[mirror_ubuntu-jammy-kernel.git] / drivers / xen / gntalloc.c

/******************************************************************************
 * gntalloc.c
 *
 * Device for creating grant references (in user-space) that may be shared
 * with other domains.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 * This driver exists to allow userspace programs in Linux to allocate kernel
 * memory that will later be shared with another domain.  Without this device,
 * Linux userspace programs cannot create grant references.
 *
 * How this stuff works:
 *   X -> granting a page to Y
 *   Y -> mapping the grant from X
 *
 *   1. X uses the gntalloc device to allocate a page of kernel memory, P.
 *   2. X creates an entry in the grant table that says domid(Y) can access P.
 *      This is done without a hypercall unless the grant table needs expansion.
 *   3. X gives the grant reference identifier, GREF, to Y.
 *   4. Y maps the page, either directly into kernel memory for use in a backend
 *      driver, or via a the gntdev device to map into the address space of an
 *      application running in Y. This is the first point at which Xen does any
 *      tracking of the page.
 *   5. A program in X mmap()s a segment of the gntalloc device that corresponds
 *      to the shared page, and can now communicate with Y over the shared page.
 *
 *
 * NOTE TO USERSPACE LIBRARIES:
 *   The grant allocation and mmap()ing are, naturally, two separate operations.
 *   You set up the sharing by calling the create ioctl() and then the mmap().
 *   Teardown requires munmap() and either close() or ioctl().
 *
 * WARNING: Since Xen does not allow a guest to forcibly end the use of a grant
 * reference, this device can be used to consume kernel memory by leaving grant
 * references mapped by another domain when an application exits. Therefore,
 * there is a global limit on the number of pages that can be allocated. When
 * all references to the page are unmapped, it will be freed during the next
 * grant operation.
 */

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

#include <linux/atomic.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/highmem.h>

#include <xen/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
#include <xen/gntalloc.h>
#include <xen/events.h>

static int limit = 1024;
module_param(limit, int, 0644);
MODULE_PARM_DESC(limit, "Maximum number of grants that may be allocated by "
		"the gntalloc device");

static LIST_HEAD(gref_list);
static DEFINE_MUTEX(gref_mutex);
static int gref_size;

struct notify_info {
	uint16_t pgoff:12;    /* Bits 0-11: Offset of the byte to clear */
	uint16_t flags:2;     /* Bits 12-13: Unmap notification flags */
	int event;            /* Port (event channel) to notify */
};

/* Metadata on a grant reference. */
struct gntalloc_gref {
	struct list_head next_gref;  /* list entry gref_list */
	struct list_head next_file;  /* list entry file->list, if open */
	struct page *page;	     /* The shared page */
	uint64_t file_index;         /* File offset for mmap() */
	unsigned int users;          /* Use count - when zero, waiting on Xen */
	grant_ref_t gref_id;         /* The grant reference number */
	struct notify_info notify;   /* Unmap notification */
};

struct gntalloc_file_private_data {
	struct list_head list;
	uint64_t index;
};

struct gntalloc_vma_private_data {
	struct gntalloc_gref *gref;
	int users;
	int count;
};

static void __del_gref(struct gntalloc_gref *gref);

static void do_cleanup(void)
{
	struct gntalloc_gref *gref, *n;
	list_for_each_entry_safe(gref, n, &gref_list, next_gref) {
		if (!gref->users)
			__del_gref(gref);
	}
}

static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
	uint32_t *gref_ids, struct gntalloc_file_private_data *priv)
{
	int i, rc, readonly;
	LIST_HEAD(queue_gref);
	LIST_HEAD(queue_file);
	struct gntalloc_gref *gref, *next;

	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
	for (i = 0; i < op->count; i++) {
		gref = kzalloc(sizeof(*gref), GFP_KERNEL);
		if (!gref) {
			rc = -ENOMEM;
			goto undo;
		}
		list_add_tail(&gref->next_gref, &queue_gref);
		list_add_tail(&gref->next_file, &queue_file);
		gref->users = 1;
		gref->file_index = op->index + i * PAGE_SIZE;
		gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
		if (!gref->page) {
			rc = -ENOMEM;
			goto undo;
		}

		/* Grant foreign access to the page. */
		rc = gnttab_grant_foreign_access(op->domid,
						 xen_page_to_gfn(gref->page),
						 readonly);
		if (rc < 0)
			goto undo;
		gref_ids[i] = gref->gref_id = rc;
	}

	/* Add to gref lists. */
	mutex_lock(&gref_mutex);
	list_splice_tail(&queue_gref, &gref_list);
	list_splice_tail(&queue_file, &priv->list);
	mutex_unlock(&gref_mutex);

	return 0;

undo:
	mutex_lock(&gref_mutex);
	gref_size -= (op->count - i);

	list_for_each_entry_safe(gref, next, &queue_file, next_file) {
		list_del(&gref->next_file);
		__del_gref(gref);
	}

