[MIPS] Adding validator for MIPS architecture.

src/trusted/validator_mips/validator_tests.cc

+/*
+ * Copyright 2012 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 the MIPS validator
+ *
+ * These tests use the google-test framework (gtest for short) to exercise the
+ * MIPS validator.  The tests currently fall into two rough categories:
+ *  1. Simple method-level tests that exercise the validator's primitive
+ *     capabilities, and
+ *  2. Instruction pattern tests that run the entire validator.
+ *
+ * All instruction pattern tests use hand-assembled machine code fragments,
+ * embedded as byte arrays.  This is somewhat ugly, but deliberate: it isolates
+ * these tests from gas, which may be buggy or not installed.  It also lets us
+ * hand-craft malicious bit patterns that gas may refuse to produce.
+ *
+ * To write a new instruction pattern, or make sense of an existing one, use the
+ * MIPS.  Instructions in this file are written as
+ * 32-bit integers so the hex encoding matches the docs.
+ */
+
+#include <vector>
+#include <string>
+#include <sstream>
+
+#include "gtest/gtest.h"
+#include "native_client/src/include/nacl_macros.h"
+
+#include "native_client/src/trusted/validator_mips/validator.h"
+
+using std::vector;
+using std::string;
+using std::ostringstream;
+
+using nacl_mips_dec::Register;
+using nacl_mips_dec::RegisterList;
+using nacl_mips_dec::Instruction;
+
+using nacl_mips_val::SfiValidator;
+using nacl_mips_val::ProblemSink;
+using nacl_mips_val::CodeSegment;
+
+namespace {
+
+/*
+ * This test is written for MIPS
+ */
+
+typedef uint32_t mips_inst;
+
+/*
+ * We use these parameters to initialize the validator, below.  They are
+ * somewhat different from the parameters used in real NaCl systems, to test
+ * degrees of validator freedom that we don't currently exercise in prod.
+ */
+// Number of bytes in each bundle.
+static const uint32_t kBytesPerBundle = 16;
+// Limit code to 256MiB.
+static const uint32_t kCodeRegionSize = 0x10000000;
+// Limit data to 1GiB.
+static const uint32_t kDataRegionSize = 0x40000000;
+// Untrusted code must not write to t6,t7,t8.
+static const RegisterList kAbiReadOnlyRegisters =
+  nacl_mips_dec::kRegisterJumpMask + nacl_mips_dec::kRegisterLoadStoreMask
+  + nacl_mips_dec::kRegisterTls;
+// The stack pointer can be used for "free" loads and stores.
+static const RegisterList kAbiDataAddrRegisters = nacl_mips_dec::kRegisterStack;
+
+
+/*
+ * Support code
+ */
+
+// Simply records the arguments given to report_problem, below.
+struct ProblemRecord {
+  uint32_t vaddr;
+  nacl_mips_dec::SafetyLevel safety;
+  nacl::string problem_code;
+  uint32_t ref_vaddr;
+};
+
+// A ProblemSink that records all calls (implementation of the Spy pattern)
+class ProblemSpy : public ProblemSink {
+ public:
+  virtual void report_problem(uint32_t vaddr, nacl_mips_dec::SafetyLevel safety,
+      const nacl::string &problem_code, uint32_t ref_vaddr = 0) {
+    _problems.push_back(
+        (ProblemRecord) { vaddr, safety, problem_code, ref_vaddr });
+  }
+
+  /*
+   * We want *all* the errors that the validator produces.  Note that this means
+   * we're not testing the should_continue functionality.  This is probably
+   * okay.
+   */
+  virtual bool should_continue() { return true; }
+
+  vector<ProblemRecord> &get_problems() { return _problems; }
+
+ private:
+  vector<ProblemRecord> _problems;
+};
+
+/*
+ * Coordinates the fixture objects used by test cases below.  This is
+ * forward-declared to the greatest extent possible so we can get on to the
+ * important test stuff below.
+ */
+class ValidatorTests : public ::testing::Test {
+ protected:
+  ValidatorTests();
+
+  // Utility method for validating a sequence of bytes.
+  bool validate(const mips_inst *pattern,
+                size_t inst_count,
+                uint32_t start_addr,
+                ProblemSink *sink);
+
+  /*
+   * Tests a pattern that's expected to pass, at each possible bundle alignment.
+   * This also tries the pattern across bundle boundaries, and makes sure it
+   * fails.
+   * Note that this only works with 8-byte patterns, but that's all we have
+   * at the moment.
+   */
+  void validation_should_pass(const mips_inst *pattern,
+                              size_t inst_count,
+                              uint32_t base_addr,
+                              const string &msg);
+
+  /*
+   * Tests a pattern that is forbidden in the SFI model.
+   *
+   * Note that the 'msg1' and 'msg2' parameters are merely concatentated in the
+   * output.
+   */
+  vector<ProblemRecord> validation_should_fail(const mips_inst *pattern,
+                                               size_t inst_count,
+                                               uint32_t base_addr,
+                                               const string &msg);
+
+  SfiValidator _validator;
+};
+
+
+/*
+ * Primitive tests checking various constructor properties.  Any of these
+ * failing would be a very bad sign indeed.
