1 /*
2 * Copyright (c) 2019, Mellanox Technologies. All rights reserved.
3 * Copyright (C) 2023 Intel Corporation.
4 *
5 * This software is available to you under a choice of one of two
6 * licenses. You may choose to be licensed under the terms of the GNU
7 * General Public License (GPL) Version 2, available from the file
8 * COPYING in the main directory of this source tree, or the
9 * OpenIB.org BSD license below:
10 *
11 * Redistribution and use in source and binary forms, with or
12 * without modification, are permitted provided that the following
13 * conditions are met:
14 *
15 * - Redistributions of source code must retain the above
16 * copyright notice, this list of conditions and the following
17 * disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials
22 * provided with the distribution.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
28 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
29 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
30 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
31 * SOFTWARE.
32 *
33 * Authors: Yi Liu <yi.l.liu@intel.com>
34 *
35 * Copied from
36 * https://github.com/linux-rdma/rdma-core/blob/master/util/open_cdev.c
37 *
38 */
39
40 #include "qemu/osdep.h"
41 #include "qemu/chardev_open.h"
42
open_cdev_internal(const char * path,dev_t cdev)43 static int open_cdev_internal(const char *path, dev_t cdev)
44 {
45 struct stat st;
46 int fd;
47
48 fd = qemu_open_old(path, O_RDWR);
49 if (fd == -1) {
50 return -1;
51 }
52 if (fstat(fd, &st) || !S_ISCHR(st.st_mode) ||
53 (cdev != 0 && st.st_rdev != cdev)) {
54 close(fd);
55 return -1;
56 }
57 return fd;
58 }
59
open_cdev_robust(dev_t cdev)60 static int open_cdev_robust(dev_t cdev)
61 {
62 g_autofree char *devpath = NULL;
63
64 /*
65 * This assumes that udev is being used and is creating the /dev/char/
66 * symlinks.
67 */
68 devpath = g_strdup_printf("/dev/char/%u:%u", major(cdev), minor(cdev));
69 return open_cdev_internal(devpath, cdev);
70 }
71
open_cdev(const char * devpath,dev_t cdev)72 int open_cdev(const char *devpath, dev_t cdev)
73 {
74 int fd;
75
76 fd = open_cdev_internal(devpath, cdev);
77 if (fd == -1 && cdev != 0) {
78 return open_cdev_robust(cdev);
79 }
80 return fd;
81 }
82