gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/test/syscalls/linux/splice.cc

// Copyright 2019 The gVisor Authors.
//
// 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 <fcntl.h>
#include <linux/unistd.h>
#include <sys/eventfd.h>
#include <sys/resource.h>
#include <sys/sendfile.h>
#include <sys/time.h>
#include <unistd.h>

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/cleanup/cleanup.h"
#include "absl/strings/string_view.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "test/util/file_descriptor.h"
#include "test/util/memory_util.h"
#include "test/util/signal_util.h"
#include "test/util/temp_path.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"
#include "test/util/timer_util.h"

namespace gvisor {
namespace testing {

namespace {

TEST(SpliceTest, TwoRegularFiles) {
  // Create temp files.
  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());

  // Open the input file as read only.
  const FileDescriptor in_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDONLY));

  // Open the output file as write only.
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_WRONLY));

  // Verify that it is rejected as expected; regardless of offsets.
  loff_t in_offset = 0;
  loff_t out_offset = 0;
  EXPECT_THAT(splice(in_fd.get(), &in_offset, out_fd.get(), &out_offset, 1, 0),
              SyscallFailsWithErrno(EINVAL));
  EXPECT_THAT(splice(in_fd.get(), nullptr, out_fd.get(), &out_offset, 1, 0),
              SyscallFailsWithErrno(EINVAL));
  EXPECT_THAT(splice(in_fd.get(), &in_offset, out_fd.get(), nullptr, 1, 0),
              SyscallFailsWithErrno(EINVAL));
  EXPECT_THAT(splice(in_fd.get(), nullptr, out_fd.get(), nullptr, 1, 0),
              SyscallFailsWithErrno(EINVAL));
}

int memfd_create(const std::string& name, unsigned int flags) {
  return syscall(__NR_memfd_create, name.c_str(), flags);
}

TEST(SpliceTest, NegativeOffset) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill the pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Open the output file as write only.
  int fd;
  EXPECT_THAT(fd = memfd_create("negative", 0), SyscallSucceeds());
  const FileDescriptor out_fd(fd);

  loff_t out_offset = 0xffffffffffffffffull;
  constexpr int kSize = 2;
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), &out_offset, kSize, 0),
              SyscallFailsWithErrno(EINVAL));
}

// Write offset + size overflows int64.
//
// This is a regression test for b/148041624.
TEST(SpliceTest, WriteOverflow) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill the pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Open the output file.
  int fd;
  EXPECT_THAT(fd = memfd_create("overflow", 0), SyscallSucceeds());
  const FileDescriptor out_fd(fd);

  // out_offset + kSize overflows INT64_MAX.
  loff_t out_offset = 0x7ffffffffffffffeull;
  constexpr int kSize = 3;
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), &out_offset, kSize, 0),
              SyscallFailsWithErrno(EINVAL));
}

TEST(SpliceTest, SamePipe) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill the pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Attempt to splice to itself.
  EXPECT_THAT(splice(rfd.get(), nullptr, wfd.get(), nullptr, kPageSize, 0),
              SyscallFailsWithErrno(EINVAL));
}

TEST(TeeTest, SamePipe) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill the pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Attempt to tee to itself.
  EXPECT_THAT(tee(rfd.get(), wfd.get(), kPageSize, 0),
              SyscallFailsWithErrno(EINVAL));
}

TEST(TeeTest, RegularFile) {
  // Open some file.
  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor in_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));

  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Attempt to tee from the file.
  EXPECT_THAT(tee(in_fd.get(), wfd.get(), kPageSize, 0),
              SyscallFailsWithErrno(EINVAL));
  EXPECT_THAT(tee(rfd.get(), in_fd.get(), kPageSize, 0),
              SyscallFailsWithErrno(EINVAL));
}

TEST(SpliceTest, PipeOffsets) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // All pipe offsets should be rejected.
  loff_t in_offset = 0;
  loff_t out_offset = 0;
  EXPECT_THAT(splice(rfd1.get(), &in_offset, wfd2.get(), &out_offset, 1, 0),
              SyscallFailsWithErrno(ESPIPE));
  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), &out_offset, 1, 0),
              SyscallFailsWithErrno(ESPIPE));
  EXPECT_THAT(splice(rfd1.get(), &in_offset, wfd2.get(), nullptr, 1, 0),
              SyscallFailsWithErrno(ESPIPE));
}

