EbcExecute.c

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#include "EbcInt.h"
#include "EbcExecute.h"
#include "EbcDebuggerHook.h"
 
//
// Define some useful data size constants to allow switch statements based on
// size of operands or data.
//
#define DATA_SIZE_INVALID  0
#define DATA_SIZE_8        1
#define DATA_SIZE_16       2
#define DATA_SIZE_32       4
#define DATA_SIZE_64       8
#define DATA_SIZE_N        48 // 4 or 8
//
// Structure we'll use to dispatch opcodes to execute functions.
//
typedef struct {
  EFI_STATUS (*ExecuteFunction)(
    IN VM_CONTEXT  *VmPtr
    );
} VM_TABLE_ENTRY;
 
typedef
UINT64
(*DATA_MANIP_EXEC_FUNCTION) (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
INT16
VmReadIndex16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  );
 
INT32
VmReadIndex32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  );
 
INT64
VmReadIndex64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  );
 
UINT8
VmReadMem8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
UINT16
VmReadMem16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
UINT32
VmReadMem32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
UINT64
VmReadMem64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
UINTN
VmReadMemN (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
EFI_STATUS
VmWriteMem8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT8       Data
  );
 
EFI_STATUS
VmWriteMem16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT16      Data
  );
 
EFI_STATUS
VmWriteMem32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT32      Data
  );
 
UINT16
VmReadCode16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
UINT32
VmReadCode32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
UINT64
VmReadCode64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
INT8
VmReadImmed8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
INT16
VmReadImmed16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
INT32
VmReadImmed32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
INT64
VmReadImmed64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  );
 
UINTN
ConvertStackAddr (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  );
 
EFI_STATUS
ExecuteDataManip (
  IN VM_CONTEXT  *VmPtr,
  IN BOOLEAN     IsSignedOp
  );
 
//
// Functions that execute VM opcodes
//
 
EFI_STATUS
ExecuteBREAK (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteJMP (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteJMP8 (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteCALL (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteRET (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteCMP (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteCMPI (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVxx (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVI (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVIn (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVREL (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecutePUSHn (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecutePUSH (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecutePOPn (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecutePOP (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteSignedDataManip (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteUnsignedDataManip (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteLOADSP (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteSTORESP (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVsnd (
  IN VM_CONTEXT  *VmPtr
  );
 
EFI_STATUS
ExecuteMOVsnw (
  IN VM_CONTEXT  *VmPtr
  );
 
//
// Data manipulation subfunctions
//
 
UINT64
ExecuteNOT (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteNEG (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteADD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteSUB (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteMUL (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteMULU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteDIV (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteDIVU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteMOD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteMODU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteAND (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteOR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteXOR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteSHL (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteSHR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteASHR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteEXTNDB (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteEXTNDW (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
UINT64
ExecuteEXTNDD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  );
 
//
// Once we retrieve the operands for the data manipulation instructions,
// call these functions to perform the operation.
//
CONST DATA_MANIP_EXEC_FUNCTION  mDataManipDispatchTable[] = {
  ExecuteNOT,
  ExecuteNEG,
  ExecuteADD,
  ExecuteSUB,
  ExecuteMUL,
  ExecuteMULU,
  ExecuteDIV,
  ExecuteDIVU,
  ExecuteMOD,
  ExecuteMODU,
  ExecuteAND,
  ExecuteOR,
  ExecuteXOR,
  ExecuteSHL,
  ExecuteSHR,
  ExecuteASHR,
  ExecuteEXTNDB,
  ExecuteEXTNDW,
  ExecuteEXTNDD,
};
 
CONST VM_TABLE_ENTRY  mVmOpcodeTable[] = {
  { ExecuteBREAK             }, // opcode 0x00
  { ExecuteJMP               }, // opcode 0x01
  { ExecuteJMP8              }, // opcode 0x02
  { ExecuteCALL              }, // opcode 0x03
  { ExecuteRET               }, // opcode 0x04
  { ExecuteCMP               }, // opcode 0x05 CMPeq
  { ExecuteCMP               }, // opcode 0x06 CMPlte
  { ExecuteCMP               }, // opcode 0x07 CMPgte
  { ExecuteCMP               }, // opcode 0x08 CMPulte
  { ExecuteCMP               }, // opcode 0x09 CMPugte
  { ExecuteUnsignedDataManip }, // opcode 0x0A NOT
  { ExecuteSignedDataManip   }, // opcode 0x0B NEG
  { ExecuteSignedDataManip   }, // opcode 0x0C ADD
  { ExecuteSignedDataManip   }, // opcode 0x0D SUB
  { ExecuteSignedDataManip   }, // opcode 0x0E MUL
  { ExecuteUnsignedDataManip }, // opcode 0x0F MULU
  { ExecuteSignedDataManip   }, // opcode 0x10 DIV
  { ExecuteUnsignedDataManip }, // opcode 0x11 DIVU
  { ExecuteSignedDataManip   }, // opcode 0x12 MOD
  { ExecuteUnsignedDataManip }, // opcode 0x13 MODU
  { ExecuteUnsignedDataManip }, // opcode 0x14 AND
  { ExecuteUnsignedDataManip }, // opcode 0x15 OR
  { ExecuteUnsignedDataManip }, // opcode 0x16 XOR
  { ExecuteUnsignedDataManip }, // opcode 0x17 SHL
  { ExecuteUnsignedDataManip }, // opcode 0x18 SHR
  { ExecuteSignedDataManip   }, // opcode 0x19 ASHR
  { ExecuteUnsignedDataManip }, // opcode 0x1A EXTNDB
  { ExecuteUnsignedDataManip }, // opcode 0x1B EXTNDW
  { ExecuteUnsignedDataManip }, // opcode 0x1C EXTNDD
  { ExecuteMOVxx             }, // opcode 0x1D MOVBW
  { ExecuteMOVxx             }, // opcode 0x1E MOVWW
  { ExecuteMOVxx             }, // opcode 0x1F MOVDW
  { ExecuteMOVxx             }, // opcode 0x20 MOVQW
  { ExecuteMOVxx             }, // opcode 0x21 MOVBD
  { ExecuteMOVxx             }, // opcode 0x22 MOVWD
  { ExecuteMOVxx             }, // opcode 0x23 MOVDD
  { ExecuteMOVxx             }, // opcode 0x24 MOVQD
  { ExecuteMOVsnw            }, // opcode 0x25 MOVsnw
  { ExecuteMOVsnd            }, // opcode 0x26 MOVsnd
  { NULL                     }, // opcode 0x27
  { ExecuteMOVxx             }, // opcode 0x28 MOVqq
  { ExecuteLOADSP            }, // opcode 0x29 LOADSP SP1, R2
  { ExecuteSTORESP           }, // opcode 0x2A STORESP R1, SP2
  { ExecutePUSH              }, // opcode 0x2B PUSH {@}R1 [imm16]
  { ExecutePOP               }, // opcode 0x2C POP {@}R1 [imm16]
  { ExecuteCMPI              }, // opcode 0x2D CMPIEQ
  { ExecuteCMPI              }, // opcode 0x2E CMPILTE
  { ExecuteCMPI              }, // opcode 0x2F CMPIGTE
  { ExecuteCMPI              }, // opcode 0x30 CMPIULTE
  { ExecuteCMPI              }, // opcode 0x31 CMPIUGTE
  { ExecuteMOVxx             }, // opcode 0x32 MOVN
  { ExecuteMOVxx             }, // opcode 0x33 MOVND
  { NULL                     }, // opcode 0x34
  { ExecutePUSHn             }, // opcode 0x35
  { ExecutePOPn              }, // opcode 0x36
  { ExecuteMOVI              }, // opcode 0x37 - mov immediate data
  { ExecuteMOVIn             }, // opcode 0x38 - mov immediate natural
  { ExecuteMOVREL            }, // opcode 0x39 - move data relative to PC
  { NULL                     }, // opcode 0x3a
  { NULL                     }, // opcode 0x3b
  { NULL                     }, // opcode 0x3c
  { NULL                     }, // opcode 0x3d
  { NULL                     }, // opcode 0x3e
  { NULL                     }  // opcode 0x3f
};
 
//
// Length of JMP instructions, depending on upper two bits of opcode.
//
CONST UINT8  mJMPLen[] = { 2, 2, 6, 10 };
 
EFI_STATUS
EFIAPI
EbcExecuteInstructions (
  IN EFI_EBC_VM_TEST_PROTOCOL  *This,
  IN VM_CONTEXT                *VmPtr,
  IN OUT UINTN                 *InstructionCount
  )
{
  UINTN       ExecFunc;
  EFI_STATUS  Status;
  UINTN       InstructionsLeft;
  UINTN       SavedInstructionCount;
 
  Status = EFI_SUCCESS;
 
  if (*InstructionCount == 0) {
    InstructionsLeft = 1;
  } else {
    InstructionsLeft = *InstructionCount;
  }
 
  SavedInstructionCount = *InstructionCount;
  *InstructionCount     = 0;
 
  //
  // Index into the opcode table using the opcode byte for this instruction.
  // This gives you the execute function, which we first test for null, then
  // call it if it's not null.
  //
  while (InstructionsLeft != 0) {
    ExecFunc = (UINTN)mVmOpcodeTable[(*VmPtr->Ip & OPCODE_M_OPCODE)].ExecuteFunction;
    if (ExecFunc == (UINTN)NULL) {
      EbcDebugSignalException (EXCEPT_EBC_INVALID_OPCODE, EXCEPTION_FLAG_FATAL, VmPtr);
      return EFI_UNSUPPORTED;
    } else {
      mVmOpcodeTable[(*VmPtr->Ip & OPCODE_M_OPCODE)].ExecuteFunction (VmPtr);
      *InstructionCount = *InstructionCount + 1;
    }
 
