[libc] Add implementations of the POSIX creat and openat functions.

[michaelrj]

LGTM

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

52

Nit: the

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.toascii
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
     # errno.h entrypoints
     libc.src.errno.__errno_location
 
     # fcntl.h entrypoints
+    libc.src.fcntl.creat
     libc.src.fcntl.open
+    libc.src.fcntl.openat
 
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy

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

 #define S_IXGRP 010
 #define S_IRWXO 07
 #define S_IROTH 04
 #define S_IWOTH 02
 #define S_IXOTH 01
 #define S_ISUID 04000
 #define S_ISGID 02000
 
+// Special directory FD to indicate that the path argument to
+// openat is relative to the current directory.
+#define AT_FDCWD -100
+
 #endif // __LLVM_LIBC_MACROS_LINUX_FCNTL_MACROS_H

libc/spec/posix.td

def POSIX : StandardSpec<"POSIX"> {
 
   HeaderSpec FCntl = HeaderSpec<
     "fcntl.h",
     [], // Macros
     [ModeTType],
     [], // Enumerations
     [
       FunctionSpec<
+          "creat",
+          RetValSpec<IntType>,
+          [ArgSpec<ConstCharPtr>, ArgSpec<ModeTType>]
+      >,
+      FunctionSpec<
           "open",
           RetValSpec<IntType>,
           [ArgSpec<ConstCharPtr>, ArgSpec<IntType>, ArgSpec<VarArgType>]
       >,
+      FunctionSpec<
+          "openat",
+          RetValSpec<IntType>,
+          [ArgSpec<IntType>, ArgSpec<ConstCharPtr>, ArgSpec<IntType>, ArgSpec<VarArgType>]
+      >,
     ]
   >;
 
   HeaderSpec SysMMan = HeaderSpec<
       "sys/mman.h",
       [
         // TODO: Add a facility to bunch macros into bitwise-or-able groups.
         // POSIX requires it, so such thing should be captured in this spec.

libc/src/fcntl/CMakeLists.txt

 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
 endif()
 
 add_entrypoint_object(
+  creat
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.creat
+)
+
+add_entrypoint_object(
   open
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.open
 )
+
+add_entrypoint_object(
+  openat
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.openat
+)

libc/src/fcntl/creat.h

+//===-- Implementation header of creat --------------------------*- 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_FCNTL_CREAT_H
+#define LLVM_LIBC_SRC_FCNTL_CREAT_H
+
+#include <fcntl.h>
+
+namespace __llvm_libc {
+
+int creat(const char *path, int mode);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_FCNTL_CREAT_H

libc/src/fcntl/linux/CMakeLists.txt

 add_entrypoint_object(
+  creat
+  SRCS
+    creat.cpp
+  HDRS
+    ../creat.h
+  DEPENDS
+    libc.include.errno
+    libc.include.fcntl
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.__errno_location
+)
+
+add_entrypoint_object(
   open
   SRCS
     open.cpp
   HDRS
     ../open.h
   DEPENDS
     libc.include.errno
     libc.include.fcntl
     libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )
+
+add_entrypoint_object(
+  openat
+  SRCS
+    openat.cpp
+  HDRS
+    ../openat.h
+  DEPENDS
+    libc.include.errno
+    libc.include.fcntl
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.__errno_location
+)

libc/src/fcntl/linux/creat.cpp

+//===-- Implementation of creat -------------------------------------------===//
+//
+// 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/fcntl/creat.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, creat, (const char *path, int mode_flags)) {
+  int fd = __llvm_libc::syscall(SYS_open, path, O_CREAT | O_WRONLY | O_TRUNC,
+                                mode_flags);
+  if (fd > 0)
+    return fd;
+
+  errno = -fd;
+  return -1;
+}
+
+} // namespace __llvm_libc

libc/src/fcntl/linux/openat.cpp

+//===-- Implementation of openat ------------------------------------------===//
+//
+// 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/fcntl/openat.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, openat, (int dfd, const char *path, int flags, ...)) {
+  mode_t mode_flags = 0;
+  // O_TMPFILE is a multi-bit flag so we test all bits by checking for equality
+  // with O_TMPFILE
+  if ((flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE) {
+    va_list varargs;
+    va_start(varargs, flags);
+    mode_flags = va_arg(varargs, mode_t);
+    va_end(varargs);
+  }
+
+  int fd = __llvm_libc::syscall(SYS_openat, dfd, path, flags, mode_flags);
+  if (fd > 0)
+    return fd;
+
+  errno = -fd;
+  return -1;
+}
+
+} // namespace __llvm_libc

