* ppc_object
-      == Track_tls::SKIP)
+    = static_cast<Powerpc_relobj<size, big_endian>*>(object);
-    return;
+
+  switch (this->maybe_skip_tls_get_addr_call(target, r_type, gsym))
+    {
+    case Track_tls::NOT_EXPECTED:
+      ppc_object->set_no_tls_marker();
+      break;
+    case Track_tls::SKIP:
+      return;
+    default:
+      break;
+    }
 
   if (target->replace_tls_get_addr(gsym))
     // Change a __tls_get_addr reference to __tls_get_addr_opt
@@ -8558,23 +8631,32 @@ Target_powerpc<size, big_endian>::Scan::global(
       || (size == 32 && r_type == elfcpp::R_PPC_TLSGD))
     {
       this->expect_tls_get_addr_call();
-      const bool final = gsym->final_value_is_known();
+      if (!ppc_object->no_tls_marker())
-      const tls::Tls_optimization tls_type = target->optimize_tls_gd(final);
+	{
-      if (tls_type != tls::TLSOPT_NONE)
+	  bool final = gsym->final_value_is_known();
-	this->skip_next_tls_get_addr_call();
+	  tls::Tls_optimization tls_type = target->optimize_tls_gd(final);
+	  if (tls_type != tls::TLSOPT_NONE)
+	    {
+	      this->skip_next_tls_get_addr_call();
+	      ppc_object->set_tls_marker();
+	    }
+	}
     }
   else if ((size == 64 && r_type == elfcpp::R_PPC64_TLSLD)
 	   || (size == 32 && r_type == elfcpp::R_PPC_TLSLD))
     {
       this->expect_tls_get_addr_call();
-      const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+      if (!ppc_object->no_tls_marker())
-      if (tls_type != tls::TLSOPT_NONE)
+	{
-	this->skip_next_tls_get_addr_call();
+	  tls::Tls_optimization tls_type = target->optimize_tls_ld();
+	  if (tls_type != tls::TLSOPT_NONE)
+	    {
+	      this->skip_next_tls_get_addr_call();
+	      ppc_object->set_tls_marker();
+	    }
+	}
     }
 
-  Powerpc_relobj<size, big_endian>* ppc_object
-    = static_cast<Powerpc_relobj<size, big_endian>*>(object);
-
   // A STT_GNU_IFUNC symbol may require a PLT entry.
   bool is_ifunc = gsym->type() == elfcpp::STT_GNU_IFUNC;
   bool pushed_ifunc = false;
@@ -8951,8 +9033,12 @@ Target_powerpc<size, big_endian>::Scan::global(
     case elfcpp::R_POWERPC_GOT_TLSGD16_HI:
     case elfcpp::R_POWERPC_GOT_TLSGD16_HA:
       {
-	const bool final = gsym->final_value_is_known();
+	tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
-	const tls::Tls_optimization tls_type = target->optimize_tls_gd(final);
+	if (!ppc_object->no_tls_marker())
+	  {
+	    bool final = gsym->final_value_is_known();
+	    tls_type = target->optimize_tls_gd(final);
+	  }
 	if (tls_type == tls::TLSOPT_NONE)
 	  {
 	    Output_data_got_powerpc<size, big_endian>* got
@@ -8984,10 +9070,12 @@ Target_powerpc<size, big_endian>::Scan::global(
 							   got, off, 0);
 		  }
 	      }
+	    ppc_object->set_tls_marker();
 	  }
 	else if (tls_type == tls::TLSOPT_TO_LE)
 	  {
 	    // no GOT relocs needed for Local Exec.
