third_party/v8/test/unittests/wasm/trap-handler-x64-unittest.cc - cobalt - Git at Google

 // Copyright 2018 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "include/v8config.h"

 #if V8_OS_LINUX || V8_OS_FREEBSD
 #include <signal.h>
 #include <ucontext.h>
 #elif V8_OS_MACOSX
 #include <signal.h>
 #include <sys/ucontext.h>
 #elif V8_OS_WIN
 #include <windows.h>
 #endif

 #include "testing/gtest/include/gtest/gtest.h"

 #if V8_OS_POSIX
 #include "include/v8-wasm-trap-handler-posix.h"
 #elif V8_OS_WIN
 #include "include/v8-wasm-trap-handler-win.h"
 #endif
 #include "src/base/page-allocator.h"
 #include "src/codegen/assembler-inl.h"
 #include "src/codegen/macro-assembler-inl.h"
 #include "src/execution/simulator.h"
 #include "src/objects/backing-store.h"
 #include "src/trap-handler/trap-handler.h"
 #include "src/utils/allocation.h"
 #include "src/utils/vector.h"
 #include "src/wasm/wasm-engine.h"

 #include "test/common/assembler-tester.h"
 #include "test/unittests/test-utils.h"

 namespace v8 {
 namespace internal {
 namespace wasm {

 namespace {
 constexpr Register scratch = r10;
 bool g_test_handler_executed = false;
 #if V8_OS_LINUX || V8_OS_MACOSX || V8_OS_FREEBSD
 struct sigaction g_old_segv_action;
 struct sigaction g_old_fpe_action;
 struct sigaction g_old_bus_action;  // We get SIGBUS on Mac sometimes.
 #elif V8_OS_WIN
 void* g_registered_handler = nullptr;
 #endif

 // The recovery address allows us to recover from an intentional crash.
 Address g_recovery_address;
 // Flag to indicate if the test handler should call the trap handler as a first
 // chance handler.
 bool g_use_as_first_chance_handler = false;
 }  // namespace

 #define __ masm.

 enum TrapHandlerStyle : int {
   // The test uses the default trap handler of V8.
   kDefault = 0,
   // The test installs the trap handler callback in its own test handler.
   kCallback = 1
 };

 std::string PrintTrapHandlerTestParam(
     ::testing::TestParamInfo<TrapHandlerStyle> info) {
   switch (info.param) {
     case kDefault:
       return "DefaultTrapHandler";
     case kCallback:
       return "Callback";
   }
   UNREACHABLE();
 }

 class TrapHandlerTest : public TestWithIsolate,
                         public ::testing::WithParamInterface<TrapHandlerStyle> {
  protected:
   void SetUp() override {
     InstallFallbackHandler();
     SetupTrapHandler(GetParam());
     backing_store_ = BackingStore::AllocateWasmMemory(i_isolate(), 1, 1,
                                                       SharedFlag::kNotShared);
     CHECK(backing_store_);
     CHECK(backing_store_->has_guard_regions());
     // The allocated backing store ends with a guard page.
     crash_address_ = reinterpret_cast<Address>(backing_store_->buffer_start()) +
                      backing_store_->byte_length() + 32;
     // Allocate a buffer for the generated code.
     buffer_ = AllocateAssemblerBuffer(AssemblerBase::kDefaultBufferSize,
                                       GetRandomMmapAddr());

     InitRecoveryCode();
   }

   void InstallFallbackHandler() {
 #if V8_OS_LINUX || V8_OS_MACOSX || V8_OS_FREEBSD
     // Set up a signal handler to recover from the expected crash.
     struct sigaction action;
     action.sa_sigaction = SignalHandler;
     sigemptyset(&action.sa_mask);
     action.sa_flags = SA_SIGINFO;
     // SIGSEGV happens for wasm oob memory accesses on Linux.
     CHECK_EQ(0, sigaction(SIGSEGV, &action, &g_old_segv_action));
     // SIGBUS happens for wasm oob memory accesses on macOS.
     CHECK_EQ(0, sigaction(SIGBUS, &action, &g_old_bus_action));
     // SIGFPE to simulate crashes which are not handled by the trap handler.
     CHECK_EQ(0, sigaction(SIGFPE, &action, &g_old_fpe_action));
 #elif V8_OS_WIN
     g_registered_handler =
         AddVectoredExceptionHandler(/*first=*/0, TestHandler);
 #endif
   }

   void TearDown() override {
     // We should always have left wasm code.
     CHECK(!GetThreadInWasmFlag());
     buffer_.reset();
     recovery_buffer_.reset();
     backing_store_.reset();

