runtime/jit/jit_memory_region_test.cc - platform/art - Git at Google

 /*
  * Copyright (C) 2019 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "jit/jit_memory_region.h"

 #include <signal.h>
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <unistd.h>

 #include <android-base/unique_fd.h>
 #include <gtest/gtest.h>

 #include "base/globals.h"
 #include "base/memfd.h"

 namespace art {
 namespace jit {

 // These tests only run on bionic.
 #if defined(__BIONIC__)
 static constexpr int kReturnFromFault = 42;

 // These globals are only set in child processes.
 void* gAddrToFaultOn = nullptr;

 void handler(int ATTRIBUTE_UNUSED, siginfo_t* info, void* ATTRIBUTE_UNUSED) {
   CHECK_EQ(info->si_addr, gAddrToFaultOn);
   exit(kReturnFromFault);
 }

 static void registerSignalHandler() {
   struct sigaction sa;
   sigemptyset(&sa.sa_mask);
   sa.sa_flags = SA_SIGINFO;
   sa.sa_sigaction = handler;
   sigaction(SIGSEGV, &sa, nullptr);
 }

 class TestZygoteMemory : public testing::Test {
  public:
   void BasicTest() {
     std::string error_msg;
     size_t size = kPageSize;
     android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
     CHECK_NE(fd.get(), -1);

     // Create a writable mapping.
     int32_t* addr = reinterpret_cast<int32_t*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0));
     CHECK(addr != nullptr);
     CHECK_NE(addr, MAP_FAILED);

     // Test that we can write into the mapping.
     addr[0] = 42;
     CHECK_EQ(addr[0], 42);

     // Protect the memory.
     bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
     CHECK(res);

     // Test that we can still write into the mapping.
     addr[0] = 2;
     CHECK_EQ(addr[0], 2);

     // Test that we cannot create another writable mapping.
     int32_t* addr2 = reinterpret_cast<int32_t*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0));
     CHECK_EQ(addr2, MAP_FAILED);

     // With the existing mapping, we can toggle read/write.
     CHECK_EQ(mprotect(addr, size, PROT_READ), 0) << strerror(errno);
     CHECK_EQ(mprotect(addr, size, PROT_READ | PROT_WRITE), 0) << strerror(errno);

     // Test mremap with old_size = 0. From the man pages:
     //    If the value of old_size is zero, and old_address refers to a shareable mapping
     //    (see mmap(2) MAP_SHARED), then mremap() will create a new mapping of the same pages.
     addr2 = reinterpret_cast<int32_t*>(mremap(addr, 0, kPageSize, MREMAP_MAYMOVE));
     CHECK_NE(addr2, MAP_FAILED);

     // Test that we can  write into the remapped mapping.
     addr2[0] = 3;
     CHECK_EQ(addr2[0], 3);

     addr2 = reinterpret_cast<int32_t*>(mremap(addr, kPageSize, 2 * kPageSize, MREMAP_MAYMOVE));
     CHECK_NE(addr2, MAP_FAILED);

     // Test that we can  write into the remapped mapping.
     addr2[0] = 4;
     CHECK_EQ(addr2[0], 4);
   }

   void TestUnmapWritableAfterFork() {
     std::string error_msg;
     size_t size = kPageSize;
     int32_t* addr = nullptr;
     int32_t* addr2 = nullptr;
     {
       android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
       CHECK_NE(fd.get(), -1);

       // Create a writable mapping.
       addr = reinterpret_cast<int32_t*>(
           mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0));
       CHECK(addr != nullptr);
       CHECK_NE(addr, MAP_FAILED);

       // Test that we can write into the mapping.
       addr[0] = 42;
       CHECK_EQ(addr[0], 42);

       // Create a read-only mapping.
       addr2 = reinterpret_cast<int32_t*>(
           mmap(nullptr, kPageSize, PROT_READ, MAP_SHARED, fd.get(), 0));
       CHECK(addr2 != nullptr);

       // Protect the memory.
       bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
       CHECK(res);
     }
     // At this point, the fd has been dropped, but the memory mappings are still
     // there.

