[src/trunk]: src Add shm_open(3) and shm_unlink(3) to support POSIX shared me...

[rmind <rmind%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/5a9b31338aab
branches:  trunk
changeset: 325342:5a9b31338aab
user:      rmind <rmind%NetBSD.org@localhost>
date:      Thu Dec 19 19:11:50 2013 +0000

description:
Add shm_open(3) and shm_unlink(3) to support POSIX shared memory objects.
They are implemented using tmpfs (mounted at /var/shm).

Discussed on tech-{kern,userlevel} (quite a while ago).

diffstat:

 lib/libc/gen/sysconf.c    |    6 +-
 lib/librt/Makefile        |    6 +-
 lib/librt/shm.c           |  136 ++++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/mman.h            |    4 +-
 sys/sys/unistd.h          |    9 +-
 usr.bin/getconf/getconf.c |    5 +-
 6 files changed, 154 insertions(+), 12 deletions(-)

diffs (262 lines):

diff -r a6a7e80d5fc4 -r 5a9b31338aab lib/libc/gen/sysconf.c
--- a/lib/libc/gen/sysconf.c    Thu Dec 19 15:51:39 2013 +0000
+++ b/lib/libc/gen/sysconf.c    Thu Dec 19 19:11:50 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sysconf.c,v 1.35 2012/11/02 21:43:07 christos Exp $    */
+/*     $NetBSD: sysconf.c,v 1.36 2013/12/19 19:11:50 rmind Exp $       */
 
 /*-
  * Copyright (c) 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)sysconf.c  8.2 (Berkeley) 3/20/94";
 #else
-__RCSID("$NetBSD: sysconf.c,v 1.35 2012/11/02 21:43:07 christos Exp $");
+__RCSID("$NetBSD: sysconf.c,v 1.36 2013/12/19 19:11:50 rmind Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -345,6 +345,8 @@
                return _PASSWORD_LEN;
        case _SC_REGEXP:
                return _POSIX_REGEXP;
+       case _SC_SHARED_MEMORY_OBJECTS:
+               return _POSIX_SHARED_MEMORY_OBJECTS;
        case _SC_SHELL:
                return _POSIX_SHELL;
        case _SC_SPAWN:
diff -r a6a7e80d5fc4 -r 5a9b31338aab lib/librt/Makefile
--- a/lib/librt/Makefile        Thu Dec 19 15:51:39 2013 +0000
+++ b/lib/librt/Makefile        Thu Dec 19 19:11:50 2013 +0000
@@ -1,4 +1,4 @@
-#      $NetBSD: Makefile,v 1.16 2012/03/21 05:37:43 matt Exp $
+#      $NetBSD: Makefile,v 1.17 2013/12/19 19:11:50 rmind Exp $
 #
 
 .include <bsd.own.mk>
@@ -6,8 +6,8 @@
 WARNS?=        5
 
 LIB=   rt
-SRCS=  sem.c
-SRCS+= pset.c
+
+SRCS=  sem.c shm.c pset.c
 
 MAN+=  aio.3 aio_cancel.3 aio_error.3 aio_fsync.3 aio_read.3 aio_return.3 \
        aio_suspend.3 aio_write.3 lio_listio.3 \
diff -r a6a7e80d5fc4 -r 5a9b31338aab lib/librt/shm.c
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/librt/shm.c   Thu Dec 19 19:11:50 2013 +0000
@@ -0,0 +1,136 @@
+/*     $NetBSD: shm.c,v 1.1 2013/12/19 19:11:50 rmind Exp $    */
+
+/*-
+ * Copyright (c) 2013 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Mindaugas Rasiukevicius.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Interface for POSIX shared memory objects.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: shm.c,v 1.1 2013/12/19 19:11:50 rmind Exp $");
+
+#include <sys/mman.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <limits.h>
+
+/*
+ * Shared memory objects are supported using tmpfs.
+ */
+#define        SHMFS_DIR_PATH          "/var/shm"
+#define        SHMFS_DIR_MODE          (S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
+#define        SHMFS_OBJ_PREFIX        ".shmobj_"
+
+#define        MOUNT_SHMFS             MOUNT_TMPFS
+
+static const char *            _shmfs_path = NULL;
+
+static bool
+_shm_check_fs(void)
+{
+       const char *shmfs = SHMFS_DIR_PATH;
+       struct statvfs sv;
+       struct stat st;
+
+       if (statvfs1(shmfs, &sv, ST_NOWAIT) == -1) {
+               return false;
+       }
+       if (strncmp(sv.f_fstypename, MOUNT_SHMFS, sizeof(sv.f_fstypename))) {
+               return false;
+       }
+
+       if (lstat(shmfs, &st) == -1) {
+               return false;
+       }
+       if ((st.st_mode & SHMFS_DIR_MODE) != SHMFS_DIR_MODE) {
+               return false;
+       }
+
+       _shmfs_path = shmfs;
+       return true;
+}
+
+static bool
+_shm_get_path(char *buf, size_t len, const char *name)
+{
+       int ret;
+
+       if (__predict_false(!_shmfs_path) && !_shm_check_fs()) {
+               errno = ENOTSUP;
+               return false;
+       }
+
+       /*
+        * As per POSIX: the name should begin with a slash character.
+        * We may disallow other slashes (implementation-defined behaviour).
+        */
+       if (*name++ != '/' || strchr(name, '/') != NULL) {
+               errno = EINVAL;
+               return false;
+       }
+
+       ret = snprintf(buf, len, "%s/%s%s",
+           _shmfs_path, SHMFS_OBJ_PREFIX, name);
+
+       if ((size_t)ret >= PATH_MAX) {
+               errno = ENAMETOOLONG;
+               return false;
+       }
+       return ret != -1;
+}
+
+int
+shm_open(const char *name, int oflag, mode_t mode)
+{
+       char path[PATH_MAX + 1];
+
+       if (!_shm_get_path(path, sizeof(path), name)) {
+               return -1;
+       }
+       return open(path, oflag | O_CLOEXEC | O_NOFOLLOW, mode);
+}
+
+int
+shm_unlink(const char *name)
+{
+       char path[PATH_MAX + 1];
+
+       if (!_shm_get_path(path, sizeof(path), name)) {
+               return -1;
+       }
+       return unlink(path);
+}
diff -r a6a7e80d5fc4 -r 5a9b31338aab sys/sys/mman.h
--- a/sys/sys/mman.h    Thu Dec 19 15:51:39 2013 +0000
+++ b/sys/sys/mman.h    Thu Dec 19 19:11:50 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mman.h,v 1.44 2012/01/05 15:19:52 reinoud Exp $        */
+/*     $NetBSD: mman.h,v 1.45 2013/12/19 19:11:50 rmind Exp $  */
 
