1 files changed, 210 insertions, 0 deletions
diff --git a/drivers/xen/privcmd-buf.c b/drivers/xen/privcmd-buf.c
new file mode 100644
index 0000000..df1ed37
--- /dev/null
+++ b/drivers/xen/privcmd-buf.c
@@ -0,0 +1,210 @@
+// 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");
+
+static unsigned int limit = 64;
+module_param(limit, uint, 0644);
+MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by "
+			"the privcmd-buf device per open file");
+
+struct privcmd_buf_private {
+	struct mutex lock;
+	struct list_head list;
+	unsigned int allocated;
+};
+
+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;
+
+	vma_priv->file_priv->allocated -= vma_priv->n_pages;
+
+	list_del(&vma_priv->list);
+
+	for (i = 0; i < vma_priv->n_pages; i++)
+		if (vma_priv->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) || count > limit ||
+	    file_priv->allocated + count > limit)
+		return -EINVAL;
+
+	vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *),
+			   GFP_KERNEL);
+	if (!vma_priv)
+		return -ENOMEM;
+
+	vma_priv->n_pages = count;
+	count = 0;
+	for (i = 0; i < vma_priv->n_pages; i++) {
+		vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!vma_priv->pages[i])
+			break;
+		count++;
+	}
+
+	mutex_lock(&file_priv->lock);
+
+	file_priv->allocated += count;
+
+	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,
+};