	/* It's possible for the target domain to map the just-allocated grant
	 * references by blindly guessing their IDs; if this is done, then
	 * __del_gref will leave them in the queue_gref list. They need to be
	 * added to the global list so that we can free them when they are no
	 * longer referenced.
	 */
	if (unlikely(!list_empty(&queue_gref)))
		list_splice_tail(&queue_gref, &gref_list);
	mutex_unlock(&gref_mutex);
	return rc;
}

static void __del_gref(struct gntalloc_gref *gref)
{
	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
		uint8_t *tmp = kmap(gref->page);
		tmp[gref->notify.pgoff] = 0;
		kunmap(gref->page);
	}
	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
		notify_remote_via_evtchn(gref->notify.event);
		evtchn_put(gref->notify.event);
	}

	gref->notify.flags = 0;

	if (gref->gref_id) {
		if (gnttab_query_foreign_access(gref->gref_id))
			return;

		if (!gnttab_end_foreign_access_ref(gref->gref_id, 0))
			return;

		gnttab_free_grant_reference(gref->gref_id);
	}

	gref_size--;
	list_del(&gref->next_gref);

	if (gref->page)
		__free_page(gref->page);

	kfree(gref);
}

/* finds contiguous grant references in a file, returns the first */
static struct gntalloc_gref *find_grefs(struct gntalloc_file_private_data *priv,
		uint64_t index, uint32_t count)
{
	struct gntalloc_gref *rv = NULL, *gref;
	list_for_each_entry(gref, &priv->list, next_file) {
		if (gref->file_index == index && !rv)
			rv = gref;
		if (rv) {
			if (gref->file_index != index)
				return NULL;
			index += PAGE_SIZE;
			count--;
			if (count == 0)
				return rv;
		}
	}
	return NULL;
}

/*
 * -------------------------------------
 *  File operations.
 * -------------------------------------
 */
static int gntalloc_open(struct inode *inode, struct file *filp)
{
	struct gntalloc_file_private_data *priv;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
		goto out_nomem;
	INIT_LIST_HEAD(&priv->list);

	filp->private_data = priv;

	pr_debug("%s: priv %p\n", __func__, priv);

	return 0;

out_nomem:
	return -ENOMEM;
}

static int gntalloc_release(struct inode *inode, struct file *filp)
{
	struct gntalloc_file_private_data *priv = filp->private_data;
	struct gntalloc_gref *gref;

	pr_debug("%s: priv %p\n", __func__, priv);

	mutex_lock(&gref_mutex);
	while (!list_empty(&priv->list)) {
		gref = list_entry(priv->list.next,
			struct gntalloc_gref, next_file);
		list_del(&gref->next_file);
		gref->users--;
		if (gref->users == 0)
			__del_gref(gref);
	}
	kfree(priv);
	mutex_unlock(&gref_mutex);

	return 0;
}

static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
		struct ioctl_gntalloc_alloc_gref __user *arg)
{
	int rc = 0;
	struct ioctl_gntalloc_alloc_gref op;
	uint32_t *gref_ids;

	pr_debug("%s: priv %p\n", __func__, priv);

	if (copy_from_user(&op, arg, sizeof(op))) {
		rc = -EFAULT;
		goto out;
	}

	gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_KERNEL);
	if (!gref_ids) {
		rc = -ENOMEM;
		goto out;
	}

	mutex_lock(&gref_mutex);
	/* Clean up pages that were at zero (local) users but were still mapped
	 * by remote domains. Since those pages count towards the limit that we
	 * are about to enforce, removing them here is a good idea.
	 */
	do_cleanup();
	if (gref_size + op.count > limit) {
		mutex_unlock(&gref_mutex);
		rc = -ENOSPC;
		goto out_free;
	}
	gref_size += op.count;
	op.index = priv->index;
	priv->index += op.count * PAGE_SIZE;
	mutex_unlock(&gref_mutex);

	rc = add_grefs(&op, gref_ids, priv);
	if (rc < 0)
		goto out_free;

	/* Once we finish add_grefs, it is unsafe to touch the new reference,
	 * since it is possible for a concurrent ioctl to remove it (by guessing
	 * its index). If the userspace application doesn't provide valid memory
	 * to write the IDs to, then it will need to close the file in order to
	 * release - which it will do by segfaulting when it tries to access the
	 * IDs to close them.
	 */
	if (copy_to_user(arg, &op, sizeof(op))) {
		rc = -EFAULT;
		goto out_free;
	}
	if (copy_to_user(arg->gref_ids, gref_ids,
			sizeof(gref_ids[0]) * op.count)) {
		rc = -EFAULT;
		goto out_free;
	}

out_free:
	kfree(gref_ids);
out:
	return rc;
}

static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
		void __user *arg)
{
	int i, rc = 0;
	struct ioctl_gntalloc_dealloc_gref op;
	struct gntalloc_gref *gref, *n;

	pr_debug("%s: priv %p\n", __func__, priv);

	if (copy_from_user(&op, arg, sizeof(op))) {
		rc = -EFAULT;
		goto dealloc_grant_out;
	}