    //
    // Decrement counter if applicable
    //
    if (SavedInstructionCount != 0) {
      InstructionsLeft--;
    }
  }
 
  return Status;
}
 
EFI_STATUS
EbcExecute (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINTN                             ExecFunc;
  UINT8                             StackCorrupted;
  EFI_STATUS                        Status;
  EFI_EBC_SIMPLE_DEBUGGER_PROTOCOL  *EbcSimpleDebugger;
 
  mVmPtr            = VmPtr;
  EbcSimpleDebugger = NULL;
  Status            = EFI_SUCCESS;
  StackCorrupted    = 0;
 
  //
  // Make sure the magic value has been put on the stack before we got here.
  //
  if (*VmPtr->StackMagicPtr != (UINTN)VM_STACK_KEY_VALUE) {
    StackCorrupted = 1;
  }
 
  VmPtr->FramePtr = (VOID *)((UINT8 *)(UINTN)VmPtr->Gpr[0] + 8);
 
  //
  // Try to get the debug support for EBC
  //
  DEBUG_CODE_BEGIN ();
  Status = gBS->LocateProtocol (
                  &gEfiEbcSimpleDebuggerProtocolGuid,
                  NULL,
                  (VOID **)&EbcSimpleDebugger
                  );
  if (EFI_ERROR (Status)) {
    EbcSimpleDebugger = NULL;
  }
 
  DEBUG_CODE_END ();
 
  //
  // Save the start IP for debug. For example, if we take an exception we
  // can print out the location of the exception relative to the entry point,
  // which could then be used in a disassembly listing to find the problem.
  //
  VmPtr->EntryPoint = (VOID *)VmPtr->Ip;
 
  //
  // We'll wait for this flag to know when we're done. The RET
  // instruction sets it if it runs out of stack.
  //
  VmPtr->StopFlags = 0;
  while ((VmPtr->StopFlags & STOPFLAG_APP_DONE) == 0) {
    //
    // If we've found a simple debugger protocol, call it
    //
    DEBUG_CODE_BEGIN ();
    if (EbcSimpleDebugger != NULL) {
      EbcSimpleDebugger->Debugger (EbcSimpleDebugger, VmPtr);
    }
 
    DEBUG_CODE_END ();
 
    //
    // Use the opcode bits to index into the opcode dispatch table. If the
    // function pointer is null then generate an exception.
    //
    ExecFunc = (UINTN)mVmOpcodeTable[(*VmPtr->Ip & OPCODE_M_OPCODE)].ExecuteFunction;
    if (ExecFunc == (UINTN)NULL) {
      EbcDebugSignalException (EXCEPT_EBC_INVALID_OPCODE, EXCEPTION_FLAG_FATAL, VmPtr);
      Status = EFI_UNSUPPORTED;
      goto Done;
    }
 
    EbcDebuggerHookExecuteStart (VmPtr);
 
    //
    // The EBC VM is a strongly ordered processor, so perform a fence operation before
    // and after each instruction is executed.
    //
    MemoryFence ();
 
    mVmOpcodeTable[(*VmPtr->Ip & OPCODE_M_OPCODE)].ExecuteFunction (VmPtr);
 
    MemoryFence ();
 
    EbcDebuggerHookExecuteEnd (VmPtr);
 
    //
    // If the step flag is set, signal an exception and continue. We don't
    // clear it here. Assuming the debugger is responsible for clearing it.
    //
    if (VMFLAG_ISSET (VmPtr, VMFLAGS_STEP)) {
      EbcDebugSignalException (EXCEPT_EBC_STEP, EXCEPTION_FLAG_NONE, VmPtr);
    }
 
    //
    // Make sure stack has not been corrupted. Only report it once though.
    //
    if ((StackCorrupted == 0) && (*VmPtr->StackMagicPtr != (UINTN)VM_STACK_KEY_VALUE)) {
      EbcDebugSignalException (EXCEPT_EBC_STACK_FAULT, EXCEPTION_FLAG_FATAL, VmPtr);
      StackCorrupted = 1;
    }
 
    if ((StackCorrupted == 0) && ((UINT64)VmPtr->Gpr[0] <= (UINT64)(UINTN)VmPtr->StackTop)) {
      EbcDebugSignalException (EXCEPT_EBC_STACK_FAULT, EXCEPTION_FLAG_FATAL, VmPtr);
      StackCorrupted = 1;
    }
  }
 
Done:
  mVmPtr = NULL;
 
  return Status;
}
 
EFI_STATUS
ExecuteMOVxx (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   OpcMasked;
  UINT8   Operands;
  UINT8   Size;
  UINT8   MoveSize;
  INT16   Index16;
  INT32   Index32;
  INT64   Index64Op1;
  INT64   Index64Op2;
  UINT64  Data64;
  UINT64  DataMask;
  UINTN   Source;
 
  Opcode    = GETOPCODE (VmPtr);
  OpcMasked = (UINT8)(Opcode & OPCODE_M_OPCODE);
 
  //
  // Get the operands byte so we can get R1 and R2
  //
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Assume no indexes
  //
  Index64Op1 = 0;
  Index64Op2 = 0;
  Data64     = 0;
 
  //
  // Determine if we have an index/immediate data. Base instruction size
  // is 2 (opcode + operands). Add to this size each index specified.
  //
  Size = 2;
  if ((Opcode & (OPCODE_M_IMMED_OP1 | OPCODE_M_IMMED_OP2)) != 0) {
    //
    // Determine size of the index from the opcode. Then get it.
    //
    if ((OpcMasked <= OPCODE_MOVQW) || (OpcMasked == OPCODE_MOVNW)) {
      //
      // MOVBW, MOVWW, MOVDW, MOVQW, and MOVNW have 16-bit immediate index.
      // Get one or both index values.
      //
      if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
        Index16    = VmReadIndex16 (VmPtr, 2);
        Index64Op1 = (INT64)Index16;
        Size      += sizeof (UINT16);
      }
 
      if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
        Index16    = VmReadIndex16 (VmPtr, Size);
        Index64Op2 = (INT64)Index16;
        Size      += sizeof (UINT16);
      }
    } else if ((OpcMasked <= OPCODE_MOVQD) || (OpcMasked == OPCODE_MOVND)) {
      //
      // MOVBD, MOVWD, MOVDD, MOVQD, and MOVND have 32-bit immediate index
      //
      if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
        Index32    = VmReadIndex32 (VmPtr, 2);
        Index64Op1 = (INT64)Index32;
        Size      += sizeof (UINT32);
      }
 
      if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
        Index32    = VmReadIndex32 (VmPtr, Size);
        Index64Op2 = (INT64)Index32;
        Size      += sizeof (UINT32);
      }
    } else if (OpcMasked == OPCODE_MOVQQ) {
      //
      // MOVqq -- only form with a 64-bit index
      //
      if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
        Index64Op1 = VmReadIndex64 (VmPtr, 2);
        Size      += sizeof (UINT64);
      }
 
      if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
        Index64Op2 = VmReadIndex64 (VmPtr, Size);
        Size      += sizeof (UINT64);
      }
    } else {
      //
      // Obsolete MOVBQ, MOVWQ, MOVDQ, and MOVNQ have 64-bit immediate index
      //
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
  }
 
  //
  // Determine the size of the move, and create a mask for it so we can
  // clear unused bits.
  //
  if ((OpcMasked == OPCODE_MOVBW) || (OpcMasked == OPCODE_MOVBD)) {
    MoveSize = DATA_SIZE_8;
    DataMask = 0xFF;
  } else if ((OpcMasked == OPCODE_MOVWW) || (OpcMasked == OPCODE_MOVWD)) {
    MoveSize = DATA_SIZE_16;
    DataMask = 0xFFFF;
  } else if ((OpcMasked == OPCODE_MOVDW) || (OpcMasked == OPCODE_MOVDD)) {
    MoveSize = DATA_SIZE_32;
    DataMask = 0xFFFFFFFF;
  } else if ((OpcMasked == OPCODE_MOVQW) || (OpcMasked == OPCODE_MOVQD) || (OpcMasked == OPCODE_MOVQQ)) {
    MoveSize = DATA_SIZE_64;
    DataMask = (UINT64) ~0;
  } else if ((OpcMasked == OPCODE_MOVNW) || (OpcMasked == OPCODE_MOVND)) {
    MoveSize = DATA_SIZE_N;
    DataMask = (UINT64) ~0 >> (64 - 8 * sizeof (UINTN));
  } else {
    //
    // We were dispatched to this function and we don't recognize the opcode
    //
    EbcDebugSignalException (EXCEPT_EBC_UNDEFINED, EXCEPTION_FLAG_FATAL, VmPtr);
    return EFI_UNSUPPORTED;
  }
 
  //
  // Now get the source address
  //
  if (OPERAND2_INDIRECT (Operands)) {
    //
    // Indirect form @R2. Compute address of operand2
    //
    Source = (UINTN)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index64Op2);
    //
    // Now get the data from the source. Always 0-extend and let the compiler
    // sign-extend where required.
    //
    switch (MoveSize) {
      case DATA_SIZE_8:
        Data64 = (UINT64)(UINT8)VmReadMem8 (VmPtr, Source);
        break;
 
      case DATA_SIZE_16:
        Data64 = (UINT64)(UINT16)VmReadMem16 (VmPtr, Source);
        break;
 
      case DATA_SIZE_32:
        Data64 = (UINT64)(UINT32)VmReadMem32 (VmPtr, Source);
        break;
 
      case DATA_SIZE_64:
        Data64 = (UINT64)VmReadMem64 (VmPtr, Source);
        break;
 
      case DATA_SIZE_N:
        Data64 = (UINT64)(UINTN)VmReadMemN (VmPtr, Source);
        break;
 
      default:
        //
        // not reached
        //
        break;
    }
  } else {
    //
    // Not indirect source: MOVxx {@}Rx, Ry [Index]
    //
    Data64 = (UINT64)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index64Op2);
    //
    // Did Operand2 have an index? If so, treat as two signed values since
    // indexes are signed values.
    //
    if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
      //
      // NOTE: need to find a way to fix this, most likely by changing the VM
      // implementation to remove the stack gap. To do that, we'd need to
      // allocate stack space for the VM and actually set the system
      // stack pointer to the allocated buffer when the VM starts.
      //
      // Special case -- if someone took the address of a function parameter
      // then we need to make sure it's not in the stack gap. We can identify
      // this situation if (Operand2 register == 0) && (Operand2 is direct)
      // && (Index applies to Operand2) && (Index > 0) && (Operand1 register != 0)
      // Situations that to be aware of:
      //   * stack adjustments at beginning and end of functions R0 = R0 += stacksize
      //
      if ((OPERAND2_REGNUM (Operands) == 0) &&
          (!OPERAND2_INDIRECT (Operands)) &&
          (Index64Op2 > 0) &&
          (OPERAND1_REGNUM (Operands) == 0) &&
          (OPERAND1_INDIRECT (Operands))
          )
      {
        Data64 = (UINT64)ConvertStackAddr (VmPtr, (UINTN)(INT64)Data64);
      }
    }
  }
 
