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1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4#include <linux/slab.h>
5#include <linux/types.h>
6#include <linux/mm.h>
7#include <linux/fs.h>
8#include <linux/miscdevice.h>
9#include <linux/init.h>
10#include <linux/capability.h>
11
12#include <xen/xen.h>
13#include <xen/page.h>
14#include <xen/xenbus.h>
15#include <xen/xenbus_dev.h>
16#include <xen/grant_table.h>
17#include <xen/events.h>
18#include <asm/xen/hypervisor.h>
19
20#include "xenbus.h"
21
22static int xenbus_backend_open(struct inode *inode, struct file *filp)
23{
24 if (!capable(CAP_SYS_ADMIN))
25 return -EPERM;
26
27 return nonseekable_open(inode, filp);
28}
29
30static long xenbus_alloc(domid_t domid)
31{
32 struct evtchn_alloc_unbound arg;
33 int err = -EEXIST;
34
35 xs_suspend();
36
37 /* If xenstored_ready is nonzero, that means we have already talked to
38 * xenstore and set up watches. These watches will be restored by
39 * xs_resume, but that requires communication over the port established
40 * below that is not visible to anyone until the ioctl returns.
41 *
42 * This can be resolved by splitting the ioctl into two parts
43 * (postponing the resume until xenstored is active) but this is
44 * unnecessarily complex for the intended use where xenstored is only
45 * started once - so return -EEXIST if it's already running.
46 */
47 if (xenstored_ready)
48 goto out_err;
49
50 gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,
51 virt_to_gfn(xen_store_interface), 0 /* writable */);
52
53 arg.dom = DOMID_SELF;
54 arg.remote_dom = domid;
55
56 err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);
57 if (err)
58 goto out_err;
59
60 if (xen_store_evtchn > 0)
61 xb_deinit_comms();
62
63 xen_store_evtchn = arg.port;
64
65 xs_resume();
66
67 return arg.port;
68
69 out_err:
70 xs_suspend_cancel();
71 return err;
72}
73
74static long xenbus_backend_ioctl(struct file *file, unsigned int cmd,
75 unsigned long data)
76{
77 if (!capable(CAP_SYS_ADMIN))
78 return -EPERM;
79
80 switch (cmd) {
81 case IOCTL_XENBUS_BACKEND_EVTCHN:
82 if (xen_store_evtchn > 0)
83 return xen_store_evtchn;
84 return -ENODEV;
85 case IOCTL_XENBUS_BACKEND_SETUP:
86 return xenbus_alloc(data);
87 default:
88 return -ENOTTY;
89 }
90}
91
92static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
93{
94 size_t size = vma->vm_end - vma->vm_start;
95
96 if (!capable(CAP_SYS_ADMIN))
97 return -EPERM;
98
99 if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
100 return -EINVAL;
101
102 if (remap_pfn_range(vma, vma->vm_start,
103 virt_to_pfn(xen_store_interface),
104 size, vma->vm_page_prot))
105 return -EAGAIN;
106
107 return 0;
108}
109
110static const struct file_operations xenbus_backend_fops = {
111 .open = xenbus_backend_open,
112 .mmap = xenbus_backend_mmap,
113 .unlocked_ioctl = xenbus_backend_ioctl,
114};
115
116static struct miscdevice xenbus_backend_dev = {
117 .minor = MISC_DYNAMIC_MINOR,
118 .name = "xen/xenbus_backend",
119 .fops = &xenbus_backend_fops,
120};
121
122static int __init xenbus_backend_init(void)
123{
124 int err;
125
126 if (!xen_initial_domain())
127 return -ENODEV;
128
129 err = misc_register(&xenbus_backend_dev);
130 if (err)
131 pr_err("Could not register xenbus backend device\n");
132 return err;
133}
134device_initcall(xenbus_backend_init);
1#include <linux/slab.h>
2#include <linux/types.h>
3#include <linux/mm.h>
4#include <linux/fs.h>
5#include <linux/miscdevice.h>
6#include <linux/module.h>
7#include <linux/capability.h>
8
9#include <xen/xen.h>
10#include <xen/page.h>
11#include <xen/xenbus.h>
12#include <xen/xenbus_dev.h>
13#include <xen/grant_table.h>
14#include <xen/events.h>
15#include <asm/xen/hypervisor.h>
16
17#include "xenbus_comms.h"
18
19MODULE_LICENSE("GPL");
20
21static int xenbus_backend_open(struct inode *inode, struct file *filp)
22{
23 if (!capable(CAP_SYS_ADMIN))
24 return -EPERM;
25
26 return nonseekable_open(inode, filp);
27}
28
29static long xenbus_alloc(domid_t domid)
30{
31 struct evtchn_alloc_unbound arg;
32 int err = -EEXIST;
33
34 xs_suspend();
35
36 /* If xenstored_ready is nonzero, that means we have already talked to
37 * xenstore and set up watches. These watches will be restored by
38 * xs_resume, but that requires communication over the port established
39 * below that is not visible to anyone until the ioctl returns.