     // Clean up the trap handler
     trap_handler::RemoveTrapHandler();
     if (!g_test_handler_executed) {
 #if V8_OS_LINUX || V8_OS_MACOSX || V8_OS_FREEBSD
       // The test handler cleans up the signal handler setup in the test. If the
       // test handler was not called, we have to do the cleanup ourselves.
       CHECK_EQ(0, sigaction(SIGSEGV, &g_old_segv_action, nullptr));
       CHECK_EQ(0, sigaction(SIGFPE, &g_old_fpe_action, nullptr));
       CHECK_EQ(0, sigaction(SIGBUS, &g_old_bus_action, nullptr));
 #elif V8_OS_WIN
       RemoveVectoredExceptionHandler(g_registered_handler);
       g_registered_handler = nullptr;
 #endif
     }
   }

   void InitRecoveryCode() {
     // Create a code snippet where we can jump to to recover from a signal or
     // exception. The code snippet only consists of a return statement.
     recovery_buffer_ = AllocateAssemblerBuffer(
         AssemblerBase::kDefaultBufferSize, GetRandomMmapAddr());

     MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                         recovery_buffer_->CreateView());
     int recovery_offset = __ pc_offset();
     __ Pop(scratch);
     __ Ret();
     CodeDesc desc;
     masm.GetCode(nullptr, &desc);
     recovery_buffer_->MakeExecutable();
     g_recovery_address =
         reinterpret_cast<Address>(desc.buffer + recovery_offset);
   }

 #if V8_OS_LINUX || V8_OS_MACOSX || V8_OS_FREEBSD
   static void SignalHandler(int signal, siginfo_t* info, void* context) {
     if (g_use_as_first_chance_handler) {
       if (v8::TryHandleWebAssemblyTrapPosix(signal, info, context)) {
         return;
       }
     }

     // Reset the signal handler, to avoid that this signal handler is called
     // repeatedly.
     sigaction(SIGSEGV, &g_old_segv_action, nullptr);
     sigaction(SIGFPE, &g_old_fpe_action, nullptr);
     sigaction(SIGBUS, &g_old_bus_action, nullptr);

     g_test_handler_executed = true;
     // Set the $rip to the recovery code.
     ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
 #if V8_OS_LINUX
     uc->uc_mcontext.gregs[REG_RIP] = g_recovery_address;
 #elif V8_OS_MACOSX
     uc->uc_mcontext->__ss.__rip = g_recovery_address;
 #elif V8_OS_FREEBSD
     uc->uc_mcontext.mc_rip = g_recovery_address;
 #else
 #error Unsupported platform
 #endif
   }
 #endif

 #if V8_OS_WIN
   static LONG WINAPI TestHandler(EXCEPTION_POINTERS* exception) {
     if (g_use_as_first_chance_handler) {
       if (v8::TryHandleWebAssemblyTrapWindows(exception)) {
         return EXCEPTION_CONTINUE_EXECUTION;
       }
     }
     RemoveVectoredExceptionHandler(g_registered_handler);
     g_registered_handler = nullptr;
     g_test_handler_executed = true;
     exception->ContextRecord->Rip = g_recovery_address;
     return EXCEPTION_CONTINUE_EXECUTION;
   }
 #endif

   void SetupTrapHandler(TrapHandlerStyle style) {
     bool use_default_handler = style == kDefault;
     g_use_as_first_chance_handler = !use_default_handler;
     CHECK(v8::V8::EnableWebAssemblyTrapHandler(use_default_handler));
   }

  public:
   void GenerateSetThreadInWasmFlagCode(MacroAssembler* masm) {
     masm->Move(scratch,
                i_isolate()->thread_local_top()->thread_in_wasm_flag_address_,
                RelocInfo::NONE);
     masm->movl(MemOperand(scratch, 0), Immediate(1));
   }

   void GenerateResetThreadInWasmFlagCode(MacroAssembler* masm) {
     masm->Move(scratch,
                i_isolate()->thread_local_top()->thread_in_wasm_flag_address_,
                RelocInfo::NONE);
     masm->movl(MemOperand(scratch, 0), Immediate(0));
   }

   bool GetThreadInWasmFlag() {
     return *reinterpret_cast<int*>(
         trap_handler::GetThreadInWasmThreadLocalAddress());
   }