	mutex_lock(&gref_mutex);
	gref = find_grefs(priv, op.index, op.count);
	if (gref) {
		/* Remove from the file list only, and decrease reference count.
		 * The later call to do_cleanup() will remove from gref_list and
		 * free the memory if the pages aren't mapped anywhere.
		 */
		for (i = 0; i < op.count; i++) {
			n = list_entry(gref->next_file.next,
				struct gntalloc_gref, next_file);
			list_del(&gref->next_file);
			gref->users--;
			gref = n;
		}
	} else {
		rc = -EINVAL;
	}

	do_cleanup();

	mutex_unlock(&gref_mutex);
dealloc_grant_out:
	return rc;
}

static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
		void __user *arg)
{
	struct ioctl_gntalloc_unmap_notify op;
	struct gntalloc_gref *gref;
	uint64_t index;
	int pgoff;
	int rc;

	if (copy_from_user(&op, arg, sizeof(op)))
		return -EFAULT;

	index = op.index & ~(PAGE_SIZE - 1);
	pgoff = op.index & (PAGE_SIZE - 1);

	mutex_lock(&gref_mutex);

	gref = find_grefs(priv, index, 1);
	if (!gref) {
		rc = -ENOENT;
		goto unlock_out;
	}

	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT)) {
		rc = -EINVAL;
		goto unlock_out;
	}

	/* We need to grab a reference to the event channel we are going to use
	 * to send the notify before releasing the reference we may already have
	 * (if someone has called this ioctl twice). This is required so that
	 * it is possible to change the clear_byte part of the notification
	 * without disturbing the event channel part, which may now be the last
	 * reference to that event channel.
	 */
	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
		if (evtchn_get(op.event_channel_port)) {
			rc = -EINVAL;
			goto unlock_out;
		}
	}

	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
		evtchn_put(gref->notify.event);

	gref->notify.flags = op.action;
	gref->notify.pgoff = pgoff;
	gref->notify.event = op.event_channel_port;
	rc = 0;

 unlock_out:
	mutex_unlock(&gref_mutex);
	return rc;
}

static long gntalloc_ioctl(struct file *filp, unsigned int cmd,
		unsigned long arg)
{
	struct gntalloc_file_private_data *priv = filp->private_data;

	switch (cmd) {
	case IOCTL_GNTALLOC_ALLOC_GREF:
		return gntalloc_ioctl_alloc(priv, (void __user *)arg);

	case IOCTL_GNTALLOC_DEALLOC_GREF:
		return gntalloc_ioctl_dealloc(priv, (void __user *)arg);

	case IOCTL_GNTALLOC_SET_UNMAP_NOTIFY:
		return gntalloc_ioctl_unmap_notify(priv, (void __user *)arg);

	default:
		return -ENOIOCTLCMD;
	}

	return 0;
}

static void gntalloc_vma_open(struct vm_area_struct *vma)
{
	struct gntalloc_vma_private_data *priv = vma->vm_private_data;

	if (!priv)
		return;

	mutex_lock(&gref_mutex);
	priv->users++;
	mutex_unlock(&gref_mutex);
}

static void gntalloc_vma_close(struct vm_area_struct *vma)
{
	struct gntalloc_vma_private_data *priv = vma->vm_private_data;
	struct gntalloc_gref *gref, *next;
	int i;

	if (!priv)
		return;

	mutex_lock(&gref_mutex);
	priv->users--;
	if (priv->users == 0) {
		gref = priv->gref;
		for (i = 0; i < priv->count; i++) {
			gref->users--;
			next = list_entry(gref->next_gref.next,
					  struct gntalloc_gref, next_gref);
			if (gref->users == 0)
				__del_gref(gref);
			gref = next;
		}
		kfree(priv);
	}
	mutex_unlock(&gref_mutex);
}

static const struct vm_operations_struct gntalloc_vmops = {
	.open = gntalloc_vma_open,
	.close = gntalloc_vma_close,
};

static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)
{
	struct gntalloc_file_private_data *priv = filp->private_data;
	struct gntalloc_vma_private_data *vm_priv;
	struct gntalloc_gref *gref;
	int count = vma_pages(vma);
	int rv, i;

	if (!(vma->vm_flags & VM_SHARED)) {
		pr_err("%s: Mapping must be shared\n", __func__);
		return -EINVAL;
	}

	vm_priv = kmalloc(sizeof(*vm_priv), GFP_KERNEL);
	if (!vm_priv)
		return -ENOMEM;

	mutex_lock(&gref_mutex);

	pr_debug("%s: priv %p,%p, page %lu+%d\n", __func__,
		       priv, vm_priv, vma->vm_pgoff, count);

	gref = find_grefs(priv, vma->vm_pgoff << PAGE_SHIFT, count);
	if (gref == NULL) {
		rv = -ENOENT;
		pr_debug("%s: Could not find grant reference",
				__func__);
		kfree(vm_priv);
		goto out_unlock;
	}

	vm_priv->gref = gref;
	vm_priv->users = 1;
	vm_priv->count = count;

	vma->vm_private_data = vm_priv;

