Start unit testing for functions in nc_inst_state.c

src/trusted/validator_x86/nc_inst_state_Tests.cc

+/*
+ * Copyright (c) 2011 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+// Unit tests for code in nc_inst_state.cc (and nc_inst_state_statics.c).
+
+// To turn on debugging of instruction decoding, change value of
+// DEBUGGING to 1.
+#define DEBUGGING 0
+
+#include "native_client/src/trusted/validator_x86/nc_inst_state.h"
+#include "native_client/src/include/nacl_macros.h"
+#include "gtest/gtest.h"
+
+// Include static functions, so that we can test.
+extern "C" {
+#include "native_client/src/trusted/validator_x86/nc_inst_state_statics.c"
+#include "native_client/src/trusted/validator_x86/RexPrefixes.h"
+};
+
+namespace {
+
+// Size of buffer to use to contain bytes of an instruction.
+static const size_t kBufferSize = 24;
+
+// Test harness for routines in nc_inst_state.c and nc_inst_state_statics.c.
+class NcInstStateTests : public ::testing::Test {
+ protected:
+  NcInstStateTests();
+  void SetUp();
+  void TearDown();
+
+  // Plant the given byte as the next input byte in the input buffer.
+  // Uses plant_index to determine the current end of the input buffer.
+  void Plant(uint8_t byte);
+
+  // Reset test state to a cleared input buffer, and (re)initialize
+  // the instruction state.
+  void Reset();
+
+  // Routine to add dummy calls so that compilation errors are not defined
+  // for static routines we have not tested.
+  void dummy();
+
+  // Reinitializes instruction state.
+  void ResetState();
+
+  // Resets the instruction pattern, and its flags to a default initial
+  // state.
+  void ResetInstPattern();
+
+  // Fills the input buffer with unlikely bytes, and initializes
+  // the reader to the beginning of the input buffer.
+  void ResetInput();
+
+  // Fills the input buffer with unlikely bytes, and set the plant
+  // index to the beginning of the input buffer.
+  void ResetInputBuffer();
+
+  // Verify that we have consumed the given number of prefix bytes, with
+  // the given number of rex prefixes, and that the prefix mask is set
+  // to the given mask.
+  //
+  // Parameters are:
+  //   num_bytes - Number of prefix bytes read.
+  //   num_rex   - Number of prefix bytes that were rex prefixes.
+  //   mask      - prefix mask that should have been generated.
+  void VerifyConsumedPrefixBytes(uint8_t num_bytes, uint8_t num_rex,
+                                 uint32_t mask);
+
+  // Run tests that verify that the call to NaClConsume0F38XXNaClInstBytes
+  // behaved as expected. Assumes the call was made through a call
+  // to NaClConsumeInstBytes.
+  void VerifyConsume0F38XXInstructions();
+
+  // Run tests that verify that the call to NaClConsume0F3AXXNaClInstBytes
+  // behaved as expected. Assumes the call was made through a call
+  // to NaClConsumeInstBytes.
+  void VerifyConsume0F3AXXInstructions();
+
+  // Run tests that verify that the call to NaClConsume0FXXNaClInstBytes
+  // behaved as expected.  Assumes the call was made through a call
+  // to NaClConsumeInstBytes.
+  void VerifyConsume0FXXInstructions();
+
+  // Run tests that verify that the call to NaClConsumeX87NaClInstBytes
+  // behaved as expected.  Assumes the call was made through a call
+  // to NaClConsumeInstBytes.
+  void VerifyConsumeX87Instructions();
+
+  // Run tests that verify that the call to NaClConsumeInstBytes consumed
+  // a single byte.
+  void VerifyConsumeOneByteInstructions();
+
+  // The instruction state to test.
+  NaClInstState* _state;
+  // The instruction iterator to use.
+  NaClInstIter* _iter;
+  // The memory segment to test.
+  NaClSegment _segment;
+  // The memory buffer in the memory segment.
