io: Refactor close_range and closefrom

Now that Hurd implementis both close_range and closefrom (f2c996597d),
we can make close_range() a base ABI, and make the default closefrom()
implementation on top of close_range().

The generic closefrom() implementation based on __getdtablesize() is
moved to generic close_range().  On Linux it will be overriden by
the auto-generation syscall while on Hurd it will be a system specific
implementation.

The closefrom() now calls close_range() and __closefrom_fallback().
Since on Hurd close_range() does not fail, __closefrom_fallback() is an
empty static inline function set by__ASSUME_CLOSE_RANGE.

The __ASSUME_CLOSE_RANGE also allows optimize Linux
__closefrom_fallback() implementation when --enable-kernel=5.9 or
higher is used.

Finally the Linux specific tst-close_range.c is moved to io and
enabled as default.  The Linuxism and CLOSE_RANGE_UNSHARE are
guarded so it can be built for Hurd (I have not actually test it).

Checked on x86_64-linux-gnu, i686-linux-gnu, and with a i686-gnu
build.

include/unistd.h

@@ -3,6 +3,9 @@
 
 # ifndef _ISOMAC
 
+#  include <stdbool.h>
+#  include <kernel-features.h>
+
 libc_hidden_proto (_exit, __noreturn__)
 #  ifndef NO_RTLD_HIDDEN
 rtld_hidden_proto (_exit, __noreturn__)
@@ -158,7 +161,14 @@ extern int __brk (void *__addr) attribute_hidden;
 extern int __close (int __fd);
 libc_hidden_proto (__close)
 extern int __libc_close (int __fd);
+#  if __ASSUME_CLOSE_RANGE
+static inline _Bool __closefrom_fallback (int __lowfd, _Bool dirfd_fallback)
+{
+  return false;
+}
+#  else
 extern _Bool __closefrom_fallback (int __lowfd, _Bool) attribute_hidden;
+#  endif
 extern ssize_t __read (int __fd, void *__buf, size_t __nbytes);
 libc_hidden_proto (__read)
 extern ssize_t __write (int __fd, const void *__buf, size_t __n);

io/Makefile

@@ -57,7 +57,7 @@ routines :=								\
 	utimensat futimens file_change_detection			\
 	fts64-time64							\
 	ftw64-time64							\
-	closefrom
+	closefrom close_range
 
 others		:= pwd
 test-srcs	:= ftwtest ftwtest-time64
@@ -79,6 +79,7 @@ tests		:= test-utime test-stat test-stat2 test-lfs tst-getcwd \
 		   tst-futimens \
 		   tst-utimensat \
 		   tst-closefrom \
+		   tst-close_range \
 		   tst-ftw-bz28126
 
 tests-time64 := \

io/close_range.c

@@ -1,4 +1,4 @@
-/* Close a range of file descriptors.  Linux version.
+/* Close a range of file descriptors.
    Copyright (C) 2021 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -16,21 +16,29 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <stdbool.h>
+#include <errno.h>
-#include <stdio.h>
+#include <not-cancel.h>
-#include <sys/param.h>
 #include <unistd.h>
 
-void
+/* Close the file descriptors from FIRST up to LAST, inclusive.  */
-__closefrom (int lowfd)
+int
+__close_range (unsigned int first, unsigned int last,
+	       int flags)
 {
-  int l = MAX (0, lowfd);
+  if (first > last || flags != 0)
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
 
-  int r = __close_range (l, ~0U, 0);
+  int maxfd = __getdtablesize ();
-  if (r == 0)
+  if (maxfd == -1)
-    return;
+    return -1;
 
