stackwalker_mips_unittest.cc

// Copyright (c) 2013, Google Inc.

// All rights reserved.

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// Original author: Gordana Cmiljanovic <gordana.cmiljanovic@imgtec.com>

// stackwalker_mips_unittest.cc: Unit tests for StackwalkerMIPS class.

#include <string.h>

#include <string>

#include <vector>

#include "breakpad_googletest_includes.h"

#include "common/test_assembler.h"

#include "common/using_std_string.h"

#include "google_breakpad/common/minidump_format.h"

#include "google_breakpad/processor/basic_source_line_resolver.h"

#include "google_breakpad/processor/call_stack.h"

#include "google_breakpad/processor/code_module.h"

#include "google_breakpad/processor/source_line_resolver_interface.h"

#include "google_breakpad/processor/stack_frame_cpu.h"

#include "processor/stackwalker_unittest_utils.h"

#include "processor/stackwalker_mips.h"

#include "processor/windows_frame_info.h"

using google_breakpad::BasicSourceLineResolver;

using google_breakpad::CallStack;

using google_breakpad::CodeModule;

using google_breakpad::StackFrameSymbolizer;

using google_breakpad::StackFrame;

using google_breakpad::StackFrameMIPS;

using google_breakpad::Stackwalker;

using google_breakpad::StackwalkerMIPS;

using google_breakpad::SystemInfo;

using google_breakpad::WindowsFrameInfo;

using google_breakpad::test_assembler::kLittleEndian;

using google_breakpad::test_assembler::Label;

using google_breakpad::test_assembler::Section;

using std::vector;

using testing::_;

using testing::AnyNumber;

using testing::Return;

using testing::SetArgumentPointee;

using testing::Test;

class StackwalkerMIPSFixture {

 public:

  StackwalkerMIPSFixture()

    : stack_section(kLittleEndian),

      // Give the two modules reasonable standard locations and names

      // for tests to play with.

      module1(0x00400000, 0x10000, "module1", "version1"),

      module2(0x00500000, 0x10000, "module2", "version2") {

    // Identify the system as a Linux system.

    system_info.os = "Linux";

    system_info.os_short = "linux";

    system_info.os_version = "Observant Opossum";  // Jealous Jellyfish

    system_info.cpu = "mips";

    system_info.cpu_info = "";

    // Put distinctive values in the raw CPU context.

    BrandContext(&raw_context);

    // Create some modules with some stock debugging information.

    modules.Add(&module1);

    modules.Add(&module2);

    // By default, none of the modules have symbol info; call

    // SetModuleSymbols to override this.

    EXPECT_CALL(supplier, GetCStringSymbolData(_, _, _, _, _))

      .WillRepeatedly(Return(MockSymbolSupplier::NOT_FOUND));

    // Avoid GMOCK WARNING "Uninteresting mock function call - returning

    // directly" for FreeSymbolData().

    EXPECT_CALL(supplier, FreeSymbolData(_)).Times(AnyNumber());

    // Reset max_frames_scanned since it's static.

    Stackwalker::set_max_frames_scanned(1024);

  // Set the Breakpad symbol information that supplier should return for

  // MODULE to INFO.

  void SetModuleSymbols(MockCodeModule* module, const string& info) {

    size_t buffer_size;

    char* buffer = supplier.CopySymbolDataAndOwnTheCopy(info, &buffer_size);

    EXPECT_CALL(supplier, GetCStringSymbolData(module, &system_info, _, _, _))

      .WillRepeatedly(DoAll(SetArgumentPointee<3>(buffer),

                            SetArgumentPointee<4>(buffer_size),

                            Return(MockSymbolSupplier::FOUND)));

  // Populate stack_region with the contents of stack_section. Use

  // stack_section.start() as the region's starting address.

  void RegionFromSection() {

    string contents;

    ASSERT_TRUE(stack_section.GetContents(&contents));

    stack_region.Init(stack_section.start().Value(), contents);

  // Fill RAW_CONTEXT with pseudo-random data, for round-trip checking.

  void BrandContext(MDRawContextMIPS* raw_context) {

    uint8_t x = 173;

    for (size_t i = 0; i < sizeof(*raw_context); ++i)

      reinterpret_cast<uint8_t*>(raw_context)[i] = (x += 17);

  SystemInfo system_info;

  MDRawContextMIPS raw_context;

  Section stack_section;

  MockMemoryRegion stack_region;

  MockCodeModule module1;

  MockCodeModule module2;

  MockCodeModules modules;

  MockSymbolSupplier supplier;

  BasicSourceLineResolver resolver;

  CallStack call_stack;

  const vector<StackFrame*>* frames;

};

class SanityCheck: public StackwalkerMIPSFixture, public Test { };

TEST_F(SanityCheck, NoResolver) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  stack_section.start() = 0x80000000;

  stack_section.D32(0).D32(0x0);

  RegionFromSection();

  raw_context.epc = 0x00400020;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

  StackFrameSymbolizer frame_symbolizer(NULL, NULL);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                        &frame_symbolizer);

  // This should succeed, even without a resolver or supplier.