TEST(SpliceTest, ToPipe) {
  // Open the input file.
  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor in_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(in_fd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));
  ASSERT_THAT(lseek(in_fd.get(), 0, SEEK_SET), SyscallSucceedsWithValue(0));

  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Splice to the pipe.
  EXPECT_THAT(splice(in_fd.get(), nullptr, wfd.get(), nullptr, kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));

  // Contents should be equal.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), buf.size()), 0);
}

TEST(SpliceTest, ToPipeEOF) {
  // Create and open an empty input file.
  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor in_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDONLY));

  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Splice from the empty file to the pipe.
  EXPECT_THAT(splice(in_fd.get(), nullptr, wfd.get(), nullptr, 123, 0),
              SyscallSucceedsWithValue(0));
}

TEST(SpliceTest, ToPipeOffset) {
  // Open the input file.
  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor in_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(in_fd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Splice to the pipe.
  loff_t in_offset = kPageSize / 2;
  EXPECT_THAT(
      splice(in_fd.get(), &in_offset, wfd.get(), nullptr, kPageSize / 2, 0),
      SyscallSucceedsWithValue(kPageSize / 2));

  // Contents should be equal to only the second part.
  std::vector<char> rbuf(kPageSize / 2);
  ASSERT_THAT(read(rfd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize / 2));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data() + (kPageSize / 2), rbuf.size()), 0);
}

TEST(SpliceTest, FromPipe) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Open the output file.
  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));

  // Splice to the output file.
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), nullptr, kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));

  // The offset of the output should be equal to kPageSize. We assert that and
  // reset to zero so that we can read the contents and ensure they match.
  EXPECT_THAT(lseek(out_fd.get(), 0, SEEK_CUR),
              SyscallSucceedsWithValue(kPageSize));
  ASSERT_THAT(lseek(out_fd.get(), 0, SEEK_SET), SyscallSucceedsWithValue(0));

  // Contents should be equal.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(out_fd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), buf.size()), 0);
}

TEST(SpliceTest, FromPipeMultiple) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  std::string buf = "abcABC123";
  ASSERT_THAT(write(wfd.get(), buf.c_str(), buf.size()),
              SyscallSucceedsWithValue(buf.size()));

  // Open the output file.
  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));

  // Splice from the pipe to the output file over several calls.
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), nullptr, 3, 0),
              SyscallSucceedsWithValue(3));
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), nullptr, 3, 0),
              SyscallSucceedsWithValue(3));
  EXPECT_THAT(splice(rfd.get(), nullptr, out_fd.get(), nullptr, 3, 0),
              SyscallSucceedsWithValue(3));

  // Reset cursor to zero so that we can check the contents.
  ASSERT_THAT(lseek(out_fd.get(), 0, SEEK_SET), SyscallSucceedsWithValue(0));

  // Contents should be equal.
  std::vector<char> rbuf(buf.size());
  ASSERT_THAT(read(out_fd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(rbuf.size()));
  EXPECT_EQ(memcmp(rbuf.data(), buf.c_str(), buf.size()), 0);
}

TEST(SpliceTest, FromPipeOffset) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Open the input file.
  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));

  // Splice to the output file.
  loff_t out_offset = kPageSize / 2;
  EXPECT_THAT(
      splice(rfd.get(), nullptr, out_fd.get(), &out_offset, kPageSize, 0),
      SyscallSucceedsWithValue(kPageSize));

  // Content should reflect the splice. We write to a specific offset in the
  // file, so the internals should now be allocated sparsely.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(out_fd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  std::vector<char> zbuf(kPageSize / 2);
  memset(zbuf.data(), 0, zbuf.size());
  EXPECT_EQ(memcmp(rbuf.data(), zbuf.data(), zbuf.size()), 0);
  EXPECT_EQ(memcmp(rbuf.data() + kPageSize / 2, buf.data(), kPageSize / 2), 0);
}

TEST(SpliceTest, TwoPipes) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Splice to the second pipe, using two operations.
  EXPECT_THAT(
      splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize / 2, 0),
      SyscallSucceedsWithValue(kPageSize / 2));
  EXPECT_THAT(
      splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize / 2, 0),
      SyscallSucceedsWithValue(kPageSize / 2));

  // Content should reflect the splice.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
}

TEST(SpliceTest, TwoPipesPartialRead) {
  // Create two pipes.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor first_rfd(fds[0]);
  const FileDescriptor first_wfd(fds[1]);
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor second_rfd(fds[0]);
  const FileDescriptor second_wfd(fds[1]);

