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[PATCH] Linux: Add memfd_create system call wrapper
- From: fweimer at redhat dot com (Florian Weimer)
- To: libc-alpha at sourceware dot org
- Date: Sat, 04 Nov 2017 00:24:45 +0100
- Subject: [PATCH] Linux: Add memfd_create system call wrapper
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The system call is somewhat obscure because it is closely related
to file descriptor sealing. However, it is also the recommended
way to create alias mappings, which is why it has more general use.
No emulation is provided. Except for the name of the
/proc/self/fd links, it would be possible to implement an
approximation using O_TMPFILE and tmpfs, but this does not appear
to be worth the added complexity.
2017-11-03 Florian Weimer <fweimer@redhat.com>
Linux: Add memfd_create system call wrapper
* sysdeps/unix/sysv/linux/Makefile [misc] (sysdep_headers): Add
sys/memfd.h.
(tests): Add tst-memfd_create.
* sysdeps/unix/sysv/linux/Versions (GLIBC_2.27): Add memfd_create.
* sysdeps/unix/sysv/linux/syscalls.list (memfd_create): Add.
* sysdeps/unix/sysv/linux/sys/memfd.h: New file.
* sysdeps/unix/sysv/linux/**.abilist: Update.
* manual/llio.texi (Memory-mapped I/O): Document memfd_create.
* support/Makefile (libsupport-routines): Add xreadlink, xstrndup,
xunlink.
(tests): Add tst-xreadlink.
* support/support.h (xstrndup): Declare.
* support/xunistd.h (xunlink, xreadlink): Declare.
* support/temp_file.h (support_create_temp_directory): Declare.
* support/temp_file.c (support_create_temp_directory): New function.
* support/support_chroot.c (support_chroot_create): Use it.
* support/xreadlink.c: New file.
* support/xstrndup.c: Likewise.
* support/xunlink.c: Likewise.
* support/tst-xreadlink.c: Likewise.
diff --git a/manual/llio.texi b/manual/llio.texi
index e72c53c785..5ab68e1511 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -1775,6 +1775,40 @@ the given @var{name} previously created by @code{shm_open}.
On failure @code{errno} is set.
@end deftypefn
+@deftypefn Function int memfd_create (const char *@var{name}, unsigned int flags)
+@standards{Linux, sys/memfd.h}
+
+The @code{memfd_create} function returns a file descriptor which can be
+used to create memory mappings using the @code{mmap} function. It is
+similar to the @code{shm_open} function in the sense that these mappings
+are not backed by actual files. However, the descriptor return by
+@code{memfd_create} does not correspond to a named object; the
+@var{name} argument is used for informative purposes only. The
+descriptor can be passed between processes (for example, over local
+domain sockets), and mappings at the same offset refer to the same
+memory, or the descriptor can be used to create alias mappings within
+the same process.
+
+The descriptor initially refers to a zero-length file. Before mappings
+can be created which are backed by memory, the file size needs to be
+increased with the @code{ftruncate} function. @xref{File Size}.
+
+The @var{flags} argument can be a combination of the following flags:
+
+@table @code
+@item MFD_CLOEXEC
+The descriptor is created with the @code{O_CLOEXEC} flag.
+
+@item MFD_ALLOW_SEALING
+The descriptor supports the addition of seals using the @code{fcntl}
+function.
+@end table
+
+The @code{memfd_create} function is specific to Linux.
+
+@end deftypefn
+
+
@node Waiting for I/O
@section Waiting for Input or Output
@cindex waiting for input or output
diff --git a/support/Makefile b/support/Makefile
index 027a663000..dafb1737a4 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -109,19 +109,22 @@ libsupport-routines = \
xpthread_once \
xpthread_rwlock_init \
xpthread_rwlock_rdlock \
- xpthread_rwlock_wrlock \
xpthread_rwlock_unlock \
+ xpthread_rwlock_wrlock \
xpthread_rwlockattr_init \
xpthread_rwlockattr_setkind_np \
xpthread_sigmask \
xpthread_spin_lock \
xpthread_spin_unlock \
+ xreadlink \
xrealloc \
xrecvfrom \
xsendto \
xsetsockopt \
xsocket \
xstrdup \
+ xstrndup \
+ xunlink \
xwaitpid \
xwrite \
@@ -138,6 +141,7 @@ tests = \
tst-support_capture_subprocess \
tst-support_format_dns_packet \
tst-support_record_failure \
+ tst-xreadlink \
ifeq ($(run-built-tests),yes)
tests-special = \
diff --git a/support/support.h b/support/support.h
index 4b5f04c2cc..bbba803ba1 100644
--- a/support/support.h
+++ b/support/support.h
@@ -68,6 +68,7 @@ void *xrealloc (void *p, size_t n);
char *xasprintf (const char *format, ...)
