[libc] pipe(2) linux syscall wrapper and unittest

libc/config/linux/aarch64/entrypoints.txt

@@ -290,6 +290,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.link
     libc.src.unistd.linkat
     libc.src.unistd.lseek
+    libc.src.unistd.pipe2
     libc.src.unistd.pread
     libc.src.unistd.pwrite
     libc.src.unistd.read

libc/config/linux/x86_64/entrypoints.txt

@@ -297,6 +297,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.link
     libc.src.unistd.linkat
     libc.src.unistd.lseek
+    libc.src.unistd.pipe2
     libc.src.unistd.pread
     libc.src.unistd.pwrite
     libc.src.unistd.read

libc/include/llvm-libc-macros/linux/fcntl-macros.h

@@ -29,6 +29,12 @@
 #define O_NOFOLLOW 00400000
 #endif
 
+#ifdef __aarch64__
+#define O_DIRECT 0200000
+#else
+#define O_DIRECT 00040000
+#endif
+
 #define O_TRUNC 00001000
 #define O_TMPFILE (020000000 | O_DIRECTORY)
 

libc/include/llvm-libc-macros/linux/watch-queue-macros.h

@@ -0,0 +1,20 @@
+//===-- Definition of macros from watch-queue.h ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// References
+// https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/watch_queue.h
+// https://kernelnewbies.org/Linux_5.8#Core_.28various.29
+// https://docs.kernel.org/core-api/watch_queue.html
+
+#ifndef LLVM_LIBC_MACROS_LINUX_WATCH_QUEUE_MACROS_H
+#define LLVM_LIBC_MACROS_LINUX_WATCH_QUEUE_MACROS_H
+
+#define O_NOTIFICATION_PIPE                                                    \
+  O_EXCL /* Parameter to pipe2() selecting notification pipe */
+
+#endif // LLVM_LIBC_MACROS_LINUX_WATCH_QUEUE_MACROS_H

libc/spec/linux.td

@@ -264,6 +264,20 @@ def Linux : StandardSpec<"Linux"> {
       ]
   >;
 
+  HeaderSpec UniStd = HeaderSpec<
+    "unistd.h",
+    [], // Macros
+    [], // Types
+    [], // Enumerations
+    [
+        FunctionSpec<
+          "pipe2",
+          RetValSpec<IntType>,
+          [ArgSpec<IntPtr>, ArgSpec<IntType>]  // TODO: use int[2] array for the first ArgSpec when possible
+        >,
+    ]
+  >;
+
   let Headers = [
     Errno,
     SysEpoll,
@@ -272,5 +286,6 @@ def Linux : StandardSpec<"Linux"> {
     SysRandom,
     SysTime,
     Signal,
+    UniStd
   ];
 }

libc/src/unistd/CMakeLists.txt

@@ -149,6 +149,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.lseek
 )
 
+add_entrypoint_object(
+  pipe2
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pipe2
+)
+
 add_entrypoint_object(
   pread
   ALIAS

libc/src/unistd/linux/CMakeLists.txt

@@ -273,6 +273,19 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_entrypoint_object(
+  pipe2
+  SRCS
+    pipe2.cpp
+  HDRS
+    ../pipe2.h
+  DEPENDS
+    libc.include.unistd
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   pread
   SRCS

libc/src/unistd/linux/pipe2.cpp

@@ -0,0 +1,33 @@
+//===-- Linux implementation of pipe2 -------------------------------------===//
+//
+// 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/unistd/pipe2.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, pipe2, (int pipefd[2], int flags)) {
+  int ret;
+#ifdef SYS_pipe2
+  ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_pipe2, pipefd, flags);
+#else
+#error "pipe2 not available."
+#endif
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/unistd/pipe2.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for pipe2 -------------------------*- 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_UNISTD_PIPE2_H
+#define LLVM_LIBC_SRC_UNISTD_PIPE2_H
+
+namespace LIBC_NAMESPACE {
+
+int pipe2(int pipefd[2], int flags);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_UNISTD_PIPE2_H

