path: root/js/src/jit/mips32/Simulator-mips32.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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#ifndef jit_mips32_Simulator_mips32_h
#define jit_mips32_Simulator_mips32_h

#ifdef JS_SIMULATOR_MIPS32

#  include "mozilla/Atomics.h"

#  include "jit/IonTypes.h"
#  include "js/ProfilingFrameIterator.h"
#  include "threading/Thread.h"
#  include "vm/MutexIDs.h"
#  include "wasm/WasmSignalHandlers.h"

namespace js {

namespace jit {

class JitActivation;

class Simulator;
class Redirection;
class CachePage;
class AutoLockSimulator;

// When the SingleStepCallback is called, the simulator is about to execute
// sim->get_pc() and the current machine state represents the completed
// execution of the previous pc.
typedef void (*SingleStepCallback)(void* arg, Simulator* sim, void* pc);

const intptr_t kPointerAlignment = 4;
const intptr_t kPointerAlignmentMask = kPointerAlignment - 1;

const intptr_t kDoubleAlignment = 8;
const intptr_t kDoubleAlignmentMask = kDoubleAlignment - 1;

// Number of general purpose registers.
const int kNumRegisters = 32;

// In the simulator, the PC register is simulated as the 34th register.
const int kPCRegister = 34;

// Number coprocessor registers.
const int kNumFPURegisters = 32;

// FPU (coprocessor 1) control registers. Currently only FCSR is implemented.
const int kFCSRRegister = 31;
const int kInvalidFPUControlRegister = -1;
const uint32_t kFPUInvalidResult = static_cast<uint32_t>(1 << 31) - 1;

// FCSR constants.
const uint32_t kFCSRInexactFlagBit = 2;
const uint32_t kFCSRUnderflowFlagBit = 3;
const uint32_t kFCSROverflowFlagBit = 4;
const uint32_t kFCSRDivideByZeroFlagBit = 5;
const uint32_t kFCSRInvalidOpFlagBit = 6;

const uint32_t kFCSRInexactCauseBit = 12;
const uint32_t kFCSRUnderflowCauseBit = 13;
const uint32_t kFCSROverflowCauseBit = 14;
const uint32_t kFCSRDivideByZeroCauseBit = 15;
const uint32_t kFCSRInvalidOpCauseBit = 16;

const uint32_t kFCSRInexactFlagMask = 1 << kFCSRInexactFlagBit;
const uint32_t kFCSRUnderflowFlagMask = 1 << kFCSRUnderflowFlagBit;
const uint32_t kFCSROverflowFlagMask = 1 << kFCSROverflowFlagBit;
const uint32_t kFCSRDivideByZeroFlagMask = 1 << kFCSRDivideByZeroFlagBit;
const uint32_t kFCSRInvalidOpFlagMask = 1 << kFCSRInvalidOpFlagBit;

const uint32_t kFCSRFlagMask =
    kFCSRInexactFlagMask | kFCSRUnderflowFlagMask | kFCSROverflowFlagMask |
    kFCSRDivideByZeroFlagMask | kFCSRInvalidOpFlagMask;

const uint32_t kFCSRExceptionFlagMask = kFCSRFlagMask ^ kFCSRInexactFlagMask;

// On MIPS Simulator breakpoints can have different codes:
// - Breaks between 0 and kMaxWatchpointCode are treated as simple watchpoints,
//   the simulator will run through them and print the registers.
// - Breaks between kMaxWatchpointCode and kMaxStopCode are treated as stop()
//   instructions (see Assembler::stop()).
// - Breaks larger than kMaxStopCode are simple breaks, dropping you into the
//   debugger.
const uint32_t kMaxWatchpointCode = 31;
const uint32_t kMaxStopCode = 127;
const uint32_t kWasmTrapCode = 6;

// -----------------------------------------------------------------------------
// Utility functions

typedef uint32_t Instr;
class SimInstruction;

