Implement code patcher for x64.

Use the code patcher for the patching of the JS return sequence used by the debugger.

Added explicit instruction cache flushing in a code patching section which did not have it for completeness, even though it is not required on Intel processors.
Review URL: http://codereview.chromium.org/203016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2870 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/assembler-ia32.cc

@@ -157,6 +157,9 @@ void RelocInfo::PatchCode(byte* instructions, int instruction_count) {
   for (int i = 0; i < instruction_count; i++) {
     *(pc_ + i) = *(instructions + i);
   }
+
+  // Indicate that code has changed.
+  CPU::FlushICache(pc_, instruction_count);
 }
 
 
@@ -164,12 +167,24 @@ void RelocInfo::PatchCode(byte* instructions, int instruction_count) {
 // Additional guard int3 instructions can be added if required.
 void RelocInfo::PatchCodeWithCall(Address target, int guard_bytes) {
   // Call instruction takes up 5 bytes and int3 takes up one byte.
-  int code_size = 5 + guard_bytes;
+  static const int kCallCodeSize = 5;
+  int code_size = kCallCodeSize + guard_bytes;
+
+  // Create a code patcher.
+  CodePatcher patcher(pc_, code_size);
+
+  // Add a label for checking the size of the code used for returning.
+#ifdef DEBUG
+  Label check_codesize;
+  patcher.masm()->bind(&check_codesize);
+#endif
 
   // Patch the code.
-  CodePatcher patcher(pc_, code_size);
   patcher.masm()->call(target, RelocInfo::NONE);
 
+  // Check that the size of the code generated is as expected.
+  ASSERT_EQ(kCallCodeSize, patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
+
   // Add the requested number of int3 instructions after the call.
   for (int i = 0; i < guard_bytes; i++) {
     patcher.masm()->int3();

src/x64/assembler-x64.cc

@@ -173,22 +173,32 @@ void CpuFeatures::Probe()  {
 // Patch the code at the current PC with a call to the target address.
 // Additional guard int3 instructions can be added if required.
 void RelocInfo::PatchCodeWithCall(Address target, int guard_bytes) {
-  // Call instruction takes up 13 bytes and int3 takes up one byte.
-  static const int kCallInstructionSize = 13;
-  Address patch_site = pc_;
-  Memory::uint16_at(patch_site) = 0xBA49u;  // movq r10, imm64
-  // Write "0x00, call r10" starting at last byte of address.  We overwrite
-  // the 0x00 later, and this lets us write a uint32.
-  Memory::uint32_at(patch_site + 9) = 0xD2FF4900u;  // 0x00, call r10
-  Memory::Address_at(patch_site + 2) = target;
+  // Load register with immediate 64 and call through a register instructions
+  // takes up 13 bytes and int3 takes up one byte.
+  static const int kCallCodeSize = 13;
+  int code_size = kCallCodeSize + guard_bytes;
+
+  // Create a code patcher.
+  CodePatcher patcher(pc_, code_size);
+
+  // Add a label for checking the size of the code used for returning.
+#ifdef DEBUG
+  Label check_codesize;
+  patcher.masm()->bind(&check_codesize);
+#endif
+
+  // Patch the code.
+  patcher.masm()->movq(r10, target, RelocInfo::NONE);
+  patcher.masm()->call(r10);
+
+  // Check that the size of the code generated is as expected.
+  ASSERT_EQ(kCallCodeSize,
+            patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
 
   // Add the requested number of int3 instructions after the call.
   for (int i = 0; i < guard_bytes; i++) {
-    *(patch_site + kCallInstructionSize + i) = 0xCC;  // int3
+    patcher.masm()->int3();
   }
-
-  // Indicate that code has changed.
-  CPU::FlushICache(patch_site, kCallInstructionSize + guard_bytes);
 }
 
 
@@ -197,6 +207,9 @@ void RelocInfo::PatchCode(byte* instructions, int instruction_count) {
   for (int i = 0; i < instruction_count; i++) {
     *(pc_ + i) = *(instructions + i);
   }
+
+  // Indicate that code has changed.
+  CPU::FlushICache(pc_, instruction_count);
 }
 
 // -----------------------------------------------------------------------------

src/x64/macro-assembler-x64.cc

@@ -2087,4 +2087,25 @@ void MacroAssembler::UndoAllocationInNewSpace(Register object) {
 }
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
+CodePatcher::CodePatcher(byte* address, int size)
+    : address_(address), size_(size), masm_(address, size + Assembler::kGap) {
+  // Create a new macro assembler pointing to the address of the code to patch.
+  // The size is adjusted with kGap on order for the assembler to generate size
+  // bytes of instructions without failing with buffer size constraints.
+  ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
+}
+
+
+CodePatcher::~CodePatcher() {
+  // Indicate that code has changed.
+  CPU::FlushICache(address_, size_);
+
+  // Check that the code was patched as expected.
+  ASSERT(masm_.pc_ == address_ + size_);
+  ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
+}
+#endif  // ENABLE_DEBUGGER_SUPPORT
+
+
 } }  // namespace v8::internal

src/x64/macro-assembler-x64.h

@@ -589,6 +589,28 @@ class MacroAssembler: public Assembler {
 };
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
+// The code patcher is used to patch (typically) small parts of code e.g. for
+// debugging and other types of instrumentation. When using the code patcher
+// the exact number of bytes specified must be emitted. Is not legal to emit
+// relocation information. If any of these constraints are violated it causes
+// an assertion.
+class CodePatcher {
+ public:
+  CodePatcher(byte* address, int size);
+  virtual ~CodePatcher();
+
+  // Macro assembler to emit code.
+  MacroAssembler* masm() { return &masm_; }
+
+ private:
+  byte* address_;  // The address of the code being patched.
+  int size_;  // Number of bytes of the expected patch size.
+  MacroAssembler masm_;  // Macro assembler used to generate the code.
+};
+#endif  // ENABLE_DEBUGGER_SUPPORT
+
+
 // -----------------------------------------------------------------------------
 // Static helper functions.