+  uint8_t _buffer[kBufferSize];
+  // The instruction pattern to match against.
+  NaClInst _inst_pattern;
+  // The index of where the next planted byte should
+  // be added to the input buffer.
+  size_t _plant_index;
+};
+
+NcInstStateTests::NcInstStateTests() {
+  ResetInputBuffer();
+  NaClSegmentInitialize(_buffer, 0, kBufferSize, &_segment);
+}
+
+void NcInstStateTests::SetUp() {
+  _iter = NaClInstIterCreate(&_segment);
+  _state = NaClInstIterGetUndecodedState(_iter);
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::TearDown() {
+  NaClInstIterDestroy(_iter);
+}
+
+void NcInstStateTests::Reset() {
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::ResetState() {
+  NaClInstStateInit(_iter, _state);
+  ResetInstPattern();
+}
+
+void NcInstStateTests::ResetInstPattern() {
+  _inst_pattern.flags = NACL_EMPTY_IFLAGS;
+  _state->inst = &_inst_pattern;
+}
+
+void NcInstStateTests::ResetInputBuffer() {
+  // Fill input buffer with unlikely byte codes.
+  for (size_t i = 0; i < kBufferSize; ++i) {
+    _buffer[i] = 'X';
+  }
+  // Mark start point for planting data into
+  // the input buffer.
+  _plant_index = 0;
+}
+
+void NcInstStateTests::ResetInput() {
+  ResetInputBuffer();
+  NCInstBytesReset(&_state->bytes);
+}
+
+void NcInstStateTests::Plant(uint8_t byte) {
+  // TODO(Karl): Why do we get a compile time error if we use ASSERT.
+  ASSERT_LT(_plant_index, kBufferSize) <<
+      "Planted too many bytes, buffer overflow!";
+  _buffer[_plant_index++] = byte;
+  // Need to reset memory so that peek byte is set.
+  NCRemainingMemoryReset(_state->bytes.memory);
+}
+
+void NcInstStateTests::VerifyConsumedPrefixBytes(
+    uint8_t num_bytes, uint8_t num_rex, uint32_t mask) {
+  EXPECT_EQ(num_bytes, _state->bytes.length);
+  EXPECT_EQ(num_bytes, _state->num_prefix_bytes);
+  EXPECT_EQ(mask, _state->prefix_mask);
+  EXPECT_EQ(num_rex, _state->num_rex_prefixes);
+}
+
+void NcInstStateTests::VerifyConsume0F38XXInstructions() {
+  NaClInstPrefixDescriptor desc;
+  uint32_t prefix_mask = _state->prefix_mask;
+  // Note: This code assumes that the prefix mask may have
+  // other flags set before this routine is called. Hence,
+  // we must be careful when updating and checking the
+  // mask.
+
+  // Test for all possible XX.
+  for (int i = 0; i < NCDTABLESIZE; ++i) {
+    // Test successfully matching 0f38XX
+    _state->prefix_mask = prefix_mask;
+    Plant(0x0f);
+    Plant(0x38);
+    Plant(i);
+    NaClConsumeInstBytes(_state, &desc);
+    if (NaClHasBit(_state->prefix_mask, kPrefixREP)) {
+      EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+    } else if (NaClHasBit(_state->prefix_mask, kPrefixREPNE)) {
+      EXPECT_EQ(PrefixF20F38, desc.matched_prefix);
+    } else if (NaClHasBit(_state->prefix_mask, kPrefixDATA16)) {
+      EXPECT_EQ(Prefix660F38, desc.matched_prefix);
+    } else {
+      EXPECT_EQ(Prefix0F38, desc.matched_prefix);
+    }
+    EXPECT_EQ((uint8_t) i, desc.opcode_byte);
+    EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+    ResetInput();
+    ResetState();
+  }
+
+  // Now verify if that there isn't an XX byte, things short curcuit correctly.
