xen: introduce XEN_GUEST_HANDLE_PARAM

XEN_GUEST_HANDLE_PARAM is going to be used to distinguish guest pointers
stored in memory from guest pointers as hypercall parameters.

guest_handle_* macros default to XEN_GUEST_HANDLE_PARAM as return type.
Two new guest_handle_to_param and guest_handle_from_param macros are
introduced to do conversions.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

5 files changed, 105 insertions, 13 deletions

diff --git a/xen/include/asm-arm/guest_access.h b/xen/include/asm-arm/guest_access.h
index 0fceae6a01..56862178e5 100644
--- a/xen/include/asm-arm/guest_access.h
+++ b/xen/include/asm-arm/guest_access.h
@@ -27,16 +27,40 @@ unsigned long raw_clear_guest(void *to, unsigned len);
 #define guest_handle_add_offset(hnd, nr) ((hnd).p += (nr))
 #define guest_handle_subtract_offset(hnd, nr) ((hnd).p -= (nr))
 
-/* Cast a guest handle to the specified type of handle. */
+/* Cast a guest handle (either XEN_GUEST_HANDLE or XEN_GUEST_HANDLE_PARAM)
+ * to the specified type of XEN_GUEST_HANDLE_PARAM. */
 #define guest_handle_cast(hnd, type) ({         \
     type *_x = (hnd).p;                         \
-    (XEN_GUEST_HANDLE(type)) { _x };            \
+    (XEN_GUEST_HANDLE_PARAM(type)) { _x };            \
+})
+
+/* 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)(&_x == &_y.p);                                    \
+    _y;                                                      \
+})
+
+
+/* Cast a XEN_GUEST_HANDLE_PARAM to XEN_GUEST_HANDLE */
+#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_from_ptr(ptr, type)        \
-    ((XEN_GUEST_HANDLE(type)) { (type *)ptr })
+    ((XEN_GUEST_HANDLE_PARAM(type)) { (type *)ptr })
 #define const_guest_handle_from_ptr(ptr, type)  \
-    ((XEN_GUEST_HANDLE(const_##type)) { (const type *)ptr })
+    ((XEN_GUEST_HANDLE_PARAM(const_##type)) { (const type *)ptr })
 
 /*
  * Copy an array of objects to guest context via a guest handle,
diff --git a/xen/include/asm-x86/guest_access.h b/xen/include/asm-x86/guest_access.h
index e3ac1d6fa8..ca700c959a 100644
--- a/xen/include/asm-x86/guest_access.h
+++ b/xen/include/asm-x86/guest_access.h
@@ -45,19 +45,40 @@
 #define guest_handle_add_offset(hnd, nr) ((hnd).p += (nr))
 #define guest_handle_subtract_offset(hnd, nr) ((hnd).p -= (nr))
 
-/* Cast a guest handle to the specified type of handle. */
+/* Cast a guest handle (either XEN_GUEST_HANDLE or XEN_GUEST_HANDLE_PARAM)
+ * to the specified type of XEN_GUEST_HANDLE_PARAM. */
 #define guest_handle_cast(hnd, type) ({         \
     type *_x = (hnd).p;                         \
-    (XEN_GUEST_HANDLE(type)) { _x };            \
+    (XEN_GUEST_HANDLE_PARAM(type)) { _x };            \
+})
+
+/* Cast a XEN_GUEST_HANDLE to XEN_GUEST_HANDLE_PARAM */
+#define guest_handle_to_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);                                                   \
+})
+
+/* 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_for_field(hnd, type, fld)          \
     ((XEN_GUEST_HANDLE(type)) { &(hnd).p->fld })
 
 #define guest_handle_from_ptr(ptr, type)        \
-    ((XEN_GUEST_HANDLE(type)) { (type *)ptr })
+    ((XEN_GUEST_HANDLE_PARAM(type)) { (type *)ptr })
 #define const_guest_handle_from_ptr(ptr, type)  \
-    ((XEN_GUEST_HANDLE(const_##type)) { (const type *)ptr })
+    ((XEN_GUEST_HANDLE_PARAM(const_##type)) { (const type *)ptr })
 
 /*
  * Copy an array of objects to guest context via a guest handle,
diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
index 2ae6548bb2..ac493a5481 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -51,18 +51,36 @@
 