	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;

	vma->vm_ops = &gntalloc_vmops;

	for (i = 0; i < count; i++) {
		gref->users++;
		rv = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
				gref->page);
		if (rv)
			goto out_unlock;

		gref = list_entry(gref->next_file.next,
				struct gntalloc_gref, next_file);
	}
	rv = 0;

out_unlock:
	mutex_unlock(&gref_mutex);
	return rv;
}

static const struct file_operations gntalloc_fops = {
	.owner = THIS_MODULE,
	.open = gntalloc_open,
	.release = gntalloc_release,
	.unlocked_ioctl = gntalloc_ioctl,
	.mmap = gntalloc_mmap
};

/*
 * -------------------------------------
 * Module creation/destruction.
 * -------------------------------------
 */
static struct miscdevice gntalloc_miscdev = {
	.minor	= MISC_DYNAMIC_MINOR,
	.name	= "xen/gntalloc",
	.fops	= &gntalloc_fops,
};

static int __init gntalloc_init(void)
{
	int err;

	if (!xen_domain())
		return -ENODEV;

	err = misc_register(&gntalloc_miscdev);
	if (err != 0) {
		pr_err("Could not register misc gntalloc device\n");
		return err;
	}

	pr_debug("Created grant allocation device at %d,%d\n",
			MISC_MAJOR, gntalloc_miscdev.minor);

