initial commit

kernel/Start.S

@@ -0,0 +1,32 @@
+.section ".text.boot"
+
+.global _start
+
+_start:
+	// read cpu id, stop slave cores
+	mrs     x1, mpidr_el1
+	and     x1, x1, #3
+	cbz     x1, 2f
+	// cpu id > 0, stop
+1:  
+	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
+
+	// clear bss
+	ldr     x1, =__bss_start
+	ldr     w2, =__bss_size
+3:  
+	cbz     w2, 4f
+	str     xzr, [x1], #8
+	sub     w2, w2, #1
+	cbnz    w2, 3b
+
+4:
+	// jump to C code, should not return
+	bl      main
+	// for failsafe, halt this core too
+	b       1b