simulator-arm.cc.svn-base

Google浏览器V8内核代码

// Copyright 2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include <stdlib.h>

#include "v8.h"

#include "disasm.h"
#include "constants-arm.h"
#include "simulator-arm.h"

#if !defined(__arm__)

// Only build the simulator if not compiling for real ARM hardware.
namespace assembler { namespace arm {

using ::v8::internal::Object;
using ::v8::internal::PrintF;
using ::v8::internal::OS;
using ::v8::internal::ReadLine;
using ::v8::internal::DeleteArray;

// This macro provides a platform independent use of sscanf. The reason for
// SScanF not beeing implemented in a platform independent was through
// ::v8::internal::OS in the same way as SNPrintF is that the Windows C Run-Time
// Library does not provide vsscanf.
#ifdef WIN32
#define SScanF sscanf_s
#else
#define SScanF sscanf  // NOLINT
#endif

// The Debugger class is used by the simulator while debugging simulated ARM
// code.
class Debugger {
 public:
  explicit Debugger(Simulator* sim);
  ~Debugger();

  void Stop(Instr* instr);
  void Debug();

 private:
  static const instr_t kBreakpointInstr =
      ((AL << 28) | (7 << 25) | (1 << 24) | break_point);
  static const instr_t kNopInstr =
      ((AL << 28) | (13 << 21));

  Simulator* sim_;

  bool GetValue(char* desc, int32_t* value);

  // Set or delete a breakpoint. Returns true if successful.
  bool SetBreakpoint(Instr* breakpc);
  bool DeleteBreakpoint(Instr* breakpc);

  // Undo and redo all breakpoints. This is needed to bracket disassembly and
  // execution to skip past breakpoints when run from the debugger.
  void UndoBreakpoints();
  void RedoBreakpoints();
};


Debugger::Debugger(Simulator* sim) {
  sim_ = sim;
}


Debugger::~Debugger() {
}


void Debugger::Stop(Instr* instr) {
  const char* str = (const char*)(instr->InstructionBits() & 0x0fffffff);
  PrintF("Simulator hit %s\n", str);
  sim_->set_pc(sim_->get_pc() + Instr::kInstrSize);
  Debug();
}


static const char* reg_names[] = {  "r0",  "r1",  "r2",  "r3",
                                    "r4",  "r5",  "r6",  "r7",
                                    "r8",  "r9", "r10", "r11",
                                   "r12", "r13", "r14", "r15",
                                    "pc",  "lr",  "sp",  "ip",
                                    "fp",  "sl", ""};

static int   reg_nums[]  = {           0,     1,     2,     3,
                                       4,     5,     6,     7,
                                       8,     9,    10,    11,
                                      12,    13,    14,    15,
                                      15,    14,    13,    12,
                                      11,    10};


static int RegNameToRegNum(char* name) {
  int reg = 0;
  while (*reg_names[reg] != 0) {
    if (strcmp(reg_names[reg], name) == 0) {
      return reg_nums[reg];
    }
    reg++;
  }
  return -1;
}


bool Debugger::GetValue(char* desc, int32_t* value) {
  int regnum = RegNameToRegNum(desc);
  if (regnum >= 0) {
    if (regnum == 15) {
      *value = sim_->get_pc();
    } else {
      *value = sim_->get_register(regnum);
    }
    return true;
  } else {
    return SScanF(desc, "%i", value) == 1;
  }
  return false;
}


bool Debugger::SetBreakpoint(Instr* breakpc) {
  // Check if a breakpoint can be set. If not return without any side-effects.
  if (sim_->break_pc_ != NULL) {
    return false;
  }

  // Set the breakpoint.
  sim_->break_pc_ = breakpc;
  sim_->break_instr_ = breakpc->InstructionBits();
  // Not setting the breakpoint instruction in the code itself. It will be set
  // when the debugger shell continues.
  return true;
}


bool Debugger::DeleteBreakpoint(Instr* breakpc) {
  if (sim_->break_pc_ != NULL) {
    sim_->break_pc_->SetInstructionBits(sim_->break_instr_);
  }

  sim_->break_pc_ = NULL;
  sim_->break_instr_ = 0;
  return true;
}


void Debugger::UndoBreakpoints() {
  if (sim_->break_pc_ != NULL) {
    sim_->break_pc_->SetInstructionBits(sim_->break_instr_);
  }
}


void Debugger::RedoBreakpoints() {
  if (sim_->break_pc_ != NULL) {
    sim_->break_pc_->SetInstructionBits(kBreakpointInstr);
  }
}


void Debugger::Debug() {
  intptr_t last_pc = -1;
  bool done = false;

#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];