	return 0;
}

static void __exit gntalloc_exit(void)
{
	misc_deregister(&gntalloc_miscdev);
}

module_init(gntalloc_init);
module_exit(gntalloc_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Carter Weatherly <carter.weatherly@jhuapl.edu>, "
		"Daniel De Graaf <dgdegra@tycho.nsa.gov>");
MODULE_DESCRIPTION("User-space grant reference allocator driver");
Commit	Line	Data
dd314058 DDG	1	/******************************************************************************
	2	* gntalloc.c
	3	*
	4	* Device for creating grant references (in user-space) that may be shared
	5	* with other domains.
	6	*
	7	* This program is distributed in the hope that it will be useful,
	8	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	9	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	10	* GNU General Public License for more details.
	11	*
	12	* You should have received a copy of the GNU General Public License
	13	* along with this program; if not, write to the Free Software
	14	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	15	*/
	16
	17	/*
	18	* This driver exists to allow userspace programs in Linux to allocate kernel
	19	* memory that will later be shared with another domain. Without this device,
	20	* Linux userspace programs cannot create grant references.
	21	*
	22	* How this stuff works:
	23	* X -> granting a page to Y
	24	* Y -> mapping the grant from X
	25	*
	26	* 1. X uses the gntalloc device to allocate a page of kernel memory, P.
	27	* 2. X creates an entry in the grant table that says domid(Y) can access P.
	28	* This is done without a hypercall unless the grant table needs expansion.
	29	* 3. X gives the grant reference identifier, GREF, to Y.
	30	* 4. Y maps the page, either directly into kernel memory for use in a backend
	31	* driver, or via a the gntdev device to map into the address space of an
	32	* application running in Y. This is the first point at which Xen does any
	33	* tracking of the page.
	34	* 5. A program in X mmap()s a segment of the gntalloc device that corresponds
	35	* to the shared page, and can now communicate with Y over the shared page.
	36	*
	37	*
	38	* NOTE TO USERSPACE LIBRARIES:
	39	* The grant allocation and mmap()ing are, naturally, two separate operations.
	40	* You set up the sharing by calling the create ioctl() and then the mmap().
	41	* Teardown requires munmap() and either close() or ioctl().
	42	*
	43	* WARNING: Since Xen does not allow a guest to forcibly end the use of a grant
	44	* reference, this device can be used to consume kernel memory by leaving grant
	45	* references mapped by another domain when an application exits. Therefore,
	46	* there is a global limit on the number of pages that can be allocated. When
	47	* all references to the page are unmapped, it will be freed during the next
	48	* grant operation.
	49	*/
	50
283c0972 JP	51	#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
283c0972 JP	52
dd314058 DDG	53	#include <linux/atomic.h>
	54	#include <linux/module.h>
	55	#include <linux/miscdevice.h>
	56	#include <linux/kernel.h>
	57	#include <linux/init.h>
	58	#include <linux/slab.h>
	59	#include <linux/fs.h>
	60	#include <linux/device.h>
	61	#include <linux/mm.h>
	62	#include <linux/uaccess.h>
	63	#include <linux/types.h>
	64	#include <linux/list.h>
bdc612dc	65	#include <linux/highmem.h>
dd314058 DDG	66
	67	#include <xen/xen.h>
	68	#include <xen/page.h>
	69	#include <xen/grant_table.h>
	70	#include <xen/gntalloc.h>
bdc612dc	71	#include <xen/events.h>
dd314058 DDG	72
	73	static int limit = 1024;
	74	module_param(limit, int, 0644);
	75	MODULE_PARM_DESC(limit, "Maximum number of grants that may be allocated by "
	76	"the gntalloc device");
	77
	78	static LIST_HEAD(gref_list);
8ca19a89	79	static DEFINE_MUTEX(gref_mutex);
dd314058 DDG	80	static int gref_size;
dd314058 DDG	81
bdc612dc DDG	82	struct notify_info {
	83	uint16_t pgoff:12; /* Bits 0-11: Offset of the byte to clear */
	84	uint16_t flags:2; /* Bits 12-13: Unmap notification flags */
	85	int event; /* Port (event channel) to notify */
	86	};
	87
dd314058 DDG	88	/* Metadata on a grant reference. */
	89	struct gntalloc_gref {
	90	struct list_head next_gref; /* list entry gref_list */
	91	struct list_head next_file; /* list entry file->list, if open */
	92	struct page page; / The shared page */
	93	uint64_t file_index; /* File offset for mmap() */
	94	unsigned int users; /* Use count - when zero, waiting on Xen */
	95	grant_ref_t gref_id; /* The grant reference number */
bdc612dc	96	struct notify_info notify; /* Unmap notification */
dd314058 DDG	97	};
	98
	99	struct gntalloc_file_private_data {
	100	struct list_head list;
	101	uint64_t index;
	102	};
	103
243082e0 DDG	104	struct gntalloc_vma_private_data {
	105	struct gntalloc_gref *gref;
	106	int users;
	107	int count;
	108	};
	109
dd314058 DDG	110	static void __del_gref(struct gntalloc_gref *gref);
	111
	112	static void do_cleanup(void)