+  _state->prefix_mask = prefix_mask;
+  Plant(0x0f);
+  Plant(0x38);
+  _state->length_limit = 2;
+  NaClConsumeInstBytes(_state, &desc);
+  EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+  EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::VerifyConsume0F3AXXInstructions() {
+  NaClInstPrefixDescriptor desc;
+  uint32_t prefix_mask = _state->prefix_mask;
+  // Note: This code assumes that the prefix mask may have
+  // other flags set before this routine is called. Hence,
+  // we must be careful when updating and checking the
+  // mask.
+
+  // Test for all possible XX.
+  for (int i = 0; i < NCDTABLESIZE; ++i) {
+    // Test successfully matching 0F3AXX
+    _state->prefix_mask = prefix_mask;
+    Plant(0x0f);
+    Plant(0x3a);
+    Plant(i);
+    NaClConsumeInstBytes(_state, &desc);
+    if (NaClHasBit(_state->prefix_mask, kPrefixREP) ||
+        NaClHasBit(_state->prefix_mask, kPrefixREPNE)) {
+      EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+    } else if (NaClHasBit(_state->prefix_mask, kPrefixDATA16)) {
+      EXPECT_EQ(Prefix660F3A, desc.matched_prefix);
+    } else {
+      EXPECT_EQ(Prefix0F3A, desc.matched_prefix);
+    }
+    EXPECT_EQ((uint8_t) i, desc.opcode_byte);
+    EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+    ResetInput();
+    ResetState();
+  }
+
+  // Now verify if that there isn't an XX byte, things short curcuit correctly.
+  _state->prefix_mask = prefix_mask;
+  Plant(0x0f);
+  Plant(0x3a);
+  _state->length_limit = 2;
+  NaClConsumeInstBytes(_state, &desc);
+  EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+  EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::VerifyConsume0FXXInstructions() {
+  NaClInstPrefixDescriptor desc;
+  uint32_t prefix_mask = _state->prefix_mask;
+  // Note: This code assumes that the prefix mask may have
+  // other flags set before this routine is called. Hence,
+  // we must be careful when updating and checking the
+  // mask.
+
+  // Test for all possible XX.
+  for (int i = 0; i < NCDTABLESIZE; ++i) {
+    if (i == 0x38 || i == 0x3a) continue;  // exclude special lookup cases.
+    // Test successfully matching 0fXX
+    _state->prefix_mask = prefix_mask;
+    Plant(0x0f);
+    Plant(i);
+    NaClConsumeInstBytes(_state, &desc);
+    if (NaClHasBit(_state->prefix_mask, kPrefixREP)) {
+      if (NaClHasBit(_state->prefix_mask, kPrefixREPNE)) {
+        EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+      } else {
+        EXPECT_EQ(PrefixF30F, desc.matched_prefix);
+      }
+    } else if (NaClHasBit(_state->prefix_mask, kPrefixREPNE)) {
+      EXPECT_EQ(PrefixF20F, desc.matched_prefix);
+    } else if (NaClHasBit(_state->prefix_mask, kPrefixDATA16)) {
+      EXPECT_EQ(Prefix660F, desc.matched_prefix);
+    } else {
+      EXPECT_EQ(Prefix0F, desc.matched_prefix);
+    }
+    EXPECT_EQ((uint8_t) i, desc.opcode_byte);
+    EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+    ResetInput();
+    ResetState();
+  }
+
+  // Now verify if that there isn't an XX byte, things short curcuit correctly.
+  _state->prefix_mask = prefix_mask;
+  Plant(0x0f);
+  _state->length_limit = 1;
+  NaClConsumeInstBytes(_state, &desc);
+  EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+  EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::VerifyConsumeX87Instructions() {
+  NaClInstPrefixDescriptor desc;
+  uint32_t prefix_mask = _state->prefix_mask;
+  // Note: This code assumes that the prefix mask may have
+  // other flags set before this routine is called. Hence,
+  // we must be careful when updating and checking the
+  // mask.
