Ensures that GDB prints stacktraces correctly for x64 builds when debugging t...

src/gdb-jit.cc

Index: src/gdb-jit.cc
===================================================================
--- src/gdb-jit.cc	(revision 6529)
+++ src/gdb-jit.cc	(working copy)
@@ -201,6 +201,7 @@
     TYPE_SHLIB = 10,
     TYPE_DYNSYM = 11,
     TYPE_LOPROC = 0x70000000,
+    TYPE_X86_64_UNWIND = 0x70000001,
     TYPE_HIPROC = 0x7fffffff,
     TYPE_LOUSER = 0x80000000,
     TYPE_HIUSER = 0xffffffff
@@ -639,11 +640,26 @@
 
 class CodeDescription BASE_EMBEDDED {
  public:
+
+#ifdef V8_TARGET_ARCH_X64
+  enum OffsetType {
+    POST_RBP_PUSH,
+    POST_RBP_SET,
+    POST_RBP_POP,
+    OFFSET_TYPE_MAX
+  };
+#endif
+
   CodeDescription(const char* name,
                   Code* code,
                   Handle<Script> script,
-                  GDBJITLineInfo* lineinfo)
-      : name_(name), code_(code), script_(script), lineinfo_(lineinfo)
+                  GDBJITLineInfo* lineinfo,
+                  GDBJITInterface::CodeTag tag)
+      : name_(name),
+      code_(code),
+      script_(script),
+      lineinfo_(lineinfo),
+      tag_(tag)
   { }
 
   const char* code_name() const {
@@ -654,6 +670,10 @@
     return code_->instruction_end() - code_->instruction_start();
   }
 
+  uintptr_t code_end() const {
+    return (uintptr_t)code_->instruction_end();
+  }
+
   uintptr_t code_start() const {
     return (uintptr_t)code_->instruction_start();
   }
@@ -666,6 +686,18 @@
         lineinfo_ != NULL;
   }
 
+#ifdef V8_TARGET_ARCH_X64
+  uintptr_t get_location(OffsetType ofs) const {
+    ASSERT(ofs < OFFSET_TYPE_MAX);
+    return offsets_[ofs];
+  }
+
+  void set_location(OffsetType ofs, uintptr_t value) {
+    ASSERT(ofs < OFFSET_TYPE_MAX);
+    offsets_[ofs] = value;
+  }
+#endif
+
   GDBJITLineInfo* lineinfo() const { return lineinfo_; }
 
   SmartPointer<char> filename() {
@@ -676,11 +708,19 @@
     return GetScriptLineNumberSafe(script_, pos) + 1;
   }
 
+  GDBJITInterface::CodeTag get_tag() const {

[Vyacheslav Egorov (Chromium), 2011/02/01 21:00:25]

Getters don't have get_ prefix in Google C++ Code Style.

+    return tag_;
+  }
+
  private:
   const char* name_;
   Code* code_;
   Handle<Script> script_;
   GDBJITLineInfo* lineinfo_;
+  GDBJITInterface::CodeTag tag_;
+#ifdef V8_TARGET_ARCH_X64
+  uintptr_t offsets_[OFFSET_TYPE_MAX];
+#endif
 };
 
 
@@ -900,12 +940,232 @@
 };
 