	113	{
	114	struct gntalloc_gref gref, n;
	115	list_for_each_entry_safe(gref, n, &gref_list, next_gref) {
	116	if (!gref->users)
	117	__del_gref(gref);
	118	}
	119	}
	120
	121	static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
	122	uint32_t gref_ids, struct gntalloc_file_private_data priv)
	123	{
	124	int i, rc, readonly;
	125	LIST_HEAD(queue_gref);
	126	LIST_HEAD(queue_file);
5903c6bd	127	struct gntalloc_gref gref, next;
dd314058 DDG	128
dd314058 DDG	129	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
dd314058 DDG	130	for (i = 0; i < op->count; i++) {
dd314058 DDG	131	gref = kzalloc(sizeof(*gref), GFP_KERNEL);
0fdb4744 PB	132	if (!gref) {
0fdb4744 PB	133	rc = -ENOMEM;
dd314058	134	goto undo;
0fdb4744	135	}
dd314058 DDG	136	list_add_tail(&gref->next_gref, &queue_gref);
	137	list_add_tail(&gref->next_file, &queue_file);
	138	gref->users = 1;
	139	gref->file_index = op->index + i * PAGE_SIZE;
	140	gref->page = alloc_page(GFP_KERNEL\|__GFP_ZERO);
0fdb4744 PB	141	if (!gref->page) {
0fdb4744 PB	142	rc = -ENOMEM;
dd314058	143	goto undo;
0fdb4744	144	}
dd314058 DDG	145
dd314058 DDG	146	/* Grant foreign access to the page. */
e9de2e5f	147	rc = gnttab_grant_foreign_access(op->domid,
0df4f266 JG	148	xen_page_to_gfn(gref->page),
0df4f266 JG	149	readonly);
e9de2e5f	150	if (rc < 0)
dd314058	151	goto undo;
e9de2e5f	152	gref_ids[i] = gref->gref_id = rc;
dd314058 DDG	153	}
	154
	155	/* Add to gref lists. */
8ca19a89	156	mutex_lock(&gref_mutex);
dd314058 DDG	157	list_splice_tail(&queue_gref, &gref_list);
dd314058 DDG	158	list_splice_tail(&queue_file, &priv->list);
8ca19a89	159	mutex_unlock(&gref_mutex);
dd314058 DDG	160
	161	return 0;
	162
	163	undo:
8ca19a89	164	mutex_lock(&gref_mutex);
dd314058 DDG	165	gref_size -= (op->count - i);
dd314058 DDG	166
5903c6bd DV	167	list_for_each_entry_safe(gref, next, &queue_file, next_file) {
5903c6bd DV	168	list_del(&gref->next_file);
dd314058 DDG	169	__del_gref(gref);
	170	}
	171
	172	/* It's possible for the target domain to map the just-allocated grant
	173	* references by blindly guessing their IDs; if this is done, then
	174	* __del_gref will leave them in the queue_gref list. They need to be
	175	* added to the global list so that we can free them when they are no
	176	* longer referenced.
	177	*/
	178	if (unlikely(!list_empty(&queue_gref)))
	179	list_splice_tail(&queue_gref, &gref_list);
8ca19a89	180	mutex_unlock(&gref_mutex);
dd314058 DDG	181	return rc;
	182	}
	183
	184	static void __del_gref(struct gntalloc_gref *gref)
	185	{
bdc612dc DDG	186	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
	187	uint8_t *tmp = kmap(gref->page);
	188	tmp[gref->notify.pgoff] = 0;
	189	kunmap(gref->page);
	190	}
0cc678f8	191	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
bdc612dc	192	notify_remote_via_evtchn(gref->notify.event);
0cc678f8 DDG	193	evtchn_put(gref->notify.event);
0cc678f8 DDG	194	}
bdc612dc DDG	195
	196	gref->notify.flags = 0;
	197
e9de2e5f	198	if (gref->gref_id) {
dd314058 DDG	199	if (gnttab_query_foreign_access(gref->gref_id))
	200	return;
	201
	202	if (!gnttab_end_foreign_access_ref(gref->gref_id, 0))
	203	return;
0105d2b4 DDG	204
0105d2b4 DDG	205	gnttab_free_grant_reference(gref->gref_id);
dd314058 DDG	206	}
	207
	208	gref_size--;
	209	list_del(&gref->next_gref);
	210
	211	if (gref->page)
	212	__free_page(gref->page);
	213
	214	kfree(gref);
	215	}
	216
	217	/* finds contiguous grant references in a file, returns the first */
	218	static struct gntalloc_gref find_grefs(struct gntalloc_file_private_data priv,
	219	uint64_t index, uint32_t count)
	220	{
	221	struct gntalloc_gref rv = NULL, gref;
	222	list_for_each_entry(gref, &priv->list, next_file) {
	223	if (gref->file_index == index && !rv)
	224	rv = gref;
	225	if (rv) {
	226	if (gref->file_index != index)
	227	return NULL;
	228	index += PAGE_SIZE;
	229	count--;
	230	if (count == 0)
	231	return rv;
	232	}
	233	}
	234	return NULL;
	235	}
	236
	237	/*
	238	* -------------------------------------
	239	* File operations.
	240	* -------------------------------------
	241	*/
	242	static int gntalloc_open(struct inode inode, struct file filp)
	243	{
	244	struct gntalloc_file_private_data *priv;
	245
	246	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	247	if (!priv)
	248	goto out_nomem;
	249	INIT_LIST_HEAD(&priv->list);
	250
	251	filp->private_data = priv;
	252
	253	pr_debug("%s: priv %p\n", __func__, priv);
	254
	255	return 0;
	256
	257	out_nomem:
	258	return -ENOMEM;
	259	}
	260
	261	static int gntalloc_release(struct inode inode, struct file filp)
	262	{
	263	struct gntalloc_file_private_data *priv = filp->private_data;
	264	struct gntalloc_gref *gref;
	265
	266	pr_debug("%s: priv %p\n", __func__, priv);
	267
8ca19a89	268	mutex_lock(&gref_mutex);
dd314058 DDG	269	while (!list_empty(&priv->list)) {
	270	gref = list_entry(priv->list.next,
	271	struct gntalloc_gref, next_file);
