Improved instruction decoding

- Decoding of EVEX/MVEX instructions without a NDS/NDD-operand encoded in `.vvvv` and without a VSIB-operand will now fail, if `.v'` is != 1b
- Added information about XACQUIRE, XRELEASE and BOUND prefixes to the instruction definitions
- Fixed immediate-decoding of the `vpermil2pd` / `vpermil2ps` instruction

include/Zydis/InstructionInfo.h

@@ -110,10 +110,9 @@ enum ZydisOperandEncodings
     ZYDIS_OPERAND_ENCODING_MODRM_REG,
     ZYDIS_OPERAND_ENCODING_MODRM_RM,
     ZYDIS_OPERAND_ENCODING_OPCODE,
-    ZYDIS_OPERAND_ENCODING_NDS,
+    ZYDIS_OPERAND_ENCODING_NDSNDD,
+    ZYDIS_OPERAND_ENCODING_IS4,
     ZYDIS_OPERAND_ENCODING_MASK,
-    ZYDIS_OPERAND_ENCODING_UIMM8_LO,
-    ZYDIS_OPERAND_ENCODING_UIMM8_HI,
     ZYDIS_OPERAND_ENCODING_DISP8,
     ZYDIS_OPERAND_ENCODING_DISP16,
     ZYDIS_OPERAND_ENCODING_DISP32,

include/Zydis/Internal/InstructionTable.h

@@ -648,6 +648,10 @@ enum ZydisMaskPolicies
     ZYDIS_INSTRUCTION_DEFINITION_BASE; \
     ZydisBool hasNDSNDDOperand              ZYDIS_BITFIELD( 1)
 
+#define ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR_EX \
+    ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR; \
+    ZydisBool hasVSIB                      ZYDIS_BITFIELD( 1)
+
 /**
  * @brief   Defines the @c ZydisInstructionDefinition struct.
  */
@@ -689,7 +693,7 @@ typedef struct ZydisInstructionDefinitionVEX_
 
 typedef struct ZydisInstructionDefinitionEVEX_
 {
-    ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR;
+    ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR_EX;
     ZydisInternalVectorLength vectorLength  ZYDIS_BITFIELD(2);
     ZydisEVEXTupleType tupleType            ZYDIS_BITFIELD(4);
     ZydisInternalElementSize elementSize    ZYDIS_BITFIELD(4);
@@ -700,7 +704,7 @@ typedef struct ZydisInstructionDefinitionEVEX_
 
 typedef struct ZydisInstructionDefinitionMVEX_
 {
-    ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR;
+    ZYDIS_INSTRUCTION_DEFINITION_BASE_VECTOR_EX;
     ZydisMVEXFunctionality functionality    ZYDIS_BITFIELD(5);
     ZydisMaskPolicy maskPolicy              ZYDIS_BITFIELD(2);
     ZydisBool hasElementGranularity         ZYDIS_BITFIELD(1);

