Add renameat2 function [BZ #17662]

The implementation falls back to renameat if renameat2 is not available
in the kernel (or in the kernel headers) and the flags argument is zero.
Without kernel support, a non-zero argument returns EINVAL, not ENOSYS.
This mirrors what the kernel does for invalid renameat2 flags.

45 files changed, 400 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 2e8308e191..27927257ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,34 @@
+2018-07-05  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ # 17662]
+	* libio/stdio.h [__USE_GNU] (RENAME_NOREPLACE, RENAME_EXCHANGE)
+	(RENAME_WHITEOUT): Define.
+	[__USE_GNU] (renameat2): Declare.
+	* stdio-common/Makefile (routines): Add renameat2.
+	(tests): Add tst-renameat2.
+	* stdio-common/Versions (GLIBC_2_28): Export renameat2.
+	* stdio-common/renameat2.c: New file.
+	* stdio-common/tst-renameat2.c: Likewise.
+	* sysdeps/unix/sysv/linux/renameat2.c: Likewise.
+	* manual/filesys.texi (Temporary Files): Note that renameat2 is
+	undocumented.
+	* sysdeps/unix/sysv/linux/kernel-features.h
+	[__LINUX_KERNEL_VERSION >= 0x030F00] (__ASSUME_RENAMEAT2): Define.
+	* sysdeps/unix/sysv/linux/alpha/kernel-features.h
+	[__LINUX_KERNEL_VERSION < 0x031100] (__ASSUME_RENAMEAT2): Undefine.
+	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+	[__LINUX_KERNEL_VERSION < 0x031100] (__ASSUME_RENAMEAT2): Undefine.
+	* sysdeps/unix/sysv/linux/sh/kernel-features.h
+	[__LINUX_KERNEL_VERSION < 0x040800] (__ASSUME_RENAMEAT2): Undefine.
+	* sysdeps/unix/sysv/linux/sparc/kernel-features.h
+	[__LINUX_KERNEL_VERSION < 0x031000] (__ASSUME_RENAMEAT2): Undefine.
+	* include/stdio.h (__renameat): Add alias for renameat.
+	* stdio-common/renameat.c (__renameat): Rename from renameat.
+	Add hidden definition and alias.
+	* sysdeps/unix/sysv/linux/renameat.c: Likewise.
+	* sysdeps/mach/hurd/renameat.c: Likewise.
+	* sysdeps/**/libc*.abilist: Add renameat2.
+
 2018-07-04  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	* posix/bug-regex33.c: Fix build after regex sync.
diff --git a/NEWS b/NEWS
index b1ce067d27..5d253910b5 100644
--- a/NEWS
+++ b/NEWS
@@ -39,6 +39,15 @@ Major new features:
 * Building and running on GNU/Hurd systems now works without out-of-tree
   patches.
 
+* The renameat2 function has been added, a variant of the renameat function
+  which has a flags argument.  If the flags are zero, the renameat2 function
+  acts like renameat.  If the flag is not zero and there is no kernel
+  support for renameat2, the function will fail with an errno value of
+  EINVAL.  This is different from the existing gnulib function renameatu,
+  which performs a plain rename operation in case of a RENAME_NOREPLACE
+  flags and a non-existing destination (and therefore has a race condition
+  that can clobber the destination inadvertently).
+
 * IDN domain names in getaddrinfo and getnameinfo now use the system libidn2
   library if installed.  libidn2 version 2.0.5 or later is recommended.  If
   libidn2 is not available, internationalized domain names are not encoded
diff --git a/include/stdio.h b/include/stdio.h
index f140813ad6..3ba0edc924 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -237,5 +237,8 @@ __putc_unlocked (int __c, FILE *__stream)
 }
 #  endif
 