__attribute__ ((format (printf, 1, 2), malloc));
char *xstrdup (const char *);
+char *xstrndup (const char *, size_t);
__END_DECLS
diff --git a/support/support_chroot.c b/support/support_chroot.c
index f3ef551b05..f6fad18f33 100644
--- a/support/support_chroot.c
+++ b/support/support_chroot.c
@@ -46,10 +46,11 @@ support_chroot_create (struct support_chroot_configuration conf)
{
struct support_chroot *chroot = xmalloc (sizeof (*chroot));
- chroot->path_chroot = xasprintf ("%s/tst-resolv-res_init-XXXXXX", test_dir);
- if (mkdtemp (chroot->path_chroot) == NULL)
- FAIL_EXIT1 ("mkdtemp (\"%s\"): %m", chroot->path_chroot);
- add_temp_file (chroot->path_chroot);
+ {
+ char *template = xasprintf ("%s/tst-resolv-res_init-XXXXXX", test_dir);
+ chroot->path_chroot = support_create_temp_directory (template);
+ free (template);
+ }
/* Create the /etc directory in the chroot environment. */
char *path_etc = xasprintf ("%s/etc", chroot->path_chroot);
diff --git a/support/temp_file.c b/support/temp_file.c
index fdb2477ab9..cbd54e2e17 100644
--- a/support/temp_file.c
+++ b/support/temp_file.c
@@ -86,6 +86,19 @@ create_temp_file (const char *base, char **filename)
return fd;
}
+char *
+support_create_temp_directory (const char *base)
+{
+ char *base_copy = xstrdup (base);
+ if (mkdtemp (base_copy) == NULL)
+ {
+ printf ("error: mkdtemp (\"%s\"): %m", base);
+ exit (1);
+ }
+ add_temp_file (base_copy);
+ return base_copy;
+}
+
/* Helper functions called by the test skeleton follow. */
void
diff --git a/support/temp_file.h b/support/temp_file.h
index 6fed8df1ea..dfefe585de 100644
--- a/support/temp_file.h
+++ b/support/temp_file.h
@@ -32,6 +32,11 @@ void add_temp_file (const char *name);
*FILENAME. */
int create_temp_file (const char *base, char **filename);
+/* Create a temporary directory and schedule it for deletion. BASE
+ must end with the six characters "XXXXXX". Return the name of the
+ temporary directory. The caller should free the string. */
+char *support_create_temp_directory (const char *base);
+
__END_DECLS
#endif /* SUPPORT_TEMP_FILE_H */
diff --git a/support/tst-xreadlink.c b/support/tst-xreadlink.c
new file mode 100644
index 0000000000..cb2c12a888
--- /dev/null
+++ b/support/tst-xreadlink.c
@@ -0,0 +1,72 @@
+/* Test the xreadlink function.
+ Copyright (C) 2017 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 <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+
+static int
+do_test (void)
+{
+ char *dir = support_create_temp_directory ("/tmp/tst-xreadlink-XXXXXX");
+ char *symlink_name = xasprintf ("%s/symlink", dir);
+ add_temp_file (symlink_name);
+
+ /* The limit 10000 is arbitrary and simply there to prevent an
+ attempt to exhaust all available disk space. */
+ for (int size = 1; size < 10000; ++size)
+ {
+ char *contents = xmalloc (size + 1);
+ for (int i = 0; i < size; ++i)
+ contents[i] = 'a' + (rand () % 26);
+ contents[size] = '\0';
+ if (symlink (contents, symlink_name) != 0)
+ {
+ if (errno == ENAMETOOLONG)
+ {
+ printf ("info: ENAMETOOLONG failure at %d bytes\n", size);
+ free (contents);
+ break;
+ }
+ FAIL_EXIT1 ("symlink (%d bytes): %m", size);
+ }
+
+ char *readlink_result = xreadlink (symlink_name);
+ TEST_VERIFY (strcmp (readlink_result, contents) == 0);
+ free (readlink_result);
+ xunlink (symlink_name);
+ free (contents);
+ }
+
+ /* Create an empty file to suppress the temporary file deletion
+ warning. */
+ xclose (xopen (symlink_name, O_WRONLY | O_CREAT, 0));
+
+ free (symlink_name);
+ free (dir);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/xreadlink.c b/support/xreadlink.c
new file mode 100644
index 0000000000..aec58a2aa6
--- /dev/null
+++ b/support/xreadlink.c
@@ -0,0 +1,44 @@
+/* Error-checking, allocating wrapper for readlink.
