public/domctl: Fix the struct xen_domctl ABI in 32bit builds

The Xen domctl ABI currently relies on the union containing a field with
alignment of 8.

32bit projects which only copy the used subset of functionality end up with an
ABI breakage if they don't have at least one uint64_aligned_t field copied.

Insert explicit padding, and some build assertions to ensure it never changes
moving forwards.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Julien Grall <jgrall@amazon.com>

diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index a69b3b59a8cda0c5710d88307aa649cdd4f6dac3..20ef8399bd56ba5d1408d5491d75a15089c2a90a 100644 (file)
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -959,6 +959,14 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
     return ret;
 }
 
+static void __init __maybe_unused build_assertions(void)
+{
+    struct xen_domctl d;
+
+    BUILD_BUG_ON(sizeof(d) != 16 /* header */ + 128 /* union */);
+    BUILD_BUG_ON(offsetof(typeof(d), u) != 16);
+}
+
 /*
  * Local variables:
  * mode: C

diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 59bdc28c89381dca0b6af14b673261025ab58cf8..9464a9058a849b3a015935b80f1a2e2d7d632d54 100644 (file)
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1222,6 +1222,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_gdbsx_domstatus             1003
     uint32_t interface_version; /* XEN_DOMCTL_INTERFACE_VERSION */
     domid_t  domain;
+    uint16_t _pad[3];
     union {
         struct xen_domctl_createdomain      createdomain;
         struct xen_domctl_getdomaininfo     getdomaininfo;