src/Decoder.c

@@ -1780,7 +1780,7 @@ static ZydisStatus ZydisDecodeOperands(ZydisDecoderContext* context, ZydisInstru
                     ZydisDecodeOperandRegister(info, &info->operands[i], registerClass, 
                     ZydisCalcRegisterId(context, info, ZYDIS_REG_ENCODING_OPCODE, registerClass)));
                 break;
-            case ZYDIS_OPERAND_ENCODING_NDS:
+            case ZYDIS_OPERAND_ENCODING_NDSNDD:
                 ZYDIS_CHECK(
                     ZydisDecodeOperandRegister(info, &info->operands[i], registerClass, 
                     ZydisCalcRegisterId(context, info, ZYDIS_REG_ENCODING_NDSNDD, registerClass)));
@@ -1790,7 +1790,7 @@ static ZydisStatus ZydisDecodeOperands(ZydisDecoderContext* context, ZydisInstru
                     ZydisDecodeOperandRegister(info, &info->operands[i], registerClass, 
                     ZydisCalcRegisterId(context, info, ZYDIS_REG_ENCODING_MASK, registerClass)));
                 break;
-            case ZYDIS_OPERAND_ENCODING_UIMM8_HI:
+            case ZYDIS_OPERAND_ENCODING_IS4:
                 ZYDIS_CHECK(
                     ZydisDecodeOperandRegister(info, &info->operands[i], registerClass, 
                     ZydisCalcRegisterId(context, info, ZYDIS_REG_ENCODING_IS4, registerClass)));
@@ -1866,7 +1866,15 @@ static ZydisStatus ZydisDecodeOperands(ZydisDecoderContext* context, ZydisInstru
             ZYDIS_ASSERT((immId == 0) || (immId == 1));
             info->operands[i].type = ZYDIS_OPERAND_TYPE_IMMEDIATE;
             info->operands[i].size = operand->size[context->eoszIndex] * 8;
-            info->operands[i].imm.value.uqword = info->details.imm[immId].value.uqword;
+            if (operand->op.encoding == ZYDIS_OPERAND_ENCODING_IS4)
+            {
+                // The upper half of the 8-bit immediate is used to encode a register specifier
+                ZYDIS_ASSERT(info->details.imm[immId].dataSize == 8);
+                info->operands[i].imm.value.ubyte = info->details.imm[immId].value.ubyte & 0x0F;   
+            } else
+            {
+                info->operands[i].imm.value.uqword = info->details.imm[immId].value.uqword;
+            }
             info->operands[i].imm.isSigned = info->details.imm[immId].isSigned;
             info->operands[i].imm.isRelative = info->details.imm[immId].isRelative;
             ++immId;
@@ -4017,6 +4025,7 @@ static ZydisStatus ZydisDecodeInstruction(ZydisDecoderContext* context, ZydisIns
                 ZYDIS_CHECK(ZydisDecodeOptionalInstructionParts(context, info, optionalParts));
 
                 ZydisBool hasNDSNDDOperand = ZYDIS_FALSE;
+                ZydisBool hasVSIB = ZYDIS_FALSE;
                 ZydisMaskPolicy maskPolicy = ZYDIS_MASK_POLICY_INVALID;
                 switch (info->encoding)
                 {
@@ -4059,6 +4068,7 @@ static ZydisStatus ZydisDecodeInstruction(ZydisDecoderContext* context, ZydisIns
                     const ZydisInstructionDefinitionEVEX* def = 
                         (const ZydisInstructionDefinitionEVEX*)definition;
                     hasNDSNDDOperand = def->hasNDSNDDOperand;
+                    hasVSIB = def->hasVSIB;
                     maskPolicy = def->maskPolicy;
                     break;
                 }
@@ -4067,6 +4077,7 @@ static ZydisStatus ZydisDecodeInstruction(ZydisDecoderContext* context, ZydisIns
                     const ZydisInstructionDefinitionMVEX* def = 
                         (const ZydisInstructionDefinitionMVEX*)definition;
                     hasNDSNDDOperand = def->hasNDSNDDOperand;
+                    hasVSIB = def->hasVSIB;
                     maskPolicy = def->maskPolicy;
 
                     // Check for invalid MVEX.SSS values
@@ -4135,14 +4146,18 @@ static ZydisStatus ZydisDecodeInstruction(ZydisDecoderContext* context, ZydisIns
                     ZYDIS_UNREACHABLE;
                 }
 
-                // TODO: Add check for invalid .V`
+                // Check for invalid `XOP/VEX/EVEX/MVEX.vvvv` value
-
-                // Check for invalid XOP/VEX/EVEX/MVEX.vvvv value
                 if (!hasNDSNDDOperand && (context->cache.v_vvvv & 0x0F))
                 {
                     return ZYDIS_STATUS_DECODING_ERROR;
                 }
 
+                // Check for invalid `EVEX/MVEX.v'` value
+                if (!hasNDSNDDOperand && !hasVSIB && context->cache.V2)
+                {
+                    return ZYDIS_STATUS_DECODING_ERROR;
+                }
+
                 // Check for invalid MASK registers
                 switch (maskPolicy)
                 {