// Per thread simulator state.
class Simulator {
  friend class MipsDebugger;

 public:
  // Registers are declared in order. See "See MIPS Run Linux" chapter 2.
  enum Register {
    no_reg = -1,
    zero_reg = 0,
    at,
    v0,
    v1,
    a0,
    a1,
    a2,
    a3,
    t0,
    t1,
    t2,
    t3,
    t4,
    t5,
    t6,
    t7,
    s0,
    s1,
    s2,
    s3,
    s4,
    s5,
    s6,
    s7,
    t8,
    t9,
    k0,
    k1,
    gp,
    sp,
    s8,
    ra,
    // LO, HI, and pc.
    LO,
    HI,
    pc,  // pc must be the last register.
    kNumSimuRegisters,
    // aliases
    fp = s8
  };

  // Coprocessor registers.
  enum FPURegister {
    f0,
    f1,
    f2,
    f3,
    f4,
    f5,
    f6,
    f7,
    f8,
    f9,
    f10,
    f11,
    f12,
    f13,
    f14,
    f15,  // f12 and f14 are arguments FPURegisters.
    f16,
    f17,
    f18,
    f19,
    f20,
    f21,
    f22,
    f23,
    f24,
    f25,
    f26,
    f27,
    f28,
    f29,
    f30,
    f31,
    kNumFPURegisters
  };

  // Returns nullptr on OOM.
  static Simulator* Create();

  static void Destroy(Simulator* simulator);

  // Constructor/destructor are for internal use only; use the static methods
  // above.
  Simulator();
  ~Simulator();

  // The currently executing Simulator instance. Potentially there can be one
  // for each native thread.
  static Simulator* Current();

  static inline uintptr_t StackLimit() {
    return Simulator::Current()->stackLimit();
  }

  uintptr_t* addressOfStackLimit();

  // Accessors for register state. Reading the pc value adheres to the MIPS
  // architecture specification and is off by a 8 from the currently executing
  // instruction.
  void setRegister(int reg, int32_t value);
  int32_t getRegister(int reg) const;
  double getDoubleFromRegisterPair(int reg);
  // Same for FPURegisters.
  void setFpuRegister(int fpureg, int32_t value);
  void setFpuRegisterFloat(int fpureg, float value);
  void setFpuRegisterFloat(int fpureg, int64_t value);
  void setFpuRegisterDouble(int fpureg, double value);
  void setFpuRegisterDouble(int fpureg, int64_t value);
  int32_t getFpuRegister(int fpureg) const;
  int64_t getFpuRegisterLong(int fpureg) const;
  float getFpuRegisterFloat(int fpureg) const;
  double getFpuRegisterDouble(int fpureg) const;
  void setFCSRBit(uint32_t cc, bool value);
  bool testFCSRBit(uint32_t cc);
  bool setFCSRRoundError(double original, double rounded);

  // Special case of set_register and get_register to access the raw PC value.
  void set_pc(int32_t value);
  int32_t get_pc() const;

  template <typename T>
  T get_pc_as() const {
    return reinterpret_cast<T>(get_pc());
  }

  void enable_single_stepping(SingleStepCallback cb, void* arg);
  void disable_single_stepping();

  // Accessor to the internal simulator stack area.
  uintptr_t stackLimit() const;
  bool overRecursed(uintptr_t newsp = 0) const;
  bool overRecursedWithExtra(uint32_t extra) const;

  // Executes MIPS instructions until the PC reaches end_sim_pc.
  template <bool enableStopSimAt>
  void execute();

  // Sets up the simulator state and grabs the result on return.
  int32_t call(uint8_t* entry, int argument_count, ...);

  // Push an address onto the JS stack.
  uintptr_t pushAddress(uintptr_t address);

  // Pop an address from the JS stack.
  uintptr_t popAddress();

  // Debugger input.
  void setLastDebuggerInput(char* input);
  char* lastDebuggerInput() { return lastDebuggerInput_; }

