bpo-26836: Add os.memfd_create() (#13567)

* bpo-26836: Add os.memfd_create()

* Use the glibc wrapper for memfd_create()

Co-Authored-By: Christian Heimes <[email protected]>

* Fix deletions caused by autoreconf.

* Use MFD_CLOEXEC as the default value for *flags*.

* Add memset_s to configure.ac.

* Revert memset_s changes.

* Apply the requested changes.

* Tweak the docs.

Doc/library/os.rst

@@ -2982,6 +2982,44 @@ features:
       Added support for :class:`bytes` paths.
 
 
+.. function:: memfd_create(name[, flags=os.MFD_CLOEXEC])
+
+   Create an anonymous file and return a file descriptor that refers to it.
+   *flags* must be one of the ``os.MFD_*`` constants available on the system
+   (or a bitwise ORed combination of them).  By default, the new file
+   descriptor is :ref:`non-inheritable <fd_inheritance>`.
+
+   .. availability:: Linux 3.17 or newer with glibc 2.27 or newer.
+
+   .. versionadded:: 3.8
+
+
+.. data:: MFD_CLOEXEC
+          MFD_ALLOW_SEALING
+          MFD_HUGETLB
+          MFD_HUGE_SHIFT
+          MFD_HUGE_MASK
+          MFD_HUGE_64KB
+          MFD_HUGE_512KB
+          MFD_HUGE_1MB
+          MFD_HUGE_2MB
+          MFD_HUGE_8MB
+          MFD_HUGE_16MB
+          MFD_HUGE_32MB
+          MFD_HUGE_256MB
+          MFD_HUGE_512MB
+          MFD_HUGE_1GB
+          MFD_HUGE_2GB
+          MFD_HUGE_16GB
+
+   These flags can be passed to :func:`memfd_create`.
+
+   .. availability:: Linux 3.17 or newer with glibc 2.27 or newer.  The
+      ``MFD_HUGE*`` flags are only available since Linux 4.14.
+
+   .. versionadded:: 3.8
+
+
 Linux extended attributes
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 

Doc/whatsnew/3.8.rst

@@ -486,6 +486,10 @@ Added new function :func:`~os.add_dll_directory` on Windows for providing
 additional search paths for native dependencies when importing extension
 modules or loading DLLs using :mod:`ctypes`.
 
+A new :func:`os.memfd_create` function was added to wrap the
+``memfd_create()`` syscall.
+(Contributed by Zackery Spytz and Christian Heimes in :issue:`26836`.)
+
 
 os.path
 -------

Lib/test/test_os.py

@@ -3122,6 +3122,22 @@ def test_stty_match(self):
         self.assertEqual(expected, actual)
 
 
+@unittest.skipUnless(hasattr(os, 'memfd_create'), 'requires os.memfd_create')
+class MemfdCreateTests(unittest.TestCase):
+    def test_memfd_create(self):
+        fd = os.memfd_create("Hi", os.MFD_CLOEXEC)
+        self.assertNotEqual(fd, -1)
+        self.addCleanup(os.close, fd)
+        self.assertFalse(os.get_inheritable(fd))
+        with open(fd, "wb", closefd=False) as f:
+            f.write(b'memfd_create')
+            self.assertEqual(f.tell(), 12)
+
+        fd2 = os.memfd_create("Hi")
+        self.addCleanup(os.close, fd2)
+        self.assertFalse(os.get_inheritable(fd2))
+
+
 class OSErrorTests(unittest.TestCase):
     def setUp(self):
         class Str(str):

Misc/NEWS.d/next/Core and Builtins/2019-05-25-08-18-01.bpo-26836.rplYWW.rst

@@ -0,0 +1 @@
+Add :func:`os.memfd_create`.

Modules/posixmodule.c

@@ -389,6 +389,19 @@ extern char        *ctermid_r(char *);
 #define HAVE_STRUCT_STAT_ST_FSTYPE 1
 #endif
 
+/* memfd_create is either defined in sys/mman.h or sys/memfd.h
+ * linux/memfd.h defines additional flags
+ */
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+#ifdef HAVE_SYS_MEMFD_H
+#include <sys/memfd.h>
+#endif
+#ifdef HAVE_LINUX_MEMFD_H
+#include <linux/memfd.h>
+#endif
+
 #ifdef _Py_MEMORY_SANITIZER
 # include <sanitizer/msan_interface.h>
 #endif
@@ -11897,6 +11910,31 @@ os_urandom_impl(PyObject *module, Py_ssize_t size)
     return bytes;
 }
 
+#ifdef HAVE_MEMFD_CREATE
+/*[clinic input]
+os.memfd_create
+
+    name: FSConverter
+    flags: unsigned_int(bitwise=True, c_default="MFD_CLOEXEC") = MFD_CLOEXEC
+
+[clinic start generated code]*/
+
+static PyObject *
+os_memfd_create_impl(PyObject *module, PyObject *name, unsigned int flags)
+/*[clinic end generated code: output=6681ede983bdb9a6 input=a42cfc199bcd56e9]*/
+{
+    int fd;
+    const char *bytes = PyBytes_AS_STRING(name);
+    Py_BEGIN_ALLOW_THREADS
+    fd = memfd_create(bytes, flags);
+    Py_END_ALLOW_THREADS
+    if (fd == -1) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
+    return PyLong_FromLong(fd);
+}
+#endif
+
 /* Terminal size querying */
 