 
+#ifdef V8_TARGET_ARCH_X64
+
+
+class UnwindInfoSection : public ELFSection {
+ public:
+  explicit UnwindInfoSection(CodeDescription *desc);
+  virtual bool WriteBody(Writer *w);
+
+  int WriteCIE(Writer *w);
+  void WriteFDE(Writer *w, int);
+
+  void WriteFDEStateOne(Writer *w);
+  void WriteFDEStateTwo(Writer *w);
+  void WriteFDEStateThree(Writer *w);
+  void WriteFDEStateFour(Writer *w);
+
+  void WriteLength(Writer *w, Writer::Slot<uint32_t> &, int);
+
+ private:
+  CodeDescription *desc_;
+
+  // DWARF3 Specification, Table 7.23
+  enum CFIInstructions {
+    DW_CFA_ADVANCE_LOC = 0X40,
+    DW_CFA_OFFSET = 0X80,
+    DW_CFA_RESTORE = 0XC0,
+    DW_CFA_NOP = 0X00,
+    DW_CFA_SET_LOC = 0X01,
+    DW_CFA_ADVANCE_LOC1 = 0X02,
+    DW_CFA_ADVANCE_LOC2 = 0X03,
+    DW_CFA_ADVANCE_LOC4 = 0X04,
+    DW_CFA_OFFSET_EXTENDED = 0X05,
+    DW_CFA_RESTORE_EXTENDED = 0X06,
+    DW_CFA_UNDEFINED = 0X07,
+    DW_CFA_SAME_VALUE = 0X08,
+    DW_CFA_REGISTER = 0X09,
+    DW_CFA_REMEMBER_STATE = 0X0A,
+    DW_CFA_RESTORE_STATE = 0X0B,
+    DW_CFA_DEF_CFA = 0X0C,
+    DW_CFA_DEF_CFA_REGISTER = 0X0D,
+    DW_CFA_DEF_CFA_OFFSET = 0X0E,
+
+    DW_CFA_DEF_CFA_EXPRESSION = 0X0F,
+    DW_CFA_EXPRESSION = 0X10,
+    DW_CFA_OFFSET_EXTENDED_SF = 0X11,
+    DW_CFA_DEF_CFA_SF = 0X12,
+    DW_CFA_DEF_CFA_OFFSET_SF = 0X13,
+    DW_CFA_VAL_OFFSET = 0X14,
+    DW_CFA_VAL_OFFSET_SF = 0X15,
+    DW_CFA_VAL_EXPRESSION = 0X16
+  };
+
+  // System V ABI, AMD64 Supplement, Version 0.99.5, Figure 3.36
+  enum RegisterMapping {
+    // Only the relevant ones have been added to reduce clutter.
+    AMD64_RBP = 6,
+    AMD64_RSP = 7,
+    AMD64_RA = 16
+  };
+
+  enum CFIConstants {
+    CIE_ID = 0,
+    CIE_VERSION = 1,
+    CODE_ALIGN_FACTOR = 1,
+    DATA_ALIGN_FACTOR = 1,
+    RETURN_ADDRESS_REGISTER = AMD64_RA
+  };
+};
+
+
+void UnwindInfoSection::WriteLength(Writer *w,
+                                    Writer::Slot<uint32_t> &length_slot,
+                                    int initial_position) {
+  uint32_t align = (w->position() - initial_position) % kPointerSize;
+
+  if (align != 0) {
+    for (uint32_t i = 0; i < (kPointerSize - align); i++)
+      w->Write<uint8_t>(DW_CFA_NOP);
+  }
+
+  ASSERT((w->position() - initial_position) % kPointerSize == 0);
+  length_slot.set(w->position() - initial_position);
+}
+
+
+UnwindInfoSection::UnwindInfoSection(CodeDescription *desc)
+    : ELFSection(".eh_frame", TYPE_X86_64_UNWIND, 1), desc_(desc)
+{ }
+
+int UnwindInfoSection::WriteCIE(Writer *w) {
+  Writer::Slot<uint32_t> cie_length_slot = w->CreateSlotHere<uint32_t>();
+  uint32_t cie_position = w->position();
+
+  // Write out the CIE header. Currently no 'common instructions' are
+  // emitted onto the CIE; every FDE has its own set of instructions.
+
+  w->Write<uint32_t>(CIE_ID);
+  w->Write<uint8_t>(CIE_VERSION);
+  w->Write<uint8_t>(0);  // Null augmentation string.
+  w->WriteSLEB128(CODE_ALIGN_FACTOR);
+  w->WriteSLEB128(DATA_ALIGN_FACTOR);
+  w->Write<uint8_t>(RETURN_ADDRESS_REGISTER);
+
+  WriteLength(w, cie_length_slot, cie_position);
+
+  return cie_position;
+}
+
+
+void UnwindInfoSection::WriteFDE(Writer *w, int cie_position) {
+  // The only FDE for this function. The CFA is the current RBP.
+  Writer::Slot<uint32_t> fde_length_slot = w->CreateSlotHere<uint32_t>();
+  int fde_position = w->position();
+  w->Write<int32_t>(fde_position - cie_position + 4);
+
+  w->Write<uintptr_t>(desc_->code_start());
+  w->Write<uintptr_t>(desc_->code_size());
+
+  WriteFDEStateOne(w);

[Vyacheslav Egorov (Chromium), 2011/02/01 21:00:25]

This names are not informative. 