+ */
+
+TEST_F(ValidatorTests, RecognizesDataAddressRegisters) {
+  /*
+   * Note that the logic below needs to be kept in sync with the definition
+   * of kAbiDataAddrRegisters at the top of this file.
+   *
+   * This test is pretty trivial -- we can exercise the data_address_register
+   * functionality more deeply with pattern tests below.
+   */
+  for (int i = 0; i < 31; i++) {
+    Register r(i);
+    if (r == nacl_mips_dec::kRegisterStack) {
+      EXPECT_TRUE(_validator.is_data_address_register(r))
+          << "Stack pointer must be a data address register.";
+    } else {
+      EXPECT_FALSE(_validator.is_data_address_register(r))
+          << "Only the stack pointer must be a data address register.";
+    }
+  }
+}
+
+/*
+ * Code validation tests
+ */
+
+// This is where untrusted code starts.  Most tests use this.
+static const uint32_t kDefaultBaseAddr = 0x20000;
+
+/*
+ * Here are examples of every form of safe stores permitted in a Native Client
+ * program.
+ */
+
+struct AnnotatedInstruction {
+  mips_inst inst;
+  const char *about;
+};
+
+static const AnnotatedInstruction examples_of_safe_stores[] = {
+  { 0xa1490200, "sb t1, 1024(t2) : store byte" },
+  { 0xad490200, "sw t1, 1024(t2) : store word" },
+  { 0xa5490200, "sh t1, 1024(t2) : store halfword" },
+  { 0xa9490200, "swl t1, 1024(t2) : store word left" },
+  { 0xb9490200, "swr t1, 1024(t2) : store word right" },
+};
+
+static const AnnotatedInstruction examples_of_safe_masks[] = {
+  { (10 << 21 | 15 << 16 | 10 << 11 | 36),
+    "and t2,t2,t7 : simple store masking" },
+};
+
+TEST_F(ValidatorTests, SafeMaskedStores) {
+  /*
+   * Produces examples of masked stores using the safe store table (above)
+   * and the list of possible masking instructions (above).
+   */
+
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_masks); m++) {
+    for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_stores);
+         s++) {
+      ostringstream message;
+      message << examples_of_safe_masks[m].about
+              << ", "
+              << examples_of_safe_stores[s].about;
+      mips_inst program[] = {
+        examples_of_safe_masks[m].inst,
+        examples_of_safe_stores[s].inst,
+      };
+      validation_should_pass(program,
+                             2,
+                             kDefaultBaseAddr,
+                             message.str());
+    }
+  }
+}
+
+TEST_F(ValidatorTests, IncorrectStores) {
+  /*
+   * Produces incorrect examples of masked stores using the safe store table
+   * (above)  and the list of possible masking instructions (above).
+   */
+
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_stores); m++) {
+     for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_masks); s++) {
+       ostringstream bad_message;
+       bad_message << examples_of_safe_stores[m].about
+                   << ", "
+                   << examples_of_safe_masks[s].about;
+       mips_inst bad_program[] = {
+           examples_of_safe_stores[m].inst,
+           examples_of_safe_masks[s].inst,
+       };
+
+       validation_should_fail(bad_program,
+                              2,
+                              kDefaultBaseAddr,
+                              bad_message.str());
+    }
+  }
+}
+
+static const AnnotatedInstruction examples_of_safe_jump_masks[] = {
+  { (10 << 21 | 14 << 16 | 10 << 11 | 36),
+    "and t2,t2,t6 : simple jump masking" },
+};
+
+static const AnnotatedInstruction examples_of_safe_jumps[] = {
+  { ((10<<21| 31 << 11 |9) ), "simple jump jalr t2" },
+  { (10<<21|8),               "simple jump jr t2" },
+};
+
+static const AnnotatedInstruction nop_instruction[] = {
+  {  0, "nop"},
+};
+
+TEST_F(ValidatorTests, SafeMaskedJumps) {
+  /*
+   * Produces examples of masked jumps using the safe jump table
+   * (above)  and the list of possible masking instructions (above).
+   */
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_jump_masks); m++) {
+    for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_jumps); s++) {
+      ostringstream message;
+      message << examples_of_safe_jump_masks[m].about
+              << ", "
+              << examples_of_safe_jumps[s].about;
+      mips_inst program[] = {
+        nop_instruction[0].inst,
+        examples_of_safe_jump_masks[m].inst,
+        examples_of_safe_jumps[s].inst,
+      };
+      validation_should_pass(program,
+                             3,
+                             kDefaultBaseAddr,
+                             message.str());
+    }
+  }
+}
+
+TEST_F(ValidatorTests, IncorrectJumps) {
+  /*
+   * Produces examples of incorrect jumps using the safe jump table
+   * (above)  and the list of possible masking instructions (above).