 static PyTypeObject* TerminalSizeType;
@@ -13554,6 +13592,7 @@ static PyMethodDef posix_methods[] = {
     OS_SCANDIR_METHODDEF
     OS_FSPATH_METHODDEF
     OS_GETRANDOM_METHODDEF
+    OS_MEMFD_CREATE_METHODDEF
 #ifdef MS_WINDOWS
     OS__ADD_DLL_DIRECTORY_METHODDEF
     OS__REMOVE_DLL_DIRECTORY_METHODDEF
@@ -14003,6 +14042,27 @@ all_ins(PyObject *m)
     if (PyModule_AddIntMacro(m, GRND_RANDOM)) return -1;
     if (PyModule_AddIntMacro(m, GRND_NONBLOCK)) return -1;
 #endif
+#ifdef HAVE_MEMFD_CREATE
+    if (PyModule_AddIntMacro(m, MFD_CLOEXEC)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_ALLOW_SEALING)) return -1;
+#ifdef MFD_HUGETLB
+    if (PyModule_AddIntMacro(m, MFD_HUGETLB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_SHIFT)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_MASK)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_64KB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_512KB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_1MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_2MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_8MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_16MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_32MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_256MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_512MB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_1GB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_2GB)) return -1;
+    if (PyModule_AddIntMacro(m, MFD_HUGE_16GB)) return -1;
+#endif
+#endif
 
 #if defined(__APPLE__)
     if (PyModule_AddIntConstant(m, "_COPYFILE_DATA", COPYFILE_DATA)) return -1;
@@ -14119,6 +14179,10 @@ static const char * const have_functions[] = {
     "HAVE_LUTIMES",
 #endif
 
+#ifdef HAVE_MEMFD_CREATE
+    "HAVE_MEMFD_CREATE",
+#endif
+
 #ifdef HAVE_MKDIRAT
     "HAVE_MKDIRAT",
 #endif

aclocal.m4

@@ -55,7 +55,7 @@ dnl
 dnl See the "Since" comment for each macro you use to see what version
 dnl of the macros you require.
 m4_defun([PKG_PREREQ],
-[m4_define([PKG_MACROS_VERSION], [0.29.2])
+[m4_define([PKG_MACROS_VERSION], [0.29.1])
 m4_if(m4_version_compare(PKG_MACROS_VERSION, [$1]), -1,
     [m4_fatal([pkg.m4 version $1 or higher is required but ]PKG_MACROS_VERSION[ found])])
 ])dnl PKG_PREREQ
@@ -156,7 +156,7 @@ AC_ARG_VAR([$1][_CFLAGS], [C compiler flags for $1, overriding pkg-config])dnl
 AC_ARG_VAR([$1][_LIBS], [linker flags for $1, overriding pkg-config])dnl
 
 pkg_failed=no
-AC_MSG_CHECKING([for $2])
+AC_MSG_CHECKING([for $1])
 
 _PKG_CONFIG([$1][_CFLAGS], [cflags], [$2])
 _PKG_CONFIG([$1][_LIBS], [libs], [$2])
@@ -166,11 +166,11 @@ and $1[]_LIBS to avoid the need to call pkg-config.
 See the pkg-config man page for more details.])
 
 if test $pkg_failed = yes; then
-        AC_MSG_RESULT([no])
+   	AC_MSG_RESULT([no])
         _PKG_SHORT_ERRORS_SUPPORTED
         if test $_pkg_short_errors_supported = yes; then
 	        $1[]_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "$2" 2>&1`
-        else
+        else 
 	        $1[]_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "$2" 2>&1`
         fi
 	# Put the nasty error message in config.log where it belongs
@@ -187,7 +187,7 @@ installed software in a non-standard prefix.
 _PKG_TEXT])[]dnl
         ])
 elif test $pkg_failed = untried; then
-        AC_MSG_RESULT([no])
+     	AC_MSG_RESULT([no])
 	m4_default([$4], [AC_MSG_FAILURE(
 [The pkg-config script could not be found or is too old.  Make sure it
 is in your PATH or set the PKG_CONFIG environment variable to the full

configure

@@ -785,6 +785,7 @@ infodir
 docdir
 oldincludedir
 includedir
+runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -897,6 +898,7 @@ datadir='${datarootdir}'
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
+runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -1149,6 +1151,15 @@ do
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
+  -runstatedir | --runstatedir | --runstatedi | --runstated \
+  | --runstate | --runstat | --runsta | --runst | --runs \
+  | --run | --ru | --r)
+    ac_prev=runstatedir ;;
+  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
+  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
+  | --run=* | --ru=* | --r=*)
+    runstatedir=$ac_optarg ;;
+
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1286,7 +1297,7 @@ fi
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir
+		libdir localedir mandir runstatedir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -1439,6 +1450,7 @@ Fine tuning of the installation directories:
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
+  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]
@@ -7892,7 +7904,7 @@ sys/stat.h sys/syscall.h sys/sys_domain.h sys/termio.h sys/time.h \
 sys/times.h sys/types.h sys/uio.h sys/un.h sys/utsname.h sys/wait.h pty.h \
 libutil.h sys/resource.h netpacket/packet.h sysexits.h bluetooth.h \
 linux/tipc.h linux/random.h spawn.h util.h alloca.h endian.h \
-sys/endian.h sys/sysmacros.h
+sys/endian.h sys/sysmacros.h linux/memfd.h sys/memfd.h sys/mman.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
@@ -11785,6 +11797,39 @@ $as_echo "no" >&6; }
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for memfd_create" >&5
+$as_echo_n "checking for memfd_create... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+#ifdef HAVE_SYS_MEMFD_H
+#include <sys/memfd.h>
+#endif
+
+int
+main ()
+{
+void *x=memfd_create
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+$as_echo "#define HAVE_MEMFD_CREATE 1" >>confdefs.h
+
+   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
 # On some systems (eg. FreeBSD 5), we would find a definition of the
 # functions ctermid_r, setgroups in the library, but no prototype
 # (e.g. because we use _XOPEN_SOURCE). See whether we can take their