  // Write half a page of data to the first pipe.
  std::vector<char> buf(kPageSize / 2);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(first_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize / 2));

  // Attempt to splice one page from the first pipe to the second; it should
  // immediately return after splicing the half-page previously written to the
  // first pipe.
  EXPECT_THAT(
      splice(first_rfd.get(), nullptr, second_wfd.get(), nullptr, kPageSize, 0),
      SyscallSucceedsWithValue(kPageSize / 2));
}

TEST(SpliceTest, TwoPipesPartialWrite) {
  // Create two pipes.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor first_rfd(fds[0]);
  const FileDescriptor first_wfd(fds[1]);
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor second_rfd(fds[0]);
  const FileDescriptor second_wfd(fds[1]);

  // Write two pages of data to the first pipe.
  std::vector<char> buf(2 * kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(first_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(2 * kPageSize));

  // Limit the second pipe to two pages, then write one page of data to it.
  ASSERT_THAT(fcntl(second_wfd.get(), F_SETPIPE_SZ, 2 * kPageSize),
              SyscallSucceeds());
  ASSERT_THAT(write(second_wfd.get(), buf.data(), buf.size() / 2),
              SyscallSucceedsWithValue(kPageSize));

  // Attempt to splice two pages from the first pipe to the second; it should
  // immediately return after splicing the first page previously written to the
  // first pipe.
  EXPECT_THAT(splice(first_rfd.get(), nullptr, second_wfd.get(), nullptr,
                     2 * kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));
}

TEST(TeeTest, TwoPipesPartialRead) {
  // Create two pipes.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor first_rfd(fds[0]);
  const FileDescriptor first_wfd(fds[1]);
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor second_rfd(fds[0]);
  const FileDescriptor second_wfd(fds[1]);

  // Write half a page of data to the first pipe.
  std::vector<char> buf(kPageSize / 2);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(first_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize / 2));

  // Attempt to tee one page from the first pipe to the second; it should
  // immediately return after copying the half-page previously written to the
  // first pipe.
  EXPECT_THAT(tee(first_rfd.get(), second_wfd.get(), kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize / 2));
}

TEST(TeeTest, TwoPipesPartialWrite) {
  // Create two pipes.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor first_rfd(fds[0]);
  const FileDescriptor first_wfd(fds[1]);
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor second_rfd(fds[0]);
  const FileDescriptor second_wfd(fds[1]);

  // Write two pages of data to the first pipe.
  std::vector<char> buf(2 * kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(first_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(2 * kPageSize));

  // Limit the second pipe to two pages, then write one page of data to it.
  ASSERT_THAT(fcntl(second_wfd.get(), F_SETPIPE_SZ, 2 * kPageSize),
              SyscallSucceeds());
  ASSERT_THAT(write(second_wfd.get(), buf.data(), buf.size() / 2),
              SyscallSucceedsWithValue(kPageSize));

  // Attempt to tee two pages from the first pipe to the second; it should
  // immediately return after copying the first page previously written to the
  // first pipe.
  EXPECT_THAT(tee(first_rfd.get(), second_wfd.get(), 2 * kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));
}

TEST(SpliceTest, TwoPipesCircular) {
  // Create two pipes.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor first_rfd(fds[0]);
  const FileDescriptor first_wfd(fds[1]);
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor second_rfd(fds[0]);
  const FileDescriptor second_wfd(fds[1]);

  // On Linux, each pipe is normally limited to
  // include/linux/pipe_fs_i.h:PIPE_DEF_BUFFERS buffers worth of data.
  constexpr size_t PIPE_DEF_BUFFERS = 16;

  // Write some data to each pipe. Below we splice 1 byte at a time between
  // pipes, which very quickly causes each byte to be stored in a separate
  // buffer, so we must ensure that the total amount of data in the system is <=
  // PIPE_DEF_BUFFERS bytes.
  std::vector<char> buf(PIPE_DEF_BUFFERS / 2);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(first_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(buf.size()));
  ASSERT_THAT(write(second_wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(buf.size()));