+extern __typeof (renameat) __renameat;
+libc_hidden_proto (__renameat)
+
 # endif /* not _ISOMAC */
 #endif /* stdio.h */
diff --git a/libio/stdio.h b/libio/stdio.h
index 731f8e56f4..739e08610d 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -153,6 +153,18 @@ extern int renameat (int __oldfd, const char *__old, int __newfd,
 		     const char *__new) __THROW;
 #endif
 
+#ifdef __USE_GNU
+/* Flags for renameat2.  */
+# define RENAME_NOREPLACE (1 << 0)
+# define RENAME_EXCHANGE (1 << 1)
+# define RENAME_WHITEOUT (1 << 2)
+
+/* Rename file OLD relative to OLDFD to NEW relative to NEWFD, with
+   additional flags.  */
+extern int renameat2 (int __oldfd, const char *__old, int __newfd,
+		      const char *__new, unsigned int __flags) __THROW;
+#endif
+
 /* Create a temporary file and open it read/write.
 
    This function is a possible cancellation point and therefore not
diff --git a/manual/filesys.texi b/manual/filesys.texi
index cc70a6b7ee..db2f1041de 100644
--- a/manual/filesys.texi
+++ b/manual/filesys.texi
@@ -3552,6 +3552,7 @@ The @code{mkdtemp} function comes from OpenBSD.
 @c open_by_handle_at
 @c readlinkat
 @c renameat
+@c renameat2
 @c scandirat
 @c symlinkat
 @c unlinkat
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 96bd7c303a..a10f12ab3c 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -35,7 +35,7 @@ routines	:=							      \
 	perror psignal							      \
 	tmpfile tmpfile64 tmpnam tmpnam_r tempnam tempname		      \
 	getline getw putw						      \
-	remove rename renameat						      \
+	remove rename renameat renameat2				      \
 	flockfile ftrylockfile funlockfile				      \
 	isoc99_scanf isoc99_vscanf isoc99_fscanf isoc99_vfscanf isoc99_sscanf \
 	isoc99_vsscanf							      \
@@ -62,6 +62,7 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
 	 tst-vfprintf-user-type \
 	 tst-vfprintf-mbs-prec \
 	 tst-scanf-round \
+	 tst-renameat2 \
 
 test-srcs = tst-unbputc tst-printf tst-printfsz-islongdouble
 
diff --git a/stdio-common/Versions b/stdio-common/Versions
index 5016f69c20..b8217578c8 100644
--- a/stdio-common/Versions
+++ b/stdio-common/Versions
@@ -57,6 +57,9 @@ libc {
     psiginfo;
     register_printf_modifier; register_printf_type; register_printf_specifier;
   }
+  GLIBC_2.28 {
+    renameat2;
+  }
   GLIBC_PRIVATE {
     # global variables
     _itoa_lower_digits;
diff --git a/stdio-common/renameat.c b/stdio-common/renameat.c
index 2180b87bdf..98c8f1d18b 100644
--- a/stdio-common/renameat.c
+++ b/stdio-common/renameat.c
@@ -22,7 +22,7 @@
 
 /* Rename the file OLD relative to OLDFD to NEW relative to NEWFD.  */
 int
-renameat (int oldfd, const char *old, int newfd, const char *new)
+__renameat (int oldfd, const char *old, int newfd, const char *new)
 {
   if ((oldfd < 0 && oldfd != AT_FDCWD) || (newfd < 0 && newfd != AT_FDCWD))
     {
@@ -40,5 +40,6 @@ renameat (int oldfd, const char *old, int newfd, const char *new)
   return -1;
 }
 
