/*===- X86DisassemblerDecoder.c - Disassembler decoder -------------*- C -*-==* * * 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" #include "X86GenDisassemblerTables.inc" #define TRUE 1 #define FALSE 0 typedef int8_t bool; #ifdef __GNUC__ #define NORETURN __attribute__((noreturn)) #else #define NORETURN #endif #ifndef NDEBUG #define debug(s) do { x86DisassemblerDebug(__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(uint8_t attrMask) { return 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, uint8_t opcode) { const struct ContextDecision* decision = 0; 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; } return decision->opcodeDecisions[insnContext].modRMDecisions[opcode]. modrm_type != MODRM_ONEENTRY; return 0; } /* * 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) { struct ModRMDecision* dec; switch (type) { default: debug("Unknown opcode type"); return 0; 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; } switch (dec->modrm_type) { default: debug("Corrupt table! Unknown modrm_type"); return 0; case MODRM_ONEENTRY: return dec->instructionIDs[0]; case MODRM_SPLITRM: if (modFromModRM(modRM) == 0x3) return dec->instructionIDs[1]; else return dec->instructionIDs[0]; case MODRM_FULL: return 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 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 | ((type)byte << ((type)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); return; } /* * 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) { if (insn->prefixPresent[prefix] == 1 && insn->prefixLocations[prefix] == location) return TRUE; else return FALSE; } /* * 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; BOOL hasAdSize = FALSE; BOOL hasOpSize = FALSE; dbgprintf(insn, "readPrefixes()"); while (isPrefix) { prefixLocation = insn->readerCursor; if (consumeByte(insn, &byte)) return -1; 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); } 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); } 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 (consumeByte(insn, ¤t)) return -1; if (current == 0x0f) { dbgprintf(insn, "Found a two-byte escape prefix (0x%hhx)", current); insn->twoByteEscape = current; if (consumeByte(insn, ¤t)) return -1; if (current == 0x38) { dbgprintf(insn, "Found a three-byte escape prefix (0x%hhx)", current); insn->threeByteEscape = 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); insn->threeByteEscape = 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, uint8_t attrMask) { BOOL hasModRMExtension; uint8_t instructionClass; instructionClass = contextForAttrs(attrMask); hasModRMExtension = modRMRequired(insn->opcodeType, instructionClass, insn->opcode); if (hasModRMExtension) { readModRM(insn); *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 is16BitEquvalent(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; } } } /* * is64BitEquivalent - Determines whether two instruction names refer to * equivalent instructions but one is 64-bit whereas the other is not. * * @param orig - The instruction that is not 64-bit * @param equiv - The instruction that is 64-bit */ static BOOL is64BitEquivalent(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] == 'W' || orig[i] == 'L') && equiv[i] == 'Q') continue; if ((orig[i] == '1' || orig[i] == '3') && equiv[i] == '6') continue; if ((orig[i] == '6' || orig[i] == '2') && equiv[i] == '4') continue; return FALSE; } } } /* * 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) { uint8_t attrMask; uint16_t instructionID; dbgprintf(insn, "getID()"); attrMask = ATTR_NONE; if (insn->mode == MODE_64BIT) attrMask |= ATTR_64BIT; if (insn->rexPrefix & 0x08) attrMask |= ATTR_REXW; if (isPrefixAtLocation(insn, 0x66, insn->necessaryPrefixLocation)) attrMask |= ATTR_OPSIZE; else if (isPrefixAtLocation(insn, 0xf3, insn->necessaryPrefixLocation)) attrMask |= ATTR_XS; else if (isPrefixAtLocation(insn, 0xf2, insn->necessaryPrefixLocation)) attrMask |= ATTR_XD; if (getIDWithAttrMask(&instructionID, insn, attrMask)) return -1; /* The following clauses compensate for limitations of the tables. */ if ((attrMask & ATTR_XD) && (attrMask & ATTR_REXW)) { /* * Although for SSE instructions it is usually necessary to treat REX.W+F2 * as F2 for decode (in the absence of a 64BIT_REXW_XD category) there is * an occasional instruction where F2 is incidental and REX.W is the more * significant. If the decoded instruction is 32-bit and adding REX.W * instead of F2 changes a 32 to a 64, we adopt the new encoding. */ struct InstructionSpecifier* spec; uint16_t instructionIDWithREXw; struct InstructionSpecifier* specWithREXw; spec = specifierForUID(instructionID); if (getIDWithAttrMask(&instructionIDWithREXw, insn, attrMask & (~ATTR_XD))) { /* * Decoding with REX.w would yield nothing; give up and return original * decode. */ insn->instructionID = instructionID; insn->spec = spec; return 0; } specWithREXw = specifierForUID(instructionIDWithREXw); if (is64BitEquivalent(spec->name, specWithREXw->name)) { insn->instructionID = instructionIDWithREXw; insn->spec = specWithREXw; } else { insn->instructionID = instructionID; insn->spec = spec; } return 0; } if (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. */ struct InstructionSpecifier* spec; uint16_t instructionIDWithOpsize; struct InstructionSpecifier* specWithOpsize; 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; } specWithOpsize = specifierForUID(instructionIDWithOpsize); if (is16BitEquvalent(spec->name, specWithOpsize->name)) { insn->instructionID = instructionIDWithOpsize; insn->spec = specWithOpsize; } else { insn->instructionID = instructionID; insn->spec = spec; } 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 = 0; SIBBase sibBaseBase = 0; 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; break; 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); switch (index) { case 0x4: insn->sibIndex = SIB_INDEX_NONE; break; default: insn->sibIndex = (EABase)(sibIndexBase + index); if (insn->sibIndex == SIB_INDEX_sib || insn->sibIndex == SIB_INDEX_sib64) insn->sibIndex = SIB_INDEX_NONE; break; } switch (scaleFromSIB(insn->sib)) { case 0: insn->sibScale = 1; break; case 1: insn->sibScale = 2; break; case 2: insn->sibScale = 4; break; case 3: insn->sibScale = 8; break; } base = baseFromSIB(insn->sib) | (bFromREX(insn->rexPrefix) << 3); switch (base) { case 0x5: 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 = (insn->addressSize == 4 ? SIB_BASE_EBP : SIB_BASE_RBP); break; case 0x2: insn->eaDisplacement = EA_DISP_32; insn->sibBase = (insn->addressSize == 4 ? SIB_BASE_EBP : SIB_BASE_RBP); break; case 0x3: debug("Cannot have Mod = 0b11 and a SIB byte"); return -1; } break; default: insn->sibBase = (EABase)(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; 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; consumeByte(insn, &insn->modRM); 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; 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; 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 */ switch (rm) { case 0x4: case 0xc: /* in case REXW.b is set */ insn->eaBase = (insn->addressSize == 4 ? EA_BASE_sib : EA_BASE_sib64); readSIB(insn); if (readDisplacement(insn)) return -1; break; case 0x5: 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: case 0x2: insn->eaDisplacement = (mod == 0x1 ? EA_DISP_8 : EA_DISP_32); switch (rm) { case 0x4: case 0xc: /* in case REXW.b is set */ insn->eaBase = EA_BASE_sib; readSIB(insn); if (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 uint8_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_XMM128: \ case TYPE_XMM64: \ case TYPE_XMM32: \ case TYPE_XMM: \ return prefix##_XMM0 + index; \ case TYPE_MM64: \ case TYPE_MM32: \ case TYPE_MM: \ if (index > 7) \ *valid = 0; \ return prefix##_MM0 + index; \ case TYPE_SEGMENTREG: \ if (index > 5) \ *valid = 0; \ return prefix##_ES + index; \ case TYPE_DEBUGREG: \ if (index > 7) \ *valid = 0; \ return prefix##_DR0 + index; \ case TYPE_CONTROLREG: \ if (index > 8) \ *valid = 0; \ return prefix##_CR0 + 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, 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_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; } /* * readOpcodeModifier - Reads an operand from the opcode field of an * instruction. Handles AddRegFrm instructions. * * @param insn - The instruction whose opcode field is to be read. * @param inModRM - Indicates that the opcode field is to be read from the * ModR/M extension; useful for escape opcodes * @return - 0 on success; nonzero otherwise. */ static int readOpcodeModifier(struct InternalInstruction* insn) { dbgprintf(insn, "readOpcodeModifier()"); if (insn->consumedOpcodeModifier) return 0; insn->consumedOpcodeModifier = TRUE; switch (insn->spec->modifierType) { default: debug("Unknown modifier type."); return -1; case MODIFIER_NONE: debug("No modifier but an operand expects one."); return -1; case MODIFIER_OPCODE: insn->opcodeModifier = insn->opcode - insn->spec->modifierBase; return 0; case MODIFIER_MODRM: insn->opcodeModifier = insn->modRM - insn->spec->modifierBase; 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 - See readOpcodeModifier(). * @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 (readOpcodeModifier(insn)) return -1; if (size == 0) size = insn->registerSize; switch (size) { case 1: insn->opcodeRegister = (Reg)(MODRM_REG_AL + ((bFromREX(insn->rexPrefix) << 3) | insn->opcodeModifier)); 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->opcodeModifier)); break; case 4: insn->opcodeRegister = (Reg)(MODRM_REG_EAX + ((bFromREX(insn->rexPrefix) << 3) | insn->opcodeModifier)); break; case 8: insn->opcodeRegister = (Reg)(MODRM_REG_RAX + ((bFromREX(insn->rexPrefix) << 3) | insn->opcodeModifier)); 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; 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; } /* * 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 index; dbgprintf(insn, "readOperands()"); for (index = 0; index < X86_MAX_OPERANDS; ++index) { switch (insn->spec->operands[index].encoding) { case ENCODING_NONE: break; case ENCODING_REG: case ENCODING_RM: if (readModRM(insn)) return -1; if (fixupReg(insn, &insn->spec->operands[index])) return -1; break; case ENCODING_CB: case ENCODING_CW: case ENCODING_CD: case ENCODING_CP: case ENCODING_CO: case ENCODING_CT: dbgprintf(insn, "We currently don't hande code-offset encodings"); return -1; case ENCODING_IB: if (readImmediate(insn, 1)) return -1; if (insn->spec->operands[index].type == TYPE_IMM3 && insn->immediates[insn->numImmediatesConsumed - 1] > 7) return -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_I: if (readOpcodeModifier(insn)) return -1; case ENCODING_DUP: break; default: dbgprintf(insn, "Encountered an operand with an unknown encoding."); 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 decodeInstruction(struct InternalInstruction* insn, byteReader_t reader, void* readerArg, dlog_t logger, void* loggerArg, 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) || insn->instructionID == 0 || readOperands(insn)) return -1; 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; }