1 // SPDX-License-Identifier: GPL-2.0 OR MIT
3 /******************************************************************************
6 * Mmap of hypercall buffers.
8 * Copyright (c) 2018 Juergen Gross
11 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/list.h>
16 #include <linux/miscdevice.h>
18 #include <linux/slab.h>
22 MODULE_LICENSE("GPL");
24 static unsigned int limit = 64;
25 module_param(limit, uint, 0644);
26 MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by "
27 "the privcmd-buf device per open file");
29 struct privcmd_buf_private {
31 struct list_head list;
32 unsigned int allocated;
35 struct privcmd_buf_vma_private {
36 struct privcmd_buf_private *file_priv;
37 struct list_head list;
43 static int privcmd_buf_open(struct inode *ino, struct file *file)
45 struct privcmd_buf_private *file_priv;
47 file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL);
51 mutex_init(&file_priv->lock);
52 INIT_LIST_HEAD(&file_priv->list);
54 file->private_data = file_priv;
59 static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv)
63 vma_priv->file_priv->allocated -= vma_priv->n_pages;
65 list_del(&vma_priv->list);
67 for (i = 0; i < vma_priv->n_pages; i++)
68 if (vma_priv->pages[i])
69 __free_page(vma_priv->pages[i]);
74 static int privcmd_buf_release(struct inode *ino, struct file *file)
76 struct privcmd_buf_private *file_priv = file->private_data;
77 struct privcmd_buf_vma_private *vma_priv;
79 mutex_lock(&file_priv->lock);
81 while (!list_empty(&file_priv->list)) {
82 vma_priv = list_first_entry(&file_priv->list,
83 struct privcmd_buf_vma_private,
85 privcmd_buf_vmapriv_free(vma_priv);
88 mutex_unlock(&file_priv->lock);
95 static void privcmd_buf_vma_open(struct vm_area_struct *vma)
97 struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
102 mutex_lock(&vma_priv->file_priv->lock);
104 mutex_unlock(&vma_priv->file_priv->lock);
107 static void privcmd_buf_vma_close(struct vm_area_struct *vma)
109 struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
110 struct privcmd_buf_private *file_priv;
115 file_priv = vma_priv->file_priv;
117 mutex_lock(&file_priv->lock);
120 if (!vma_priv->users)
121 privcmd_buf_vmapriv_free(vma_priv);
123 mutex_unlock(&file_priv->lock);
126 static vm_fault_t privcmd_buf_vma_fault(struct vm_fault *vmf)
128 pr_debug("fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
129 vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end,
130 vmf->pgoff, (void *)vmf->address);
132 return VM_FAULT_SIGBUS;
135 static const struct vm_operations_struct privcmd_buf_vm_ops = {
136 .open = privcmd_buf_vma_open,
137 .close = privcmd_buf_vma_close,
138 .fault = privcmd_buf_vma_fault,
141 static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
143 struct privcmd_buf_private *file_priv = file->private_data;
144 struct privcmd_buf_vma_private *vma_priv;
145 unsigned long count = vma_pages(vma);
149 if (!(vma->vm_flags & VM_SHARED) || count > limit ||
150 file_priv->allocated + count > limit)
153 vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *),
158 vma_priv->n_pages = count;
160 for (i = 0; i < vma_priv->n_pages; i++) {
161 vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
162 if (!vma_priv->pages[i])
167 mutex_lock(&file_priv->lock);
169 file_priv->allocated += count;
171 vma_priv->file_priv = file_priv;
174 vma->vm_flags |= VM_IO | VM_DONTEXPAND;
175 vma->vm_ops = &privcmd_buf_vm_ops;
176 vma->vm_private_data = vma_priv;
178 list_add(&vma_priv->list, &file_priv->list);
180 if (vma_priv->n_pages != count)
183 for (i = 0; i < vma_priv->n_pages; i++) {
184 ret = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
191 privcmd_buf_vmapriv_free(vma_priv);
193 mutex_unlock(&file_priv->lock);
198 const struct file_operations xen_privcmdbuf_fops = {
199 .owner = THIS_MODULE,
200 .open = privcmd_buf_open,
201 .release = privcmd_buf_release,
202 .mmap = privcmd_buf_mmap,
204 EXPORT_SYMBOL_GPL(xen_privcmdbuf_fops);
206 struct miscdevice xen_privcmdbuf_dev = {
207 .minor = MISC_DYNAMIC_MINOR,
208 .name = "xen/hypercall",
209 .fops = &xen_privcmdbuf_fops,