//===-- X86DisassemblerDecoder.cpp - Disassembler decoder -----------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file is part of the X86 Disassembler. // It contains the implementation of the instruction decoder. // Documentation for the disassembler can be found in X86Disassembler.h. // //===----------------------------------------------------------------------===// #include /* for va_*() */ #include /* for vsnprintf() */ #include /* for exit() */ #include /* for memset() */ #include "X86DisassemblerDecoder.h" using namespace llvm::X86Disassembler; /// Specifies whether a ModR/M byte is needed and (if so) which /// instruction each possible value of the ModR/M byte corresponds to. Once /// this information is known, we have narrowed down to a single instruction. struct ModRMDecision { uint8_t modrm_type; uint16_t instructionIDs; }; /// Specifies which set of ModR/M->instruction tables to look at /// given a particular opcode. struct OpcodeDecision { ModRMDecision modRMDecisions[256]; }; /// Specifies which opcode->instruction tables to look at given /// a particular context (set of attributes). Since there are many possible /// contexts, the decoder first uses CONTEXTS_SYM to determine which context /// applies given a specific set of attributes. Hence there are only IC_max /// entries in this table, rather than 2^(ATTR_max). struct ContextDecision { OpcodeDecision opcodeDecisions[IC_max]; }; #include "X86GenDisassemblerTables.inc" #ifndef NDEBUG #define debug(s) do { Debug(__FILE__, __LINE__, s); } while (0) #else #define debug(s) do { } while (0) #endif /* * contextForAttrs - Client for the instruction context table. Takes a set of * attributes and returns the appropriate decode context. * * @param attrMask - Attributes, from the enumeration attributeBits. * @return - The InstructionContext to use when looking up an * an instruction with these attributes. */ static InstructionContext contextForAttrs(uint16_t attrMask) { return static_cast(CONTEXTS_SYM[attrMask]); } /* * modRMRequired - Reads the appropriate instruction table to determine whether * the ModR/M byte is required to decode a particular instruction. * * @param type - The opcode type (i.e., how many bytes it has). * @param insnContext - The context for the instruction, as returned by * contextForAttrs. * @param opcode - The last byte of the instruction's opcode, not counting * ModR/M extensions and escapes. * @return - true if the ModR/M byte is required, false otherwise. */ static int modRMRequired(OpcodeType type, InstructionContext insnContext, uint16_t opcode) { const struct ContextDecision* decision = nullptr; switch (type) { case ONEBYTE: decision = &ONEBYTE_SYM; break; case TWOBYTE: decision = &TWOBYTE_SYM; break; case THREEBYTE_38: decision = &THREEBYTE38_SYM; break; case THREEBYTE_3A: decision = &THREEBYTE3A_SYM; break; case XOP8_MAP: decision = &XOP8_MAP_SYM; break; case XOP9_MAP: decision = &XOP9_MAP_SYM; break; case XOPA_MAP: decision = &XOPA_MAP_SYM; break; } return decision->opcodeDecisions[insnContext].modRMDecisions[opcode]. modrm_type != MODRM_ONEENTRY; } /* * decode - Reads the appropriate instruction table to obtain the unique ID of * an instruction. * * @param type - See modRMRequired(). * @param insnContext - See modRMRequired(). * @param opcode - See modRMRequired(). * @param modRM - The ModR/M byte if required, or any value if not. * @return - The UID of the instruction, or 0 on failure. */ static InstrUID decode(OpcodeType type, InstructionContext insnContext, uint8_t opcode, uint8_t modRM) { const struct ModRMDecision* dec = nullptr; switch (type) { case ONEBYTE: dec = &ONEBYTE_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case TWOBYTE: dec = &TWOBYTE_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case THREEBYTE_38: dec = &THREEBYTE38_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case THREEBYTE_3A: dec = &THREEBYTE3A_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case XOP8_MAP: dec = &XOP8_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case XOP9_MAP: dec = &XOP9_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; case XOPA_MAP: dec = &XOPA_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode]; break; } switch (dec->modrm_type) { default: debug("Corrupt table! Unknown modrm_type"); return 0; case MODRM_ONEENTRY: return modRMTable[dec->instructionIDs]; case MODRM_SPLITRM: if (modFromModRM(modRM) == 0x3) return modRMTable[dec->instructionIDs+1]; return modRMTable[dec->instructionIDs]; case MODRM_SPLITREG: if (modFromModRM(modRM) == 0x3) return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)+8]; return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)]; case MODRM_SPLITMISC: if (modFromModRM(modRM) == 0x3) return modRMTable[dec->instructionIDs+(modRM & 0x3f)+8]; return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)]; case MODRM_FULL: return modRMTable[dec->instructionIDs+modRM]; } } /* * specifierForUID - Given a UID, returns the name and operand specification for * that instruction. * * @param uid - The unique ID for the instruction. This should be returned by * decode(); specifierForUID will not check bounds. * @return - A pointer to the specification for that instruction. */ static const struct InstructionSpecifier *specifierForUID(InstrUID uid) { return &INSTRUCTIONS_SYM[uid]; } /* * consumeByte - Uses the reader function provided by the user to consume one * byte from the instruction's memory and advance the cursor. * * @param insn - The instruction with the reader function to use. The cursor * for this instruction is advanced. * @param byte - A pointer to a pre-allocated memory buffer to be populated * with the data read. * @return - 0 if the read was successful; nonzero otherwise. */ static int consumeByte(struct InternalInstruction* insn, uint8_t* byte) { int ret = insn->reader(insn->readerArg, byte, insn->readerCursor); if (!ret) ++(insn->readerCursor); return ret; } /* * lookAtByte - Like consumeByte, but does not advance the cursor. * * @param insn - See consumeByte(). * @param byte - See consumeByte(). * @return - See consumeByte(). */ static int lookAtByte(struct InternalInstruction* insn, uint8_t* byte) { return insn->reader(insn->readerArg, byte, insn->readerCursor); } static