diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 2140d7a02845..1e28aa9bd12d 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -121,6 +121,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/ptrace.h>
 #include <machine/sigframe.h>
 
+/* Sanity check for __curthread() */
+CTASSERT(offsetof(struct pcpu, pc_curthread) == 0);
+
 extern u_int64_t hammer_time(u_int64_t, u_int64_t);
 extern void dblfault_handler(void);
 
diff --git a/sys/amd64/include/pcpu.h b/sys/amd64/include/pcpu.h
index 9e0383a8f0a7..b96221b473da 100644
--- a/sys/amd64/include/pcpu.h
+++ b/sys/amd64/include/pcpu.h
@@ -159,6 +159,16 @@ extern struct pcpu *pcpup;
 #define	PCPU_PTR(member)	__PCPU_PTR(pc_ ## member)
 #define	PCPU_SET(member, val)	__PCPU_SET(pc_ ## member, val)
 
+static __inline struct thread *
+__curthread(void)
+{
+	struct thread *td;
+
+	__asm __volatile("movq %%gs:0,%0" : "=r" (td));
+	return (td);
+}
+#define	Xurthread (__curthread())
+
 #else
 #error gcc or lint is required to use this file
 #endif