Index: mod/kcore/syscall.fn.x86.lin.64.s
==================================================================
--- mod/kcore/syscall.fn.x86.lin.64.s
+++ mod/kcore/syscall.fn.x86.lin.64.s
@@ -34,16 +34,17 @@
 	; arg 1 = errno ptr
 	; arg 2 = syscall num
 	; arg 3 = valency
 	; arg 4 = args ptr
 
-	; we use two registers that are supposed
+	; we use three registers that are supposed
 	; to be callee-saved, so we need to
 	; push them to the stack and then pop
 	; them back off just before the fn rets.
 	push rbx
 	push r12
+	push r15
 
 	; store the locals in registers that
 	; are guaranteed not to be clobbered,
 	; saving us some cycles pushing to
 	; and popping back from the stack
@@ -101,8 +102,9 @@
 	.error: neg sys.reg.ret
 	        mov qword [rbx], -1
 			mov       [r12], sys.reg.ret
 			jmp .return
 
-	.return: pop r12
+	.return: pop r15 
+		 pop r12
 	         pop rbx
 			 ret