summaryrefslogtreecommitdiff
path: root/drivers/xen/privcmd-buf.c
blob: de01a6d0059dc4adcb98a24197750f72b0b4ceaf (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
// SPDX-License-Identifier: GPL-2.0 OR MIT

/******************************************************************************
 * privcmd-buf.c
 *
 * Mmap of hypercall buffers.
 *
 * Copyright (c) 2018 Juergen Gross
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/slab.h>

#include "privcmd.h"

MODULE_LICENSE("GPL");

struct privcmd_buf_private {
	struct mutex lock;
	struct list_head list;
};

struct privcmd_buf_vma_private {
	struct privcmd_buf_private *file_priv;
	struct list_head list;
	unsigned int users;
	unsigned int n_pages;
	struct page *pages[];
};

static int privcmd_buf_open(struct inode *ino, struct file *file)
{
	struct privcmd_buf_private *file_priv;

	file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL);
	if (!file_priv)
		return -ENOMEM;

	mutex_init(&file_priv->lock);
	INIT_LIST_HEAD(&file_priv->list);

	file->private_data = file_priv;

	return 0;
}

static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv)
{
	unsigned int i;

	list_del(&vma_priv->list);

	for (i = 0; i < vma_priv->n_pages; i++)
		__free_page(vma_priv->pages[i]);

	kfree(vma_priv);
}

static int privcmd_buf_release(struct inode *ino, struct file *file)
{
	struct privcmd_buf_private *file_priv = file->private_data;
	struct privcmd_buf_vma_private *vma_priv;

	mutex_lock(&file_priv->lock);

	while (!list_empty(&file_priv->list)) {
		vma_priv = list_first_entry(&file_priv->list,
					    struct privcmd_buf_vma_private,
					    list);
		privcmd_buf_vmapriv_free(vma_priv);
	}

	mutex_unlock(&file_priv->lock);

	kfree(file_priv);

	return 0;
}

static void privcmd_buf_vma_open(struct vm_area_struct *vma)
{
	struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;

	if (!vma_priv)
		return;

	mutex_lock(&vma_priv->file_priv->lock);
	vma_priv->users++;
	mutex_unlock(&vma_priv->file_priv->lock);
}

static void privcmd_buf_vma_close(struct vm_area_struct *vma)
{
	struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
	struct privcmd_buf_private *file_priv;

	if (!vma_priv)
		return;

	file_priv = vma_priv->file_priv;

	mutex_lock(&file_priv->lock);

	vma_priv->users--;
	if (!vma_priv->users)
		privcmd_buf_vmapriv_free(vma_priv);

	mutex_unlock(&file_priv->lock);
}

static vm_fault_t privcmd_buf_vma_fault(struct vm_fault *vmf)
{
	pr_debug("fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
		 vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end,
		 vmf->pgoff, (void *)vmf->address);

	return VM_FAULT_SIGBUS;
}

static const struct vm_operations_struct privcmd_buf_vm_ops = {
	.open = privcmd_buf_vma_open,
	.close = privcmd_buf_vma_close,
	.fault = privcmd_buf_vma_fault,
};

static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct privcmd_buf_private *file_priv = file->private_data;
	struct privcmd_buf_vma_private *vma_priv;
	unsigned long count = vma_pages(vma);
	unsigned int i;
	int ret = 0;

	if (!(vma->vm_flags & VM_SHARED))
		return -EINVAL;

	vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *),
			   GFP_KERNEL);
	if (!vma_priv)
		return -ENOMEM;

	for (i = 0; i < count; i++) {
		vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
		if (!vma_priv->pages[i])
			break;
		vma_priv->n_pages++;
	}

	mutex_lock(&file_priv->lock);

	vma_priv->file_priv = file_priv;
	vma_priv->users = 1;

	vma->vm_flags |= VM_IO | VM_DONTEXPAND;
	vma->vm_ops = &privcmd_buf_vm_ops;
	vma->vm_private_data = vma_priv;

	list_add(&vma_priv->list, &file_priv->list);

	if (vma_priv->n_pages != count)
		ret = -ENOMEM;
	else
		for (i = 0; i < vma_priv->n_pages; i++) {
			ret = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
					     vma_priv->pages[i]);
			if (ret)
				break;
		}

	if (ret)
		privcmd_buf_vmapriv_free(vma_priv);

	mutex_unlock(&file_priv->lock);

	return ret;
}

const struct file_operations xen_privcmdbuf_fops = {
	.owner = THIS_MODULE,
	.open = privcmd_buf_open,
	.release = privcmd_buf_release,
	.mmap = privcmd_buf_mmap,
};
EXPORT_SYMBOL_GPL(xen_privcmdbuf_fops);

struct miscdevice xen_privcmdbuf_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "xen/hypercall",
	.fops = &xen_privcmdbuf_fops,
};