[libc] add ioctl

libc/config/linux/aarch64/entrypoints.txt

@@ -245,6 +245,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # https://github.com/llvm/llvm-project/issues/80060
     # libc.src.sys.epoll.epoll_pwait2
 
+    # sys/ioctl.h entrypoints
+    libc.src.sys.ioctl.ioctl
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
     libc.src.sys.mman.mincore

libc/config/linux/arm/entrypoints.txt

@@ -172,6 +172,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.free
     libc.src.stdlib.malloc
 
+    # sys/ioctl.h entrypoints
+    libc.src.sys.ioctl.ioctl
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap

libc/config/linux/riscv/entrypoints.txt

@@ -246,6 +246,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # https://github.com/llvm/llvm-project/issues/80060
     # libc.src.sys.epoll.epoll_pwait2
 
+    # sys/ioctl.h entrypoints
+    libc.src.sys.ioctl.ioctl
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
     libc.src.sys.mman.mincore

libc/config/linux/x86_64/entrypoints.txt

@@ -246,6 +246,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # https://github.com/llvm/llvm-project/issues/80060
     # libc.src.sys.epoll.epoll_pwait2
 
+    # sys/ioctl.h entrypoints
+    libc.src.sys.ioctl.ioctl
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
     libc.src.sys.mman.mincore

libc/src/sys/CMakeLists.txt

@@ -13,3 +13,4 @@ add_subdirectory(utsname)
 add_subdirectory(wait)
 add_subdirectory(prctl)
 add_subdirectory(uio)
+add_subdirectory(ioctl)

libc/src/sys/ioctl/CMakeLists.txt

@@ -0,0 +1,10 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+  ioctl
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.ioctl
+)

libc/src/sys/ioctl/ioctl.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for ioctl ---------------------------*-C++-*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_IOCTL_IOCTL_H
+#define LLVM_LIBC_SRC_SYS_IOCTL_IOCTL_H
+
+#include "src/__support/macros/config.h"
+#include <sys/ioctl.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+int ioctl(int fd, unsigned long request, ...);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_IOCTL_IOCTL_H

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

@@ -0,0 +1,12 @@
+add_entrypoint_object(
+  ioctl
+  SRCS
+    ioctl.cpp
+  HDRS
+    ../ioctl.h
+  DEPENDS
+    libc.include.sys_ioctl
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

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

@@ -0,0 +1,40 @@
+//===---------- Linux implementation of the ioctl function ----------------===//
+//
+// 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/sys/ioctl/ioctl.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <stdarg.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, ioctl, (int fd, unsigned long request, ...)) {
+  va_list vargs;
+  va_start(vargs, request);
+  void *data_pointer = va_arg(vargs, void *);
+  int ret =
+      LIBC_NAMESPACE::syscall_impl<int>(SYS_ioctl, fd, request, data_pointer);
+  va_end(vargs);
+
+  // From `man ioctl`:
+  // "Usually, on success zero is returned.  A few ioctl() operations
+  // use the return value as an output parameter and return a
+  // nonnegative value on success.  On error, -1 is returned, and errno
+  // is set to indicate the error."
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

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 +1,14 @@
+add_custom_target(libc_sys_ioctl_unittests)
+
+add_libc_unittest(
+  ioctl_test
+  SUITE
+    libc_sys_ioctl_unittests
+  SRCS
+    ioctl_test.cpp
+  DEPENDS
+    libc.include.sys_ioctl
+    libc.include.sys_filio
+    libc.src.sys.ioctl.ioctl
+    libc.src.errno.errno
+)

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

@@ -0,0 +1,34 @@
+//===-- 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/sys/ioctl/ioctl.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include <sys/filio.h>
+#include <sys/ioctl.h>
+
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+TEST(LlvmLibcSysIoctlTest, StdinFIONREAD) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  // FIONREAD reports the number of readable bytes for fd
+  int bytes;
+  int ret = LIBC_NAMESPACE::ioctl(0, FIONREAD, &bytes);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcSysIoctlTest, InvalidCommandENOTTY) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  // 0xDEADBEEF is just a random nonexistent command;
+  // calling this should always fail with ENOTTY
+  int ret = LIBC_NAMESPACE::ioctl(3, 0xDEADBEEF, NULL);
+  ASSERT_TRUE(ret == -1 && errno == ENOTTY);
+}