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@@ -0,0 +1,210 @@
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+// SPDX-License-Identifier: GPL-2.0 OR MIT
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+
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+/******************************************************************************
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+ * privcmd-buf.c
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+ *
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+ * Mmap of hypercall buffers.
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+ *
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+ * Copyright (c) 2018 Juergen Gross
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+ */
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+
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+#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
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+
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+#include <linux/kernel.h>
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+#include <linux/module.h>
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+#include <linux/list.h>
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+#include <linux/miscdevice.h>
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+#include <linux/mm.h>
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+#include <linux/slab.h>
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+
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+#include "privcmd.h"
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+
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+MODULE_LICENSE("GPL");
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+
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+static unsigned int limit = 64;
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+module_param(limit, uint, 0644);
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+MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by "
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+ "the privcmd-buf device per open file");
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+
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+struct privcmd_buf_private {
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+ struct mutex lock;
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+ struct list_head list;
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+ unsigned int allocated;
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+};
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+
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+struct privcmd_buf_vma_private {
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+ struct privcmd_buf_private *file_priv;
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+ struct list_head list;
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+ unsigned int users;
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+ unsigned int n_pages;
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+ struct page *pages[];
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+};
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+
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+static int privcmd_buf_open(struct inode *ino, struct file *file)
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+{
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+ struct privcmd_buf_private *file_priv;
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+
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+ file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL);
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+ if (!file_priv)
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+ return -ENOMEM;
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+
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+ mutex_init(&file_priv->lock);
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+ INIT_LIST_HEAD(&file_priv->list);
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+
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+ file->private_data = file_priv;
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+
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+ return 0;
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+}
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+
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+static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv)
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+{
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+ unsigned int i;
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+
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+ vma_priv->file_priv->allocated -= vma_priv->n_pages;
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+
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+ list_del(&vma_priv->list);
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+
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+ for (i = 0; i < vma_priv->n_pages; i++)
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+ if (vma_priv->pages[i])
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+ __free_page(vma_priv->pages[i]);
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+
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+ kfree(vma_priv);
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+}
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+
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+static int privcmd_buf_release(struct inode *ino, struct file *file)
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+{
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+ struct privcmd_buf_private *file_priv = file->private_data;
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+ struct privcmd_buf_vma_private *vma_priv;
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+
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+ mutex_lock(&file_priv->lock);
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+
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+ while (!list_empty(&file_priv->list)) {
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+ vma_priv = list_first_entry(&file_priv->list,
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+ struct privcmd_buf_vma_private,
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+ list);
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+ privcmd_buf_vmapriv_free(vma_priv);
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+ }
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+
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+ mutex_unlock(&file_priv->lock);
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+
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+ kfree(file_priv);
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+
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+ return 0;
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+}
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+
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+static void privcmd_buf_vma_open(struct vm_area_struct *vma)
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+{
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+ struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
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+
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+ if (!vma_priv)
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+ return;
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+
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+ mutex_lock(&vma_priv->file_priv->lock);
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+ vma_priv->users++;
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+ mutex_unlock(&vma_priv->file_priv->lock);
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+}
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+
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+static void privcmd_buf_vma_close(struct vm_area_struct *vma)
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+{
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+ struct privcmd_buf_vma_private *vma_priv = vma->vm_private_data;
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+ struct privcmd_buf_private *file_priv;
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+
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+ if (!vma_priv)
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+ return;
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+
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+ file_priv = vma_priv->file_priv;
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+
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+ mutex_lock(&file_priv->lock);
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+
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+ vma_priv->users--;
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+ if (!vma_priv->users)
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+ privcmd_buf_vmapriv_free(vma_priv);
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+
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+ mutex_unlock(&file_priv->lock);
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+}
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+
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+static vm_fault_t privcmd_buf_vma_fault(struct vm_fault *vmf)
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+{
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+ pr_debug("fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
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+ vmf->vma, vmf->vma->vm_start, vmf->vma->vm_end,
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+ vmf->pgoff, (void *)vmf->address);
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+
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+ return VM_FAULT_SIGBUS;
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+}
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+
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+static const struct vm_operations_struct privcmd_buf_vm_ops = {
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+ .open = privcmd_buf_vma_open,
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+ .close = privcmd_buf_vma_close,
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+ .fault = privcmd_buf_vma_fault,
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+};
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+
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+static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
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+{
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+ struct privcmd_buf_private *file_priv = file->private_data;
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+ struct privcmd_buf_vma_private *vma_priv;
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+ unsigned long count = vma_pages(vma);
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+ unsigned int i;
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+ int ret = 0;
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+
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+ if (!(vma->vm_flags & VM_SHARED) || count > limit ||
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+ file_priv->allocated + count > limit)
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+ return -EINVAL;
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+
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+ vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *),
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+ GFP_KERNEL);
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+ if (!vma_priv)
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+ return -ENOMEM;
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+
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+ vma_priv->n_pages = count;
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+ count = 0;
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+ for (i = 0; i < vma_priv->n_pages; i++) {
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+ vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
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+ if (!vma_priv->pages[i])
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+ break;
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+ count++;
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+ }
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+
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+ mutex_lock(&file_priv->lock);
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+
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+ file_priv->allocated += count;
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+
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+ vma_priv->file_priv = file_priv;
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+ vma_priv->users = 1;
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+
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+ vma->vm_flags |= VM_IO | VM_DONTEXPAND;
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+ vma->vm_ops = &privcmd_buf_vm_ops;
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+ vma->vm_private_data = vma_priv;
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+
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+ list_add(&vma_priv->list, &file_priv->list);
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+
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+ if (vma_priv->n_pages != count)
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+ ret = -ENOMEM;
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+ else
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+ for (i = 0; i < vma_priv->n_pages; i++) {
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+ ret = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
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+ vma_priv->pages[i]);
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+ if (ret)
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+ break;
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+ }
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+
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+ if (ret)
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+ privcmd_buf_vmapriv_free(vma_priv);
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+
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+ mutex_unlock(&file_priv->lock);
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+
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+ return ret;
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+}
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+
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+const struct file_operations xen_privcmdbuf_fops = {
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+ .owner = THIS_MODULE,
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+ .open = privcmd_buf_open,
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+ .release = privcmd_buf_release,
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+ .mmap = privcmd_buf_mmap,
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+};
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+EXPORT_SYMBOL_GPL(xen_privcmdbuf_fops);
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+
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+struct miscdevice xen_privcmdbuf_dev = {
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+ .minor = MISC_DYNAMIC_MINOR,
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+ .name = "xen/hypercall",
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+ .fops = &xen_privcmdbuf_fops,
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+};
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Linus Torvalds