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![Suren Baghdasaryan](/assets/img/avatar_default.png)
Replace direct modifications to vma->vm_flags with calls to modifier functions to be able to track flag changes and to keep vma locking correctness. [akpm@linux-foundation.org: fix drivers/misc/open-dice.c, per Hyeonggon Yoo] Link: https://lkml.kernel.org/r/20230126193752.297968-5-surenb@google.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com> Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjun Roy <arjunroy@google.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: David Rientjes <rientjes@google.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Greg Thelen <gthelen@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Laurent Dufour <ldufour@linux.ibm.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Minchan Kim <minchan@google.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Peter Oskolkov <posk@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Punit Agrawal <punit.agrawal@bytedance.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Soheil Hassas Yeganeh <soheil@google.com> Cc: Song Liu <songliubraving@fb.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
598 lines
15 KiB
C
598 lines
15 KiB
C
/******************************************************************************
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* gntalloc.c
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*
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* Device for creating grant references (in user-space) that may be shared
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* with other domains.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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* This driver exists to allow userspace programs in Linux to allocate kernel
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* memory that will later be shared with another domain. Without this device,
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* Linux userspace programs cannot create grant references.
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*
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* How this stuff works:
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* X -> granting a page to Y
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* Y -> mapping the grant from X
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*
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* 1. X uses the gntalloc device to allocate a page of kernel memory, P.
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* 2. X creates an entry in the grant table that says domid(Y) can access P.
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* This is done without a hypercall unless the grant table needs expansion.
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* 3. X gives the grant reference identifier, GREF, to Y.
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* 4. Y maps the page, either directly into kernel memory for use in a backend
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* driver, or via a the gntdev device to map into the address space of an
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* application running in Y. This is the first point at which Xen does any
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* tracking of the page.
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* 5. A program in X mmap()s a segment of the gntalloc device that corresponds
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* to the shared page, and can now communicate with Y over the shared page.
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*
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*
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* NOTE TO USERSPACE LIBRARIES:
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* The grant allocation and mmap()ing are, naturally, two separate operations.
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* You set up the sharing by calling the create ioctl() and then the mmap().
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* Teardown requires munmap() and either close() or ioctl().
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*
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* WARNING: Since Xen does not allow a guest to forcibly end the use of a grant
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* reference, this device can be used to consume kernel memory by leaving grant
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* references mapped by another domain when an application exits. Therefore,
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* there is a global limit on the number of pages that can be allocated. When
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* all references to the page are unmapped, it will be freed during the next
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* grant operation.
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*/
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#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
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#include <linux/atomic.h>
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#include <linux/module.h>
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#include <linux/miscdevice.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/device.h>
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#include <linux/mm.h>
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#include <linux/uaccess.h>
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/highmem.h>
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#include <xen/xen.h>
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#include <xen/page.h>
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#include <xen/grant_table.h>
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#include <xen/gntalloc.h>
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#include <xen/events.h>
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static int limit = 1024;
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module_param(limit, int, 0644);
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MODULE_PARM_DESC(limit, "Maximum number of grants that may be allocated by "
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"the gntalloc device");
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static LIST_HEAD(gref_list);
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static DEFINE_MUTEX(gref_mutex);
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static int gref_size;
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struct notify_info {
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uint16_t pgoff:12; /* Bits 0-11: Offset of the byte to clear */
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uint16_t flags:2; /* Bits 12-13: Unmap notification flags */
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int event; /* Port (event channel) to notify */
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};
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/* Metadata on a grant reference. */
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struct gntalloc_gref {
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struct list_head next_gref; /* list entry gref_list */
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struct list_head next_file; /* list entry file->list, if open */
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struct page *page; /* The shared page */
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uint64_t file_index; /* File offset for mmap() */
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unsigned int users; /* Use count - when zero, waiting on Xen */
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grant_ref_t gref_id; /* The grant reference number */
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struct notify_info notify; /* Unmap notification */
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};
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struct gntalloc_file_private_data {
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struct list_head list;
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uint64_t index;
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};
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struct gntalloc_vma_private_data {
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struct gntalloc_gref *gref;
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int users;
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int count;
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};
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static void __del_gref(struct gntalloc_gref *gref);
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static void do_cleanup(void)
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{
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struct gntalloc_gref *gref, *n;
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list_for_each_entry_safe(gref, n, &gref_list, next_gref) {
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if (!gref->users)
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__del_gref(gref);
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}
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}
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static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
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uint32_t *gref_ids, struct gntalloc_file_private_data *priv)
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{
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int i, rc, readonly;
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LIST_HEAD(queue_gref);
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LIST_HEAD(queue_file);
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struct gntalloc_gref *gref, *next;
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readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
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for (i = 0; i < op->count; i++) {
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gref = kzalloc(sizeof(*gref), GFP_KERNEL);
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if (!gref) {