void unconsumeByte(struct InternalInstruction* insn) { insn->readerCursor--; } #define CONSUME_FUNC(name, type) \ static int name(struct InternalInstruction* insn, type* ptr) { \ type combined = 0; \ unsigned offset; \ for (offset = 0; offset < sizeof(type); ++offset) { \ uint8_t byte; \ int ret = insn->reader(insn->readerArg, \ &byte, \ insn->readerCursor + offset); \ if (ret) \ return ret; \ combined = combined | ((uint64_t)byte << (offset * 8)); \ } \ *ptr = combined; \ insn->readerCursor += sizeof(type); \ return 0; \ } /* * consume* - Use the reader function provided by the user to consume data * values of various sizes from the instruction's memory and advance the * cursor appropriately. These readers perform endian conversion. * * @param insn - See consumeByte(). * @param ptr - A pointer to a pre-allocated memory of appropriate size to * be populated with the data read. * @return - See consumeByte(). */ CONSUME_FUNC(consumeInt8, int8_t) CONSUME_FUNC(consumeInt16, int16_t) CONSUME_FUNC(consumeInt32, int32_t) CONSUME_FUNC(consumeUInt16, uint16_t) CONSUME_FUNC(consumeUInt32, uint32_t) CONSUME_FUNC(consumeUInt64, uint64_t) /* * dbgprintf - Uses the logging function provided by the user to log a single * message, typically without a carriage-return. * * @param insn - The instruction containing the logging function. * @param format - See printf(). * @param ... - See printf(). */ static void dbgprintf(struct InternalInstruction* insn, const char* format, ...) { char buffer[256]; va_list ap; if (!insn->dlog) return; va_start(ap, format); (void)vsnprintf(buffer, sizeof(buffer), format, ap); va_end(ap); insn->dlog(insn->dlogArg, buffer); } /* * setPrefixPresent - Marks that a particular prefix is present at a particular * location. * * @param insn - The instruction to be marked as having the prefix. * @param prefix - The prefix that is present. * @param location - The location where the prefix is located (in the address * space of the instruction's reader). */ static void setPrefixPresent(struct InternalInstruction* insn, uint8_t prefix, uint64_t location) { insn->prefixPresent[prefix] = 1; insn->prefixLocations[prefix] = location; } /* * isPrefixAtLocation - Queries an instruction to determine whether a prefix is * present at a given location. * * @param insn - The instruction to be queried. * @param prefix - The prefix. * @param location - The location to query. * @return - Whether the prefix is at that location. */ static bool isPrefixAtLocation(struct InternalInstruction* insn, uint8_t prefix, uint64_t location) { return insn->prefixPresent[prefix] == 1 && insn->prefixLocations[prefix] == location; } /* * readPrefixes - Consumes all of an instruction's prefix bytes, and marks the * instruction as having them. Also sets the instruction's default operand, * address, and other relevant data sizes to report operands correctly. * * @param insn - The instruction whose prefixes are to be read. * @return - 0 if the instruction could be read until the end of the prefix * bytes, and no prefixes conflicted; nonzero otherwise. */ static int readPrefixes(struct InternalInstruction* insn) { bool isPrefix = true; bool prefixGroups[4] = { false }; uint64_t prefixLocation; uint8_t byte = 0; uint8_t nextByte; bool hasAdSize = false; bool hasOpSize = false; dbgprintf(insn, "readPrefixes()"); while (isPrefix) { prefixLocation = insn->readerCursor; /* If we fail reading prefixes, just stop here and let the opcode reader deal with it */ if (consumeByte(insn, &byte)) break; /* * If the byte is a LOCK/REP/REPNE prefix and not a part of the opcode, then * break and let it be disassembled as a normal "instruction". */ if (insn->readerCursor - 1 == insn->startLocation && byte == 0xf0) break; if (insn->readerCursor - 1 == insn->startLocation && (byte == 0xf2 || byte == 0xf3) && !lookAtByte(insn, &nextByte)) { /* * If the byte is 0xf2 or 0xf3, and any of the following conditions are * met: * - it is followed by a LOCK (0xf0) prefix * - it is followed by an xchg instruction * then it should be disassembled as a xacquire/xrelease not repne/rep. */ if ((byte == 0xf2 || byte == 0xf3) && ((nextByte == 0xf0) || ((nextByte & 0xfe) == 0x86 || (nextByte & 0xf8) == 0x90))) insn->xAcquireRelease = true; /* * Also if the byte is 0xf3, and the following condition is met: * - it is followed by a "mov mem, reg" (opcode 0x88/0x89) or * "mov mem, imm" (opcode 0xc6/0xc7) instructions. * then it should be disassembled as an xrelease not rep. */ if (byte == 0xf3 && (nextByte == 0x88 || nextByte == 0x89 || nextByte == 0xc6 || nextByte == 0xc7)) insn->xAcquireRelease = true; if (insn->mode == MODE_64BIT && (nextByte & 0xf0) == 0x40) { if (consumeByte(insn, &nextByte)) return -1; if (lookAtByte(insn, &nextByte)) return -1; unconsumeByte(insn); } if (nextByte != 0x0f && nextByte != 0x90) break; } switch (byte) { case 0xf0: /* LOCK */ case 0xf2: /* REPNE/REPNZ */ case 0xf3: /* REP or REPE/REPZ */ if (prefixGroups[0]) dbgprintf(insn, "Redundant Group 1 prefix"); prefixGroups[0] = true; setPrefixPresent(insn, byte, prefixLocation); break; case 0x2e: /* CS segment override -OR- Branch not taken */ case 0x36: /* SS segment override -OR- Branch taken */ case 0x3e: /* DS segment override */ case 0x26: /* ES segment override */ case 0x64: /* FS segment override */ case 0x65: /* GS segment override */ switch (byte) { case 0x2e: insn->segmentOverride = SEG_OVERRIDE_CS; break; case 0x36: insn->segmentOverride = SEG_OVERRIDE_SS; break; case 0x3e: insn->segmentOverride = SEG_OVERRIDE_DS; break; case 0x26: insn->segmentOverride = SEG_OVERRIDE_ES; break; case 0x64: insn->segmentOverride = SEG_OVERRIDE_FS; break; case 0x65: insn->segmentOverride = SEG_OVERRIDE_GS; break; default: debug("Unhandled override"); return -1; } if (prefixGroups[1]) dbgprintf(insn, "Redundant Group 2 prefix"); prefixGroups[1] = true; setPrefixPresent(insn, byte, prefixLocation); break; case 0x66: /* Operand-size override */ if (prefixGroups[2]) dbgprintf(insn, "Redundant Group 3 prefix"); prefixGroups[2] = true; hasOpSize = true; setPrefixPresent(insn, byte, prefixLocation); break; case 0x67: /* Address-size override */ if (prefixGroups[3]) dbgprintf(insn, "Redundant