+ Copyright (C) 2017 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 <scratch_buffer.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <xunistd.h>
+
+char *
+xreadlink (const char *path)
+{
+ struct scratch_buffer buf;
+ scratch_buffer_init (&buf);
+
+ while (true)
+ {
+ ssize_t count = readlink (path, buf.data, buf.length);
+ if (count < 0)
+ FAIL_EXIT1 ("readlink (\"%s\"): %m", path);
+ if (count < buf.length)
+ {
+ char *result = xstrndup (buf.data, count);
+ scratch_buffer_free (&buf);
+ return result;
+ }
+ if (!scratch_buffer_grow (&buf))
+ FAIL_EXIT1 ("scratch_buffer_grow in xreadlink");
+ }
+}
diff --git a/support/xstrndup.c b/support/xstrndup.c
new file mode 100644
index 0000000000..d59a283d25
--- /dev/null
+++ b/support/xstrndup.c
@@ -0,0 +1,30 @@
+/* strndup with error checking.
+ Copyright (C) 2016-2017 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 <support/support.h>
+
+#include <string.h>
+
+char *
+xstrndup (const char *s, size_t length)
+{
+ char *p = strndup (s, length);
+ if (p == NULL)
+ oom_error ("strndup", length);
+ return p;
+}
diff --git a/support/xunistd.h b/support/xunistd.h
index c947bfd8fb..05c2626a7b 100644
--- a/support/xunistd.h
+++ b/support/xunistd.h
@@ -38,6 +38,11 @@ int xopen (const char *path, int flags, mode_t);
void xstat (const char *path, struct stat64 *);
void xmkdir (const char *path, mode_t);
void xchroot (const char *path);
+void xunlink (const char *path);
+
+/* Read the link at PATH. The caller should free the returned string
+ with free. */
+char *xreadlink (const char *path);
/* Close the file descriptor. Ignore EINTR errors, but terminate the
process on other errors. */
diff --git a/support/xunlink.c b/support/xunlink.c
new file mode 100644
index 0000000000..f94ee118cf
--- /dev/null
+++ b/support/xunlink.c
@@ -0,0 +1,27 @@
+/* Error-checking wrapper for unlink.
+ Copyright (C) 2017 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 <support/check.h>
+#include <support/xunistd.h>
+
+void
+xunlink (const char *path)
+{
+ if (unlink (path) != 0)
+ FAIL_EXIT1 ("unlink (\"%s\"): %m", path);
+}
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 0c8a009b5e..3a5515d092 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -39,7 +39,7 @@ sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
sys/klog.h \
sys/user.h sys/prctl.h \
sys/kd.h sys/soundcard.h sys/vt.h \
- sys/quota.h sys/fsuid.h \
+ sys/quota.h sys/fsuid.h sys/memfd.h \
scsi/sg.h scsi/scsi.h scsi/scsi_ioctl.h sys/pci.h \
sys/raw.h sys/personality.h sys/epoll.h \
bits/a.out.h sys/inotify.h sys/signalfd.h sys/eventfd.h \
@@ -50,7 +50,8 @@ sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
bits/siginfo-arch.h bits/siginfo-consts-arch.h
tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
- tst-quota tst-sync_file_range test-errno-linux tst-sysconf-iov_max
+ tst-quota tst-sync_file_range test-errno-linux tst-sysconf-iov_max \
+ tst-memfd_create
# Generate the list of SYS_* macros for the system calls (__NR_*
# macros). The file syscall-names.list contains all possible system
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 6c9e06f4f9..992c19729f 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -166,6 +166,9 @@ libc {
GLIBC_2.15 {
process_vm_readv; process_vm_writev;
}
+ GLIBC_2.27 {
+ memfd_create;
+ }
GLIBC_PRIVATE {
# functions used in other libraries
__syscall_rt_sigqueueinfo;
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index ed598aedac..140ca28abc 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2106,6 +2106,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index 4e57f36bcf..f698e1b2f4 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2017,6 +2017,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/arm/libc.abilist b/sysdeps/unix/sysv/linux/arm/libc.abilist
index 5b70e1bfc9..8a8af3e3e4 100644
--- a/sysdeps/unix/sysv/linux/arm/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/libc.abilist
@@ -107,6 +107,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.4 GLIBC_2.4 A
GLIBC_2.4 _Exit F
GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 6a2500a8b3..5b81a6cd7d 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -1871,6 +1871,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 9ab4e3642a..51ead9e867 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2036,6 +2036,7 @@ GLIBC_2.26 wcstof128_l F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index 81bb623fe8..78b4ee8d40 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -1900,6 +1900,7 @@ GLIBC_2.26 wcstof128_l F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 5a33b57390..d9c97779e4 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -108,6 +108,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.4 GLIBC_2.4 A
GLIBC_2.4 _Exit F
GLIBC_2.4 _IO_2_1_stderr_ D 0x98
