hw2 done

kernel/Start.S

@@ -4,25 +4,24 @@
 
 _start:
 	// read cpu id, stop slave cores
-	mrs     x1, mpidr_el1
-	and     x1, x1, #3
-	cbz     x1, 2f
+	mrs x1, mpidr_el1
+	and x1, x1, #3
+	cbz x1, run
 	// cpu id > 0, stop
-1:  
+wait:
 	wfe
-	b       1b
-2:// cpu id == 0
-	// set top of stack just before our code (stack grows to a lower address per AAPCS64)
-	ldr     x1, =_start
-	mov     sp, x1
+	b wait
+
+run: // cpu id == 0
+  mov x20, x0
+	adrp x0, __stack_end
+	mov sp, x0
 
 	// clear bss
 	adr x0, __bss_start
 	adr x1, __bss_end
 	bl memzero
 
-4:
-	// jump to C code, should not return
-	bl      main
-	// for failsafe, halt this core too
-	b       1b
+	mov x0, x20
+	bl main
+	b wait