   // Execute the code in buffer.
   void ExecuteBuffer() {
     buffer_->MakeExecutable();
     GeneratedCode<void>::FromAddress(
         i_isolate(), reinterpret_cast<Address>(buffer_->start()))
         .Call();
     CHECK(!g_test_handler_executed);
   }

   // Execute the code in buffer. We expect a crash which we recover from in the
   // test handler.
   void ExecuteExpectCrash(TestingAssemblerBuffer* buffer,
                           bool check_wasm_flag = true) {
     CHECK(!g_test_handler_executed);
     buffer->MakeExecutable();
     GeneratedCode<void>::FromAddress(i_isolate(),
                                      reinterpret_cast<Address>(buffer->start()))
         .Call();
     CHECK(g_test_handler_executed);
     g_test_handler_executed = false;
     if (check_wasm_flag) CHECK(!GetThreadInWasmFlag());
   }

   bool test_handler_executed() { return g_test_handler_executed; }

   // The backing store used for testing the trap handler.
   std::unique_ptr<BackingStore> backing_store_;

   // Address within the guard region of the wasm memory. Accessing this memory
   // address causes a signal or exception.
   Address crash_address_;

   // Buffer for generated code.
   std::unique_ptr<TestingAssemblerBuffer> buffer_;
   // Buffer for the code for the landing pad of the test handler.
   std::unique_ptr<TestingAssemblerBuffer> recovery_buffer_;
 };

 // TODO(almuthanna): These tests were skipped because they cause a crash when
 // they are ran on Fuchsia. This issue should be solved later on
 // Ticket: https://crbug.com/1028617
 #if !defined(V8_TARGET_OS_FUCHSIA)
 TEST_P(TrapHandlerTest, TestTrapHandlerRecovery) {
   // Test that the wasm trap handler can recover a memory access violation in
   // wasm code (we fake the wasm code and the access violation).
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   GenerateSetThreadInWasmFlagCode(&masm);
   __ Move(scratch, crash_address_, RelocInfo::NONE);
   int crash_offset = __ pc_offset();
   __ testl(MemOperand(scratch, 0), Immediate(1));
   int recovery_offset = __ pc_offset();
   GenerateResetThreadInWasmFlagCode(&masm);
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
                                                                recovery_offset};
   trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
                                     desc.instr_size, 1, &protected_instruction);

   ExecuteBuffer();
 }

 TEST_P(TrapHandlerTest, TestReleaseHandlerData) {
   // Test that after we release handler data in the trap handler, it cannot
   // recover from the specific memory access violation anymore.
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   GenerateSetThreadInWasmFlagCode(&masm);
   __ Move(scratch, crash_address_, RelocInfo::NONE);
   int crash_offset = __ pc_offset();
   __ testl(MemOperand(scratch, 0), Immediate(1));
   int recovery_offset = __ pc_offset();
   GenerateResetThreadInWasmFlagCode(&masm);
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
                                                                recovery_offset};
   int handler_id = trap_handler::RegisterHandlerData(
       reinterpret_cast<Address>(desc.buffer), desc.instr_size, 1,
       &protected_instruction);

   ExecuteBuffer();

   // Deregister from the trap handler. The trap handler should not do the
   // recovery now.
   trap_handler::ReleaseHandlerData(handler_id);

   ExecuteExpectCrash(buffer_.get());
 }

 TEST_P(TrapHandlerTest, TestNoThreadInWasmFlag) {
   // That that if the thread_in_wasm flag is not set, the trap handler does not
   // get active.
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   __ Move(scratch, crash_address_, RelocInfo::NONE);
   int crash_offset = __ pc_offset();
   __ testl(MemOperand(scratch, 0), Immediate(1));
   int recovery_offset = __ pc_offset();
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
                                                                recovery_offset};
   trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
                                     desc.instr_size, 1, &protected_instruction);