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 50a86e74fa..4acbf7eeed 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -1985,6 +1985,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/microblaze/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/libc.abilist
index 250ef305c3..93f02f08ce 100644
--- a/sysdeps/unix/sysv/linux/microblaze/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/libc.abilist
@@ -2106,3 +2106,4 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 87a1dc4ad7..795e85de70 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -1960,6 +1960,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index f2b35f250e..dc714057b7 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -1958,6 +1958,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index ade654dbea..ce7bc9b175 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -1956,6 +1956,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 56032c3f82..3fdd85eace 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -1951,6 +1951,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index c599dd9212..3e0bcb2a5c 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2147,3 +2147,4 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 385409aa6e..375c69d9d1 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -1989,6 +1989,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index e99cb454b5..a88172a906 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -1994,6 +1994,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
index 173672ab5e..fa026a332c 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
@@ -2201,3 +2201,4 @@ GLIBC_2.26 wcstof128_l F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
index 8a654436ab..838f395d78 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
@@ -108,6 +108,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 _Exit F
GLIBC_2.3 _IO_2_1_stderr_ D 0xe0
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index dbd411ceb1..41b79c496a 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -1989,6 +1989,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index 5617784ca0..68251a0e69 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -1890,6 +1890,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/sh/libc.abilist b/sysdeps/unix/sysv/linux/sh/libc.abilist
index 0f840e6e88..bc1aae275e 100644
--- a/sysdeps/unix/sysv/linux/sh/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/libc.abilist
@@ -1875,6 +1875,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index bb7e1042c7..93e6d092ac 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -1982,6 +1982,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index 4053b0a51c..b11d6764d4 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -1919,6 +1919,7 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.27 strfromf128 F
GLIBC_2.27 strtof128 F
GLIBC_2.27 strtof128_l F
diff --git a/sysdeps/unix/sysv/linux/sys/memfd.h b/sysdeps/unix/sysv/linux/sys/memfd.h
new file mode 100644
index 0000000000..8255ecd7a4
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sys/memfd.h
@@ -0,0 +1,28 @@
+/* memfd_create system call and constants.
+ Copyright (C) 2017 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/>. */
+
+#ifndef _SYS_MEMFD_H
+#define _SYS_MEMFD_H
+
+#include <linux/memfd.h>
+
+/* Create a new memory file descriptor. NAME is a name for debugging.
+ FLAGS is a combination of the MFD_* constants. */
+int memfd_create (const char *__name, unsigned int __flags);
+
+#endif /* _SYS_MEMFD_H */
diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index 8bfb080d80..40c4fbb9ea 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -109,3 +109,4 @@ setns EXTRA setns i:ii setns
process_vm_readv EXTRA process_vm_readv i:ipipii process_vm_readv
process_vm_writev EXTRA process_vm_writev i:ipipii process_vm_writev
+memfd_create EXTRA memfd_create i:si memfd_create
diff --git a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
index 38a96d3a02..e9eb4ff7bd 100644
--- a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
@@ -2113,3 +2113,4 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
index 572b917d7d..8f08e909cd 100644
--- a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
@@ -2113,3 +2113,4 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
index 38a96d3a02..e9eb4ff7bd 100644
--- a/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
@@ -2113,3 +2113,4 @@ GLIBC_2.26 reallocarray F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
diff --git a/sysdeps/unix/sysv/linux/tst-memfd_create.c b/sysdeps/unix/sysv/linux/tst-memfd_create.c
new file mode 100644
index 0000000000..709cf46791
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-memfd_create.c
@@ -0,0 +1,134 @@
+/* Test for the memfd_create system call.
