libxc: add xc_gntshr_* functions

These functions and the xc_gntshr device (/dev/xen/gntalloc on linux)
allow applications to create pages shared with other domains.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

6 files changed, 282 insertions, 0 deletions

diff --git a/tools/include/xen-sys/Linux/gntalloc.h b/tools/include/xen-sys/Linux/gntalloc.h
new file mode 100644
index 0000000000..76bd58065f
--- /dev/null
+++ b/tools/include/xen-sys/Linux/gntalloc.h
@@ -0,0 +1,82 @@
+/******************************************************************************
+ * gntalloc.h
+ *
+ * Interface to /dev/xen/gntalloc.
+ *
+ * Author: Daniel De Graaf <dgdegra@tycho.nsa.gov>
+ *
+ * This file is in the public domain.
+ */
+
+#ifndef __LINUX_PUBLIC_GNTALLOC_H__
+#define __LINUX_PUBLIC_GNTALLOC_H__
+
+/*
+ * Allocates a new page and creates a new grant reference.
+ */
+#define IOCTL_GNTALLOC_ALLOC_GREF \
+_IOC(_IOC_NONE, 'G', 5, sizeof(struct ioctl_gntalloc_alloc_gref))
+struct ioctl_gntalloc_alloc_gref {
+	/* IN parameters */
+	/* The ID of the domain to be given access to the grants. */
+	uint16_t domid;
+	/* Flags for this mapping */
+	uint16_t flags;
+	/* Number of pages to map */
+	uint32_t count;
+	/* OUT parameters */
+	/* The offset to be used on a subsequent call to mmap(). */
+	uint64_t index;
+	/* The grant references of the newly created grant, one per page */
+	/* Variable size, depending on count */
+	uint32_t gref_ids[1];
+};
+
+#define GNTALLOC_FLAG_WRITABLE 1
+
+/*
+ * Deallocates the grant reference, allowing the associated page to be freed if
+ * no other domains are using it.
+ */
+#define IOCTL_GNTALLOC_DEALLOC_GREF \
+_IOC(_IOC_NONE, 'G', 6, sizeof(struct ioctl_gntalloc_dealloc_gref))
+struct ioctl_gntalloc_dealloc_gref {
+	/* IN parameters */
+	/* The offset returned in the map operation */
+	uint64_t index;
+	/* Number of references to unmap */
+	uint32_t count;
+};
+
+/*
+ * Sets up an unmap notification within the page, so that the other side can do
+ * cleanup if this side crashes. Required to implement cross-domain robust
+ * mutexes or close notification on communication channels.
+ *
+ * Each mapped page only supports one notification; multiple calls referring to
+ * the same page overwrite the previous notification. You must clear the
+ * notification prior to the IOCTL_GNTALLOC_DEALLOC_GREF if you do not want it
+ * to occur.
+ */
+#define IOCTL_GNTALLOC_SET_UNMAP_NOTIFY \
+_IOC(_IOC_NONE, 'G', 7, sizeof(struct ioctl_gntalloc_unmap_notify))
+struct ioctl_gntalloc_unmap_notify {
+	/* IN parameters */
+	/* Offset in the file descriptor for a byte within the page (same as
+	 * used in mmap). If using UNMAP_NOTIFY_CLEAR_BYTE, this is the byte to
+	 * be cleared. Otherwise, it can be any byte in the page whose
+	 * notification we are adjusting.
+	 */
+	uint64_t index;
+	/* Action(s) to take on unmap */
+	uint32_t action;
+	/* Event channel to notify */
+	uint32_t event_channel_port;
+};
+
+/* Clear (set to zero) the byte specified by index */
+#define UNMAP_NOTIFY_CLEAR_BYTE 0x1
+/* Send an interrupt on the indicated event channel */
+#define UNMAP_NOTIFY_SEND_EVENT 0x2
+
+#endif /* __LINUX_PUBLIC_GNTALLOC_H__ */
diff --git a/tools/libxc/xc_gnttab.c b/tools/libxc/xc_gnttab.c
index 033cc5c0de..cb5995ffe4 100644
--- a/tools/libxc/xc_gnttab.c
+++ b/tools/libxc/xc_gnttab.c
@@ -203,6 +203,33 @@ int xc_gnttab_set_max_grants(xc_gnttab *xcg, uint32_t count)
 	return xcg->ops->u.gnttab.set_max_grants(xcg, xcg->ops_handle, count);
 }
 