   ExecuteExpectCrash(buffer_.get());
 }

 TEST_P(TrapHandlerTest, TestCrashInWasmNoProtectedInstruction) {
   // Test that if the crash in wasm happened at an instruction which is not
   // protected, then the trap handler does not handle it.
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   GenerateSetThreadInWasmFlagCode(&masm);
   int no_crash_offset = __ pc_offset();
   __ Move(scratch, crash_address_, RelocInfo::NONE);
   __ testl(MemOperand(scratch, 0), Immediate(1));
   // Offset where the crash is not happening.
   int recovery_offset = __ pc_offset();
   GenerateResetThreadInWasmFlagCode(&masm);
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{no_crash_offset,
                                                                recovery_offset};
   trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
                                     desc.instr_size, 1, &protected_instruction);

   ExecuteExpectCrash(buffer_.get());
 }

 TEST_P(TrapHandlerTest, TestCrashInWasmWrongCrashType) {
   // Test that if the crash reason is not a memory access violation, then the
   // wasm trap handler does not handle it.
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   GenerateSetThreadInWasmFlagCode(&masm);
   __ xorq(scratch, scratch);
   int crash_offset = __ pc_offset();
   __ divq(scratch);
   // Offset where the crash is not happening.
   int recovery_offset = __ pc_offset();
   GenerateResetThreadInWasmFlagCode(&masm);
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
                                                                recovery_offset};
   trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
                                     desc.instr_size, 1, &protected_instruction);

 #if V8_OS_POSIX
   // On Posix, the V8 default trap handler does not register for SIGFPE,
   // therefore the thread-in-wasm flag is never reset in this test. We
   // therefore do not check the value of this flag.
   bool check_wasm_flag = GetParam() != kDefault;
 #elif V8_OS_WIN
   // On Windows, the trap handler returns immediately if not an exception of
   // interest.
   bool check_wasm_flag = false;
 #else
   bool check_wasm_flag = true;
 #endif
   ExecuteExpectCrash(buffer_.get(), check_wasm_flag);
   if (!check_wasm_flag) {
     // Reset the thread-in-wasm flag because it was probably not reset in the
     // trap handler.
     *trap_handler::GetThreadInWasmThreadLocalAddress() = 0;
   }
 }
 #endif

 class CodeRunner : public v8::base::Thread {
  public:
   CodeRunner(TrapHandlerTest* test, TestingAssemblerBuffer* buffer)
       : Thread(Options("CodeRunner")), test_(test), buffer_(buffer) {}

   void Run() override { test_->ExecuteExpectCrash(buffer_); }

  private:
   TrapHandlerTest* test_;
   TestingAssemblerBuffer* buffer_;
 };

 // TODO(almuthanna): This test was skipped because it causes a crash when it is
 // ran on Fuchsia. This issue should be solved later on
 // Ticket: https://crbug.com/1028617
 #if !defined(V8_TARGET_OS_FUCHSIA)
 TEST_P(TrapHandlerTest, TestCrashInOtherThread) {
   // Test setup:
   // The current thread enters wasm land (sets the thread_in_wasm flag)
   // A second thread crashes at a protected instruction without having the flag
   // set.
   MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
                       buffer_->CreateView());
   __ Push(scratch);
   __ Move(scratch, crash_address_, RelocInfo::NONE);
   int crash_offset = __ pc_offset();
   __ testl(MemOperand(scratch, 0), Immediate(1));
   int recovery_offset = __ pc_offset();
   __ Pop(scratch);
   __ Ret();
   CodeDesc desc;
   masm.GetCode(nullptr, &desc);

   trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
                                                                recovery_offset};
   trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
                                     desc.instr_size, 1, &protected_instruction);

   CodeRunner runner(this, buffer_.get());
   CHECK(!GetThreadInWasmFlag());
   // Set the thread-in-wasm flag manually in this thread.
   *trap_handler::GetThreadInWasmThreadLocalAddress() = 1;
   CHECK(runner.Start());
   runner.Join();
   CHECK(GetThreadInWasmFlag());
   // Reset the thread-in-wasm flag.
   *trap_handler::GetThreadInWasmThreadLocalAddress() = 0;
 }
 #endif

 INSTANTIATE_TEST_SUITE_P(Traps, TrapHandlerTest,
                          ::testing::Values(kDefault, kCallback),
                          PrintTrapHandlerTestParam);

