Here my take at it. This actually also replaces the patch sent under the same subject yesterday, as I meanwhile realized there's a simpler way to achieve the desired effect. It also converts the 64-bit store to a 32-bit one, as only the upper 32 bits need clearing.

Signed-off-by: Jan Beulich <jbeu...@novell.com>

Index: 2006-08-28/xen/include/public/arch-x86_32.h =================================================================== --- 2006-08-28.orig/xen/include/public/arch-x86_32.h 2006-08-28
08:32:38.000000000 +0200 +++ 2006-08-28/xen/include/public/arch-x86_32.h 2006-08-29 11:15:44.000000000
+0200 @@ -29,11 +29,11 @@

/* Structural guest handles introduced in 0x00030201. */ #if (defined(__XEN__) || defined(__XEN_TOOLS__)) && !defined(__ASSEMBLY__) -typedef uint64_t __attribute__((aligned(8))) uint64_aligned_t; +#define uint64_aligned_t uint64_t __attribute__((__aligned__(8))) #define __DEFINE_XEN_GUEST_HANDLE(name, type) \ typedef struct { type *p; } \ __guest_handle_ ## name; \ - typedef struct { union { type *p; uint64_aligned_t q; }; } \ + typedef struct { type *p __attribute__((__aligned__(8))); } \ __guest_handle_64_ ## name #elif __XEN_INTERFACE_VERSION__ >= 0x00030201 #define __DEFINE_XEN_GUEST_HANDLE(name, type) \ @@ -49,7 +49,7 @@ typedef uint64_t __attribute__((aligned( #ifdef __XEN_TOOLS__ #define get_xen_guest_handle(val, hnd) do { val = (hnd).p; } while (0) #define set_xen_guest_handle(hnd, val) \ - do { if ( sizeof(hnd) == 8 ) *(uint64_t *)&(hnd) = 0; \ + do { if ( sizeof(hnd) == 8 ) (&(hnd).p)[1] = NULL; \ (hnd).p = val; \ } while ( 0 ) #else Index: 2006-08-28/xen/include/asm-x86/guest_access.h =================================================================== --- 2006-08-28.orig/xen/include/asm-x86/guest_access.h 2006-08-07
09:07:03.000000000 +0200 +++ 2006-08-28/xen/include/asm-x86/guest_access.h 2006-08-29 11:52:57.000000000
+0200 @@ -17,6 +17,14 @@ /* Offset the given guest handle into the array it refers to. */ #define guest_handle_add_offset(hnd, nr) ((hnd).p += (nr))

+#if defined(__i386__) +#define __guest_handle_okay(hnd) \ + (sizeof(hnd) == sizeof((hnd).p) || \ + (&(hnd).p)[1] == NULL) +#elif defined(__x86_64__) +#define __guest_handle_okay(hnd) ((void)(hnd), 1) +#endif + /* Cast a guest handle to the specified type of handle. */ #define guest_handle_cast(hnd, type) ({ \ type *_x = (hnd).p; \ @@ -33,9 +41,11 @@ #define copy_to_guest_offset(hnd, off, ptr, nr) ({ \ const typeof(ptr) _x = (hnd).p; \ const typeof(ptr) _y = (ptr); \ + __guest_handle_okay(hnd) ? \ hvm_guest(current) ? \ copy_to_user_hvm(_x+(off), _y, sizeof(*_x)*(nr)) : \ - copy_to_user(_x+(off), _y, sizeof(*_x)*(nr)); \ + copy_to_user(_x+(off), _y, sizeof(*_x)*(nr)) : \ + sizeof(*_x) * (nr); \ })

/* @@ -45,27 +55,33 @@ #define copy_from_guest_offset(ptr, hnd, off, nr) ({ \ const typeof(ptr) _x = (hnd).p; \ const typeof(ptr) _y = (ptr); \ + __guest_handle_okay(hnd) ? \ hvm_guest(current) ? \ copy_from_user_hvm(_y, _x+(off), sizeof(*_x)*(nr)) :\ - copy_from_user(_y, _x+(off), sizeof(*_x)*(nr)); \ + copy_from_user(_y, _x+(off), sizeof(*_x)*(nr)) : \ + sizeof(*_x) * (nr); \ })

/* Copy sub-field of a structure to guest context via a guest handle. */ #define copy_field_to_guest(hnd, ptr, field) ({ \ const typeof(&(ptr)->field) _x = &(hnd).p->field; \ const typeof(&(ptr)->field) _y = &(ptr)->field; \ + __guest_handle_okay(hnd) ? \ hvm_guest(current) ? \ copy_to_user_hvm(_x, _y, sizeof(*_x)) : \ - copy_to_user(_x, _y, sizeof(*_x)); \ + copy_to_user(_x, _y, sizeof(*_x)) : \ + sizeof(*_x); \ })

/* Copy sub-field of a structure from guest context via a guest handle. */ #define copy_field_from_guest(ptr, hnd, field) ({ \ const typeof(&(ptr)->field) _x = &(hnd).p->field; \ const typeof(&(ptr)->field) _y = &(ptr)->field; \ + __guest_handle_okay(hnd) ? \ hvm_guest(current) ? \ copy_from_user_hvm(_y, _x, sizeof(*_x)) : \ - copy_from_user(_y, _x, sizeof(*_x)); \ + copy_from_user(_y, _x, sizeof(*_x)) : \ + sizeof(*_x); \ })

/* @@ -73,7 +89,9 @@ * Allows use of faster __copy_* functions. */ #define guest_handle_okay(hnd, nr) \ - (hvm_guest(current) || array_access_ok((hnd).p, (nr), sizeof(*(hnd).p))) + (__guest_handle_okay(hnd) && \ + (hvm_guest(current) || \ + array_access_ok((hnd).p, (nr), sizeof(*(hnd).p))))

#define __copy_to_guest_offset(hnd, off, ptr, nr) ({ \ const typeof(ptr) _x = (hnd).p; \