     // Create a mapping of atomic ints to communicate between processes.
     android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
     CHECK_NE(fd2.get(), -1);
     std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd2.get(), 0));

     // Values used for the tests below.
     const int32_t parent_value = 66;
     const int32_t child_value = 33;
     const int32_t starting_value = 22;

     shared[0] = 0;
     addr[0] = starting_value;
     CHECK_EQ(addr[0], starting_value);
     CHECK_EQ(addr2[0], starting_value);
     pid_t pid = fork();
     if (pid == 0) {
       // Test that we can write into the mapping.
       addr[0] = child_value;
       CHECK_EQ(addr[0], child_value);
       CHECK_EQ(addr2[0], child_value);

       // Unmap the writable mappping.
       munmap(addr, kPageSize);

       CHECK_EQ(addr2[0], child_value);

       // Notify parent process.
       shared[0] = 1;

       // Wait for parent process for a new value.
       while (shared[0] != 2) {
         sched_yield();
       }
       CHECK_EQ(addr2[0], parent_value);

       // Test that we cannot write into the mapping. The signal handler will
       // exit the process.
       gAddrToFaultOn = addr;
       registerSignalHandler();
       // This write will trigger a fault, as `addr` is unmapped.
       addr[0] = child_value + 1;
       exit(0);
     } else {
       while (shared[0] != 1) {
         sched_yield();
       }
       CHECK_EQ(addr[0], child_value);
       CHECK_EQ(addr2[0], child_value);
       addr[0] = parent_value;
       // Notify the child if the new value.
       shared[0] = 2;
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(WEXITSTATUS(status), kReturnFromFault);
       CHECK_EQ(addr[0], parent_value);
       CHECK_EQ(addr2[0], parent_value);
       munmap(addr, kPageSize);
       munmap(addr2, kPageSize);
       munmap(shared, kPageSize);
     }
   }

   void TestMadviseDontFork() {
     std::string error_msg;
     size_t size = kPageSize;
     int32_t* addr = nullptr;
     int32_t* addr2 = nullptr;
     {
       android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
       CHECK_NE(fd.get(), -1);

       // Create a writable mapping.
       addr = reinterpret_cast<int32_t*>(
           mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0));
       CHECK(addr != nullptr);
       CHECK_NE(addr, MAP_FAILED);
       CHECK_EQ(madvise(addr, kPageSize, MADV_DONTFORK), 0);

       // Test that we can write into the mapping.
       addr[0] = 42;
       CHECK_EQ(addr[0], 42);

       // Create a read-only mapping.
       addr2 = reinterpret_cast<int32_t*>(
           mmap(nullptr, kPageSize, PROT_READ, MAP_SHARED, fd.get(), 0));
       CHECK(addr2 != nullptr);

       // Protect the memory.
       bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
       CHECK(res);
     }
     // At this point, the fd has been dropped, but the memory mappings are still
     // there.

     // Create a mapping of atomic ints to communicate between processes.
     android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
     CHECK_NE(fd2.get(), -1);
     std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd2.get(), 0));

     // Values used for the tests below.
     const int32_t parent_value = 66;
     const int32_t child_value = 33;
     const int32_t starting_value = 22;

     shared[0] = 0;
     addr[0] = starting_value;
     CHECK_EQ(addr[0], starting_value);
     CHECK_EQ(addr2[0], starting_value);
     pid_t pid = fork();
     if (pid == 0) {
       CHECK_EQ(addr2[0], starting_value);

       // Notify parent process.
       shared[0] = 1;

       // Wait for parent process for new value.
       while (shared[0] != 2) {
         sched_yield();
       }

       CHECK_EQ(addr2[0], parent_value);
       // Test that we cannot write into the mapping. The signal handler will
       // exit the process.
       gAddrToFaultOn = addr;
       registerSignalHandler();
       addr[0] = child_value + 1;
       exit(0);
     } else {
       while (shared[0] != 1) {
         sched_yield();
       }
       CHECK_EQ(addr[0], starting_value);
       CHECK_EQ(addr2[0], starting_value);
       addr[0] = parent_value;
       // Notify the child of the new value.
       shared[0] = 2;
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(WEXITSTATUS(status), kReturnFromFault);
       CHECK_EQ(addr[0], parent_value);
       CHECK_EQ(addr2[0], parent_value);

       munmap(addr, kPageSize);
       munmap(addr2, kPageSize);
       munmap(shared, kPageSize);
     }
   }