  //
  // Now write it back
  //
  if (OPERAND1_INDIRECT (Operands)) {
    //
    // Reuse the Source variable to now be dest.
    //
    Source = (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index64Op1);
    //
    // Do the write based on the size
    //
    switch (MoveSize) {
      case DATA_SIZE_8:
        VmWriteMem8 (VmPtr, Source, (UINT8)Data64);
        break;
 
      case DATA_SIZE_16:
        VmWriteMem16 (VmPtr, Source, (UINT16)Data64);
        break;
 
      case DATA_SIZE_32:
        VmWriteMem32 (VmPtr, Source, (UINT32)Data64);
        break;
 
      case DATA_SIZE_64:
        VmWriteMem64 (VmPtr, Source, Data64);
        break;
 
      case DATA_SIZE_N:
        VmWriteMemN (VmPtr, Source, (UINTN)Data64);
        break;
 
      default:
        //
        // not reached
        //
        break;
    }
  } else {
    //
    // Operand1 direct.
    // Make sure we didn't have an index on operand1.
    //
    if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    //
    // Direct storage in register. Clear unused bits and store back to
    // register.
    //
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = Data64 & DataMask;
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteBREAK (
  IN VM_CONTEXT  *VmPtr
  )
{
  EFI_STATUS  Status;
  UINT8       Operands;
  VOID        *EbcEntryPoint;
  VOID        *Thunk;
  UINT64      U64EbcEntryPoint;
  INT32       Offset;
 
  Thunk    = NULL;
  Operands = GETOPERANDS (VmPtr);
  switch (Operands) {
    //
    // Runaway program break. Generate an exception and terminate
    //
    case 0:
      EbcDebugSignalException (EXCEPT_EBC_BAD_BREAK, EXCEPTION_FLAG_FATAL, VmPtr);
      break;
 
    //
    // Get VM version -- return VM revision number in R7
    //
    case 1:
      //
      // Bits:
      //  63-17 = 0
      //  16-8  = Major version
      //  7-0   = Minor version
      //
      VmPtr->Gpr[7] = GetVmVersion ();
      break;
 
    //
    // Debugger breakpoint
    //
    case 3:
      VmPtr->StopFlags |= STOPFLAG_BREAKPOINT;
      //
      // See if someone has registered a handler
      //
      EbcDebugSignalException (
        EXCEPT_EBC_BREAKPOINT,
        EXCEPTION_FLAG_NONE,
        VmPtr
        );
      break;
 
    //
    // System call, which there are none, so NOP it.
    //
    case 4:
      break;
 
    //
    // Create a thunk for EBC code. R7 points to a 32-bit (in a 64-bit slot)
    // "offset from self" pointer to the EBC entry point.
    // After we're done, *(UINT64 *)R7 will be the address of the new thunk.
    //
    case 5:
      Offset           = (INT32)VmReadMem32 (VmPtr, (UINTN)VmPtr->Gpr[7]);
      U64EbcEntryPoint = (UINT64)(VmPtr->Gpr[7] + Offset + 4);
      EbcEntryPoint    = (VOID *)(UINTN)U64EbcEntryPoint;
 
      //
      // Now create a new thunk
      //
      Status = EbcCreateThunks (VmPtr->ImageHandle, EbcEntryPoint, &Thunk, 0);
      if (EFI_ERROR (Status)) {
        return Status;
      }
 
      //
      // Finally replace the EBC entry point memory with the thunk address
      //
      VmWriteMem64 (VmPtr, (UINTN)VmPtr->Gpr[7], (UINT64)(UINTN)Thunk);
      break;
 
    //
    // Compiler setting version per value in R7
    //
    case 6:
      VmPtr->CompilerVersion = (UINT32)VmPtr->Gpr[7];
      //
      // Check compiler version against VM version?
      //
      break;
 
    //
    // Unhandled break code. Signal exception.
    //
    default:
      EbcDebugSignalException (EXCEPT_EBC_BAD_BREAK, EXCEPTION_FLAG_FATAL, VmPtr);
      break;
  }
 
  //
  // Advance IP
  //
  VmPtr->Ip += 2;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteJMP (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   CompareSet;
  UINT8   ConditionFlag;
  UINT8   Size;
  UINT8   Operand;
  UINT64  Data64;
  INT32   Index32;
  UINTN   Addr;
 
  Operand = GETOPERANDS (VmPtr);
  Opcode  = GETOPCODE (VmPtr);
 
  //
  // Get instruction length from the opcode. The upper two bits are used here
  // to index into the length array.
  //
  Size = mJMPLen[(Opcode >> 6) & 0x03];
 
  //
  // Decode instruction conditions
  // If we haven't met the condition, then simply advance the IP and return.
  //
  CompareSet    = (UINT8)(((Operand & JMP_M_CS) != 0) ? 1 : 0);
  ConditionFlag = (UINT8)VMFLAG_ISSET (VmPtr, VMFLAGS_CC);
  if ((Operand & CONDITION_M_CONDITIONAL) != 0) {
    if (CompareSet != ConditionFlag) {
      EbcDebuggerHookJMPStart (VmPtr);
      VmPtr->Ip += Size;
      EbcDebuggerHookJMPEnd (VmPtr);
      return EFI_SUCCESS;
    }
  }
 
  //
  // Check for 64-bit form and do it right away since it's the most
  // straight-forward form.
  //
  if ((Opcode & OPCODE_M_IMMDATA64) != 0) {
    //
    // Double check for immediate-data, which is required. If not there,
    // then signal an exception
    //
    if ((Opcode & OPCODE_M_IMMDATA) == 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_ERROR,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    //
    // 64-bit immediate data is full address. Read the immediate data,
    // check for alignment, and jump absolute.
    //
    Data64 = (UINT64)VmReadImmed64 (VmPtr, 2);
    if (!ADDRESS_IS_ALIGNED ((UINTN)Data64, sizeof (UINT16))) {
      EbcDebugSignalException (
        EXCEPT_EBC_ALIGNMENT_CHECK,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
 
      return EFI_UNSUPPORTED;
    }
 
    //
    // Take jump -- relative or absolute
    //
    EbcDebuggerHookJMPStart (VmPtr);
    if ((Operand & JMP_M_RELATIVE) != 0) {
      VmPtr->Ip += (UINTN)Data64 + Size;
    } else {
      VmPtr->Ip = (VMIP)(UINTN)Data64;
    }
 
    EbcDebuggerHookJMPEnd (VmPtr);
 
    return EFI_SUCCESS;
  }
 
  //
  // 32-bit forms:
  // Get the index if there is one. May be either an index, or an immediate
  // offset depending on indirect operand.
  //   JMP32 @R1 Index32 -- immediate data is an index
  //   JMP32 R1 Immed32  -- immedate data is an offset
  //
  if ((Opcode & OPCODE_M_IMMDATA) != 0) {
    if (OPERAND1_INDIRECT (Operand)) {
      Index32 = VmReadIndex32 (VmPtr, 2);
    } else {
      Index32 = VmReadImmed32 (VmPtr, 2);
    }
  } else {
    Index32 = 0;
  }
 
  //
  // Get the register data. If R == 0, then special case where it's ignored.
  //
  if (OPERAND1_REGNUM (Operand) == 0) {
    Data64 = 0;
  } else {
    Data64 = (UINT64)OPERAND1_REGDATA (VmPtr, Operand);
  }
 
  //
  // Decode the forms
  //
  if (OPERAND1_INDIRECT (Operand)) {
    //
    // Form: JMP32 @Rx {Index32}
    //
    Addr = VmReadMemN (VmPtr, (UINTN)Data64 + Index32);
    if (!ADDRESS_IS_ALIGNED ((UINTN)Addr, sizeof (UINT16))) {
      EbcDebugSignalException (
        EXCEPT_EBC_ALIGNMENT_CHECK,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
 
      return EFI_UNSUPPORTED;
    }
 
    EbcDebuggerHookJMPStart (VmPtr);
    if ((Operand & JMP_M_RELATIVE) != 0) {
      VmPtr->Ip += (UINTN)Addr + Size;
    } else {
      VmPtr->Ip = (VMIP)Addr;
    }
 
    EbcDebuggerHookJMPEnd (VmPtr);
  } else {
    //
    // Form: JMP32 Rx {Immed32}
    //
    Addr = (UINTN)(Data64 + Index32);
    if (!ADDRESS_IS_ALIGNED ((UINTN)Addr, sizeof (UINT16))) {
      EbcDebugSignalException (
        EXCEPT_EBC_ALIGNMENT_CHECK,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
 
      return EFI_UNSUPPORTED;
    }
 
    EbcDebuggerHookJMPStart (VmPtr);
    if ((Operand & JMP_M_RELATIVE) != 0) {
      VmPtr->Ip += (UINTN)Addr + Size;
    } else {
      VmPtr->Ip = (VMIP)Addr;
    }
 
    EbcDebuggerHookJMPEnd (VmPtr);
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteJMP8 (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Opcode;
  UINT8  ConditionFlag;
  UINT8  CompareSet;
  INT8   Offset;
 
  //
  // Decode instruction.
  //
  Opcode        = GETOPCODE (VmPtr);
  CompareSet    = (UINT8)(((Opcode & JMP_M_CS) != 0) ? 1 : 0);
  ConditionFlag = (UINT8)VMFLAG_ISSET (VmPtr, VMFLAGS_CC);
 
