From 0dcd945a675cd12d283121e9b7f1626104b60bcc Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 4 Jun 2019 15:32:55 +0200 Subject: [PATCH] trace: fix build with gcc9 MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit While I've not observed this myself, gcc 9 (imo validly) reportedly may complain trace.c: In function '__trace_hypercall': trace.c:826:19: error: taking address of packed member of 'struct ' may result in an unaligned pointer value [-Werror=address-of-packed-member] 826 | uint32_t *a = d.args; and the fix is rather simple - remove the __packed attribute. Introduce a BUILD_BUG_ON() as replacement, for the unlikely case that Xen might get ported to an architecture where array alignment higher that that of its elements. Reported-by: Martin Liška Signed-off-by: Jan Beulich Acked-by: George Dunlap master commit: 3fd3b266d4198c06e8e421ca515d9ba09ccd5155 master date: 2019-05-13 09:51:23 +0200 --- xen/common/trace.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/xen/common/trace.c b/xen/common/trace.c index cc294fc384..d1ef81407b 100644 --- a/xen/common/trace.c +++ b/xen/common/trace.c @@ -819,12 +819,18 @@ unlock: void __trace_hypercall(uint32_t event, unsigned long op, const xen_ulong_t *args) { - struct __packed { + struct { uint32_t op; uint32_t args[6]; } d; uint32_t *a = d.args; + /* + * In lieu of using __packed above, which gcc9 legitimately doesn't + * like in combination with the address of d.args[] taken. + */ + BUILD_BUG_ON(offsetof(typeof(d), args) != sizeof(d.op)); + #define APPEND_ARG32(i) \ do { \ unsigned i_ = (i); \ -- 2.39.5