 #undef __
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
	// Copyright 2018 the V8 project authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "include/v8config.h"

	#if V8_OS_LINUX \|\| V8_OS_FREEBSD
	#include <signal.h>
	#include <ucontext.h>
	#elif V8_OS_MACOSX
	#include <signal.h>
	#include <sys/ucontext.h>
	#elif V8_OS_WIN
	#include <windows.h>
	#endif

	#include "testing/gtest/include/gtest/gtest.h"

	#if V8_OS_POSIX
	#include "include/v8-wasm-trap-handler-posix.h"
	#elif V8_OS_WIN
	#include "include/v8-wasm-trap-handler-win.h"
	#endif
	#include "src/base/page-allocator.h"
	#include "src/codegen/assembler-inl.h"
	#include "src/codegen/macro-assembler-inl.h"
	#include "src/execution/simulator.h"
	#include "src/objects/backing-store.h"
	#include "src/trap-handler/trap-handler.h"
	#include "src/utils/allocation.h"
	#include "src/utils/vector.h"
	#include "src/wasm/wasm-engine.h"

	#include "test/common/assembler-tester.h"
	#include "test/unittests/test-utils.h"

	namespace v8 {
	namespace internal {
	namespace wasm {

	namespace {
	constexpr Register scratch = r10;
	bool g_test_handler_executed = false;
	#if V8_OS_LINUX \|\| V8_OS_MACOSX \|\| V8_OS_FREEBSD
	struct sigaction g_old_segv_action;
	struct sigaction g_old_fpe_action;
	struct sigaction g_old_bus_action; // We get SIGBUS on Mac sometimes.
	#elif V8_OS_WIN
	void* g_registered_handler = nullptr;
	#endif

	// The recovery address allows us to recover from an intentional crash.
	Address g_recovery_address;
	// Flag to indicate if the test handler should call the trap handler as a first
	// chance handler.
	bool g_use_as_first_chance_handler = false;
	} // namespace

	#define __ masm.

	enum TrapHandlerStyle : int {
	// The test uses the default trap handler of V8.
	kDefault = 0,
	// The test installs the trap handler callback in its own test handler.
	kCallback = 1
	};

	std::string PrintTrapHandlerTestParam(
	::testing::TestParamInfo<TrapHandlerStyle> info) {
	switch (info.param) {
	case kDefault:
	return "DefaultTrapHandler";
	case kCallback:
	return "Callback";
	}
	UNREACHABLE();
	}

	class TrapHandlerTest : public TestWithIsolate,
	public ::testing::WithParamInterface<TrapHandlerStyle> {
	protected:
	void SetUp() override {
	InstallFallbackHandler();
	SetupTrapHandler(GetParam());
	backing_store_ = BackingStore::AllocateWasmMemory(i_isolate(), 1, 1,
	SharedFlag::kNotShared);
	CHECK(backing_store_);
	CHECK(backing_store_->has_guard_regions());
	// The allocated backing store ends with a guard page.
	crash_address_ = reinterpret_cast<Address>(backing_store_->buffer_start()) +
	backing_store_->byte_length() + 32;
	// Allocate a buffer for the generated code.
	buffer_ = AllocateAssemblerBuffer(AssemblerBase::kDefaultBufferSize,
	GetRandomMmapAddr());

	InitRecoveryCode();
	}

	void InstallFallbackHandler() {
	#if V8_OS_LINUX \|\| V8_OS_MACOSX \|\| V8_OS_FREEBSD
	// Set up a signal handler to recover from the expected crash.
	struct sigaction action;
	action.sa_sigaction = SignalHandler;
	sigemptyset(&action.sa_mask);
	action.sa_flags = SA_SIGINFO;
	// SIGSEGV happens for wasm oob memory accesses on Linux.
	CHECK_EQ(0, sigaction(SIGSEGV, &action, &g_old_segv_action));
	// SIGBUS happens for wasm oob memory accesses on macOS.
	CHECK_EQ(0, sigaction(SIGBUS, &action, &g_old_bus_action));
	// SIGFPE to simulate crashes which are not handled by the trap handler.
	CHECK_EQ(0, sigaction(SIGFPE, &action, &g_old_fpe_action));
	#elif V8_OS_WIN
	g_registered_handler =
	AddVectoredExceptionHandler(/first=/0, TestHandler);
	#endif
	}

	void TearDown() override {
	// We should always have left wasm code.
	CHECK(!GetThreadInWasmFlag());
	buffer_.reset();
	recovery_buffer_.reset();
	backing_store_.reset();