  //
  // If we haven't met the condition, then simply advance the IP and return
  //
  if ((Opcode & CONDITION_M_CONDITIONAL) != 0) {
    if (CompareSet != ConditionFlag) {
      EbcDebuggerHookJMP8Start (VmPtr);
      VmPtr->Ip += 2;
      EbcDebuggerHookJMP8End (VmPtr);
      return EFI_SUCCESS;
    }
  }
 
  //
  // Get the offset from the instruction stream. It's relative to the
  // following instruction, and divided by 2.
  //
  Offset = VmReadImmed8 (VmPtr, 1);
  //
  // Want to check for offset == -2 and then raise an exception?
  //
  EbcDebuggerHookJMP8Start (VmPtr);
  VmPtr->Ip += (Offset * 2) + 2;
  EbcDebuggerHookJMP8End (VmPtr);
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteMOVI (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT16   Index16;
  INT64   ImmData64;
  UINT64  Op1;
  UINT64  Mask64;
 
  //
  // Get the opcode and operands byte so we can get R1 and R2
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Get the index (16-bit) if present
  //
  if ((Operands & MOVI_M_IMMDATA) != 0) {
    Index16 = VmReadIndex16 (VmPtr, 2);
    Size    = 4;
  } else {
    Index16 = 0;
    Size    = 2;
  }
 
  //
  // Extract the immediate data. Sign-extend always.
  //
  if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH16) {
    ImmData64 = (INT64)(INT16)VmReadImmed16 (VmPtr, Size);
    Size     += 2;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH32) {
    ImmData64 = (INT64)(INT32)VmReadImmed32 (VmPtr, Size);
    Size     += 4;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH64) {
    ImmData64 = (INT64)VmReadImmed64 (VmPtr, Size);
    Size     += 8;
  } else {
    //
    // Invalid encoding
    //
    EbcDebugSignalException (
      EXCEPT_EBC_INSTRUCTION_ENCODING,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return EFI_UNSUPPORTED;
  }
 
  //
  // Now write back the result
  //
  if (!OPERAND1_INDIRECT (Operands)) {
    //
    // Operand1 direct. Make sure it didn't have an index.
    //
    if ((Operands & MOVI_M_IMMDATA) != 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    //
    // Writing directly to a register. Clear unused bits.
    //
    if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH8) {
      Mask64 = 0x000000FF;
    } else if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH16) {
      Mask64 = 0x0000FFFF;
    } else if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH32) {
      Mask64 = 0x00000000FFFFFFFF;
    } else {
      Mask64 = (UINT64) ~0;
    }
 
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = ImmData64 & Mask64;
  } else {
    //
    // Get the address then write back based on size of the move
    //
    Op1 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16;
    if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH8) {
      VmWriteMem8 (VmPtr, (UINTN)Op1, (UINT8)ImmData64);
    } else if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH16) {
      VmWriteMem16 (VmPtr, (UINTN)Op1, (UINT16)ImmData64);
    } else if ((Operands & MOVI_M_MOVEWIDTH) == MOVI_MOVEWIDTH32) {
      VmWriteMem32 (VmPtr, (UINTN)Op1, (UINT32)ImmData64);
    } else {
      VmWriteMem64 (VmPtr, (UINTN)Op1, (UINT64)ImmData64);
    }
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteMOVIn (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT16   Index16;
  INT16   ImmedIndex16;
  INT32   ImmedIndex32;
  INT64   ImmedIndex64;
  UINT64  Op1;
 
  //
  // Get the opcode and operands byte so we can get R1 and R2
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Get the operand1 index (16-bit) if present
  //
  if ((Operands & MOVI_M_IMMDATA) != 0) {
    Index16 = VmReadIndex16 (VmPtr, 2);
    Size    = 4;
  } else {
    Index16 = 0;
    Size    = 2;
  }
 
  //
  // Extract the immediate data and convert to a 64-bit index.
  //
  if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH16) {
    ImmedIndex16 = VmReadIndex16 (VmPtr, Size);
    ImmedIndex64 = (INT64)ImmedIndex16;
    Size        += 2;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH32) {
    ImmedIndex32 = VmReadIndex32 (VmPtr, Size);
    ImmedIndex64 = (INT64)ImmedIndex32;
    Size        += 4;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH64) {
    ImmedIndex64 = VmReadIndex64 (VmPtr, Size);
    Size        += 8;
  } else {
    //
    // Invalid encoding
    //
    EbcDebugSignalException (
      EXCEPT_EBC_INSTRUCTION_ENCODING,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return EFI_UNSUPPORTED;
  }
 
  //
  // Now write back the result
  //
  if (!OPERAND1_INDIRECT (Operands)) {
    //
    // Check for MOVIn R1 Index16, Immed (not indirect, with index), which
    // is illegal
    //
    if ((Operands & MOVI_M_IMMDATA) != 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = ImmedIndex64;
  } else {
    //
    // Get the address
    //
    Op1 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16;
    VmWriteMemN (VmPtr, (UINTN)Op1, (UINTN)(INTN)ImmedIndex64);
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteMOVREL (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT16   Index16;
  INT64   ImmData64;
  UINT64  Op1;
  UINT64  Op2;
 
  //
  // Get the opcode and operands byte so we can get R1 and R2
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Get the Operand 1 index (16-bit) if present
  //
  if ((Operands & MOVI_M_IMMDATA) != 0) {
    Index16 = VmReadIndex16 (VmPtr, 2);
    Size    = 4;
  } else {
    Index16 = 0;
    Size    = 2;
  }
 
  //
  // Get the immediate data.
  //
  if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH16) {
    ImmData64 = (INT64)VmReadImmed16 (VmPtr, Size);
    Size     += 2;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH32) {
    ImmData64 = (INT64)VmReadImmed32 (VmPtr, Size);
    Size     += 4;
  } else if ((Opcode & MOVI_M_DATAWIDTH) == MOVI_DATAWIDTH64) {
    ImmData64 = VmReadImmed64 (VmPtr, Size);
    Size     += 8;
  } else {
    //
    // Invalid encoding
    //
    EbcDebugSignalException (
      EXCEPT_EBC_INSTRUCTION_ENCODING,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return EFI_UNSUPPORTED;
  }
 
  //
  // Compute the value and write back the result
  //
  Op2 = (UINT64)((INT64)((UINT64)(UINTN)VmPtr->Ip) + (INT64)ImmData64 + Size);
  if (!OPERAND1_INDIRECT (Operands)) {
    //
    // Check for illegal combination of operand1 direct with immediate data
    //
    if ((Operands & MOVI_M_IMMDATA) != 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = (VM_REGISTER)Op2;
  } else {
    //
    // Get the address = [Rx] + Index16
    // Write back the result. Always a natural size write, since
    // we're talking addresses here.
    //
    Op1 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16;
    VmWriteMemN (VmPtr, (UINTN)Op1, (UINTN)Op2);
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteMOVsnw (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT16   Op1Index;
  INT16   Op2Index;
  UINT64  Op2;
 
  //
  // Get the opcode and operand bytes
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  Op1Index = Op2Index = 0;
 
  //
  // Get the indexes if present.
  //
  Size = 2;
  if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Op1Index = VmReadIndex16 (VmPtr, 2);
    } else {
      //
      // Illegal form operand1 direct with index:  MOVsnw R1 Index16, {@}R2
      //
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    Size += sizeof (UINT16);
  }
 
  if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
    if (OPERAND2_INDIRECT (Operands)) {
      Op2Index = VmReadIndex16 (VmPtr, Size);
    } else {
      Op2Index = VmReadImmed16 (VmPtr, Size);
    }
 
    Size += sizeof (UINT16);
  }
 
  //
  // Get the data from the source.
  //
  Op2 = (UINT64)(INT64)(INTN)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Op2Index);
  if (OPERAND2_INDIRECT (Operands)) {
    Op2 = (UINT64)(INT64)(INTN)VmReadMemN (VmPtr, (UINTN)Op2);
  }
 
  //
  // Now write back the result.
  //
  if (!OPERAND1_INDIRECT (Operands)) {
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = Op2;
  } else {
    VmWriteMemN (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Op1Index), (UINTN)Op2);
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteMOVsnd (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT32   Op1Index;
  INT32   Op2Index;
  UINT64  Op2;
 
  //
  // Get the opcode and operand bytes
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  Op1Index = Op2Index = 0;
 
  //
  // Get the indexes if present.
  //
  Size = 2;
  if ((Opcode & OPCODE_M_IMMED_OP1) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Op1Index = VmReadIndex32 (VmPtr, 2);
    } else {
      //
      // Illegal form operand1 direct with index:  MOVsnd R1 Index16,..
      //
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
      return EFI_UNSUPPORTED;
    }
 
    Size += sizeof (UINT32);
  }
 
  if ((Opcode & OPCODE_M_IMMED_OP2) != 0) {
    if (OPERAND2_INDIRECT (Operands)) {
      Op2Index = VmReadIndex32 (VmPtr, Size);
    } else {
      Op2Index = VmReadImmed32 (VmPtr, Size);
    }
 
    Size += sizeof (UINT32);
  }
 
  //
  // Get the data from the source.
  //
  Op2 = (UINT64)(INT64)(INTN)(INT64)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Op2Index);
  if (OPERAND2_INDIRECT (Operands)) {
    Op2 = (UINT64)(INT64)(INTN)(INT64)VmReadMemN (VmPtr, (UINTN)Op2);
  }
 
  //
  // Now write back the result.
  //
  if (!OPERAND1_INDIRECT (Operands)) {
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = Op2;
  } else {
    VmWriteMemN (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Op1Index), (UINTN)Op2);
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecutePUSHn (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Opcode;
  UINT8  Operands;
  INT16  Index16;
  UINTN  DataN;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Get index if present
  //
  if ((Opcode & PUSHPOP_M_IMMDATA) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    VmPtr->Ip += 4;
  } else {
    Index16    = 0;
    VmPtr->Ip += 2;
  }
 
