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diff --git a/sandbox/win/src/sidestep/mini_disassembler.cpp b/sandbox/win/src/sidestep/mini_disassembler.cpp
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Implementation of MiniDisassembler.
+
+#ifdef _WIN64
+#error The code in this file should not be used on 64-bit Windows.
+#endif
+
+#include "sandbox/win/src/sidestep/mini_disassembler.h"
+
+namespace sidestep {
+
+MiniDisassembler::MiniDisassembler(bool operand_default_is_32_bits,
+ bool address_default_is_32_bits)
+ : operand_default_is_32_bits_(operand_default_is_32_bits),
+ address_default_is_32_bits_(address_default_is_32_bits) {
+ Initialize();
+}
+
+MiniDisassembler::MiniDisassembler()
+ : operand_default_is_32_bits_(true),
+ address_default_is_32_bits_(true) {
+ Initialize();
+}
+
+InstructionType MiniDisassembler::Disassemble(
+ unsigned char* start_byte,
+ unsigned int* instruction_bytes) {
+ // Clean up any state from previous invocations.
+ Initialize();
+
+ // Start by processing any prefixes.
+ unsigned char* current_byte = start_byte;
+ unsigned int size = 0;
+ InstructionType instruction_type = ProcessPrefixes(current_byte, &size);
+
+ if (IT_UNKNOWN == instruction_type)
+ return instruction_type;
+
+ current_byte += size;
+ size = 0;
+
+ // Invariant: We have stripped all prefixes, and the operand_is_32_bits_
+ // and address_is_32_bits_ flags are correctly set.
+
+ instruction_type = ProcessOpcode(current_byte, 0, &size);
+
+ // Check for error processing instruction
+ if ((IT_UNKNOWN == instruction_type_) || (IT_UNUSED == instruction_type_)) {
+ return IT_UNKNOWN;
+ }
+
+ current_byte += size;
+
+ // Invariant: operand_bytes_ indicates the total size of operands
+ // specified by the opcode and/or ModR/M byte and/or SIB byte.
+ // pCurrentByte points to the first byte after the ModR/M byte, or after
+ // the SIB byte if it is present (i.e. the first byte of any operands
+ // encoded in the instruction).
+
+ // We get the total length of any prefixes, the opcode, and the ModR/M and
+ // SIB bytes if present, by taking the difference of the original starting
+ // address and the current byte (which points to the first byte of the
+ // operands if present, or to the first byte of the next instruction if
+ // they are not). Adding the count of bytes in the operands encoded in
+ // the instruction gives us the full length of the instruction in bytes.
+ *instruction_bytes += operand_bytes_ + (current_byte - start_byte);
+
+ // Return the instruction type, which was set by ProcessOpcode().
+ return instruction_type_;
+}
+
+void MiniDisassembler::Initialize() {
+ operand_is_32_bits_ = operand_default_is_32_bits_;
+ address_is_32_bits_ = address_default_is_32_bits_;
+ operand_bytes_ = 0;
+ have_modrm_ = false;
+ should_decode_modrm_ = false;
+ instruction_type_ = IT_UNKNOWN;
+ got_f2_prefix_ = false;
+ got_f3_prefix_ = false;
+ got_66_prefix_ = false;
+}
+
+InstructionType MiniDisassembler::ProcessPrefixes(unsigned char* start_byte,
+ unsigned int* size) {
+ InstructionType instruction_type = IT_GENERIC;
+ const Opcode& opcode = s_ia32_opcode_map_[0].table_[*start_byte];
+
+ switch (opcode.type_) {
+ case IT_PREFIX_ADDRESS:
+ address_is_32_bits_ = !address_default_is_32_bits_;
+ goto nochangeoperand;
+ case IT_PREFIX_OPERAND:
+ operand_is_32_bits_ = !operand_default_is_32_bits_;
+ nochangeoperand:
+ case IT_PREFIX:
+
+ if (0xF2 == (*start_byte))
+ got_f2_prefix_ = true;
+ else if (0xF3 == (*start_byte))
+ got_f3_prefix_ = true;
+ else if (0x66 == (*start_byte))
+ got_66_prefix_ = true;
+
+ instruction_type = opcode.type_;
+ (*size)++;
+ // we got a prefix, so add one and check next byte
+ ProcessPrefixes(start_byte + 1, size);
+ default:
+ break; // not a prefix byte
+ }
+
+ return instruction_type;
+}
+
+InstructionType MiniDisassembler::ProcessOpcode(unsigned char* start_byte,
+ unsigned int table_index,
+ unsigned int* size) {
+ const OpcodeTable& table = s_ia32_opcode_map_[table_index]; // Get our table
+ unsigned char current_byte = (*start_byte) >> table.shift_;
+ current_byte = current_byte & table.mask_; // Mask out the bits we will use
+
+ // Check whether the byte we have is inside the table we have.