  // Have another thread splice from the second pipe to the first, while we
  // splice from the first to the second. The test passes if this does not
  // deadlock.
  const int kIterations = 1000;
  DisableSave ds;
  ScopedThread t([&]() {
    for (int i = 0; i < kIterations; i++) {
      ASSERT_THAT(
          splice(second_rfd.get(), nullptr, first_wfd.get(), nullptr, 1, 0),
          SyscallSucceedsWithValue(1));
    }
  });
  for (int i = 0; i < kIterations; i++) {
    ASSERT_THAT(
        splice(first_rfd.get(), nullptr, second_wfd.get(), nullptr, 1, 0),
        SyscallSucceedsWithValue(1));
  }
}

TEST(SpliceTest, Blocking) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // This thread writes to the main pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ScopedThread t([&]() {
    ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
                SyscallSucceedsWithValue(kPageSize));
  });

  // Attempt a splice immediately; it should block.
  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));

  // Thread should be joinable.
  t.Join();

  // Content should reflect the splice.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
}

TEST(TeeTest, Blocking) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // This thread writes to the main pipe.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ScopedThread t([&]() {
    ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
                SyscallSucceedsWithValue(kPageSize));
  });

  // Attempt a tee immediately; it should block.
  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));

  // Thread should be joinable.
  t.Join();

  // Content should reflect the splice, in both pipes.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
  ASSERT_THAT(read(rfd1.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
}

TEST(TeeTest, BlockingWrite) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // Make some data available to be read.
  std::vector<char> buf1(kPageSize);
  RandomizeBuffer(buf1.data(), buf1.size());
  ASSERT_THAT(write(wfd1.get(), buf1.data(), buf1.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Fill up the write pipe's buffer.
  int pipe_size = -1;
  ASSERT_THAT(pipe_size = fcntl(wfd2.get(), F_GETPIPE_SZ), SyscallSucceeds());
  std::vector<char> buf2(pipe_size);
  ASSERT_THAT(write(wfd2.get(), buf2.data(), buf2.size()),
              SyscallSucceedsWithValue(pipe_size));

  ScopedThread t([&]() {
    absl::SleepFor(absl::Milliseconds(100));
    ASSERT_THAT(read(rfd2.get(), buf2.data(), buf2.size()),
                SyscallSucceedsWithValue(pipe_size));
  });

  // Attempt a tee immediately; it should block.
  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), kPageSize, 0),
              SyscallSucceedsWithValue(kPageSize));

  // Thread should be joinable.
  t.Join();

  // Content should reflect the tee.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf1.data(), kPageSize), 0);
}

TEST(SpliceTest, NonBlocking) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // Splice with no data to back it.
  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize,
                     SPLICE_F_NONBLOCK),
              SyscallFailsWithErrno(EAGAIN));
}

TEST(TeeTest, NonBlocking) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // Splice with no data to back it.
  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), kPageSize, SPLICE_F_NONBLOCK),
              SyscallFailsWithErrno(EAGAIN));
}

TEST(TeeTest, MultiPage) {
  // Create two new pipes.
  int first[2], second[2];
  ASSERT_THAT(pipe(first), SyscallSucceeds());
  const FileDescriptor rfd1(first[0]);
  const FileDescriptor wfd1(first[1]);
  ASSERT_THAT(pipe(second), SyscallSucceeds());
  const FileDescriptor rfd2(second[0]);
  const FileDescriptor wfd2(second[1]);

  // Make some data available to be read.
  std::vector<char> wbuf(8 * kPageSize);
  RandomizeBuffer(wbuf.data(), wbuf.size());
  ASSERT_THAT(write(wfd1.get(), wbuf.data(), wbuf.size()),
              SyscallSucceedsWithValue(wbuf.size()));

  // Attempt a tee immediately; it should complete.
  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), wbuf.size(), 0),
              SyscallSucceedsWithValue(wbuf.size()));

  // Content should reflect the tee.
  std::vector<char> rbuf(wbuf.size());
  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(rbuf.size()));
  EXPECT_EQ(memcmp(rbuf.data(), wbuf.data(), rbuf.size()), 0);
  ASSERT_THAT(read(rfd1.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(rbuf.size()));
  EXPECT_EQ(memcmp(rbuf.data(), wbuf.data(), rbuf.size()), 0);
}

TEST(SpliceTest, FromPipeMaxFileSize) {
  // Create a new pipe.
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);

  // Fill with some random data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
              SyscallSucceedsWithValue(kPageSize));

  // Open the input file.
  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));

  EXPECT_THAT(ftruncate(out_fd.get(), 13 << 20), SyscallSucceeds());
  EXPECT_THAT(lseek(out_fd.get(), 0, SEEK_END),
              SyscallSucceedsWithValue(13 << 20));

