Reworked REX2 handling

zyantific · Nov 8, 2024 · 9f29242 · 9f29242
1 parent 6241bfb
commit 9f29242
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Showing 3 changed files with 9,878 additions and 9,913 deletions.
diff --git a/include/Zydis/Internal/EncoderData.h b/include/Zydis/Internal/EncoderData.h
@@ -112,6 +112,25 @@ typedef enum ZydisSizeHint_
     ZYDIS_SIZE_HINT_REQUIRED_BITS = ZYAN_BITS_TO_REPRESENT(ZYDIS_SIZE_HINT_MAX_VALUE)
 } ZydisSizeHint;
 
+/**
+ * Used in encoder's table to indicate `REX2` prefix support type.
+ */
+typedef enum ZydisRex2Type_
+{
+    ZYDIS_REX2_TYPE_FORBIDDEN,
+    ZYDIS_REX2_TYPE_ALLOWED,
+    ZYDIS_REX2_TYPE_MANDATORY,
+
+    /**
+     * Maximum value of this enum.
+     */
+    ZYDIS_REX2_TYPE_MAX_VALUE = ZYDIS_REX2_TYPE_MANDATORY,
+    /**
+     * The minimum number of bits required to represent all values of this enum.
+     */
+    ZYDIS_REX2_TYPE_REQUIRED_BITS = ZYAN_BITS_TO_REPRESENT(ZYDIS_REX2_TYPE_MAX_VALUE)
+} ZydisRex2Type;
+
 /**
  * Used in encoder's primary lookup table which allows to access a set of instruction definitions
  * for specified mnemonic in constant time.
@@ -183,7 +202,7 @@ typedef struct ZydisEncodableInstruction_
     /**
      * True if `REX2` prefix is required for this definition.
      */
-    ZyanU8 rex2                     ZYAN_BITFIELD(1);
+    ZyanU8 rex2                     ZYAN_BITFIELD(ZYDIS_REX2_TYPE_REQUIRED_BITS);
     /**
      * True if `EEVEX.ND` is required for this definition.
      */

diff --git a/src/Encoder.c b/src/Encoder.c
@@ -721,59 +721,6 @@ static ZyanBool ZydisCheckAsz(ZydisEncoderInstructionMatch *match, ZydisRegister
     return match->easz == (ZyanU8)reg_width ? ZYAN_TRUE : ZYAN_FALSE;
 }
 
-/**
- * Checks if opcode is allowed to use `REX2` prefix.
- *
- * @param   match   A pointer to `ZydisEncoderInstructionMatch` struct.
- *
- * @return  True if `REX2` prefix can be used, false otherwise.
- */
-static ZyanBool ZydisIsRex2Allowed(ZydisEncoderInstructionMatch *match)
-{
-    // TODO: Remove this function, use `no_rex2` filter
-    const ZydisOpcodeMap opcode_map = match->definition->opcode_map;
-    if ((opcode_map != ZYDIS_OPCODE_MAP_DEFAULT) &&
-        (opcode_map != ZYDIS_OPCODE_MAP_0F))
-    {
-        return ZYAN_FALSE;
-    }
-    switch (match->request->mnemonic)
-    {
-    case ZYDIS_MNEMONIC_XRSTOR:
-    case ZYDIS_MNEMONIC_XRSTOR64:
-    case ZYDIS_MNEMONIC_XRSTORS:
-    case ZYDIS_MNEMONIC_XRSTORS64:
-    case ZYDIS_MNEMONIC_XSAVE:
-    case ZYDIS_MNEMONIC_XSAVE64:
-    case ZYDIS_MNEMONIC_XSAVEC:
-    case ZYDIS_MNEMONIC_XSAVEC64:
-    case ZYDIS_MNEMONIC_XSAVEOPT:
-    case ZYDIS_MNEMONIC_XSAVEOPT64:
-    case ZYDIS_MNEMONIC_XSAVES:
-    case ZYDIS_MNEMONIC_XSAVES64:
-        return ZYAN_FALSE;
-    default:
-        break;
-    }
-    static const ZyanBool is_rex2_allowed[2][16] =
-    {
-        {
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE,
-            ZYAN_FALSE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_FALSE,
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_FALSE, ZYAN_TRUE,
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_FALSE, ZYAN_TRUE,
-        },
-        {
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_FALSE,
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE,
-            ZYAN_FALSE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE,
-            ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE, ZYAN_TRUE,
-        },
-    };
-    const ZyanU8 row = (match->definition->opcode & 0xF0) >> 4;
-    return is_rex2_allowed[opcode_map][row];
-}
-
 /**
  * Returns the id of the specified register as used in physical encoding.
  *
@@ -833,7 +780,7 @@ static ZyanBool ZydisIsRegisterAllowed(ZydisEncoderInstructionMatch *match, Zydi
         case ZYDIS_REGCLASS_GPR16:
         case ZYDIS_REGCLASS_GPR32:
         case ZYDIS_REGCLASS_GPR64:
-            return ZydisIsRex2Allowed(match) ||
+            return (match->definition->rex2 != ZYDIS_REX2_TYPE_FORBIDDEN) ||
                    (ZydisGetPhysicalId(reg, reg_class) < 16);
         default:
             return reg_id < 16;
@@ -989,8 +936,7 @@ static ZyanBool ZydisIsValidAddressingClass(ZydisEncoderInstructionMatch *match,
             switch (match->definition->encoding)
             {
             case ZYDIS_INSTRUCTION_ENCODING_LEGACY:
-                result &=
-                    ZydisIsRex2Allowed(match);
+                result &= (match->definition->rex2 != ZYDIS_REX2_TYPE_FORBIDDEN);
                 break;
             case ZYDIS_INSTRUCTION_ENCODING_EVEX:
                 break;
@@ -4157,7 +4103,7 @@ static ZyanStatus ZydisBuildInstruction(ZydisEncoderInstructionMatch *match,
     {
         instruction->attributes |= ZYDIS_ATTRIB_HAS_MODRM;
     }
-    if (match->definition->rex2)
+    if (match->definition->rex2 == ZYDIS_REX2_TYPE_MANDATORY)
     {
         instruction->attributes |= ZYDIS_ATTRIB_HAS_REX2;
     }