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(1U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(1U, frames->size());

  StackFrameMIPS* frame = static_cast<StackFrameMIPS*>(frames->at(0));

  // Check that the values from the original raw context made it

  // through to the context in the stack frame.

  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));

class GetContextFrame: public StackwalkerMIPSFixture, public Test { };

TEST_F(GetContextFrame, Simple) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  stack_section.start() = 0x80000000;

  stack_section.D32(0).D32(0x0);

  RegionFromSection();

  raw_context.epc = 0x00400020;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(1U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  StackFrameMIPS* frame = static_cast<StackFrameMIPS*>(frames->at(0));

  // Check that the values from the original raw context made it

  // through to the context in the stack frame.

  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));

// The stackwalker should be able to produce the context frame even

// without stack memory present.

TEST_F(GetContextFrame, NoStackMemory) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  raw_context.epc = 0x00400020;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, NULL, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(1U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  StackFrameMIPS* frame = static_cast<StackFrameMIPS*>(frames->at(0));

  // Check that the values from the original raw context made it

  // through to the context in the stack frame.

  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));

class GetCallerFrame: public StackwalkerMIPSFixture, public Test { };

TEST_F(GetCallerFrame, ScanWithoutSymbols) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  // When the stack walker resorts to scanning the stack,

  // only addresses located within loaded modules are

  // considered valid return addresses.

  // Force scanning through three frames to ensure that the

  // stack pointer is set properly in scan-recovered frames.

  stack_section.start() = 0x80000000;

  uint32_t return_address1 = 0x00400100;

  uint32_t return_address2 = 0x00400900;

  Label frame1_sp, frame2_sp;

  stack_section

    // frame 0

    .Append(16, 0)                      // space

    .D32(0x00490000)                    // junk that's not

    .D32(0x00600000)                    // a return address

    .D32(frame1_sp)                     // stack pointer

    .D32(return_address1)               // actual return address

    // frame 1

    .Mark(&frame1_sp)

    .Append(16, 0)                      // space

    .D32(0xF0000000)                    // more junk

    .D32(0x0000000D)

    .D32(frame2_sp)                     // stack pointer

    .D32(return_address2)               // actual return address

    // frame 2

    .Mark(&frame2_sp)

    .Append(32, 0);                     // end of stack

  RegionFromSection();

  raw_context.epc = 0x00405510;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = stack_section.start().Value();

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = return_address1;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(1U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(3U, frames->size());

  StackFrameMIPS* frame0 = static_cast<StackFrameMIPS*>(frames->at(0));

  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);

  ASSERT_EQ(StackFrameMIPS::CONTEXT_VALID_ALL, frame0->context_validity);

  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameMIPS* frame1 = static_cast<StackFrameMIPS*>(frames->at(1));

  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);

  ASSERT_EQ((StackFrameMIPS::CONTEXT_VALID_PC |

             StackFrameMIPS::CONTEXT_VALID_SP |

             StackFrameMIPS::CONTEXT_VALID_FP |

             StackFrameMIPS::CONTEXT_VALID_RA),

            frame1->context_validity);

  EXPECT_EQ(return_address1 - 2 * sizeof(return_address1), frame1->context.epc);

  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_MIPS_REG_SP]);

  StackFrameMIPS* frame2 = static_cast<StackFrameMIPS*>(frames->at(2));

  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame2->trust);

  ASSERT_EQ((StackFrameMIPS::CONTEXT_VALID_PC |

             StackFrameMIPS::CONTEXT_VALID_SP |

             StackFrameMIPS::CONTEXT_VALID_FP |

             StackFrameMIPS::CONTEXT_VALID_RA),

            frame2->context_validity);

  EXPECT_EQ(return_address2 - 2 * sizeof(return_address2), frame2->context.epc);

  EXPECT_EQ(frame2_sp.Value(), frame2->context.iregs[MD_CONTEXT_MIPS_REG_SP]);

TEST_F(GetCallerFrame, ScanWithFunctionSymbols) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  // During stack scanning, if a potential return address

  // is located within a loaded module that has symbols,

  // it is only considered a valid return address if it

  // lies within a function's bounds.