	272	list_del(&gref->next_file);
	273	gref->users--;
	274	if (gref->users == 0)
	275	__del_gref(gref);
	276	}
	277	kfree(priv);
8ca19a89	278	mutex_unlock(&gref_mutex);
dd314058 DDG	279
	280	return 0;
	281	}
	282
	283	static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
	284	struct ioctl_gntalloc_alloc_gref __user *arg)
	285	{
	286	int rc = 0;
	287	struct ioctl_gntalloc_alloc_gref op;
	288	uint32_t *gref_ids;
	289
	290	pr_debug("%s: priv %p\n", __func__, priv);
	291
	292	if (copy_from_user(&op, arg, sizeof(op))) {
	293	rc = -EFAULT;
	294	goto out;
	295	}
	296
0ee931c4	297	gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_KERNEL);
dd314058 DDG	298	if (!gref_ids) {
	299	rc = -ENOMEM;
	300	goto out;
	301	}
	302
8ca19a89	303	mutex_lock(&gref_mutex);
dd314058 DDG	304	/* Clean up pages that were at zero (local) users but were still mapped
	305	* by remote domains. Since those pages count towards the limit that we
	306	* are about to enforce, removing them here is a good idea.
	307	*/
	308	do_cleanup();
	309	if (gref_size + op.count > limit) {
8ca19a89	310	mutex_unlock(&gref_mutex);
dd314058 DDG	311	rc = -ENOSPC;
	312	goto out_free;
	313	}
	314	gref_size += op.count;
	315	op.index = priv->index;
	316	priv->index += op.count * PAGE_SIZE;
8ca19a89	317	mutex_unlock(&gref_mutex);
dd314058 DDG	318
	319	rc = add_grefs(&op, gref_ids, priv);
	320	if (rc < 0)
	321	goto out_free;
	322
	323	/* Once we finish add_grefs, it is unsafe to touch the new reference,
	324	* since it is possible for a concurrent ioctl to remove it (by guessing
	325	* its index). If the userspace application doesn't provide valid memory
	326	* to write the IDs to, then it will need to close the file in order to
	327	* release - which it will do by segfaulting when it tries to access the
	328	* IDs to close them.
	329	*/
	330	if (copy_to_user(arg, &op, sizeof(op))) {
	331	rc = -EFAULT;
	332	goto out_free;
	333	}
	334	if (copy_to_user(arg->gref_ids, gref_ids,
	335	sizeof(gref_ids[0]) * op.count)) {
	336	rc = -EFAULT;
	337	goto out_free;
	338	}
	339
	340	out_free:
	341	kfree(gref_ids);
	342	out:
	343	return rc;
	344	}
	345
	346	static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
	347	void __user *arg)
	348	{
	349	int i, rc = 0;
	350	struct ioctl_gntalloc_dealloc_gref op;
	351	struct gntalloc_gref gref, n;
	352
	353	pr_debug("%s: priv %p\n", __func__, priv);
	354
	355	if (copy_from_user(&op, arg, sizeof(op))) {
	356	rc = -EFAULT;
	357	goto dealloc_grant_out;
	358	}
	359
8ca19a89	360	mutex_lock(&gref_mutex);
dd314058 DDG	361	gref = find_grefs(priv, op.index, op.count);
	362	if (gref) {
	363	/* Remove from the file list only, and decrease reference count.
	364	* The later call to do_cleanup() will remove from gref_list and
	365	* free the memory if the pages aren't mapped anywhere.
	366	*/
	367	for (i = 0; i < op.count; i++) {
	368	n = list_entry(gref->next_file.next,
	369	struct gntalloc_gref, next_file);
	370	list_del(&gref->next_file);
	371	gref->users--;
	372	gref = n;
	373	}
	374	} else {
	375	rc = -EINVAL;
	376	}
	377
	378	do_cleanup();
	379
8ca19a89	380	mutex_unlock(&gref_mutex);
dd314058 DDG	381	dealloc_grant_out:
	382	return rc;
	383	}
	384
bdc612dc DDG	385	static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
	386	void __user *arg)
	387	{
	388	struct ioctl_gntalloc_unmap_notify op;
	389	struct gntalloc_gref *gref;
	390	uint64_t index;
	391	int pgoff;
	392	int rc;
	393
	394	if (copy_from_user(&op, arg, sizeof(op)))
	395	return -EFAULT;
	396
	397	index = op.index & ~(PAGE_SIZE - 1);
	398	pgoff = op.index & (PAGE_SIZE - 1);
	399
8ca19a89	400	mutex_lock(&gref_mutex);
bdc612dc DDG	401
	402	gref = find_grefs(priv, index, 1);
	403	if (!gref) {
	404	rc = -ENOENT;
	405	goto unlock_out;
	406	}
	407
	408	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE\|UNMAP_NOTIFY_SEND_EVENT)) {
	409	rc = -EINVAL;
	410	goto unlock_out;
	411	}
	412
0cc678f8 DDG	413	/* We need to grab a reference to the event channel we are going to use
	414	* to send the notify before releasing the reference we may already have
	415	* (if someone has called this ioctl twice). This is required so that
	416	* it is possible to change the clear_byte part of the notification
	417	* without disturbing the event channel part, which may now be the last
	418	* reference to that event channel.
	419	*/
	420	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
	421	if (evtchn_get(op.event_channel_port)) {
	422	rc = -EINVAL;
	423	goto unlock_out;
	424	}
	425	}
	426
	427	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
	428	evtchn_put(gref->notify.event);
	429
bdc612dc DDG	430	gref->notify.flags = op.action;
	431	gref->notify.pgoff = pgoff;
	432	gref->notify.event = op.event_channel_port;
	433	rc = 0;
8ca19a89	434
bdc612dc	435	unlock_out:
8ca19a89	436	mutex_unlock(&gref_mutex);
bdc612dc DDG	437	return rc;
	438	}
	439
dd314058 DDG	440	static long gntalloc_ioctl(struct file *filp, unsigned int cmd,