	// Clean up the trap handler
	trap_handler::RemoveTrapHandler();
	if (!g_test_handler_executed) {
	#if V8_OS_LINUX \|\| V8_OS_MACOSX \|\| V8_OS_FREEBSD
	// The test handler cleans up the signal handler setup in the test. If the
	// test handler was not called, we have to do the cleanup ourselves.
	CHECK_EQ(0, sigaction(SIGSEGV, &g_old_segv_action, nullptr));
	CHECK_EQ(0, sigaction(SIGFPE, &g_old_fpe_action, nullptr));
	CHECK_EQ(0, sigaction(SIGBUS, &g_old_bus_action, nullptr));
	#elif V8_OS_WIN
	RemoveVectoredExceptionHandler(g_registered_handler);
	g_registered_handler = nullptr;
	#endif
	}
	}

	void InitRecoveryCode() {
	// Create a code snippet where we can jump to to recover from a signal or
	// exception. The code snippet only consists of a return statement.
	recovery_buffer_ = AllocateAssemblerBuffer(
	AssemblerBase::kDefaultBufferSize, GetRandomMmapAddr());

	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	recovery_buffer_->CreateView());
	int recovery_offset = __ pc_offset();
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);
	recovery_buffer_->MakeExecutable();
	g_recovery_address =
	reinterpret_cast<Address>(desc.buffer + recovery_offset);
	}

	#if V8_OS_LINUX \|\| V8_OS_MACOSX \|\| V8_OS_FREEBSD
	static void SignalHandler(int signal, siginfo_t* info, void* context) {
	if (g_use_as_first_chance_handler) {
	if (v8::TryHandleWebAssemblyTrapPosix(signal, info, context)) {
	return;
	}
	}

	// Reset the signal handler, to avoid that this signal handler is called
	// repeatedly.
	sigaction(SIGSEGV, &g_old_segv_action, nullptr);
	sigaction(SIGFPE, &g_old_fpe_action, nullptr);
	sigaction(SIGBUS, &g_old_bus_action, nullptr);

	g_test_handler_executed = true;
	// Set the $rip to the recovery code.
	ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
	#if V8_OS_LINUX
	uc->uc_mcontext.gregs[REG_RIP] = g_recovery_address;
	#elif V8_OS_MACOSX
	uc->uc_mcontext->__ss.__rip = g_recovery_address;
	#elif V8_OS_FREEBSD
	uc->uc_mcontext.mc_rip = g_recovery_address;
	#else
	#error Unsupported platform
	#endif
	}
	#endif

	#if V8_OS_WIN
	static LONG WINAPI TestHandler(EXCEPTION_POINTERS* exception) {
	if (g_use_as_first_chance_handler) {
	if (v8::TryHandleWebAssemblyTrapWindows(exception)) {
	return EXCEPTION_CONTINUE_EXECUTION;
	}
	}
	RemoveVectoredExceptionHandler(g_registered_handler);
	g_registered_handler = nullptr;
	g_test_handler_executed = true;
	exception->ContextRecord->Rip = g_recovery_address;
	return EXCEPTION_CONTINUE_EXECUTION;
	}
	#endif

	void SetupTrapHandler(TrapHandlerStyle style) {
	bool use_default_handler = style == kDefault;
	g_use_as_first_chance_handler = !use_default_handler;
	CHECK(v8::V8::EnableWebAssemblyTrapHandler(use_default_handler));
	}

	public:
	void GenerateSetThreadInWasmFlagCode(MacroAssembler* masm) {
	masm->Move(scratch,
	i_isolate()->thread_local_top()->thread_in_wasm_flag_address_,
	RelocInfo::NONE);
	masm->movl(MemOperand(scratch, 0), Immediate(1));
	}

	void GenerateResetThreadInWasmFlagCode(MacroAssembler* masm) {
	masm->Move(scratch,
	i_isolate()->thread_local_top()->thread_in_wasm_flag_address_,
	RelocInfo::NONE);
	masm->movl(MemOperand(scratch, 0), Immediate(0));
	}

	bool GetThreadInWasmFlag() {
	return reinterpret_cast<int>(
	trap_handler::GetThreadInWasmThreadLocalAddress());
	}