libc/test/src/unistd/CMakeLists.txt

@@ -444,3 +444,20 @@ add_libc_test(
     libc.src.stdio.fopencookie
     libc.src.stdio.fflush
 )
+
+add_libc_unittest(
+  pipe2_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    pipe2_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.unistd
+    libc.src.errno.errno
+    libc.src.unistd.close
+    libc.src.unistd.pipe2
+    libc.src.unistd.read
+    libc.src.unistd.write
+    libc.test.UnitTest.ErrnoSetterMatcher
+)

libc/test/src/unistd/pipe2_test.cpp

@@ -0,0 +1,93 @@
+//===-- Unittests for pipe2 -----------------------------------------------===//
+//
+// 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 "include/llvm-libc-macros/linux/fcntl-macros.h"
+#include "include/llvm-libc-macros/linux/watch-queue-macros.h"
+#include "src/errno/libc_errno.h"
+#include "src/unistd/close.h"
+#include "src/unistd/pipe2.h"
+#include "src/unistd/read.h"
+#include "src/unistd/write.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+#include <fcntl.h>
+
+TEST(LlvmLibcPipe2Test, Pipe2CreationTest) {
+  int pipefd[2];
+  int flags;
+
+  LIBC_NAMESPACE::libc_errno = 0;
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+// Create pipe(2) with all valid flags set
+#ifdef CONFIG_WATCH_QUEUE
+  flags = O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE;
+#else
+  flags = O_CLOEXEC | O_NONBLOCK | O_DIRECT;
+#endif
+  ASSERT_NE(LIBC_NAMESPACE::pipe2(pipefd, flags), -1);
+  ASSERT_ERRNO_SUCCESS();
+
+  // Check if file descriptors are distinct and valid
+  ASSERT_GE(pipefd[0], 0);
+  ASSERT_GE(pipefd[1], 0);
+  ASSERT_NE(pipefd[0], pipefd[1]);
+
+  // Check file status flags associated with pipe file descriptors
+  ASSERT_TRUE((fcntl(pipefd[0], F_GETFL) & flags) != 0);
+  ASSERT_TRUE((fcntl(pipefd[1], F_GETFL) & flags) != 0);
+
+  // Close the pipe file descriptors
+  ASSERT_NE(LIBC_NAMESPACE::close(pipefd[0]), -1);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_NE(LIBC_NAMESPACE::close(pipefd[1]), -1);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcPipe2Test, ReadAndWriteViaPipe2) {
+  int pipefd[2];
+  int flags;
+
+  LIBC_NAMESPACE::libc_errno = 0;
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+  // Create pipe(2) with flags set to 0
+  flags = 0;
+  ASSERT_NE(LIBC_NAMESPACE::pipe2(pipefd, flags), -1);
+  ASSERT_ERRNO_SUCCESS();
+
+  // Write something via the pipe and read from other end
+  constexpr char MESSAGE[] = "Hello from the write end!";
+  constexpr size_t MESSAGE_SIZE = sizeof(MESSAGE);
+  char buf[MESSAGE_SIZE];
+  ASSERT_EQ(ssize_t(MESSAGE_SIZE),
+            LIBC_NAMESPACE::write(pipefd[1], MESSAGE, MESSAGE_SIZE));
+  ASSERT_EQ(ssize_t(MESSAGE_SIZE),
+            LIBC_NAMESPACE::read(pipefd[0], buf, MESSAGE_SIZE));
+  ASSERT_STREQ(buf, MESSAGE);
+
+  // Close the pipe file descriptors
+  ASSERT_NE(LIBC_NAMESPACE::close(pipefd[0]), -1);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_NE(LIBC_NAMESPACE::close(pipefd[1]), -1);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcPipe2Test, Pipe2InvalidFlags) {
+  int invalidflags = 0xDEADBEEF;
+  int pipefd[2];
+
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+  ASSERT_THAT(LIBC_NAMESPACE::pipe2(pipefd, invalidflags), Fails(EINVAL));
+}
+
+TEST(LlvmLibcPipe2Test, Pipe2InvalidPipeFD) {
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+  ASSERT_THAT(LIBC_NAMESPACE::pipe2(NULL, 0), Fails(EFAULT));
+}