+ Copyright (C) 2017 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 <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/xunistd.h>
+#include <sys/syscall.h>
+
+#ifndef SYS_memfd_create
+static int
+do_test (void)
+{
+ puts ("warning: kernel headers do not support memfd_create");
+ return EXIT_UNSUPPORTED;
+}
+
+#else /* SYS_memfd_create */
+
+#include <sys/memfd.h>
+
+/* Return true if the descriptor has the FD_CLOEXEC flag set. */
+static bool
+is_cloexec (int fd)
+{
+ int flags = fcntl (fd, F_GETFD);
+ TEST_VERIFY (flags >= 0);
+ return flags & FD_CLOEXEC;
+}
+
+/* Return the seals set on FD. */
+static int
+get_seals (int fd)
+{
+ int flags = fcntl (fd, F_GET_SEALS);
+ TEST_VERIFY (flags >= 0);
+ return flags;
+}
+
+/* Return true if the F_SEAL_SEAL flag is set on the descriptor. */
+static bool
+is_sealed (int fd)
+{
+ return get_seals (fd) & F_SEAL_SEAL;
+}
+
+static int
+do_test (void)
+{
+ /* Initialized by the first call to memfd_create to 0 (memfd_create
+ unsupported) or 1 (memfd_create is implemented in the kernel).
+ Subsequent iterations check that the success/failure state is
+ consistent. */
+ int supported = -1;
+
+ for (int do_cloexec = 0; do_cloexec < 2; ++do_cloexec)
+ for (int do_sealing = 0; do_sealing < 2; ++do_sealing)
+ {
+ int flags = 0;
+ if (do_cloexec)
+ flags |= MFD_CLOEXEC;
+ if (do_sealing)
+ flags |= MFD_ALLOW_SEALING;
+ if (test_verbose > 0)
+ printf ("info: memfd_create with flags=0x%x\n", flags);
+ int fd = memfd_create ("tst-memfd_create", flags);
+ if (fd < 0)
+ {
+ if (errno == ENOSYS)
+ {
+ if (supported < 0)
+ {
+ supported = 0;
+ continue;
+ }
+ TEST_VERIFY (supported == 0);
+ continue;
+ }
+ else
+ FAIL_EXIT1 ("memfd_create: %m");
+ }
+ if (supported < 0)
+ supported = 1;
+ TEST_VERIFY (supported > 0);
+
+ char *fd_path = xasprintf ("/proc/self/fd/%d", fd);
+ char *link = xreadlink (fd_path);
+ if (test_verbose > 0)
+ printf ("info: memfd link: %s\n", link);
+ TEST_VERIFY (strcmp (link, "memfd:tst-memfd_create (deleted)"));
+ TEST_VERIFY (is_cloexec (fd) == do_cloexec);
+ TEST_VERIFY (is_sealed (fd) == !do_sealing);
+ if (do_sealing)
+ {
+ TEST_VERIFY (fcntl (fd, F_ADD_SEALS, F_SEAL_WRITE) == 0);
+ TEST_VERIFY (!is_sealed (fd));
+ TEST_VERIFY (get_seals (fd) & F_SEAL_WRITE);
+ TEST_VERIFY (fcntl (fd, F_ADD_SEALS, F_SEAL_SEAL) == 0);
+ TEST_VERIFY (is_sealed (fd));
+ }
+ xclose (fd);
+ free (fd_path);
+ free (link);
+ }
+
+ if (supported == 0)
+ return EXIT_UNSUPPORTED;
+ return 0;
+}
+
+#endif /* SYS_memfd_create */
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index b83d25c2e3..0a4f7797ac 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -1877,6 +1877,7 @@ GLIBC_2.26 wcstof128_l F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __ctype_b_loc F
GLIBC_2.3 __ctype_tolower_loc F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index cba1d59057..23f6a91429 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2120,3 +2120,4 @@ GLIBC_2.26 wcstof128_l F
GLIBC_2.27 GLIBC_2.27 A
GLIBC_2.27 glob F
GLIBC_2.27 glob64 F
+GLIBC_2.27 memfd_create F