+
+  // Try for all possible x87 initial bytes.
+  for (uint8_t byte1 = 0xD8; byte1 <= 0xDF; ++byte1) {
+    // Test for all possible XX.
+    for (int i = 0; i < NCDTABLESIZE; ++i) {
+      // Test successfully matching byte1 XX
+      _state->prefix_mask = prefix_mask;
+      Plant(byte1);
+      Plant(i);
+      NaClConsumeInstBytes(_state, &desc);
+      NaClInstPrefix prefix = (NaClInstPrefix) (PrefixD8 + (byte1 - 0xD8));
+      EXPECT_EQ(prefix, desc.matched_prefix);
+      EXPECT_EQ((uint8_t) i, desc.opcode_byte);
+      EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+      ResetInput();
+      ResetState();
+    }
+
+    // Now verify if that there isn't an XX byte, things short curcuit
+    // correctly. For this context, it should return matching a single
+    // byte instruction with no prefix.
+    _state->prefix_mask = prefix_mask;
+    Plant(byte1);
+    _state->length_limit = 1;
+    NaClConsumeInstBytes(_state, &desc);
+    EXPECT_EQ(NoPrefix, desc.matched_prefix);
+    EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+    ResetInput();
+    ResetState();
+  }
+}
+
+void NcInstStateTests::VerifyConsumeOneByteInstructions() {
+  NaClInstPrefixDescriptor desc;
+  uint32_t prefix_mask = _state->prefix_mask;
+  // Note: This code assumes that the prefix mask may have
+  // other flags set before this routine is called. Hence,
+  // we must be careful when updating and checking the
+  // mask.
+
+  // Test for all possible XX.
+  for (int i = 0; i < NCDTABLESIZE; ++i) {
+    // exclude special lookup cases.
+    if (i == 0x0f || (i >= 0xD8 && i <= 0xDF)) continue;
+    // Test successfully XX
+    _state->prefix_mask = prefix_mask;
+    Plant(i);
+    NaClConsumeInstBytes(_state, &desc);
+    EXPECT_EQ(NoPrefix, desc.matched_prefix);
+    EXPECT_EQ((uint8_t) i, desc.opcode_byte);
+    EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+    ResetInput();
+    ResetState();
+  }
+
+  // Now verify if that there isn't an XX byte, things short curcuit correctly.
+  _state->prefix_mask = prefix_mask;
+  _state->length_limit = 0;
+  NaClConsumeInstBytes(_state, &desc);
+  EXPECT_EQ(NaClInstPrefixEnumSize, desc.matched_prefix);
+  EXPECT_EQ((uint8_t) 0, desc.next_length_adjustment);
+  ResetInput();
+  ResetState();
+}
+
+void NcInstStateTests::dummy() {
+  NaClInstPrefixDescriptor prefix_desc;
+  NaClConsumeAndCheckOperandSize(_state);
+  NaClConsumeAndCheckAddressSize(_state);
+  NaClConsumeModRm(_state);
+  NaClConsumeSib(_state);
+  NaClConsumeDispBytes(_state);
+  NaClConsumeImmediateBytes(_state);
+  NaClValidatePrefixFlags(_state);
+  NaClClearInstState(_state, 0);
+  NaClGetNextInstCandidates(_state, &prefix_desc, NULL);
+  NaClConsumeOpcodeSequence(_state);
+}
+
+// Test function NaClExtactOpSize, which returns the expected
+// number of bytes to represent operands.
+TEST_F(NcInstStateTests, TestExtractOpSize) {
+  // Test 32 amd 64 bit assumptions.
+
+  // Test explicit size restrictors. Note: Only b should make a difference
+  // in matching the pattern, since v, w, and o are used as excluders rather
+  // than for matching (i.e. don't match unless operand size should be
+  // 1).
