3 files changed, 22 insertions, 5 deletions

diff --git a/sys/dev/xen/console/xen_console.c b/sys/dev/xen/console/xen_console.c
index d232dd4e0c1c..f1a298a2aefa 100644
--- a/sys/dev/xen/console/xen_console.c
+++ b/sys/dev/xen/console/xen_console.c
@@ -138,6 +138,13 @@ struct putchar_arg {
 	size_t	n_next;
 };
 
+void __weak_symbol
+xen_emergency_print(const char *str, size_t size)
+{
+	KASSERT((xen_domain()), ("call to xc_printf from non Xen guest"));
+	HYPERVISOR_console_write(str, size);
+}
+
 static void
 putchar(int c, void *arg)
 {
@@ -150,12 +157,12 @@ putchar(int c, void *arg)
 		 * We have no buffer, output directly to the
 		 * console char by char.
 		 */
-		HYPERVISOR_console_write((char *)&c, 1);
+		xen_emergency_print((char *)&c, 1);
 	} else {
 		pca->buf[pca->n_next++] = c;
 		if ((pca->size == pca->n_next) || (c = '\0')) {
 			/* Flush the buffer */
-			HYPERVISOR_console_write(pca->buf, pca->n_next);
+			xen_emergency_print(pca->buf, pca->n_next);
 			pca->n_next = 0;
 		}
 	}
@@ -177,15 +184,13 @@ xc_printf(const char *fmt, ...)
 	pca.size = 0;
 #endif
 
-	KASSERT((xen_domain()), ("call to xc_printf from non Xen guest"));
-
 	va_start(ap, fmt);
 	kvprintf(fmt, putchar, &pca, 10, ap);
 	va_end(ap);
 
 #ifdef PRINTF_BUFR_SIZE
 	if (pca.n_next != 0)
-		HYPERVISOR_console_write(buf, pca.n_next);
+		xen_emergency_print(buf, pca.n_next);
 #endif
 }
 
diff --git a/sys/x86/xen/hvm.c b/sys/x86/xen/hvm.c
index b8125e230b6f..6411b790a2be 100644
--- a/sys/x86/xen/hvm.c
+++ b/sys/x86/xen/hvm.c
@@ -95,6 +95,11 @@ TUNABLE_INT("hw.xen.disable_pv_nics", &xen_disable_pv_nics);
 
 /*---------------------- XEN Hypervisor Probe and Setup ----------------------*/
 
+void xen_emergency_print(const char *str, size_t size)
+{
+	outsb(XEN_HVM_DEBUGCONS_IOPORT, str, size);
+}
+
 uint32_t xen_cpuid_base;
 
 static uint32_t
diff --git a/sys/xen/xen-os.h b/sys/xen/xen-os.h
index d7e9b3ca8632..98be41124846 100644
--- a/sys/xen/xen-os.h
+++ b/sys/xen/xen-os.h
@@ -151,6 +151,13 @@ int xenmem_free(device_t dev, int res_id, struct resource *res);
 /* Debug/emergency function, prints directly to hypervisor console */
 void xc_printf(const char *, ...) __printflike(1, 2);
 
+/*
+ * Emergency print function, can be defined per-arch, otherwise defaults to
+ * HYPERVISOR_console_write.  Should not be called directly, use xc_printf
+ * instead.
+ */
+void xen_emergency_print(const char *str, size_t size);
+
 #ifndef xen_mb
 #define xen_mb() mb()
 #endif