Gold: Patch linker to implement --long-plt flag.

third_party/binutils/long-plt.patch

Index: third_party/binutils/long-plt.patch
diff --git a/third_party/binutils/long-plt.patch b/third_party/binutils/long-plt.patch
new file mode 100644
index 0000000000000000000000000000000000000000..9132377efcff82efa9e8a6d4304ae3c23da176e3
--- /dev/null
+++ b/third_party/binutils/long-plt.patch
@@ -0,0 +1,232 @@
+commit ee8713f5cfc38be0e92d78f2afbc77d701ef189d
+Author: Peter Collingbourne <pcc@google.com>
+Date:   Thu Dec 17 16:50:35 2015 -0800
+
+    Implement --long-plt flag (ARM only).
+    
+    gold/
+        PR gold/18780
+        * arm.cc (Target_arm::do_make_data_plt): Choose PLT generator based
+        on value of --long-plt flag.
+        (Output_data_plt_arm_standard::do_get_plt_entry_size): Moved to
+        Output_data_plt_arm_short.
+        (Output_data_plt_arm_standard::do_fill_plt_entry): Likewise.
+        (Output_data_plt_arm_standard::plt_entry): Likewise.
+        (Output_data_plt_arm_standard::do_fill_first_plt_entry): Fix
+        variable reference.
+        (Output_data_plt_arm_short): New class.
+        (Output_data_plt_arm_short::do_fill_plt_entry): Error out on too large
+        PLT offsets instead of asserting.
+        (Output_data_plt_arm_long): New class.
+        * options.h (General_options): Define --long-plt flag.
+
+diff --git a/gold/arm.cc b/gold/arm.cc
+index 6c472bb..a10d785 100644
+--- a/gold/arm.cc
++++ b/gold/arm.cc
+@@ -62,7 +62,10 @@ template<bool big_endian>
+ class Output_data_plt_arm;
+ 
+ template<bool big_endian>
+-class Output_data_plt_arm_standard;
++class Output_data_plt_arm_short;
++
++template<bool big_endian>
++class Output_data_plt_arm_long;
+ 
+ template<bool big_endian>
+ class Stub_table;
+@@ -2532,7 +2535,12 @@ class Target_arm : public Sized_target<32, big_endian>
+   virtual Output_data_plt_arm<big_endian>*
+   do_make_data_plt(Layout* layout, Output_data_space* got_plt)
+   {
+-    return new Output_data_plt_arm_standard<big_endian>(layout, got_plt);
++    if (parameters->options().long_plt())
++      return new Output_data_plt_arm_long<big_endian>(
++	layout, got_plt);
++    else
++      return new Output_data_plt_arm_short<big_endian>(
++	layout, got_plt);
+   }
+ 
+  private:
+@@ -7382,29 +7390,14 @@ class Output_data_plt_arm_standard : public Output_data_plt_arm<big_endian>
+   do_first_plt_entry_offset() const
+   { return sizeof(first_plt_entry); }
+ 
+-  // Return the size of a PLT entry.
+-  virtual unsigned int
+-  do_get_plt_entry_size() const
+-  { return sizeof(plt_entry); }
+-
+   virtual void
+   do_fill_first_plt_entry(unsigned char* pov,
+ 			  Arm_address got_address,
+ 			  Arm_address plt_address);
+ 
+-  virtual void
+-  do_fill_plt_entry(unsigned char* pov,
+-		    Arm_address got_address,
+-		    Arm_address plt_address,
+-		    unsigned int got_offset,
+-		    unsigned int plt_offset);
+-
+  private:
+   // Template for the first PLT entry.
+   static const uint32_t first_plt_entry[5];
+-
+-  // Template for subsequent PLT entries.
+-  static const uint32_t plt_entry[3];
+ };
+ 
+ // ARM PLTs.
+@@ -7432,7 +7425,7 @@ Output_data_plt_arm_standard<big_endian>::do_fill_first_plt_entry(
+ {
+   // Write first PLT entry.  All but the last word are constants.
+   const size_t num_first_plt_words = (sizeof(first_plt_entry)
+-				      / sizeof(plt_entry[0]));
++				      / sizeof(first_plt_entry[0]));
+   for (size_t i = 0; i < num_first_plt_words - 1; i++)
+     elfcpp::Swap<32, big_endian>::writeval(pov + i * 4, first_plt_entry[i]);
+   // Last word in first PLT entry is &GOT[0] - .
+@@ -7441,9 +7434,37 @@ Output_data_plt_arm_standard<big_endian>::do_fill_first_plt_entry(
+ }
+ 
+ // Subsequent entries in the PLT.
++// This class generates short (12-byte) entries, for displacements up to 2^28.
++
++template<bool big_endian>
++class Output_data_plt_arm_short : public Output_data_plt_arm_standard<big_endian>
++{
++ public:
++  Output_data_plt_arm_short(Layout* layout,
++			    Output_data_space* got_plt)
++    : Output_data_plt_arm_standard<big_endian>(layout, got_plt)
++  { }
++
++ protected:
++  // Return the size of a PLT entry.
++  virtual unsigned int
++  do_get_plt_entry_size() const
++  { return sizeof(plt_entry); }
++
++  virtual void
++  do_fill_plt_entry(unsigned char* pov,
++		    Arm_address got_address,
++		    Arm_address plt_address,
++		    unsigned int got_offset,
++		    unsigned int plt_offset);
++
++ private:
++  // Template for subsequent PLT entries.