+void *xc_gntshr_share_pages(xc_gntshr *xcg, uint32_t domid,
+                            int count, uint32_t *refs, int writable)
+{
+	return xcg->ops->u.gntshr.share_pages(xcg, xcg->ops_handle, domid,
+	                                      count, refs, writable, -1, -1);
+}
+
+void *xc_gntshr_share_page_notify(xc_gntshr *xcg, uint32_t domid,
+                                  uint32_t *ref, int writable,
+                                  uint32_t notify_offset,
+                                  evtchn_port_t notify_port)
+{
+	return xcg->ops->u.gntshr.share_pages(xcg, xcg->ops_handle,
+			domid, 1, ref, writable, notify_offset, notify_port);
+}
+
+/*
+ * Unmaps the @count pages starting at @start_address, which were mapped by a
+ * call to xc_gntshr_share_*. Never logs.
+ */
+int xc_gntshr_munmap(xc_gntshr *xcg, void *start_address, uint32_t count)
+{
+	return xcg->ops->u.gntshr.munmap(xcg, xcg->ops_handle,
+					 start_address, count);
+}
+
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
index f760421f9c..04059b8126 100644
--- a/tools/libxc/xc_linux_osdep.c
+++ b/tools/libxc/xc_linux_osdep.c
@@ -34,6 +34,7 @@
 #include <xen/memory.h>
 #include <xen/sys/evtchn.h>
 #include <xen/sys/gntdev.h>
+#include <xen/sys/gntalloc.h>
 
 #include "xenctrl.h"
 #include "xenctrlosdep.h"
@@ -656,6 +657,105 @@ static struct xc_osdep_ops linux_gnttab_ops = {
     },
 };
 
+static xc_osdep_handle linux_gntshr_open(xc_gntshr *xcg)
+{
+    int fd = open(DEVXEN "gntalloc", O_RDWR);
+
+    if ( fd == -1 )
+        return XC_OSDEP_OPEN_ERROR;
+
+    return (xc_osdep_handle)fd;
+}
+
+static int linux_gntshr_close(xc_gntshr *xcg, xc_osdep_handle h)
+{
+    int fd = (int)h;
+    return close(fd);
+}
+
+static void *linux_gntshr_share_pages(xc_gntshr *xch, xc_osdep_handle h,
+                                      uint32_t domid, int count,
+                                      uint32_t *refs, int writable,
+                                      uint32_t notify_offset,
+                                      evtchn_port_t notify_port)
+{
+    struct ioctl_gntalloc_alloc_gref *gref_info = NULL;
+    struct ioctl_gntalloc_unmap_notify notify;
+    struct ioctl_gntalloc_dealloc_gref gref_drop;
+    int fd = (int)h;
+    int err;
+    void *area = NULL;
+    gref_info = malloc(sizeof(*gref_info) + count * sizeof(uint32_t));
+    if (!gref_info)
+        return NULL;
+    gref_info->domid = domid;
+    gref_info->flags = writable ? GNTALLOC_FLAG_WRITABLE : 0;
+    gref_info->count = count;
+
+    err = ioctl(fd, IOCTL_GNTALLOC_ALLOC_GREF, gref_info);
+    if (err) {
+        PERROR("linux_gntshr_share_pages: ioctl failed");
+        goto out;
+    }
+
+    area = mmap(NULL, count * XC_PAGE_SIZE, PROT_READ | PROT_WRITE,
+        MAP_SHARED, fd, gref_info->index);
+
+    if (area == MAP_FAILED) {
+        area = NULL;
+        PERROR("linux_gntshr_share_pages: mmap failed");
+        goto out_remove_fdmap;
+    }
+
+    notify.index = gref_info->index;
+    notify.action = 0;
+    if (notify_offset >= 0) {
+        notify.index += notify_offset;
+        notify.action |= UNMAP_NOTIFY_CLEAR_BYTE;
+    }
+    if (notify_port >= 0) {
+        notify.event_channel_port = notify_port;
+        notify.action |= UNMAP_NOTIFY_SEND_EVENT;
+    }
+    if (notify.action)
+        err = ioctl(fd, IOCTL_GNTALLOC_SET_UNMAP_NOTIFY, &notify);
+    if (err) {
+        PERROR("linux_gntshr_share_page_notify: ioctl SET_UNMAP_NOTIFY failed");
+		munmap(area, count * XC_PAGE_SIZE);
+		area = NULL;
+	}
+
+    memcpy(refs, gref_info->gref_ids, count * sizeof(uint32_t));
+
+ out_remove_fdmap:
+    /* Removing the mapping from the file descriptor does not cause the pages to
+     * be deallocated until the mapping is removed.
+     */
+    gref_drop.index = gref_info->index;
+    gref_drop.count = count;
+    ioctl(fd, IOCTL_GNTALLOC_DEALLOC_GREF, &gref_drop);
+ out:
+    free(gref_info);
+    return area;
+}
+
+static int linux_gntshr_munmap(xc_gntshr *xcg, xc_osdep_handle h,
+                               void *start_address, uint32_t count)
+{
+    return munmap(start_address, count);
+}
+
+static struct xc_osdep_ops linux_gntshr_ops = {
+    .open = &linux_gntshr_open,
+    .close = &linux_gntshr_close,
+
+    .u.gntshr = {
+        .share_pages = &linux_gntshr_share_pages,
+        .munmap = &linux_gntshr_munmap,
+    },
+};
+
+
 static struct xc_osdep_ops *linux_osdep_init(xc_interface *xch, enum xc_osdep_type type)
 {
     switch ( type )
@@ -666,6 +766,8 @@ static struct xc_osdep_ops *linux_osdep_init(xc_interface *xch, enum xc_osdep_ty
         return &linux_evtchn_ops;
     case XC_OSDEP_GNTTAB:
         return &linux_gnttab_ops;
+    case XC_OSDEP_GNTSHR:
+        return &linux_gntshr_ops;
     default:
         return NULL;
     }
diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c
index 09c8f23ca5..09a91e75ad 100644
--- a/tools/libxc/xc_private.c
+++ b/tools/libxc/xc_private.c
@@ -258,6 +258,19 @@ int xc_gnttab_close(xc_gnttab *xcg)
     return xc_interface_close_common(xcg);
 }
 