+  WriteFDEStateTwo(w);
+  WriteFDEStateThree(w);
+  WriteFDEStateFour(w);
+
+  WriteLength(w, fde_length_slot, fde_position);
+}
+
+
+void UnwindInfoSection::WriteFDEStateOne(Writer *w) {
+  // The first state, just after the control has been transferred to the the
+  // function.
+
+  // RBP for this function will be the value of RSP after pushing the RBP
+  // for the previous function. The previous RBP has not been pushed yet.
+  w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
+  w->WriteULEB128(AMD64_RSP);
+  w->WriteSLEB128(-kPointerSize);
+
+  // The RA is stored at location CFA + kCallerPCOffset. This is an invariant,
+  // and hence omitted from the next states.
+  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
+  w->WriteULEB128(AMD64_RA);
+  w->WriteSLEB128(StandardFrameConstants::kCallerPCOffset);
+
+  // The RBP of the previous function is still in RBP.
+  w->Write<uint8_t>(DW_CFA_SAME_VALUE);
+  w->WriteULEB128(AMD64_RBP);
+
+  // Last location described by this entry.
+  w->Write<uint8_t>(DW_CFA_SET_LOC);
+  w->Write<uint64_t>(desc_->get_location(CodeDescription::POST_RBP_PUSH));
+}
+
+
+void UnwindInfoSection::WriteFDEStateTwo(Writer *w) {
+  // The second state, just after RBP has been pushed.
+
+  // RBP / CFA for this function is now the current RSP, so just set the
+  // offset from the previous rule (from -8) to 0.
+  w->Write<uint8_t>(DW_CFA_DEF_CFA_OFFSET);
+  w->WriteULEB128(0);
+
+  // The previous RBP is stored at CFA + kCallerFPOffset. This is an invariant
+  // in this and the next state, and hence omitted in the next state.
+  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
+  w->WriteULEB128(AMD64_RBP);
+  w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);
+
+  // Last location described by this entry.
+  w->Write<uint8_t>(DW_CFA_SET_LOC);
+  w->Write<uint64_t>(desc_->get_location(CodeDescription::POST_RBP_SET));
+}
+
+
+void UnwindInfoSection::WriteFDEStateThree(Writer *w) {
+  // The third state, after the RBP has been set.
+
+  // The CFA can now directly be set to RBP.
+  w->Write<uint8_t>(DW_CFA_DEF_CFA);
+  w->WriteULEB128(AMD64_RBP);
+  w->WriteULEB128(0);
+
+  // Last location described by this entry.
+  w->Write<uint8_t>(DW_CFA_SET_LOC);
+  w->Write<uint64_t>(desc_->get_location(CodeDescription::POST_RBP_POP));
+}
+
+
+void UnwindInfoSection::WriteFDEStateFour(Writer *w) {
+  // The fourth (final) state. The RBP has been popped (just before issuing a
+  // return).
+
+  // The CFA can is now calculated in the same way as in the first state.
+  w->Write<uint8_t>(DW_CFA_DEF_CFA_SF);
+  w->WriteULEB128(AMD64_RSP);
+  w->WriteSLEB128(-kPointerSize);
+
+  // The RBP
+  w->Write<uint8_t>(DW_CFA_OFFSET_EXTENDED);
+  w->WriteULEB128(AMD64_RBP);
+  w->WriteSLEB128(StandardFrameConstants::kCallerFPOffset);
+
+  // Last location described by this entry.
+  w->Write<uint8_t>(DW_CFA_SET_LOC);
+  w->Write<uint64_t>(desc_->code_end());
+}
+
+
+bool UnwindInfoSection::WriteBody(Writer *w) {
+  uint32_t cie_position = WriteCIE(w);
+  WriteFDE(w, cie_position);
+  return true;
+}
+
+
+#endif  // V8_TARGET_ARCH_X64
+
+
 static void CreateDWARFSections(CodeDescription* desc, ELF* elf) {
   if (desc->is_line_info_available()) {
     elf->AddSection(new DebugInfoSection(desc));
     elf->AddSection(new DebugAbbrevSection);
     elf->AddSection(new DebugLineSection(desc));
   }
+#ifdef V8_TARGET_ARCH_X64
+  elf->AddSection(new UnwindInfoSection(desc));
+#endif
 }
 