   // This code is testing some behavior that ART could potentially use: get a
   // copy-on-write mapping that can incorporate changes from a shared mapping
   // owned by another process.
   void TestFromSharedToPrivate() {
     // This test is only for memfd with future write sealing support:
     // 1) ashmem with PROT_READ doesn't permit mapping MAP_PRIVATE | PROT_WRITE
     // 2) ashmem mapped MAP_PRIVATE discards the contents already written.
     if (!art::IsSealFutureWriteSupported()) {
       return;
     }
     std::string error_msg;
     size_t size = kPageSize;
     int32_t* addr = nullptr;
     android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
     CHECK_NE(fd.get(), -1);

     // Create a writable mapping.
     addr = reinterpret_cast<int32_t*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0));
     CHECK(addr != nullptr);
     CHECK_NE(addr, MAP_FAILED);

     // Test that we can write into the mapping.
     addr[0] = 42;
     CHECK_EQ(addr[0], 42);

     // Create another mapping of atomic ints to communicate between processes.
     android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
     CHECK_NE(fd2.get(), -1);
     std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
         mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd2.get(), 0));

     // Protect the memory.
     CHECK(JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg));

     // Values used for the tests below.
     const int32_t parent_value = 66;
     const int32_t child_value = 33;
     const int32_t starting_value = 22;

     // Check that updates done by a child mapping write-private are not visible
     // to the parent.
     addr[0] = starting_value;
     shared[0] = 0;
     pid_t pid = fork();
     if (pid == 0) {
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       addr[0] = child_value;
       exit(0);
     } else {
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(addr[0], starting_value);
     }

     addr[0] = starting_value;
     shared[0] = 0;

     // Check getting back and forth on shared mapping.
     pid = fork();
     if (pid == 0) {
       // Map it private with write access. MAP_FIXED will replace the existing
       // mapping.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       addr[0] = child_value;
       CHECK_EQ(addr[0], child_value);

       // Check that mapping shared with write access fails.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd.get(), 0),
                MAP_FAILED);
       CHECK_EQ(errno, EPERM);

       // Map shared with read access.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ, MAP_SHARED | MAP_FIXED, fd.get(), 0), addr);
       CHECK_NE(addr[0], child_value);

       // Wait for the parent to notify.
       while (shared[0] != 1) {
         sched_yield();
       }
       CHECK_EQ(addr[0], parent_value);

       // Notify the parent for getting a new update of the buffer.
       shared[0] = 2;

       // Map it private again.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       addr[0] = child_value + 1;
       CHECK_EQ(addr[0], child_value + 1);

       // And map it back shared.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ, MAP_SHARED | MAP_FIXED, fd.get(), 0), addr);
       while (shared[0] != 3) {
         sched_yield();
       }
       CHECK_EQ(addr[0], parent_value + 1);
       exit(0);
     } else {
       addr[0] = parent_value;
       CHECK_EQ(addr[0], parent_value);

       // Notify the child of the new value.
       shared[0] = 1;

       // Wait for the child to ask for a new value;
       while (shared[0] != 2) {
         sched_yield();
       }
       addr[0] = parent_value + 1;
       CHECK_EQ(addr[0], parent_value + 1);

       // Notify the child of a new value.
       shared[0] = 3;
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(addr[0], parent_value + 1);
     }

     // Check that updates done by the parent are visible after a new mmap
     // write-private.
     shared[0] = 0;
     addr[0] = starting_value;
     pid = fork();
     if (pid == 0) {
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       CHECK_EQ(addr[0], starting_value);
       addr[0] = child_value;
       CHECK_EQ(addr[0], child_value);

       // Notify the parent to update the buffer.
       shared[0] = 1;

       // Wait for the parent update.
       while (shared[0] != 2) {
         sched_yield();
       }
       // Test the buffer still contains our own data, and not the parent's.
       CHECK_EQ(addr[0], child_value);

