[GOLD] Power10 segv due to wild r2

Calling non-pcrel functions from pcrel code requires a stub to set up
r2.  Gold created the stub, but an "optimisation" made the stub jump
to the function local entry, ie. r2 was not initialised.

This patch fixes that long branch stub problem, and another that might
occur for plt call stubs to local functions.

bfd/
	* elf64-ppc.c (write_plt_relocs_for_local_syms): Don't do local
	entry offset optimisation.
gold/
	* powerpc.cc (Powerpc_relobj::do_relocate_sections): Don't do
	local entry offset optimisation for lplt_section.
	(Target_powerpc::Branch_info::make_stub): Don't add local
	entry offset to long branch dest passed to
	add_long_branch_entry.  Do pass st_other bits.
	(Stub_table::Branch_stub_ent): Add "other_" field.
	(Stub_table::add_long_branch_entry): Add "other" param, and
	save.
	(Stub_table::branch_stub_size): Adjust long branch offset.
	(Stub_table::do_write): Likewise.
	(Target_powerpc::Relocate::relocate): Likewise.

2 files changed, 45 insertions, 16 deletions

diff --git a/gold/ChangeLog b/gold/ChangeLog
index 0c00d96..25248a6 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,5 +1,19 @@
 2020-10-09  Alan Modra  <amodra@gmail.com>
 
+	* powerpc.cc (Powerpc_relobj::do_relocate_sections): Don't do
+	local entry offset optimisation for lplt_section.
+	(Target_powerpc::Branch_info::make_stub): Don't add local
+	entry offset to long branch dest passed to
+	add_long_branch_entry.  Do pass st_other bits.
+	(Stub_table::Branch_stub_ent): Add "other_" field.
+	(Stub_table::add_long_branch_entry): Add "other" param, and
+	save.
+	(Stub_table::branch_stub_size): Adjust long branch offset.
+	(Stub_table::do_write): Likewise.
+	(Target_powerpc::Relocate::relocate): Likewise.
+
+2020-10-09  Alan Modra  <amodra@gmail.com>
+
 	* powerpc.cc (is_got_reloc): New function.
 	(Target_powerpc::Relocate::relocate): Use it here, exclude GOT
 	relocs when looking for stubs.
diff --git a/gold/powerpc.cc b/gold/powerpc.cc
index f9eb4f9..476fb4e 100644
--- a/gold/powerpc.cc
+++ b/gold/powerpc.cc
@@ -2767,8 +2767,6 @@ Powerpc_relobj<size, big_endian>::do_relocate_sections(
 	    if (this->local_has_plt_offset(i))
 	      {
 		Address value = this->local_symbol_value(i, 0);
-		if (size == 64)
-		  value += ppc64_local_entry_offset(i);
 		size_t off = this->local_plt_offset(i);
 		elfcpp::Swap<size, big_endian>::writeval(oview + off, value);
 		modified = true;
@@ -3539,6 +3537,7 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
       from += (this->object_->output_section(this->shndx_)->address()
 	       + this->offset_);
       Address to;
+      unsigned int other;
       if (gsym != NULL)
 	{
 	  switch (gsym->source())
@@ -3566,8 +3565,7 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
 	  to = symtab->compute_final_value<size>(gsym, &status);
 	  if (status != Symbol_table::CFVS_OK)
 	    return true;
-	  if (size == 64)
-	    to += this->object_->ppc64_local_entry_offset(gsym);
+	  other = gsym->nonvis() >> 3;
 	}
       else
 	{
@@ -3584,8 +3582,7 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
 	      || !symval.has_output_value())
 	    return true;
 	  to = symval.value(this->object_, 0);
-	  if (size == 64)
-	    to += this->object_->ppc64_local_entry_offset(this->r_sym_);
+	  other = this->object_->st_other(this->r_sym_) >> 5;
 	}
       if (!(size == 32 && this->r_type_ == elfcpp::R_PPC_PLTREL24))
 	to += this->addend_;
@@ -3598,7 +3595,11 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
 					 &to, &dest_shndx))
 	    return true;
 	}
-      Address delta = to - from;
+      unsigned int local_ent = 0;
+      if (size == 64
+	  && this->r_type_ != elfcpp::R_PPC64_REL24_NOTOC)
+	local_ent = elfcpp::ppc64_decode_local_entry(other);
+      Address delta = to + local_ent - from;
       if (delta + max_branch_offset >= 2 * max_branch_offset
 	  || (size == 64
 	      && this->r_type_ == elfcpp::R_PPC64_REL24_NOTOC
@@ -3620,7 +3621,7 @@ Target_powerpc<size, big_endian>::Branch_info::make_stub(
 			   && gsym->output_data() == target->savres_section());
 	  ok = stub_table->add_long_branch_entry(this->object_,
 						 this->r_type_,
-						 from, to, save_res);
+						 from, to, other, save_res);
 	}
     }
   if (!ok)
@@ -4688,7 +4689,7 @@ class Stub_table : public Output_relaxed_input_section
   {
     Branch_stub_ent(unsigned int off, bool notoc, bool save_res)
       : off_(off), iter_(0), notoc_(notoc), toc_(0), save_res_(save_res),
-	tocoff_(0)
+	other_(0), tocoff_(0)
     { }
 