  stack_section.start() = 0x80000000;

  uint32_t return_address = 0x00500200;

  Label frame1_sp;

  stack_section

    // frame 0

    .Append(16, 0)                      // space

    .D32(0x00490000)                    // junk that's not

    .D32(0x00600000)                    // a return address

    .D32(0x00401000)                    // a couple of plausible addresses

    .D32(0x0050F000)                    // that are not within functions

    .D32(frame1_sp)                     // stack pointer

    .D32(return_address)                // actual return address

    // frame 1

    .Mark(&frame1_sp)

    .Append(32, 0);                     // end of stack

  RegionFromSection();

  raw_context.epc = 0x00400200;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = stack_section.start().Value();

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = return_address;

  SetModuleSymbols(&module1,

                   // The youngest frame's function.

                   "FUNC 100 400 10 monotreme\n");

  SetModuleSymbols(&module2,

                   // The calling frame's function.

                   "FUNC 100 400 10 marsupial\n");

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(0U, modules_without_symbols.size());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(2U, frames->size());

  StackFrameMIPS* frame0 = static_cast<StackFrameMIPS*>(frames->at(0));

  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);

  ASSERT_EQ(StackFrameMIPS::CONTEXT_VALID_ALL, frame0->context_validity);

  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  EXPECT_EQ("monotreme", frame0->function_name);

  EXPECT_EQ(0x00400100U, frame0->function_base);

  StackFrameMIPS* frame1 = static_cast<StackFrameMIPS*>(frames->at(1));

  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);

  ASSERT_EQ((StackFrameMIPS::CONTEXT_VALID_PC |

             StackFrameMIPS::CONTEXT_VALID_SP |

             StackFrameMIPS::CONTEXT_VALID_FP |

             StackFrameMIPS::CONTEXT_VALID_RA),

            frame1->context_validity);

  EXPECT_EQ(return_address - 2 * sizeof(return_address), frame1->context.epc);

  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_MIPS_REG_SP]);

  EXPECT_EQ("marsupial", frame1->function_name);

  EXPECT_EQ(0x00500100U, frame1->function_base);

TEST_F(GetCallerFrame, CheckStackFrameSizeLimit) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  // If the stackwalker resorts to stack scanning, it will scan only

  // 1024 bytes of stack which correspondes to maximum size of stack frame.

  stack_section.start() = 0x80000000;

  uint32_t return_address1 = 0x00500100;

  uint32_t return_address2 = 0x00500900;

  Label frame1_sp, frame2_sp;

  stack_section

    // frame 0

    .Append(32, 0)                      // space

    .D32(0x00490000)                    // junk that's not

    .D32(0x00600000)                    // a return address

    .Append(96, 0)                      // more space

    .D32(frame1_sp)                     // stack pointer

    .D32(return_address1)               // actual return address

    // frame 1

    .Mark(&frame1_sp)

    .Append(128 * 4, 0)                 // space

    .D32(0x00F00000)                    // more junk

    .D32(0x0000000D)

    .Append(128 * 4, 0)                 // more space

    .D32(frame2_sp)                     // stack pointer

    .D32(return_address2)               // actual return address

                                        // (won't be found)

    // frame 2

    .Mark(&frame2_sp)

    .Append(32, 0);                     // end of stack

  RegionFromSection();

  raw_context.epc = 0x00405510;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = stack_section.start().Value();

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = return_address1;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(2U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ("module2", modules_without_symbols[1]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(2U, frames->size());

  StackFrameMIPS* frame0 = static_cast<StackFrameMIPS*>(frames->at(0));

  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);

  ASSERT_EQ(StackFrameMIPS::CONTEXT_VALID_ALL, frame0->context_validity);

  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameMIPS* frame1 = static_cast<StackFrameMIPS*>(frames->at(1));

  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);

  ASSERT_EQ((StackFrameMIPS::CONTEXT_VALID_PC |

             StackFrameMIPS::CONTEXT_VALID_SP |

             StackFrameMIPS::CONTEXT_VALID_FP |

             StackFrameMIPS::CONTEXT_VALID_RA),

            frame1->context_validity);

  EXPECT_EQ(return_address1 - 2 * sizeof(return_address1), frame1->context.epc);

  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_MIPS_REG_SP]);

// Test that set_max_frames_scanned prevents using stack scanning

// to find caller frames.