  //
  // Get the data to push
  //
  if (OPERAND1_INDIRECT (Operands)) {
    DataN = VmReadMemN (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16));
  } else {
    DataN = (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16);
  }
 
  //
  // Adjust the stack down.
  //
  VmPtr->Gpr[0] -= sizeof (UINTN);
  VmWriteMemN (VmPtr, (UINTN)VmPtr->Gpr[0], DataN);
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecutePUSH (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT32  Data32;
  UINT64  Data64;
  INT16   Index16;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
  //
  // Get immediate index if present, then advance the IP.
  //
  if ((Opcode & PUSHPOP_M_IMMDATA) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    VmPtr->Ip += 4;
  } else {
    Index16    = 0;
    VmPtr->Ip += 2;
  }
 
  //
  // Get the data to push
  //
  if ((Opcode & PUSHPOP_M_64) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Data64 = VmReadMem64 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16));
    } else {
      Data64 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16;
    }
 
    //
    // Adjust the stack down, then write back the data
    //
    VmPtr->Gpr[0] -= sizeof (UINT64);
    VmWriteMem64 (VmPtr, (UINTN)VmPtr->Gpr[0], Data64);
  } else {
    //
    // 32-bit data
    //
    if (OPERAND1_INDIRECT (Operands)) {
      Data32 = VmReadMem32 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16));
    } else {
      Data32 = (UINT32)VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16;
    }
 
    //
    // Adjust the stack down and write the data
    //
    VmPtr->Gpr[0] -= sizeof (UINT32);
    VmWriteMem32 (VmPtr, (UINTN)VmPtr->Gpr[0], Data32);
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecutePOPn (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Opcode;
  UINT8  Operands;
  INT16  Index16;
  UINTN  DataN;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
  //
  // Get immediate data if present, and advance the IP
  //
  if ((Opcode & PUSHPOP_M_IMMDATA) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    VmPtr->Ip += 4;
  } else {
    Index16    = 0;
    VmPtr->Ip += 2;
  }
 
  //
  // Read the data off the stack, then adjust the stack pointer
  //
  DataN          = VmReadMemN (VmPtr, (UINTN)VmPtr->Gpr[0]);
  VmPtr->Gpr[0] += sizeof (UINTN);
  //
  // Do the write-back
  //
  if (OPERAND1_INDIRECT (Operands)) {
    VmWriteMemN (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16), DataN);
  } else {
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = (INT64)(UINT64)(UINTN)(DataN + Index16);
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecutePOP (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  INT16   Index16;
  INT32   Data32;
  UINT64  Data64;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
  //
  // Get immediate data if present, and advance the IP.
  //
  if ((Opcode & PUSHPOP_M_IMMDATA) != 0) {
    if (OPERAND1_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    VmPtr->Ip += 4;
  } else {
    Index16    = 0;
    VmPtr->Ip += 2;
  }
 
  //
  // Get the data off the stack, then write it to the appropriate location
  //
  if ((Opcode & PUSHPOP_M_64) != 0) {
    //
    // Read the data off the stack, then adjust the stack pointer
    //
    Data64         = VmReadMem64 (VmPtr, (UINTN)VmPtr->Gpr[0]);
    VmPtr->Gpr[0] += sizeof (UINT64);
    //
    // Do the write-back
    //
    if (OPERAND1_INDIRECT (Operands)) {
      VmWriteMem64 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16), Data64);
    } else {
      VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = Data64 + Index16;
    }
  } else {
    //
    // 32-bit pop. Read it off the stack and adjust the stack pointer
    //
    Data32         = (INT32)VmReadMem32 (VmPtr, (UINTN)VmPtr->Gpr[0]);
    VmPtr->Gpr[0] += sizeof (UINT32);
    //
    // Do the write-back
    //
    if (OPERAND1_INDIRECT (Operands)) {
      VmWriteMem32 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND1_REGNUM (Operands)] + Index16), Data32);
    } else {
      VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = (INT64)Data32 + Index16;
    }
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteCALL (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Opcode;
  UINT8  Operands;
  INT32  Immed32;
  UINT8  Size;
  INT64  Immed64;
  VOID   *FramePtr;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  if ((Operands & OPERAND_M_NATIVE_CALL) != 0) {
    EbcDebuggerHookCALLEXStart (VmPtr);
  } else {
    EbcDebuggerHookCALLStart (VmPtr);
  }
 
  //
  // Assign these as well to avoid compiler warnings
  //
  Immed64 = 0;
  Immed32 = 0;
 
  FramePtr = VmPtr->FramePtr;
  //
  // Determine the instruction size, and get immediate data if present
  //
  if ((Opcode & OPCODE_M_IMMDATA) != 0) {
    if ((Opcode & OPCODE_M_IMMDATA64) != 0) {
      Immed64 = VmReadImmed64 (VmPtr, 2);
      Size    = 10;
    } else {
      //
      // If register operand is indirect, then the immediate data is an index
      //
      if (OPERAND1_INDIRECT (Operands)) {
        Immed32 = VmReadIndex32 (VmPtr, 2);
      } else {
        Immed32 = VmReadImmed32 (VmPtr, 2);
      }
 
      Size = 6;
    }
  } else {
    Size = 2;
  }
 
  //
  // If it's a call to EBC, adjust the stack pointer down 16 bytes and
  // put our return address and frame pointer on the VM stack.
  //
  if ((Operands & OPERAND_M_NATIVE_CALL) == 0) {
    VmPtr->Gpr[0] -= 8;
    VmWriteMemN (VmPtr, (UINTN)VmPtr->Gpr[0], (UINTN)FramePtr);
    VmPtr->FramePtr = (VOID *)(UINTN)VmPtr->Gpr[0];
    VmPtr->Gpr[0]  -= 8;
    VmWriteMem64 (VmPtr, (UINTN)VmPtr->Gpr[0], (UINT64)(UINTN)(VmPtr->Ip + Size));
  }
 
  //
  // If 64-bit data, then absolute jump only
  //
  if ((Opcode & OPCODE_M_IMMDATA64) != 0) {
    //
    // Native or EBC call?
    //
    if ((Operands & OPERAND_M_NATIVE_CALL) == 0) {
      VmPtr->Ip = (VMIP)(UINTN)Immed64;
    } else {
      //
      // Call external function, get the return value, and advance the IP
      //
      EbcLLCALLEX (VmPtr, (UINTN)Immed64, (UINTN)VmPtr->Gpr[0], FramePtr, Size);
    }
  } else {
    //
    // Get the register data. If operand1 == 0, then ignore register and
    // take immediate data as relative or absolute address.
    // Compiler should take care of upper bits if 32-bit machine.
    //
    if (OPERAND1_REGNUM (Operands) != 0) {
      Immed64 = (UINT64)(UINTN)VmPtr->Gpr[OPERAND1_REGNUM (Operands)];
    }
 
    //
    // Get final address
    //
    if (OPERAND1_INDIRECT (Operands)) {
      Immed64 = (INT64)(UINT64)(UINTN)VmReadMemN (VmPtr, (UINTN)(Immed64 + Immed32));
    } else {
      Immed64 += Immed32;
    }
 
    //
    // Now determine if external call, and then if relative or absolute
    //
    if ((Operands & OPERAND_M_NATIVE_CALL) == 0) {
      //
      // EBC call. Relative or absolute? If relative, then it's relative to the
      // start of the next instruction.
      //
      if ((Operands & OPERAND_M_RELATIVE_ADDR) != 0) {
        VmPtr->Ip += Immed64 + Size;
      } else {
        VmPtr->Ip = (VMIP)(UINTN)Immed64;
      }
    } else {
      //
      // Native call. Relative or absolute?
      //
      if ((Operands & OPERAND_M_RELATIVE_ADDR) != 0) {
        EbcLLCALLEX (VmPtr, (UINTN)(Immed64 + VmPtr->Ip + Size), (UINTN)VmPtr->Gpr[0], FramePtr, Size);
      } else {
        if ((VmPtr->StopFlags & STOPFLAG_BREAK_ON_CALLEX) != 0) {
          CpuBreakpoint ();
        }
 
        EbcLLCALLEX (VmPtr, (UINTN)Immed64, (UINTN)VmPtr->Gpr[0], FramePtr, Size);
      }
    }
  }
 
  if ((Operands & OPERAND_M_NATIVE_CALL) != 0) {
    EbcDebuggerHookCALLEXEnd (VmPtr);
  } else {
    EbcDebuggerHookCALLEnd (VmPtr);
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteRET (
  IN VM_CONTEXT  *VmPtr
  )
{
  EbcDebuggerHookRETStart (VmPtr);
 
  //
  // If we're at the top of the stack, then simply set the done
  // flag and return
  //
  if (VmPtr->StackRetAddr == (UINT64)VmPtr->Gpr[0]) {
    VmPtr->StopFlags |= STOPFLAG_APP_DONE;
  } else {
    //
    // Pull the return address off the VM app's stack and set the IP
    // to it
    //
    if (!ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Gpr[0], sizeof (UINT16))) {
      EbcDebugSignalException (
        EXCEPT_EBC_ALIGNMENT_CHECK,
        EXCEPTION_FLAG_FATAL,
        VmPtr
        );
    }
 
    //
    // Restore the IP and frame pointer from the stack
    //
    VmPtr->Ip       = (VMIP)(UINTN)VmReadMem64 (VmPtr, (UINTN)VmPtr->Gpr[0]);
    VmPtr->Gpr[0]  += 8;
    VmPtr->FramePtr = (VOID *)VmReadMemN (VmPtr, (UINTN)VmPtr->Gpr[0]);
    VmPtr->Gpr[0]  += 8;
  }
 
  EbcDebuggerHookRETEnd (VmPtr);
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteCMP (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT16   Index16;
  UINT32  Flag;
  INT64   Op2;
  INT64   Op1;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
  //
  // Get the register data we're going to compare to
  //
  Op1 = VmPtr->Gpr[OPERAND1_REGNUM (Operands)];
  //
  // Get immediate data
  //
  if ((Opcode & OPCODE_M_IMMDATA) != 0) {
    if (OPERAND2_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    Size = 4;
  } else {
    Index16 = 0;
    Size    = 2;
  }
 
