[libc] add ioctl (#141393)

Closes #85275
Closes #90317
Updates #97191

---------

Co-authored-by: Joseph Huber <huberjn@outlook.com>
Co-authored-by: Michael Jones <michaelrj@google.com>

libc/test/src/sys/CMakeLists.txt

@@ -13,3 +13,4 @@ add_subdirectory(auxv)
 add_subdirectory(epoll)
 add_subdirectory(uio)
 add_subdirectory(time)
+add_subdirectory(ioctl)

libc/test/src/sys/ioctl/CMakeLists.txt

@@ -0,0 +1,3 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${LIBC_TARGET_OS})
+endif()

libc/test/src/sys/ioctl/linux/CMakeLists.txt

@@ -0,0 +1,17 @@
+add_custom_target(libc_sys_ioctl_unittests)
+
+add_libc_unittest(
+  ioctl_test
+  SUITE
+    libc_sys_ioctl_unittests
+  SRCS
+    ioctl_test.cpp
+  DEPENDS
+    libc.hdr.ioctl_macros
+    libc.src.sys.ioctl.ioctl
+    libc.src.errno.errno
+    libc.src.fcntl.open
+    libc.src.unistd.close
+    libc.src.unistd.read
+    libc.src.unistd.write
+)

libc/test/src/sys/ioctl/linux/ioctl_test.cpp

@@ -0,0 +1,75 @@
+//===-- Unittests for ioctl -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/errno/libc_errno.h"
+#include "src/fcntl/open.h"
+#include "src/sys/ioctl/ioctl.h"
+#include "src/unistd/close.h"
+#include "src/unistd/read.h"
+#include "src/unistd/write.h"
+
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+#include "hdr/sys_stat_macros.h"
+
+#include "hdr/sys_ioctl_macros.h"
+
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+TEST(LlvmLibcSysIoctlTest, InvalidCommandAndFIONREAD) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  // Setup the test file
+  constexpr const char *TEST_FILE_NAME = "ioctl.test";
+  constexpr const char TEST_MSG[] = "ioctl test";
+  constexpr int TEST_MSG_SIZE = sizeof(TEST_MSG) - 1;
+  auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
+  int new_test_file_fd = LIBC_NAMESPACE::open(
+      TEST_FILE, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+  ASSERT_THAT(
+      (int)LIBC_NAMESPACE::write(new_test_file_fd, TEST_MSG, TEST_MSG_SIZE),
+      Succeeds(TEST_MSG_SIZE));
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_THAT(LIBC_NAMESPACE::close(new_test_file_fd), Succeeds(0));
+  ASSERT_ERRNO_SUCCESS();
+
+  // Reopen the file for testing
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_RDONLY);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GT(fd, 0);
+
+  // FIONREAD reports the number of available bytes to read for the passed fd
+  // This will report the full size of the file, as we haven't read anything yet
+  int n = -1;
+  int ret = LIBC_NAMESPACE::ioctl(fd, FIONREAD, &n);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GT(ret, -1);
+  ASSERT_EQ(n, TEST_MSG_SIZE);
+
+  // But if we read some bytes...
+  constexpr int READ_COUNT = 5;
+  char read_buffer[READ_COUNT];
+  ASSERT_THAT((int)LIBC_NAMESPACE::read(fd, read_buffer, READ_COUNT),
+              Succeeds(READ_COUNT));
+
+  // ... n should have decreased by the number of bytes we've read
+  int n_after_reading = -1;
+  ret = LIBC_NAMESPACE::ioctl(fd, FIONREAD, &n_after_reading);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GT(ret, -1);
+  ASSERT_EQ(n - READ_COUNT, n_after_reading);
+
+  // 0xDEADBEEF is just a random nonexistent command;
+  // calling this should always fail with ENOTTY
+  ret = LIBC_NAMESPACE::ioctl(fd, 0xDEADBEEF, NULL);
+  ASSERT_ERRNO_EQ(ENOTTY);
+  ASSERT_EQ(ret, -1);
+
+  ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+}