 #define XEN_HYPERCALL_TAG   0XEA1
 
+#define uint64_aligned_t uint64_t __attribute__((aligned(8)))
 
 #ifndef __ASSEMBLY__
-#define ___DEFINE_XEN_GUEST_HANDLE(name, type) \
-    typedef struct { type *p; } __guest_handle_ ## name
+#define ___DEFINE_XEN_GUEST_HANDLE(name, type)                  \
+    typedef union { type *p; unsigned long q; }                 \
+        __guest_handle_ ## name;                                \
+    typedef union { type *p; uint64_aligned_t q; }              \
+        __guest_handle_64_ ## name;
 
+/*
+ * XEN_GUEST_HANDLE represents a guest pointer, when passed as a field
+ * in a struct in memory. On ARM is always 8 bytes sizes and 8 bytes
+ * aligned.
+ * XEN_GUEST_HANDLE_PARAM represent a guest pointer, when passed as an
+ * hypercall argument. It is 4 bytes on aarch and 8 bytes on aarch64.
+ */
 #define __DEFINE_XEN_GUEST_HANDLE(name, type) \
     ___DEFINE_XEN_GUEST_HANDLE(name, type);   \
     ___DEFINE_XEN_GUEST_HANDLE(const_##name, const type)
 #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)        __guest_handle_64_ ## name
 #define XEN_GUEST_HANDLE(name)          __XEN_GUEST_HANDLE(name)
-#define set_xen_guest_handle_raw(hnd, val)  do { (hnd).p = val; } while (0)
+/* this is going to be changed on 64 bit */
+#define XEN_GUEST_HANDLE_PARAM(name)   XEN_GUEST_HANDLE(name)
+#define set_xen_guest_handle_raw(hnd, val)                  \
+    do {                                                    \
+        typeof(&(hnd)) _sxghr_tmp = &(hnd);                 \
+        _sxghr_tmp->q = 0;                                  \
+        _sxghr_tmp->p = val;                                \
+    } while ( 0 )
 #ifdef __XEN_TOOLS__
 #define get_xen_guest_handle(val, hnd)  do { val = (hnd).p; } while (0)
 #endif
diff --git a/xen/include/public/arch-x86/xen.h b/xen/include/public/arch-x86/xen.h
index fff882425d..f5c58a6467 100644
--- a/xen/include/public/arch-x86/xen.h
+++ b/xen/include/public/arch-x86/xen.h
@@ -38,12 +38,21 @@
     typedef type * __guest_handle_ ## name
 #endif
 
+/*
+ * XEN_GUEST_HANDLE represents a guest pointer, when passed as a field
+ * in a struct in memory.
+ * XEN_GUEST_HANDLE_PARAM represent a guest pointer, when passed as an
+ * hypercall argument.
+ * XEN_GUEST_HANDLE_PARAM and XEN_GUEST_HANDLE are the same on X86 but
+ * they might not be on other architectures.
+ */
 #define __DEFINE_XEN_GUEST_HANDLE(name, type) \
     ___DEFINE_XEN_GUEST_HANDLE(name, type);   \
     ___DEFINE_XEN_GUEST_HANDLE(const_##name, const type)
 #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 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)
diff --git a/xen/include/xen/xencomm.h b/xen/include/xen/xencomm.h
index 730da7c1f2..3426b8a136 100644
--- a/xen/include/xen/xencomm.h
+++ b/xen/include/xen/xencomm.h
@@ -66,11 +66,31 @@ static inline unsigned long xencomm_inline_addr(const void *handle)
 /* Cast a guest handle to the specified type of handle. */
 #define guest_handle_cast(hnd, type) ({         \
     type *_x = (hnd).p;                         \
-    XEN_GUEST_HANDLE(type) _y;                  \
+    XEN_GUEST_HANDLE_PARAM(type) _y;            \
     set_xen_guest_handle(_y, _x);               \
     _y;                                         \
 })
 
+/* Cast a XEN_GUEST_HANDLE to XEN_GUEST_HANDLE_PARAM */
+#define guest_handle_to_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);                                                   \
+})
+
+/* 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);                                                   \
+})
+
 /* Since we run in real mode, we can safely access all addresses. That also
  * means our __routines are identical to our "normal" routines. */
 #define guest_handle_okay(hnd, nr) 1