Group 4 prefix"); prefixGroups[3] = true; hasAdSize = true; setPrefixPresent(insn, byte, prefixLocation); break; default: /* Not a prefix byte */ isPrefix = false; break; } if (isPrefix) dbgprintf(insn, "Found prefix 0x%hhx", byte); } insn->vectorExtensionType = TYPE_NO_VEX_XOP; if (byte == 0x62) { uint8_t byte1, byte2; if (consumeByte(insn, &byte1)) { dbgprintf(insn, "Couldn't read second byte of EVEX prefix"); return -1; } if (lookAtByte(insn, &byte2)) { dbgprintf(insn, "Couldn't read third byte of EVEX prefix"); return -1; } if ((insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0) && ((~byte1 & 0xc) == 0xc) && ((byte2 & 0x4) == 0x4)) { insn->vectorExtensionType = TYPE_EVEX; } else { unconsumeByte(insn); /* unconsume byte1 */ unconsumeByte(insn); /* unconsume byte */ insn->necessaryPrefixLocation = insn->readerCursor - 2; } if (insn->vectorExtensionType == TYPE_EVEX) { insn->vectorExtensionPrefix[0] = byte; insn->vectorExtensionPrefix[1] = byte1; if (consumeByte(insn, &insn->vectorExtensionPrefix[2])) { dbgprintf(insn, "Couldn't read third byte of EVEX prefix"); return -1; } if (consumeByte(insn, &insn->vectorExtensionPrefix[3])) { dbgprintf(insn, "Couldn't read fourth byte of EVEX prefix"); return -1; } /* We simulate the REX prefix for simplicity's sake */ if (insn->mode == MODE_64BIT) { insn->rexPrefix = 0x40 | (wFromEVEX3of4(insn->vectorExtensionPrefix[2]) << 3) | (rFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 2) | (xFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 1) | (bFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 0); } dbgprintf(insn, "Found EVEX prefix 0x%hhx 0x%hhx 0x%hhx 0x%hhx", insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1], insn->vectorExtensionPrefix[2], insn->vectorExtensionPrefix[3]); } } else if (byte == 0xc4) { uint8_t byte1; if (lookAtByte(insn, &byte1)) { dbgprintf(insn, "Couldn't read second byte of VEX"); return -1; } if (insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0) { insn->vectorExtensionType = TYPE_VEX_3B; insn->necessaryPrefixLocation = insn->readerCursor - 1; } else { unconsumeByte(insn); insn->necessaryPrefixLocation = insn->readerCursor - 1; } if (insn->vectorExtensionType == TYPE_VEX_3B) { insn->vectorExtensionPrefix[0] = byte; consumeByte(insn, &insn->vectorExtensionPrefix[1]); consumeByte(insn, &insn->vectorExtensionPrefix[2]); /* We simulate the REX prefix for simplicity's sake */ if (insn->mode == MODE_64BIT) { insn->rexPrefix = 0x40 | (wFromVEX3of3(insn->vectorExtensionPrefix[2]) << 3) | (rFromVEX2of3(insn->vectorExtensionPrefix[1]) << 2) | (xFromVEX2of3(insn->vectorExtensionPrefix[1]) << 1) | (bFromVEX2of3(insn->vectorExtensionPrefix[1]) << 0); } dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx 0x%hhx", insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1], insn->vectorExtensionPrefix[2]); } } else if (byte == 0xc5) { uint8_t byte1; if (lookAtByte(insn, &byte1)) { dbgprintf(insn, "Couldn't read second byte of VEX"); return -1; } if (insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0) { insn->vectorExtensionType = TYPE_VEX_2B; } else { unconsumeByte(insn); } if (insn->vectorExtensionType == TYPE_VEX_2B) { insn->vectorExtensionPrefix[0] = byte; consumeByte(insn, &insn->vectorExtensionPrefix[1]); if (insn->mode == MODE_64BIT) { insn->rexPrefix = 0x40 | (rFromVEX2of2(insn->vectorExtensionPrefix[1]) << 2); } switch (ppFromVEX2of2(insn->vectorExtensionPrefix[1])) { default: break; case VEX_PREFIX_66: hasOpSize = true; break; } dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx", insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1]); } } else if (byte == 0x8f) { uint8_t byte1; if (lookAtByte(insn, &byte1)) { dbgprintf(insn, "Couldn't read second byte of XOP"); return -1; } if ((byte1 & 0x38) != 0x0) { /* 0 in these 3 bits is a POP instruction. */ insn->vectorExtensionType = TYPE_XOP; insn->necessaryPrefixLocation = insn->readerCursor - 1; } else { unconsumeByte(insn); insn->necessaryPrefixLocation = insn->readerCursor - 1; } if (insn->vectorExtensionType == TYPE_XOP) { insn->vectorExtensionPrefix[0] = byte; consumeByte(insn, &insn->vectorExtensionPrefix[1]); consumeByte(insn, &insn->vectorExtensionPrefix[2]); /* We simulate the REX prefix for simplicity's sake */ if (insn->mode == MODE_64BIT) { insn->rexPrefix = 0x40 | (wFromXOP3of3(insn->vectorExtensionPrefix[2]) << 3) | (rFromXOP2of3(insn->vectorExtensionPrefix[1]) << 2) | (xFromXOP2of3(insn->vectorExtensionPrefix[1]) << 1) | (bFromXOP2of3(insn->vectorExtensionPrefix[1]) << 0); } switch (ppFromXOP3of3(insn->vectorExtensionPrefix[2])) { default: break; case VEX_PREFIX_66: hasOpSize = true; break; } dbgprintf(insn, "Found XOP prefix 0x%hhx 0x%hhx 0x%hhx", insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1], insn->vectorExtensionPrefix[2]); } } else { if (insn->mode == MODE_64BIT) { if ((byte & 0xf0) == 0x40) { uint8_t opcodeByte; if (lookAtByte(insn, &opcodeByte) || ((opcodeByte & 0xf0) == 0x40)) { dbgprintf(insn, "Redundant REX prefix"); return -1; } insn->rexPrefix = byte; insn->necessaryPrefixLocation = insn->readerCursor - 2; dbgprintf(insn, "Found REX prefix 0x%hhx", byte); } else { unconsumeByte(insn); insn->necessaryPrefixLocation = insn->readerCursor - 1; } } else { unconsumeByte(insn); insn->necessaryPrefixLocation = insn->readerCursor - 1; } } if (insn->mode == MODE_16BIT) { insn->registerSize = (hasOpSize ? 4 : 2); insn->addressSize = (hasAdSize ? 4 : 2); insn->displacementSize = (hasAdSize ? 4 : 2); insn->immediateSize = (hasOpSize ? 4 : 2); } else if (insn->mode == MODE_32BIT) { insn->registerSize = (hasOpSize ? 2 : 4); insn->addressSize = (hasAdSize ? 2 : 4); insn->displacementSize = (hasAdSize ? 2 : 4); insn->immediateSize = (hasOpSize ? 2 : 4); } else if (insn->mode == MODE_64BIT) { if (insn->rexPrefix && wFromREX(insn->rexPrefix)) { insn->registerSize = 8; insn->addressSize = (hasAdSize ? 4 : 8); insn->displacementSize = 4; insn->immediateSize = 4; } else if (insn->rexPrefix) { insn->registerSize = (hasOpSize ? 2 : 4); insn->addressSize = (hasAdSize ? 4 : 8); insn->displacementSize = (hasOpSize ? 2 : 4); insn->immediateSize = (hasOpSize ? 2 : 4); } else { insn->registerSize = (hasOpSize ? 2 : 4); insn->addressSize = (hasAdSize ? 