+ if (current_byte < table.min_lim_ || current_byte > table.max_lim_) {
+ instruction_type_ = IT_UNKNOWN;
+ return instruction_type_;
+ }
+
+ const Opcode& opcode = table.table_[current_byte];
+ if (IT_UNUSED == opcode.type_) {
+ // This instruction is not used by the IA-32 ISA, so we indicate
+ // this to the user. Probably means that we were pointed to
+ // a byte in memory that was not the start of an instruction.
+ instruction_type_ = IT_UNUSED;
+ return instruction_type_;
+ } else if (IT_REFERENCE == opcode.type_) {
+ // We are looking at an opcode that has more bytes (or is continued
+ // in the ModR/M byte). Recursively find the opcode definition in
+ // the table for the opcode's next byte.
+ (*size)++;
+ ProcessOpcode(start_byte + 1, opcode.table_index_, size);
+ return instruction_type_;
+ }
+
+ const SpecificOpcode* specific_opcode = reinterpret_cast<
+ const SpecificOpcode*>(&opcode);
+ if (opcode.is_prefix_dependent_) {
+ if (got_f2_prefix_ && opcode.opcode_if_f2_prefix_.mnemonic_ != 0) {
+ specific_opcode = &opcode.opcode_if_f2_prefix_;
+ } else if (got_f3_prefix_ && opcode.opcode_if_f3_prefix_.mnemonic_ != 0) {
+ specific_opcode = &opcode.opcode_if_f3_prefix_;
+ } else if (got_66_prefix_ && opcode.opcode_if_66_prefix_.mnemonic_ != 0) {
+ specific_opcode = &opcode.opcode_if_66_prefix_;
+ }
+ }
+
+ // Inv: The opcode type is known.
+ instruction_type_ = specific_opcode->type_;
+
+ // Let's process the operand types to see if we have any immediate
+ // operands, and/or a ModR/M byte.
+
+ ProcessOperand(specific_opcode->flag_dest_);
+ ProcessOperand(specific_opcode->flag_source_);
+ ProcessOperand(specific_opcode->flag_aux_);
+
+ // Inv: We have processed the opcode and incremented operand_bytes_
+ // by the number of bytes of any operands specified by the opcode
+ // that are stored in the instruction (not registers etc.). Now
+ // we need to return the total number of bytes for the opcode and
+ // for the ModR/M or SIB bytes if they are present.
+
+ if (table.mask_ != 0xff) {
+ if (have_modrm_) {
+ // we're looking at a ModR/M byte so we're not going to
+ // count that into the opcode size
+ ProcessModrm(start_byte, size);
+ return IT_GENERIC;
+ } else {
+ // need to count the ModR/M byte even if it's just being
+ // used for opcode extension
+ (*size)++;
+ return IT_GENERIC;
+ }
+ } else {
+ if (have_modrm_) {
+ // The ModR/M byte is the next byte.