++  static const uint32_t plt_entry[3];
++};
+ 
+ template<bool big_endian>
+-const uint32_t Output_data_plt_arm_standard<big_endian>::plt_entry[3] =
++const uint32_t Output_data_plt_arm_short<big_endian>::plt_entry[3] =
+ {
+   0xe28fc600,	// add   ip, pc, #0xNN00000
+   0xe28cca00,	// add   ip, ip, #0xNN000
+@@ -7452,7 +7473,7 @@ const uint32_t Output_data_plt_arm_standard<big_endian>::plt_entry[3] =
+ 
+ template<bool big_endian>
+ void
+-Output_data_plt_arm_standard<big_endian>::do_fill_plt_entry(
++Output_data_plt_arm_short<big_endian>::do_fill_plt_entry(
+     unsigned char* pov,
+     Arm_address got_address,
+     Arm_address plt_address,
+@@ -7461,8 +7482,9 @@ Output_data_plt_arm_standard<big_endian>::do_fill_plt_entry(
+ {
+   int32_t offset = ((got_address + got_offset)
+ 		    - (plt_address + plt_offset + 8));
++  if (offset < 0 || offset > 0x0fffffff)
++    gold_error(_("PLT offset too large, try linking with --long-plt"));
+ 
+-  gold_assert(offset >= 0 && offset < 0x0fffffff);
+   uint32_t plt_insn0 = plt_entry[0] | ((offset >> 20) & 0xff);
+   elfcpp::Swap<32, big_endian>::writeval(pov, plt_insn0);
+   uint32_t plt_insn1 = plt_entry[1] | ((offset >> 12) & 0xff);
+@@ -7471,6 +7493,66 @@ Output_data_plt_arm_standard<big_endian>::do_fill_plt_entry(
+   elfcpp::Swap<32, big_endian>::writeval(pov + 8, plt_insn2);
+ }
+ 
++// This class generates long (16-byte) entries, for arbitrary displacements.
++
++template<bool big_endian>
++class Output_data_plt_arm_long : public Output_data_plt_arm_standard<big_endian>
++{
++ public:
++  Output_data_plt_arm_long(Layout* layout,
++			   Output_data_space* got_plt)
++    : Output_data_plt_arm_standard<big_endian>(layout, got_plt)
++  { }
++
++ protected:
++  // Return the size of a PLT entry.
++  virtual unsigned int
++  do_get_plt_entry_size() const
++  { return sizeof(plt_entry); }
++
++  virtual void
++  do_fill_plt_entry(unsigned char* pov,
++		    Arm_address got_address,
++		    Arm_address plt_address,
++		    unsigned int got_offset,
++		    unsigned int plt_offset);
++
++ private:
++  // Template for subsequent PLT entries.
++  static const uint32_t plt_entry[4];
++};
++
++template<bool big_endian>
++const uint32_t Output_data_plt_arm_long<big_endian>::plt_entry[4] =
++{
++  0xe28fc200,	// add   ip, pc, #0xN0000000
++  0xe28cc600,	// add   ip, ip, #0xNN00000
++  0xe28cca00,	// add   ip, ip, #0xNN000
++  0xe5bcf000,	// ldr   pc, [ip, #0xNNN]!
++};
++
++template<bool big_endian>
++void
++Output_data_plt_arm_long<big_endian>::do_fill_plt_entry(
++    unsigned char* pov,
++    Arm_address got_address,
++    Arm_address plt_address,
++    unsigned int got_offset,
++    unsigned int plt_offset)
++{
++  int32_t offset = ((got_address + got_offset)
++		    - (plt_address + plt_offset + 8));
++
++  uint32_t plt_insn0 = plt_entry[0] | (offset >> 28);
++  elfcpp::Swap<32, big_endian>::writeval(pov, plt_insn0);
++  uint32_t plt_insn1 = plt_entry[1] | ((offset >> 20) & 0xff);
++  elfcpp::Swap<32, big_endian>::writeval(pov + 4, plt_insn1);
++  uint32_t plt_insn2 = plt_entry[2] | ((offset >> 12) & 0xff);
++  elfcpp::Swap<32, big_endian>::writeval(pov + 8, plt_insn2);
++  uint32_t plt_insn3 = plt_entry[3] | (offset & 0xfff);
++  elfcpp::Swap<32, big_endian>::writeval(pov + 12, plt_insn3);
++}
++
+ // Write out the PLT.  This uses the hand-coded instructions above,
+ // and adjusts them as needed.  This is all specified by the arm ELF
+ // Processor Supplement.
+diff --git a/gold/options.h b/gold/options.h
+index cf3b705..5bd93b1e 100644
+--- a/gold/options.h
++++ b/gold/options.h
+@@ -826,6 +826,10 @@ class General_options
+ 		    "veneer"),
+ 		 NULL);
+ 
++  DEFINE_bool(long_plt, options::TWO_DASHES, '\0', false,
++	      N_("(ARM only) Generate long PLT entries"),
++	      N_("(ARM only) Do not generate long PLT entries"));
++
+   DEFINE_bool(g, options::EXACTLY_ONE_DASH, '\0', false,
+ 	      N_("Ignored"), NULL);
+