+  _inst_pattern.flags = NACL_IFLAG(OperandSize_b);
+  EXPECT_EQ(1, NaClExtractOpSize(_state)) << "bytes are of size 1\n";
+  _inst_pattern.flags = NACL_IFLAG(OperandSize_w);
+  EXPECT_EQ(4, NaClExtractOpSize(_state));
+  _inst_pattern.flags = NACL_IFLAG(OperandSize_v);
+  EXPECT_EQ(4, NaClExtractOpSize(_state));
+  _inst_pattern.flags = NACL_IFLAG(OperandSize_o);
+  EXPECT_EQ(4, NaClExtractOpSize(_state));
+  ResetState();
+
+  // See if we interpret the Data16 prefix correctly.
+  _state->prefix_mask = kPrefixDATA16;
+  EXPECT_EQ(2, NaClExtractOpSize(_state));
+  _inst_pattern.flags = NACL_IFLAG(SizeIgnoresData16);
+  EXPECT_EQ(4, NaClExtractOpSize(_state));
+  ResetState();
+
+  // Test strictly 64-bit assumptions.
+  if (NACL_TARGET_SUBARCH == 64) {
+    // Check that we return a size 64 if the REX.W bit is set.
+    for (uint8_t rex = NaClRexMin; rex <= NaClRexMax; ++rex) {
+      _state->rexprefix = rex;
+      if (NaClRexW(rex)) {
+        EXPECT_EQ(8, NaClExtractOpSize(_state));
+      } else {
+        EXPECT_EQ(4, NaClExtractOpSize(_state));
+      }
+    }
+    ResetState();
+
+    // If we force the size to 64, it returns size 64.
+    _inst_pattern.flags = NACL_IFLAG(OperandSizeForce64);
+    EXPECT_EQ(8, NaClExtractOpSize(_state));
+    ResetState();
+
+    // Now repeat the tests, but with the default size set to 64 bits,
+    // which replaces the default size of 4 with 8.
+
+    // Test explicit size restrictors. Note: Only b should make a difference
+    // in matching the pattern, since v, w, and o are used as excluders rather
+    // than for matching (i.e. don't match unless operand size matches).
+    _inst_pattern.flags =
+        NACL_IFLAG(OperandSize_b) | NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(1, NaClExtractOpSize(_state)) << "bytes are of size 1\n";
+    _inst_pattern.flags =
+        NACL_IFLAG(OperandSize_w) | NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(8, NaClExtractOpSize(_state));
+    _inst_pattern.flags =
+        NACL_IFLAG(OperandSize_v) | NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(8, NaClExtractOpSize(_state));
+    _inst_pattern.flags =
+        NACL_IFLAG(OperandSize_o) | NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(8, NaClExtractOpSize(_state));
+    ResetState();
+
+    // See if we interpret the Data16 prefix correctly.
+    _state->prefix_mask = kPrefixDATA16;
+    _inst_pattern.flags = NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(2, NaClExtractOpSize(_state));
+    _inst_pattern.flags =
+        NACL_IFLAG(SizeIgnoresData16) | NACL_IFLAG(OperandSizeDefaultIs64);
+    EXPECT_EQ(8, NaClExtractOpSize(_state));
+    ResetState();
+
+    // Check that we return a size 64 independent of the REX.W bit.
+    _inst_pattern.flags = NACL_IFLAG(OperandSizeDefaultIs64);
+    for (uint8_t rex = NaClRexMin; rex <= NaClRexMax; ++rex) {
+      _state->rexprefix = rex;
+      EXPECT_EQ(8, NaClExtractOpSize(_state));
+    }
+  }
+}
+
+// Test function NaClExtractAddressSize, which returns the expected
+// number of bits in operands corresponding to addresses.
+TEST_F(NcInstStateTests, TestExtractAddressSize) {
+  // Depending on whether we are in 32/64 bit mode, there are two
+  // different address sizes.