 
@@ -1065,15 +1325,47 @@
 
   if (!name.is_null()) {
     SmartPointer<char> name_cstring = name->ToCString(DISALLOW_NULLS);
-    AddCode(*name_cstring, *code, *script);
+    AddCode(*name_cstring, *code, GDBJITInterface::FUNCTION, *script);
   } else {
-    AddCode("", *code, *script);
+    AddCode("", *code, GDBJITInterface::FUNCTION, *script);
   }
 }
 
+static const int kFramePointerPushOffset = 1;
+static const int kFramePointerSetOffset = 4;
+static const int kFramePointerPopOffset = -3;
 
+static void AddUnwindInfo(CodeDescription *cd) {
+#ifdef V8_TARGET_ARCH_X64
+  if (cd->get_tag() == GDBJITInterface::FUNCTION) {
+

[Vyacheslav Egorov (Chromium), 2011/02/01 21:00:25]

This does not lint (did you run tools/presubmit.py?)

+    {
+      // Sanity check
+      byte *code = reinterpret_cast<byte*>(cd->code_start());

[Vyacheslav Egorov (Chromium), 2011/02/01 21:00:25]

This will fail to compile in release mode (due to unused variable).

+      ASSERT(code[kFramePointerSetOffset] == 0x56);
+      ASSERT(code[kFramePointerSetOffset + 1] == 0x57);
+      ASSERT(code[kFramePointerPushOffset] == 0x48);
+      ASSERT(code[kFramePointerPopOffset] == 0xBE);
+    }
+
+    cd->set_location(CodeDescription::POST_RBP_PUSH,
+                     cd->code_start() + kFramePointerPushOffset);
+    cd->set_location(CodeDescription::POST_RBP_SET,
+                     cd->code_start() + kFramePointerSetOffset);
+    cd->set_location(CodeDescription::POST_RBP_POP,
+                     cd->code_end() + kFramePointerPopOffset);
+  } else {
+    cd->set_location(CodeDescription::POST_RBP_PUSH, cd->code_start());
+    cd->set_location(CodeDescription::POST_RBP_SET, cd->code_start());
+    cd->set_location(CodeDescription::POST_RBP_POP, cd->code_end());
+  }
+#endif  // V8_TARGET_ARCH_X64
+}
+
+
 void GDBJITInterface::AddCode(const char* name,
                               Code* code,
+                              GDBJITInterface::CodeTag tag,
                               Script* script) {
   if (!FLAG_gdbjit) return;
   AssertNoAllocation no_gc;
@@ -1086,7 +1378,8 @@
                             code,
                             script != NULL ? Handle<Script>(script)
                                            : Handle<Script>(),
-                            lineinfo);
+                            lineinfo,
+                            tag);
 
   if (!FLAG_gdbjit_full && !code_desc.is_line_info_available()) {
     delete lineinfo;
@@ -1094,6 +1387,7 @@
     return;
   }
 
+  AddUnwindInfo(&code_desc);
   JITCodeEntry* entry = CreateELFObject(&code_desc);
   ASSERT(!IsLineInfoTagged(entry));
 
@@ -1120,7 +1414,7 @@
     builder.AddFormatted(": code object %p", static_cast<void*>(code));
   }
 
-  AddCode(builder.Finalize(), code);
+  AddCode(builder.Finalize(), code, tag);
 }