40 *
41 * This can be resolved by splitting the ioctl into two parts
42 * (postponing the resume until xenstored is active) but this is
43 * unnecessarily complex for the intended use where xenstored is only
44 * started once - so return -EEXIST if it's already running.
45 */
46 if (xenstored_ready)
47 goto out_err;
48
49 gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,
50 virt_to_mfn(xen_store_interface), 0 /* writable */);
51
52 arg.dom = DOMID_SELF;
53 arg.remote_dom = domid;
54
55 err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);
56 if (err)
57 goto out_err;
58
59 if (xen_store_evtchn > 0)
60 xb_deinit_comms();
61
62 xen_store_evtchn = arg.port;
63
64 xs_resume();
65
66 return arg.port;
67
68 out_err:
69 xs_suspend_cancel();
70 return err;
71}
72
73static long xenbus_backend_ioctl(struct file *file, unsigned int cmd, unsigned long data)
74{
75 if (!capable(CAP_SYS_ADMIN))
76 return -EPERM;
77
78 switch (cmd) {
79 case IOCTL_XENBUS_BACKEND_EVTCHN:
80 if (xen_store_evtchn > 0)
81 return xen_store_evtchn;
82 return -ENODEV;
83
84 case IOCTL_XENBUS_BACKEND_SETUP:
85 return xenbus_alloc(data);
86
87 default:
88 return -ENOTTY;
89 }
90}
91
92static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
93{
94 size_t size = vma->vm_end - vma->vm_start;
95
96 if (!capable(CAP_SYS_ADMIN))
97 return -EPERM;
98
99 if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
100 return -EINVAL;
101
102 if (remap_pfn_range(vma, vma->vm_start,
103 virt_to_pfn(xen_store_interface),
104 size, vma->vm_page_prot))
105 return -EAGAIN;
106
107 return 0;
108}
109
110const struct file_operations xenbus_backend_fops = {
111 .open = xenbus_backend_open,
112 .mmap = xenbus_backend_mmap,
113 .unlocked_ioctl = xenbus_backend_ioctl,
114};
115
116static struct miscdevice xenbus_backend_dev = {
117 .minor = MISC_DYNAMIC_MINOR,
118 .name = "xen/xenbus_backend",
119 .fops = &xenbus_backend_fops,
120};
121
122static int __init xenbus_backend_init(void)
123{
124 int err;
125
126 if (!xen_initial_domain())
127 return -ENODEV;
128
129 err = misc_register(&xenbus_backend_dev);
130 if (err)
131 printk(KERN_ERR "Could not register xenbus backend device\n");
132 return err;
133}
134
135static void __exit xenbus_backend_exit(void)
136{
137 misc_deregister(&xenbus_backend_dev);
138}
139
140module_init(xenbus_backend_init);
141module_exit(xenbus_backend_exit);