4 : 8); insn->displacementSize = (hasOpSize ? 2 : 4); insn->immediateSize = (hasOpSize ? 2 : 4); } } return 0; } /* * readOpcode - Reads the opcode (excepting the ModR/M byte in the case of * extended or escape opcodes). * * @param insn - The instruction whose opcode is to be read. * @return - 0 if the opcode could be read successfully; nonzero otherwise. */ static int readOpcode(struct InternalInstruction* insn) { /* Determine the length of the primary opcode */ uint8_t current; dbgprintf(insn, "readOpcode()"); insn->opcodeType = ONEBYTE; if (insn->vectorExtensionType == TYPE_EVEX) { switch (mmFromEVEX2of4(insn->vectorExtensionPrefix[1])) { default: dbgprintf(insn, "Unhandled mm field for instruction (0x%hhx)", mmFromEVEX2of4(insn->vectorExtensionPrefix[1])); return -1; case VEX_LOB_0F: insn->opcodeType = TWOBYTE; return consumeByte(insn, &insn->opcode); case VEX_LOB_0F38: insn->opcodeType = THREEBYTE_38; return consumeByte(insn, &insn->opcode); case VEX_LOB_0F3A: insn->opcodeType = THREEBYTE_3A; return consumeByte(insn, &insn->opcode); } } else if (insn->vectorExtensionType == TYPE_VEX_3B) { switch (mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1])) { default: dbgprintf(insn, "Unhandled m-mmmm field for instruction (0x%hhx)", mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1])); return -1; case VEX_LOB_0F: insn->opcodeType = TWOBYTE; return consumeByte(insn, &insn->opcode); case VEX_LOB_0F38: insn->opcodeType = THREEBYTE_38; return consumeByte(insn, &insn->opcode); case VEX_LOB_0F3A: insn->opcodeType = THREEBYTE_3A; return consumeByte(insn, &insn->opcode); } } else if (insn->vectorExtensionType == TYPE_VEX_2B) { insn->opcodeType = TWOBYTE; return consumeByte(insn, &insn->opcode); } else if (insn->vectorExtensionType == TYPE_XOP) { switch (mmmmmFromXOP2of3(insn->vectorExtensionPrefix[1])) { default: dbgprintf(insn, "Unhandled m-mmmm field for instruction (0x%hhx)", mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1])); return -1; case XOP_MAP_SELECT_8: insn->opcodeType = XOP8_MAP; return consumeByte(insn, &insn->opcode); case XOP_MAP_SELECT_9: insn->opcodeType = XOP9_MAP; return consumeByte(insn, &insn->opcode); case XOP_MAP_SELECT_A: insn->opcodeType = XOPA_MAP; return consumeByte(insn, &insn->opcode); } } if (consumeByte(insn, ¤t)) return -1; if (current == 0x0f) { dbgprintf(insn, "Found a two-byte escape prefix (0x%hhx)", current); if (consumeByte(insn, ¤t)) return -1; if (current == 0x38) { dbgprintf(insn, "Found a three-byte escape prefix (0x%hhx)", current); if (consumeByte(insn, ¤t)) return -1; insn->opcodeType = THREEBYTE_38; } else if (current == 0x3a) { dbgprintf(insn, "Found a three-byte escape prefix (0x%hhx)", current); if (consumeByte(insn, ¤t)) return -1; insn->opcodeType = THREEBYTE_3A; } else { dbgprintf(insn, "Didn't find a three-byte escape prefix"); insn->opcodeType = TWOBYTE; } } /* * At this point we have consumed the full opcode. * Anything we consume from here on must be unconsumed. */ insn->opcode = current; return 0; } static int readModRM(struct InternalInstruction* insn); /* * getIDWithAttrMask - Determines the ID of an instruction, consuming * the ModR/M byte as appropriate for extended and escape opcodes, * and using a supplied attribute mask. * * @param instructionID - A pointer whose target is filled in with the ID of the * instruction. * @param insn - The instruction whose ID is to be determined. * @param attrMask - The attribute mask to search. * @return - 0 if the ModR/M could be read when needed or was not * needed; nonzero otherwise. */ static int getIDWithAttrMask(uint16_t* instructionID, struct InternalInstruction* insn, uint16_t attrMask) { bool hasModRMExtension; InstructionContext instructionClass = contextForAttrs(attrMask); hasModRMExtension = modRMRequired(insn->opcodeType, instructionClass, insn->opcode); if (hasModRMExtension) { if (readModRM(insn)) return -1; *instructionID = decode(insn->opcodeType, instructionClass, insn->opcode, insn->modRM); } else { *instructionID = decode(insn->opcodeType, instructionClass, insn->opcode, 0); } return 0; } /* * is16BitEquivalent - Determines whether two instruction names refer to * equivalent instructions but one is 16-bit whereas the other is not. * * @param orig - The instruction that is not 16-bit * @param equiv - The instruction that is 16-bit */ static bool is16BitEquivalent(const char* orig, const char* equiv) { off_t i; for (i = 0;; i++) { if (orig[i] == '\0' && equiv[i] == '\0') return true; if (orig[i] == '\0' || equiv[i] == '\0') return false; if (orig[i] != equiv[i]) { if ((orig[i] == 'Q' || orig[i] == 'L') && equiv[i] == 'W') continue; if ((orig[i] == '6' || orig[i] == '3') && equiv[i] == '1') continue; if ((orig[i] == '4' || orig[i] == '2') && equiv[i] == '6') continue; return false; } } } /* * is64Bit - Determines whether this instruction is a 64-bit instruction. * * @param name - The instruction that is not 16-bit */ static bool is64Bit(const char* name) { off_t i; for (i = 0;; ++i) { if (name[i] == '\0') return false; if (name[i] == '6' && name[i+1] == '4') return true; } } /* * getID - Determines the ID of an instruction, consuming the ModR/M byte as * appropriate for extended and escape opcodes. Determines the attributes and * context for the instruction before doing so. * * @param insn - The instruction whose ID is to be determined. * @return - 0 if the ModR/M could be read when needed or was not needed; * nonzero otherwise. */ static int getID(struct InternalInstruction* insn, const void *miiArg) { uint16_t attrMask; uint16_t instructionID; dbgprintf(insn, "getID()"); attrMask = ATTR_NONE; if (insn->mode == MODE_64BIT) attrMask |= ATTR_64BIT; if (insn->vectorExtensionType != TYPE_NO_VEX_XOP) { attrMask |= (insn->vectorExtensionType == TYPE_EVEX) ? ATTR_EVEX : ATTR_VEX; if (insn->vectorExtensionType == TYPE_EVEX) { switch (ppFromEVEX3of4(insn->vectorExtensionPrefix[2])) { case VEX_PREFIX_66: attrMask |= ATTR_OPSIZE; break; case VEX_PREFIX_F3: attrMask |= ATTR_XS; break; case VEX_PREFIX_F2: attrMask |= ATTR_XD; break; } if (zFromEVEX4of4(insn->vectorExtensionPrefix[3])) attrMask |= ATTR_EVEXKZ; if (bFromEVEX4of4(insn->vectorExtensionPrefix[3])) attrMask |= ATTR_EVEXB; if (aaaFromEVEX4of4(insn->vectorExtensionPrefix[3])) attrMask |= ATTR_EVEXK; if (lFromEVEX4of4(insn->vectorExtensionPrefix[3])) attrMask |= ATTR_EVEXL; if (l2FromEVEX4of4(insn->vectorExtensionPrefix[3])) attrMask |= ATTR_EVEXL2; } else if (insn->vectorExtensionType == TYPE_VEX_3B) { switch (ppFromVEX3of3(insn->vectorExtensionPrefix[2])) { case VEX_PREFIX_66: attrMask |= ATTR_OPSIZE; break; case VEX_PREFIX_F3: attrMask |= ATTR_XS; break; case VEX_PREFIX_F2: attrMask |= ATTR_XD; break; } if (lFromVEX3of3(insn->vectorExtensionPrefix[2])) attrMask |= ATTR_VEXL; } else if (insn->vectorExtensionType == TYPE_VEX_2B) { switch (ppFromVEX2of2(insn->vectorExtensionPrefix[1])) { case VEX_PREFIX_66: attrMask |= ATTR_OPSIZE; break; case VEX_PREFIX_F3: attrMask |= ATTR_XS; break; case VEX_PREFIX_F2: attrMask |= ATTR_XD; break; } if (lFromVEX2of2(insn->vectorExtensionPrefix[1])) attrMask |= ATTR_VEXL; } else if (insn->vectorExtensionType == TYPE_XOP) { switch (ppFromXOP3of3(insn->vectorExtensionPrefix[2])) { case VEX_PREFIX_66: attrMask |= ATTR_OPSIZE; break; case VEX_PREFIX_F3: attrMask |= ATTR_XS; break; case VEX_PREFIX_F2: attrMask |= ATTR_XD; break; } if (lFromXOP3of3(insn->vectorExtensionPrefix[2])) attrMask |= ATTR_VEXL; } else { return -1; } } else { if (insn->mode != MODE_16BIT && isPrefixAtLocation(insn, 0x66, insn->necessaryPrefixLocation)) attrMask |= ATTR_OPSIZE; else if (isPrefixAtLocation(insn, 0x67, insn->necessaryPrefixLocation)) attrMask |= ATTR_ADSIZE; else if (isPrefixAtLocation(insn, 0xf3, insn->necessaryPrefixLocation)) attrMask |= ATTR_XS; else if (isPrefixAtLocation(insn, 0xf2, insn->necessaryPrefixLocation)) attrMask |= ATTR_XD; } if (insn->rexPrefix & 0x08) attrMask |= ATTR_REXW; /* * JCXZ/JECXZ need special handling for 16-bit mode because the meaning * of the AdSize prefix is inverted w.r.t. 32-bit mode. */ if (insn->mode == MODE_16BIT && insn->opcodeType == ONEBYTE && insn->opcode == 0xE3) attrMask ^= ATTR_ADSIZE; /* * In 64-bit mode all f64 superscripted opcodes ignore opcode size prefix * CALL/JMP/JCC instructions need to ignore 0x66 and consume 4 bytes */ if (insn->mode == MODE_64BIT && isPrefixAtLocation(insn, 0x66, insn->necessaryPrefixLocation)) { switch (insn->opcode) { case 0xE8: case 0xE9: // Take care of psubsb and other mmx instructions. if (insn->opcodeType == ONEBYTE) { attrMask ^= ATTR_OPSIZE; insn->immediateSize = 4; insn->displacementSize = 4; } break; case 0x82: case 0x83: case 0x84: case 0x85: case 0x86: case 0x87: case 0x88: case 0x89: case 0x8A: case 0x8B: case 0x8C: case 0x8D: case 0x8E: case 0x8F: // Take care of lea and three byte ops. if (insn->opcodeType == TWOBYTE) { attrMask ^= ATTR_OPSIZE; insn->immediateSize = 4; insn->displacementSize = 4; } break; } } if (getIDWithAttrMask(&instructionID, insn, attrMask)) return -1; /* The following clauses compensate for limitations of the tables. */ if (insn->mode != MODE_64BIT && insn->vectorExtensionType != TYPE_NO_VEX_XOP) { /* * The tables can't distinquish between cases where the W-bit is used to * select register size and cases where its a required part of the opcode. */ if ((insn->vectorExtensionType == TYPE_EVEX && wFromEVEX3of4(insn->vectorExtensionPrefix[2])) || (insn->vectorExtensionType == TYPE_VEX_3B && wFromVEX3of3(insn->vectorExtensionPrefix[2])) || (insn->vectorExtensionType == TYPE_XOP && wFromXOP3of3(insn->vectorExtensionPrefix[2]))) { uint16_t instructionIDWithREXW; if (getIDWithAttrMask(&instructionIDWithREXW, insn, attrMask | ATTR_REXW)) { insn->instructionID = instructionID; insn->spec = specifierForUID(instructionID); return 0; } const char *SpecName = GetInstrName(instructionIDWithREXW, miiArg); // If not a 64-bit instruction. Switch the opcode. if (!is64Bit(SpecName)) { insn->instructionID = instructionIDWithREXW; insn->spec = specifierForUID(instructionIDWithREXW); return 0; } } } /* * Absolute moves need special handling. * -For 16-bit mode because the meaning of the AdSize and OpSize prefixes are * inverted w.r.t. * -For 32-bit mode we need to ensure the ADSIZE prefix is observed in * any position. */ if (insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0)) { /* Make sure we observed the prefixes in any position. */ if (insn->prefixPresent[0x67]) attrMask |= ATTR_ADSIZE; if (insn->prefixPresent[0x66]) attrMask |= ATTR_OPSIZE; /* In 16-bit, invert the attributes. */ if (insn->mode == MODE_16BIT) attrMask ^= ATTR_ADSIZE | ATTR_OPSIZE; if (getIDWithAttrMask(&instructionID, insn, attrMask)) return -1; insn->instructionID = instructionID; insn->spec = specifierForUID(instructionID); return 0; } if ((insn->mode == MODE_16BIT || insn->prefixPresent[0x66]) && !(attrMask & ATTR_OPSIZE)) { /* * The instruction tables make no distinction between instructions that * allow OpSize anywhere (i.e., 16-bit operations) and that need it in a * particular spot (i.e., many MMX operations). In general we're * conservative, but in the specific case where OpSize is present but not * in the right place we check if there's a 16-bit operation. */ const struct InstructionSpecifier *spec; uint16_t instructionIDWithOpsize; const char *specName, *specWithOpSizeName; spec = specifierForUID(instructionID); if (getIDWithAttrMask(&instructionIDWithOpsize, insn, attrMask | ATTR_OPSIZE)) { /* * ModRM required with OpSize but not present; give up and return version * without OpSize set */ insn->instructionID = instructionID; insn->spec = spec; return 0; } specName = GetInstrName(instructionID, miiArg); specWithOpSizeName = GetInstrName(instructionIDWithOpsize, miiArg); if (is16BitEquivalent(specName, specWithOpSizeName) && (insn->mode == MODE_16BIT) ^ insn->prefixPresent[0x66]) { insn->instructionID = instructionIDWithOpsize; insn->spec = specifierForUID(instructionIDWithOpsize); } else { insn->instructionID = instructionID; insn->spec = spec; } return 0; } if (insn->opcodeType == ONEBYTE && insn->opcode == 0x90 && insn->rexPrefix & 0x01) { /* * NOOP shouldn't decode as NOOP if REX.b is set. Instead * it should decode as XCHG %r8, %eax. */ const struct InstructionSpecifier *spec; uint16_t instructionIDWithNewOpcode; const struct InstructionSpecifier *specWithNewOpcode; spec = specifierForUID(instructionID); /* Borrow opcode from