+	    ppc_object->set_tls_marker();
 	  }
 	else
 	  gold_unreachable();
@@ -9000,7 +9088,9 @@ Target_powerpc<size, big_endian>::Scan::global(
     case elfcpp::R_POWERPC_GOT_TLSLD16_HI:
     case elfcpp::R_POWERPC_GOT_TLSLD16_HA:
       {
-	const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+	tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+	if (!ppc_object->no_tls_marker())
+	  tls_type = target->optimize_tls_ld();
 	if (tls_type == tls::TLSOPT_NONE)
 	  target->tlsld_got_offset(symtab, layout, object);
 	else if (tls_type == tls::TLSOPT_TO_LE)
@@ -9012,6 +9102,7 @@ Target_powerpc<size, big_endian>::Scan::global(
 		gold_assert(os != NULL);
 		os->set_needs_symtab_index();
 	      }
+	    ppc_object->set_tls_marker();
 	  }
 	else
 	  gold_unreachable();
@@ -9044,8 +9135,8 @@ Target_powerpc<size, big_endian>::Scan::global(
     case elfcpp::R_POWERPC_GOT_TPREL16_HI:
     case elfcpp::R_POWERPC_GOT_TPREL16_HA:
       {
-	const bool final = gsym->final_value_is_known();
+	bool final = gsym->final_value_is_known();
-	const tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
+	tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
 	if (tls_type == tls::TLSOPT_NONE)
 	  {
 	    if (!gsym->has_got_offset(GOT_TYPE_TPREL))
@@ -10357,11 +10448,25 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 
   const elfcpp::Rela<size, big_endian> rela(preloc);
   unsigned int r_type = elfcpp::elf_r_type<size>(rela.get_r_info());
+  Powerpc_relobj<size, big_endian>* const object
+    = static_cast<Powerpc_relobj<size, big_endian>*>(relinfo->object);
   switch (this->maybe_skip_tls_get_addr_call(target, r_type, gsym))
     {
     case Track_tls::NOT_EXPECTED:
-      gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
+      if (!parameters->options().shared()
-			     _("__tls_get_addr call lacks marker reloc"));
+	  && parameters->options().tls_optimize())
+	{
+	  // It is a hard error to see a __tls_get_addr call without
+	  // marker relocs after seeing calls with marker relocs in the
+	  // same object file, because dynamic relocation accounting
+	  // will be wrong.
+	  if (object->tls_opt_error())
+	    gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
+				   _("__tls_get_addr call lacks marker reloc"));
+	  else
+	    gold_warning_at_location(relinfo, relnum, rela.get_r_offset(),
+				     _("__tls_get_addr call lacks marker reloc"));
+	}
       break;
     case Track_tls::EXPECTED:
       // We have already complained.
@@ -10394,8 +10499,6 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
   // Offset from start of insn to d-field reloc.
   const int d_offset = big_endian ? 2 : 0;
 
-  Powerpc_relobj<size, big_endian>* const object
-    = static_cast<Powerpc_relobj<size, big_endian>*>(relinfo->object);
   Address value = 0;
   bool has_stub_value = false;
   bool localentry0 = false;
@@ -10646,8 +10749,12 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 	   || r_type == elfcpp::R_PPC64_GOT_TLSGD_PCREL34)
     {
       // First instruction of a global dynamic sequence, arg setup insn.
-      const bool final = gsym == NULL || gsym->final_value_is_known();
+      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
-      const tls::Tls_optimization tls_type = target->optimize_tls_gd(final);
+      if (!object->no_tls_marker())
+	{
+	  bool final = gsym == NULL || gsym->final_value_is_known();
+	  tls_type = target->optimize_tls_gd(final);
+	}
       enum Got_type got_type = GOT_TYPE_STANDARD;
       if (tls_type == tls::TLSOPT_NONE)
 	got_type = GOT_TYPE_TLSGD;
@@ -10752,7 +10859,9 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 	   || r_type == elfcpp::R_PPC64_GOT_TLSLD_PCREL34)
     {
       // First instruction of a local dynamic sequence, arg setup insn.
-      const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+      if (!object->no_tls_marker())
+	tls_type = target->optimize_tls_ld();
       if (tls_type == tls::TLSOPT_NONE)
 	{
 	  value = target->tlsld_got_offset();
@@ -10831,8 +10940,8 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 	   || r_type == elfcpp::R_PPC64_GOT_TPREL_PCREL34)
     {
       // First instruction of initial exec sequence.