  //
  // Now get Op2
  //
  if (OPERAND2_INDIRECT (Operands)) {
    if ((Opcode & OPCODE_M_64BIT) != 0) {
      Op2 = (INT64)VmReadMem64 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index16));
    } else {
      //
      // 32-bit operations. 0-extend the values for all cases.
      //
      Op2 = (INT64)(UINT64)((UINT32)VmReadMem32 (VmPtr, (UINTN)(VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index16)));
    }
  } else {
    Op2 = VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index16;
  }
 
  //
  // Now do the compare
  //
  Flag = 0;
  if ((Opcode & OPCODE_M_64BIT) != 0) {
    //
    // 64-bit compares
    //
    switch (Opcode & OPCODE_M_OPCODE) {
      case OPCODE_CMPEQ:
        if (Op1 == Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPLTE:
        if (Op1 <= Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPGTE:
        if (Op1 >= Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPULTE:
        if ((UINT64)Op1 <= (UINT64)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPUGTE:
        if ((UINT64)Op1 >= (UINT64)Op2) {
          Flag = 1;
        }
 
        break;
 
      default:
        ASSERT (0);
    }
  } else {
    //
    // 32-bit compares
    //
    switch (Opcode & OPCODE_M_OPCODE) {
      case OPCODE_CMPEQ:
        if ((INT32)Op1 == (INT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPLTE:
        if ((INT32)Op1 <= (INT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPGTE:
        if ((INT32)Op1 >= (INT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPULTE:
        if ((UINT32)Op1 <= (UINT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPUGTE:
        if ((UINT32)Op1 >= (UINT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      default:
        ASSERT (0);
    }
  }
 
  //
  // Now set the flag accordingly for the comparison
  //
  if (Flag != 0) {
    VMFLAG_SET (VmPtr, VMFLAGS_CC);
  } else {
    VMFLAG_CLEAR (VmPtr, (UINT64)VMFLAGS_CC);
  }
 
  //
  // Advance the IP
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteCMPI (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8   Opcode;
  UINT8   Operands;
  UINT8   Size;
  INT64   Op1;
  INT64   Op2;
  INT16   Index16;
  UINT32  Flag;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Get operand1 index if present
  //
  Size = 2;
  if ((Operands & OPERAND_M_CMPI_INDEX) != 0) {
    Index16 = VmReadIndex16 (VmPtr, 2);
    Size   += 2;
  } else {
    Index16 = 0;
  }
 
  //
  // Get operand1 data we're going to compare to
  //
  Op1 = (INT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)];
  if (OPERAND1_INDIRECT (Operands)) {
    //
    // Indirect operand1. Fetch 32 or 64-bit value based on compare size.
    //
    if ((Opcode & OPCODE_M_CMPI64) != 0) {
      Op1 = (INT64)VmReadMem64 (VmPtr, (UINTN)Op1 + Index16);
    } else {
      Op1 = (INT64)VmReadMem32 (VmPtr, (UINTN)Op1 + Index16);
    }
  } else {
    //
    // Better not have been an index with direct. That is, CMPI R1 Index,...
    // is illegal.
    //
    if ((Operands & OPERAND_M_CMPI_INDEX) != 0) {
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_ERROR,
        VmPtr
        );
      VmPtr->Ip += Size;
      return EFI_UNSUPPORTED;
    }
  }
 
  //
  // Get immediate data -- 16- or 32-bit sign extended
  //
  if ((Opcode & OPCODE_M_CMPI32_DATA) != 0) {
    Op2   = (INT64)VmReadImmed32 (VmPtr, Size);
    Size += 4;
  } else {
    //
    // 16-bit immediate data. Sign extend always.
    //
    Op2   = (INT64)((INT16)VmReadImmed16 (VmPtr, Size));
    Size += 2;
  }
 
  //
  // Now do the compare
  //
  Flag = 0;
  if ((Opcode & OPCODE_M_CMPI64) != 0) {
    //
    // 64 bit comparison
    //
    switch (Opcode & OPCODE_M_OPCODE) {
      case OPCODE_CMPIEQ:
        if (Op1 == (INT64)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPILTE:
        if (Op1 <= (INT64)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIGTE:
        if (Op1 >= (INT64)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIULTE:
        if ((UINT64)Op1 <= (UINT64)((UINT32)Op2)) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIUGTE:
        if ((UINT64)Op1 >= (UINT64)((UINT32)Op2)) {
          Flag = 1;
        }
 
        break;
 
      default:
        ASSERT (0);
    }
  } else {
    //
    // 32-bit comparisons
    //
    switch (Opcode & OPCODE_M_OPCODE) {
      case OPCODE_CMPIEQ:
        if ((INT32)Op1 == Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPILTE:
        if ((INT32)Op1 <= Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIGTE:
        if ((INT32)Op1 >= Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIULTE:
        if ((UINT32)Op1 <= (UINT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      case OPCODE_CMPIUGTE:
        if ((UINT32)Op1 >= (UINT32)Op2) {
          Flag = 1;
        }
 
        break;
 
      default:
        ASSERT (0);
    }
  }
 
  //
  // Now set the flag accordingly for the comparison
  //
  if (Flag != 0) {
    VMFLAG_SET (VmPtr, VMFLAGS_CC);
  } else {
    VMFLAG_CLEAR (VmPtr, (UINT64)VMFLAGS_CC);
  }
 
  //
  // Advance the IP
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
UINT64
ExecuteNOT (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return ~Op2;
}
 
UINT64
ExecuteNEG (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return ~Op2 + 1;
}
 
UINT64
ExecuteADD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return Op1 + Op2;
}
 
UINT64
ExecuteSUB (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return (UINT64)((INT64)((INT64)Op1 - (INT64)Op2));
  } else {
    return (UINT64)((INT64)((INT32)((INT32)Op1 - (INT32)Op2)));
  }
}
 
UINT64
ExecuteMUL (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return MultS64x64 ((INT64)Op1, (INT64)Op2);
  } else {
    return (UINT64)((INT64)((INT32)((INT32)Op1 * (INT32)Op2)));
  }
}
 
UINT64
ExecuteMULU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return MultU64x64 (Op1, Op2);
  } else {
    return (UINT64)((UINT32)((UINT32)Op1 * (UINT32)Op2));
  }
}
 
UINT64
ExecuteDIV (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  INT64  Remainder;
 
  //
  // Check for divide-by-0
  //
  if (Op2 == 0) {
    EbcDebugSignalException (
      EXCEPT_EBC_DIVIDE_ERROR,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
 
    return 0;
  } else {
    if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
      return (UINT64)(DivS64x64Remainder (Op1, Op2, &Remainder));
    } else {
      return (UINT64)((INT64)((INT32)Op1 / (INT32)Op2));
    }
  }
}
 
UINT64
ExecuteDIVU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  UINT64  Remainder;
 
  //
  // Check for divide-by-0
  //
  if (Op2 == 0) {
    EbcDebugSignalException (
      EXCEPT_EBC_DIVIDE_ERROR,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return 0;
  } else {
    //
    // Get the destination register
    //
    if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
      return (UINT64)(DivU64x64Remainder (Op1, Op2, &Remainder));
    } else {
      return (UINT64)((UINT32)Op1 / (UINT32)Op2);
    }
  }
}
 
UINT64
ExecuteMOD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  INT64  Remainder;
 
  //
  // Check for divide-by-0
  //
  if (Op2 == 0) {
    EbcDebugSignalException (
      EXCEPT_EBC_DIVIDE_ERROR,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return 0;
  } else {
    DivS64x64Remainder ((INT64)Op1, (INT64)Op2, &Remainder);
    return Remainder;
  }
}
 
UINT64
ExecuteMODU (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  UINT64  Remainder;
 
  //
  // Check for divide-by-0
  //
  if (Op2 == 0) {
    EbcDebugSignalException (
      EXCEPT_EBC_DIVIDE_ERROR,
      EXCEPTION_FLAG_FATAL,
      VmPtr
      );
    return 0;
  } else {
    DivU64x64Remainder (Op1, Op2, &Remainder);
    return Remainder;
  }
}
 
UINT64
ExecuteAND (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return Op1 & Op2;
}
 
UINT64
ExecuteOR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return Op1 | Op2;
}
 
UINT64
ExecuteXOR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  return Op1 ^ Op2;
}
 
UINT64
ExecuteSHL (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return LShiftU64 (Op1, (UINTN)Op2);
  } else {
    return (UINT64)((UINT32)((UINT32)Op1 << (UINT32)Op2));
  }
}
 
UINT64
ExecuteSHR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return RShiftU64 (Op1, (UINTN)Op2);
  } else {
    return (UINT64)((UINT32)Op1 >> (UINT32)Op2);
  }
}
 
UINT64
ExecuteASHR (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  if ((*VmPtr->Ip & DATAMANIP_M_64) != 0) {
    return ARShiftU64 (Op1, (UINTN)Op2);
  } else {
    return (UINT64)((INT64)((INT32)Op1 >> (UINT32)Op2));
  }
}
 
UINT64
ExecuteEXTNDB (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  INT8   Data8;
  INT64  Data64;
 
  //
  // Convert to byte, then return as 64-bit signed value to let compiler
  // sign-extend the value
  //
  Data8  = (INT8)Op2;
  Data64 = (INT64)Data8;
 
  return (UINT64)Data64;
}
 
UINT64
ExecuteEXTNDW (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  INT16  Data16;
  INT64  Data64;
 
  //
  // Convert to word, then return as 64-bit signed value to let compiler
  // sign-extend the value
  //
  Data16 = (INT16)Op2;
  Data64 = (INT64)Data16;
 
  return (UINT64)Data64;
}
 
//
// Execute the EBC EXTNDD instruction.
//
// Format: EXTNDD {@}Rx, {@}Ry [Index16|Immed16]
//         EXTNDD Dest, Source
//
// Operation:  Dest <- SignExtended((DWORD)Source))
//
 
