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

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

#ifdef JS_SIMULATOR_ARM

#  include "mozilla/Atomics.h"

#  include "jit/arm/Architecture-arm.h"
#  include "jit/arm/disasm/Disasm-arm.h"
#  include "jit/IonTypes.h"
#  include "js/AllocPolicy.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);

// VFP rounding modes. See ARM DDI 0406B Page A2-29.
enum VFPRoundingMode {
  SimRN = 0 << 22,  // Round to Nearest.
  SimRP = 1 << 22,  // Round towards Plus Infinity.
  SimRM = 2 << 22,  // Round towards Minus Infinity.
  SimRZ = 3 << 22,  // Round towards zero.

  // Aliases.
  kRoundToNearest = SimRN,
  kRoundToPlusInf = SimRP,
  kRoundToMinusInf = SimRM,
  kRoundToZero = SimRZ
};

const uint32_t kVFPRoundingModeMask = 3 << 22;

typedef int32_t Instr;
class SimInstruction;

// Per thread simulator state.
class Simulator {
 public:
  friend class ArmDebugger;
  enum Register {
    no_reg = -1,
    r0 = 0,
    r1,
    r2,
    r3,
    r4,
    r5,
    r6,
    r7,
    r8,
    r9,
    r10,
    r11,
    r12,
    r13,
    r14,
    r15,
    num_registers,
    fp = 11,
    ip = 12,
    sp = 13,
    lr = 14,
    pc = 15,
    s0 = 0,
    s1,
    s2,
    s3,
    s4,
    s5,
    s6,
    s7,
    s8,
    s9,
    s10,
    s11,
    s12,
    s13,
    s14,
    s15,
    s16,
    s17,
    s18,
    s19,
    s20,
    s21,
    s22,
    s23,
    s24,
    s25,
    s26,
    s27,
    s28,
    s29,
    s30,
    s31,
    num_s_registers = 32,
    d0 = 0,
    d1,
    d2,
    d3,
    d4,
    d5,
    d6,
    d7,
    d8,
    d9,
    d10,
    d11,
    d12,
    d13,
    d14,
    d15,
    d16,
    d17,
    d18,
    d19,
    d20,
    d21,
    d22,
    d23,
    d24,
    d25,
    d26,
    d27,
    d28,
    d29,
    d30,
    d31,
    num_d_registers = 32,
    q0 = 0,
    q1,
    q2,
    q3,
    q4,
    q5,
    q6,
    q7,
    q8,
    q9,
    q10,
    q11,
    q12,
    q13,
    q14,
    q15,
    num_q_registers = 16
  };

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

  // Disassemble some instructions starting at instr and print them
  // on stdout.  Useful for working within GDB after a MOZ_CRASH(),
  // among other things.
  //
  // Typical use within a crashed instruction decoding method is simply:
  //
  //   call Simulator::disassemble(instr, 1)
  //
  // or use one of the more convenient inline methods below.
  static void disassemble(SimInstruction* instr, size_t n);

  // Disassemble one instruction.
  // "call disasm(instr)"
  void disasm(SimInstruction* instr);

  // Disassemble n instructions starting at instr.
  // "call disasm(instr, 3)"
  void disasm(SimInstruction* instr, size_t n);

  // Skip backwards m instructions before starting, then disassemble n
  // instructions.
  // "call disasm(instr, 3, 7)"
  void disasm(SimInstruction* instr, size_t m, size_t n);

  uintptr_t* addressOfStackLimit();

  // Accessors for register state. Reading the pc value adheres to the ARM
  // architecture specification and is off by a 8 from the currently executing
  // instruction.
  void set_register(int reg, int32_t value);
  int32_t get_register(int reg) const;
  double get_double_from_register_pair(int reg);
  void set_register_pair_from_double(int reg, double* value);
  void set_dw_register(int dreg, const int* dbl);

  // Support for VFP.
  void get_d_register(int dreg, uint64_t* value);
  void set_d_register(int dreg, const uint64_t* value);
  void get_d_register(int dreg, uint32_t* value);
  void set_d_register(int dreg, const uint32_t* value);
  void get_q_register(int qreg, uint64_t* value);
  void set_q_register(int qreg, const uint64_t* value);
  void get_q_register(int qreg, uint32_t* value);
  void set_q_register(int qreg, const uint32_t* value);
  void set_s_register(int reg, unsigned int value);
  unsigned int get_s_register(int reg) const;