  // Set our file size limit.
  sigset_t set;
  sigemptyset(&set);
  sigaddset(&set, SIGXFSZ);
  TEST_PCHECK(sigprocmask(SIG_BLOCK, &set, nullptr) == 0);
  rlimit rlim = {};
  rlim.rlim_cur = rlim.rlim_max = (13 << 20);
  EXPECT_THAT(setrlimit(RLIMIT_FSIZE, &rlim), SyscallSucceeds());

  // Splice to the output file.
  EXPECT_THAT(
      splice(rfd.get(), nullptr, out_fd.get(), nullptr, 3 * kPageSize, 0),
      SyscallFailsWithErrno(EFBIG));

  // Contents should be equal.
  std::vector<char> rbuf(kPageSize);
  ASSERT_THAT(read(rfd.get(), rbuf.data(), rbuf.size()),
              SyscallSucceedsWithValue(kPageSize));
  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), buf.size()), 0);
}

static volatile int signaled = 0;
void SigUsr1Handler(int sig, siginfo_t* info, void* context) { signaled = 1; }

TEST(SpliceTest, ToPipeWithSmallCapacityDoesNotSpin) {
  // Writes to a pipe that are less than PIPE_BUF must be atomic. This test
  // creates a pipe with only 128 bytes of capacity (< PIPE_BUF) and checks that
  // splicing to the pipe does not spin. See b/170743336.

  // Create a file with one page of data.
  std::vector<char> buf(kPageSize);
  RandomizeBuffer(buf.data(), buf.size());
  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
      GetAbsoluteTestTmpdir(), absl::string_view(buf.data(), buf.size()),
      TempPath::kDefaultFileMode));
  auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_RDONLY));

  // Create a pipe with size 4096, and fill all but 128 bytes of it.
  int p[2];
  ASSERT_THAT(pipe(p), SyscallSucceeds());
  ASSERT_THAT(fcntl(p[1], F_SETPIPE_SZ, kPageSize), SyscallSucceeds());
  const int kWriteSize = kPageSize - 128;
  std::vector<char> writeBuf(kWriteSize);
  RandomizeBuffer(writeBuf.data(), writeBuf.size());
  ASSERT_THAT(write(p[1], writeBuf.data(), writeBuf.size()),
              SyscallSucceedsWithValue(kWriteSize));

  // Set up signal handler.
  struct sigaction sa = {};
  sa.sa_sigaction = SigUsr1Handler;
  sa.sa_flags = SA_SIGINFO;
  const auto cleanup_sigact =
      ASSERT_NO_ERRNO_AND_VALUE(ScopedSigaction(SIGUSR1, sa));

  // Send SIGUSR1 to this thread in 1 second.
  struct sigevent sev = {};
  sev.sigev_notify = SIGEV_THREAD_ID;
  sev.sigev_signo = SIGUSR1;
  sev.sigev_notify_thread_id = gettid();
  auto timer = ASSERT_NO_ERRNO_AND_VALUE(TimerCreate(CLOCK_MONOTONIC, sev));
  struct itimerspec its = {};
  its.it_value = absl::ToTimespec(absl::Seconds(1));
  DisableSave ds;  // Asserting an EINTR.
  ASSERT_NO_ERRNO(timer.Set(0, its));

  // Now splice the file to the pipe. This should block, but not spin, and
  // should return EINTR because it is interrupted by the signal.
  EXPECT_THAT(splice(fd.get(), nullptr, p[1], nullptr, kPageSize, 0),
              SyscallFailsWithErrno(EINTR));

  // Alarm should have been handled.
  EXPECT_EQ(signaled, 1);
}

// Regression test for b/208679047.
TEST(SpliceTest, FromPipeWithConcurrentIo) {
  // Create a file containing two copies of the same byte. Two bytes are
  // necessary because both the read() and splice() loops below advance the file
  // offset by one byte before lseek(); use of the file offset is required since
  // the mutex protecting the file offset is implicated in the circular lock
  // ordering that this test attempts to reproduce.
  //
  // This can't use memfd_create() because, in Linux, memfd_create(2) creates a
  // struct file using alloc_file_pseudo() without going through
  // do_dentry_open(), so FMODE_ATOMIC_POS is not set despite the created file
  // having type S_IFREG ("regular file").
  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
  const FileDescriptor fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_RDWR));
  constexpr char kSplicedByte = 0x01;
  for (int i = 0; i < 2; i++) {
    ASSERT_THAT(WriteFd(fd.get(), &kSplicedByte, 1),
                SyscallSucceedsWithValue(1));
  }