+  int small_address;
+  int large_address;
+  if (NACL_TARGET_SUBARCH == 64) {
+    small_address = 32;
+    large_address = 64;
+  } else {
+    small_address = 16;
+    large_address = 32;
+  }
+  EXPECT_EQ(large_address, NaClExtractAddressSize(_state));
+  _state->prefix_mask = kPrefixADDR16;
+  EXPECT_EQ(small_address, NaClExtractAddressSize(_state));
+}
+
+extern "C" {
+  // Define acceptable prefixes, and the corresponding flag that
+  // should be set (except for rex prefixes).
+  static const struct  prefix_pairs {
+    uint8_t byte;
+    uint32_t mask;
+  } prefix_values[] = {
+    {kValueSEGCS, kPrefixSEGCS},
+    {kValueSEGSS, kPrefixSEGSS},
+    {kValueSEGFS, kPrefixSEGFS},
+    {kValueSEGGS, kPrefixSEGGS},
+    {kValueDATA16, kPrefixDATA16},
+    {kValueADDR16, kPrefixADDR16},
+    {kValueREPNE, kPrefixREPNE},
+    {kValueREP, kPrefixREP},
+    {kValueLOCK, kPrefixLOCK},
+    {kValueSEGES, kPrefixSEGES},
+    {kValueSEGDS, kPrefixSEGDS}
+  };
+};
+
+// Test function NaClConsumePrefixBytes to verify it only recognizes
+// valid prefix values.
+TEST_F(NcInstStateTests, ConsumesKnownPrefixBytes) {
+  for (int byte = 0; byte < NCDTABLESIZE; ++byte) {
+    bool byte_categorized = false;
+    Plant(byte);
+    EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+    if (NACL_TARGET_SUBARCH == 64 &&
+        byte >= NaClRexMin && byte <= NaClRexMax) {
+      VerifyConsumedPrefixBytes(1, 1, kPrefixREX);
+      byte_categorized = true;
+    } else {
+      for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+        if (byte == prefix_values[j].byte) {
+          VerifyConsumedPrefixBytes(1, 0, prefix_values[j].mask);
+          byte_categorized = true;
+        }
+      }
+    }
+    if (!byte_categorized) {
+      VerifyConsumedPrefixBytes(0, 0, 0);
+    }
+    ResetInput();
+    ResetState();
+  }
+}
+
+// Test function NaClConsumePrefixBytes to verify it can recognize
+// pairs of non-rex prefix bytes.
+TEST_F(NcInstStateTests, ConsumeNonRexPrefixBytePairs) {
+  // First try some pairs within non-rex prefix bytes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(prefix_values) - 1; ++i) {
+    Plant(prefix_values[i].byte);
+    Plant(prefix_values[i+1].byte);
+    EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+    VerifyConsumedPrefixBytes(2, 0,
+                              prefix_values[i].mask | prefix_values[i+1].mask);
+    ResetInput();
+    ResetState();
+  }
+}
+
+// Test Function NaClConsumePrefixBytes to verify it can recognize
+// a Rex prefix followed by a non-rex prefix.
+TEST_F(NcInstStateTests, ConsumeRexThenNonRexPrefixPairs) {
+  if (NACL_TARGET_SUBARCH == 64) {
+    // Try some pairs where one is rex.
+    for (size_t i = 0; i < NACL_ARRAY_SIZE(prefix_values); ++i) {
+      for (size_t rex = NaClRexMin; rex <= NaClRexMax; ++rex) {
+        Plant(rex);
+        Plant(prefix_values[i].byte);
+        EXPECT_FALSE(NaClConsumePrefixBytes(_state));
+        VerifyConsumedPrefixBytes(2, 1, prefix_values[i].mask | kPrefixREX);
+        ResetInput();
+        ResetState();
+      }
+    }
+  }
+}
+
+// Test Function NaClConsumePrefixBytes to verify it can recognize
+// a non-rex prefix, followed by a rex prefix.
+TEST_F(NcInstStateTests, ConsumeNonRexThenRexPrefixPairs) {
+  if (NACL_TARGET_SUBARCH == 64) {
+    // Try some pairs where one is rex.