  // 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()) {
      disasm::Disassembler dasm;
      // use a reasonably large buffer
      v8::internal::EmbeddedVector<char, 256> buffer;
      dasm.InstructionDecode(buffer,
                             reinterpret_cast<byte*>(sim_->get_pc()));
      PrintF("  0x%x  %s\n", sim_->get_pc(), buffer.start());
      last_pc = sim_->get_pc();
    }
    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 "
                        "%" XSTR(ARG_SIZE) "s",
                        cmd, arg1, arg2);
      if ((strcmp(cmd, "si") == 0) || (strcmp(cmd, "stepi") == 0)) {
        sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
      } else if ((strcmp(cmd, "c") == 0) || (strcmp(cmd, "cont") == 0)) {
        // 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) {
          int32_t value;
          if (GetValue(arg1, &value)) {
            PrintF("%s: %d 0x%x\n", arg1, value, value);
          } else {
            PrintF("%s unrecognized\n", arg1);
          }
        } else {
          PrintF("print value\n");
        }
      } else if ((strcmp(cmd, "po") == 0)
                 || (strcmp(cmd, "printobject") == 0)) {
        if (args == 2) {
          int32_t value;
          if (GetValue(arg1, &value)) {
            Object* obj = reinterpret_cast<Object*>(value);
            USE(obj);
            PrintF("%s: \n", arg1);
#if defined(DEBUG)
            obj->PrintLn();
#endif  // defined(DEBUG)
          } else {
            PrintF("%s unrecognized\n", arg1);
          }
        } else {
          PrintF("printobject value\n");
        }
      } else if (strcmp(cmd, "disasm") == 0) {
        disasm::Disassembler dasm;
        // use a reasonably large buffer
        v8::internal::EmbeddedVector<char, 256> buffer;

        byte* cur = NULL;
        byte* end = NULL;

        if (args == 1) {
          cur = reinterpret_cast<byte*>(sim_->get_pc());
          end = cur + (10 * Instr::kInstrSize);
        } else if (args == 2) {
          int32_t value;
          if (GetValue(arg1, &value)) {
            cur = reinterpret_cast<byte*>(value);
            // no length parameter passed, assume 10 instructions
            end = cur + (10 * Instr::kInstrSize);
          }
        } else {
          int32_t value1;
          int32_t value2;
          if (GetValue(arg1, &value1) && GetValue(arg2, &value2)) {
            cur = reinterpret_cast<byte*>(value1);
            end = cur + (value2 * Instr::kInstrSize);
          }
        }

        while (cur < end) {
          dasm.InstructionDecode(buffer, cur);
          PrintF("  0x%x  %s\n", cur, buffer.start());
          cur += Instr::kInstrSize;
        }
      } else if (strcmp(cmd, "gdb") == 0) {
        PrintF("relinquishing control to gdb\n");
        v8::internal::OS::DebugBreak();
        PrintF("regaining control from gdb\n");
      } else if (strcmp(cmd, "break") == 0) {
        if (args == 2) {
          int32_t value;
          if (GetValue(arg1, &value)) {
            if (!SetBreakpoint(reinterpret_cast<Instr*>(value))) {
              PrintF("setting breakpoint failed\n");
            }
          } else {
            PrintF("%s unrecognized\n", arg1);
          }
        } else {
          PrintF("break addr\n");
        }
      } else if (strcmp(cmd, "del") == 0) {
        if (!DeleteBreakpoint(NULL)) {
          PrintF("deleting breakpoint failed\n");
        }
      } else if (strcmp(cmd, "flags") == 0) {
        PrintF("N flag: %d; ", sim_->n_flag_);
        PrintF("Z flag: %d; ", sim_->z_flag_);
        PrintF("C flag: %d; ", sim_->c_flag_);
        PrintF("V flag: %d\n", sim_->v_flag_);
      } else if (strcmp(cmd, "unstop") == 0) {
        intptr_t stop_pc = sim_->get_pc() - Instr::kInstrSize;
        Instr* stop_instr = reinterpret_cast<Instr*>(stop_pc);
        if (stop_instr->ConditionField() == special_condition) {
          stop_instr->SetInstructionBits(kNopInstr);
        } else {
          PrintF("Not at debugger stop.");
        }
      } else {
        PrintF("Unknown command: %s\n", cmd);
      }
    }
    DeleteArray(line);
  }

  // Add all the breakpoints back to stop execution and enter the debugger
  // shell when hit.
  RedoBreakpoints();