	// Execute the code in buffer.
	void ExecuteBuffer() {
	buffer_->MakeExecutable();
	GeneratedCode<void>::FromAddress(
	i_isolate(), reinterpret_cast<Address>(buffer_->start()))
	.Call();
	CHECK(!g_test_handler_executed);
	}

	// Execute the code in buffer. We expect a crash which we recover from in the
	// test handler.
	void ExecuteExpectCrash(TestingAssemblerBuffer* buffer,
	bool check_wasm_flag = true) {
	CHECK(!g_test_handler_executed);
	buffer->MakeExecutable();
	GeneratedCode<void>::FromAddress(i_isolate(),
	reinterpret_cast<Address>(buffer->start()))
	.Call();
	CHECK(g_test_handler_executed);
	g_test_handler_executed = false;
	if (check_wasm_flag) CHECK(!GetThreadInWasmFlag());
	}

	bool test_handler_executed() { return g_test_handler_executed; }

	// The backing store used for testing the trap handler.
	std::unique_ptr<BackingStore> backing_store_;

	// Address within the guard region of the wasm memory. Accessing this memory
	// address causes a signal or exception.
	Address crash_address_;

	// Buffer for generated code.
	std::unique_ptr<TestingAssemblerBuffer> buffer_;
	// Buffer for the code for the landing pad of the test handler.
	std::unique_ptr<TestingAssemblerBuffer> recovery_buffer_;
	};

	// TODO(almuthanna): These tests were skipped because they cause a crash when
	// they are ran on Fuchsia. This issue should be solved later on
	// Ticket: https://crbug.com/1028617
	#if !defined(V8_TARGET_OS_FUCHSIA)
	TEST_P(TrapHandlerTest, TestTrapHandlerRecovery) {
	// Test that the wasm trap handler can recover a memory access violation in
	// wasm code (we fake the wasm code and the access violation).
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	GenerateSetThreadInWasmFlagCode(&masm);
	__ Move(scratch, crash_address_, RelocInfo::NONE);
	int crash_offset = __ pc_offset();
	__ testl(MemOperand(scratch, 0), Immediate(1));
	int recovery_offset = __ pc_offset();
	GenerateResetThreadInWasmFlagCode(&masm);
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
	recovery_offset};
	trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
	desc.instr_size, 1, &protected_instruction);

	ExecuteBuffer();
	}

	TEST_P(TrapHandlerTest, TestReleaseHandlerData) {
	// Test that after we release handler data in the trap handler, it cannot
	// recover from the specific memory access violation anymore.
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	GenerateSetThreadInWasmFlagCode(&masm);
	__ Move(scratch, crash_address_, RelocInfo::NONE);
	int crash_offset = __ pc_offset();
	__ testl(MemOperand(scratch, 0), Immediate(1));
	int recovery_offset = __ pc_offset();
	GenerateResetThreadInWasmFlagCode(&masm);
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
	recovery_offset};
	int handler_id = trap_handler::RegisterHandlerData(
	reinterpret_cast<Address>(desc.buffer), desc.instr_size, 1,
	&protected_instruction);

	ExecuteBuffer();

	// Deregister from the trap handler. The trap handler should not do the
	// recovery now.
	trap_handler::ReleaseHandlerData(handler_id);

	ExecuteExpectCrash(buffer_.get());
	}

	TEST_P(TrapHandlerTest, TestNoThreadInWasmFlag) {
	// That that if the thread_in_wasm flag is not set, the trap handler does not
	// get active.
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	__ Move(scratch, crash_address_, RelocInfo::NONE);
	int crash_offset = __ pc_offset();
	__ testl(MemOperand(scratch, 0), Immediate(1));
	int recovery_offset = __ pc_offset();
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
	recovery_offset};
	trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
	desc.instr_size, 1, &protected_instruction);

