xref: /openbmc/qemu/util/chardev_open.c (revision 764a6ee9)
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 
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 
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 
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