     unsigned int off_;
@@ -4696,6 +4697,7 @@ class Stub_table : public Output_relaxed_input_section
     unsigned int notoc_ : 1;
     unsigned int toc_ : 1;
     unsigned int save_res_ : 1;
+    unsigned int other_ : 3;
     unsigned int tocoff_ : 8;
   };
   typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
@@ -4762,7 +4764,7 @@ class Stub_table : public Output_relaxed_input_section
   // Add a long branch stub.
   bool
   add_long_branch_entry(const Powerpc_relobj<size, big_endian>*,
-			unsigned int, Address, Address, bool);
+			unsigned int, Address, Address, unsigned int, bool);
 
   const Branch_stub_ent*
   find_long_branch_entry(const Powerpc_relobj<size, big_endian>*,
@@ -5282,6 +5284,7 @@ Stub_table<size, big_endian>::add_long_branch_entry(
     unsigned int r_type,
     Address from,
     Address to,
+    unsigned int other,
     bool save_res)
 {
   Branch_stub_key key(object, to);
@@ -5301,6 +5304,8 @@ Stub_table<size, big_endian>::add_long_branch_entry(
 	this->need_resize_ = true;
       p.first->second.toc_ = true;
     }
+  if (p.first->second.other_ == 0)
+    p.first->second.other_ = other;
   gold_assert(save_res == p.first->second.save_res_);
   if (p.second || (this->resizing_ && !p.first->second.iter_))
     {
@@ -6198,6 +6203,7 @@ Stub_table<size, big_endian>::branch_stub_size(
 	}
     }
 
+  off += elfcpp::ppc64_decode_local_entry(p->second.other_);
   if (off + (1 << 25) < 2 << 25)
     return bytes + 4;
   if (!this->targ_->power10_stubs()
@@ -6377,6 +6383,7 @@ Stub_table<size, big_endian>::do_write(Output_file* of)
 		}
 	      if (bs->second.toc_)
 		{
+		  delta += elfcpp::ppc64_decode_local_entry(bs->second.other_);
 		  if (delta + (1 << 25) >= 2 << 25)
 		    {
 		      Address brlt_addr
@@ -6410,6 +6417,8 @@ Stub_table<size, big_endian>::do_write(Output_file* of)
 	    }
 	  else
 	    {
+	      if (!bs->second.notoc_)
+		delta += elfcpp::ppc64_decode_local_entry(bs->second.other_);
 	      if (bs->second.notoc_ || delta + (1 << 25) >= 2 << 25)
 		{
 		  unsigned char* startp = p;
@@ -6640,6 +6649,8 @@ Stub_table<size, big_endian>::do_write(Output_file* of)
 	  p = oview + off;
 	  Address loc = this->stub_address() + off;
 	  Address delta = bs->first.dest_ - loc;
+	  if (!bs->second.notoc_)
+	    delta += elfcpp::ppc64_decode_local_entry(bs->second.other_);
 	  if (bs->second.notoc_)
 	    {
 	      unsigned char* startp = p;
@@ -11039,14 +11050,15 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 		|| r_type == elfcpp::R_POWERPC_PLT16_HA)))
 	addend = rela.get_r_addend();
       value = psymval->value(object, addend);
+      unsigned int local_ent = 0;
       if (size == 64 && is_branch_reloc<size>(r_type))
 	{
 	  if (target->abiversion() >= 2)
 	    {
 	      if (gsym != NULL)
-		value += object->ppc64_local_entry_offset(gsym);
+		local_ent = object->ppc64_local_entry_offset(gsym);
 	      else
-		value += object->ppc64_local_entry_offset(r_sym);
+		local_ent = object->ppc64_local_entry_offset(r_sym);
 	    }
 	  else
 	    {
@@ -11055,9 +11067,9 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 					&value, &dest_shndx);
 	    }
 	}
-      Address max_branch_offset = max_branch_delta<size>(r_type);
-      if (max_branch_offset != 0
-	  && (value - address + max_branch_offset >= 2 * max_branch_offset
+      Address max_branch = max_branch_delta<size>(r_type);
+      if (max_branch != 0
+	  && (value + local_ent - address + max_branch >= 2 * max_branch
 	      || (size == 64
 		  && r_type == elfcpp::R_PPC64_REL24_NOTOC
 		  && (gsym != NULL
@@ -11082,12 +11094,15 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
 			       + ent->off_);
 		      if (size == 64
 			  && r_type != elfcpp::R_PPC64_REL24_NOTOC)
-			value += ent->tocoff_;
+			value += (elfcpp::ppc64_decode_local_entry(ent->other_)
+				  + ent->tocoff_);
 		    }
 		  has_stub_value = true;
 		}
 	    }
 	}
+      if (!has_stub_value)
+	value += local_ent;
     }
 
   switch (r_type)