Drops into Simulator Debugger only in a session that is already interactive.

runtime/vm/simulator_mips.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_MIPS)
 
 // Only build the simulator if not compiling for real MIPS hardware.
 #if !defined(HOST_ARCH_MIPS)
 
@@ skipping 15 matching lines @@
 #define SScanF sscanf  // NOLINT
 
 
 // The SimulatorDebugger class is used by the simulator while debugging
 // simulated MIPS code.
 class SimulatorDebugger {
  public:
   explicit SimulatorDebugger(Simulator* sim);
   ~SimulatorDebugger();
 
+  // Enter interactive debugging, and attach to the simulator.
+  void Attach(Instr* instr, const char *message);
+
+  // Enter interactive debugging if debugging is already attached to
+  // the simulator, and otherwise return immediately.
   void Stop(Instr* instr, const char* message);
   void Debug();
   char* ReadLine(const char* prompt);
 
  private:
   Simulator* sim_;
 
   bool GetValue(char* desc, uint32_t* value);
   bool GetFValue(char* desc, double* value);
 
@@ skipping 10 matching lines @@
 
 SimulatorDebugger::SimulatorDebugger(Simulator* sim) {
   sim_ = sim;
 }
 
 
 SimulatorDebugger::~SimulatorDebugger() {
 }
 
 
+void SimulatorDebugger::Attach(Instr* instr, const char* message) {
+  sim_->set_debugger_attached(true);
+  Stop(instr, message);
+}
+
+
 void SimulatorDebugger::Stop(Instr* instr, const char* message) {
   OS::Print("Simulator hit %s\n", message);
   Debug();
 }
 
 
 static Register LookupCpuRegisterByName(const char* name) {
   static const char* kNames[] = {
       "r0",  "r1",  "r2",  "r3",
       "r4",  "r5",  "r6",  "r7",
@@ skipping 136 matching lines @@
 void SimulatorDebugger::RedoBreakpoints() {
   if (sim_->break_pc_ != NULL) {
     sim_->break_pc_->SetInstructionBits(Instr::kBreakPointInstruction);
   }
 }
 
 
 void SimulatorDebugger::Debug() {
   intptr_t last_pc = -1;
   bool done = false;
-  bool decoded = true;
 
 #define COMMAND_SIZE 63
 #define ARG_SIZE 255
 
 #define STR(a) #a
 #define XSTR(a) STR(a)
 
   char cmd[COMMAND_SIZE + 1];
   char arg1[ARG_SIZE + 1];
   char arg2[ARG_SIZE + 1];
 
+  // If the simulator does not already have debugging attached, then return---
+  // we aren't in interactive mode.
+  if (!sim_->debugger_attached()) {
+    return;
+  }
+
   // make sure to have a proper terminating character if reaching the limit
   cmd[COMMAND_SIZE] = 0;
   arg1[ARG_SIZE] = 0;
   arg2[ARG_SIZE] = 0;
 
   // Undo all set breakpoints while running in the debugger shell. This will
   // make them invisible to all commands.
   UndoBreakpoints();
 