-  if (!__closefrom_fallback (l, true))
+  for (int i = first; i <= last && i < maxfd; i++)
-    __fortify_fail ("closefrom failed to close a file descriptor");
+    __close_nocancel_nostatus (i);
+
+  return 0;
 }
-weak_alias (__closefrom, closefrom)
+libc_hidden_def (__close_range)
+weak_alias (__close_range, close_range)

io/closefrom.c

@@ -16,19 +16,21 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <stdbool.h>
 #include <stdio.h>
+#include <sys/param.h>
 #include <unistd.h>
-#include <not-cancel.h>
 
 void
 __closefrom (int lowfd)
 {
-  int maxfd = __getdtablesize ();
+  int l = MAX (0, lowfd);
-  if (maxfd == -1)
-    __fortify_fail ("closefrom failed to get the file descriptor table size");
 
-  for (int i = 0; i < maxfd; i++)
+  int r = __close_range (l, ~0U, 0);
-    if (i >= lowfd)
+  if (r == 0)
-      __close_nocancel_nostatus (i);
+    return ;
+
+  if (!__closefrom_fallback (l, true))
+    __fortify_fail ("closefrom failed to close a file descriptor");
 }
 weak_alias (__closefrom, closefrom)

io/tst-close_range.c

@@ -119,6 +119,7 @@ close_range_test (void)
   support_descriptors_free (descrs);
 }
 
+#ifdef __linux__
 _Noreturn static int
 close_range_test_fn (void *arg)
 {
@@ -155,8 +156,10 @@ close_range_test_subprocess (void)
   support_descriptors_check (descrs);
   support_descriptors_free (descrs);
 }
+#endif
 
 
+#ifdef CLOSE_RANGE_UNSHARE
 _Noreturn static int
 close_range_unshare_test_fn (void *arg)
 {
@@ -200,6 +203,7 @@ close_range_unshare_test (void)
   support_descriptors_check (descrs1);
   support_descriptors_free (descrs1);
 }
+#endif
 
 static bool
 is_in_array (int *arr, size_t len, int fd)
@@ -282,8 +286,12 @@ do_test (void)
 {
   close_range_test_max_upper_limit ();
   close_range_test ();
+#ifdef __linux__
   close_range_test_subprocess ();
+#endif
+#ifdef CLOSE_RANGE_UNSHARE
   close_range_unshare_test ();
+#endif
   close_range_cloexec_test ();
 
   return 0;

posix/unistd.h

@@ -1199,6 +1199,16 @@ int getentropy (void *__buffer, size_t __length) __wur
     __attr_access ((__write_only__, 1, 2));
 #endif
 
+#ifdef __USE_GNU
+/* Close all file descriptors in the range FD up to MAX_FD.  The flag FLAGS
+   are define by the CLOSE_RANGE prefix.  This function behaves like close
+   on the range and gaps where the file descriptor is invalid or errors
+   encountered while closing file descriptors are ignored.   Returns 0 on
+   successor or -1 for failure (and sets errno accordingly).  */
+extern int close_range (unsigned int __fd, unsigned int __max_fd,
+			int __flags) __THROW;
+#endif
+
 /* Define some macros helping to catch buffer overflows.  */
 #if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function
 # include <bits/unistd.h>

sysdeps/mach/hurd/Makefile

@@ -196,7 +196,7 @@ sysdep_routines += cthreads
 endif
 
 ifeq (io, $(subdir))
-sysdep_routines += f_setlk close_nocancel close_nocancel_nostatus close_range \
+sysdep_routines += f_setlk close_nocancel close_nocancel_nostatus \
 		   fcntl_nocancel open_nocancel openat_nocancel read_nocancel \
 		   pread64_nocancel write_nocancel pwrite64_nocancel \
 		   wait4_nocancel \

sysdeps/mach/hurd/bits/unistd_ext.h

@@ -25,10 +25,4 @@
 /* Set the FD_CLOEXEC bit instead of closing the file descriptor.  */
 #define CLOSE_RANGE_CLOEXEC (1U << 2)
 