TEST_F(GetCallerFrame, ScanningNotAllowed) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  // When the stack walker resorts to scanning the stack,

  // only fixed number of frames are allowed to be scanned out from stack

  stack_section.start() = 0x80000000;

  uint32_t return_address1 = 0x00500100;

  uint32_t return_address2 = 0x00500900;

  Label frame1_sp, frame2_sp;

  stack_section

    // frame 0

    .Append(32, 0)                      // space

    .D32(0x00490000)                    // junk that's not

    .D32(0x00600000)                    // a return address

    .Append(96, 0)                      // more space

    .D32(frame1_sp)                     // stack pointer

    .D32(return_address1)               // actual return address

    // frame 1

    .Mark(&frame1_sp)

    .Append(128 * 4, 0)                 // space

    .D32(0x00F00000)                    // more junk

    .D32(0x0000000D)

    .Append(128 * 4, 0)                 // more space

    .D32(frame2_sp)                     // stack pointer

    .D32(return_address2)               // actual return address

                                        // (won't be found)

    // frame 2

    .Mark(&frame2_sp)

    .Append(32, 0);                     // end of stack

  RegionFromSection();

  raw_context.epc = 0x00405510;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = stack_section.start().Value();

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = return_address1;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  Stackwalker::set_max_frames_scanned(0);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(1U, modules_without_symbols.size());

  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(1U, frames->size());

  StackFrameMIPS* frame0 = static_cast<StackFrameMIPS*>(frames->at(0));

  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);

  ASSERT_EQ(StackFrameMIPS::CONTEXT_VALID_ALL, frame0->context_validity);

  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

struct CFIFixture: public StackwalkerMIPSFixture {

  CFIFixture() {

    // Provide some STACK CFI records;

    SetModuleSymbols(&module1,

                     // The youngest frame's function.

                     "FUNC 4000 1000 0 enchiridion\n"

                     // Initially, nothing has been pushed on the stack,

                     // and the return address is still in the $ra register.

                     "STACK CFI INIT 4000 1000 .cfa: $sp 0 + .ra: $ra\n"

                     // Move stack pointer.

                     "STACK CFI 4004 .cfa: $sp 32 +\n"

                     // store $fp and ra

                     "STACK CFI 4008 $fp: .cfa -8 + ^ .ra: .cfa -4 + ^\n"

                     // restore $fp

                     "STACK CFI 400c .cfa: $fp 32 +\n"

                     // restore $sp

                     "STACK CFI 4018 .cfa: $sp 32 +\n"

                     "STACK CFI 4020 $fp: $fp .cfa: $sp 0 + .ra: .ra\n"

                     // The calling function.

                     "FUNC 5000 1000 0 epictetus\n"

                     // Mark it as end of stack.

                     "STACK CFI INIT 5000 8 .cfa: $sp 0 + .ra: $ra\n"

                     // A function whose CFI makes the stack pointer

                     // go backwards.

                     "FUNC 6000 1000 20 palinal\n"

                     "STACK CFI INIT 6000 1000 .cfa: $sp 4 - .ra: $ra\n"

                     // A function with CFI expressions that can't be

                     // evaluated.

                     "FUNC 7000 1000 20 rhetorical\n"

                     "STACK CFI INIT 7000 1000 .cfa: moot .ra: ambiguous\n"

);

    // Provide some distinctive values for the caller's registers.

    expected.epc = 0x00405508;

    expected.iregs[MD_CONTEXT_MIPS_REG_S0] = 0x0;

    expected.iregs[MD_CONTEXT_MIPS_REG_S1] = 0x1;

    expected.iregs[MD_CONTEXT_MIPS_REG_S2] = 0x2;

    expected.iregs[MD_CONTEXT_MIPS_REG_S3] = 0x3;

    expected.iregs[MD_CONTEXT_MIPS_REG_S4] = 0x4;

    expected.iregs[MD_CONTEXT_MIPS_REG_S5] = 0x5;

    expected.iregs[MD_CONTEXT_MIPS_REG_S6] = 0x6;

    expected.iregs[MD_CONTEXT_MIPS_REG_S7] = 0x7;

    expected.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

    expected.iregs[MD_CONTEXT_MIPS_REG_FP] = 0x80000000;

    expected.iregs[MD_CONTEXT_MIPS_REG_RA] = 0x00405510;

    // Expect CFI to recover all callee-save registers. Since CFI is the

    // only stack frame construction technique we have, aside from the

    // context frame itself, there's no way for us to have a set of valid

    // registers smaller than this.