   while (!done) {
     if (last_pc != sim_->get_pc()) {
       last_pc = sim_->get_pc();
-      decoded = Disassembler::Disassemble(last_pc, last_pc + Instr::kInstrSize);
+      Disassembler::Disassemble(last_pc, last_pc + Instr::kInstrSize);
     }
     char* line = ReadLine("sim> ");
     if (line == NULL) {
       break;
     } else {
       // Use sscanf to parse the individual parts of the command line. At the
       // moment no command expects more than two parameters.
       int args = SScanF(line,
                         "%" XSTR(COMMAND_SIZE) "s "
                         "%" XSTR(ARG_SIZE) "s "
@@ skipping 13 matching lines @@
                   "p/print <reg or value or *addr> -- print integer value\n"
                   "pf/printfloat <freg or *addr> -- print float value\n"
                   "po/printobject <*reg or *addr> -- print object\n"
                   "si/stepi -- single step an instruction\n"
                   "unstop -- if current pc is a stop instr make it a nop\n"
                   "q/quit -- Quit the debugger and exit the program\n");
       } else if ((strcmp(cmd, "quit") == 0) || (strcmp(cmd, "q") == 0)) {
         OS::Print("Quitting\n");
         OS::Exit(0);
       } else if ((strcmp(cmd, "si") == 0) || (strcmp(cmd, "stepi") == 0)) {
-        if (decoded) {
-          sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
-        } else {
-          OS::Print("Instruction could not be decoded. Stepping disabled.\n");
-        }
+        sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
       } else if ((strcmp(cmd, "c") == 0) || (strcmp(cmd, "cont") == 0)) {
-        if (decoded) {
-          // Execute the one instruction we broke at with breakpoints disabled.
-          sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
-          // Leave the debugger shell.
-          done = true;
-        } else {
-          OS::Print("Instruction could not be decoded. Cannot continue.\n");
-        }
+        // Execute the one instruction we broke at with breakpoints disabled.
+        sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
+        // Leave the debugger shell.
+        done = true;
       } else if ((strcmp(cmd, "p") == 0) || (strcmp(cmd, "print") == 0)) {
         if (args == 2) {
           uint32_t value;
           if (GetValue(arg1, &value)) {
             OS::Print("%s: %u 0x%x\n", arg1, value, value);
           } else {
             OS::Print("%s unrecognized\n", arg1);
           }
         } else {
           OS::Print("print <reg or value or *addr>\n");
@@ skipping 188 matching lines @@
   // handling stack overflow exceptions. To be safe in potential
   // stack underflows we also add some underflow buffer space.
   stack_ = new char[(Isolate::GetSpecifiedStackSize() +
                      Isolate::kStackSizeBuffer +
                      kSimulatorStackUnderflowSize)];
   icount_ = 0;
   delay_slot_ = false;
   break_pc_ = NULL;
   break_instr_ = 0;
 
+  debugger_attached_ = false;
+
   // Setup architecture state.
   // All registers are initialized to zero to start with.
   for (int i = 0; i < kNumberOfCpuRegisters; i++) {
     registers_[i] = 0;
   }
   pc_ = 0;
   // The sp is initialized to point to the bottom (high address) of the
   // allocated stack area.
   registers_[SP] = StackTop();
 }
@@ skipping 42 matching lines @@
   fregisters_[reg] = value;
 }
 
 
 double Simulator::get_fregister(FRegister reg) const {
   ASSERT((reg >= 0) && (reg < kNumberOfFRegisters));
   return fregisters_[reg];
 }
 
 
+void Simulator::UnimplementedInstruction(Instr* instr) {
+  char buffer[64];
+  snprintf(buffer, sizeof(buffer), "Unimplemented instruction: pc=%p\n", instr);
+  SimulatorDebugger dbg(this);
+  dbg.Stop(instr, buffer);
+  FATAL("Cannot continue execution after unimplemented instruction.");
+}
+
+
 void Simulator::HandleIllegalAccess(uword addr, Instr* instr) {
   uword fault_pc = get_pc();
   // The debugger will not be able to single step past this instruction, but
   // it will be possible to disassemble the code and inspect registers.
   char buffer[128];
   snprintf(buffer, sizeof(buffer),
            "illegal memory access at 0x%"Px", pc=0x%"Px"\n",
            addr, fault_pc);
   SimulatorDebugger dbg(this);
   dbg.Stop(instr, buffer);
@@ skipping 131 matching lines @@
     case AND: {
       ASSERT(instr->SaField() == 0);
       // Format(instr, "and 'rd, 'rs, 'rt");
       int32_t rs_val = get_register(instr->RsField());
       int32_t rt_val = get_register(instr->RtField());
       set_register(instr->RdField(), rs_val & rt_val);
       break;
     }
     case BREAK: {
       SimulatorDebugger dbg(this);
-      dbg.Stop(instr, "breakpoint");
+      dbg.Attach(instr, "breakpoint");
       break;
     }
     case DIV: {
       ASSERT(instr->RdField() == 0);
       ASSERT(instr->SaField() == 0);
       // Format(instr, "div 'rs, 'rt");
       int32_t rs_val = get_register(instr->RsField());
       int32_t rt_val = get_register(instr->RtField());
       if (rt_val == 0) {
         // Results are unpredictable.
@@ skipping 208 matching lines @@
     case XOR: {
       ASSERT(instr->SaField() == 0);
       // Format(instr, "xor 'rd, 'rs, 'rt");
       int32_t rs_val = get_register(instr->RsField());
       int32_t rt_val = get_register(instr->RtField());
       set_register(instr->RdField(), rs_val ^ rt_val);
       break;
     }
     default: {
       OS::PrintErr("DecodeSpecial: 0x%x\n", instr->InstructionBits());
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
 }
 