	441	unsigned long arg)
	442	{
	443	struct gntalloc_file_private_data *priv = filp->private_data;
	444
	445	switch (cmd) {
	446	case IOCTL_GNTALLOC_ALLOC_GREF:
	447	return gntalloc_ioctl_alloc(priv, (void __user *)arg);
	448
	449	case IOCTL_GNTALLOC_DEALLOC_GREF:
	450	return gntalloc_ioctl_dealloc(priv, (void __user *)arg);
	451
bdc612dc DDG	452	case IOCTL_GNTALLOC_SET_UNMAP_NOTIFY:
	453	return gntalloc_ioctl_unmap_notify(priv, (void __user *)arg);
	454
dd314058 DDG	455	default:
	456	return -ENOIOCTLCMD;
	457	}
	458
	459	return 0;
	460	}
	461
d79647ae DDG	462	static void gntalloc_vma_open(struct vm_area_struct *vma)
d79647ae DDG	463	{
243082e0 DDG	464	struct gntalloc_vma_private_data *priv = vma->vm_private_data;
	465
	466	if (!priv)
d79647ae DDG	467	return;
d79647ae DDG	468
8ca19a89	469	mutex_lock(&gref_mutex);
243082e0	470	priv->users++;
8ca19a89	471	mutex_unlock(&gref_mutex);
d79647ae DDG	472	}
d79647ae DDG	473
dd314058 DDG	474	static void gntalloc_vma_close(struct vm_area_struct *vma)
dd314058 DDG	475	{
243082e0 DDG	476	struct gntalloc_vma_private_data *priv = vma->vm_private_data;
	477	struct gntalloc_gref gref, next;
	478	int i;
	479
	480	if (!priv)
dd314058 DDG	481	return;
dd314058 DDG	482
8ca19a89	483	mutex_lock(&gref_mutex);
243082e0 DDG	484	priv->users--;
	485	if (priv->users == 0) {
	486	gref = priv->gref;
	487	for (i = 0; i < priv->count; i++) {
	488	gref->users--;
	489	next = list_entry(gref->next_gref.next,
	490	struct gntalloc_gref, next_gref);
	491	if (gref->users == 0)
	492	__del_gref(gref);
	493	gref = next;
	494	}
	495	kfree(priv);
	496	}
8ca19a89	497	mutex_unlock(&gref_mutex);
dd314058 DDG	498	}
dd314058 DDG	499
7cbea8dc	500	static const struct vm_operations_struct gntalloc_vmops = {
d79647ae	501	.open = gntalloc_vma_open,
dd314058 DDG	502	.close = gntalloc_vma_close,
	503	};
	504
	505	static int gntalloc_mmap(struct file filp, struct vm_area_struct vma)
	506	{
	507	struct gntalloc_file_private_data *priv = filp->private_data;
243082e0	508	struct gntalloc_vma_private_data *vm_priv;
dd314058	509	struct gntalloc_gref *gref;
c7ebf9d9	510	int count = vma_pages(vma);
dd314058 DDG	511	int rv, i;
dd314058 DDG	512
dd314058	513	if (!(vma->vm_flags & VM_SHARED)) {
283c0972	514	pr_err("%s: Mapping must be shared\n", __func__);
dd314058 DDG	515	return -EINVAL;
	516	}
	517
243082e0 DDG	518	vm_priv = kmalloc(sizeof(*vm_priv), GFP_KERNEL);
	519	if (!vm_priv)
	520	return -ENOMEM;
	521
8ca19a89	522	mutex_lock(&gref_mutex);
243082e0 DDG	523
	524	pr_debug("%s: priv %p,%p, page %lu+%d\n", __func__,
	525	priv, vm_priv, vma->vm_pgoff, count);
	526
dd314058 DDG	527	gref = find_grefs(priv, vma->vm_pgoff << PAGE_SHIFT, count);
	528	if (gref == NULL) {
	529	rv = -ENOENT;
	530	pr_debug("%s: Could not find grant reference",
	531	__func__);
2e163414	532	kfree(vm_priv);
dd314058 DDG	533	goto out_unlock;
	534	}
	535
243082e0 DDG	536	vm_priv->gref = gref;
	537	vm_priv->users = 1;
	538	vm_priv->count = count;
	539
	540	vma->vm_private_data = vm_priv;
dd314058	541
314e51b9	542	vma->vm_flags \|= VM_DONTEXPAND \| VM_DONTDUMP;
dd314058 DDG	543
	544	vma->vm_ops = &gntalloc_vmops;
	545
	546	for (i = 0; i < count; i++) {
	547	gref->users++;
	548	rv = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
	549	gref->page);
	550	if (rv)
	551	goto out_unlock;
	552
	553	gref = list_entry(gref->next_file.next,
	554	struct gntalloc_gref, next_file);
	555	}
	556	rv = 0;
	557
	558	out_unlock:
8ca19a89	559	mutex_unlock(&gref_mutex);
dd314058 DDG	560	return rv;
	561	}
	562
	563	static const struct file_operations gntalloc_fops = {
	564	.owner = THIS_MODULE,
	565	.open = gntalloc_open,
	566	.release = gntalloc_release,
	567	.unlocked_ioctl = gntalloc_ioctl,
	568	.mmap = gntalloc_mmap
	569	};
	570
	571	/*
	572	* -------------------------------------
	573	* Module creation/destruction.
	574	* -------------------------------------
	575	*/
	576	static struct miscdevice gntalloc_miscdev = {
	577	.minor = MISC_DYNAMIC_MINOR,
	578	.name = "xen/gntalloc",
	579	.fops = &gntalloc_fops,
	580	};
	581
	582	static int __init gntalloc_init(void)
	583	{
	584	int err;
	585
	586	if (!xen_domain())
	587	return -ENODEV;
	588
	589	err = misc_register(&gntalloc_miscdev);
	590	if (err != 0) {
283c0972	591	pr_err("Could not register misc gntalloc device\n");
dd314058 DDG	592	return err;
	593	}
	594
	595	pr_debug("Created grant allocation device at %d,%d\n",
	596	MISC_MAJOR, gntalloc_miscdev.minor);
	597
	598	return 0;
	599	}
	600
	601	static void __exit gntalloc_exit(void)
	602	{
	603	misc_deregister(&gntalloc_miscdev);
	604	}
	605
	606	module_init(gntalloc_init);
	607	module_exit(gntalloc_exit);
	608
	609	MODULE_LICENSE("GPL");
	610	MODULE_AUTHOR("Carter Weatherly <carter.weatherly@jhuapl.edu>, "
	611	"Daniel De Graaf <dgdegra@tycho.nsa.gov>");
	612	MODULE_DESCRIPTION("User-space grant reference allocator driver");