       // Test the buffer contains the parent data after a new mmap.
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       CHECK_EQ(addr[0], parent_value);
       exit(0);
     } else {
       // Wait for the child to start
       while (shared[0] != 1) {
         sched_yield();
       }
       CHECK_EQ(addr[0], starting_value);
       addr[0] = parent_value;
       // Notify the child that the buffer has been written.
       shared[0] = 2;
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(addr[0], parent_value);
     }

     // Check that updates done by the parent are visible for a new mmap
     // write-private that hasn't written to the buffer yet.
     shared[0] = 0;
     addr[0] = starting_value;
     pid = fork();
     if (pid == 0) {
       CHECK_EQ(mmap(addr, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd.get(), 0),
                addr);
       CHECK_EQ(addr[0], starting_value);
       // Notify the parent for a new update of the buffer.
       shared[0] = 1;
       while (addr[0] != parent_value) {
         sched_yield();
       }
       addr[0] = child_value;
       CHECK_EQ(addr[0], child_value);
       exit(0);
     } else {
       while (shared[0] != 1) {
         sched_yield();
       }
       CHECK_EQ(addr[0], starting_value);
       addr[0] = parent_value;
       int status;
       CHECK_EQ(waitpid(pid, &status, 0), pid);
       CHECK(WIFEXITED(status)) << strerror(errno);
       CHECK_EQ(addr[0], parent_value);
     }
     munmap(addr, kPageSize);
     munmap(shared, kPageSize);
   }
 };

 TEST_F(TestZygoteMemory, BasicTest) {
   BasicTest();
 }

 TEST_F(TestZygoteMemory, TestUnmapWritableAfterFork) {
   TestUnmapWritableAfterFork();
 }

 TEST_F(TestZygoteMemory, TestMadviseDontFork) {
   TestMadviseDontFork();
 }

 TEST_F(TestZygoteMemory, TestFromSharedToPrivate) {
   TestFromSharedToPrivate();
 }

 #endif  // defined (__BIONIC__)

 }  // namespace jit
 }  // namespace art
	/*
	* Copyright (C) 2019 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "jit/jit_memory_region.h"

	#include <signal.h>
	#include <sys/mman.h>
	#include <sys/types.h>
	#include <unistd.h>

	#include <android-base/unique_fd.h>
	#include <gtest/gtest.h>

	#include "base/globals.h"
	#include "base/memfd.h"

	namespace art {
	namespace jit {

	// These tests only run on bionic.
	#if defined(__BIONIC__)
	static constexpr int kReturnFromFault = 42;

	// These globals are only set in child processes.
	void* gAddrToFaultOn = nullptr;

	void handler(int ATTRIBUTE_UNUSED, siginfo_t* info, void* ATTRIBUTE_UNUSED) {
	CHECK_EQ(info->si_addr, gAddrToFaultOn);
	exit(kReturnFromFault);
	}

	static void registerSignalHandler() {
	struct sigaction sa;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_SIGINFO;
	sa.sa_sigaction = handler;
	sigaction(SIGSEGV, &sa, nullptr);
	}

	class TestZygoteMemory : public testing::Test {
	public:
	void BasicTest() {
	std::string error_msg;
	size_t size = kPageSize;
	android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd.get(), -1);

	// Create a writable mapping.
	int32_t* addr = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd.get(), 0));
	CHECK(addr != nullptr);
	CHECK_NE(addr, MAP_FAILED);

	// Test that we can write into the mapping.
	addr[0] = 42;
	CHECK_EQ(addr[0], 42);

	// Protect the memory.
	bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
	CHECK(res);

	// Test that we can still write into the mapping.
	addr[0] = 2;
	CHECK_EQ(addr[0], 2);

	// Test that we cannot create another writable mapping.
	int32_t* addr2 = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd.get(), 0));
	CHECK_EQ(addr2, MAP_FAILED);

	// With the existing mapping, we can toggle read/write.
	CHECK_EQ(mprotect(addr, size, PROT_READ), 0) << strerror(errno);
	CHECK_EQ(mprotect(addr, size, PROT_READ \| PROT_WRITE), 0) << strerror(errno);

