Index: lib/libc/aarch64/Symbol.map
===================================================================
--- lib/libc/aarch64/Symbol.map
+++ lib/libc/aarch64/Symbol.map
@@ -11,6 +11,7 @@
 	/* PSEUDO syscalls */
 	_exit;
 
+	.mcount;
 	_setjmp;
 	_longjmp;
 	fabs;
Index: sys/arm64/include/profile.h
===================================================================
--- sys/arm64/include/profile.h
+++ sys/arm64/include/profile.h
@@ -44,8 +44,29 @@
 
 typedef __uintfptr_t    uintfptr_t;
 
-#define	_MCOUNT_DECL	void mcount
+#define	_MCOUNT_DECL \
+static void _mcount(uintfptr_t frompc, uintfptr_t selfpc) __used; \
+static void _mcount
+
+#ifdef __GNUCLIKE_ASM
+#define	MCOUNT __asm(					\
+"	.text					\n"	\
+"	.align	6				\n"	\
+"	.type	.mcount,#function		\n"	\
+"	.globl	.mcount				\n"	\
+"	.mcount:				\n"	\
+"	.cfi_startproc				\n"	\
+	/* Load the caller return address as frompc */	\
+"	ldr	x0, [x29, #8]			\n"	\
+	/* Use our return address as selfpc */		\
+"	mov	x1, lr				\n"	\
+"	b	_mcount				\n"	\
+"	.cfi_endproc				\n"	\
+"	.size	.mcount, . - .mcount		\n"	\
+	);
+#else
 #define	MCOUNT
+#endif
 
 #endif /* !_KERNEL */