UINT64
ExecuteEXTNDD (
  IN VM_CONTEXT  *VmPtr,
  IN UINT64      Op1,
  IN UINT64      Op2
  )
{
  INT32  Data32;
  INT64  Data64;
 
  //
  // Convert to 32-bit value, then return as 64-bit signed value to let compiler
  // sign-extend the value
  //
  Data32 = (INT32)Op2;
  Data64 = (INT64)Data32;
 
  return (UINT64)Data64;
}
 
EFI_STATUS
ExecuteSignedDataManip (
  IN VM_CONTEXT  *VmPtr
  )
{
  //
  // Just call the data manipulation function with a flag indicating this
  // is a signed operation.
  //
  return ExecuteDataManip (VmPtr, TRUE);
}
 
EFI_STATUS
ExecuteUnsignedDataManip (
  IN VM_CONTEXT  *VmPtr
  )
{
  //
  // Just call the data manipulation function with a flag indicating this
  // is not a signed operation.
  //
  return ExecuteDataManip (VmPtr, FALSE);
}
 
EFI_STATUS
ExecuteDataManip (
  IN VM_CONTEXT  *VmPtr,
  IN BOOLEAN     IsSignedOp
  )
{
  UINT8   Opcode;
  INT16   Index16;
  UINT8   Operands;
  UINT8   Size;
  UINT64  Op1;
  UINT64  Op2;
  INTN    DataManipDispatchTableIndex;
 
  //
  // Get opcode and operands
  //
  Opcode   = GETOPCODE (VmPtr);
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Determine if we have immediate data by the opcode
  //
  if ((Opcode & DATAMANIP_M_IMMDATA) != 0) {
    //
    // Index16 if Ry is indirect, or Immed16 if Ry direct.
    //
    if (OPERAND2_INDIRECT (Operands)) {
      Index16 = VmReadIndex16 (VmPtr, 2);
    } else {
      Index16 = VmReadImmed16 (VmPtr, 2);
    }
 
    Size = 4;
  } else {
    Index16 = 0;
    Size    = 2;
  }
 
  //
  // Now get operand2 (source). It's of format {@}R2 {Index16|Immed16}
  //
  Op2 = (UINT64)VmPtr->Gpr[OPERAND2_REGNUM (Operands)] + Index16;
  if (OPERAND2_INDIRECT (Operands)) {
    //
    // Indirect form: @R2 Index16. Fetch as 32- or 64-bit data
    //
    if ((Opcode & DATAMANIP_M_64) != 0) {
      Op2 = VmReadMem64 (VmPtr, (UINTN)Op2);
    } else {
      //
      // Read as signed value where appropriate.
      //
      if (IsSignedOp) {
        Op2 = (UINT64)(INT64)((INT32)VmReadMem32 (VmPtr, (UINTN)Op2));
      } else {
        Op2 = (UINT64)VmReadMem32 (VmPtr, (UINTN)Op2);
      }
    }
  } else {
    if ((Opcode & DATAMANIP_M_64) == 0) {
      if (IsSignedOp) {
        Op2 = (UINT64)(INT64)((INT32)Op2);
      } else {
        Op2 = (UINT64)((UINT32)Op2);
      }
    }
  }
 
  //
  // Get operand1 (destination and sometimes also an actual operand)
  // of form {@}R1
  //
  Op1 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)];
  if (OPERAND1_INDIRECT (Operands)) {
    if ((Opcode & DATAMANIP_M_64) != 0) {
      Op1 = VmReadMem64 (VmPtr, (UINTN)Op1);
    } else {
      if (IsSignedOp) {
        Op1 = (UINT64)(INT64)((INT32)VmReadMem32 (VmPtr, (UINTN)Op1));
      } else {
        Op1 = (UINT64)VmReadMem32 (VmPtr, (UINTN)Op1);
      }
    }
  } else {
    if ((Opcode & DATAMANIP_M_64) == 0) {
      if (IsSignedOp) {
        Op1 = (UINT64)(INT64)((INT32)Op1);
      } else {
        Op1 = (UINT64)((UINT32)Op1);
      }
    }
  }
 
  //
  // Dispatch to the computation function
  //
  DataManipDispatchTableIndex = (Opcode & OPCODE_M_OPCODE) - OPCODE_NOT;
  if ((DataManipDispatchTableIndex < 0) ||
      (DataManipDispatchTableIndex >= ARRAY_SIZE (mDataManipDispatchTable)))
  {
    EbcDebugSignalException (
      EXCEPT_EBC_INVALID_OPCODE,
      EXCEPTION_FLAG_ERROR,
      VmPtr
      );
    //
    // Advance and return
    //
    VmPtr->Ip += Size;
    return EFI_UNSUPPORTED;
  } else {
    Op2 = mDataManipDispatchTable[DataManipDispatchTableIndex](VmPtr, Op1, Op2);
  }
 
  //
  // Write back the result.
  //
  if (OPERAND1_INDIRECT (Operands)) {
    Op1 = (UINT64)VmPtr->Gpr[OPERAND1_REGNUM (Operands)];
    if ((Opcode & DATAMANIP_M_64) != 0) {
      VmWriteMem64 (VmPtr, (UINTN)Op1, Op2);
    } else {
      VmWriteMem32 (VmPtr, (UINTN)Op1, (UINT32)Op2);
    }
  } else {
    //
    // Storage back to a register. Write back, clearing upper bits (as per
    // the specification) if 32-bit operation.
    //
    VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = Op2;
    if ((Opcode & DATAMANIP_M_64) == 0) {
      VmPtr->Gpr[OPERAND1_REGNUM (Operands)] &= 0xFFFFFFFF;
    }
  }
 
  //
  // Advance the instruction pointer
  //
  VmPtr->Ip += Size;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteLOADSP (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Operands;
 
  //
  // Get the operands
  //
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Do the operation
  //
  switch (OPERAND1_REGNUM (Operands)) {
    //
    // Set flags
    //
    case 0:
      //
      // Spec states that this instruction will not modify reserved bits in
      // the flags register.
      //
      VmPtr->Flags = (VmPtr->Flags &~VMFLAGS_ALL_VALID) | (VmPtr->Gpr[OPERAND2_REGNUM (Operands)] & VMFLAGS_ALL_VALID);
      break;
 
    default:
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_WARNING,
        VmPtr
        );
      VmPtr->Ip += 2;
      return EFI_UNSUPPORTED;
  }
 
  VmPtr->Ip += 2;
  return EFI_SUCCESS;
}
 
EFI_STATUS
ExecuteSTORESP (
  IN VM_CONTEXT  *VmPtr
  )
{
  UINT8  Operands;
 
  //
  // Get the operands
  //
  Operands = GETOPERANDS (VmPtr);
 
  //
  // Do the operation
  //
  switch (OPERAND2_REGNUM (Operands)) {
    //
    // Get flags
    //
    case 0:
      //
      // Retrieve the value in the flags register, then clear reserved bits
      //
      VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = (UINT64)(VmPtr->Flags & VMFLAGS_ALL_VALID);
      break;
 
    //
    // Get IP -- address of following instruction
    //
    case 1:
      VmPtr->Gpr[OPERAND1_REGNUM (Operands)] = (UINT64)(UINTN)VmPtr->Ip + 2;
      break;
 
    default:
      EbcDebugSignalException (
        EXCEPT_EBC_INSTRUCTION_ENCODING,
        EXCEPTION_FLAG_WARNING,
        VmPtr
        );
      VmPtr->Ip += 2;
      return EFI_UNSUPPORTED;
      break;
  }
 
  VmPtr->Ip += 2;
  return EFI_SUCCESS;
}
 
INT16
VmReadIndex16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  )
{
  UINT16  Index;
  INT16   Offset;
  INT16   ConstUnits;
  INT16   NaturalUnits;
  INT16   NBits;
  INT16   Mask;
 
  //
  // First read the index from the code stream
  //
  Index = VmReadCode16 (VmPtr, CodeOffset);
 
  //
  // Get the mask for NaturalUnits. First get the number of bits from the index.
  //
  NBits = (INT16)((Index & 0x7000) >> 12);
 
  //
  // Scale it for 16-bit indexes
  //
  NBits *= 2;
 
  //
  // Now using the number of bits, create a mask.
  //
  Mask = (INT16)((INT16) ~0 << NBits);
 
  //
  // Now using the mask, extract NaturalUnits from the lower bits of the index.
  //
  NaturalUnits = (INT16)(Index &~Mask);
 
  //
  // Now compute ConstUnits
  //
  ConstUnits = (INT16)(((Index &~0xF000) & Mask) >> NBits);
 
  Offset = (INT16)(NaturalUnits * sizeof (UINTN) + ConstUnits);
 
  //
  // Now set the sign
  //
  if ((Index & 0x8000) != 0) {
    //
    // Do it the hard way to work around a bogus compiler warning
    //
    // Offset = -1 * Offset;
    //
    Offset = (INT16)((INT32)Offset * -1);
  }
 
  return Offset;
}
 
INT32
VmReadIndex32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  )
{
  UINT32  Index;
  INT32   Offset;
  INT32   ConstUnits;
  INT32   NaturalUnits;
  INT32   NBits;
  INT32   Mask;
 
  Index = VmReadImmed32 (VmPtr, CodeOffset);
 
  //
  // Get the mask for NaturalUnits. First get the number of bits from the index.
  //
  NBits = (Index & 0x70000000) >> 28;
 
  //
  // Scale it for 32-bit indexes
  //
  NBits *= 4;
 
  //
  // Now using the number of bits, create a mask.
  //
  Mask = (INT32) ~0 << NBits;
 
  //
  // Now using the mask, extract NaturalUnits from the lower bits of the index.
  //
  NaturalUnits = Index &~Mask;
 
  //
  // Now compute ConstUnits
  //
  ConstUnits = ((Index &~0xF0000000) & Mask) >> NBits;
 
  Offset = NaturalUnits * sizeof (UINTN) + ConstUnits;
 
