From Craig Silverstein: set symbol value for function pointer

equality across shared library boundaries.

diff --git a/gold/x86_64.cc b/gold/x86_64.cc
index d7a6ea9..df76051 100644 (file)
--- a/gold/x86_64.cc
+++ b/gold/x86_64.cc
@@ -86,6 +86,11 @@ class Target_x86_64 : public Sized_target<64, false>
   void
   do_finalize_sections(Layout*);
 
+  // Return the value to use for a dynamic which requires special
+  // treatment.
+  uint64_t
+  do_dynsym_value(const Symbol*) const;
+
   // Relocate a section.
   void
   relocate_section(const Relocate_info<64, false>*,
@@ -849,7 +854,19 @@ Target_x86_64::Scan::global(const General_options& options,
          // function, we make a PLT entry.  Otherwise we need to
          // either generate a COPY reloc or copy this reloc.
          if (gsym->type() == elfcpp::STT_FUNC)
-           target->make_plt_entry(symtab, layout, gsym);
+           {
+             target->make_plt_entry(symtab, layout, gsym);
+
+             // If this is not a PC relative reference, then we may
+             // be taking the address of the function.  In that case
+             // we need to set the entry in the dynamic symbol table
+             // to the address of the PLT entry.
+             if (r_type != elfcpp::R_X86_64_PC64
+                 && r_type != elfcpp::R_X86_64_PC32
+                 && r_type != elfcpp::R_X86_64_PC16
+                 && r_type != elfcpp::R_X86_64_PC8)
+               gsym->set_needs_dynsym_value();
+           }
          else
            target->copy_reloc(&options, symtab, layout, object, data_shndx,
                               gsym, reloc);
@@ -1608,6 +1625,18 @@ Target_x86_64::relocate_section(const Relocate_info<64, false>* relinfo,
     view_size);
 }
 
+// Return the value to use for a dynamic which requires special
+// treatment.  This is how we support equality comparisons of function
+// pointers across shared library boundaries, as described in the
+// processor specific ABI supplement.
+
+uint64_t
+Target_x86_64::do_dynsym_value(const Symbol* gsym) const
+{
+  gold_assert(gsym->is_from_dynobj() && gsym->has_plt_offset());
+  return this->plt_section()->address() + gsym->plt_offset();
+}
+
 // Return a string used to fill a code section with nops to take up
 // the specified length.