-      const bool final = gsym == NULL || gsym->final_value_is_known();
+      bool final = gsym == NULL || gsym->final_value_is_known();
-      const tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
+      tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
       if (tls_type == tls::TLSOPT_NONE)
 	{
 	  if (gsym != NULL)
@@ -10897,8 +11006,12 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
       // Second instruction of a global dynamic sequence,
       // the __tls_get_addr call
       this->expect_tls_get_addr_call(relinfo, relnum, rela.get_r_offset());
-      const bool final = gsym == NULL || gsym->final_value_is_known();
+      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
-      const tls::Tls_optimization tls_type = target->optimize_tls_gd(final);
+      if (!object->no_tls_marker())
+	{
+	  bool final = gsym == NULL || gsym->final_value_is_known();
+	  tls_type = target->optimize_tls_gd(final);
+	}
       if (tls_type != tls::TLSOPT_NONE)
 	{
 	  if (tls_type == tls::TLSOPT_TO_IE)
@@ -10949,7 +11062,9 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
       // Second instruction of a local dynamic sequence,
       // the __tls_get_addr call
       this->expect_tls_get_addr_call(relinfo, relnum, rela.get_r_offset());
-      const tls::Tls_optimization tls_type = target->optimize_tls_ld();
+      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+      if (!object->no_tls_marker())
+	tls_type = target->optimize_tls_ld();
       if (tls_type == tls::TLSOPT_TO_LE)
 	{
 	  bool is_pcrel = false;
@@ -10985,8 +11100,8 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
   else if (r_type == elfcpp::R_POWERPC_TLS)
     {
       // Second instruction of an initial exec sequence
-      const bool final = gsym == NULL || gsym->final_value_is_known();
+      bool final = gsym == NULL || gsym->final_value_is_known();
-      const tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
+      tls::Tls_optimization tls_type = target->optimize_tls_ie(final);
       if (tls_type == tls::TLSOPT_TO_LE)
 	{
 	  Address roff = rela.get_r_offset() & 3;
@@ -12439,8 +12554,13 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 	    {
 	      // First instruction of a global dynamic sequence,
 	      // arg setup insn.
-	      const bool final = gsym == NULL || gsym->final_value_is_known();
+	      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
-	      switch (this->optimize_tls_gd(final))
+	      if (!object->no_tls_marker())
+		{
+		  bool final = gsym == NULL || gsym->final_value_is_known();
+		  tls_type = this->optimize_tls_gd(final);
+		}
+	      switch (tls_type)
 		{
 		case tls::TLSOPT_TO_IE:
 		  r_type += (elfcpp::R_POWERPC_GOT_TPREL16
@@ -12467,7 +12587,10 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 	    {
 	      // First instruction of a local dynamic sequence,
 	      // arg setup insn.
-	      if (this->optimize_tls_ld() == tls::TLSOPT_TO_LE)
+	      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+	      if (!object->no_tls_marker())
+		tls_type = this->optimize_tls_ld();
+	      if (tls_type == tls::TLSOPT_TO_LE)
 		{
 		  if (r_type == elfcpp::R_POWERPC_GOT_TLSLD16
 		      || r_type == elfcpp::R_POWERPC_GOT_TLSLD16_LO)
@@ -12493,7 +12616,7 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 		   || r_type == elfcpp::R_POWERPC_GOT_TPREL16_HA)
 	    {
 	      // First instruction of initial exec sequence.
-	      const bool final = gsym == NULL || gsym->final_value_is_known();
+	      bool final = gsym == NULL || gsym->final_value_is_known();
 	      if (this->optimize_tls_ie(final) == tls::TLSOPT_TO_LE)
 		{
 		  if (r_type == elfcpp::R_POWERPC_GOT_TPREL16
@@ -12511,8 +12634,13 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 	    {
 	      // Second instruction of a global dynamic sequence,
 	      // the __tls_get_addr call
-	      const bool final = gsym == NULL || gsym->final_value_is_known();
+	      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
-	      switch (this->optimize_tls_gd(final))
+	      if (!object->no_tls_marker())
+		{
+		  bool final = gsym == NULL || gsym->final_value_is_known();
+		  tls_type = this->optimize_tls_gd(final);
+		}
+	      switch (tls_type)
 		{
 		case tls::TLSOPT_TO_IE:
 		  r_type = elfcpp::R_POWERPC_NONE;
@@ -12532,7 +12660,10 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 	    {
 	      // Second instruction of a local dynamic sequence,
 	      // the __tls_get_addr call
-	      if (this->optimize_tls_ld() == tls::TLSOPT_TO_LE)
+	      tls::Tls_optimization tls_type = tls::TLSOPT_NONE;
+	      if (!object->no_tls_marker())
+		tls_type = this->optimize_tls_ld();
+	      if (tls_type == tls::TLSOPT_TO_LE)
 		{
 		  const Output_section* os = relinfo->layout->tls_segment()
 		    ->first_section();
@@ -12548,7 +12679,7 @@ Target_powerpc<size, big_endian>::relocate_relocs(
 	  else if (r_type == elfcpp::R_POWERPC_TLS)
 	    {
 	      // Second instruction of an initial exec sequence
-	      const bool final = gsym == NULL || gsym->final_value_is_known();
+	      bool final = gsym == NULL || gsym->final_value_is_known();
 	      if (this->optimize_tls_ie(final) == tls::TLSOPT_TO_LE)
 		{
 		  r_type = elfcpp::R_POWERPC_TPREL16_LO;