  //
  // Now set the sign
  //
  if ((Index & 0x80000000) != 0) {
    Offset = Offset * -1;
  }
 
  return Offset;
}
 
INT64
VmReadIndex64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      CodeOffset
  )
{
  UINT64  Index;
  INT64   Offset;
  INT64   ConstUnits;
  INT64   NaturalUnits;
  INT64   NBits;
  INT64   Mask;
 
  Index = VmReadCode64 (VmPtr, CodeOffset);
 
  //
  // Get the mask for NaturalUnits. First get the number of bits from the index.
  //
  NBits = RShiftU64 ((Index & 0x7000000000000000ULL), 60);
 
  //
  // Scale it for 64-bit indexes (multiply by 8 by shifting left 3)
  //
  NBits = LShiftU64 ((UINT64)NBits, 3);
 
  //
  // Now using the number of bits, create a mask.
  //
  Mask = (LShiftU64 ((UINT64) ~0, (UINTN)NBits));
 
  //
  // Now using the mask, extract NaturalUnits from the lower bits of the index.
  //
  NaturalUnits = Index &~Mask;
 
  //
  // Now compute ConstUnits
  //
  ConstUnits = ARShiftU64 (((Index &~0xF000000000000000ULL) & Mask), (UINTN)NBits);
 
  Offset = MultU64x64 ((UINT64)NaturalUnits, sizeof (UINTN)) + ConstUnits;
 
  //
  // Now set the sign
  //
  if ((Index & 0x8000000000000000ULL) != 0) {
    Offset = MultS64x64 (Offset, -1);
  }
 
  return Offset;
}
 
EFI_STATUS
VmWriteMem8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT8       Data
  )
{
  //
  // Convert the address if it's in the stack gap
  //
  Addr           = ConvertStackAddr (VmPtr, Addr);
  *(UINT8 *)Addr = Data;
  return EFI_SUCCESS;
}
 
EFI_STATUS
VmWriteMem16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT16      Data
  )
{
  EFI_STATUS  Status;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
 
  //
  // Do a simple write if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT16))) {
    *(UINT16 *)Addr = Data;
  } else {
    //
    // Write as two bytes
    //
    MemoryFence ();
    if ((Status = VmWriteMem8 (VmPtr, Addr, (UINT8)Data)) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
    if ((Status = VmWriteMem8 (VmPtr, Addr + 1, (UINT8)(Data >> 8))) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VmWriteMem32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT32      Data
  )
{
  EFI_STATUS  Status;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
 
  //
  // Do a simple write if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT32))) {
    *(UINT32 *)Addr = Data;
  } else {
    //
    // Write as two words
    //
    MemoryFence ();
    if ((Status = VmWriteMem16 (VmPtr, Addr, (UINT16)Data)) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
    if ((Status = VmWriteMem16 (VmPtr, Addr + sizeof (UINT16), (UINT16)(Data >> 16))) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VmWriteMem64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINT64      Data
  )
{
  EFI_STATUS  Status;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
 
  //
  // Do a simple write if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT64))) {
    *(UINT64 *)Addr = Data;
  } else {
    //
    // Write as two 32-bit words
    //
    MemoryFence ();
    if ((Status = VmWriteMem32 (VmPtr, Addr, (UINT32)Data)) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
    if ((Status = VmWriteMem32 (VmPtr, Addr + sizeof (UINT32), (UINT32)RShiftU64 (Data, 32))) != EFI_SUCCESS) {
      return Status;
    }
 
    MemoryFence ();
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
VmWriteMemN (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr,
  IN UINTN       Data
  )
{
  EFI_STATUS  Status;
  UINTN       Index;
 
  Status = EFI_SUCCESS;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
 
  //
  // Do a simple write if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINTN))) {
    *(UINTN *)Addr = Data;
  } else {
    for (Index = 0; Index < sizeof (UINTN) / sizeof (UINT32); Index++) {
      MemoryFence ();
      Status = VmWriteMem32 (VmPtr, Addr + Index * sizeof (UINT32), (UINT32)Data);
      MemoryFence ();
      Data = (UINTN)RShiftU64 ((UINT64)Data, 32);
    }
  }
 
  return Status;
}
 
INT8
VmReadImmed8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  //
  // Simply return the data in flat memory space
  //
  return *(INT8 *)(VmPtr->Ip + Offset);
}
 
INT16
VmReadImmed16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (INT16))) {
    return *(INT16 *)(VmPtr->Ip + Offset);
  } else {
    //
    // All code word reads should be aligned
    //
    EbcDebugSignalException (
      EXCEPT_EBC_ALIGNMENT_CHECK,
      EXCEPTION_FLAG_WARNING,
      VmPtr
      );
  }
 
  //
  // Return unaligned data
  //
  return (INT16)(*(UINT8 *)(VmPtr->Ip + Offset) + (*(UINT8 *)(VmPtr->Ip + Offset + 1) << 8));
}
 
INT32
VmReadImmed32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  UINT32  Data;
 
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (UINT32))) {
    return *(INT32 *)(VmPtr->Ip + Offset);
  }
 
  //
  // Return unaligned data
  //
  Data  = (UINT32)VmReadCode16 (VmPtr, Offset);
  Data |= (UINT32)(VmReadCode16 (VmPtr, Offset + 2) << 16);
  return Data;
}
 
INT64
VmReadImmed64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  UINT64  Data64;
  UINT32  Data32;
  UINT8   *Ptr;
 
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (UINT64))) {
    return *(UINT64 *)(VmPtr->Ip + Offset);
  }
 
  //
  // Return unaligned data.
  //
  Ptr            = (UINT8 *)&Data64;
  Data32         = VmReadCode32 (VmPtr, Offset);
  *(UINT32 *)Ptr = Data32;
  Ptr           += sizeof (Data32);
  Data32         = VmReadCode32 (VmPtr, Offset + sizeof (UINT32));
  *(UINT32 *)Ptr = Data32;
  return Data64;
}
 
UINT16
VmReadCode16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (UINT16))) {
    return *(UINT16 *)(VmPtr->Ip + Offset);
  } else {
    //
    // All code word reads should be aligned
    //
    EbcDebugSignalException (
      EXCEPT_EBC_ALIGNMENT_CHECK,
      EXCEPTION_FLAG_WARNING,
      VmPtr
      );
  }
 
  //
  // Return unaligned data
  //
  return (UINT16)(*(UINT8 *)(VmPtr->Ip + Offset) + (*(UINT8 *)(VmPtr->Ip + Offset + 1) << 8));
}
 
UINT32
VmReadCode32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  UINT32  Data;
 
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (UINT32))) {
    return *(UINT32 *)(VmPtr->Ip + Offset);
  }
 
  //
  // Return unaligned data
  //
  Data  = (UINT32)VmReadCode16 (VmPtr, Offset);
  Data |= (VmReadCode16 (VmPtr, Offset + 2) << 16);
  return Data;
}
 
UINT64
VmReadCode64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINT32      Offset
  )
{
  UINT64  Data64;
  UINT32  Data32;
  UINT8   *Ptr;
 
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED ((UINTN)VmPtr->Ip + Offset, sizeof (UINT64))) {
    return *(UINT64 *)(VmPtr->Ip + Offset);
  }
 
  //
  // Return unaligned data.
  //
  Ptr            = (UINT8 *)&Data64;
  Data32         = VmReadCode32 (VmPtr, Offset);
  *(UINT32 *)Ptr = Data32;
  Ptr           += sizeof (Data32);
  Data32         = VmReadCode32 (VmPtr, Offset + sizeof (UINT32));
  *(UINT32 *)Ptr = Data32;
  return Data64;
}
 
UINT8
VmReadMem8 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
  //
  // Simply return the data in flat memory space
  //
  return *(UINT8 *)Addr;
}
 
UINT16
VmReadMem16 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT16))) {
    return *(UINT16 *)Addr;
  }
 
  //
  // Return unaligned data
  //
  return (UINT16)(*(UINT8 *)Addr + (*(UINT8 *)(Addr + 1) << 8));
}
 
UINT32
VmReadMem32 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  UINT32  Data;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT32))) {
    return *(UINT32 *)Addr;
  }
 
  //
  // Return unaligned data
  //
  Data  = (UINT32)VmReadMem16 (VmPtr, Addr);
  Data |= (VmReadMem16 (VmPtr, Addr + 2) << 16);
  return Data;
}
 
UINT64
VmReadMem64 (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  UINT64  Data;
  UINT32  Data32;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
 
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINT64))) {
    return *(UINT64 *)Addr;
  }
 
  //
  // Return unaligned data. Assume little endian.
  //
  Data32 = VmReadMem32 (VmPtr, Addr);
  Data   = (UINT64)VmReadMem32 (VmPtr, Addr + sizeof (UINT32));
  Data   = LShiftU64 (Data, 32) | Data32;
  return Data;
}
 
UINTN
ConvertStackAddr (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  ASSERT (((Addr < VmPtr->LowStackTop) || (Addr > VmPtr->HighStackBottom)));
  return Addr;
}
 
UINTN
VmReadMemN (
  IN VM_CONTEXT  *VmPtr,
  IN UINTN       Addr
  )
{
  UINTN            Data;
  volatile UINT32  Size;
  UINT8            *FromPtr;
  UINT8            *ToPtr;
 
  //
  // Convert the address if it's in the stack gap
  //
  Addr = ConvertStackAddr (VmPtr, Addr);
  //
  // Read direct if aligned
  //
  if (ADDRESS_IS_ALIGNED (Addr, sizeof (UINTN))) {
    return *(UINTN *)Addr;
  }
 
  //
  // Return unaligned data
  //
  Data    = 0;
  FromPtr = (UINT8 *)Addr;
  ToPtr   = (UINT8 *)&Data;
 
  for (Size = 0; Size < sizeof (Data); Size++) {
    *ToPtr = *FromPtr;
    ToPtr++;
    FromPtr++;
  }
 
  return Data;
}
 
UINT64
GetVmVersion (
  VOID
  )
{
  return (UINT64)(((VM_MAJOR_VERSION & 0xFFFF) << 16) | ((VM_MINOR_VERSION & 0xFFFF)));
}