+ (*size)++;
+ ProcessModrm(start_byte + 1, size);
+ return IT_GENERIC;
+ } else {
+ (*size)++;
+ return IT_GENERIC;
+ }
+ }
+}
+
+bool MiniDisassembler::ProcessOperand(int flag_operand) {
+ bool succeeded = true;
+ if (AM_NOT_USED == flag_operand)
+ return succeeded;
+
+ // Decide what to do based on the addressing mode.
+ switch (flag_operand & AM_MASK) {
+ // No ModR/M byte indicated by these addressing modes, and no
+ // additional (e.g. immediate) parameters.
+ case AM_A: // Direct address
+ case AM_F: // EFLAGS register
+ case AM_X: // Memory addressed by the DS:SI register pair
+ case AM_Y: // Memory addressed by the ES:DI register pair
+ case AM_IMPLICIT: // Parameter is implicit, occupies no space in
+ // instruction
+ break;
+
+ // There is a ModR/M byte but it does not necessarily need
+ // to be decoded.
+ case AM_C: // reg field of ModR/M selects a control register
+ case AM_D: // reg field of ModR/M selects a debug register
+ case AM_G: // reg field of ModR/M selects a general register
+ case AM_P: // reg field of ModR/M selects an MMX register
+ case AM_R: // mod field of ModR/M may refer only to a general register
+ case AM_S: // reg field of ModR/M selects a segment register
+ case AM_T: // reg field of ModR/M selects a test register
+ case AM_V: // reg field of ModR/M selects a 128-bit XMM register
+ have_modrm_ = true;
+ break;
+
+ // In these addressing modes, there is a ModR/M byte and it needs to be
+ // decoded. No other (e.g. immediate) params than indicated in ModR/M.
+ case AM_E: // Operand is either a general-purpose register or memory,
+ // specified by ModR/M byte
+ case AM_M: // ModR/M byte will refer only to memory
+ case AM_Q: // Operand is either an MMX register or memory (complex
+ // evaluation), specified by ModR/M byte
+ case AM_W: // Operand is either a 128-bit XMM register or memory (complex
+ // eval), specified by ModR/M byte
+ have_modrm_ = true;
+ should_decode_modrm_ = true;
+ break;
+
+ // These addressing modes specify an immediate or an offset value
+ // directly, so we need to look at the operand type to see how many
+ // bytes.
+ case AM_I: // Immediate data.
+ case AM_J: // Jump to offset.
+ case AM_O: // Operand is at offset.
+ switch (flag_operand & OT_MASK) {
+ case OT_B: // Byte regardless of operand-size attribute.
+ operand_bytes_ += OS_BYTE;
+ break;
+ case OT_C: // Byte or word, depending on operand-size attribute.
+ if (operand_is_32_bits_)
+ operand_bytes_ += OS_WORD;
+ else
+ operand_bytes_ += OS_BYTE;
+ break;
+ case OT_D: // Doubleword, regardless of operand-size attribute.
+ operand_bytes_ += OS_DOUBLE_WORD;
+ break;
+ case OT_DQ: // Double-quadword, regardless of operand-size attribute.
+ operand_bytes_ += OS_DOUBLE_QUAD_WORD;
+ break;
+ case OT_P: // 32-bit or 48-bit pointer, depending on operand-size
+ // attribute.
+ if (operand_is_32_bits_)
+ operand_bytes_ += OS_48_BIT_POINTER;
+ else
+ operand_bytes_ += OS_32_BIT_POINTER;
+ break;
+ case OT_PS: // 128-bit packed single-precision floating-point data.
+ operand_bytes_ += OS_128_BIT_PACKED_SINGLE_PRECISION_FLOATING;
+ break;
+ case OT_Q: // Quadword, regardless of operand-size attribute.
+ operand_bytes_ += OS_QUAD_WORD;
+ break;
+ case OT_S: // 6-byte pseudo-descriptor.