+xc_gntshr *xc_gntshr_open(xentoollog_logger *logger,
+                             unsigned open_flags)
+{
+    return xc_interface_open_common(logger, NULL, open_flags,
+                                    XC_OSDEP_GNTSHR);
+}
+
+int xc_gntshr_close(xc_gntshr *xcg)
+{
+    return xc_interface_close_common(xcg);
+}
+
+
 static pthread_key_t errbuf_pkey;
 static pthread_once_t errbuf_pkey_once = PTHREAD_ONCE_INIT;
 
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 0e3c25edf1..3ff943ff32 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -115,6 +115,7 @@
 typedef struct xc_interface_core xc_interface;
 typedef struct xc_interface_core xc_evtchn;
 typedef struct xc_interface_core xc_gnttab;
+typedef struct xc_interface_core xc_gntshr;
 typedef enum xc_error_code xc_error_code;
 
 
@@ -1403,6 +1404,53 @@ grant_entry_v1_t *xc_gnttab_map_table_v1(xc_interface *xch, int domid, int *gnt_
 grant_entry_v2_t *xc_gnttab_map_table_v2(xc_interface *xch, int domid, int *gnt_num);
 /* Sometimes these don't set errno [fixme], and sometimes they don't log. */
 
+/*
+ * Return an fd onto the grant sharing driver.  Logs errors.
+ */
+xc_gntshr *xc_gntshr_open(xentoollog_logger *logger,
+			  unsigned open_flags);
+
+/*
+ * Close a handle previously allocated with xc_gntshr_open().
+ * Never logs errors.
+ */
+int xc_gntshr_close(xc_gntshr *xcg);
+
+/*
+ * Creates and shares pages with another domain.
+ * 
+ * @parm xcg a handle to an open grant sharing instance
+ * @parm domid the domain to share memory with
+ * @parm count the number of pages to share
+ * @parm refs the grant references of the pages (output)
+ * @parm writable true if the other domain can write to the pages
+ * @return local mapping of the pages
+ */
+void *xc_gntshr_share_pages(xc_gntshr *xcg, uint32_t domid,
+                            int count, uint32_t *refs, int writable);
+
+/*
+ * Creates and shares a page with another domain, with unmap notification.
+ * 
+ * @parm xcg a handle to an open grant sharing instance
+ * @parm domid the domain to share memory with
+ * @parm refs the grant reference of the pages (output)
+ * @parm writable true if the other domain can write to the page
+ * @parm notify_offset The byte offset in the page to use for unmap
+ *                     notification; -1 for none.
+ * @parm notify_port The event channel port to use for unmap notify, or -1
+ * @return local mapping of the page
+ */
+void *xc_gntshr_share_page_notify(xc_gntshr *xcg, uint32_t domid,
+                                  uint32_t *ref, int writable,
+                                  uint32_t notify_offset,
+                                  evtchn_port_t notify_port);
+/*
+ * Unmaps the @count pages starting at @start_address, which were mapped by a
+ * call to xc_gntshr_share_*. Never logs.
+ */
+int xc_gntshr_munmap(xc_gntshr *xcg, void *start_address, uint32_t count);
+
 int xc_physdev_map_pirq(xc_interface *xch,
                         int domid,
                         int index,
diff --git a/tools/libxc/xenctrlosdep.h b/tools/libxc/xenctrlosdep.h
index 1c6317e52e..a36c4aab7b 100644
--- a/tools/libxc/xenctrlosdep.h
+++ b/tools/libxc/xenctrlosdep.h
@@ -54,6 +54,7 @@ enum xc_osdep_type {
     XC_OSDEP_PRIVCMD,
     XC_OSDEP_EVTCHN,
     XC_OSDEP_GNTTAB,
+    XC_OSDEP_GNTSHR,
 };
 
 /* Opaque handle internal to the backend */
@@ -116,6 +117,15 @@ struct xc_osdep_ops
                           uint32_t count);
             int (*set_max_grants)(xc_gnttab *xcg, xc_osdep_handle h, uint32_t count);
         } gnttab;
+        struct {
+            void *(*share_pages)(xc_gntshr *xcg, xc_osdep_handle h,
+                                 uint32_t domid, int count,
+                                 uint32_t *refs, int writable,
+                                 uint32_t notify_offset,
+                                 evtchn_port_t notify_port);
+            int (*munmap)(xc_gntshr *xcg, xc_osdep_handle h,
+                          void *start_address, uint32_t count);
+        } gntshr;
     } u;
 };
 typedef struct xc_osdep_ops xc_osdep_ops;