    expected_validity = (StackFrameMIPS::CONTEXT_VALID_PC |

                         StackFrameMIPS::CONTEXT_VALID_S0 |

                         StackFrameMIPS::CONTEXT_VALID_S1 |

                         StackFrameMIPS::CONTEXT_VALID_S2 |

                         StackFrameMIPS::CONTEXT_VALID_S3 |

                         StackFrameMIPS::CONTEXT_VALID_S4 |

                         StackFrameMIPS::CONTEXT_VALID_S5 |

                         StackFrameMIPS::CONTEXT_VALID_S6 |

                         StackFrameMIPS::CONTEXT_VALID_S7 |

                         StackFrameMIPS::CONTEXT_VALID_SP |

                         StackFrameMIPS::CONTEXT_VALID_FP |

                         StackFrameMIPS::CONTEXT_VALID_RA);

    // By default, context frames provide all registers, as normal.

    context_frame_validity = StackFrameMIPS::CONTEXT_VALID_ALL;

    // By default, registers are unchanged.

    raw_context = expected;

  // Walk the stack, using stack_section as the contents of the stack

  // and raw_context as the current register values. (Set the stack

  // pointer to the stack's starting address.) Expect two stack

  // frames; in the older frame, expect the callee-saves registers to

  // have values matching those in 'expected'.

  void CheckWalk() {

    RegionFromSection();

    raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = stack_section.start().Value();

    StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

    StackwalkerMIPS walker(&system_info, &raw_context, &stack_region,

                           &modules, &frame_symbolizer);

    vector<const CodeModule*> modules_without_symbols;

    vector<const CodeModule*> modules_with_corrupt_symbols;

    ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                            &modules_with_corrupt_symbols));

    ASSERT_EQ(0U, modules_without_symbols.size());

    ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

    frames = call_stack.frames();

    ASSERT_EQ(2U, frames->size());

    StackFrameMIPS* frame0 = static_cast<StackFrameMIPS*>(frames->at(0));

    EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);

    ASSERT_EQ(StackFrameMIPS::CONTEXT_VALID_ALL, frame0->context_validity);

    EXPECT_EQ("enchiridion", frame0->function_name);

    EXPECT_EQ(0x00404000U, frame0->function_base);

    StackFrameMIPS* frame1 = static_cast<StackFrameMIPS*>(frames->at(1));

    EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame1->trust);

    ASSERT_EQ(expected_validity, frame1->context_validity);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S0],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S0]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S1],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S1]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S2],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S2]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S3],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S3]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S4],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S4]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S5],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S5]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S6],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S6]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_S7],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_S7]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_FP],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_FP]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_RA],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_RA]);

    EXPECT_EQ(expected.iregs[MD_CONTEXT_MIPS_REG_SP],

              frame1->context.iregs[MD_CONTEXT_MIPS_REG_SP]);

    EXPECT_EQ(expected.epc, frame1->context.epc);

    EXPECT_EQ(expected.epc, frame1->instruction);

    EXPECT_EQ("epictetus", frame1->function_name);

    EXPECT_EQ(0x00405000U, frame1->function_base);

  // The values we expect to find for the caller's registers.

  MDRawContextMIPS expected;

  // The validity mask for expected.

  int expected_validity;

  // The validity mask to impose on the context frame.

  int context_frame_validity;

};

class CFI: public CFIFixture, public Test { };

// TODO(gordanac): add CFI tests

TEST_F(CFI, At4004) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  Label frame1_sp = expected.iregs[MD_CONTEXT_MIPS_REG_SP];

  stack_section

    // frame0

    .Append(24, 0)               // space

    .D32(frame1_sp)              // stack pointer

    .D32(0x00405510)             // return address

    .Mark(&frame1_sp);           // This effectively sets stack_section.start().

  raw_context.epc = 0x00404004;

  CheckWalk();

// Check that we reject rules that would cause the stack pointer to

// move in the wrong direction.

TEST_F(CFI, RejectBackwards) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  raw_context.epc = 0x40005000;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = 0x00405510;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(0U, modules_without_symbols.size());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(1U, frames->size());

// Check that we reject rules whose expressions' evaluation fails.

TEST_F(CFI, RejectBadExpressions) {

  raw_context.context_flags = raw_context.context_flags | MD_CONTEXT_MIPS_FULL;

  raw_context.epc = 0x00407000;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_SP] = 0x80000000;

  raw_context.iregs[MD_CONTEXT_MIPS_REG_RA] = 0x00405510;

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);

  StackwalkerMIPS walker(&system_info, &raw_context, &stack_region, &modules,

                         &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;

  vector<const CodeModule*> modules_with_corrupt_symbols;

  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,

                          &modules_with_corrupt_symbols));

  ASSERT_EQ(0U, modules_without_symbols.size());

  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());

  frames = call_stack.frames();

  ASSERT_EQ(1U, frames->size());

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