+ operand_bytes_ += OS_PSEUDO_DESCRIPTOR;
+ break;
+ case OT_SD: // Scalar Double-Precision Floating-Point Value
+ case OT_PD: // Unaligned packed double-precision floating point value
+ operand_bytes_ += OS_DOUBLE_PRECISION_FLOATING;
+ break;
+ case OT_SS:
+ // Scalar element of a 128-bit packed single-precision
+ // floating data.
+ // We simply return enItUnknown since we don't have to support
+ // floating point
+ succeeded = false;
+ break;
+ case OT_V: // Word or doubleword, depending on operand-size attribute.
+ if (operand_is_32_bits_)
+ operand_bytes_ += OS_DOUBLE_WORD;
+ else
+ operand_bytes_ += OS_WORD;
+ break;
+ case OT_W: // Word, regardless of operand-size attribute.
+ operand_bytes_ += OS_WORD;
+ break;
+
+ // Can safely ignore these.
+ case OT_A: // Two one-word operands in memory or two double-word
+ // operands in memory
+ case OT_PI: // Quadword MMX technology register (e.g. mm0)
+ case OT_SI: // Doubleword integer register (e.g., eax)
+ break;
+
+ default:
+ break;
+ }
+ break;
+
+ default:
+ break;
+ }
+
+ return succeeded;
+}
+
+bool MiniDisassembler::ProcessModrm(unsigned char* start_byte,
+ unsigned int* size) {
+ // If we don't need to decode, we just return the size of the ModR/M
+ // byte (there is never a SIB byte in this case).
+ if (!should_decode_modrm_) {
+ (*size)++;
+ return true;
+ }
+
+ // We never care about the reg field, only the combination of the mod
+ // and r/m fields, so let's start by packing those fields together into
+ // 5 bits.
+ unsigned char modrm = (*start_byte);
+ unsigned char mod = modrm & 0xC0; // mask out top two bits to get mod field
+ modrm = modrm & 0x07; // mask out bottom 3 bits to get r/m field
+ mod = mod >> 3; // shift the mod field to the right place
+ modrm = mod | modrm; // combine the r/m and mod fields as discussed
+ mod = mod >> 3; // shift the mod field to bits 2..0
+
+ // Invariant: modrm contains the mod field in bits 4..3 and the r/m field
+ // in bits 2..0, and mod contains the mod field in bits 2..0
+
+ const ModrmEntry* modrm_entry = 0;
+ if (address_is_32_bits_)
+ modrm_entry = &s_ia32_modrm_map_[modrm];
+ else
+ modrm_entry = &s_ia16_modrm_map_[modrm];
+
+ // Invariant: modrm_entry points to information that we need to decode
+ // the ModR/M byte.
+
+ // Add to the count of operand bytes, if the ModR/M byte indicates
+ // that some operands are encoded in the instruction.
+ if (modrm_entry->is_encoded_in_instruction_)
+ operand_bytes_ += modrm_entry->operand_size_;
+
+ // Process the SIB byte if necessary, and return the count
+ // of ModR/M and SIB bytes.
+ if (modrm_entry->use_sib_byte_) {
+ (*size)++;
+ return ProcessSib(start_byte + 1, mod, size);
+ } else {
+ (*size)++;
+ return true;
+ }
+}
+
+bool MiniDisassembler::ProcessSib(unsigned char* start_byte,
+ unsigned char mod,
+ unsigned int* size) {
+ // get the mod field from the 2..0 bits of the SIB byte
+ unsigned char sib_base = (*start_byte) & 0x07;
+ if (0x05 == sib_base) {
+ switch (mod) {
+ case 0x00: // mod == 00
+ case 0x02: // mod == 10
+ operand_bytes_ += OS_DOUBLE_WORD;
+ break;
+ case 0x01: // mod == 01
+ operand_bytes_ += OS_BYTE;
+ break;
+ case 0x03: // mod == 11
+ // According to the IA-32 docs, there does not seem to be a disp
+ // value for this value of mod
+ default:
+ break;
+ }
+ }
+
+ (*size)++;
+ return true;
+}
+
+}; // namespace sidestep
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