	// Test mremap with old_size = 0. From the man pages:
	// If the value of old_size is zero, and old_address refers to a shareable mapping
	// (see mmap(2) MAP_SHARED), then mremap() will create a new mapping of the same pages.
	addr2 = reinterpret_cast<int32_t*>(mremap(addr, 0, kPageSize, MREMAP_MAYMOVE));
	CHECK_NE(addr2, MAP_FAILED);

	// Test that we can write into the remapped mapping.
	addr2[0] = 3;
	CHECK_EQ(addr2[0], 3);

	addr2 = reinterpret_cast<int32_t>(mremap(addr, kPageSize, 2 kPageSize, MREMAP_MAYMOVE));
	CHECK_NE(addr2, MAP_FAILED);

	// Test that we can write into the remapped mapping.
	addr2[0] = 4;
	CHECK_EQ(addr2[0], 4);
	}

	void TestUnmapWritableAfterFork() {
	std::string error_msg;
	size_t size = kPageSize;
	int32_t* addr = nullptr;
	int32_t* addr2 = nullptr;
	{
	android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd.get(), -1);

	// Create a writable mapping.
	addr = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd.get(), 0));
	CHECK(addr != nullptr);
	CHECK_NE(addr, MAP_FAILED);

	// Test that we can write into the mapping.
	addr[0] = 42;
	CHECK_EQ(addr[0], 42);

	// Create a read-only mapping.
	addr2 = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ, MAP_SHARED, fd.get(), 0));
	CHECK(addr2 != nullptr);

	// Protect the memory.
	bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
	CHECK(res);
	}
	// At this point, the fd has been dropped, but the memory mappings are still
	// there.

	// Create a mapping of atomic ints to communicate between processes.
	android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd2.get(), -1);
	std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd2.get(), 0));

	// Values used for the tests below.
	const int32_t parent_value = 66;
	const int32_t child_value = 33;
	const int32_t starting_value = 22;

	shared[0] = 0;
	addr[0] = starting_value;
	CHECK_EQ(addr[0], starting_value);
	CHECK_EQ(addr2[0], starting_value);
	pid_t pid = fork();
	if (pid == 0) {
	// Test that we can write into the mapping.
	addr[0] = child_value;
	CHECK_EQ(addr[0], child_value);
	CHECK_EQ(addr2[0], child_value);

	// Unmap the writable mappping.
	munmap(addr, kPageSize);

	CHECK_EQ(addr2[0], child_value);

	// Notify parent process.
	shared[0] = 1;

	// Wait for parent process for a new value.
	while (shared[0] != 2) {
	sched_yield();
	}
	CHECK_EQ(addr2[0], parent_value);

	// Test that we cannot write into the mapping. The signal handler will
	// exit the process.
	gAddrToFaultOn = addr;
	registerSignalHandler();
	// This write will trigger a fault, as `addr` is unmapped.
	addr[0] = child_value + 1;
	exit(0);
	} else {
	while (shared[0] != 1) {
	sched_yield();
	}
	CHECK_EQ(addr[0], child_value);
	CHECK_EQ(addr2[0], child_value);
	addr[0] = parent_value;
	// Notify the child if the new value.
	shared[0] = 2;
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(WEXITSTATUS(status), kReturnFromFault);
	CHECK_EQ(addr[0], parent_value);
	CHECK_EQ(addr2[0], parent_value);
	munmap(addr, kPageSize);
	munmap(addr2, kPageSize);
	munmap(shared, kPageSize);
	}
	}

	void TestMadviseDontFork() {
	std::string error_msg;
	size_t size = kPageSize;
	int32_t* addr = nullptr;
	int32_t* addr2 = nullptr;
	{
	android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd.get(), -1);

	// Create a writable mapping.
	addr = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd.get(), 0));
	CHECK(addr != nullptr);
	CHECK_NE(addr, MAP_FAILED);
	CHECK_EQ(madvise(addr, kPageSize, MADV_DONTFORK), 0);

	// Test that we can write into the mapping.
	addr[0] = 42;
	CHECK_EQ(addr[0], 42);

	// Create a read-only mapping.
	addr2 = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ, MAP_SHARED, fd.get(), 0));
	CHECK(addr2 != nullptr);

	// Protect the memory.
	bool res = JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg);
	CHECK(res);
	}
	// At this point, the fd has been dropped, but the memory mappings are still
	// there.