#undef COMMAND_SIZE
#undef ARG_SIZE

#undef STR
#undef XSTR
}


Simulator::Simulator() {
  // Setup simulator support first. Some of this information is needed to
  // setup the architecture state.
  size_t stack_size = 1 * 1024*1024;  // allocate 1MB for stack
  stack_ = reinterpret_cast<char*>(malloc(stack_size));
  pc_modified_ = false;
  icount_ = 0;
  break_pc_ = NULL;
  break_instr_ = 0;

  // Setup architecture state.
  // All registers are initialized to zero to start with.
  for (int i = 0; i < num_registers; i++) {
    registers_[i] = 0;
  }
  n_flag_ = false;
  z_flag_ = false;
  c_flag_ = false;
  v_flag_ = false;

  // The sp is initialized to point to the bottom (high address) of the
  // allocated stack area. To be safe in potential stack underflows we leave
  // some buffer below.
  registers_[sp] = reinterpret_cast<int32_t>(stack_) + stack_size - 64;
  // The lr and pc are initialized to a known bad value that will cause an
  // access violation if the simulator ever tries to execute it.
  registers_[pc] = bad_lr;
  registers_[lr] = bad_lr;
}


// This is the Simulator singleton. Currently only one thread is supported by
// V8. If we had multiple threads, then we should have a Simulator instance on
// a per thread basis.
static Simulator* the_sim = NULL;


// Get the active Simulator for the current thread. See comment above about
// using a singleton currently.
Simulator* Simulator::current() {
  if (the_sim == NULL) {
    the_sim = new Simulator();
  }
  return the_sim;
}


// Sets the register in the architecture state. It will also deal with updating
// Simulator internal state for special registers such as PC.
void Simulator::set_register(int reg, int32_t value) {
  ASSERT((reg >= 0) && (reg < num_registers));
  if (reg == pc) {
    pc_modified_ = true;
  }
  registers_[reg] = value;
}


// Get the register from the architecture state. This function does handle
// the special case of accessing the PC register.
int32_t Simulator::get_register(int reg) const {
  ASSERT((reg >= 0) && (reg < num_registers));
  return registers_[reg] + ((reg == pc) ? Instr::kPCReadOffset : 0);
}


// Raw access to the PC register.
void Simulator::set_pc(int32_t value) {
  pc_modified_ = true;
  registers_[pc] = value;
}


// Raw access to the PC register without the special adjustment when reading.
int32_t Simulator::get_pc() const {
  return registers_[pc];
}


// Returns the limit of the stack area to enable checking for stack overflows.
uintptr_t Simulator::StackLimit() const {
  // Leave a safety margin of 256 bytes to prevent overrunning the stack when
  // pushing values.
  return reinterpret_cast<uintptr_t>(stack_) + 256;
}


// Unsupported instructions use Format to print an error and stop execution.
void Simulator::Format(Instr* instr, const char* format) {
  PrintF("Simulator found unsupported instruction:\n 0x%x: %s\n",
         instr, format);
  UNIMPLEMENTED();
}


// Checks if the current instruction should be executed based on its
// condition bits.
bool Simulator::ConditionallyExecute(Instr* instr) {
  switch (instr->ConditionField()) {
    case EQ: return z_flag_;
    case NE: return !z_flag_;
    case CS: return c_flag_;
    case CC: return !c_flag_;
    case MI: return n_flag_;
    case PL: return !n_flag_;
    case VS: return v_flag_;
    case VC: return !v_flag_;
    case HI: return c_flag_ && !z_flag_;
    case LS: return !c_flag_ || z_flag_;
    case GE: return n_flag_ == v_flag_;
    case LT: return n_flag_ != v_flag_;
    case GT: return !z_flag_ && (n_flag_ == v_flag_);
    case LE: return z_flag_ || (n_flag_ != v_flag_);
    case AL: return true;
    default: UNREACHABLE();
  }
  return false;
}


// Calculate and set the Negative and Zero flags.
void Simulator::SetNZFlags(int32_t val) {
  n_flag_ = (val < 0);
  z_flag_ = (val == 0);
}


// Set the Carry flag.
void Simulator::SetCFlag(bool val) {
  c_flag_ = val;
}


// Set the oVerflow flag.
void Simulator::SetVFlag(bool val) {
  v_flag_ = val;
}


// Calculate C flag value for additions.
bool Simulator::CarryFrom(int32_t left, int32_t right) {
  uint32_t uleft = static_cast<uint32_t>(left);
  uint32_t uright = static_cast<uint32_t>(right);
  uint32_t urest  = 0xffffffffU - uleft;

  return (uright > urest);
}


// Calculate C flag value for subtractions.
bool Simulator::BorrowFrom(int32_t left, int32_t right) {
  uint32_t uleft = static_cast<uint32_t>(left);