  // Create a pipe.
  int pipe_fds[2];
  ASSERT_THAT(pipe(pipe_fds), SyscallSucceeds());
  const FileDescriptor rfd(pipe_fds[0]);
  FileDescriptor wfd(pipe_fds[1]);

  DisableSave ds;
  std::atomic<bool> done(false);

  // Create a thread that reads from fd until the end of the test.
  ScopedThread memfd_reader([&] {
    char file_buf;
    while (!done.load()) {
      ASSERT_THAT(lseek(fd.get(), 0, SEEK_SET), SyscallSucceeds());
      int n = ReadFd(fd.get(), &file_buf, 1);
      if (n == 0) {
        // fd was at offset 2 (EOF). In Linux, this is possible even after
        // lseek(0) because splice() doesn't attempt atomicity with respect to
        // concurrent lseek(), so the effect of lseek() may be lost.
        continue;
      }
      ASSERT_THAT(n, SyscallSucceedsWithValue(1));
      ASSERT_EQ(file_buf, kSplicedByte);
    }
  });

  // Create a thread that reads from the pipe until the end of the test.
  ScopedThread pipe_reader([&] {
    char pipe_buf;
    while (!done.load()) {
      int n = ReadFd(rfd.get(), &pipe_buf, 1);
      if (n == 0) {
        // This should only happen due to cleanup_threads (below) closing wfd.
        EXPECT_TRUE(done.load());
        return;
      }
      ASSERT_THAT(n, SyscallSucceedsWithValue(1));
      ASSERT_EQ(pipe_buf, kSplicedByte);
    }
  });

  // Create a thread that repeatedly invokes madvise(MADV_DONTNEED) on the same
  // page of memory. (Having a thread attempt to lock MM.activeMu for writing is
  // necessary to create a deadlock from the circular lock ordering, since
  // otherwise both uses of MM.activeMu are for reading and may proceed
  // concurrently.)
  ScopedThread mm_locker([&] {
    const Mapping m = ASSERT_NO_ERRNO_AND_VALUE(
        MmapAnon(kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE));
    while (!done.load()) {
      madvise(m.ptr(), kPageSize, MADV_DONTNEED);
    }
  });

  // This must come after the ScopedThreads since its destructor must run before
  // theirs.
  const absl::Cleanup cleanup_threads = [&] {
    done.store(true);
    // Ensure that pipe_reader is unblocked after setting done, so that it will
    // be able to observe done being true.
    wfd.reset();
  };

  // Repeatedly splice from memfd to the pipe. The test passes if this does not
  // deadlock.
  const int kIterations = 5000;
  for (int i = 0; i < kIterations; i++) {
    ASSERT_THAT(lseek(fd.get(), 0, SEEK_SET), SyscallSucceeds());
    ASSERT_THAT(splice(fd.get(), nullptr, wfd.get(), nullptr, 1, 0),
                SyscallSucceedsWithValue(1));
  }
}

// Regression test for #9736 and #10046.
TEST(SpliceTest, FromPipeWithWriterToDevNull) {
  int fds[2];
  ASSERT_THAT(pipe(fds), SyscallSucceeds());
  const FileDescriptor rfd(fds[0]);
  const FileDescriptor wfd(fds[1]);
  const FileDescriptor out_fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/null", O_WRONLY));

  // Write one byte to the pipe and expect it to be successfully spliced to
  // /dev/null.
  constexpr char kSplicedByte = '.';
  ASSERT_THAT(WriteFd(wfd.get(), &kSplicedByte, 1),
              SyscallSucceedsWithValue(1));
  ASSERT_THAT(
      splice(rfd.get(), nullptr, out_fd.get(), nullptr, 1, SPLICE_F_NONBLOCK),
      SyscallSucceedsWithValue(1));

  // Expect that splicing from the pipe again fails with EAGAIN since the pipe
  // is now empty.
  ASSERT_THAT(
      splice(rfd.get(), nullptr, out_fd.get(), nullptr, 1, SPLICE_F_NONBLOCK),
      SyscallFailsWithErrno(EAGAIN));
}

}  // namespace

}  // namespace testing
}  // namespace gvisor