Re: [Xen-devel] [PATCH v3 0/6] ARM hypercall ABI: 64 bit ready

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-08-16 at 15:48 +0100, Stefano Stabellini wrote:
> In this version of the patch series I have introduced conversion macros
> to convert a XEN_GUEST_HANDLE_PARAM into a XEN_GUEST_HANDLE a vice
> versa. Most of the problematic cases come from xen/arch/x86 code, in
> order to spot them I wrote a simple debug patch that change the
> definition of XEN_GUEST_HANDLE_PARAM to be different from
> XEN_GUEST_HANDLE on x86 too. I am attaching the debug patch to this
> email. 

This (quoted below) seems like a useful patch from the PoV of catching
these sorts of things early on x86 before they break ARM.

It doesn't seem like it should have any impact on the generated code,
should we perhaps apply it?

I needed the addition of the following to actually make it work though.

diff --git a/xen/include/asm-x86/guest_access.h b/xen/include/asm-x86/guest_acce
index ca700c9..33b4afd 100644
--- a/xen/include/asm-x86/guest_access.h
+++ b/xen/include/asm-x86/guest_access.h
@@ -54,22 +54,24 @@
 
 /* Cast a XEN_GUEST_HANDLE to XEN_GUEST_HANDLE_PARAM */
 #define guest_handle_to_param(hnd, type) ({                  \
+    typeof((hnd).p) _x = (hnd).p;                            \
+    XEN_GUEST_HANDLE_PARAM(type) _y = { _x };                \
     /* type checking: make sure that the pointers inside     \
      * XEN_GUEST_HANDLE and XEN_GUEST_HANDLE_PARAM are of    \
      * the same type, then return hnd */                     \
-    (void)((typeof(&(hnd).p)) 0 ==                           \
-        (typeof(&((XEN_GUEST_HANDLE_PARAM(type)) {}).p)) 0); \
-    (hnd);                                                   \
+    (void)(&_x == &_y.p);                                    \
+    _y;                                                      \
 })
 
 /* Cast a XEN_GUEST_HANDLE_PARAM to XEN_GUEST_HANDLE */
-#define guest_handle_from_param(hnd, type) ({                \
-    /* type checking: make sure that the pointers inside     \
-     * XEN_GUEST_HANDLE and XEN_GUEST_HANDLE_PARAM are of    \
-     * the same type, then return hnd */                     \
-    (void)((typeof(&(hnd).p)) 0 ==                           \
-        (typeof(&((XEN_GUEST_HANDLE_PARAM(type)) {}).p)) 0); \
-    (hnd);                                                   \
+#define guest_handle_from_param(hnd, type) ({               \
+    typeof((hnd).p) _x = (hnd).p;                           \
+    XEN_GUEST_HANDLE(type) _y = { _x };                     \
+    /* type checking: make sure that the pointers inside    \
+     * XEN_GUEST_HANDLE and XEN_GUEST_HANDLE_PARAM are of   \
+     * the same type, then return hnd */                    \
+    (void)(&_x == &_y.p);                                   \
+    _y;                                                     \
 })
 
 #define guest_handle_for_field(hnd, type, fld)          \


> diff --git a/xen/include/public/arch-x86/xen.h 
> b/xen/include/public/arch-x86/xen.h
> index 0e10260..08a788e 100644
> --- a/xen/include/public/arch-x86/xen.h
> +++ b/xen/include/public/arch-x86/xen.h
> @@ -32,7 +32,8 @@
>  /* Structural guest handles introduced in 0x00030201. */
>  #if __XEN_INTERFACE_VERSION__ >= 0x00030201
>  #define ___DEFINE_XEN_GUEST_HANDLE(name, type) \
> -    typedef struct { type *p; } __guest_handle_ ## name
> +    typedef struct { type *p; } __guest_handle_ ## name; \
> +    typedef struct { type *p; } __guest_handle_param_ ## name
>  #else
>  #define ___DEFINE_XEN_GUEST_HANDLE(name, type) \
>      typedef type * __guest_handle_ ## name
> @@ -52,7 +53,7 @@
>  #define DEFINE_XEN_GUEST_HANDLE(name)   __DEFINE_XEN_GUEST_HANDLE(name, name)
>  #define __XEN_GUEST_HANDLE(name)        __guest_handle_ ## name
>  #define XEN_GUEST_HANDLE(name)          __XEN_GUEST_HANDLE(name)
> -#define XEN_GUEST_HANDLE_PARAM(name)    XEN_GUEST_HANDLE(name)
> +#define XEN_GUEST_HANDLE_PARAM(name)    __guest_handle_param_ ## name
>  #define set_xen_guest_handle_raw(hnd, val)  do { (hnd).p = val; } while (0)
>  #ifdef __XEN_TOOLS__
>  #define get_xen_guest_handle(val, hnd)  do { val = (hnd).p; } while (0)
> 


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