	// Create a mapping of atomic ints to communicate between processes.
	android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd2.get(), -1);
	std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd2.get(), 0));

	// Values used for the tests below.
	const int32_t parent_value = 66;
	const int32_t child_value = 33;
	const int32_t starting_value = 22;

	shared[0] = 0;
	addr[0] = starting_value;
	CHECK_EQ(addr[0], starting_value);
	CHECK_EQ(addr2[0], starting_value);
	pid_t pid = fork();
	if (pid == 0) {
	CHECK_EQ(addr2[0], starting_value);

	// Notify parent process.
	shared[0] = 1;

	// Wait for parent process for new value.
	while (shared[0] != 2) {
	sched_yield();
	}

	CHECK_EQ(addr2[0], parent_value);
	// Test that we cannot write into the mapping. The signal handler will
	// exit the process.
	gAddrToFaultOn = addr;
	registerSignalHandler();
	addr[0] = child_value + 1;
	exit(0);
	} else {
	while (shared[0] != 1) {
	sched_yield();
	}
	CHECK_EQ(addr[0], starting_value);
	CHECK_EQ(addr2[0], starting_value);
	addr[0] = parent_value;
	// Notify the child of the new value.
	shared[0] = 2;
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(WEXITSTATUS(status), kReturnFromFault);
	CHECK_EQ(addr[0], parent_value);
	CHECK_EQ(addr2[0], parent_value);

	munmap(addr, kPageSize);
	munmap(addr2, kPageSize);
	munmap(shared, kPageSize);
	}
	}

	// This code is testing some behavior that ART could potentially use: get a
	// copy-on-write mapping that can incorporate changes from a shared mapping
	// owned by another process.
	void TestFromSharedToPrivate() {
	// This test is only for memfd with future write sealing support:
	// 1) ashmem with PROT_READ doesn't permit mapping MAP_PRIVATE \| PROT_WRITE
	// 2) ashmem mapped MAP_PRIVATE discards the contents already written.
	if (!art::IsSealFutureWriteSupported()) {
	return;
	}
	std::string error_msg;
	size_t size = kPageSize;
	int32_t* addr = nullptr;
	android::base::unique_fd fd(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd.get(), -1);

	// Create a writable mapping.
	addr = reinterpret_cast<int32_t*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd.get(), 0));
	CHECK(addr != nullptr);
	CHECK_NE(addr, MAP_FAILED);

	// Test that we can write into the mapping.
	addr[0] = 42;
	CHECK_EQ(addr[0], 42);

	// Create another mapping of atomic ints to communicate between processes.
	android::base::unique_fd fd2(JitMemoryRegion::CreateZygoteMemory(size, &error_msg));
	CHECK_NE(fd2.get(), -1);
	std::atomic<int32_t>* shared = reinterpret_cast<std::atomic<int32_t>*>(
	mmap(nullptr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED, fd2.get(), 0));

	// Protect the memory.
	CHECK(JitMemoryRegion::ProtectZygoteMemory(fd.get(), &error_msg));

	// Values used for the tests below.
	const int32_t parent_value = 66;
	const int32_t child_value = 33;
	const int32_t starting_value = 22;

	// Check that updates done by a child mapping write-private are not visible
	// to the parent.
	addr[0] = starting_value;
	shared[0] = 0;
	pid_t pid = fork();
	if (pid == 0) {
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	addr[0] = child_value;
	exit(0);
	} else {
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(addr[0], starting_value);
	}

	addr[0] = starting_value;
	shared[0] = 0;

	// Check getting back and forth on shared mapping.
	pid = fork();
	if (pid == 0) {
	// Map it private with write access. MAP_FIXED will replace the existing
	// mapping.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	addr[0] = child_value;
	CHECK_EQ(addr[0], child_value);