  void set_d_register_from_double(int dreg, const double& dbl) {
    setVFPRegister<double, 2>(dreg, dbl);
  }
  void get_double_from_d_register(int dreg, double* out) {
    getFromVFPRegister<double, 2>(dreg, out);
  }
  void set_s_register_from_float(int sreg, const float flt) {
    setVFPRegister<float, 1>(sreg, flt);
  }
  void get_float_from_s_register(int sreg, float* out) {
    getFromVFPRegister<float, 1>(sreg, out);
  }
  void set_s_register_from_sinteger(int sreg, const int sint) {
    setVFPRegister<int, 1>(sreg, sint);
  }
  int get_sinteger_from_s_register(int sreg) {
    int ret;
    getFromVFPRegister<int, 1>(sreg, &ret);
    return ret;
  }

  // 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();

  uintptr_t stackLimit() const;
  bool overRecursed(uintptr_t newsp = 0) const;
  bool overRecursedWithExtra(uint32_t extra) const;

  // Executes ARM 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, ...);

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

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

 private:
  enum special_values {
    // Known bad pc value to ensure that the simulator does not execute
    // without being properly setup.
    bad_lr = -1,
    // A pc value used to signal the simulator to stop execution. Generally
    // the lr 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
  };

  // ForbidUnaligned means "always fault on unaligned access".
  //
  // AllowUnaligned means "allow the unaligned access if other conditions are
  // met".  The "other conditions" vary with the instruction: For all
  // instructions the base condition is !HasAlignmentFault(), ie, the chip is
  // configured to allow unaligned accesses.  For instructions like VLD1
  // there is an additional constraint that the alignment attribute in the
  // instruction must be set to "default alignment".

  enum UnalignedPolicy { ForbidUnaligned, AllowUnaligned };

  bool init();

  // Checks if the current instruction should be executed based on its
  // condition bits.
  inline bool conditionallyExecute(SimInstruction* instr);

  // Helper functions to set the conditional flags in the architecture state.
  void setNZFlags(int32_t val);
  void setCFlag(bool val);
  void setVFlag(bool val);
  bool carryFrom(int32_t left, int32_t right, int32_t carry = 0);
  bool borrowFrom(int32_t left, int32_t right);
  bool overflowFrom(int32_t alu_out, int32_t left, int32_t right,
                    bool addition);

  inline int getCarry() { return c_flag_ ? 1 : 0; };

  // Support for VFP.
  void compute_FPSCR_Flags(double val1, double val2);
  void copy_FPSCR_to_APSR();
  inline void canonicalizeNaN(double* value);
  inline void canonicalizeNaN(float* value);

  // Helper functions to decode common "addressing" modes
  int32_t getShiftRm(SimInstruction* instr, bool* carry_out);
  int32_t getImm(SimInstruction* instr, bool* carry_out);
  int32_t processPU(SimInstruction* instr, int num_regs, int operand_size,
                    intptr_t* start_address, intptr_t* end_address);
  void handleRList(SimInstruction* instr, bool load);
  void handleVList(SimInstruction* inst);
  void softwareInterrupt(SimInstruction* instr);

  // Stop helper functions.
  inline bool isStopInstruction(SimInstruction* instr);
  inline bool isWatchedStop(uint32_t bkpt_code);
  inline bool isEnabledStop(uint32_t bkpt_code);
  inline void enableStop(uint32_t bkpt_code);
  inline void disableStop(uint32_t bkpt_code);
  inline void increaseStopCounter(uint32_t bkpt_code);
  void printStopInfo(uint32_t code);

  // Handle a wasm interrupt triggered by an async signal handler.
  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(!wasm::CodeExists)) {
      return false;
    }

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

    set_pc(int32_t(newPC));
    return true;
  }

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

  inline uint8_t readExBU(int32_t addr);
  inline int32_t writeExB(int32_t addr, uint8_t value);

  inline uint16_t readHU(int32_t addr, SimInstruction* instr);
  inline int16_t readH(int32_t addr, SimInstruction* instr);
  // Note: Overloaded on the sign of the value.
  inline void writeH(int32_t addr, uint16_t value, SimInstruction* instr);
  inline void writeH(int32_t addr, int16_t value, SimInstruction* instr);

  inline uint16_t readExHU(int32_t addr, SimInstruction* instr);
  inline int32_t writeExH(int32_t addr, uint16_t value, SimInstruction* instr);

  inline int readW(int32_t addr, SimInstruction* instr,
                   UnalignedPolicy f = ForbidUnaligned);
  inline void writeW(int32_t addr, int value, SimInstruction* instr,
                     UnalignedPolicy f = ForbidUnaligned);