+    for (size_t i = 0; i < NACL_ARRAY_SIZE(prefix_values); ++i) {
+      for (size_t rex = NaClRexMin; rex <= NaClRexMax; ++rex) {
+        Plant(prefix_values[i].byte);
+        Plant(rex);
+        EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+        VerifyConsumedPrefixBytes(2, 1, prefix_values[i].mask | kPrefixREX);
+        ResetInput();
+        ResetState();
+      }
+    }
+  }
+}
+
+// Test function NaClConsumePrefixBytes on multiple rex prefixes.
+TEST_F(NcInstStateTests, ConsumeMultipleRexPrefixes) {
+  if (NACL_TARGET_SUBARCH == 64) {
+    for (size_t rex1 = NaClRexMin; rex1 <= NaClRexMax; ++rex1) {
+      for (size_t rex2 = NaClRexMin; rex2 <= NaClRexMax; ++rex2) {
+        Plant(rex1);
+        Plant(rex2);
+        EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+        VerifyConsumedPrefixBytes(2, 2, kPrefixREX);
+        ResetInput();
+        ResetState();
+      }
+    }
+  }
+}
+
+// Test function NaClConsumePrefixBytes to see if we allow multiple
+// copies of the same (non-rex) prefix.
+TEST_F(NcInstStateTests, ConsumeDuplicatePrefixes) {
+  // Try with non rex prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(prefix_values); ++i) {
+    Plant(prefix_values[i].byte);
+    Plant(prefix_values[i].byte);
+    EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+    VerifyConsumedPrefixBytes(2, 0, prefix_values[i].mask);
+    ResetInput();
+    ResetState();
+  }
+}
+
+// Test if we can recognize 14 prefix bytes.
+TEST_F(NcInstStateTests, Consume14PrefixBytes) {
+  for (int i = 0; i < 14; ++i) {
+    Plant(kValueDATA16);
+  }
+  EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+  VerifyConsumedPrefixBytes(14, 0, kPrefixDATA16);
+}
+
+// Test that we can't accept 15 prefix bytes.
+TEST_F(NcInstStateTests, Consume15PrefixBytes) {
+  for (int i = 0; i < 15; ++i) {
+    Plant(kValueDATA16);
+  }
+  EXPECT_TRUE(NaClConsumePrefixBytes(_state));
+  EXPECT_EQ((uint8_t) 14, _state->bytes.length);
+}
+
+// Defines the set of prefix bytes that effect multibyte instructions
+// (i.e. REP, REPNE,  and DATA16), and all possible combinations of
+// these prefixes.
+static const uint32_t kMultibytePrefixes[] = {
+  0,
+  kPrefixREP,
+  kPrefixREP | kPrefixREPNE,
+  kPrefixREP | kPrefixREPNE | kPrefixDATA16,
+  kPrefixREPNE,
+  kPrefixREPNE | kPrefixDATA16,
+  kPrefixDATA16
+};
+
+// Test function NaClConsume0F38XXNaClInstBytes, as called through
+// function NaClConsumeInstBytes.
+TEST_F(NcInstStateTests, ConsumeOF38XXInstructions) {
+  // First try effects of just multibyte prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(kMultibytePrefixes); ++i) {
+    _state->prefix_mask = kMultibytePrefixes[i];
+    VerifyConsume0F38XXInstructions();
+
+    // Verify that adding a rex prefix don't effect anything.
+    _state->prefix_mask = kMultibytePrefixes[i] | kPrefixREX;
+    VerifyConsume0F38XXInstructions();
+
+    // Now try adding other possible prefixes to see if they break anything.
+    for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask;
+      VerifyConsume0F38XXInstructions();
+
+      // Verify that adding a rex prefix don't effect anything.
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask
+          | kPrefixREX;
+      VerifyConsume0F38XXInstructions();
+    }
+  }
+}
+
+// Test function NaClConsume0F3AXXNaClInstBytes, as called through
+// function NaClConsumeInstBytes.
