Index: sys/arch/aarch64/aarch64/locore.S
===================================================================
RCS file: /cvsroot/src/sys/arch/aarch64/aarch64/locore.S,v
retrieving revision 1.42
diff -u -p -w -b -r1.42 locore.S
--- sys/arch/aarch64/aarch64/locore.S	19 Oct 2019 18:04:26 -0000	1.42
+++ sys/arch/aarch64/aarch64/locore.S	20 Oct 2019 12:01:40 -0000
@@ -378,10 +376,10 @@ ENTRY_NP(cpu_mpstart)
 
 	/* set stack pointer for boot */
 	mov	x1, #BOOT_AP_STACKSIZE
-	mul	x1, x1, x27
+	sub	x2, x27, #1
+	mul	x1, x1, x2
 	ADDR	x0, bootstk_cpus
-	sub	sp, x0, x1  /* sp = bootstk_cpus-(BOOT_AP_STACKSIZE*cpuindex) */
-
+	sub	sp, x0, x1  /* sp = bootstk_cpus - (BOOT_AP_STACKSIZE * (cpuindex - 1)) */
 
 	bl	1f
 1:	CPU_DPRINTREG("PC               = ", lr)
@@ -450,6 +447,8 @@ mp_vstart:
 	 * atomic_or_uint(&aarch64_cpu_mbox[cpuindex], 1)
 	 * to tell my activity to primary processor.
 	 */
+	ADDR	x0, _C_LABEL(aarch64_cpu_mbox)
+	add	x28, x0, x27, lsl #2	/* x28 = &aarch64_cpu_mbox[cpuindex] */
 	mov	x0, x28
 	mov	x1, #1
 	bl	_C_LABEL(atomic_or_uint)	/* hatched! */
@@ -459,8 +458,8 @@ mp_vstart:
 	/* wait for the mailbox start bit to become true */
 1:
 	dmb	sy
-	ldr	x20, [x28]
-	tst	x20, #2
+	ldr	w20, [x28]
+	tst	w20, #2
 	bne	9f
 	wfe
 	b	1b