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rc = -ENOMEM;
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goto undo;
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}
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list_add_tail(&gref->next_gref, &queue_gref);
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list_add_tail(&gref->next_file, &queue_file);
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gref->users = 1;
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gref->file_index = op->index + i * PAGE_SIZE;
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gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
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if (!gref->page) {
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rc = -ENOMEM;
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goto undo;
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}
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/* Grant foreign access to the page. */
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rc = gnttab_grant_foreign_access(op->domid,
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xen_page_to_gfn(gref->page),
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readonly);
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if (rc < 0)
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goto undo;
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gref_ids[i] = gref->gref_id = rc;
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}
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/* Add to gref lists. */
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mutex_lock(&gref_mutex);
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list_splice_tail(&queue_gref, &gref_list);
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list_splice_tail(&queue_file, &priv->list);
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mutex_unlock(&gref_mutex);
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return 0;
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undo:
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mutex_lock(&gref_mutex);
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gref_size -= (op->count - i);
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list_for_each_entry_safe(gref, next, &queue_file, next_file) {
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list_del(&gref->next_file);
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__del_gref(gref);
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}
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mutex_unlock(&gref_mutex);
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return rc;
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}
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static void __del_gref(struct gntalloc_gref *gref)
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{
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if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
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uint8_t *tmp = kmap_local_page(gref->page);
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tmp[gref->notify.pgoff] = 0;
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kunmap_local(tmp);
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}
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if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
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notify_remote_via_evtchn(gref->notify.event);
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evtchn_put(gref->notify.event);
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}
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gref->notify.flags = 0;
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if (gref->gref_id) {
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if (gref->page)
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gnttab_end_foreign_access(gref->gref_id, gref->page);
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else
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gnttab_free_grant_reference(gref->gref_id);
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}
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gref_size--;
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list_del(&gref->next_gref);
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kfree(gref);
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}
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/* finds contiguous grant references in a file, returns the first */
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static struct gntalloc_gref *find_grefs(struct gntalloc_file_private_data *priv,
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uint64_t index, uint32_t count)
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{
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struct gntalloc_gref *rv = NULL, *gref;
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list_for_each_entry(gref, &priv->list, next_file) {
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if (gref->file_index == index && !rv)
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rv = gref;
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if (rv) {
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if (gref->file_index != index)
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return NULL;
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index += PAGE_SIZE;
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count--;
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if (count == 0)
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return rv;
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}
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}
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return NULL;
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}
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/*
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* -------------------------------------
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* File operations.
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* -------------------------------------
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*/
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static int gntalloc_open(struct inode *inode, struct file *filp)
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{
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struct gntalloc_file_private_data *priv;
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priv = kzalloc(sizeof(*priv), GFP_KERNEL);
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if (!priv)
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goto out_nomem;
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INIT_LIST_HEAD(&priv->list);
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filp->private_data = priv;
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pr_debug("%s: priv %p\n", __func__, priv);
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return 0;
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out_nomem:
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return -ENOMEM;
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}
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static int gntalloc_release(struct inode *inode, struct file *filp)
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{
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struct gntalloc_file_private_data *priv = filp->private_data;
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struct gntalloc_gref *gref;
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pr_debug("%s: priv %p\n", __func__, priv);
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mutex_lock(&gref_mutex);
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while (!list_empty(&priv->list)) {
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gref = list_entry(priv->list.next,
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struct gntalloc_gref, next_file);
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list_del(&gref->next_file);
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gref->users--;
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if (gref->users == 0)
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__del_gref(gref);
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}
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kfree(priv);
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mutex_unlock(&gref_mutex);
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return 0;
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}
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static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
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struct ioctl_gntalloc_alloc_gref __user *arg)
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{
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int rc = 0;
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struct ioctl_gntalloc_alloc_gref op;
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uint32_t *gref_ids;
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pr_debug("%s: priv %p\n", __func__, priv);
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if (copy_from_user(&op, arg, sizeof(op))) {
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rc = -EFAULT;
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goto out;
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}
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gref_ids = kcalloc(op.count, sizeof(gref_ids[0]), GFP_KERNEL);
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if (!gref_ids) {
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rc = -ENOMEM;
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goto out;
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}
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mutex_lock(&gref_mutex);
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/* Clean up pages that were at zero (local) users but were still mapped
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* by remote domains. Since those pages count towards the limit that we
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* are about to enforce, removing them here is a good idea.