 
 void Simulator::DecodeSpecial2(Instr* instr) {
   ASSERT(instr->OpcodeField() == SPECIAL2);
   switch (instr->FunctionField()) {
     case CLO: {
@@ skipping 21 matching lines @@
           rs_val <<= 1;
         }
       } else {
         bitcount = 32;
       }
       set_register(instr->RdField(), bitcount);
       break;
     }
     default: {
       OS::PrintErr("DecodeSpecial2: 0x%x\n", instr->InstructionBits());
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
 }
 
 
 void Simulator::InstructionDecode(Instr* instr) {
   switch (instr->OpcodeField()) {
     case SPECIAL: {
       DecodeSpecial(instr);
@@ skipping 129 matching lines @@
       if (Simulator::IsIllegalAddress(addr)) {
         HandleIllegalAccess(addr, instr);
       } else {
         WriteW(addr, rt_val, instr);
       }
       break;
     }
     default: {
       OS::PrintErr("Undecoded instruction: 0x%x at %p\n",
                     instr->InstructionBits(), instr);
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
   pc_ += Instr::kInstrSize;
 }
 
 
 void Simulator::ExecuteDelaySlot() {
   ASSERT(pc_ != kEndSimulatingPC);
   delay_slot_ = true;
   icount_++;
+  Instr* instr = Instr::At(pc_ + Instr::kInstrSize);
   if (icount_ == FLAG_stop_sim_at) {
-    UNIMPLEMENTED();
+    SimulatorDebugger dbg(this);
+    dbg.Attach(instr, "Instruction count reached");
   }
-  Instr* instr = Instr::At(pc_ + Instr::kInstrSize);
   InstructionDecode(instr);
   delay_slot_ = false;
 }
 
 
 void Simulator::Execute() {
   if (FLAG_stop_sim_at == 0) {
     // Fast version of the dispatch loop without checking whether the simulator
     // should be stopping at a particular executed instruction.
     while (pc_ != kEndSimulatingPC) {
       icount_++;
       Instr* instr = Instr::At(pc_);
-      InstructionDecode(instr);
+      if (IsIllegalAddress(pc_)) {
+        HandleIllegalAccess(pc_, instr);
+      } else {
+        InstructionDecode(instr);
+      }
     }
   } else {
     // FLAG_stop_sim_at is at the non-default value. Stop in the debugger when
     // we reach the particular instruction count.
     while (pc_ != kEndSimulatingPC) {
       icount_++;
+      Instr* instr = Instr::At(pc_);
       if (icount_ == FLAG_stop_sim_at) {
-        UNIMPLEMENTED();
+        SimulatorDebugger dbg(this);
+        dbg.Attach(instr, "Instruction count reached");
       } else {
-        Instr* instr = Instr::At(pc_);
-        InstructionDecode(instr);
+        if (IsIllegalAddress(pc_)) {
+          HandleIllegalAccess(pc_, instr);
+        } else {
+          InstructionDecode(instr);
+        }
       }
     }
   }
 }
 
 
 int64_t Simulator::Call(int32_t entry,
                         int32_t parameter0,
                         int32_t parameter1,
                         int32_t parameter2,
@@ skipping 72 matching lines @@
   // Restore the SP register and return R1:R0.
   set_register(SP, sp_before_call);
   return Utils::LowHighTo64Bits(get_register(V0), get_register(V1));
 }
 
 }  // namespace dart
 
 #endif  // !defined(HOST_ARCH_MIPS)
 
 #endif  // defined TARGET_ARCH_MIPS