one of the other XCHGar opcodes */ insn->opcode = 0x91; if (getIDWithAttrMask(&instructionIDWithNewOpcode, insn, attrMask)) { insn->opcode = 0x90; insn->instructionID = instructionID; insn->spec = spec; return 0; } specWithNewOpcode = specifierForUID(instructionIDWithNewOpcode); /* Change back */ insn->opcode = 0x90; insn->instructionID = instructionIDWithNewOpcode; insn->spec = specWithNewOpcode; return 0; } insn->instructionID = instructionID; insn->spec = specifierForUID(insn->instructionID); return 0; } /* * readSIB - Consumes the SIB byte to determine addressing information for an * instruction. * * @param insn - The instruction whose SIB byte is to be read. * @return - 0 if the SIB byte was successfully read; nonzero otherwise. */ static int readSIB(struct InternalInstruction* insn) { SIBIndex sibIndexBase = SIB_INDEX_NONE; SIBBase sibBaseBase = SIB_BASE_NONE; uint8_t index, base; dbgprintf(insn, "readSIB()"); if (insn->consumedSIB) return 0; insn->consumedSIB = true; switch (insn->addressSize) { case 2: dbgprintf(insn, "SIB-based addressing doesn't work in 16-bit mode"); return -1; case 4: sibIndexBase = SIB_INDEX_EAX; sibBaseBase = SIB_BASE_EAX; break; case 8: sibIndexBase = SIB_INDEX_RAX; sibBaseBase = SIB_BASE_RAX; break; } if (consumeByte(insn, &insn->sib)) return -1; index = indexFromSIB(insn->sib) | (xFromREX(insn->rexPrefix) << 3); // FIXME: The fifth bit (bit index 4) is only to be used for instructions // that understand VSIB indexing. ORing the bit in here is mildy dangerous // because performing math on an 'enum SIBIndex' can produce garbage. // Excluding the "none" value, it should cover 6 spaces of register names: // - 16 possibilities for 16-bit GPR starting at SIB_INDEX_BX_SI // - 16 possibilities for 32-bit GPR starting at SIB_INDEX_EAX // - 16 possibilities for 64-bit GPR starting at SIB_INDEX_RAX // - 32 possibilities for each of XMM, YMM, ZMM registers // When sibIndexBase gets assigned SIB_INDEX_RAX as it does in 64-bit mode, // summing in a fully decoded index between 0 and 31 can end up with a value // that looks like something in the low half of the XMM range. // translateRMMemory() tries to reverse the damage, with only partial success, // as evidenced by known bugs in "test/MC/Disassembler/X86/x86-64.txt" if (insn->vectorExtensionType == TYPE_EVEX) index |= v2FromEVEX4of4(insn->vectorExtensionPrefix[3]) << 4; if (index == 0x4) { insn->sibIndex = SIB_INDEX_NONE; } else { insn->sibIndex = (SIBIndex)(sibIndexBase + index); } insn->sibScale = 1 << scaleFromSIB(insn->sib); base = baseFromSIB(insn->sib) | (bFromREX(insn->rexPrefix) << 3); switch (base) { case 0x5: case 0xd: switch (modFromModRM(insn->modRM)) { case 0x0: insn->eaDisplacement = EA_DISP_32; insn->sibBase = SIB_BASE_NONE; break; case 0x1: insn->eaDisplacement = EA_DISP_8; insn->sibBase = (SIBBase)(sibBaseBase + base); break; case 0x2: insn->eaDisplacement = EA_DISP_32; insn->sibBase = (SIBBase)(sibBaseBase + base); break; case 0x3: debug("Cannot have Mod = 0b11 and a SIB byte"); return -1; } break; default: insn->sibBase = (SIBBase)(sibBaseBase + base); break; } return 0; } /* * readDisplacement - Consumes the displacement of an instruction. * * @param insn - The instruction whose displacement is to be read. * @return - 0 if the displacement byte was successfully read; nonzero * otherwise. */ static int readDisplacement(struct InternalInstruction* insn) { int8_t d8; int16_t d16; int32_t d32; dbgprintf(insn, "readDisplacement()"); if (insn->consumedDisplacement) return 0; insn->consumedDisplacement = true; insn->displacementOffset = insn->readerCursor - insn->startLocation; switch (insn->eaDisplacement) { case EA_DISP_NONE: insn->consumedDisplacement = false; break; case EA_DISP_8: if (consumeInt8(insn, &d8)) return -1; insn->displacement = d8; break; case EA_DISP_16: if (consumeInt16(insn, &d16)) return -1; insn->displacement = d16; break; case EA_DISP_32: if (consumeInt32(insn, &d32)) return -1; insn->displacement = d32; break; } insn->consumedDisplacement = true; return 0; } /* * readModRM - Consumes all addressing information (ModR/M byte, SIB byte, and * displacement) for an instruction and interprets it. * * @param insn - The instruction whose addressing information is to be read. * @return - 0 if the information was successfully read; nonzero otherwise. */ static int readModRM(struct InternalInstruction* insn) { uint8_t mod, rm, reg; dbgprintf(insn, "readModRM()"); if (insn->consumedModRM) return 0; if (consumeByte(insn, &insn->modRM)) return -1; insn->consumedModRM = true; mod = modFromModRM(insn->modRM); rm = rmFromModRM(insn->modRM); reg = regFromModRM(insn->modRM); /* * This goes by insn->registerSize to pick the correct register, which messes * up if we're using (say) XMM or 8-bit register operands. That gets fixed in * fixupReg(). */ switch (insn->registerSize) { case 2: insn->regBase = MODRM_REG_AX; insn->eaRegBase = EA_REG_AX; break; case 4: insn->regBase = MODRM_REG_EAX; insn->eaRegBase = EA_REG_EAX; break; case 8: insn->regBase = MODRM_REG_RAX; insn->eaRegBase = EA_REG_RAX; break; } reg |= rFromREX(insn->rexPrefix) << 3; rm |= bFromREX(insn->rexPrefix) << 3; if (insn->vectorExtensionType == TYPE_EVEX) { reg |= r2FromEVEX2of4(insn->vectorExtensionPrefix[1]) << 4; rm |= xFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 4; } insn->reg = (Reg)(insn->regBase + reg); switch (insn->addressSize) { case 2: insn->eaBaseBase = EA_BASE_BX_SI; switch (mod) { case 0x0: if (rm == 0x6) { insn->eaBase = EA_BASE_NONE; insn->eaDisplacement = EA_DISP_16; if (readDisplacement(insn)) return -1; } else { insn->eaBase = (EABase)(insn->eaBaseBase + rm); insn->eaDisplacement = EA_DISP_NONE; } break; case 0x1: insn->eaBase = (EABase)(insn->eaBaseBase + rm); insn->eaDisplacement = EA_DISP_8; insn->displacementSize = 1; if (readDisplacement(insn)) return -1; break; case 0x2: insn->eaBase = (EABase)(insn->eaBaseBase + rm); insn->eaDisplacement = EA_DISP_16; if (readDisplacement(insn)) return -1; break; case 0x3: insn->eaBase = (EABase)(insn->eaRegBase + rm); if (readDisplacement(insn)) return -1; break; } break; case 4: case 8: insn->eaBaseBase = (insn->addressSize == 4 ? EA_BASE_EAX : EA_BASE_RAX); switch (mod) { case 0x0: insn->eaDisplacement = EA_DISP_NONE; /* readSIB may override this */ // In determining whether RIP-relative mode is used (rm=5), // or whether a SIB byte is present (rm=4), // the extension bits (REX.b and EVEX.x) are ignored. switch (rm & 7) { case 0x4: // SIB byte is present insn->eaBase = (insn->addressSize == 4 ? EA_BASE_sib : EA_BASE_sib64); if (readSIB(insn) || readDisplacement(insn)) return -1; break; case 0x5: // RIP-relative insn->eaBase = EA_BASE_NONE; insn->eaDisplacement = EA_DISP_32; if (readDisplacement(insn)) return -1; break; default: insn->eaBase = (EABase)(insn->eaBaseBase + rm); break; } break; case 0x1: insn->displacementSize = 1; /* FALLTHROUGH */ case 0x2: insn->eaDisplacement = (mod == 0x1 ? EA_DISP_8 : EA_DISP_32); switch (rm & 7) { case 0x4: // SIB byte is present insn->eaBase = EA_BASE_sib; if (readSIB(insn) || readDisplacement(insn)) return -1; break; default: insn->eaBase = (EABase)(insn->eaBaseBase + rm); if (readDisplacement(insn)) return -1; break; } break; case 0x3: insn->eaDisplacement = EA_DISP_NONE; insn->eaBase = (EABase)(insn->eaRegBase + rm); break; } break; } /* switch (insn->addressSize) */ return 0; } #define GENERIC_FIXUP_FUNC(name, base, prefix) \ static uint16_t name(struct InternalInstruction *insn, \ OperandType type, \ uint8_t index, \ uint8_t *valid) { \ *valid = 1; \ switch (type) { \ default: \ debug("Unhandled register type"); \ *valid = 0; \ return 0; \ case TYPE_Rv: \ return base + index; \ case TYPE_R8: \ if (insn->rexPrefix && \ index >= 4 && index <= 7) { \ return prefix##_SPL + (index - 4); \ } else { \ return prefix##_AL + index; \ } \ case TYPE_R16: \ return prefix##_AX + index; \ case TYPE_R32: \ return prefix##_EAX + index; \ case TYPE_R64: \ return prefix##_RAX + index; \ case TYPE_XMM512: \ return prefix##_ZMM0 + index; \ case TYPE_XMM256: \ return prefix##_YMM0 + index; \ case TYPE_XMM128: \ case TYPE_XMM64: \ case TYPE_XMM32: \ return prefix##_XMM0 + index; \ case TYPE_VK1: \ case TYPE_VK2: \ case TYPE_VK4: \ case TYPE_VK8: \ case TYPE_VK16: \ case TYPE_VK32: \ case TYPE_VK64: \ if (index > 7) \ *valid = 0; \ return prefix##_K0 + index; \ case TYPE_MM64: \ return prefix##_MM0 + (index & 0x7); \ case TYPE_SEGMENTREG: \ if (index > 5) \ *valid = 0; \ return prefix##_ES + index; \ case TYPE_DEBUGREG: \ return prefix##_DR0 + index; \ case TYPE_CONTROLREG: \ return prefix##_CR0 + index; \ case TYPE_BNDR: \ if (index > 3) \ *valid = 0; \ return prefix##_BND0 + index; \ } \ } /* * fixup*Value - Consults an operand type to determine the meaning of the * reg or R/M field. If the operand is an XMM operand, for example, an * operand would be XMM0 instead of AX, which readModRM() would otherwise * misinterpret it as. * * @param insn - The instruction containing the operand. * @param type - The operand type. * @param index - The existing value of the field as reported by readModRM(). * @param valid - The address of a uint8_t. The target is set to 1 if the * field is valid for the register class; 0 if not. * @return - The proper value. */ GENERIC_FIXUP_FUNC(fixupRegValue, insn->regBase, MODRM_REG) GENERIC_FIXUP_FUNC(fixupRMValue, insn->eaRegBase, EA_REG) /* * fixupReg - Consults an operand specifier to determine which of the * fixup*Value functions to use in correcting readModRM()'ss interpretation. * * @param insn - See fixup*Value(). * @param op - The operand specifier. * @return - 0 if fixup was successful; -1 if the register returned was * invalid for its class. */ static int fixupReg(struct InternalInstruction *insn, const struct OperandSpecifier *op) { uint8_t valid; dbgprintf(insn, "fixupReg()"); switch ((OperandEncoding)op->encoding) { default: debug("Expected a REG or R/M encoding in fixupReg"); return -1; case ENCODING_VVVV: insn->vvvv = (Reg)fixupRegValue(insn, (OperandType)op->type, insn->vvvv, &valid); if (!valid) return -1; break; case ENCODING_REG: insn->reg = (Reg)fixupRegValue(insn, (OperandType)op->type, insn->reg - insn->regBase, &valid); if (!valid) return -1; break; CASE_ENCODING_RM: if (insn->eaBase >= insn->eaRegBase) { insn->eaBase = (EABase)fixupRMValue(insn, (OperandType)op->type, insn->eaBase - insn->eaRegBase, &valid); if (!valid) return -1; } break; } return 0; } /* * readOpcodeRegister - Reads an operand from the opcode field of an * instruction and interprets it appropriately given the operand width. * Handles AddRegFrm instructions. * * @param insn - the instruction whose opcode field is to be read. * @param size - The width (in bytes) of the register being specified. * 1 means AL and friends, 2 means AX, 4 means EAX, and 8 means * RAX. * @return - 0 on success; nonzero otherwise. */ static int readOpcodeRegister(struct InternalInstruction* insn, uint8_t size) { dbgprintf(insn, "readOpcodeRegister()"); if (size == 0) size = insn->registerSize; switch (size) { case 1: insn->opcodeRegister = (Reg)(MODRM_REG_AL + ((bFromREX(insn->rexPrefix) << 3) | (insn->opcode & 7))); if (insn->rexPrefix && insn->opcodeRegister >= MODRM_REG_AL + 0x4 && insn->opcodeRegister < MODRM_REG_AL + 0x8) { insn->opcodeRegister = (Reg)(MODRM_REG_SPL + (insn->opcodeRegister - MODRM_REG_AL - 4)); } break; case 2: insn->opcodeRegister = (Reg)(MODRM_REG_AX + ((bFromREX(insn->rexPrefix) << 3) | (insn->opcode & 7))); break; case 4: insn->opcodeRegister = (Reg)(MODRM_REG_EAX + ((bFromREX(insn->rexPrefix) << 3) | (insn->opcode & 7))); break; case 8: insn->opcodeRegister = (Reg)(MODRM_REG_RAX + ((bFromREX(insn->rexPrefix) << 3) | (insn->opcode & 7))); break; } return 0; } /* * readImmediate - Consumes an immediate operand from an instruction, given the * desired operand size. * * @param insn - The instruction whose operand is to be read. * @param size - The width (in bytes) of the operand. * @return - 0 if the immediate was successfully consumed; nonzero * otherwise. */ static int readImmediate(struct InternalInstruction* insn, uint8_t size) { uint8_t imm8; uint16_t imm16; uint32_t imm32; uint64_t imm64; dbgprintf(insn, "readImmediate()"); if (insn->numImmediatesConsumed == 2) { debug("Already consumed two immediates"); return -1; } if (size == 0) size = insn->immediateSize; else insn->immediateSize = size; insn->immediateOffset = insn->readerCursor - insn->startLocation; switch (size) { case 1: if (consumeByte(insn, &imm8)) return -1; insn->immediates[insn->numImmediatesConsumed] = imm8; break; case 2: if (consumeUInt16(insn, &imm16)) return -1; insn->immediates[insn->numImmediatesConsumed] = imm16; break; case 4: if (consumeUInt32(insn, &imm32)) return -1; insn->immediates[insn->numImmediatesConsumed] = imm32; break; case 8: if (consumeUInt64(insn, &imm64)) return -1; insn->immediates[insn->numImmediatesConsumed] = imm64; break; } insn->numImmediatesConsumed++; return 0; } /* * readVVVV - Consumes vvvv from an instruction if it has a VEX prefix. * * @param insn - The instruction whose operand is to be read. * @return - 0 if the vvvv was successfully consumed; nonzero * otherwise. */ static int readVVVV(struct InternalInstruction* insn) { dbgprintf(insn, "readVVVV()"); int vvvv; if (insn->vectorExtensionType == TYPE_EVEX) vvvv = (v2FromEVEX4of4(insn->vectorExtensionPrefix[3]) << 4 | vvvvFromEVEX3of4(insn->vectorExtensionPrefix[2])); else if (insn->vectorExtensionType == TYPE_VEX_3B) vvvv = vvvvFromVEX3of3(insn->vectorExtensionPrefix[2]); else if (insn->vectorExtensionType == TYPE_VEX_2B) vvvv = vvvvFromVEX2of2(insn->vectorExtensionPrefix[1]); else if (insn->vectorExtensionType == TYPE_XOP) vvvv = vvvvFromXOP3of3(insn->vectorExtensionPrefix[2]); else return -1; if (insn->mode != MODE_64BIT) vvvv &= 0x7; insn->vvvv = static_cast(vvvv); return 0; } /* * readMaskRegister - Reads an mask register from the opcode field of an * instruction. * * @param insn - The instruction whose opcode field is to be read. * @return - 0 on success; nonzero otherwise. */ static int readMaskRegister(struct InternalInstruction* insn) { dbgprintf(insn, "readMaskRegister()"); if (insn->vectorExtensionType != TYPE_EVEX) return -1; insn->writemask = static_cast(aaaFromEVEX4of4(insn->vectorExtensionPrefix[3])); return 0; } /* * readOperands - Consults the specifier for an instruction and consumes all * operands for that instruction, interpreting them as it goes. * * @param insn - The instruction whose operands are to be read and interpreted. * @return - 0 if all operands could be read; nonzero otherwise. */ static int readOperands(struct InternalInstruction* insn) { int hasVVVV, needVVVV; int sawRegImm = 0; dbgprintf(insn, "readOperands()"); /* If non-zero vvvv specified, need to make sure one of the operands uses it. */ hasVVVV = !readVVVV(insn); needVVVV = hasVVVV && (insn->vvvv != 0); for (const auto &Op : x86OperandSets[insn->spec->operands]) { switch (Op.encoding) { case ENCODING_NONE: case ENCODING_SI: case ENCODING_DI: break; case ENCODING_REG: CASE_ENCODING_RM: if (readModRM(insn)) return -1; if (fixupReg(insn, &Op)) return -1; // Apply the AVX512 compressed displacement scaling factor. if (Op.encoding != ENCODING_REG && insn->eaDisplacement == EA_DISP_8) insn->displacement *= 1 << (Op.encoding - ENCODING_RM); break; case ENCODING_IB: if (sawRegImm) { /* Saw a register immediate so don't read again and instead split the previous immediate. FIXME: This is a hack. */ insn->immediates[insn->numImmediatesConsumed] = insn->immediates[insn->numImmediatesConsumed - 1] & 0xf; ++insn->numImmediatesConsumed; break; } if (readImmediate(insn, 1)) return -1; if (Op.type == TYPE_XMM128 || Op.type == TYPE_XMM256) sawRegImm = 1; break; case ENCODING_IW: if (readImmediate(insn, 2)) return -1; break; case ENCODING_ID: if (readImmediate(insn, 4)) return -1; break; case ENCODING_IO: if (readImmediate(insn, 8)) return -1; break; case ENCODING_Iv: if (readImmediate(insn, insn->immediateSize)) return -1; break; case ENCODING_Ia: if (readImmediate(insn, insn->addressSize)) return -1; break; case ENCODING_RB: if (readOpcodeRegister(insn, 1)) return -1; break; case ENCODING_RW: if (readOpcodeRegister(insn, 2)) return -1; break; case ENCODING_RD: if (readOpcodeRegister(insn, 4)) return -1; break; case ENCODING_RO: if (readOpcodeRegister(insn, 8)) return -1; break; case ENCODING_Rv: if (readOpcodeRegister(insn, 0)) return -1; break; case ENCODING_FP: break; case ENCODING_VVVV: needVVVV = 0; /* Mark that we have found a VVVV operand. */ if (!hasVVVV) return -1; if (fixupReg(insn, &Op)) return -1; break; case ENCODING_WRITEMASK: if (readMaskRegister(insn)) return -1; break; case ENCODING_DUP: break; default: dbgprintf(insn, "Encountered an operand with an unknown encoding."); return -1; } } /* If we didn't find ENCODING_VVVV operand, but non-zero vvvv present, fail */ if (needVVVV) return -1; return 0; } /* * decodeInstruction - Reads and interprets a full instruction provided by the * user. * * @param insn - A pointer to the instruction to be populated. Must be * pre-allocated. * @param reader - The function to be used to read the instruction's bytes. * @param readerArg - A generic argument to be passed to the reader to store * any internal state. * @param logger - If non-NULL, the function to be used to write log messages * and warnings. * @param loggerArg - A generic argument to be passed to the logger to store * any internal state. * @param startLoc - The address (in the reader's address space) of the first * byte in the instruction. * @param mode - The mode (real mode, IA-32e, or IA-32e in 64-bit mode) to * decode the instruction in. * @return - 0 if the instruction's memory could be read; nonzero if * not. */ int llvm::X86Disassembler::decodeInstruction( struct InternalInstruction *insn, byteReader_t reader, const void *readerArg, dlog_t logger, void *loggerArg, const void *miiArg, uint64_t startLoc, DisassemblerMode mode) { memset(insn, 0, sizeof(struct InternalInstruction)); insn->reader = reader; insn->readerArg = readerArg; insn->dlog = logger; insn->dlogArg = loggerArg; insn->startLocation = startLoc; insn->readerCursor = startLoc; insn->mode = mode; insn->numImmediatesConsumed = 0; if (readPrefixes(insn) || readOpcode(insn) || getID(insn, miiArg) || insn->instructionID == 0 || readOperands(insn)) return -1; insn->operands = x86OperandSets[insn->spec->operands]; insn->length = insn->readerCursor - insn->startLocation; dbgprintf(insn, "Read from 0x%llx to 0x%llx: length %zu", startLoc, insn->readerCursor, insn->length); if (insn->length > 15) dbgprintf(insn, "Instruction exceeds 15-byte limit"); return 0; }