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*/
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do_cleanup();
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if (gref_size + op.count > limit) {
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mutex_unlock(&gref_mutex);
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rc = -ENOSPC;
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goto out_free;
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}
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gref_size += op.count;
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op.index = priv->index;
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priv->index += op.count * PAGE_SIZE;
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mutex_unlock(&gref_mutex);
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rc = add_grefs(&op, gref_ids, priv);
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if (rc < 0)
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goto out_free;
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/* Once we finish add_grefs, it is unsafe to touch the new reference,
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* since it is possible for a concurrent ioctl to remove it (by guessing
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* its index). If the userspace application doesn't provide valid memory
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* to write the IDs to, then it will need to close the file in order to
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* release - which it will do by segfaulting when it tries to access the
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* IDs to close them.
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*/
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if (copy_to_user(arg, &op, sizeof(op))) {
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rc = -EFAULT;
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goto out_free;
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}
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if (copy_to_user(arg->gref_ids, gref_ids,
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sizeof(gref_ids[0]) * op.count)) {
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rc = -EFAULT;
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goto out_free;
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}
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out_free:
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kfree(gref_ids);
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out:
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return rc;
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}
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static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
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void __user *arg)
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{
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int i, rc = 0;
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struct ioctl_gntalloc_dealloc_gref op;
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struct gntalloc_gref *gref, *n;
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pr_debug("%s: priv %p\n", __func__, priv);
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if (copy_from_user(&op, arg, sizeof(op))) {
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rc = -EFAULT;
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goto dealloc_grant_out;
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}
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mutex_lock(&gref_mutex);
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gref = find_grefs(priv, op.index, op.count);
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if (gref) {
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/* Remove from the file list only, and decrease reference count.
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* The later call to do_cleanup() will remove from gref_list and
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* free the memory if the pages aren't mapped anywhere.
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*/
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for (i = 0; i < op.count; i++) {
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n = list_entry(gref->next_file.next,
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struct gntalloc_gref, next_file);
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list_del(&gref->next_file);
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gref->users--;
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gref = n;
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}
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} else {
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rc = -EINVAL;
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}
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do_cleanup();
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mutex_unlock(&gref_mutex);
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dealloc_grant_out:
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return rc;
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}
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static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
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void __user *arg)
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{
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struct ioctl_gntalloc_unmap_notify op;
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struct gntalloc_gref *gref;
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uint64_t index;
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int pgoff;
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int rc;
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if (copy_from_user(&op, arg, sizeof(op)))
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return -EFAULT;
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index = op.index & ~(PAGE_SIZE - 1);
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pgoff = op.index & (PAGE_SIZE - 1);
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mutex_lock(&gref_mutex);
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gref = find_grefs(priv, index, 1);
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if (!gref) {
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rc = -ENOENT;
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goto unlock_out;
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}
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if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT)) {
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rc = -EINVAL;
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goto unlock_out;
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}
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/* We need to grab a reference to the event channel we are going to use
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* to send the notify before releasing the reference we may already have
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* (if someone has called this ioctl twice). This is required so that
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* it is possible to change the clear_byte part of the notification
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* without disturbing the event channel part, which may now be the last
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* reference to that event channel.
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*/
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if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
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if (evtchn_get(op.event_channel_port)) {
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rc = -EINVAL;
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goto unlock_out;
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}
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}
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if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
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evtchn_put(gref->notify.event);
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gref->notify.flags = op.action;
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gref->notify.pgoff = pgoff;
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gref->notify.event = op.event_channel_port;
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rc = 0;
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unlock_out:
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mutex_unlock(&gref_mutex);
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return rc;
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}
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static long gntalloc_ioctl(struct file *filp, unsigned int cmd,
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unsigned long arg)
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{
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struct gntalloc_file_private_data *priv = filp->private_data;
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switch (cmd) {
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case IOCTL_GNTALLOC_ALLOC_GREF:
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return gntalloc_ioctl_alloc(priv, (void __user *)arg);
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case IOCTL_GNTALLOC_DEALLOC_GREF:
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return gntalloc_ioctl_dealloc(priv, (void __user *)arg);
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case IOCTL_GNTALLOC_SET_UNMAP_NOTIFY:
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return gntalloc_ioctl_unmap_notify(priv, (void __user *)arg);
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default:
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return -ENOIOCTLCMD;
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}
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return 0;
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}
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static void gntalloc_vma_open(struct vm_area_struct *vma)
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{
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struct gntalloc_vma_private_data *priv = vma->vm_private_data;
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if (!priv)
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return;
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mutex_lock(&gref_mutex);
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priv->users++;
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mutex_unlock(&gref_mutex);
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}
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static void gntalloc_vma_close(struct vm_area_struct *vma)
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{
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struct gntalloc_vma_private_data *priv = vma->vm_private_data;
|
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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;
|
|
|
|
vm_flags_set(vma, 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");
|