 /*-
  * Copyright (c) 1982, 1986, 1993
@@ -185,6 +185,8 @@
 void * mremap(void *, size_t, void *, size_t, int);
 #endif
 int    posix_madvise(void *, size_t, int);
+int    shm_open(const char *, int, mode_t);
+int    shm_unlink(const char *);
 __END_DECLS
 
 #endif /* !_KERNEL */
diff -r a6a7e80d5fc4 -r 5a9b31338aab sys/sys/unistd.h
--- a/sys/sys/unistd.h  Thu Dec 19 15:51:39 2013 +0000
+++ b/sys/sys/unistd.h  Thu Dec 19 19:11:50 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: unistd.h,v 1.54 2012/11/02 21:41:26 christos Exp $     */
+/*     $NetBSD: unistd.h,v 1.55 2013/12/19 19:11:50 rmind Exp $        */
 
 /*
  * Copyright (c) 1989, 1993
@@ -129,8 +129,8 @@
 #define        _POSIX_REGEXP                   1
                                        /* semaphores */
 #define        _POSIX_SEMAPHORES               0
-                                       /* shared memory */
-#undef _POSIX_SHARED_MEMORY_OBJECTS
+                                       /* shared memory objects */
+#define        _POSIX_SHARED_MEMORY_OBJECTS    0
                                        /* shell */
 #define        _POSIX_SHELL                    1
                                        /* spin locks */
@@ -303,8 +303,9 @@
 #define        _SC_2_PBS_MESSAGE               84
 #define        _SC_2_PBS_TRACK                 85
 
-/* This is implemented */
+/* These are implemented */
 #define        _SC_SPAWN                       86
+#define        _SC_SHARED_MEMORY_OBJECTS       87
 
 /* Extensions found in Solaris and Linux. */
 #define        _SC_PHYS_PAGES          121
diff -r a6a7e80d5fc4 -r 5a9b31338aab usr.bin/getconf/getconf.c
--- a/usr.bin/getconf/getconf.c Thu Dec 19 15:51:39 2013 +0000
+++ b/usr.bin/getconf/getconf.c Thu Dec 19 19:11:50 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: getconf.c,v 1.34 2008/08/27 08:56:49 christos Exp $    */
+/*     $NetBSD: getconf.c,v 1.35 2013/12/19 19:11:50 rmind Exp $       */
 
 /*-
  * Copyright (c) 1996, 1998 The NetBSD Foundation, Inc.
@@ -31,7 +31,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: getconf.c,v 1.34 2008/08/27 08:56:49 christos Exp $");
+__RCSID("$NetBSD: getconf.c,v 1.35 2013/12/19 19:11:50 rmind Exp $");
 #endif /* not lint */
 
 #include <err.h>
@@ -147,6 +147,7 @@
   { "_POSIX_MONOTONIC_CLOCK",  SYSCONF,        _SC_MONOTONIC_CLOCK     },
   { "_POSIX_PRIORITY_SCHEDULING", SYSCONF,     _SC_PRIORITY_SCHEDULING },
   { "_POSIX_SEMAPHORES",       SYSCONF,        _SC_SEMAPHORES          },
+  { "_POSIX_SHARED_MEMORY_OBJECTS", SYSCONF,   _SC_SHARED_MEMORY_OBJECTS },
   { "_POSIX_SYNCHRONIZED_IO",  SYSCONF,        _SC_SYNCHRONIZED_IO     },
   { "_POSIX_TIMERS",           SYSCONF,        _SC_TIMERS              },