  inline uint64_t readQ(int32_t addr, SimInstruction* instr,
                        UnalignedPolicy f = ForbidUnaligned);
  inline void writeQ(int32_t addr, uint64_t value, SimInstruction* instr,
                     UnalignedPolicy f = ForbidUnaligned);

  inline int readExW(int32_t addr, SimInstruction* instr);
  inline int writeExW(int32_t addr, int value, SimInstruction* instr);

  int32_t* readDW(int32_t addr);
  void writeDW(int32_t addr, int32_t value1, int32_t value2);

  int32_t readExDW(int32_t addr, int32_t* hibits);
  int32_t writeExDW(int32_t addr, int32_t value1, int32_t value2);

  // Executing is handled based on the instruction type.
  // Both type 0 and type 1 rolled into one.
  void decodeType01(SimInstruction* instr);
  void decodeType2(SimInstruction* instr);
  void decodeType3(SimInstruction* instr);
  void decodeType4(SimInstruction* instr);
  void decodeType5(SimInstruction* instr);
  void decodeType6(SimInstruction* instr);
  void decodeType7(SimInstruction* instr);

  // Support for VFP.
  void decodeTypeVFP(SimInstruction* instr);
  void decodeType6CoprocessorIns(SimInstruction* instr);
  void decodeSpecialCondition(SimInstruction* instr);

  void decodeVMOVBetweenCoreAndSinglePrecisionRegisters(SimInstruction* instr);
  void decodeVCMP(SimInstruction* instr);
  void decodeVCVTBetweenDoubleAndSingle(SimInstruction* instr);
  void decodeVCVTBetweenFloatingPointAndInteger(SimInstruction* instr);
  void decodeVCVTBetweenFloatingPointAndIntegerFrac(SimInstruction* instr);

  // Support for some system functions.
  void decodeType7CoprocessorIns(SimInstruction* instr);

  // Executes one instruction.
  void instructionDecode(SimInstruction* instr);

 public:
  static int64_t StopSimAt;

  // For testing the MoveResolver code, a MoveResolver is set up, and
  // the VFP registers are loaded with pre-determined values,
  // then the sequence of code is simulated.  In order to test this with the
  // simulator, the callee-saved registers can't be trashed. This flag
  // disables that feature.
  bool skipCalleeSavedRegsCheck;

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

 private:
  // Handle arguments and return value for runtime FP functions.
  void getFpArgs(double* x, double* y, int32_t* z);
  void getFpFromStack(int32_t* stack, double* x1);
  void setCallResultDouble(double result);
  void setCallResultFloat(float result);
  void setCallResult(int64_t res);
  void scratchVolatileRegisters(bool scratchFloat = true);

  template <class ReturnType, int register_size>
  void getFromVFPRegister(int reg_index, ReturnType* out);

  template <class InputType, int register_size>
  void setVFPRegister(int reg_index, const InputType& value);

  void callInternal(uint8_t* entry);

  // Architecture state.
  // Saturating instructions require a Q flag to indicate saturation.
  // There is currently no way to read the CPSR directly, and thus read the Q
  // flag, so this is left unimplemented.
  int32_t registers_[16];
  bool n_flag_;
  bool z_flag_;
  bool c_flag_;
  bool v_flag_;

  // VFP architecture state.
  uint32_t vfp_registers_[num_d_registers * 2];
  bool n_flag_FPSCR_;
  bool z_flag_FPSCR_;
  bool c_flag_FPSCR_;
  bool v_flag_FPSCR_;

  // VFP rounding mode. See ARM DDI 0406B Page A2-29.
  VFPRoundingMode FPSCR_rounding_mode_;
  bool FPSCR_default_NaN_mode_;

  // VFP FP exception flags architecture state.
  bool inv_op_vfp_flag_;
  bool div_zero_vfp_flag_;
  bool overflow_vfp_flag_;
  bool underflow_vfp_flag_;
  bool inexact_vfp_flag_;

  // Simulator support.
  char* stack_;
  uintptr_t stackLimit_;
  bool pc_modified_;
  int64_t icount_;

  // 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;

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

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

 public:
  int64_t icount() { return icount_; }

 private:
  // Exclusive access monitor
  void exclusiveMonitorSet(uint64_t value);
  uint64_t exclusiveMonitorGetAndClear(bool* held);
  void exclusiveMonitorClear();

  bool exclusiveMonitorHeld_;
  uint64_t exclusiveMonitor_;
};

// 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_ARM */

#endif /* jit_arm_Simulator_arm_h */