+TEST_F(NcInstStateTests, ConsumeOF3AXXInstructions) {
+  // First try effects of just multibyte prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(kMultibytePrefixes); ++i) {
+    _state->prefix_mask = kMultibytePrefixes[i];
+    VerifyConsume0F3AXXInstructions();
+
+    // Verify that adding a rex prefix don't effect anything.
+    _state->prefix_mask = kMultibytePrefixes[i] | kPrefixREX;
+    VerifyConsume0F3AXXInstructions();
+
+    // Now try adding other possible prefixes to see if they break anything.
+    for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask;
+      VerifyConsume0F3AXXInstructions();
+
+      // Verify that adding a rex prefix don't effect anything.
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask
+          | kPrefixREX;
+      VerifyConsume0F3AXXInstructions();
+    }
+  }
+}
+
+// Test function NaClConsume0FXXNaClInstBytes, as called through
+// function NaClConsumeInstBytes.
+TEST_F(NcInstStateTests, ConsumeOFXXInstructions) {
+  // First try effects of just multibyte prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(kMultibytePrefixes); ++i) {
+    _state->prefix_mask = kMultibytePrefixes[i];
+    VerifyConsume0FXXInstructions();
+
+    // Verify that adding a rex prefix don't effect anything.
+    _state->prefix_mask = kMultibytePrefixes[i] | kPrefixREX;
+    VerifyConsume0FXXInstructions();
+
+    // Now try adding other possible prefixes to see if they break anything.
+    for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask;
+      VerifyConsume0FXXInstructions();
+
+      // Verify that adding a rex prefix don't effect anything.
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask
+          | kPrefixREX;
+      VerifyConsume0FXXInstructions();
+    }
+  }
+}
+
+// Test function NaClConsumeX87NaClInstBytes, as called through
+// function NaClConsumeInstBytes.
+TEST_F(NcInstStateTests, ConsumeX87Instructions) {
+  // First try effects of just multibyte prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(kMultibytePrefixes); ++i) {
+    _state->prefix_mask = kMultibytePrefixes[i];
+    VerifyConsumeX87Instructions();
+
+    // Verify that adding a rex prefix don't effect anything.
+    _state->prefix_mask = kMultibytePrefixes[i] | kPrefixREX;
+    VerifyConsumeX87Instructions();
+
+    // Now try adding other possible prefixes to see if they break anything.
+    for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask;
+      VerifyConsumeX87Instructions();
+
+      // Verify that adding a rex prefix don't effect anything.
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask
+          | kPrefixREX;
+      VerifyConsumeX87Instructions();
+    }
+  }
+}
+
+// Test function NaClConsumeInstBytes for one byte instruction values.
+TEST_F(NcInstStateTests, ConsumeOneByteInstructions) {
+  // First try effects of just multibyte prefixes.
+  for (size_t i = 0; i < NACL_ARRAY_SIZE(kMultibytePrefixes); ++i) {
+    _state->prefix_mask = kMultibytePrefixes[i];
+    VerifyConsumeOneByteInstructions();
+
+    // Verify that adding a rex prefix don't effect anything.
+    _state->prefix_mask = kMultibytePrefixes[i] | kPrefixREX;
+    VerifyConsumeOneByteInstructions();
+
+    // Now try adding other possible prefixes to see if they break anything.
+    for (size_t j = 0; j < NACL_ARRAY_SIZE(prefix_values); ++j) {
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask;
+      VerifyConsumeOneByteInstructions();
+
+      // Verify that adding a rex prefix don't effect anything.
+      _state->prefix_mask = kMultibytePrefixes[i] | prefix_values[i].mask
+          | kPrefixREX;
+      VerifyConsumeOneByteInstructions();
+    }
+  }
+}
+
+};  // anonymous namespace
+
+int main(int argc, char *argv[]) {
+  NaClLogModuleInit();
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}