142 lines
3.5 KiB
C
142 lines
3.5 KiB
C
/* $NetBSD: shm.c,v 1.3 2015/07/08 07:14:38 martin Exp $ */
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/*-
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* Copyright (c) 2013 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Mindaugas Rasiukevicius.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Interface for POSIX shared memory objects.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: shm.c,v 1.3 2015/07/08 07:14:38 martin Exp $");
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#include <sys/mman.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <stdio.h>
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#include <stdbool.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <limits.h>
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/*
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* Shared memory objects are supported using tmpfs.
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*/
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#define SHMFS_DIR_PATH "/var/shm"
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#define SHMFS_DIR_MODE (S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
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#define SHMFS_OBJ_PREFIX ".shmobj_"
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#define MOUNT_SHMFS MOUNT_TMPFS
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static bool shm_ok = false;
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static bool
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_shm_check_fs(void)
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{
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int fd;
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struct statvfs sv;
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struct stat st;
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fd = open(SHMFS_DIR_PATH, O_DIRECTORY|O_RDONLY);
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if (fd == -1)
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return false;
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if (fstatvfs1(fd, &sv, ST_NOWAIT) == -1)
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goto out;
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if (strncmp(sv.f_fstypename, MOUNT_SHMFS, sizeof(sv.f_fstypename)))
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goto out;
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if (fstat(fd, &st) == -1)
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goto out;
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if ((st.st_mode & SHMFS_DIR_MODE) != SHMFS_DIR_MODE)
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goto out;
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shm_ok = true;
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out:
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close(fd);
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return shm_ok;
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}
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static bool
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_shm_get_path(char *buf, size_t len, const char *name)
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{
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int ret;
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if (__predict_false(!shm_ok) && !_shm_check_fs()) {
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errno = ENOTSUP;
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return false;
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}
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/*
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* As per POSIX: the name should begin with a slash character.
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* We may disallow other slashes (implementation-defined behaviour).
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*/
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if (*name++ != '/' || strchr(name, '/') != NULL) {
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errno = EINVAL;
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return false;
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}
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ret = snprintf(buf, len, SHMFS_DIR_PATH "/" SHMFS_OBJ_PREFIX "%s",
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name);
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if ((size_t)ret >= len) {
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errno = ENAMETOOLONG;
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return false;
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}
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return ret != -1;
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}
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int
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shm_open(const char *name, int oflag, mode_t mode)
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{
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char path[PATH_MAX];
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if (!_shm_get_path(path, sizeof(path), name)) {
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return -1;
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}
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return open(path, oflag | O_CLOEXEC | O_NOFOLLOW, mode);
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}
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int
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shm_unlink(const char *name)
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{
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char path[PATH_MAX];
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if (!_shm_get_path(path, sizeof(path), name)) {
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return -1;
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}
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return unlink(path);
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}
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