	ExecuteExpectCrash(buffer_.get());
	}

	TEST_P(TrapHandlerTest, TestCrashInWasmNoProtectedInstruction) {
	// Test that if the crash in wasm happened at an instruction which is not
	// protected, then the trap handler does not handle it.
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	GenerateSetThreadInWasmFlagCode(&masm);
	int no_crash_offset = __ pc_offset();
	__ Move(scratch, crash_address_, RelocInfo::NONE);
	__ testl(MemOperand(scratch, 0), Immediate(1));
	// Offset where the crash is not happening.
	int recovery_offset = __ pc_offset();
	GenerateResetThreadInWasmFlagCode(&masm);
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{no_crash_offset,
	recovery_offset};
	trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
	desc.instr_size, 1, &protected_instruction);

	ExecuteExpectCrash(buffer_.get());
	}

	TEST_P(TrapHandlerTest, TestCrashInWasmWrongCrashType) {
	// Test that if the crash reason is not a memory access violation, then the
	// wasm trap handler does not handle it.
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	GenerateSetThreadInWasmFlagCode(&masm);
	__ xorq(scratch, scratch);
	int crash_offset = __ pc_offset();
	__ divq(scratch);
	// Offset where the crash is not happening.
	int recovery_offset = __ pc_offset();
	GenerateResetThreadInWasmFlagCode(&masm);
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
	recovery_offset};
	trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
	desc.instr_size, 1, &protected_instruction);

	#if V8_OS_POSIX
	// On Posix, the V8 default trap handler does not register for SIGFPE,
	// therefore the thread-in-wasm flag is never reset in this test. We
	// therefore do not check the value of this flag.
	bool check_wasm_flag = GetParam() != kDefault;
	#elif V8_OS_WIN
	// On Windows, the trap handler returns immediately if not an exception of
	// interest.
	bool check_wasm_flag = false;
	#else
	bool check_wasm_flag = true;
	#endif
	ExecuteExpectCrash(buffer_.get(), check_wasm_flag);
	if (!check_wasm_flag) {
	// Reset the thread-in-wasm flag because it was probably not reset in the
	// trap handler.
	*trap_handler::GetThreadInWasmThreadLocalAddress() = 0;
	}
	}
	#endif

	class CodeRunner : public v8::base::Thread {
	public:
	CodeRunner(TrapHandlerTest* test, TestingAssemblerBuffer* buffer)
	: Thread(Options("CodeRunner")), test_(test), buffer_(buffer) {}

	void Run() override { test_->ExecuteExpectCrash(buffer_); }

	private:
	TrapHandlerTest* test_;
	TestingAssemblerBuffer* buffer_;
	};

	// TODO(almuthanna): This test was skipped because it causes a crash when it is
	// ran on Fuchsia. This issue should be solved later on
	// Ticket: https://crbug.com/1028617
	#if !defined(V8_TARGET_OS_FUCHSIA)
	TEST_P(TrapHandlerTest, TestCrashInOtherThread) {
	// Test setup:
	// The current thread enters wasm land (sets the thread_in_wasm flag)
	// A second thread crashes at a protected instruction without having the flag
	// set.
	MacroAssembler masm(nullptr, AssemblerOptions{}, CodeObjectRequired::kNo,
	buffer_->CreateView());
	__ Push(scratch);
	__ Move(scratch, crash_address_, RelocInfo::NONE);
	int crash_offset = __ pc_offset();
	__ testl(MemOperand(scratch, 0), Immediate(1));
	int recovery_offset = __ pc_offset();
	__ Pop(scratch);
	__ Ret();
	CodeDesc desc;
	masm.GetCode(nullptr, &desc);

	trap_handler::ProtectedInstructionData protected_instruction{crash_offset,
	recovery_offset};
	trap_handler::RegisterHandlerData(reinterpret_cast<Address>(desc.buffer),
	desc.instr_size, 1, &protected_instruction);

	CodeRunner runner(this, buffer_.get());
	CHECK(!GetThreadInWasmFlag());
	// Set the thread-in-wasm flag manually in this thread.
	*trap_handler::GetThreadInWasmThreadLocalAddress() = 1;
	CHECK(runner.Start());
	runner.Join();
	CHECK(GetThreadInWasmFlag());
	// Reset the thread-in-wasm flag.
	*trap_handler::GetThreadInWasmThreadLocalAddress() = 0;
	}
	#endif

	INSTANTIATE_TEST_SUITE_P(Traps, TrapHandlerTest,
	::testing::Values(kDefault, kCallback),
	PrintTrapHandlerTestParam);

	#undef __
	} // namespace wasm
	} // namespace internal
	} // namespace v8