+   */
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_jumps); m++) {
+    for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_jump_masks);
+         s++) {
+      ostringstream bad_message;
+      bad_message << examples_of_safe_jumps[m].about
+                  << ", "
+                  << examples_of_safe_jump_masks[s].about;
+
+      mips_inst bad_program[] = {
+        examples_of_safe_jumps[m].inst,
+        examples_of_safe_jump_masks[s].inst,
+      };
+
+      validation_should_fail(bad_program,
+                         3,
+                         kDefaultBaseAddr,
+                         bad_message.str());
+    }
+  }
+}
+
+static const AnnotatedInstruction examples_of_safe_stack_masks[] = {
+  { (29 << 21 | 15 << 16 | 29 << 11 | 36),
+    "and sp,sp,t7 : simple stack masking" },
+};
+
+
+static const AnnotatedInstruction examples_of_safe_stack_ops[] = {
+  { (29<<21|8<<16|29<<11|32), "add  sp,sp,t0 : stack addition" },
+  { (29<<21|8<<16|29<<11|34), "sub  sp,sp,t0 : stack substraction" },
+};
+
+TEST_F(ValidatorTests, SafeMaskedStack) {
+  /*
+   * Produces examples of safe pseudo-ops on stack using the safe jump table
+   * and the list of possible masking instructions (above).
+   */
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_stack_ops); m++) {
+    for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_stack_masks);
+         s++) {
+      ostringstream message;
+      message << examples_of_safe_stack_ops[m].about
+              << ", "
+              << examples_of_safe_stack_masks[s].about;
+      mips_inst program[] = {
+         examples_of_safe_stack_ops[m].inst,
+         examples_of_safe_stack_masks[s].inst,
+      };
+      validation_should_pass(program,
+                             2,
+                             kDefaultBaseAddr,
+                             message.str());
+    }
+  }
+}
+
+TEST_F(ValidatorTests, IncorrectStackOps) {
+  /*
+   * Produces examples of incorrect pseudo-ops on stack using the safe jump
+   * table and the list of possible masking instructions (above).
+   */
+  for (unsigned m = 0; m < NACL_ARRAY_SIZE(examples_of_safe_stack_masks); m++) {
+    for (unsigned s = 0; s < NACL_ARRAY_SIZE(examples_of_safe_stack_ops); s++) {
+      ostringstream bad_message;
+      bad_message << examples_of_safe_stack_masks[m].about
+                  << ", "
+                  << examples_of_safe_stack_ops[s].about;
+      mips_inst bad_program[] = {
+        examples_of_safe_stack_masks[m].inst,
+        examples_of_safe_stack_ops[s].inst,
+        nop_instruction[0].inst
+      };
+
+      validation_should_fail(bad_program,
+                             3,
+                             kDefaultBaseAddr,
+                             bad_message.str());
+    }
+  }
+}
+
+/*
+ * Implementation of the ValidatorTests utility methods.  These are documented
+ * toward the top of this file.
+ */
+ValidatorTests::ValidatorTests()
+  : _validator(kBytesPerBundle,
+               kCodeRegionSize,
+               kDataRegionSize,
+               kAbiReadOnlyRegisters,
+               kAbiDataAddrRegisters) {}
+
+bool ValidatorTests::validate(const mips_inst *pattern,
+                              size_t inst_count,
+                              uint32_t start_addr,
+                              ProblemSink *sink) {
+  // We think in instructions; CodeSegment thinks in bytes.
+  const uint8_t *bytes = reinterpret_cast<const uint8_t *>(pattern);
+  CodeSegment segment(bytes, start_addr, inst_count * sizeof(mips_inst));
+
+  vector<CodeSegment> segments;
+  segments.push_back(segment);
+
+  return _validator.validate(segments, sink);
+}
+
+void ValidatorTests::validation_should_pass(const mips_inst *pattern,
+                                            size_t inst_count,
+                                            uint32_t base_addr,
+                                            const string &msg) {
+  ASSERT_TRUE(
+      _validator.bundle_for_address(base_addr).begin_addr() == base_addr)
+      << "base_addr parameter must be bundle-aligned";
+
+  ProblemSpy spy;
+
+  bool validation_result = validate(pattern, inst_count, base_addr, &spy);
+  ASSERT_TRUE(validation_result) << msg << " should pass at " << base_addr;
+  vector<ProblemRecord> &problems = spy.get_problems();
+  EXPECT_EQ(0U, problems.size()) << msg
+      << " should have no problems when located at " << base_addr;
+}
+
+vector<ProblemRecord> ValidatorTests::validation_should_fail(
+    const mips_inst *pattern,
+    size_t inst_count,
+    uint32_t base_addr,
+    const string &msg) {
+
+  ProblemSpy spy;
+  bool validation_result = validate(pattern, inst_count, base_addr, &spy);
+  EXPECT_FALSE(validation_result) << "Expected to fail: " << msg;
+
+  vector<ProblemRecord> problems = spy.get_problems();
+  // Would use ASSERT here, but cannot ASSERT in non-void functions :-(
+  EXPECT_NE(0U, problems.size())
+      << "Must report validation problems: " << msg;
+
+  // The rest of the checking is done in the caller.
+  return problems;
+}
+
+};  // anonymous namespace
+
+// Test driver function.
+int main(int argc, char *argv[]) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}