	// Check that mapping shared with write access fails.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_FIXED, fd.get(), 0),
	MAP_FAILED);
	CHECK_EQ(errno, EPERM);

	// Map shared with read access.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ, MAP_SHARED \| MAP_FIXED, fd.get(), 0), addr);
	CHECK_NE(addr[0], child_value);

	// Wait for the parent to notify.
	while (shared[0] != 1) {
	sched_yield();
	}
	CHECK_EQ(addr[0], parent_value);

	// Notify the parent for getting a new update of the buffer.
	shared[0] = 2;

	// Map it private again.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	addr[0] = child_value + 1;
	CHECK_EQ(addr[0], child_value + 1);

	// And map it back shared.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ, MAP_SHARED \| MAP_FIXED, fd.get(), 0), addr);
	while (shared[0] != 3) {
	sched_yield();
	}
	CHECK_EQ(addr[0], parent_value + 1);
	exit(0);
	} else {
	addr[0] = parent_value;
	CHECK_EQ(addr[0], parent_value);

	// Notify the child of the new value.
	shared[0] = 1;

	// Wait for the child to ask for a new value;
	while (shared[0] != 2) {
	sched_yield();
	}
	addr[0] = parent_value + 1;
	CHECK_EQ(addr[0], parent_value + 1);

	// Notify the child of a new value.
	shared[0] = 3;
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(addr[0], parent_value + 1);
	}

	// Check that updates done by the parent are visible after a new mmap
	// write-private.
	shared[0] = 0;
	addr[0] = starting_value;
	pid = fork();
	if (pid == 0) {
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	CHECK_EQ(addr[0], starting_value);
	addr[0] = child_value;
	CHECK_EQ(addr[0], child_value);

	// Notify the parent to update the buffer.
	shared[0] = 1;

	// Wait for the parent update.
	while (shared[0] != 2) {
	sched_yield();
	}
	// Test the buffer still contains our own data, and not the parent's.
	CHECK_EQ(addr[0], child_value);

	// Test the buffer contains the parent data after a new mmap.
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	CHECK_EQ(addr[0], parent_value);
	exit(0);
	} else {
	// Wait for the child to start
	while (shared[0] != 1) {
	sched_yield();
	}
	CHECK_EQ(addr[0], starting_value);
	addr[0] = parent_value;
	// Notify the child that the buffer has been written.
	shared[0] = 2;
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(addr[0], parent_value);
	}

	// Check that updates done by the parent are visible for a new mmap
	// write-private that hasn't written to the buffer yet.
	shared[0] = 0;
	addr[0] = starting_value;
	pid = fork();
	if (pid == 0) {
	CHECK_EQ(mmap(addr, kPageSize, PROT_READ \| PROT_WRITE, MAP_PRIVATE \| MAP_FIXED, fd.get(), 0),
	addr);
	CHECK_EQ(addr[0], starting_value);
	// Notify the parent for a new update of the buffer.
	shared[0] = 1;
	while (addr[0] != parent_value) {
	sched_yield();
	}
	addr[0] = child_value;
	CHECK_EQ(addr[0], child_value);
	exit(0);
	} else {
	while (shared[0] != 1) {
	sched_yield();
	}
	CHECK_EQ(addr[0], starting_value);
	addr[0] = parent_value;
	int status;
	CHECK_EQ(waitpid(pid, &status, 0), pid);
	CHECK(WIFEXITED(status)) << strerror(errno);
	CHECK_EQ(addr[0], parent_value);
	}
	munmap(addr, kPageSize);
	munmap(shared, kPageSize);
	}
	};

	TEST_F(TestZygoteMemory, BasicTest) {
	BasicTest();
	}

	TEST_F(TestZygoteMemory, TestUnmapWritableAfterFork) {
	TestUnmapWritableAfterFork();
	}

	TEST_F(TestZygoteMemory, TestMadviseDontFork) {
	TestMadviseDontFork();
	}

	TEST_F(TestZygoteMemory, TestFromSharedToPrivate) {
	TestFromSharedToPrivate();
	}

	#endif // defined (__BIONIC__)

	} // namespace jit
	} // namespace art