[Xen-devel] [PATCH v9 3/4] libxc: Provide set_xen_guest_handle_offset macro

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Add set_xen_guest_handle_offset() macro that can be used for setting
xen_guest_handle to an offset into hypercall buffer.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v9:
* set_xen_guest_handle_offset() takes offset in terms of number of elements
* Drop unnecessary '#undef set_xen_guest_handle_offset'

 tools/libxc/include/xenctrl.h |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index a404855..4b3c26e 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -322,16 +322,24 @@ typedef struct xc_hypercall_buffer xc_hypercall_buffer_t;
  * Set a xen_guest_handle in a type safe manner, ensuring that the
  * data pointer has been correctly allocated.
  */
-#undef set_xen_guest_handle
-#define set_xen_guest_handle(_hnd, _val)                        \
+#define set_xen_guest_handle_impl(_hnd, _val, _byte_off)        \
     do {                                                        \
         xc_hypercall_buffer_t _hcbuf_hnd1;                      \
         typeof(XC__HYPERCALL_BUFFER_NAME(_val)) *_hcbuf_hnd2 =  \
                 HYPERCALL_BUFFER(_val);                         \
         (void) (&_hcbuf_hnd1 == _hcbuf_hnd2);                   \
-        set_xen_guest_handle_raw(_hnd, (_hcbuf_hnd2)->hbuf);    \
+        set_xen_guest_handle_raw(_hnd,                          \
+                (_hcbuf_hnd2)->hbuf + (_byte_off));             \
     } while (0)
 
+#undef set_xen_guest_handle
+#define set_xen_guest_handle(_hnd, _val)                        \
+    set_xen_guest_handle_impl(_hnd, _val, 0)
+
+#define set_xen_guest_handle_offset(_hnd, _val, _off)           \
+    set_xen_guest_handle_impl(_hnd, _val,                       \
+            ((sizeof(*_val)*(_off))))
+
 /* Use with set_xen_guest_handle in place of NULL */
 extern xc_hypercall_buffer_t XC__HYPERCALL_BUFFER_NAME(HYPERCALL_BUFFER_NULL);
 
-- 
1.7.1


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