  // Returns true if pc register contains one of the 'SpecialValues' defined
  // below (bad_ra, end_sim_pc).
  bool has_bad_pc() const;

 private:
  enum SpecialValues {
    // Known bad pc value to ensure that the simulator does not execute
    // without being properly setup.
    bad_ra = -1,
    // A pc value used to signal the simulator to stop execution.  Generally
    // the ra is set to this value on transition from native C code to
    // simulated execution, so that the simulator can "return" to the native
    // C code.
    end_sim_pc = -2,
    // Unpredictable value.
    Unpredictable = 0xbadbeaf
  };

  bool init();

  // Unsupported instructions use Format to print an error and stop execution.
  void format(SimInstruction* instr, const char* format);

  // Read and write memory.
  inline uint32_t readBU(uint32_t addr);
  inline int32_t readB(uint32_t addr);
  inline void writeB(uint32_t addr, uint8_t value);
  inline void writeB(uint32_t addr, int8_t value);

  inline uint16_t readHU(uint32_t addr, SimInstruction* instr);
  inline int16_t readH(uint32_t addr, SimInstruction* instr);
  // Note: Overloaded on the sign of the value.
  inline void writeH(uint32_t addr, uint16_t value, SimInstruction* instr);
  inline void writeH(uint32_t addr, int16_t value, SimInstruction* instr);

  inline int readW(uint32_t addr, SimInstruction* instr);
  inline void writeW(uint32_t addr, int value, SimInstruction* instr);

  inline double readD(uint32_t addr, SimInstruction* instr);
  inline void writeD(uint32_t addr, double value, SimInstruction* instr);

  inline int32_t loadLinkedW(uint32_t addr, SimInstruction* instr);
  inline int32_t storeConditionalW(uint32_t addr, int32_t value,
                                   SimInstruction* instr);

  // Executing is handled based on the instruction type.
  void decodeTypeRegister(SimInstruction* instr);

  // Helper function for decodeTypeRegister.
  void configureTypeRegister(SimInstruction* instr, int32_t& alu_out,
                             int64_t& i64hilo, uint64_t& u64hilo,
                             int32_t& next_pc, int32_t& return_addr_reg,
                             bool& do_interrupt);

  void decodeTypeImmediate(SimInstruction* instr);
  void decodeTypeJump(SimInstruction* instr);

  // Used for breakpoints and traps.
  void softwareInterrupt(SimInstruction* instr);

  // Stop helper functions.
  bool isWatchpoint(uint32_t code);
  void printWatchpoint(uint32_t code);
  void handleStop(uint32_t code, SimInstruction* instr);
  bool isStopInstruction(SimInstruction* instr);
  bool isEnabledStop(uint32_t code);
  void enableStop(uint32_t code);
  void disableStop(uint32_t code);
  void increaseStopCounter(uint32_t code);
  void printStopInfo(uint32_t code);

  JS::ProfilingFrameIterator::RegisterState registerState();

  // Handle any wasm faults, returning true if the fault was handled.
  // This method is rather hot so inline the normal (no-wasm) case.
  bool MOZ_ALWAYS_INLINE handleWasmSegFault(int32_t addr, unsigned numBytes) {
    if (MOZ_LIKELY(!js::wasm::CodeExists)) {
      return false;
    }

    uint8_t* newPC;
    if (!js::wasm::MemoryAccessTraps(registerState(), (uint8_t*)addr, numBytes,
                                     &newPC)) {
      return false;
    }

    LLBit_ = false;
    set_pc(int32_t(newPC));
    return true;
  }

  // Executes one instruction.
  void instructionDecode(SimInstruction* instr);
  // Execute one instruction placed in a branch delay slot.
  void branchDelayInstructionDecode(SimInstruction* instr);

 public:
  static int StopSimAt;

  // Runtime call support.
  static void* RedirectNativeFunction(void* nativeFunction,
                                      ABIFunctionType type);

 private:
  enum Exception {
    kNone,
    kIntegerOverflow,
    kIntegerUnderflow,
    kDivideByZero,
    kNumExceptions
  };
  int16_t exceptions[kNumExceptions];