-
+libc_hidden_def (__renameat)
+weak_alias (__renameat, renameat)
 stub_warning (renameat)
diff --git a/stdio-common/renameat2.c b/stdio-common/renameat2.c
new file mode 100644
index 0000000000..c2cedcd2cb
--- /dev/null
+++ b/stdio-common/renameat2.c
@@ -0,0 +1,30 @@
+/* Generic implementation of the renameat function.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <stdio.h>
+
+int
+renameat2 (int oldfd, const char *old, int newfd, const char *new,
+           unsigned int flags)
+{
+  if (flags == 0)
+    return __renameat (oldfd, old, newfd, new);
+  __set_errno (EINVAL);
+  return -1;
+}
diff --git a/stdio-common/tst-renameat2.c b/stdio-common/tst-renameat2.c
new file mode 100644
index 0000000000..958b0918d6
--- /dev/null
+++ b/stdio-common/tst-renameat2.c
@@ -0,0 +1,204 @@
+/* Linux implementation for renameat2 function.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <array_length.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+/* Directory with the temporary files.  */
+static char *directory;
+static int directory_fd;
+
+/* Paths within that directory.  */
+static char *old_path;          /* File is called "old".  */
+static char *new_path;          /* File is called "new".  */
+
+/* Subdirectory within the directory above.  */
+static char *subdirectory;
+int subdirectory_fd;
+
+/* And a pathname in that directory (called "file").  */
+static char *subdir_path;
+
+static void
+prepare (int argc, char **argv)
+{
+  directory = support_create_temp_directory ("tst-renameat2-");
+  directory_fd = xopen (directory, O_RDONLY | O_DIRECTORY, 0);
+  old_path = xasprintf ("%s/old", directory);
+  add_temp_file (old_path);
+  new_path = xasprintf ("%s/new", directory);
+  add_temp_file (new_path);
+  subdirectory = xasprintf ("%s/subdir", directory);
+  xmkdir (subdirectory, 0777);
+  add_temp_file (subdirectory);
+  subdirectory_fd = xopen (subdirectory, O_RDONLY | O_DIRECTORY, 0);
+  subdir_path = xasprintf ("%s/file", subdirectory);
+  add_temp_file (subdir_path);
+}
+
+/* Delete all files, preparing a clean slate for the next test.  */
+static void
+delete_all_files (void)
+{
+  char *files[] = { old_path, new_path, subdir_path };
+  for (size_t i = 0; i < array_length (files); ++i)
+    if (unlink (files[i]) != 0 && errno != ENOENT)
+      FAIL_EXIT1 ("unlink (\"%s\"): %m", files[i]);
+}
+
+/* Return true if PATH exists in the file system.  */
+static bool
+file_exists (const char *path)
+{
+  return access (path, F_OK) == 0;
+}
+
+/* Check that PATH exists and has size EXPECTED_SIZE.  */
+static void
+check_size (const char *path, off64_t expected_size)
+{
+  struct stat64 st;
+  xstat (path, &st);
+  if (st.st_size != expected_size)
+    FAIL_EXIT1 ("file \"%s\": expected size %lld, actual size %lld",
+                path, (unsigned long long int) expected_size,
+                (unsigned long long int) st.st_size);
+}
+
+/* Rename tests where the target does not exist.  */
+static void
+rename_without_existing_target (unsigned int flags)
+{
+  delete_all_files ();
+  support_write_file_string (old_path, "");
+  TEST_COMPARE (renameat2 (AT_FDCWD, old_path, AT_FDCWD, new_path, flags), 0);
+  TEST_VERIFY (!file_exists (old_path));
+  TEST_VERIFY (file_exists (new_path));
+
+  delete_all_files ();
+  support_write_file_string (old_path, "");
+  TEST_COMPARE (renameat2 (directory_fd, "old", AT_FDCWD, new_path, flags), 0);
+  TEST_VERIFY (!file_exists (old_path));
+  TEST_VERIFY (file_exists (new_path));
+
+  delete_all_files ();
+  support_write_file_string (old_path, "");
+  TEST_COMPARE (renameat2 (directory_fd, "old", subdirectory_fd, "file", 0),
+                0);
+  TEST_VERIFY (!file_exists (old_path));
+  TEST_VERIFY (file_exists (subdir_path));
+}
+
+static int
+do_test (void)
+{
+  /* Tests with zero flags argument.  These are expected to