libc/src/fcntl/openat.h

+//===-- Implementation header of openat -------------------------*- 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_FCNTL_OPENAT_H
+#define LLVM_LIBC_SRC_FCNTL_OPENAT_H
+
+#include <fcntl.h>
+
+namespace __llvm_libc {
+
+int openat(int dfd, const char *path, int flags, ...);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_FCNTL_OPENAT_H

libc/test/src/CMakeLists.txt

 add_subdirectory(errno)
 add_subdirectory(fenv)
 add_subdirectory(inttypes)
 add_subdirectory(math)
 add_subdirectory(string)
 add_subdirectory(stdlib)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
+  add_subdirectory(fcntl)
   add_subdirectory(sys)
   add_subdirectory(unistd)
 endif()
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 

libc/test/src/fcntl/CMakeLists.txt

+add_libc_testsuite(libc_fcntl_unittests)
+
+add_subdirectory(testdata)
+
+add_libc_unittest(
+  creat_test
+  SUITE
+    libc_fcntl_unittests
+  SRCS
+    creat_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.fcntl
+    libc.src.fcntl.creat
+    libc.src.fcntl.open
+    libc.src.unistd.close
+    libc.test.errno_setter_matcher
+)
+
+add_libc_unittest(
+  openat_test
+  SUITE
+    libc_fcntl_unittests
+  SRCS
+    openat_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.fcntl
+    libc.src.fcntl.open
+    libc.src.fcntl.openat
+    libc.src.unistd.close
+    libc.src.unistd.read
+    libc.test.errno_setter_matcher
+)

libc/test/src/fcntl/creat_test.cpp

+//===-- Unittest for creat ------------------------------------------------===//
+//
+// 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/fcntl/creat.h"
+#include "src/fcntl/open.h"
+#include "src/unistd/close.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include "utils/testutils/FDReader.h"
+
+#include <errno.h>
+
+TEST(LlvmLibcCreatTest, CreatAndOpen) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_FILE = "testdata/creat.test";
+  int fd = __llvm_libc::creat(TEST_FILE, S_IRWXU);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
+
+  fd = __llvm_libc::open(TEST_FILE, O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
+
+  // TODO: 'remove' the test file at the end.
+}

libc/test/src/fcntl/openat_test.cpp

+//===-- Unittests for openat ----------------------------------------------===//
+//
+// 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/fcntl/open.h"
+#include "src/fcntl/openat.h"
+#include "src/unistd/close.h"
+#include "src/unistd/read.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include "utils/testutils/FDReader.h"
+
+#include <errno.h>
+
+TEST(LlvmLibcUniStd, OpenAndReadTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_DIR = "testdata";
+  constexpr const char *TEST_FILE = "openat.test";
+  int dir_fd = __llvm_libc::open(TEST_DIR, O_DIRECTORY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(dir_fd, 0);
+  constexpr const char TEST_MSG[] = "openat test";
+  constexpr int TEST_MSG_SIZE = sizeof(TEST_MSG) - 1;
+
+  int read_fd = __llvm_libc::openat(dir_fd, TEST_FILE, O_RDONLY);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(read_fd, 0);
+  char read_buf[TEST_MSG_SIZE];
+  ASSERT_THAT(__llvm_libc::read(read_fd, read_buf, TEST_MSG_SIZE),
+              Succeeds(TEST_MSG_SIZE));
+  ASSERT_THAT(__llvm_libc::close(read_fd), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::close(dir_fd), Succeeds(0));
+}
+
+TEST(LlvmLibcUniStd, FailTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  EXPECT_THAT(__llvm_libc::openat(AT_FDCWD, "openat.test", O_RDONLY),
+              Fails(ENOENT));
+}

libc/test/src/fcntl/testdata/CMakeLists.txt

+file(GENERATE OUTPUT openat.test CONTENT "openat test")