-/* Close the file descriptors from FIRST up to LAST, inclusive.
-   If CLOSE_RANGE_CLOEXEC is set in FLAGS, set the FD_CLOEXEC flag
-   instead of closing.  */
-extern int close_range (unsigned int __first, unsigned int __last,
-			int __flags) __THROW;
-
 #endif /* __USE_GNU  */

sysdeps/mach/hurd/closefrom.c

@@ -1,29 +0,0 @@
-/* Close a range of file descriptors.  Hurd version.
-   Copyright (C) 2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-#include <unistd.h>
-#include <sys/param.h>
-
-void
-__closefrom (int lowfd)
-{
-  int l = MAX (0, lowfd);
-
-  (void) __close_range (l, ~0U, 0);
-}
-weak_alias (__closefrom, closefrom)

sysdeps/mach/hurd/kernel-features.h

@@ -19,3 +19,5 @@
 /* This file can define __ASSUME_* macros checked by certain source files.
    Almost none of these are used outside of sysdeps/unix/sysv/linux code.
    But those referring to POSIX-level features like O_* flags can be.  */
+
+#define __ASSUME_CLOSE_RANGE 1

sysdeps/unix/sysv/linux/Makefile

@@ -120,7 +120,6 @@ tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
 	 tst-timerfd tst-ppoll \
 	 tst-clock_adjtime tst-adjtimex tst-ntp_adjtime tst-ntp_gettime \
 	 tst-ntp_gettimex tst-sigtimedwait tst-misalign-clone \
-  tst-close_range \
   tst-prctl \
   tst-scm_rights \
   # tests

sysdeps/unix/sysv/linux/bits/unistd_ext.h

@@ -47,13 +47,4 @@ extern __pid_t gettid (void) __THROW;
 # define CLOSE_RANGE_CLOEXEC (1U << 2)
 #endif
 
-/* Close all file descriptors in the range FD up to MAX_FD.  The flag FLAGS
-   are define by the CLOSE_RANGE prefix.  This function behaves like close
-   on the range, but in a fail-safe where it will either fail and not close
-   any file descriptor or close all of them.  Gaps where the file descriptor
-   is invalid are ignored.   Returns 0 on successor or -1 for failure (and
-   sets errno accordingly).  */
-extern int close_range (unsigned int __fd, unsigned int __max_fd,
-			int __flags) __THROW;
-
 #endif /* __USE_GNU  */

sysdeps/unix/sysv/linux/closefrom_fallback.c

@@ -21,6 +21,8 @@
 #include <not-cancel.h>
 #include <stdbool.h>
 
+#if !__ASSUME_CLOSE_RANGE
+
 /* Fallback code: iterates over /proc/self/fd, closing each file descriptor
    that fall on the criteria.  If DIRFD_FALLBACK is set, a failure on
    /proc/self/fd open will trigger a fallback that tries to close a file
@@ -97,3 +99,5 @@ err:
   __close_nocancel (dirfd);
   return ret;
 }
+
+#endif

sysdeps/unix/sysv/linux/kernel-features.h

@@ -220,6 +220,14 @@
 # define __ASSUME_FACCESSAT2 0
 #endif
 
+/* The close_range system call was introduced across all architectures
+   in Linux 5.9.  */
+#if __LINUX_KERNEL_VERSION >= 0x050900
+# define __ASSUME_CLOSE_RANGE 1
+#else
+# define __ASSUME_CLOSE_RANGE 0
+#endif
+
 /* The FUTEX_LOCK_PI2 operation was introduced across all architectures in Linux
    5.14.  */
 #if __LINUX_KERNEL_VERSION >= 0x050e00

sysdeps/unix/sysv/linux/syscalls.list

@@ -99,4 +99,4 @@ pkey_alloc	EXTRA	pkey_alloc	i:ii	pkey_alloc
 pkey_free	EXTRA	pkey_free	i:i	pkey_free
 gettid          EXTRA   gettid          Ei:     __gettid	gettid
 tgkill          EXTRA   tgkill          i:iii   __tgkill	tgkill
-close_range     EXTRA   close_range     i:iii   __close_range   close_range
+close_range     -       close_range     i:iii   __close_range   close_range