  // Exceptions.
  void signalExceptions();

  // Handle arguments and return value for runtime FP functions.
  void getFpArgs(double* x, double* y, int32_t* z);
  void getFpFromStack(int32_t* stack, double* x);

  void setCallResultDouble(double result);
  void setCallResultFloat(float result);
  void setCallResult(int64_t res);

  void callInternal(uint8_t* entry);

  // Architecture state.
  // Registers.
  int32_t registers_[kNumSimuRegisters];
  // Coprocessor Registers.
  int32_t FPUregisters_[kNumFPURegisters];
  // FPU control register.
  uint32_t FCSR_;

  bool LLBit_;
  uint32_t LLAddr_;
  int32_t lastLLValue_;

  // Simulator support.
  char* stack_;
  uintptr_t stackLimit_;
  bool pc_modified_;
  int icount_;
  int break_count_;

  // Debugger input.
  char* lastDebuggerInput_;

  // Registered breakpoints.
  SimInstruction* break_pc_;
  Instr break_instr_;

  // Single-stepping support
  bool single_stepping_;
  SingleStepCallback single_step_callback_;
  void* single_step_callback_arg_;

  // A stop is watched if its code is less than kNumOfWatchedStops.
  // Only watched stops support enabling/disabling and the counter feature.
  static const uint32_t kNumOfWatchedStops = 256;

  // Stop is disabled if bit 31 is set.
  static const uint32_t kStopDisabledBit = 1U << 31;

  // A stop is enabled, meaning the simulator will stop when meeting the
  // instruction, if bit 31 of watchedStops_[code].count is unset.
  // The value watchedStops_[code].count & ~(1 << 31) indicates how many times
  // the breakpoint was hit or gone through.
  struct StopCountAndDesc {
    uint32_t count_;
    char* desc_;
  };
  StopCountAndDesc watchedStops_[kNumOfWatchedStops];
};

// Process wide simulator state.
class SimulatorProcess {
  friend class Redirection;
  friend class AutoLockSimulatorCache;

 private:
  // ICache checking.
  struct ICacheHasher {
    typedef void* Key;
    typedef void* Lookup;
    static HashNumber hash(const Lookup& l);
    static bool match(const Key& k, const Lookup& l);
  };

 public:
  typedef HashMap<void*, CachePage*, ICacheHasher, SystemAllocPolicy> ICacheMap;

  static mozilla::Atomic<size_t, mozilla::ReleaseAcquire>
      ICacheCheckingDisableCount;
  static void FlushICache(void* start, size_t size);

  static void checkICacheLocked(SimInstruction* instr);

  static bool initialize() {
    singleton_ = js_new<SimulatorProcess>();
    return singleton_;
  }
  static void destroy() {
    js_delete(singleton_);
    singleton_ = nullptr;
  }

  SimulatorProcess();
  ~SimulatorProcess();

 private:
  static SimulatorProcess* singleton_;

  // This lock creates a critical section around 'redirection_' and
  // 'icache_', which are referenced both by the execution engine
  // and by the off-thread compiler (see Redirection::Get in the cpp file).
  Mutex cacheLock_ MOZ_UNANNOTATED;

  Redirection* redirection_;
  ICacheMap icache_;

 public:
  static ICacheMap& icache() {
    // Technically we need the lock to access the innards of the
    // icache, not to take its address, but the latter condition
    // serves as a useful complement to the former.
    singleton_->cacheLock_.assertOwnedByCurrentThread();
    return singleton_->icache_;
  }

  static Redirection* redirection() {
    singleton_->cacheLock_.assertOwnedByCurrentThread();
    return singleton_->redirection_;
  }

  static void setRedirection(js::jit::Redirection* redirection) {
    singleton_->cacheLock_.assertOwnedByCurrentThread();
    singleton_->redirection_ = redirection;
  }
};

}  // namespace jit
}  // namespace js

#endif /* JS_SIMULATOR_MIPS32 */

#endif /* jit_mips32_Simulator_mips32_h */